Aobo Steel | Global Tool Steel Supplier in China
Tool Steel Heat Treatment Technical Center
Technical guidance based on established metallurgical standards and verified industry practice. Browse heat treatment guides by grade, and use the fundamentals section to reduce risks such as distortion and cracking.
Technical Source & Validation Statement
The heat treatment data and process ranges presented in this Technical Center are synthesized from established metallurgical literature, international grade standards, and long-term industry practice.
In addition to documented references, many of the process parameters reflect real-world operational feedback from tool steel users across forging, die manufacturing, and industrial production environments.
These guidelines are technically sound and consistent with mainstream industry practice. However, heat treatment performance is influenced by furnace capability, part geometry, section thickness, and process control variables. Therefore, final parameters should always be validated under actual operating conditions.
Heat Treatment Guides by Tool Steel Grade
Each card targets common search intent, such as “D2 heat treatment temperature” and “H13 tempering range.” Use the guide button for technical content, and the quote button for bulk supply inquiries.
D2 Heat Treatment (1.2379/SKD11)
Austenitized typically between 995°C and 1030°C, D2 utilizes air quenching to effect martensitic transformation and exhibits a distinct secondary hardening peak around 500°C due to the precipitation of alloy carbides.
D3 Heat Treatment (1.2080/SKD1)
Requiring austenitization between 925°C and 980°C, D3 relies on oil quenching to achieve maximum hardness, but exhibits increased susceptibility to quench cracking and distortion compared to air-hardening grades due to rapid cooling rates.
D6 Heat Treatment (1.2436/SKD2)
Alloyed with tungsten to restrict austenitic grain growth via stable carbides, D6 is typically austenitized at around 960°C and oil-quenched to ensure deep hardenability and a high-carbon martensitic matrix.
A2 Heat Treatment(1.2363/SKD12)
Austenitized between 925°C and 980°C, A2 utilizes air quenching to transform austenite to martensite, requiring tempering to eliminate retained austenite.
O1 Heat Treatment (1.2510/SKS3)
Austenitized at 790–815°C and oil-quenched, O1 develops a martensitic matrix with fine carbide dispersions upon low-temperature tempering.
O2 Heat Treatment (1.2842)
Typically austenitized at 790–815°C and oil quenched, O2 transforms to martensite with minimal distortion compared to water-hardening grades.
S1 Heat Treatment(1.2550)
Austenitized between 900°C and 955°C and oil-quenched, S1 forms a martensitic structure that often requires immediate tempering to prevent cracking.
S7 Heat Treatment(1.2355)
Austenitized at 925–955°C, S7 utilizes air quenching to achieve deep hardenability and a martensitic structure resistant to softening.
52100 Heat Treatment(1.3505/100Cr6)
Austenitized between 815°C and 860°C and oil quenched, 52100 forms a martensitic microstructure with undissolved carbides and retained austenite
H10 Heat Treatment(1.2365/SKD)
Austenitized at 995–1025°C and air quenched, H10 achieves a hardness of 53–55 HRC through martensitic transformation.
H11 Heat Treatment(1.2343/SKD)
Austenitized between 995°C and 1025°C and air quenched, H11 exhibits secondary hardening during tempering due to precipitation of vanadium carbides.
H13 Heat Treatment(1.2344/SKD61)
Austenitized between 995°C and 1040°C and air-quenched, H13 forms a martensitic structure that is often susceptible to grain-boundary carbide precipitation if cooled slowly.
H21 Heat Treatment | 1.2581 | SKD7
Austenitized between 1095°C and 1205°C, H21 is typically quenched in oil or salt to develop a martensitic matrix capable of secondary hardening.
L6 Heat Treatment | 1.2714 | SKT4
Austenitized at 815–870°C and oil quenched, L6 develops a martensitic structure with good hardenability due to nickel and chromium content.
M2 Heat Treatment | 1.3343 | SKH51
Austenitized at 1190–1230°C and quenched in oil, air, or salt, M2 exhibits secondary hardening via alloy carbide precipitation.
M35 Heat Treatment | 1.3243 | SKH55
Typically austenitized around 1200°C and quenched in oil or salt, M35 relies on cobalt for hot hardness and secondary hardening.
M42 Heat Treatment | 1.3247 | SKH59
Austenitized at 1165–1190°C and quenched in oil, air, or salt, M42 achieves high hardness (63–65 HRC) through martensitic transformation.
P20 Heat Treatment | 1.2311 | 3Cr2Mo
Austenitized at approximately 845°C and oil-quenched, P20 achieves a martensitic-bainitic structure suitable for plastic molds.
Heat Treatment Fundamentals for Tool Steels
Heat treatment is a controlled heating and cooling process that alters microstructure and properties while minimizing shape change. The process chain typically includes preheating, austenitizing, quenching, and tempering. Final results depend on the weakest link, especially furnace uniformity, part geometry, and quench severity.
Process Chain Overview
- Preheating reduces thermal shock and lowers cracking risk.
- Austenitizing dissolves carbides to enrich austenite with carbon and alloying elements.
- Quenching suppresses pearlite and bainite formation to obtain martensite.
- Tempering restores toughness and controls retained austenite behavior.
Common Risk Factors
- Distortion comes from residual stress, thermal gradients, and phase transformation volume change.
- Quench cracking increases with sharp corners, high tensile stress, and excessive quench severity.
- Retained austenite may require multiple tempering cycles or cryogenic treatment in high-alloy grades.
- Non-neutral atmospheres can cause decarburization; protective atmospheres or vacuum furnaces help.