Automotive Steel Technology
Each automobile component is designed to unique conditions and criteria such as durability, crash energy management, appearance, formability, cost. Steel has the best combination of engineering capability versus material cost. Steel is formable, weldable, strong and has state-of-the-art coating that will help resist corrosion. In addition, it is cost effective and has good surface appearance. We have gathered and organized information along with a comparison chart of mechanical properties pertaining to every steel available for use in automotive applications today. We have also created a list of our publications should there be a specific topic you would like to research.
Grades and Products
Low-Carbon Steels
Commercial Steel (CS) Type B
Drawing Steel (DS) Type B
Deep-Drawing Steel
Extra Deep-Drawing Steel
Dent-Resistant Steels
Bake-Hardenable Steel
Rephosphorized Steels
High-Strength Steels
Advanced High-Strength Steels
DUAL-TEN® (Dual Phase) Steel
DUAL-TEN® 590/600 Steel
DUAL-TEN® 780/800 Steel
TRIP Steels
TRIP Steel 590/600
TRIP Steel 780/800
Formability Chart: Material Based on Strength and Elongation
Product Table: Material Based on Product and U. S. Steel Availability:
HR
CR Uncoated
HDG
HDGA
EG
EGA
Low Carbon
Yes
Yes
Yes
Yes
Yes
Yes
BH
No
Yes
Yes
Yes
Yes
Yes
HSFS
No
Yes
Yes
Yes
Yes
Yes
HSLA
Yes
Yes
Yes
Yes
Yes
Yes
DP
Yes
No
Yes
Yes
No
No
TRIP
Developing
No
Developing
Developing
No
No
Trial AvailabilityU. S. Steel maintains a bank of various qualities and sizes for trial or sample purposes (please refer to above table). If you are interested in obtaining a sample or running a trial with a certain material, please contact Keith Shuttlesworth, marketing manager for the Automotive Department
1. Low-Carbon Steels
Low-Carbon Steels are produced in four principal qualities for automotive applications. The qualities listed below are organized by formability levels with the last category being the most formable:
Commercial Steel (CS) Type B
Drawing Steel (DS) Type B
Deep- Drawing Steel (DDS)
Extra Deep-Drawing Steel (EDDS)
In addition to being cost effective, low-carbon steels have a wide range of key forming characteristics. As a result, these steels can be used for almost any automotive part – from small, flat parts (brackets) to large, deep drawn parts (floor pans). Also, this material can be made for either exposed or unexposed applications.
The low carbon content found in these mild steels will perform well with typical automotive welding techniques, but the relatively low yield strength, as compared to other steels, may limit its usefulness where dent resistance is important. Finally, high-strength steels and/or advanced high-strength steels should be considered for crash-sensitive parts because they perform better with respect to crash energy management. Due to its versatility and low cost, low-carbon steel is an effective material for most automotive applications.
Commercial Steel (CS) Type B
Commercial Steel (CS) Type B is a low-carbon steel used in many automotive applications where simple bending or moderate forming is required. This grade can be bent flat on itself in any direction at room temperature. If drawing depth is more severe, please refer to DS Type B Steels.
CS Type B is susceptible to aging, which may cause problems such as stretcher strains, fluting, coil breaks (in heavy gauges), loss of ductility and increased hardness. Roller leveling this grade prior to forming will reduce the chance for stretcher strains or fluting caused by aging. However, leveling will not restore softness or ductility.
Weldability – Low carbon level makes this a good welding candidate.
Fatigue Performance – Compared to other low-carbon steels, CS Type B has the highest yield strength, which means it will have a good resistance to fatigue. But higher strength steels may be better candidates for durability sensitive components.
Denting – CS Type B is not used on exposed applications due to the aging characteristics. For dent-resistant grades and capabilities, please check our dent- resistant steels.
Applications – CS Type B is a product that is best suited for unexposed applications. These materials work well for applications with very little depth of draw. CS Type B is typically used on truck bed floors and other floor pans with little formability requirements. Other suitable parts are truck cab backs and tailgate access covers.
Typical Properties for CS Type B:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
230
345
31
N/A
N/A
Cold Roll
207
304
38
N/A
N/A
EG
210
293
37
N/A
N/A
HDGI
269
345
40
0.210
N/A
HDGA
269
345
40
0.210
N/A
Drawing Steel (DS) Type B
DS Type B Replaces Drawing Quality (DQ) and Drawing Quality Special Killed Steels (DQSK)
Drawing Steel (DS) Type B has a greater degree of ductility and is more consistent in performance than Commercial Steel Type B because of higher standards in production, selection and melting of steel. The improved ductility and uniformity of properties of Drawing Steel compared to Commercial Steel sheet means that it provides improved performance during manufacturing. If drawing depth is more severe, please refer to Deep-Drawing Steels or Extra Deep-Drawing Steels.
DS Type B must be ordered within the following compositional limits:C - 0.02/0.08, Mn - 0.50 max., P - 0.020 max., and S - 0.030 max.
Weldability – Low carbon level makes this a good welding candidate.
Fatigue Performance – Relatively low yield, compared to other steels, makes this grade more susceptible to fatigue than higher strength steels.
Denting – Relatively low yield strength, compared to other steels, may make DS Type B more susceptible to denting. For additional capabilities, please check our dent-resistant steels.
Applications - DS Type B is the most common material found in automotive stampings today. This material offers the formability that is required to produce parts with some depth of draw. Typical applications would include body sides, roofs, floor pans, reinforcements, doors, deck lids and hoods.
Typical Properties for DS Type B
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
217
331
34
N/A
N/A
Cold Roll
175
297
44
0.232
view
EG
181
310
43
0.224
view
EG Alloy
183
313
43
0.218
view
Deep-Drawing Steel (DDS)
U. S. Steel provides DDS as a low-carbon steel grade to meet improved drawability compared with DS Type B. The usual metallurgical approach is to provide DDS as a low carbon/low manganese steel chemistry combined with low amounts of residual elements. Cold Rolled and Electrolytic Zinc & Zinc-Iron Alloy steels will use the following compositional limits: C-0.06 max., Mn-0.50 max., P-0.020 max. and S-0.025 max.
The Hot-Dip Galvanized and Galvannealed DDS substrate is produced from aluminum-killed steel employing special steelmaking practices. It can be produced using restricted low-carbon steels or interstitial-free steels depending on the application requirement and the producing facility. It has forming characteristics superior to CS and FS sheet. These characteristics make it excellent for applications involving deep drawing or combinations of drawing and stretching. The Hot-Dip Galvanized and Galvannealed DDS substrate will use the following compositional limits: C-0.06 max., Mn-0.50 max., P-0.020 max. and S-0.025 max.
Weldability – Low carbon level makes this a good welding candidate.
Fatigue Performance – Relatively low yield, compared to other steels, makes this grade more susceptible to fatigue than higher strength steels.
