{"id":9555,"date":"2025-08-05T15:18:22","date_gmt":"2025-08-05T07:18:22","guid":{"rendered":"https:\/\/aobosteel.com\/?page_id=9555"},"modified":"2026-03-31T15:05:46","modified_gmt":"2026-03-31T07:05:46","slug":"selection-of-steels-for-cold-extrusion","status":"publish","type":"page","link":"https:\/\/aobosteel.com\/es\/selection-of-steels-for-cold-extrusion\/","title":{"rendered":"Gu\u00eda de selecci\u00f3n de aceros para matrices de extrusi\u00f3n en fr\u00edo | Explicaci\u00f3n de los aceros D2, A2, H13 y M2"},"content":{"rendered":"\n
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Home<\/mark> <\/a>> Cold Forming & Extrusion<\/mark> <\/a> > Blanking and Piercing Dies<\/h5><\/div>\n\n\n\n

Technical Guide for Selecting Cold Extrusion Die Steels<\/h2><\/div>\n\n\n\n

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In modern manufacturing, cold extrusion is a core process for mass-producing precision components across the automotive, aerospace, and industrial machinery sectors. The service life of cold extrusion dies often directly determines a company’s profitability. Selecting the most suitable tool steel for punches and dies represents a strategic decision critical to cost-effectiveness.<\/p>\n\n\n\n

Cold extrusion, also known as cold forging or cold impact extrusion, is typically performed at temperatures below 200\u00b0C (390\u00b0F). The general process involves placing a metal blank into a fixed die cavity, where a high-speed punch forces the metal to flow plastically, ultimately achieving the desired shape.<\/p>\n\n\n\n

This process imposes extremely demanding requirements on tool and die materials. Die steel must withstand extreme compressive stresses, severe abrasive wear, and dynamic fatigue loads within an extremely short timeframe.<\/p>\n\n\n\n

General-purpose steel can no longer meet the requirements above; heat-treated tool and die steel must be used. The fundamental rationale for selecting tool and die steel is to balance high hardness with high toughness.<\/p>\n\n\n\n

The Critical Demands on Cold Extrusion Tooling<\/h2>\n\n\n\n

Cold extrusion dies face three core challenges.<\/p>\n\n\n\n

1. Extreme Pressure and Compressive Stress<\/h3>\n\n\n\n

Cold extrusion operates by inducing plastic flow in metal at room temperature. To force the metal through a specific die cavity, the die must withstand an immense counterforce. Qualified punches and dies must endure peak pressures reaching 2415 MPa (350 ksi). Under such pressure, ordinary steel deforms like clay. Compressive strength is the primary consideration for tool and die steel, ensuring the die does not undergo plastic deformation or collapse under extreme pressure.<\/p>\n\n\n\n

2. Wear Resistance<\/h3>\n\n\n\n

Under high pressure, the metal blank and die surfaces undergo intense relative sliding, resulting in abrasive and adhesive wear. Wear resistance directly determines die lifespan and the dimensional accuracy of the finished product. This is why high-carbon, high-chromium tool steels, such as the D series, are widely used in this field.<\/p>\n\n\n\n

3. Toughness and Fatigue<\/h3>\n\n\n\n

To withstand high pressure and wear, we need to increase hardness; however, excessive hardness renders steel brittle. Cold extrusion is a dynamic cyclic process. Particularly for slender punches with high length-to-diameter ratios, insufficient toughness under repeated impacts makes them highly susceptible to fatigue fracture or premature chipping.<\/p>\n\n\n\n

Key Tool Steel Categories for Cold Extrusion<\/h2>\n\n\n\n

In summary, the material selection requirements for cold extrusion processes are high hardness, high wear resistance, and sufficient toughness.<\/p>\n\n\n\n

1. High-Speed Steels (HSS)<\/h3>\n\n\n\n

High-speed steel is not only used for cutting tools; it also excels in cold-extrusion dies, particularly punches and die inserts.<\/p>\n\n\n\n

HSS exhibits exceptional hot hardness, maintaining high hardness up to 600\u00b0C. During high-speed extrusion, where instantaneous high temperatures occur, the working edges of HSS dies do not soften.<\/p>\n\n\n\n

Example: M2 steel is the standard choice for cold extrusion punches. It has a wear resistance rating of 7 and a toughness rating of 3.<\/p>\n\n\n\n

M4 steel is suitable for cold-extrusion applications that require higher wear resistance. It has a wear resistance rating of 9 and a toughness rating of 3.<\/p>\n\n\n\n

T15 steel is suitable for cold extrusion, even under higher wear-resistance requirements. It has a wear resistance rating of 9 and a toughness rating of 1. T15 offers top-tier wear resistance, but this comes at the expense of toughness. It is suitable for precision dies operating under extremely stable conditions with minimal lateral forces but experiencing severe wear.<\/p>\n\n\n\n

