Shock Resistant Tool Steel
Precision Marshall’s SUPER 7 MQ® is a premium shock resistant tool steel which provides a unique combination of machinability, exceptional toughness, ease of heat treatment and minium distortion. Special melting and refining practices are utilitzed to produce a uniform product with high cleanliness and minimum
segregation. The material is tested to rigorous tool steel standards to ensure uniformity of structure and freedom from defects. Meets ASTM A-681.
Chemistry
| ELEMENT | RANGE | AIM | ELEMENT | RANGE | AIM |
|---|---|---|---|---|---|
| Carbon | .48/.55 | .50 | Chromium | 3.10/3.50 | 3.30 |
| Manganese | .60/.80 | .70 | Molybdenum | 1.30/1.55 | 1.35 |
| Phosphorus | .010 max | .005 | Silicon | .20/1.00 | .50 |
| Sulfur | .002 max | .0005 | Vanadium | .20/.30 | .25 |
| Copper | .25 max | Tungsten | .30 max | ||
| Nickel | .40 max |
Applications
SUPER 7 MQ® is suitable for use in applications requiring high impact strength such as shears, punches, blanking dies and chisels. SUPER 7 MQ®’’s superior cleanliness and soundness makes it suitable for high-hardness plastic molds and zinc die casting dies.
Annealing
Heat slowly and uniformly to 1500/1550°F and hold two hours. Cool slowly (50°F per hour max.) to 1100°F and air cool to room temperature. Hardness 229 BHN maximum.
Heat Treating
Precision Marshall’s SUPER 7 MQ® is subject to decarburization during heat treatment, so a protective atmosphere furnace or a vacuum furnace should be used.
After preheating 1200/1250°F, soak material for one half hour per inch of thickness. When material reaches this temperature, heat to 1725°F, then soak material for one half hour per inch of thickness when material is up to this temperature. Air cool or oil quench to hand warm (approximately 150°F) and temper immediately. Note: Sections over two inches thick should be interrupt oil quenched or full oil quenched to attain full hardness.
Tempering
Double temper one hour per inch of section thickness to desired harness, two hours minimum per temper. Representative hardness levels after tempering are tabulated below.
Oil quenched from 1750°F • Tempered 4 hours (Section Size — 4” x 4”)
| Tempering Temperature (°F) | Rockwell Hardness (RC) | Tempering Temperature (°F) | Rockwell Hardness (RC) |
| 400 | 56/58 | 900 | 51/53 |
| 500 | 54/56 | 1000 | 49/52 |
| 600 | 53/55 | 1100 | 46/48 |
| 700 | 52/54 | 1200 | 39/41 |
| 800 | 52/54 |
EDM
Electro-discharge machining is used in the production of various tooling. This process produces recast, rehardened and retempered layers on the EDM surface. It is recommended that SUPER 7 be stress relieved at 50°F below the final tool tempering temperature, after the EDM process, to temper the rehardened layer produced by EDM.
Condition
SUPER 7 MQ® is provided completely decarb free and stress relieved.
Finish
round oversize to typical rms 50/75, maximum 125.
Sizes
Available in standard thickness increments 1/4” thru 8”.