Denting – Relatively low yield strength, compared to other steels, may make DDS more susceptible to denting. For additional capabilities, please check our dent-resistant steels.
Applications – DDS is very similar to DS Type B. This material offers more formability to produce parts with a moderate depth of draw. Typical applications would include body sides, roofs, floor pans, reinforcements, doors, deck lids and hoods with difficult shapes.
Typical Properties for DDS:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
207
317
36
N/A
N/A
Cold Roll
168
279
45
0.235
N/A
EG
182
307
41
0.228
N/A
EG Alloy
183
313
41
0.227
view
HDGI
152
296
47
0.240
N/A
HDGA
152
303
45
0.234
view
Deep-Drawing Steel (DDS)
U. S. Steel provides DDS as a low-carbon steel grade to meet improved drawability compared with DS Type B. The usual metallurgical approach is to provide DDS as a low carbon/low manganese steel chemistry combined with low amounts of residual elements. Cold Rolled and Electrolytic Zinc & Zinc-Iron Alloy steels will use the following compositional limits: C-0.06 max., Mn-0.50 max., P-0.020 max. and S-0.025 max.
The Hot-Dip Galvanized and Galvannealed DDS substrate is produced from aluminum-killed steel employing special steelmaking practices. It can be produced using restricted low-carbon steels or interstitial-free steels depending on the application requirement and the producing facility. It has forming characteristics superior to CS and FS sheet. These characteristics make it excellent for applications involving deep drawing or combinations of drawing and stretching. The Hot-Dip Galvanized and Galvannealed DDS substrate will use the following compositional limits: C-0.06 max., Mn-0.50 max., P-0.020 max. and S-0.025 max.
Weldability – Low carbon level makes this a good welding candidate.
Fatigue Performance – Relatively low yield, compared to other steels, makes this grade more susceptible to fatigue than higher strength steels.
Denting – Relatively low yield strength, compared to other steels, may make DDS more susceptible to denting. For additional capabilities, please check our dent-resistant steels.
Applications – DDS is very similar to DS Type B. This material offers more formability to produce parts with a moderate depth of draw. Typical applications would include body sides, roofs, floor pans, reinforcements, doors, deck lids and hoods with difficult shapes.
Typical Properties for DDS:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
207
317
36
N/A
N/A
Cold Roll
168
279
45
0.235
N/A
EG
182
307
41
0.228
N/A
EG Alloy
183
313
41
0.227
view
HDGI
152
296
47
0.240
N/A
HDGA
152
303
45
0.234
view
Extra Deep-Drawing Steel (EDDS)
EDDS is produced from vacuum degassed steel to achieve a very low carbon content. It is chemically stabilized with elements such as titanium and niobium (columbium) during production to combine the remaning residual amounts of carbon and nitrogen to make it "interstitial-free." Excellent uniformity and exceptional formability characterize coated and uncoated sheet of this quality. The final product is excellent for deep drawn parts in that the sheet exhibits a high resistance to thinning during drawing.
EDDS sheet is non-aging, thus coil breaks, strain lines and fluting during fabrication are not encountered.
Weldability – Low carbon level makes this a good welding candidate.
Fatigue Performance – Relatively low yield, compared to other steels, makes this grade more susceptible to fatigue than higher strength steels.
Denting – Relatively low yield strength, compared to other steels, may make EDDS more susceptible to denting. For additional capabilities, please check our dent-resistant steels.
Applications – EDDS is used in applications where severe forming characteristics are required. EDDS is typically found in door inners, dash panels, body side inners and floor pans with spare tire tubs.
Typical Properties for EDDS:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Cold Roll
155
297
45
0.256
view
EG
168
304
44
.239
view
EG Alloy
168
308
44
0.239
view
HDGI
145
303
46
0.240
view
HDGA
145
303
46
0.240
view
2. Dent-Resistant Steels
In recent years, weight reduction efforts have led to the decrease in the thickness of all automotive components. As a result, new grades of steel have been developed to resist the tendency of thin-gage, exposed panels to permanently dent. Palm printing and/or denting is caused by a variety of factors such as hail, thrown stones or out-of-control shopping carts.
Dent-resistant steels are produced in two principal grades:
Bake- Hardenable Steel
Rephosphorized Steels
Dent-resistant steels are relatively new to the automotive industry. In general, they offer a combination of formability and high yield strength that is not attainable with low-carbon, mild steels or conventional high-strength steels. Dent-resistant steels provide customers with a material that is capable of reducing the severity and number of dents and dings found on the outer body panels of today’s cars.
These materials have the formability requirements needed to produce most exterior applications. The dent resistance of these exterior parts benefits from both the work and/or bake hardening effects that are experienced during processing. These parts include doors, deck lids, quarter panels, fenders, hoods and roofs. Please refer to the descriptions of each of the different dent resistant steels for more specific information about material properties and characteristics.
Bake-Hardenable (BH) Steels
A bake-hardenable steel is any steel that exhibits a capacity for a significant increase in strength through the combination of work hardening during part formation and strain aging during a subsequent thermal cycle such as a paint-baking operation. These steels are made in the following grades:
BH180
BH210
BH240
Any steel with adequate carbon and/or nitrogen in solution to cause strain-aging may be classified as bake-hardenable. In general, bake-hardenable steels are aluminum-killed steels with an adequate amount of aluminum to combine with the nitrogen as Aluminum Nitride (AlN).
A combination of relatively low yield strength prior to manufacturing and a high in-part strength after forming and paint baking makes bake-hardenable steels ideal for applications where dent and palm printing resistance is important. This material can be used in relatively deep draw or stretching operations. Due to the high in-part strength, bake-hardenable parts are also good candidates for downgaging, which is important for weight reduction efforts.
When using bake-hardenable steel, the amount of strain introduced during the forming process will largely dictate the final strength of the part. Since automotive parts, specifically exposed body panels, have a wide array of designs, there will be a corresponding disparity in the amount of strain introduced in these varying geometries. As a result, when using bake-hardenable steel, it is important to design an adequate amount of strain into a part in order to fully utilize this material’s dent resistant characteristics.
Weldability – Low carbon level makes bake-hardenable steel a good welding candidate.
Fatigue Performance – If used properly, bake-hardenable steels have a high yield strength after forming and baking, which means it will have a good resistance to fatigue.
Denting – Bake-hardenable steels were designed for dent resistance.
Applications – Bake-hardenable materials provide customers with a material that is capable of reducing the amount of dents and dings found on today’s cars. These materials have the formability requirements needed to produce most exterior applications. These exterior parts benefit from the work and bake hardening kicks that are experienced during processing. These parts include doors, deck lids, quarter panels, fenders, hoods and roofs.
