Basics of tool steels

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Introductory Level Tutorial on Use and Application of Tool Steels

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Basics of tool steels

  1. 1. BASICS OF TOOL STEELS Types and Applications
  2. 2. <ul><li>Raymond F. Mignogna, MS, PE </li></ul><ul><li>Metallurgical Engineer </li></ul><ul><li>Email: [email_address] </li></ul><ul><li>Telephone: 352-259-2938 </li></ul><ul><li>Cell: 352-638-2072 </li></ul><ul><li>Website: www.mignogna.net </li></ul>
  3. 3. TOOL STEEL PERFORMANCE <ul><li>The Four Factors </li></ul><ul><li>Required for Successful Application </li></ul><ul><li>Tool Design </li></ul><ul><li>Accuracy of Fabrication </li></ul><ul><li>Tool Steel Selection </li></ul><ul><li>Correct Heat Treatment </li></ul>
  4. 4. TYPES OF TOOL STEEL <ul><li>High Speed Steels </li></ul><ul><ul><li>Group M – Molybdenum </li></ul></ul><ul><ul><li>Group T – Tungsten </li></ul></ul><ul><li>Hot Work Steels </li></ul><ul><ul><li>Chromium </li></ul></ul><ul><ul><li>Tungsten </li></ul></ul><ul><ul><li>Molybdenum </li></ul></ul><ul><li>Cold Work Steels </li></ul><ul><ul><li>Air Hardening </li></ul></ul><ul><ul><li>High Carbon, High Chromium </li></ul></ul><ul><ul><li>Oil Hardening </li></ul></ul>
  5. 5. TYPES OF TOOL STEEL <ul><li>Shock Resisting Steels </li></ul><ul><li>Low Alloy Special Purpose Steels </li></ul><ul><li>Mold Steels </li></ul><ul><li>Water Hardening Steels </li></ul>
  6. 6. GROUP M HIGH SPEED <ul><li>Used for High Speed Cutting Tools – Account for Over 95% Of Total Useage </li></ul><ul><li>Contain Mo, W, Cr, V, Co </li></ul><ul><li>Superior Toughness </li></ul><ul><li>Maximum Hardness Ranges from HRC 65 to HRC 70 – Depending Upon Grade </li></ul><ul><li>Type M-2 Has Best Resistance to Softening at Elevated Temperatures </li></ul>
  7. 7. GROUP T HIGH SPEED <ul><li>First Developed in Early 1900’s </li></ul><ul><li>Contain W, Cr, V </li></ul><ul><li>Extremely Deep Hardening </li></ul><ul><li>High Red Hardness (Similar to Group M) </li></ul><ul><li>High Wear Resistance </li></ul><ul><li>More Expensive Than Group M Steels </li></ul>
  8. 8. CHROMIUM HOT WORK STEELS <ul><li>H10 – H19 </li></ul><ul><li>Medium Carbon Content </li></ul><ul><li>High Toughness @ HRC 40-55 </li></ul><ul><li>Deep Hardening – up to 6” in Air </li></ul><ul><li>Low Distortion During Hardening </li></ul><ul><li>Used for Tooling at Elevated Temperatures – Same as W, Mo Grades </li></ul>
  9. 9. TUNGSTEN HOT WORK STEELS <ul><li>H21 – H26 </li></ul><ul><li>Extra Resistant to Softening </li></ul><ul><li>More Prone to Brittleness </li></ul><ul><li>Working Hardness Range is HRC 45-55 </li></ul><ul><li>Quench in Oil or Salt to Minimize Scaling </li></ul>
  10. 10. MOLYBDENUM HOT WORK STEEL <ul><li>H42 is Only Grade in Current Use </li></ul><ul><li>Low Carbon Content </li></ul><ul><li>Greater Toughness Than Tungsten Grades </li></ul><ul><li>Lower Cost </li></ul>
