Our colleagues at JFE Steel recently provided us with a new case study based on laboratory evaluations they conducted in Japan.  The article is part of our Martensite article, but we this month, we want to highlight it in our AHSS Insights blog. 

Martensitic steel grades provide a cold formed alternative to hot formed press hardening steels. Not all product shapes can be cold formed. For those shapes where forming at ambient temperatures is possible, design and process strategies must address the springback which comes with the high strength levels, as well as eliminate the risk of delayed fracture. The potential benefits associated with cold forming include lower energy costs, reduced carbon footprint, and improved cycle times compared with hot forming processes.

Highlighting product forms achievable in cold stamping, an automotive steel Product Applications Laboratory formed a Roof Center Reinforcement from 1.4 mm CR1200Y1470T-MS using conventional cold stamping rather than roll forming, Figure 6. Using cold stamping allows for the flexibility of considering different strategies when die processing which may result in reduced springback or incorporating part features not achievable with roll forming.

Figure 4: Roof Center Reinforcement cold stamped from CR1200Y1470T-MS martensitic steel.U-1

Figure 6: Roof Center Reinforcement cold stamped from CR1200Y1470T-MS martensitic steel.U-1

 

Cold stamping of martensitic steels is not limited to simpler shapes with gentle curvature. Shown in Figure 7 is a Center Pillar Outer, cold stamped using a tailor welded blank containing CR1200Y1470T-MS and CR320Y590T-DP as the upper and lower portion steels.U-1

Figure 5: Center Pillar Outer stamped at ambient temperature from a tailor welded blank containing 1470 MPa tensile strength martensitic steel.U-1

Figure 7: Center Pillar Outer stamped at ambient temperature from a tailor welded blank containing 1470 MPa tensile strength martensitic steel.U-1

 

Another characteristic of martensitic steels is their high yield strength, which is associated with improved crash performance. In a laboratory environment, crash behavior is assessed with 3-point bending moments. A studyS-8 determined there was a correlation between sheet steel yield strength and the 3-point bending deformation of hat shaped parts. Based on a comparison of yield strength, Figure 8 shows that 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.

Figure 6: Effect of Yield Strength on Bending Moment. The right image shows the typical yield strength range of CR1030Y1300T-MS and CR1200Y1470T-MS as well as typical yield strength values of several Press Hardened Steels.S-8

Figure 8: Effect of Yield Strength on Bending Moment. The right image shows the typical yield strength range of CR1030Y1300T-MS and CR1200Y1470T-MS as well as typical yield strength values of several Press Hardened Steels.S-8

 

To read more about Martensitic steels, including its practical applications, visit the Steel Grades page here.

 

Many thanks to Toshiaki Urabe, Principal Researcher, JFE Steel, and Dr. Daniel Schaeffler, President, Engineering Quality Solutions, Inc., for providing this case study.

 

 

Related Posts
Filter by
Post Page
Joining Dissimilar Materials Resistance Welding Steel to Aluminium homepage-featured-top main-blog Blog Citations Steel Grades AHSS 1stGen AHSS Laser Welding Simulation Tube Forming
Sort by

Aluminium/Steel Using Interlayer

In order to reduce the thickness of brittle intermetallic compound (IMC) formed at Aluminium/Steel interface to

18

Aluminium/Steel Using Cover Plates

In order to reduce welding current and improve heat balance during resistance spot welding of aluminium alloy to

10

T-29

Citation: T-29. S. Tobita, T. Shinmiya, Y. Yamasaki and J. Hiramoto,

8

Conventional Rule-of-Thumb Calculations Lead to Inaccurate Press Tonnage Predictions

The rule of thumb estimates used in 1989 during my internship with an automotive stamping supplier were simple

8

Servo Press Force and Energy Considerations When Working With AHSS

Advanced High-Strength Steel (AHSS) products have significantly different forming characteristics and these

8

Improvement of Delayed Cracking in Laser Weld of AHSS and 980 3rd Gen AHSS

This article is a summary of the paper entitled, “IMPROVEMENT OF DELAYED CRACKING IN LASER WELD OF AHSS AND

8

Tube Forming

Manufacturing precision welded tubes typically involves continuous

8