Increase in yield strength during forming and baking of bake-hardenable steels
Typical Properties for BH 180 MPa:(Back to top)
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Cold Roll
196
325
38.9
0.210
N/A
EG
196
325
38.9
0.210
N/A
EG Alloy
196
325
38.9
0.210
N/A
HDGI
185
305
39.3
0.210
N/A
HDGA
185
305
39.3
0.210
N/A
Typical Properties for BH 210 MPa:(Back to top)
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Cold Roll
223
344
37.8
0.200
N/A
EG
223
344
37.8
0.200
N/A
EGA
223
344
37.8
0.200
N/A
HDGI
230
355
34.2
0.190
N/A
HDGA
230
355
34.2
0.190
N/A
Typical Properties for BH 240 MPa:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
EG
256
378
34.7
0.190
N/A
Rephosphorized Steels
A rephosphorized steel is any steel that exhibits a capacity for a significant increase in strength through work hardening during part formation. This steel will not achieve any increase in strength from a thermal cycle and is therefore referred to as non bake-hardenable. Rephosphorized steels are made in the following grades. Users can find more specific material property information about these grades by following the links provided.
180A
210A
In order to increase initial strengths, solid solution strengthening elements such as phosphorus, manganese and/or silicon are added to the nominal chemistry. The amount of additional strength from work hardening will depend on the amount of carbon remaining in solution, which is controlled through chemistry and thermo-mechanical processing. Columbium, vanadium or titanium may be used in small quantities, but they will reduce ductility.
A combination of relatively low yield strength prior to manufacturing and a high in-part strength after forming makes rephosphorized steels good candidates for applications where dent and palm printing resistance is important. This material can be used in relatively deep draw or stretching operations. Due to the high in-part strength, rephosphorized parts are also good candidates for downgaging, which is important for weight reduction efforts.
When using rephosphorized steel, the amount of strain introduced during the forming process will largely dictate the final strength of the part. Since automotive parts, specifically exposed body panels, have a wide array of designs, there will be a corresponding disparity in the amount of strain introduced in these varying geometries. As a result, when using rephosphorized steel, it is important to design an adequate amount of strain into a part in order to fully utilize this material’s dent resistant characteristics.
Weldability – Low carbon level makes rephosphorized steel a good welding candidate.
Fatigue Performance – If used properly, rephosphorized steels have a high yield strength after forming, which means it will have a good resistance to fatigue.
Denting – Rephosphorized steels were designed for dent resistance.
Applications – Rephosphorized materials provide customers with a material that is capable of reducing the amount of dents and dings found on today’s cars. These materials have the formability requirements needed to produce most exterior applications. These exterior parts benefit from the work and bake hardening kicks that are experienced during processing. These parts include doors, deck lids, quarter panels, fenders, hoods and roofs.
Typical Properties for 180A MPa:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Cold Roll
195
352
46.3
0.220
N/A
EG
195
352
46.3
0.220
N/A
EG Alloy
195
352
4
0.220
N/A
HDGI
199
352
38.8
0.220
N/A
HDGA
199
352
38.8
0.220
N/A
Typical Properties for 210A MPa: (Back to top)
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Cold Roll
223
344
37.8
0.200
N/A
EG
233
344
37.8
0.200
N/A
EG Alloy
223
344
37.8
0.200
N/A
HDGI
230
355
35.8
0.200
N/A
HDGA
230
355
35.8
0.200
N/A
3. High-Strength Low-Alloy (HSLA) Steels
High-strength low-alloy steel (HSLA) grades have a good combination of formability and weldability. Successfully forming a complex part with HSLA can be difficult, but is possible with a well thought-out design. This grade will provide mass reduction in most automotive applications.
The strength of HSLA steels is achieved by the addition of small quantities of alloying elements.
Weldability – Good welding characteristics.
Fatigue Performance – High-strength steels have good resistance to fatigue due to their relatively high yield strengths. Therefore, HSLA is a good candidate for durability sensitive components.
Denting – Good dent resistance capabilities. For additional capabilities, please check our dent-resistant steels.
Applications - HSLA materials are typically found on structural parts of the vehicle. Most HSLA materials have very limited formability characteristics. The materials are found on rocker inners, b/c pillar reinforcements and cross members.
Typical Properties for HSLA 280MPa:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
Stress/Strain Curve
Hot Roll
310
380
28
N/A
N/A
Cold Roll
303
372
26
N/A
N/A
HDGI
300
384
36.5
0.195
view
Typical Properties for HSLA 340MPa:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
380
450
25.6
N/A
N/A
Cold Roll
370
445
26.7
0.155
view
HDGI
378
458
30.0
0.170
view
HDGA
378
458
30.0
0.170
N/A
Typical Properties for HSLA 410MPa:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
462
558
26
N/A
N/A
HDGI
420
500
27
0.15
N/A
4. Advanced High-Strength Steels (AHSS)
Advanced high-strength steels (AHSS) include DUAL-TEN® (dual phase) steel and transformation induced plasticity (TRIP) steels. The minimum tensile strengths range from 500 to 800 MPa. These steels are gaining popularity in automotive applications because they are easier to form than HSLA grades with similar initial yield strengths, but have a much higher final part strength.
As a result, today's automobile manufacturers are increasingly using DUAL-TEN®steel to reduce mass, reduce cost and improve crash energy management. In addition, these advanced high-strength steels are ideal for fatigue and durability sensitive parts or thin-gauge exposed panels that are subjected to denting loads. With proper design strategy, DUAL-TEN® steels offer a great opportunity for part downgaging, body in white weight reduction, improvement of car fuel economy, and crash performance.
Product Descriptions
DUAL-TEN® Steel
DUAL-TEN® - 590/600 Steel
DUAL-TEN® - 780/800 Steel
TRIP Steels
TRIP - 590/600 Steel
TRIP - 780/800 Steel
The unique characteristics of advanced high-strength steels are developed by a continuous heat treating process that creates martensite in the steel microstructure. The amount of martensite, together with the amount of carbon, will determine the strength level of the steel. When compared to other grades, specifically high-strength, low-alloy steels, the classification for advanced high-strength steels are based on minimum tensile strength.
DUAL-TEN® (dual phase) Steels
DUAL-TEN® (dual phase) steels are quickly becoming one of the most popular and versatile materials in today's automotive industry. Currently, these steels are most commonly used in structural applications where they have replaced more conventional HSLA steels. They offer a great opportunity for part weight reduction. The improved formability, capacity to absorb crash energy, and ability to resist fatigue have driven this substitution. Today's applications include front and rear rails, crush cans, rocker reinforcements, b/c pillar reinforcements, cowl inner/outer, back panels, cross members, bumpers and door intrusion beams. Recently, DUAL-TEN® steels have gained in popularity in automotive closures.
DUAL-TEN® steels are made in the following grades. You can find more specific material property information about these grades in our online brochure or by following the links provided.
DUAL-TEN® 590/600 steel
DUAL-TEN® 780/800 steel
In general, DUAL-TEN® steel is a mixture of ferrite matrix and martensite islands decorating grain boundaries with possible addition of bainite. Formable DUAL-TEN® steels contain approximately 5% - 15% martensite. Refer to Figure - 1.