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\"M2<\/figure>
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M2 High Speed Steel<\/h4>\n\n\n\n

M2 high-speed steel is an ideal material for cold extrusion punches. When heat-treated to 62-64 HRC, its compressive strength can exceed 2068 MPa (300 ksi). This material exhibits exceptional wear resistance, effectively maintaining dimensional accuracy during high-volume production while resisting plastic deformation.<\/p>\n\n\n\n

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2. Cold Work Tool Steels (D- and A-Series)<\/h3>\n\n\n\n

For buyers and engineers in the cold forming field, the most common choices typically revolve around three materials: AISI D2 (1.2379), AISI A2(1.2363), and AISI O1(1.2510).<\/p>\n\n\n\n

AISI D2 (1.2379) is a high-carbon, high-chromium cold work tool steel distinguished by its exceptional wear resistance and resistance to softening. It scores 8 for wear resistance and 2 for toughness. D2 is the optimal choice for long-life, high-volume production dies. It is widely used in cold extrusion dies, punching dies, and various shearing blades.<\/p>\n\n\n\n

When D2 dies exhibit chipping or fracturing during use, AISI A2 often serves as the optimal alternative. It scores 6 for wear resistance and 5 for toughness, offering a balanced combination of these properties. A2 is a versatile cold-forming steel that retains good wear resistance and superior impact resistance compared to D2, making it suitable for slightly more demanding applications.<\/p>\n\n\n\n

AISI O1, a low-cost oil-hardening tool steel, remains in the market. It scores 4 for wear resistance and 8 for toughness. While O1’s wear resistance falls short of D2, its toughness is exceptional. If your dies primarily fail due to fracture rather than wear, or if you require a low-cost tool material, O1 offers a highly cost-effective choice.<\/p>\n\n\n\n

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\"D2<\/figure>
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D2 Cold Work Tool Steel | 1.2379 | SKD11<\/h4>\n\n\n\n

D2 cold work tool steel combines high wear resistance with exceptional compressive strength, making it an ideal choice for extrusion die inserts. This material offers a hardness of 60-62 HRC and excellent deep hardenability; its air-hardening properties effectively control heat-treatment distortion, ensuring the die maintains stable dimensional accuracy and precision tolerances throughout prolonged, high-wear production cycles.<\/p>\n\n\n\n

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\"A2<\/figure>
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A2 Cold Work Tool Steel | 1.2363 | SKD12<\/h4>\n\n\n\n

A2 air-hardening tool steel combines high toughness with wear resistance, making it an ideal choice for extrusion punches and dies. Its quenched hardness typically ranges from 56 to 58 HRC, with deep hardenability and extremely low distortion. When D2 steel exhibits brittle fracture, A2 is an excellent alternative: it withstands extremely high compressive stresses while effectively preventing chipping under heavy impact loads.<\/p>\n\n\n\n

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\"o1<\/figure>
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O1 Cold Work Tool Steel | 1.2510 | SKS3<\/h4>\n\n\n\n

O1 oil-hardening tool steel offers a cost-effective solution for small-batch cold extrusion dies. With a hardness of 58-62 HRC, it balances wear resistance and toughness, making it widely used in punch-and-die container manufacturing.<\/p>\n\n\n\n

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3. Hot Work Tool Steels (H-Series)<\/h3>\n\n\n\n

In cold extrusion die applications, hardness is crucial but not the sole factor. When dies face extremely complex stress environments or extrude high-strength steels, excessively high hardness can instead cause instantaneous brittle fracture. In such cases, a different material selection strategy is required. To achieve necessary fracture resistance while sacrificing some compressive strength, we strongly recommend using H11 or H13. These steels absorb impact energy like springs rather than shattering like glass. Medium-carbon hot work tool steels like H11\/H13 achieve a toughness rating of 9.<\/p>\n\n\n\n

H11\/H13 also serves another purpose. To prevent the shattering of expensive carbide or high-hardness tool steel inserts within the die, one or more \u201cShrink Rings\u201d made of H11 or H13 (1.2344) can be fitted around the exterior of the inserts. This configuration is termed a prestressed composite die. Leveraging thermal expansion and contraction, H11\/H13 rings are heated and fitted over the insert. Upon cooling, this creates significant inward pre-stress. This force counteracts outward tensile stress during cold extrusion, preventing insert cracking. For this application, H11\/H13 does not require extremely high hardness; heat treatment to 46-48 HRC is typically sufficient. This hardness range ensures excellent toughness and structural stability.<\/p>\n\n\n\n

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\"H11<\/figure>
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H11 Tool Steel | 1.2343 | SKD6<\/h4>\n\n\n\n

