SLDi. June 2016 Hitachi Metals America

Transcription

1 SLDi June 2016 Hitachi Metals America

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3 Elongation (%) 1.1 Sheet Metals Trends 70 ~ ~ ~ IF 2015~ Tensile Strength MPa Cast Iron S7 / A2 / D2 Advanced Grade / Hot Stamp AHSS use is increasing due to automotive light-weighting. Advanced die grades are needed to form AHSS. 2

4 1.2 Tool Steel Bubble Chart S7 A2 8%Cr steel SLD-i D2 3

5 2.1 Chemical Composition Grade D2 Chemical composition (wt%) C Si Mn Cr Mo V Others SLD-i Within the D2 spec (stricter) - * SLD-MAGIC Same as Same as Same as Same as Lower than Lower than Addition *Chemical composition of has a variety by steel maker 4

6 2.2 Microstructure SLD-i D2 200μm 200μm 200μm Small, dense & homogeneous carbide distribution will contribute to Small & isotropic heat treatment deformation Good galling & wear resistance Coarse & directional carbide distribution Large & anisotropic heat treatment deformation Medium galling & wear resistance Characteristics will be affected by grain direction Small & sparse carbide distribution Large heat treatment deformation Low galling & wear resistance Good toughness & machinability 5

7 Hardness 2.3 Heat Treatment Condition Tempering curve Retained austenite *Quenching:1030C (1886F) SLD-i D2 Maximum hardness at 500C (932F) temper. If γr is less than 5%, secular change risk will be minimized. Tempering temperature x 2hr x 2 times Tempering temperature x2hr x 2 times Compared to D2, SLD-i is capable of an equal or greater hardness with the same heat treatment. 500 o C (932 o F) tempering temperature maximizes SLD-i performance due to; Obtaining maximum hardness (over 60 HRC). Lowering γr below 5% (minimize secular change risk). 6

8 Dimensional Change (%) 2.4 Heat Treatment Deformation Poor Length Width Specimen size: 18Tx25Wx30L(mm) Austenitizing: 1030 o C Tempering: 500 o C 2h+2h Good SLD-i D2 Reference: Chemical composition of SLD-i is within the D2 spec Grade D2 SLD-i Chemical composition (wt%) C Si Mn Cr Mo V Within the D2 spec

9 3.1 Case Study Punch dies for burring hub bearings OD: 75mm Spec 73.86±0.01 mm SLD-i Sample mm Sample mm Sample mm Sample mm Sample mm Pass rate 100% (5/5) Pass rate of D2 10% Application Grade Coating Die life Punch dies for burring SLD-i TD coated More than 500,000 hits WITHOUT repairing D2 TD coated 10, ,000 hits with repairing 8

10 3.2 Case Study Shear Tool for 1500 MPa Material information Application Thickness Hardness Strength Failure mode of dies Cross Member Floor Panel Part 1.5 mm 52 HRC 1500 MPa Wear/Galling Application Grade Hardness Coating Die life before resharpening Shear Tool SLD-i 60~62 HRC Bare surface 75,000 ~ 100,000 cuts D2 60~62 HRC Bare surface 10,000 ~ 15,000 cuts 9

11 Wear Volume (x m 2 /N) 4.1 Wear Resistance <Conditions> Test piece Item Grade Hardness Disc Surface pressure Friction Speed Friction length Condition D2, SLD-i, SLD-Magic and 8Cr 60HRC Alumina 7.8 MPa 0.42 m/sec 377 m <Results> Increase carbide amount Decrease Wear amount Poor 3 TP ASTM G99-05 Disc D2 SLD-i 8%Cr SLD-MAGIC Good 10

12 Holding Pressure (kg f) 4.2 Galling Resistance <Conditions> Item Length of Stroke Pressing Velocity Lubricant Work Work Thickness Die surface condition Condition 60mm 60spm Rust prevention oil *delivery condition 980MPa HSS 1.4mm (No Zn plating) Clearance:5% Polished by #8000 paper (2-4μm) <Results> Bead Initiation point and direction of galling Load Punch Die Work piece 0 D2 SLD-i 8%Cr SLD-MAGIC Schematic diagram of test condition 11

13 THANK YOU