- Ferrite - soft phase, offers ductility - Martensite - hard phase, offers strength
Figure - 1: Example of DUAL-TEN® 600 steel structure, 1000x
Characteristics of DUAL-TEN® steels:
Work hardening - DUAL-TEN® steel displays a high and rapid initial work hardening rate. Even at low forming strain levels (2% - 3%), yield strength increases approximately 21-31 ksi (145-214 MPa). Refer to Figure - 2.
Yield point elongation - Tested DUAL-TEN® 590/600 and DUAL-TEN® 780 steels show no yield point elongation. Refer to Figure - 3.
Formability - Due to a higher work-hardening rate and absence of YPE, DUAL-TEN® steels behave predictably in stamping processes (i.e. resistance to necking, plastic instability and kinking).
FLD curves - For the needs of forming feasibility analysis, FLD can be approximated with sufficient accuracy by the conventional ASM-FLD calculated from n-value and thickness. Refer to Table - 1, Figure - 4 and Figure - 5.
Springback - As compared to conventional HSLA steels, springback is easier to control due to consistent behavior during stamping. Refer to Figure - 6.
Bendability - DUAL-TEN® steel has very good bendability. Refer to Figure - 7.
Bake hardening - DUAL-TEN® steels have an excellent bake hardening capacity. The increase in the yield strength resulting from typical paint baking cycle is approximately 5-10 ksi (35-70 MPa). Refer to Figure - 8 and Figure - 9.
In-part strength - DUAL-TEN® (dual phase) steels have a high ultimate tensile strength (UTS). UTS ranges from 72-175 ksi (500-1200 MPa) for available grades.
Shelf life - DUAL-TEN® steel displays no room temperature aging.
Mass reduction capability - These steels have high potential for part downgaging and weight reduction (up to 25% as compared to equivalent conventional HSLA steels).
Crash energy management - DUAL-TEN® steels have a higher yield to tensile ratio as compared to conventional HSLA steels (0.5-0.6). This results in a higher capacity to manage vehicle crash energy.
Fatigue performance - DUAL-TEN® steels have a higher fatigue strength than equivalent conventional HSLA steels.
Weldability - DUAL-TEN® steel meets automotive application weldability needs.
Figure - 2: Example of work hardening rate for DUAL-TEN® 590/600 steel: Instantaneous n-value as a function of engineering strain. Note the characteristic high n-value in the low plastic deformation range.
Return to DUAL-TEN® steel characteristics
Figure - 3: Examples of stress strain curves for DUAL-TEN® steels as compared with various grades.
Return to DUAL-TEN® steel characteristics
Table - 1: Comparison of mechanical properties for DUAL-TEN® 590 and HSLA 340 steels
Material
Yield Strength (ksi)
Tensile Strength (ksi)
YPE (%)
Elongation (%)
n-value 10%-UE
DUAL-TEN® 590
375
640
24.5
0.170
HSLA 340
378
458
2.8
30.0
0.170
Return to DUAL-TEN® steel characteristics
Figure - 4: Experimental forming limit curve for material thickness of 1.8mm. A conventional ASM FLC calculated from n-value and thickness can be used for DUAL-TEN® steel with sufficient accuracy.
Figure - 5: Experimental forming limit curve for material thickness of 1.2mm. A conventional ASM FLC calculated from n-value and thickness can be used for DUAL-TEN® steel with sufficient accuracy.
Return to DUAL-TEN® steel characteristics
Figure - 6: Springback. Results of bending under tension test. Various back tension forces at constant ratio of bending radius to material thickness, R/t = 2.14. For the top samples, back tension is 85% YS, the middle is 75% YS, and the bottom is 50% YS. Two samples are shown in the picture for each case. Note consistent geometry for DUAL-TEN® 590. Dimensional accuracy of parts made of DUAL-TEN® steel can be controlled easier due to consistent material behavior in plastic deformation.
Return to DUAL-TEN® steel characteristics
Figure - 7: Bendability in a free-bending test. Results of the bendability test for DUAL-TEN® 590 steel: a) inner radius close to zero, b) inner radius close to the half of the material thickness. Note material folding tendencies in the inner radius area. Bending with inner radius close to zero can be performed successfully without fracture on the outer bend line.
Return to DUAL-TEN® steel characteristics
Figure - 8: Bake hardening in paint baking cycle. Increase in yield strength due to bake hardening for DUAL-TEN® 590 steel at various pre-strain levels.
Return to DUAL-TEN® steel characteristics
Figure - 9: Combined effect of work hardening (WH) and bake hardening (BH). Yield strength of DUAL-TEN® 600 steel increases more than 260 MPa after deformation to 5% and baking in a typical paint baking cycle.
Return to DUAL-TEN® steel characteristics
TRIP Steels
TRIP steels are one of the newest and most exciting materials being developed by the steel industry. In relation to other advanced high-strength steels, TRIP steels exhibit better ductility at a given strength level. This enhanced formability comes from the transformation of retained austenite (ductile, high temperature phase of iron) to martensite (tough, non-equilibrium phase) during plastic deformation. In fact, the acronym “TRIP” stands for TRansformation Induced Plasticity. Because of this increased formability, TRIP steels can be used to produce more complicated parts than other high strength steels, allowing the automotive engineer more freedom in part design to optimize weight and structural performance.
Comparison of DUAL-TEN® (dual phase) steel vs. TRIP steel
DUAL-TEN® Steel
Topic Area
TRIP Steel
Ferrite-martensite
Microstructure
Ferrite-bainite-austenite
None
Yield Point Elongation
Yes
Good
Formability for strength level
Very Good
Excellent
Bake Hardening
Excellent
Good
Strain Rate Sensitivity
Excellent
Good
Fatigue
Good
OK
Weldability
More difficult than DUAL-TEN®
The characteristics of TRIP steel make it especially useful for difficult to form parts. These components can benefit from the increased strength and strain rate sensitivity that TRIP offers.
Typical Grades
Various tensile strengths from 500 MPa to 800 MPa
590/600T
780/800T
Typical Microstructure
The microstructure of unformed TRIP steel consists of varying amounts of ferrite, bainite and retained austenite depending on the strength level desired.
Characteristics of TRIP steels
Work hardening – As compared with other high-strength steels, TRIP steel displays higher work hardening rate in entire range of plastic deformation.
Yield point elongation (YPE) - Tested as delivered, TRIP steels usually show YPE; however, some grades may have no YPE.
Formability – Due to high work hardening rate, TRIP steel behaves in a stable way in stamping processes (resistance to onset necking) and displays remarkably high formability (high potential to form parts of complex geometry).
Bendability – TRIP steel demonstrates good bendability; As a result, product and process design solutions leading to springback control are easier to implement.
Bake hardening – TRIP steels have an excellent bake-hardening capacity. The increase in the yield strength in a typical paint baking cycle is approximately 10 ksi (70 MPa).
