HOT WORKING TOOL STEELS

Transcription

1 HOT WORKING TOOL STEELS 1

2 Characteristics of YSS Hot Work Tool Steels Warm forging 56~58HRC Precision hot forging 47~56HRC High temperatrure strength, Wear resistance High speed hot forging 47~54HRC F 45 (SKD61) Toughness High performance die casting 43~53 HRC 55 3 (SKT4) General purpose hot press/forging ~48HRC 2

3 Applications and YSS grade Features YSS JIS equivalent Applications Features SKD61 Hot forging dies, Extrusion dise, Die casting dies. General-purpose hot-working tool steel used in a wide range of applications. 3 Hot forging dies, Extrusion dise. A hot-working tool steel which has improved hardenability and greater toughness than, and helps avoid cracking in hotworking press dies, high-hardened Al extrusion dies. Die casting dies, Extrusion dies. Steel for precision die casting and hot-working press die which has excellent heat crack resistance and wear resistance. Extrusion dies. Al extrusion die steel and hot-working press die steel which has better high-temperature strength and softening resistance than YXR3 Die casting dies. Hot forging dies. Hot forging dies. Die casting dies, Hot forging dies. Hot forging dies. Tool steel for large or squeeze die casting moulds with excellent heat crack resistance. Hot-working tool steel with the improved high-temperature strength and toughness of JIS-SKD7 steel. Very high-strength hot working tool steel with the improved toughness of JIS-SKD8. Has great high-temperature strength and outstanding crack resistance, and is suited for hot-working press dies requiring wear resistance and high Si-Al die-cast molds requiring erosion resistance. High-toughness matrix high speed steel. Hot forging dies, Anti-meltdown insert pin. High-toughness matrix high speed steel for hot-working tools, and excellent wear resistance and crack resistance. Can withstand high-temperature loads such as in warm-and hot-working precision forging dies. SKT4 Hammer dies. Tool steel for hammer dies. F Dies for small lot, Simple dies Holding lock. Free-cutting hot-working tool steel. 3

4 Chemical compositions of YSS hot-working tool steels Chemical composition YSS JIS equivalent C Si Mn P S Ni Cr W Mo V Co SKD High toughness die steel High-strength die steel High-strength Al extrusion die steel YXR3 F SKT4 SKD61 Free cutting High-strength and toughness die steel High-strength die steel High-strength die steel High-strength die steel Matrix high speed steel Matrix high speed steel *Harmful impurities such as S, Cu and Ni are restricted to below JIS levels using Hitachi Metals' own high-quality raw materials. 4

5 Heat Treatment Standard heat treatment conditions for YSS hot-working tool steels YXR3 F (1) Simple shape tools (2) The others, especially needs toughness Temperature (HBW) Temperature Temperature 8-87 Slow cooling 8-87 Slow cooling 8-87 Slow cooling 8-87 Slow cooling 8-87 Slow cooling 8-87 Slow cooling 8-87 Slow cooling 8-87 Slow cooling 8-88 Slow cooling 8-88 Slow cooling 7-8 Slow cooling (2) Holding time at hardening temperature Annealing Quenching Tempering 1.Holding time at hardening temperature (1) Preheating time First stage: ~5 C hardening temperature holding time x 2 Second stage: 7~8 C hardening temperature holding time x 1 But preheating can be omittted when the electrical furnaces process is used or when workpieces are mm or under in thickness or a simple shape. - Oil cooling(air cooling) - Oil cooling(air cooling) - Oil cooling(air cooling) - Oil cooling - Oil cooling(air cooling) - Oil cooling(air cooling) -11 Oil cooling -8 Oil cooling (1)11-117,(2)11-11 Oil cooling 8-11 Oil cooling 8-88 Oil cooling Delivery in prehardened condition Quenching and tempering time of YSS die steels 5-6 Air cooling 5-6 Air cooling 5-6 Air cooling 5-68 Air cooling 5-6 Air cooling 5-6 Air cooling -7 Air cooling 58-6 Air cooling 5-59 Air cooling 5- Air cooling -6 Air cooling Furnace Thickness(mm) Electrical furnace, Salt bath Holding time(min) Caution: The salt bath needs preheating. Set the Soaking time same as the holding time. 2.Holding time at tempering temperature Thickness (mm) Holding time (h)

6 Quenched and tempered hardness curve , C 1, C 1, C 55 1, C C 9 C 1, C 45 1, C 1, C , C 1, C 1, C 9 C 1,1 C 1,9 C 1, C 45 1,7 C YXR , C 1,175 C 1,1 C 1,125 C ,1 C 56 1,1 C ,1 C 8 C mm cube mm cube

7 Properties Comparison Properties Carbide (Area ratio) % A1 Point ( C) Toughness Guide for selecting die materials (example) (Charpy impact value) J/cm 2 (Tensile strength at 7 C) N/mm 2 High -temperature strength Hot forging dies General For severe forging condition Warm forging, Gear forging Precision hot forging Hot former Higher resistance to heat crack and wear (Low raising temperature by forging) (Higher wear resistance) 45 (Higher resistance to progress of crack) 3 (Higher hardness) Extrusion dies Higher resistance to softening by multiple nitriding Die casting dies Anti-meltdown Insert pin General Large die Higher resistance to deflection Higher resistance to deflection 3 (Higher hardness) General For high melting point alloy Precision die casting High resistance to heat crack

8 Properties Tensile strength at elevated temperature Tensile Strength (N/mm 2 ) Charpy impact value at room temperature 2U Charpy impact value (J/cm 2 ) 18 C 8 7 C (HV) Tempering parameter P=T (+log t) / 3 T:Temperature(k) t:time(h) Tempering parameter Charpy impact value at elevated temperature 2U Charpy impact value (J/cm 2 ) 1 (42HRC) 7 Testing temperature ( C) (44HRC) Hardenability Nitriding property 7 Half temperature time=time required for cooling from quenching temperature to (Quenching temperature+room temperature) /2 Relationship between diameter of round bar and half temperature time for the center part of the bar Oil cooling (8 C) Diameter of round bar (mm) (1,25 C) Diameter of round bar (mm) Oil cooling Air cooling Half temperature time (min) Air cooling Relationship between half temperature time and quench hardness of hot working steels Hardnes (HV) C X 9min Nitriding in salt bath Distance from surface (mm) 8

9 Properties 1.Coefficient of thermal expansion [X -6 / C] C C C 7 C Thermal conductivity [W/(m k)] C Modulus of elasticity C 6 C C 196 C C C C [GPa] C