Aobo Steel | Global Tool Steel Supplier in China
Explore Our Range of Cold-Work Tool Steels for Precision, Durability, and Reliable Performance
Discover high-performance cold-work tool steels including D2, D3, D6, A2, O1, O2, S1, S7, 52100, and DC53. Our steels are optimized for wear resistance, high hardness, dimensional stability, and reliable heat treatment outcomes across a wide range of cold-work tooling applications.
✓Refined Microstructure | UT Grade Sep 1921-82 D/d
✓Full MTC Documentation Provided
✓Factory-Direct Pricing
D2 Tool Steel | 1.2379 | SKD11
High-carbon, high-chromium air-hardening steel rich in carbides, offering exceptional wear resistance. Features deep hardenability, high compressive strength, and excellent dimensional stability. Suitable for long-life blanking and forming dies, thread rolling, shear blades, and polishing tools.
D3 Tool Steel | 1.2080 | SKD1
High-carbon, high-chromium oil-hardened steel exhibits exceptional wear resistance and compressive strength. It features deep hardening, excellent dimensional stability, and lower toughness than D2 steel. Suitable for extreme wear applications such as brick molds, ceramic liners, laminating dies, and cold-rolling rolls.
D6 Tool Steel | 1.2436 | SKD2
High-hardness, high-carbon, high-chromium air-hardening steel. Excellent wear resistance and compressive strength (approximating D3). Air-hardening properties help minimize deformation. Suitable for punching dies, drawing dies, shearing blades, and cold-forming rolls.
A2 Tool Steel | 1.2363 | SKD12
General-purpose medium-alloy air-hardening steel offering balanced toughness and wear resistance. Features deep hardening, low distortion, and reliable heat treatment properties. Suitable for various blanking/forming dies, punches, and gauges.
O1 Tool Steel | 1.2510 | SKS3
General-purpose oil-hardening steel. Combines high surface hardness, wear resistance, and toughness. Excellent deformation resistance and machinability. Suitable for economical medium-to-short run stamping dies, punches, forming dies, shear blades, bushings, and gauges.
O2 Tool Steel | 1.2842
Manganese-based oil-quenched steel. Exhibits minimal heat treatment distortion and exceptional dimensional stability. Offers excellent wear resistance and machinability. Suitable for applications demanding strict dimensional control, such as blanking, trimming, forming dies, punches, and gauges.
S1 Tool Steel | 1.2550
Tungsten alloy Shock-resisting steel. Features high toughness and impact strength, moderate wear resistance, and hardness. Supports carburizing treatment to enhance surface hardness. Suitable for heavy-duty chisels, punches, shear blades, rivet sleeves, and various impact-resistant tools.
S7 Tool Steel | 1.2355
Air-hardening Shock-resisting steel. Offers the highest impact strength and toughness among standard tool steels. Features excellent machinability, dimensional stability, and high strength. Suitable for cold-forming punches, shear blades, heavy-duty blanking dies, and crack-resistant plastic molds.
52100 Tool Steel | 1.3505 | 100Cr6
High-carbon chromium steel. Capable of through-hardening to high hardness (up to 67 HRC). Features a fine microstructure with excellent wear resistance and fatigue life. Primarily used for bearings, it is also suitable for embossing dies, relief dies, and cold-rolling rolls.
DC53 Tool Steel
Advanced High-Strength Steel (AHSS) Specialized Die Steel. Exceptional wear and damage resistance, comparable to D2 and coated tools. Suitable for high-contact-pressure applications, capable of complete hardening or additional coating.
What Is Cold-Work Tool Steel
Within the extensive classification of tool steels, cold work tool steel is a category of steel designed for operating temperatures below 200°C (390°F). Unlike the hot-work tool steels we produce, such as H13, cold-work tool steels (e.g., D2/1.2379 or D3/1.2080) lack resistance to softening at elevated temperatures. Once operating temperatures exceed 200°C (390°F), the material matrix faces a risk of softening, leading to tool and die failure.