Product mass reduction capacity – TRIP steels have high potential for part downgauging and weight reduction.
Fatigue performance – TRIP steels have higher fatigue strength than equivalent conventional HSLA steels.
Grades and Products
Low-Carbon Steels
Commercial Steel (CS) Type B
Drawing Steel (DS) Type B
Deep-Drawing Steel
Extra Deep-Drawing Steel
Dent-Resistant Steels
Bake-Hardenable Steel
Rephosphorized Steels
High-Strength Steels
Advanced High-Strength Steels
DUAL-TEN® (Dual Phase) Steel
DUAL-TEN® 590/600 Steel
DUAL-TEN® 780/800 Steel
TRIP Steels
TRIP Steel 590/600
TRIP Steel 780/800
Formability Chart: Material Based on Strength and Elongation
Product Table: Material Based on Product and U. S. Steel Availability:
HR
CR Uncoated
HDG
HDGA
EG
EGA
Low Carbon
Yes
Yes
Yes
Yes
Yes
Yes
BH
No
Yes
Yes
Yes
Yes
Yes
HSFS
No
Yes
Yes
Yes
Yes
Yes
HSLA
Yes
Yes
Yes
Yes
Yes
Yes
DP
Yes
No
Yes
Yes
No
No
TRIP
Developing
No
Developing
Developing
No
No
Trial AvailabilityU. S. Steel maintains a bank of various qualities and sizes for trial or sample purposes (please refer to above table). If you are interested in obtaining a sample or running a trial with a certain material, please contact Keith Shuttlesworth, marketing manager for the Automotive Department
1. Low-Carbon Steels
Low-Carbon Steels are produced in four principal qualities for automotive applications. The qualities listed below are organized by formability levels with the last category being the most formable:
Commercial Steel (CS) Type B
Drawing Steel (DS) Type B
Deep- Drawing Steel (DDS)
Extra Deep-Drawing Steel (EDDS)
In addition to being cost effective, low-carbon steels have a wide range of key forming characteristics. As a result, these steels can be used for almost any automotive part – from small, flat parts (brackets) to large, deep drawn parts (floor pans). Also, this material can be made for either exposed or unexposed applications.
The low carbon content found in these mild steels will perform well with typical automotive welding techniques, but the relatively low yield strength, as compared to other steels, may limit its usefulness where dent resistance is important. Finally, high-strength steels and/or advanced high-strength steels should be considered for crash-sensitive parts because they perform better with respect to crash energy management. Due to its versatility and low cost, low-carbon steel is an effective material for most automotive applications.
Commercial Steel (CS) Type B
Commercial Steel (CS) Type B is a low-carbon steel used in many automotive applications where simple bending or moderate forming is required. This grade can be bent flat on itself in any direction at room temperature. If drawing depth is more severe, please refer to DS Type B Steels.
CS Type B is susceptible to aging, which may cause problems such as stretcher strains, fluting, coil breaks (in heavy gauges), loss of ductility and increased hardness. Roller leveling this grade prior to forming will reduce the chance for stretcher strains or fluting caused by aging. However, leveling will not restore softness or ductility.
Weldability – Low carbon level makes this a good welding candidate.
Fatigue Performance – Compared to other low-carbon steels, CS Type B has the highest yield strength, which means it will have a good resistance to fatigue. But higher strength steels may be better candidates for durability sensitive components.
Denting – CS Type B is not used on exposed applications due to the aging characteristics. For dent-resistant grades and capabilities, please check our dent- resistant steels.
Applications – CS Type B is a product that is best suited for unexposed applications. These materials work well for applications with very little depth of draw. CS Type B is typically used on truck bed floors and other floor pans with little formability requirements. Other suitable parts are truck cab backs and tailgate access covers.
Typical Properties for CS Type B:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
230
345
31
N/A
N/A
Cold Roll
207
304
38
N/A
N/A
EG
210
293
37
N/A
N/A
HDGI
269
345
40
0.210
N/A
HDGA
269
345
40
0.210
N/A
Drawing Steel (DS) Type B
DS Type B Replaces Drawing Quality (DQ) and Drawing Quality Special Killed Steels (DQSK)
Drawing Steel (DS) Type B has a greater degree of ductility and is more consistent in performance than Commercial Steel Type B because of higher standards in production, selection and melting of steel. The improved ductility and uniformity of properties of Drawing Steel compared to Commercial Steel sheet means that it provides improved performance during manufacturing. If drawing depth is more severe, please refer to Deep-Drawing Steels or Extra Deep-Drawing Steels.
DS Type B must be ordered within the following compositional limits:C - 0.02/0.08, Mn - 0.50 max., P - 0.020 max., and S - 0.030 max.
Weldability – Low carbon level makes this a good welding candidate.
Fatigue Performance – Relatively low yield, compared to other steels, makes this grade more susceptible to fatigue than higher strength steels.
Denting – Relatively low yield strength, compared to other steels, may make DS Type B more susceptible to denting. For additional capabilities, please check our dent-resistant steels.
Applications - DS Type B is the most common material found in automotive stampings today. This material offers the formability that is required to produce parts with some depth of draw. Typical applications would include body sides, roofs, floor pans, reinforcements, doors, deck lids and hoods.
Typical Properties for DS Type B
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
217
331
34
N/A
N/A
Cold Roll
175
297
44
0.232
view
EG
181
310
43
0.224
view
EG Alloy
183
313
43
0.218
view
Deep-Drawing Steel (DDS)
U. S. Steel provides DDS as a low-carbon steel grade to meet improved drawability compared with DS Type B. The usual metallurgical approach is to provide DDS as a low carbon/low manganese steel chemistry combined with low amounts of residual elements. Cold Rolled and Electrolytic Zinc & Zinc-Iron Alloy steels will use the following compositional limits: C-0.06 max., Mn-0.50 max., P-0.020 max. and S-0.025 max.
The Hot-Dip Galvanized and Galvannealed DDS substrate is produced from aluminum-killed steel employing special steelmaking practices. It can be produced using restricted low-carbon steels or interstitial-free steels depending on the application requirement and the producing facility. It has forming characteristics superior to CS and FS sheet. These characteristics make it excellent for applications involving deep drawing or combinations of drawing and stretching. The Hot-Dip Galvanized and Galvannealed DDS substrate will use the following compositional limits: C-0.06 max., Mn-0.50 max., P-0.020 max. and S-0.025 max.
Weldability – Low carbon level makes this a good welding candidate.
Fatigue Performance – Relatively low yield, compared to other steels, makes this grade more susceptible to fatigue than higher strength steels.
Denting – Relatively low yield strength, compared to other steels, may make DDS more susceptible to denting. For additional capabilities, please check our dent-resistant steels.