H11 chromium hot-work steel is a critical complementary material for cold extrusion dies, with its high toughness effectively preventing sudden brittle fracture of the die. This steel grade is commonly used to manufacture shrink rings and die frames with a hardness of 46 to 52 HRC. Its high ductility enables it to withstand immense burst pressures. In high-stress components that demand superior impact resistance, H11 ensures the overall structural integrity of tooling, overcoming the brittleness inherent in high-hardness materials.<\/p>\n\n\n\n

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\"H13<\/figure>
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H13 Tool Steel | 1.2344 | SKD61<\/h4>\n\n\n\n

H13 tool steel offers high toughness and ductility, making it an ideal material for manufacturing shrink rings and housings. When heat-treated to 44-48 HRC, this material effectively suppresses crack propagation under high impact loads. H13 exhibits excellent deep hardenability and maintains precise dimensional tolerances over extended periods under extremely high burst stresses.<\/p>\n\n\n\n

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 Heat Treatment and Surface Enhancement<\/h2>\n\n\n\n

Our customers have encountered this situation: dies pass hardness tests during factory inspection, yet suddenly crack shortly after machine operation begins. This is most likely due to retained austenite. During quenching, if the austenite in the steel is not fully transformed into\u00a0martensite, the remaining portion is called retained austenite. This phase is unstable and spontaneously transforms into brittle martensite during die service, especially under high stress or high-speed impact. This transformation involves volume expansion, generating immense internal stresses within the die that ultimately lead to fatigue fracture.<\/p>\n\n\n\n

For high-stress applications such as cold extrusion dies, never perform only one or two tempering cycles to save costs. The industry standard practice is triple tempering. This ensures that most of the retained austenite is successfully transformed, eliminating internal instability in the die.<\/p>\n\n\n\n

Once the base material achieves sufficient strength and toughness, we must also apply a protective layer to the die to withstand extreme wear. Nitriding is the most common surface hardening method. Through this process, an extremely hard compound layer forms on the die surface, further enhancing its wear resistance.<\/p>\n\n\n\n

Tool Component<\/td>Recommended Steel Grades (Selection Examples)<\/td>Working Hardness (HRC)<\/td>Key Property Emphasis<\/td>Supporting Components<\/td><\/tr>
Punches<\/td>T15, M4, D4, M2<\/td>60\u201366<\/td>High Compressive Strength\/Wear Resistance<\/td>Punch shank: A2, O1, S7 (56\u201358 HRC)<\/td><\/tr>
Die Inserts<\/td>T15, M4, D4, M2, D2, Carbide<\/td>58\u201366+<\/td>High Hardness\/Wear Resistance<\/td>Die holder\/Retainer Rings: H11, H13 (46\u201348 HRC)<\/td><\/tr>
Extremely Difficult Extrusion<\/td>H11\/H13 or Tungsten Carbide<\/td>46\u201362+<\/td>Toughness to resist cracking<\/td><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

FAQ<\/h2>\n\n\n\n
What properties are required for cold extrusion die steels?<\/strong>

Tool and die steel must balance high hardness with high toughness to withstand extreme compressive stresses and dynamic fatigue loads. They also require high wear resistance to endure severe abrasive wear during the process.<\/p> <\/div>

What is the best steel for cold extrusion punches?<\/strong>

M2 high-speed steel is the standard choice for punches, offering a balance of wear resistance and toughness. When heat-treated to 62-64 HRC, M2 provides exceptional compressive strength of 2068 MPa or more.<\/p> <\/div>

When should I choose A2 steel over D2 for dies?<\/strong>

Select AISI A2 (1.2363) when D2 dies exhibit chipping or brittle fracture during use. A2 offers superior impact resistance and toughness compared to D2, while maintaining good wear resistance for cold forming.<\/p> <\/div>

What steel is used for die shrink rings?<\/strong>

H11 or H13 hot work tool steels are recommended for shrink rings to prevent insert cracking. These materials absorb impact energy like springs and create inward pre-stress to counteract tensile stress during extrusion.<\/p> <\/div>

Why is compressive strength important for cold extrusion dies?<\/strong>

Compressive strength is the primary consideration, as dies must withstand peak pressures of 2415 MPa (350 ksi). High compressive strength ensures the die does not undergo plastic deformation or collapse under this immense counterforce.<\/p> <\/div>

How many tempering cycles are needed for extrusion dies?<\/strong>

Industry standards recommend triple tempering for high-stress applications like cold extrusion. This ensures retained austenite is fully transformed, eliminating internal instability that causes fatigue fracture.<\/p> <\/div>

What is a good low-cost tool steel for cold extrusion?<\/strong>

AISI O1 is a cost-effective oil-hardening steel ideal for small-batch dies or applications requiring high toughness. While its wear resistance is lower than that of D2, O1 is excellent if dies primarily fail by fracture.<\/p> <\/div> <\/div>\n\n\n\n