Classification of Cold-Work Tool Steel
Cold work tool steels are systematically categorized, primarily by the AISI (American Iron and Steel Institute) system, into three main groups based on their quenching medium and composition:
| AISI Symbol | Group Designation | Key Hardening Characteristic |
| O | Oil-Hardening Cold-Work Steels | Hardenable by oil quenching. They possess non-deforming properties and are suited for intricate shapes. Examples include O1 and O2. |
| A | Air-Hardening, Medium-Alloy Cold-Work Steels | Hardenable by air cooling (or slow gas quench), which offers the highest safety (least cracking tendency) and minimum distortion during heat treatment. Examples include A2, A7, A8, and A9. |
| D | High-Carbon, High-Chromium Cold-Work Steels | Highly alloyed steels (high hardenability, often air-hardening) offering extremely high wear and abrasion resistance due to large volumes of alloy carbides. Examples include D2, D3, and D7. |
| W | Water-Hardening Tool Steels | Plain carbon steels (or low-alloy steels) require water quenching to achieve the required hardness. They are shallow-hardening, with a hard case over a strong, rigid core in thicker sections. |
| S | Shock-Resisting Tool Steels | Designed for high toughness under impact loading; suitable for cold work applications involving high mechanical shock. Examples include S1 and S7. |
The International Standard EN ISO 4957 also classifies tool steels, with cold-work tool steels being divided into non-alloy and alloy categories.
Key Properties of Cold-Work Tool Steels
In practical applications, cold work tool steel is primarily used for high-load operations such as metal stamping, embossing, shearing, and blanking. These processes demand materials with high wear resistance, high strength, and high toughness.
- High Hardness and Strength. Cold forming typically involves forcefully shaping metal at room temperature, requiring tools and dies to withstand immense counterforces. To resist plastic deformation, cold-work tool steel must possess extremely high hardness. Typically, a hardness of 60 HRC or higher is required after heat treatment.
- High Wear Resistance. Wear resistance serves as a key indicator of tool and die durability, directly determining their performance against abrasive and adhesive wear. For customers seeking ultimate wear resistance, we recommend selecting ESR (Electroslag Remelting) grade tool steel. The ESR process significantly refines carbide particles and ensures more uniform distribution, thereby substantially extending mold service life.
- Good Toughness. Toughness refers to a material’s ability to resist chipping, cracking, or fracturing under impact loads. Toughness is typically inversely proportional to hardness. High-carbon cold-work tool steels, such as D2 and D3, exhibit high hardness but low toughness. Therefore, this characteristic must be considered during tool and die design and material selection.
- Dimensional Stability. When high precision is required for tools, the thermal stability of some tool steels becomes very important. In such cases, air-hardening steel is the material of choice.
- Machinability. Tools are generally supplied in a soft, annealed condition to facilitate shaping and machining before final hardening.
Composition and Microstructure
Cold-work tool steels contain higher carbon contents (typically 0.60% to 2.50%) than many other steels, which is fundamental to achieving high hardness. They are also alloyed with various elements to enhance specific properties:
- Chromium (Cr): A moderate carbide former that contributes significantly to wear resistance, especially in high-carbon, high-chromium types (D-series). It also improves hardenability.
- Molybdenum (Mo) and Tungsten (W): While less prevalent than in hot work or high-speed steels, they can be added to improve hardenability and contribute to wear resistance by forming hard carbides.
- Vanadium (V): Forms very hard MC-type carbides (2300-3000 HV) that significantly boost abrasive wear resistance.
- Manganese (Mn) and Silicon (Si): Contribute to hardenability and, in the case of Si, can improve machinability and resistance to decarburization.
The microstructure of hardened cold-worked tool steels primarily consists of high-carbon tempered martensite and a dispersion of various carbides.
- Carbides: The type and distribution of carbides are crucial. Chromium-rich M7C3 carbides are typical in D-series steels, providing high wear resistance. The amount of these carbides increases with higher carbon and chromium content. Lower-alloy grades like O1 have almost no carbides due to their low chromium content.
- Retained Austenite (RA): In high-carbon and high-alloy steels, some austenite may be retained after quenching. While austenite can absorb stress due to its ductility, retained austenite is undesirable as it reduces hardness and can cause dimensional instability by transforming to brittle martensite under stress, leading to cracking or chipping. Control of RA is achieved through composition, hardening temperature, and tempering temperature. Subzero treatments (cryogenic treatments) can also be applied to convert retained austenite into martensite for improved hardness, dimensional stability, and fracture toughness.