Applications – DDS is very similar to DS Type B. This material offers more formability to produce parts with a moderate depth of draw. Typical applications would include body sides, roofs, floor pans, reinforcements, doors, deck lids and hoods with difficult shapes.
Typical Properties for DDS:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
207
317
36
N/A
N/A
Cold Roll
168
279
45
0.235
N/A
EG
182
307
41
0.228
N/A
EG Alloy
183
313
41
0.227
view
HDGI
152
296
47
0.240
N/A
HDGA
152
303
45
0.234
view
Deep-Drawing Steel (DDS)
U. S. Steel provides DDS as a low-carbon steel grade to meet improved drawability compared with DS Type B. The usual metallurgical approach is to provide DDS as a low carbon/low manganese steel chemistry combined with low amounts of residual elements. Cold Rolled and Electrolytic Zinc & Zinc-Iron Alloy steels will use the following compositional limits: C-0.06 max., Mn-0.50 max., P-0.020 max. and S-0.025 max.
The Hot-Dip Galvanized and Galvannealed DDS substrate is produced from aluminum-killed steel employing special steelmaking practices. It can be produced using restricted low-carbon steels or interstitial-free steels depending on the application requirement and the producing facility. It has forming characteristics superior to CS and FS sheet. These characteristics make it excellent for applications involving deep drawing or combinations of drawing and stretching. The Hot-Dip Galvanized and Galvannealed DDS substrate will use the following compositional limits: C-0.06 max., Mn-0.50 max., P-0.020 max. and S-0.025 max.
Weldability – Low carbon level makes this a good welding candidate.
Fatigue Performance – Relatively low yield, compared to other steels, makes this grade more susceptible to fatigue than higher strength steels.
Denting – Relatively low yield strength, compared to other steels, may make DDS more susceptible to denting. For additional capabilities, please check our dent-resistant steels.
Applications – DDS is very similar to DS Type B. This material offers more formability to produce parts with a moderate depth of draw. Typical applications would include body sides, roofs, floor pans, reinforcements, doors, deck lids and hoods with difficult shapes.
Typical Properties for DDS:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
207
317
36
N/A
N/A
Cold Roll
168
279
45
0.235
N/A
EG
182
307
41
0.228
N/A
EG Alloy
183
313
41
0.227
view
HDGI
152
296
47
0.240
N/A
HDGA
152
303
45
0.234
view
Extra Deep-Drawing Steel (EDDS)
EDDS is produced from vacuum degassed steel to achieve a very low carbon content. It is chemically stabilized with elements such as titanium and niobium (columbium) during production to combine the remaning residual amounts of carbon and nitrogen to make it "interstitial-free." Excellent uniformity and exceptional formability characterize coated and uncoated sheet of this quality. The final product is excellent for deep drawn parts in that the sheet exhibits a high resistance to thinning during drawing.
EDDS sheet is non-aging, thus coil breaks, strain lines and fluting during fabrication are not encountered.
Weldability – Low carbon level makes this a good welding candidate.
Fatigue Performance – Relatively low yield, compared to other steels, makes this grade more susceptible to fatigue than higher strength steels.
Denting – Relatively low yield strength, compared to other steels, may make EDDS more susceptible to denting. For additional capabilities, please check our dent-resistant steels.
Applications – EDDS is used in applications where severe forming characteristics are required. EDDS is typically found in door inners, dash panels, body side inners and floor pans with spare tire tubs.
Typical Properties for EDDS:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Cold Roll
155
297
45
0.256
view
EG
168
304
44
.239
view
EG Alloy
168
308
44
0.239
view
HDGI
145
303
46
0.240
view
HDGA
145
303
46
0.240
view
2. Dent-Resistant Steels
In recent years, weight reduction efforts have led to the decrease in the thickness of all automotive components. As a result, new grades of steel have been developed to resist the tendency of thin-gage, exposed panels to permanently dent. Palm printing and/or denting is caused by a variety of factors such as hail, thrown stones or out-of-control shopping carts.
Dent-resistant steels are produced in two principal grades:
Bake- Hardenable Steel
Rephosphorized Steels
Dent-resistant steels are relatively new to the automotive industry. In general, they offer a combination of formability and high yield strength that is not attainable with low-carbon, mild steels or conventional high-strength steels. Dent-resistant steels provide customers with a material that is capable of reducing the severity and number of dents and dings found on the outer body panels of today’s cars.
These materials have the formability requirements needed to produce most exterior applications. The dent resistance of these exterior parts benefits from both the work and/or bake hardening effects that are experienced during processing. These parts include doors, deck lids, quarter panels, fenders, hoods and roofs. Please refer to the descriptions of each of the different dent resistant steels for more specific information about material properties and characteristics.
Bake-Hardenable (BH) Steels
A bake-hardenable steel is any steel that exhibits a capacity for a significant increase in strength through the combination of work hardening during part formation and strain aging during a subsequent thermal cycle such as a paint-baking operation. These steels are made in the following grades:
BH180
BH210
BH240
Any steel with adequate carbon and/or nitrogen in solution to cause strain-aging may be classified as bake-hardenable. In general, bake-hardenable steels are aluminum-killed steels with an adequate amount of aluminum to combine with the nitrogen as Aluminum Nitride (AlN).
A combination of relatively low yield strength prior to manufacturing and a high in-part strength after forming and paint baking makes bake-hardenable steels ideal for applications where dent and palm printing resistance is important. This material can be used in relatively deep draw or stretching operations. Due to the high in-part strength, bake-hardenable parts are also good candidates for downgaging, which is important for weight reduction efforts.
When using bake-hardenable steel, the amount of strain introduced during the forming process will largely dictate the final strength of the part. Since automotive parts, specifically exposed body panels, have a wide array of designs, there will be a corresponding disparity in the amount of strain introduced in these varying geometries. As a result, when using bake-hardenable steel, it is important to design an adequate amount of strain into a part in order to fully utilize this material’s dent resistant characteristics.
Weldability – Low carbon level makes bake-hardenable steel a good welding candidate.
Fatigue Performance – If used properly, bake-hardenable steels have a high yield strength after forming and baking, which means it will have a good resistance to fatigue.
Denting – Bake-hardenable steels were designed for dent resistance.
Applications – Bake-hardenable materials provide customers with a material that is capable of reducing the amount of dents and dings found on today’s cars. These materials have the formability requirements needed to produce most exterior applications. These exterior parts benefit from the work and bake hardening kicks that are experienced during processing. These parts include doors, deck lids, quarter panels, fenders, hoods and roofs.