  11. 11. AIR HARDENING COLD WORK STEELS <ul><li>Air Harden Up To 4” Thick Sections </li></ul><ul><li>Minimum Distortion </li></ul><ul><li>Least Tendency to Crack During Hardening </li></ul><ul><li>Used for Shear Knives, Punches, Blanking/Trimming Dies, Forming Dies, Coining Dies </li></ul>
  12. 12. HIGH C, HIGH CR COLD WORK STEELS <ul><li>Group D Steels – Carbon From 1.50/2.35% </li></ul><ul><li>High Softening and Wear Resistance </li></ul><ul><li>Susceptible to Edge Brittleness </li></ul><ul><li>Dies For Long Runs – Blanking, Forming, Thread Rolling, Deep Drawing, Shear and Slitter Knives </li></ul>
  13. 13. OIL HARDENING COLD WORK STEELS <ul><li>Group O Steels </li></ul><ul><li>High Carbon Contents – 0.85-1.55% </li></ul><ul><li>Quench in Oil </li></ul><ul><li>High Wear Resistance </li></ul><ul><li>Hardness Ranges From HRC 56-62 </li></ul><ul><li>Used for Punches and Dies, Machinery Components, Gages </li></ul>
  14. 14. SHOCK RESISTING STEELS <ul><li>Group S - Medium Carbon – 0.40-0.55% </li></ul><ul><li>High Strength, Toughness </li></ul><ul><li>Good Wear Resistance at Low /Medium Temperatures </li></ul><ul><li>Used for Chisels, Rivet Sets, Driver Bits </li></ul><ul><li>Also Considered for Some Structural Applications </li></ul>
  15. 15. LOW ALLOY SPECIAL PURPOSE <ul><li>Group L – Types L2 and L6 Currently Available </li></ul><ul><li>Usually Oil Quenched </li></ul><ul><li>Can Be Water Quenched </li></ul><ul><li>L2 – Hardness – HRC 57 </li></ul><ul><li>L6 – Hardness – HRC 64 </li></ul><ul><li>Used for Machine Parts – Arbors, Cams, Chucks, Collets </li></ul>
  16. 16. MOLD STEELS <ul><li>Group P – Low Carbon Steels </li></ul><ul><li>P2 – P6 Are Carburizing Grades </li></ul><ul><li>Can Achieve Surface Hardness of HRC 58 </li></ul><ul><li>P20, P21 – Hardened to HRC 30-36 </li></ul><ul><li>Used for Low Temperature Die Casting Dies and Plastic Mold Dies </li></ul><ul><li>Electric Furnace Melted, Vacuum Degassed, Deoxidized </li></ul>
  17. 17. WATER HARDENING STEELS <ul><li>Group W – Medium to High Carbon </li></ul><ul><li>Shallow Hardening </li></ul><ul><li>Hard Case Over Tough Core </li></ul><ul><li>Used for Cold Heading, Striking, Embossing, Woodworking, Taps, Reamers, Machine Tool Components </li></ul>
  18. 18. HEAT TREATMENTS <ul><li>Most Tool Steels Require Heat Treatment After Fabrication </li></ul><ul><li>Generally Respond Best To Slow Heating Rates – Promotes Uniformity </li></ul><ul><li>Groups M, T, and H Are Exceptions </li></ul><ul><li>Quench Media Need To Be Clean and At Uniform Temperature </li></ul><ul><li>Consult Steel Suppliers For Specific Recommendations </li></ul>
  19. 19. RESOURCES <ul><li>ASM Metals Handbook – 9 th Ed., Vol. 3 </li></ul><ul><li>Tool Steels – A.I.S.I., 1978 </li></ul><ul><li>Tool Steels – Roberts & Cary; ASM, 1980 </li></ul><ul><li>Heat Treatment of Ferrous Alloys – Brooks; McGraw-Hill 1979 </li></ul><ul><li>Distortion In Tool Steels – Lement; ASM 1959 </li></ul>

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