Page 46 - MetalForming February 2022 Special Automotive Issue
P. 46

 Cutting Edge
By Eren Billur, Ph.D.
Correcting Common Misconceptions
Regarding Steel Grades
   Naming based on
   SAE
 EN VDA JFS
 OEM 1 OEM 2 OEM 3
 LSS
 Mild
D
D
D
TS+D
D
D
D
 IF
 D
 D
 D
 TS+D
 D
 D
 D
 HSS
  HS-IF
 YS
 YS
 YS
 TS
 YS
 YS
 YS
 HSLA
 YS
 YS
 YS
 TS
 YS
 YS
 YS+TS
 CMn
 YS
 TS*
 -
 TS
 TS
 -
 -
 BH
 YS
 YS
 YS
 TS
 YS
 YS
 YS
 AHSS
 DP
 YS+TS
 TS
 YS+TS
 TS
 YS+TS
 TS
 YS+TS
 CP
 YS+TS
 TS
 YS+TS
 TS
 YS+TS
 TS
 YS+TS
 FB
  -
  TS
  YS+TS
  TS
  YS+TS
  TS
  YS+TS
 TRIP
YS+TS
TS
YS+TS
TS
YS+TS
TS
YS+TS
 MART
 YS+TS
 TS
 YS+TS
 TS
 YS+TS
 TS
 YS+TS
  PHS / PQS
 -
 -
 TS**
 TS
 YS+TS
 TS
 YS+TS
  3rd Gen
 DP-HD (DH)
  -
  -
  YS+TS
  -
  YS+TS
  TS
  YS+TS
 TBF (CFB)
-
-
-
-
YS+TS
TS
YS+TS
 Q&P
 -
 -
 -
 -
 YS+TS
 TS
 YS+TS
  Several misconcep- tions regarding the naming and prop- erties of sheet steels exist within the metal forming community. Here we’ll discuss several of them, because while most peo- ple around the world attempt to use equiva- lency tables to identify and compare similar grades, at the end of the day a die made in Korea with commercial-quality steel may not work prop- erly in the United King- dom with what appears to be the same steel grade. Let’s discuss why this can happen.
Table 1—Global standards and specifications each name the various steel grades differently. D, drawa- bility; YS, yield strength; TS, tensile strength.
*CMn is not included in EN 10268, but several European steelmakers use a similar naming scheme. **PHS and PQS are not included in VDA239-100 but are included in a draft standard VDA239-500.
                                           Stampers readily form
and deep draw lower-
strength steels (low-carbon
mild steels as well as inter-
stitial-free (IF) grades). These steels often are named based on their drawa- bility, a combination of r and n values and total elongation. Recently, these steels have taken on the names CR1
to CR6 by SAE, VDA and several OEMs. The higher the number the better the formability. In Europe, examples of these grades DC01 to DC07 and FeP1 to FeP6, and in Japan their names are based on their minimum tensile strength (260 or 270 MPa) and their drawability—referred to with a letter, JSC270C being the least formable and JSC260G being the most ( Table 1).
Conventional high-strength steels (HSS) include high-strength IF grades (HS-IF), bake-hardenable (BH), solid solution hardened (CMn or rephos- phorized) and high-strength low-alloy (HSLA) steels. In Europe and North America, most HSS (except for CMn) are named after yield strength, while in Japan steels are named based on tensile strength. This may be confusing, as JSC340H is similar to HC180B or SAE 180B (Table 3). All of these steels could be generically named BH180.
Advanced high-strength steels (AHSS) in some cases are referred to as multiphase steels; however, I do not endorse this definition as it excludes single-phase martensitic grades. The most recent definition of AHSS, agreed to by WorldAutoSteel members:
Martensitic and multiphase steels having a minimum specified tensile strength of at least 440 MPa.
Note that at one time the definition specified a minimum tensile strength of 590 MPa, but recently was revised to include DP440 and FB440 steels.
Among the grades defined as 1st Gen AHSS: dual-phase (DP), complex- phase (CP), ferritic-bainitic (FB), trans- formation-induced-plasticity ( TRIP), martensitic (Mart) and press- quenched/hardened steels (PHS/PQS).
2nd Gen steels include twinning induced plasticity ( TWIP), as well as austenitic stainless steels, which are
 Eren Billur is the founder of Billur Metal Form, a consulting, engineering and training company in Ankara, Turkey. He stud- ied at Baskent University and Virginia Common- wealth University, received a Ph. D. in Mechanical Engineering from The Ohio State Uni-
versity, and worked as a researcher at the Center for Precision Forming. His areas of expertise include material characterization, sheet metal forming processes and finite element simulations. He has authored/co-authored more than 20 scien- tific papers (including proceedings) and con- tributed to four books, including “Hot Stamping of Ultra High Strength Steels,” published in 2018. Eren Billur
Billur Metal Form, Founder eren@billur.com.tr
 MetalForming/February 2022
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