Increase in yield strength during forming and baking of bake-hardenable steels
Typical Properties for BH 180 MPa:(Back to top)
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Cold Roll
196
325
38.9
0.210
N/A
EG
196
325
38.9
0.210
N/A
EG Alloy
196
325
38.9
0.210
N/A
HDGI
185
305
39.3
0.210
N/A
HDGA
185
305
39.3
0.210
N/A
Typical Properties for BH 210 MPa:(Back to top)
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Cold Roll
223
344
37.8
0.200
N/A
EG
223
344
37.8
0.200
N/A
EGA
223
344
37.8
0.200
N/A
HDGI
230
355
34.2
0.190
N/A
HDGA
230
355
34.2
0.190
N/A
Typical Properties for BH 240 MPa:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
EG
256
378
34.7
0.190
N/A
Rephosphorized Steels
A rephosphorized steel is any steel that exhibits a capacity for a significant increase in strength through work hardening during part formation. This steel will not achieve any increase in strength from a thermal cycle and is therefore referred to as non bake-hardenable. Rephosphorized steels are made in the following grades. Users can find more specific material property information about these grades by following the links provided.
180A
210A
In order to increase initial strengths, solid solution strengthening elements such as phosphorus, manganese and/or silicon are added to the nominal chemistry. The amount of additional strength from work hardening will depend on the amount of carbon remaining in solution, which is controlled through chemistry and thermo-mechanical processing. Columbium, vanadium or titanium may be used in small quantities, but they will reduce ductility.
A combination of relatively low yield strength prior to manufacturing and a high in-part strength after forming makes rephosphorized steels good candidates for applications where dent and palm printing resistance is important. This material can be used in relatively deep draw or stretching operations. Due to the high in-part strength, rephosphorized parts are also good candidates for downgaging, which is important for weight reduction efforts.
When using rephosphorized steel, the amount of strain introduced during the forming process will largely dictate the final strength of the part. Since automotive parts, specifically exposed body panels, have a wide array of designs, there will be a corresponding disparity in the amount of strain introduced in these varying geometries. As a result, when using rephosphorized steel, it is important to design an adequate amount of strain into a part in order to fully utilize this material’s dent resistant characteristics.
Weldability – Low carbon level makes rephosphorized steel a good welding candidate.
Fatigue Performance – If used properly, rephosphorized steels have a high yield strength after forming, which means it will have a good resistance to fatigue.
Denting – Rephosphorized steels were designed for dent resistance.
Applications – Rephosphorized materials provide customers with a material that is capable of reducing the amount of dents and dings found on today’s cars. These materials have the formability requirements needed to produce most exterior applications. These exterior parts benefit from the work and bake hardening kicks that are experienced during processing. These parts include doors, deck lids, quarter panels, fenders, hoods and roofs.
Typical Properties for 180A MPa:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Cold Roll
195
352
46.3
0.220
N/A
EG
195
352
46.3
0.220
N/A
EG Alloy
195
352
4
0.220
N/A
HDGI
199
352
38.8
0.220
N/A
HDGA
199
352
38.8
0.220
N/A
Typical Properties for 210A MPa: (Back to top)
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Cold Roll
223
344
37.8
0.200
N/A
EG
233
344
37.8
0.200
N/A
EG Alloy
223
344
37.8
0.200
N/A
HDGI
230
355
35.8
0.200
N/A
HDGA
230
355
35.8
0.200
N/A
3. High-Strength Low-Alloy (HSLA) Steels
High-strength low-alloy steel (HSLA) grades have a good combination of formability and weldability. Successfully forming a complex part with HSLA can be difficult, but is possible with a well thought-out design. This grade will provide mass reduction in most automotive applications.
The strength of HSLA steels is achieved by the addition of small quantities of alloying elements.
Weldability – Good welding characteristics.
Fatigue Performance – High-strength steels have good resistance to fatigue due to their relatively high yield strengths. Therefore, HSLA is a good candidate for durability sensitive components.
Denting – Good dent resistance capabilities. For additional capabilities, please check our dent-resistant steels.
Applications - HSLA materials are typically found on structural parts of the vehicle. Most HSLA materials have very limited formability characteristics. The materials are found on rocker inners, b/c pillar reinforcements and cross members.
Typical Properties for HSLA 280MPa:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
Stress/Strain Curve
Hot Roll
310
380
28
N/A
N/A
Cold Roll
303
372
26
N/A
N/A
HDGI
300
384
36.5
0.195
view
Typical Properties for HSLA 340MPa:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
380
450
25.6
N/A
N/A
Cold Roll
370
445
26.7
0.155
view
HDGI
378
458
30.0
0.170
view
HDGA
378
458
30.0
0.170
N/A
Typical Properties for HSLA 410MPa:
Product
Yield Strength [MPa]
Tensile Strength [MPa]
Elongation [%]
n-value
True Stress/Strain Curve
Hot Roll
462
558
26
N/A
N/A
HDGI
420
500
27
0.15
N/A
4. Advanced High-Strength Steels (AHSS)
Advanced high-strength steels (AHSS) include DUAL-TEN® (dual phase) steel and transformation induced plasticity (TRIP) steels. The minimum tensile strengths range from 500 to 800 MPa. These steels are gaining popularity in automotive applications because they are easier to form than HSLA grades with similar initial yield strengths, but have a much higher final part strength.
As a result, today's automobile manufacturers are increasingly using DUAL-TEN®steel to reduce mass, reduce cost and improve crash energy management. In addition, these advanced high-strength steels are ideal for fatigue and durability sensitive parts or thin-gauge exposed panels that are subjected to denting loads. With proper design strategy, DUAL-TEN® steels offer a great opportunity for part downgaging, body in white weight reduction, improvement of car fuel economy, and crash performance.
Product Descriptions
DUAL-TEN® Steel
DUAL-TEN® - 590/600 Steel
DUAL-TEN® - 780/800 Steel
TRIP Steels
TRIP - 590/600 Steel
TRIP - 780/800 Steel
The unique characteristics of advanced high-strength steels are developed by a continuous heat treating process that creates martensite in the steel microstructure. The amount of martensite, together with the amount of carbon, will determine the strength level of the steel. When compared to other grades, specifically high-strength, low-alloy steels, the classification for advanced high-strength steels are based on minimum tensile strength.
DUAL-TEN® (dual phase) Steels
DUAL-TEN® (dual phase) steels are quickly becoming one of the most popular and versatile materials in today's automotive industry. Currently, these steels are most commonly used in structural applications where they have replaced more conventional HSLA steels. They offer a great opportunity for part weight reduction. The improved formability, capacity to absorb crash energy, and ability to resist fatigue have driven this substitution. Today's applications include front and rear rails, crush cans, rocker reinforcements, b/c pillar reinforcements, cowl inner/outer, back panels, cross members, bumpers and door intrusion beams. Recently, DUAL-TEN® steels have gained in popularity in automotive closures.
DUAL-TEN® steels are made in the following grades. You can find more specific material property information about these grades in our online brochure or by following the links provided.
DUAL-TEN® 590/600 steel
DUAL-TEN® 780/800 steel
In general, DUAL-TEN® steel is a mixture of ferrite matrix and martensite islands decorating grain boundaries with possible addition of bainite. Formable DUAL-TEN® steels contain approximately 5% - 15% martensite. Refer to Figure - 1.
