Skh51 Heat Treatment Made Simple Annealing Quenching Tempering Parameters That Work - China

SKH51 Heat Treatment – Complete Process Parameters For Tool Rooms And Heat Treat Shops Correct SKH51 heat treatment converts good steel into a tool that lasts.

Because this grade (equal to AISI M2, DIN 1.3343 and GB W6Mo5Cr4V2) is used in millions of tools worldwide, its treatment windows are well established — yet small mistakes still ruin more SKH51 tools than bad steel ever does.

Here are the parameters we supply with every shipment, gathered in one reference.

Stage 1 – Stress relief (before heavy machining):

- 650–700°C, hold 2 hours, slow cool in furnace

- Recommended after rough turning or milling of large sections to prevent distortion in final hardening Stage 2 – Annealing (full softening for machining):

- 850–900°C, soak, then very slow cooling at 10–20°C per hour down to 700°C

- Target hardness: HB 255 max

- Songshun delivers SKH51 fully annealed, so most customers skip this stage entirely Stage 3 – Hardening (quenching):

- Preheat slowly: first step 450–500°C, second step 850–900°C

- Austenitize at 1200–1240°C in vacuum furnace or neutral salt bath — the exact point within this window depends on the tool: drills sit at the high side, punches that need toughness sit lower

- Quench in oil, salt at 500–550°C, or gas pressure quench in vacuum Stage 4 – Tempering (the step that builds final hardness):

- Triple temper at 550–580°C, 1 hour per cycle, cooling to room temperature between cycles

- Primary hardening peak occurs here — final hardness HRC 63–65

- Never skip the third temper: retained austenite that transforms later distorts finished tools and drops edge life Common SKH51 heat treatment problems and prevention:

1 - Decarburization → use vacuum or salt bath; if using atmosphere furnaces, machine off the decarb layer fully.

2 - Overheating above 1240°C → coarse grains, brittle edges that chip; the safe margin is small, use calibrated instruments.

3 - Grinding burn after hardening → sharp wheels, generous coolant, light passes; burn martensite ruins the best heat treatment.

4 - Distortion in thin tools → hang vertically during austenitizing, temper while clamped flat if needed.

For customers without in-house equipment, Songshun offers pre-hardened SKH51 (after quench and triple temper) cut to size, ready for final grinding.

You receive a mill certificate with every shipment showing the heat chemistry (C 0.80–0.90 / Cr 3.80–4.40 / Mo 4.50–5.50 / W 5.50–6.75 / V 1.75–2.20), heat-number traceability and UT reports on forged sections above 50mm — the fingerprint you need to tune and repeat your treatment recipe.

Stock in round bar dia 3–300mm, flat bar and plate 5–300mm.

Message us your sizes for a quotation within 12 hours.

Songshun Company Website: https: //songshunsteel.

com/

Company Contact:

• Posted By: Dongguan Songshun Mould Steel Co., Ltd.

• Phone: 0086 0769 85475596

• Address: 1st Floor, No. 1, Dongda Fourth Street, Shatou Community, Chang'an Town, Dongguan , GuangDong , China

• Email:

• Website: https://songshunsteel.com/

• Business Description: Established in 2009,Songshun Steel supplies a wide range of carbon, alloy and tool steel products, including high speed tool steel, cold work tool steel, hot work tool steel, plastic mould steel, engineering steel and machine structural steel etc.
  
  After more than 10 years development and growing, Songshun Steel becomes one comprehensive special steel factory, stockist and exporter.
  
  Combined with experienced exporting team and professional technical knowledge, Songshun Steel offers both technical advice and support, as well as global professional steel solution and service.
  
  Due to satisfactory reliable quality and professional service, Songshun expands our market worldwide, such as Colombia, Chile, Spain, Turkey, Iran, Vietnam, Malaysia ,UAE, Canada, Brazil, Mexico and so on.
  
  Songshun specialized in Special Steel for almost 20 years.
  
  We can supply mold steel, high speed steel, alloy steel, free cutting steel and etc.
  
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