S-7 Tool Steel Data Sheet

S7 is a shock-resistant air hardening tool steel, designed for high impact resistance at relatively high hardness. It offers toughness to withstand chipping and breaking, combined with high attainable hardness and good wear resistance.

Chemical Composition

Carbon

Manganese 

Chromium

Molybdenum

Vanadium

Silicon

0.55%

0.70%

3.25%

1.40%

0.25%

0.35%

Typical Applications

Heavy Impact Punches

Warm Forging/Heading Dies

Plastic Injection Molds

Shear Blades

Powder Compaction Punches

Thermal Treatments

Preheat : 1100/1250F (595/675C), equalize, 1350/1450F (775/790C), equalize.

Austenize : 1725/1775F (995/895C), 30/45 minutes at temperature.

Quench : Air, positive pressure vacuum to 150F (65C), Interrupted oil to 150F(65C). Sections over 3" thick may require oil quenching to attain full hardness.

Temper : 350/1000F (205/540C), hold 2 hours at temperature, air cool. Temper twice.

Cryogenic Treating : Refrigeration treatments may improve long term dimensional stability by transforming retained austenite. Refrigeration treatments should generally be performed after the first temper, and must be followed by a temper.

Hardness and Impact Toughness Data
Air cooled from 1775F(970C)

Tempering

Temperature

Deg F

As Quenched

300

400

500

600

700

800

900

1000

1100

 

 

Deg C

 

150

205

260

315

379

425

480

540

595

 

Hardness

HRC

59

59

57

55

54

53

53

52

51

47

Toughness

Charpy C-notch

Ft-Lbs.

---

85

125

125

115

105

105

120

150

190

 

 

Joules

---

115

169

169

155

141

141

162

203

257

Surface Treatments

Because of the low tempering temperatures normally used, S7 is not typically suitable for nitriding or similar treatments.

Annealing

A. Heat to 1550F (840C), hold 2 hours, slow cool 50F (30C)/hour maximum) to 1000F (540C), air cool.
OR
B. Heat to 1550F (840C), hold 2 hours, cool to 1400F (760C), hold 4 hours, air cool to room temperature.
Typical annealed hardness: 187/220 BHN.

Stress Relieving

Annealed Material: Heat to 1200/1250F(650/675C), hold two hours, cool in still air.
Hardened Material: Heat to 25F(15C) below original tempering temperature, hold two hours, cool in still air.

Welding

Use hot work tool steel filler material 4140 or 4150 type filler material may be satisfactory for small repairs or welds away from working surface of tool.

Annealed Material:Preheat to 400/600F(205/315C). Maintain above 400F(205C) during welding. Reanneal or temper 1400F(760C) for 4 hours after welding.

Hardened Material: Preheat to original tempering temperature (300F(150C) minimum). Maintain above 300F(150C) during welding. Cool to 150F(65C) after welding. Temper 25F(15C) below original tempering temperature. (300F(150C) Minimum)

Physical Properties

Modulus of Elasticity

Density

Thermal Conductivity´╗┐

30psix10(6)

0.283 lb/in3

16.5 BTU/hr./ft./F

(207 GPa)

(7861 kg/M3)

29 W/m/ ┬░K)

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