- Ferrite - soft phase, offers ductility - Martensite - hard phase, offers strength
Figure - 1: Example of DUAL-TEN® 600 steel structure, 1000x
Characteristics of DUAL-TEN® steels:
Work hardening - DUAL-TEN® steel displays a high and rapid initial work hardening rate. Even at low forming strain levels (2% - 3%), yield strength increases approximately 21-31 ksi (145-214 MPa). Refer to Figure - 2.
Yield point elongation - Tested DUAL-TEN® 590/600 and DUAL-TEN® 780 steels show no yield point elongation. Refer to Figure - 3.
Formability - Due to a higher work-hardening rate and absence of YPE, DUAL-TEN® steels behave predictably in stamping processes (i.e. resistance to necking, plastic instability and kinking).
FLD curves - For the needs of forming feasibility analysis, FLD can be approximated with sufficient accuracy by the conventional ASM-FLD calculated from n-value and thickness. Refer to Table - 1, Figure - 4 and Figure - 5.
Springback - As compared to conventional HSLA steels, springback is easier to control due to consistent behavior during stamping. Refer to Figure - 6.
Bendability - DUAL-TEN® steel has very good bendability. Refer to Figure - 7.
Bake hardening - DUAL-TEN® steels have an excellent bake hardening capacity. The increase in the yield strength resulting from typical paint baking cycle is approximately 5-10 ksi (35-70 MPa). Refer to Figure - 8 and Figure - 9.
In-part strength - DUAL-TEN® (dual phase) steels have a high ultimate tensile strength (UTS). UTS ranges from 72-175 ksi (500-1200 MPa) for available grades.
Shelf life - DUAL-TEN® steel displays no room temperature aging.
Mass reduction capability - These steels have high potential for part downgaging and weight reduction (up to 25% as compared to equivalent conventional HSLA steels).
Crash energy management - DUAL-TEN® steels have a higher yield to tensile ratio as compared to conventional HSLA steels (0.5-0.6). This results in a higher capacity to manage vehicle crash energy.
Fatigue performance - DUAL-TEN® steels have a higher fatigue strength than equivalent conventional HSLA steels.
Weldability - DUAL-TEN® steel meets automotive application weldability needs.
Figure - 2: Example of work hardening rate for DUAL-TEN® 590/600 steel: Instantaneous n-value as a function of engineering strain. Note the characteristic high n-value in the low plastic deformation range.
Return to DUAL-TEN® steel characteristics
Figure - 3: Examples of stress strain curves for DUAL-TEN® steels as compared with various grades.
Return to DUAL-TEN® steel characteristics
Table - 1: Comparison of mechanical properties for DUAL-TEN® 590 and HSLA 340 steels
Material
Yield Strength (ksi)
Tensile Strength (ksi)
YPE (%)
Elongation (%)
n-value 10%-UE
DUAL-TEN® 590
375
640
24.5
0.170
HSLA 340
378
458
2.8
30.0
0.170
Return to DUAL-TEN® steel characteristics
Figure - 4: Experimental forming limit curve for material thickness of 1.8mm. A conventional ASM FLC calculated from n-value and thickness can be used for DUAL-TEN® steel with sufficient accuracy.
Figure - 5: Experimental forming limit curve for material thickness of 1.2mm. A conventional ASM FLC calculated from n-value and thickness can be used for DUAL-TEN® steel with sufficient accuracy.
Return to DUAL-TEN® steel characteristics
Figure - 6: Springback. Results of bending under tension test. Various back tension forces at constant ratio of bending radius to material thickness, R/t = 2.14. For the top samples, back tension is 85% YS, the middle is 75% YS, and the bottom is 50% YS. Two samples are shown in the picture for each case. Note consistent geometry for DUAL-TEN® 590. Dimensional accuracy of parts made of DUAL-TEN® steel can be controlled easier due to consistent material behavior in plastic deformation.
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Figure - 7: Bendability in a free-bending test. Results of the bendability test for DUAL-TEN® 590 steel: a) inner radius close to zero, b) inner radius close to the half of the material thickness. Note material folding tendencies in the inner radius area. Bending with inner radius close to zero can be performed successfully without fracture on the outer bend line.
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Figure - 8: Bake hardening in paint baking cycle. Increase in yield strength due to bake hardening for DUAL-TEN® 590 steel at various pre-strain levels.
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Figure - 9: Combined effect of work hardening (WH) and bake hardening (BH). Yield strength of DUAL-TEN® 600 steel increases more than 260 MPa after deformation to 5% and baking in a typical paint baking cycle.
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TRIP Steels
TRIP steels are one of the newest and most exciting materials being developed by the steel industry. In relation to other advanced high-strength steels, TRIP steels exhibit better ductility at a given strength level. This enhanced formability comes from the transformation of retained austenite (ductile, high temperature phase of iron) to martensite (tough, non-equilibrium phase) during plastic deformation. In fact, the acronym “TRIP” stands for TRansformation Induced Plasticity. Because of this increased formability, TRIP steels can be used to produce more complicated parts than other high strength steels, allowing the automotive engineer more freedom in part design to optimize weight and structural performance.
Comparison of DUAL-TEN® (dual phase) steel vs. TRIP steel
DUAL-TEN® Steel
Topic Area
TRIP Steel
Ferrite-martensite
Microstructure
Ferrite-bainite-austenite
None
Yield Point Elongation
Yes
Good
Formability for strength level
Very Good
Excellent
Bake Hardening
Excellent
Good
Strain Rate Sensitivity
Excellent
Good
Fatigue
Good
OK
Weldability
More difficult than DUAL-TEN®
The characteristics of TRIP steel make it especially useful for difficult to form parts. These components can benefit from the increased strength and strain rate sensitivity that TRIP offers.
Typical Grades
Various tensile strengths from 500 MPa to 800 MPa
590/600T
780/800T
Typical Microstructure
The microstructure of unformed TRIP steel consists of varying amounts of ferrite, bainite and retained austenite depending on the strength level desired.
Characteristics of TRIP steels
Work hardening – As compared with other high-strength steels, TRIP steel displays higher work hardening rate in entire range of plastic deformation.
Yield point elongation (YPE) - Tested as delivered, TRIP steels usually show YPE; however, some grades may have no YPE.
Formability – Due to high work hardening rate, TRIP steel behaves in a stable way in stamping processes (resistance to onset necking) and displays remarkably high formability (high potential to form parts of complex geometry).
Bendability – TRIP steel demonstrates good bendability; As a result, product and process design solutions leading to springback control are easier to implement.
Bake hardening – TRIP steels have an excellent bake-hardening capacity. The increase in the yield strength in a typical paint baking cycle is approximately 10 ksi (70 MPa).
Product mass reduction capacity – TRIP steels have high potential for part downgauging and weight reduction.
Fatigue performance – TRIP steels have higher fatigue strength than equivalent conventional HSLA steels.
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