Heat Treatment
Proper heat treatment determines the final properties of cold-work tool steel. If heat treatment is improper, even high-quality base material will fail due to cracking, wear, or deformation. We supply annealed tool steel. Upon receiving the material, customers perform heat treatment during their own machining process, which includes four steps: preheating, austenitizing, quenching, and tempering.
Preheating is the process of heating the workpiece to an intermediate temperature and holding it there before raising it to the final hardening temperature. High-alloy steels typically employ two-stage preheating (650–760°C and 815–900°C). This staged heating eliminates temperature differences across the cross-section, achieving uniform heating throughout the workpiece. This measure aims to reduce thermal shock, preventing uneven stress distribution, warping, or cracking in the die core caused by rapid heating. It thereby minimizes thermal deformation and ensures dimensional stability in cold-working dies.
Austenitizing is the process of heating a workpiece to high temperatures to induce a microstructural transformation into austenite and dissolve carbides into the matrix. This process requires strict control of temperature and time parameters to ensure complete solid solution of alloy carbides for achieving the final hardness and wear resistance, while avoiding grain coarsening caused by overheating or prolonged holding. Effective control of grain size is crucial for maintaining material toughness and avoiding brittle fracture during use.
Quenching aims to rapidly cool the workpiece from the austenitizing temperature, bypassing the pearlite and bainite transformation zone, thereby obtaining a hard martensitic microstructure. For high-hardening-ability steels, high-pressure nitrogen or air cooling is commonly employed to ensure uniform cooling and minimize deformation risks; whereas low-hardening-ability steels or large-section workpieces require oil quenching to guarantee full hardness. The core of the process lies in balancing cooling rate and stress control. While ensuring martensitic transformation, the mildest quenching medium should be selected to minimize warping and cracking caused by thermal gradients.
Tempering is the reheating process immediately following quenching, designed to relieve quenching stresses and transform brittle microstructures into toughened forms. By heating the workpiece to the lower critical temperature (typically 200–540°C for cold-work steels), fine carbides precipitate, and unstable retained austenite transforms into martensite. High-alloy steels generally are double- or triple-tempered to ensure complete microstructural transformation. This process sacrifices a minimal peak hardness reduction for a substantial increase in toughness, preventing cracking while eliminating dimensional instability. This achieves a balance between wear resistance and chipping resistance.
Applications
Cold-work tool steels are widely used in diverse manufacturing operations due to their ability to withstand high pressure, impact, and abrasion at or near room temperature. Typical applications include:
- Forming: Bending dies, coining dies, cold heading dies (e.g., W1, W2), cold extrusion dies, drawing dies (for wire, bars, deep drawing).
- Shearing and Cutting: Blanking dies, shear blades (hot and cold), knives (cold work).
- Punches: General punches, piercing punches, and dies.
- Miscellaneous: Wear-resistant machine tool components, woodworking tools, measuring tools, and fasteners.
- Shock-resistant applications: S-series steels (e.g., S1, S5, S7) are used for tools that require high toughness, such as chisels, powder-pressing molds, and shear-cutting thick plates.
FAQ
Cold-work tool steels are a class of tool steels used for tooling operations at temperatures typically below 200°C (390°F), often at room temperature. They are designed to offer high hardness, mechanical strength, and wear resistance, which are achieved through specific heat treatments and the presence of coarse carbides in their microstructure.
There isn’t a single “best” steel, as the optimal choice depends on the specific application’s requirements and the balance between wear resistance and toughness. Common types include high-carbon, high-chromium steels (D-series), air-hardening steels (A-series), oil-hardening steels (O-series), and shock-resisting steels (S-series). High-speed steels (HSS) and powder metallurgy (PM) tool steels also offer excellent cold-work wear resistance.
The primary difference lies in their operating temperature ranges and optimized properties. Cold work tool steels are for applications below ~200-260°C (390-500°F) and prioritize high hardness and wear resistance. Hot-work tool steels are for applications above this temperature range (up to 800°C or 1472°F). They are characterized by high hot strength, resistance to softening at elevated temperatures (red hardness), and toughness, often with lower hardness than cold-work tool steels.
