Martensitic steel combines tensile strengths up to 1700 MPa with good ductility, making it highly efficient for both vehicle lightweighting and improved crash protection — especially in anti-intrusion zones.
When austenite iron is very rapidly quenched, the austenite is transformed into a very hard crystalline microstructure called “martensite.”
The martensitic transformation begins when the austenite reaches the martensite start temperature (Ms) and continues until the lower transformation temperature (Mt) is reached. In general, the higher the percentage of conversion to martensite, the stronger the resulting martensitic steel. These steels undergo post-quench martensitic tempering to improve their ductility, so that even MS steels with very high strength levels can be cold-formed using processes like cold-roll forming.
To produce cold-rolled martensitic steel (aka MS or MART), a cold-rolled steel strip is fed into a continuous annealing line (CAL). In the CAL, the material is annealed, water-quenched, and tempered. The austenite formed in the CAL, when rapidly quenched, is transformed into martensite. The CAL’s tempering operation provides the ultra-high strength steel with improved ductility.
Docol® martensitic grades have less than 2% alloying elements, providing good weldability.
With the highest strength of our cold-formable steels, Docol martensitic steel enables excellent lightweighting and increased crash performance:
Cold-rolled Docol 1700M steel from SSAB is an eco-friendly, pound-for-pound alternative to aluminum for lightweight components used in passive safety systems. Due to Docol martensitic steel’s ductility, critical safety components are now being fabricated using cost- and energy-efficient cold forming processes.
For example, Shape Corp. uses 3D roll-forming to create lighter, more compact, and stronger A-pillars and roof rail tubes in Docol martensitic 1700MPa. Designed for the Ford 2020 Explorer and 2020 Escape, these key safety components increase driver visibility, interior space, and air bag placement optimization.
Docol 1700 martensitic is the material of choice for ultra-high strength steel (UHSS) applications, including side impact beams, bumpers, structural components, and EV battery enclosures. Docol design specialists can provide stimulated crash performance data on several optimized 1700MPa profiles, as well as simulations for many of our other martensitic grades: Docol 900M, 1100M, 1200M, 1300M, 1400M and 1500M.
*Available upon request.
Docol® steel grades can be supplied according to OEM or VDA standards. And, in close cooperation with automotive OEMs, we often develop innovative AHSS steels that are customized for a specific car application. If we don’t list a specific grade that you need, contact our technical support for more information.
Safety engineers: Create new anti-intrusion zones (e.g., for BEV battery packs) and optimize the space utilization of existing zones (e.g., passenger compartments).
Lightweighting engineers: Leverage the extreme steel strength and aluminum-like weight of martensitic steel.
Production engineers: Use familiar cold forming operations (bending, stamping, roll-forming) and exciting new operations, like 3D roll-forming, on a UHSS steel.
Procurement officers: Realize major cost reductions — with no performance penalty — by replacing aluminum with Docol martensitic steel. (And reduce your carbon footprint at the same time.)
Sustainability officers: Lower the embedded CO2 in your materials and improve your life cycle assessment with our “future-proofed” Docol martensitic steels.
Docol electrogalvanized MS steels provide corrosion resistance using a uniform, high quality, protective coating, which can be applied as a very thin coat, if desired. Docol EG-coated martensitic grades can be readily formed and joined, with excellent resistance spot welding (RSW) properties.
Docol EZ (or ZE) martensitic automotive steels are available from SSAB in the following strengths: Docol 900M, 1100M, 1200M, 1300M, 1400M and 1500M. With SSAB’s long and extensive experience in making electrogalvanized martensitic steels, car OEMs can have any of their concerns regarding hydrogen embrittlement (HE), also known as hydrogen-induced cracking (HIC), fully addressed.
World Auto Steel points out a correlation between sheet steel yield strength and the 3-point bending deformation (crash behavior) of hat-shaped parts:
“CR1200Y1470T-MS has similar performance to hot-stamped PHS-CR1800T-MB and PHS-CR1900T-MB at the same thickness, and exceeds the frequently used PHS-CR1500T-MB. For this reason, there may be the potential to reduce costs and even weight with a cold-stamping approach, providing appropriate press, process, and die designs are used.” World Auto Steel’s Metallurgy of Martensitic Steels.
With our Trial Material Stock Center, you can get AHSS samples for most of our commercially available steels – as well as samples for our newest but not yet commercially released grades. Unique to the industry, we ship coils, sheets and custom lengths of any size. In 1 to 2 weeks, your material is ready for dispatch to anywhere in the world.
The very hard crystalline steel microstructure called “martensitic” is formed when austenite iron is very rapidly quenched, transforming austenite into martensite.
Docol martensitic steels are the highest in strength of our Docol cold-formable steel grades, which means the highest potential for weight reduction and increased performance in crash-related components.
World Auto Steel presents case studies of automotive parts applications where MS steels have replaced PHS grades for certain shaped-parts, lowering energy costs and improving cycle times. As the study points out, cold forming of martensitic steels is not limited to simpler shapes with gentle curvature. The example is a cold-stamped outer center pillar with a tailor-welded blank containing both CR1200Y1470T-MS and CR320Y590T-DP sections.
Dual phase with high formability/ductility (DH) steels are TRIP-assisted, 3rd Generation automotive steels with high global and local formability and good resistance to edge cracking. DH steel have excellent energy-absorbing properties, included reserved ductility during crash impact. DH grades are ideal for complex geometries, including cold deep drawing. DH steel's FLDs and HERs are superior to DP steels, enabling scrap reduction and more streamlined stamping.
Press hardening steels have four major advantages: they can be formed into very complex shapes, their ultimate tensile strength ranges up to 2000 MPa (290 ksi), there is little or no springback, and, with tailored tempering, you can combine “full hard zones” and “soft zones” for multi-function crash performance within a single part.
Complex phase steels have the highest — up to 100% — hole expansion ratios available from advanced high strength steels. Their high HER values provide excellent cold-forming properties for punched and stretched edges/flanges, as well as deep-drawn shapes. CP steels’ superior yield strengths are used for high crash-energy absorption, while their elevated UTS levels enable thinner walls for significant automobile weight reductions.
Dual phase automotive steels have an excellent balance of ductility, high tensile strengths, easy cold formability, and very good crash energy-absorption. Its high early-stage strain hardening (n-value) makes DP steel resistant to local necking due to strain redistribution — providing highly uniform elongation. Dual phase steel’s low yield-to-tensile-strength ratio creates high global formability for deep-drawing and high-stretching capacities — all with good weldability.
High edge ductility HSLA steel with greatly improved local formability and high hole expansion ratios – ideal for challenging auto components with complex designs on sheared stretched edges.
High strength, low alloy steels are a cost-effective choice for increasing strength-to-weight ratios when compared to conventional mild carbon steels. HSLA steels also have excellent bendability and weldability and can increase the strength and/or decrease the weight for a variety of body-in-white and chassis automotive components, including suspensions, beams, and subframes.
Ferritic-Bainitic are multi-phased steels with high hole expansion ratios and good edge stretch capabilities. FB steels are suited for cold-formed and punched flanges when lightweighting automotive components such as wheels, cross members, and other structural parts.