Cold working, also known as strain hardening or work hardening, is the plastic deformation of a metal at temperatures below its recrystallization temperature, typically at or near room temperature. This process causes distortions in the metal’s internal structure.
The primary purposes of cold working steel include increasing strength, hardness, and dimensional or microstructural stability, as well as improving wear resistance. It also produces a smooth, clean surface finish, achieves greater dimensional accuracy, and can improve machinability by causing chips to break more easily.
Yes, cold working directly increases steel’s hardness. As plastic deformation accumulates, the internal structure distorts, making further deformation more difficult and improving the metal’s strength and hardness.
“Cold steel” typically refers to steel that has undergone “cold working” (e.g., cold rolling or cold drawing) at room temperature, which increases its hardness and strength, provides a better surface finish, and improves dimensional control. “Regular steel” can refer to hot-rolled steel, which is processed at high temperatures, often resulting in a rougher surface, lower hardness, and higher ductility initially.
No, cold working itself does not decrease grain size; it distorts and elongates the existing grains. Grain refinement (making grains smaller) occurs during a subsequent heat-treatment process called annealing, which promotes the recrystallization of new, finer grains after cold work.
Cold-work percentage is typically calculated as the reduction in the material’s cross-sectional area or thickness. For example, a 70% thickness reduction means the material’s thickness has been reduced by 70% through cold working.
Cold working is widely used to improve a steel’s mechanical properties (like strength and hardness), achieve precise dimensions and smooth surface finishes, and enhance machinability. It is applied to processes such as cold-rolling of sheets and strips, cold-drawing of bars and wire, cold-heading, coining, and extrusion, particularly for automotive, aerospace, and general engineering components.
Cold working is performed at temperatures below the metal’s recrystallization temperature, typically at or near room temperature. Although the process itself can generate some heat from deformation, the material is generally at room temperature.
Cold working enhances mechanical properties such as strength, hardness, and yield strength, improves surface finish and dimensional accuracy, and enables better reproducibility and interchangeability of parts. It also minimizes contamination problems and can impart desirable directional properties.
Cold working is plastic deformation at temperatures where annealing doesn’t rapidly occur, leading to strain hardening, increased strength, and decreased ductility. Annealing is a heat treatment that softens metallic materials, relieves internal stresses, and restores ductility by heating and then cooling at an appropriate rate, often reversing the effects of cold working.
“Hot work” and “cold work” typically refer to the temperature at which a tool steel is designed to operate. Hot-work tool steels are for high-temperature applications (above ~200°C) that require high hardness and resistance to softening at elevated temperatures. Cold-work tool steels are for room-temperature applications, emphasizing high hardness, wear resistance, and toughness. Separately, hot working and cold working are metal-forming processes that occur above and below the recrystallization temperature, respectively.
No, cold working decreases a metal’s ductility and increases its hardness and strength. To restore ductility for further deformation, intermediate annealing is often required.
Cold working stainless steel deforms it at room temperature to increase its strength and hardness, and sometimes to induce martensite formation (especially in austenitic types), while decreasing its elongation. It generally requires higher forces than those required for cold-working carbon steels due to stainless steel’s higher work-hardening rate.
Yes, 316 is an austenitic stainless steel that can be cold worked. Austenitic stainless steels, including 316, are commonly subjected to cold working processes such as cold heading. Cold-rolling, even at sub-zero temperatures, can be used to induce martensite and increase its work-hardening rate.
Hot-work tool steels are a category of tool steels engineered explicitly for cutting or forming operations in which the workpiece or tool reaches elevated temperatures, typically above 200°C. Their primary characteristic is “hot hardness,” meaning they retain their strength and hardness at high temperatures. They also exhibit good toughness and wear resistance under hot conditions. Common examples include the AISI H-series steels.
Stainless steel refers to a family of alloy steels characterized by high corrosion resistance due to a minimum of 10.5% chromium content90…. “Cold steel” is not a type of steel, but usually refers to “cold-finished steel,” which describes carbon or alloy steels that have been processed at room temperature (cold working, turning, grinding) to achieve specific characteristics like improved dimensional accuracy, smoother surface finish, and increased strength and hardness through work hardening20…. So, stainless steel is a material composition, while “cold steel” refers to a processing method applied to various steel compositions.