Understand Common Steel Grades and Their Performance Characteristics in One Article
- Steel No. 45 – a high-quality carbon structural steel, is the most commonly used medium-carbon quenched and tempered steel.
Main features: Medium carbon quenched and tempered steel is most commonly used, with good comprehensive mechanical properties, low hardenability, and prone to cracking when quenched in water. Small-sized parts are suitable for quenching and tempering treatment, while large-sized parts are better treated by normalizing.
Application examples: Mainly used for manufacturing high-strength moving parts, such as turbine impellers, compressor pistons, shafts, gears, racks, worms, etc. For welded parts, preheating before welding and stress relief annealing after welding should be noted.
- Q235A (A3 steel) – the most commonly used carbon structural steel.
Main features: It has high plasticity, toughness and weldability, cold stamping performance, as well as certain strength and good cold bending performance.
Application examples: Widely used in parts and welded structures with general requirements. Such as tie rods, connecting rods, pins, shafts, screws, nuts, rings, brackets, bases, building structures, bridges, etc. where the force is not large.
Representation method:
① It is composed of “Q” + a number + a quality grade symbol + a deoxidation method symbol. The steel grade is prefixed with “Q”, representing the yield point of the steel. The number following it indicates the yield point value, with the unit being MPa. For example, Q235 represents a carbon structural steel with a yield point (σs) of 235 MPa.
② When necessary, symbols indicating quality grade and deoxidation method can be marked after the steel grade. The quality grade symbols are A, B, C and D respectively. A means no impact test, B above 20 degrees, C above 0 degrees, and D above -20 degrees. The difference between A to D lies in the different impact temperatures in their properties.
Grade Q235A does not require impact toughness tests; Grade Q235B requires impact toughness tests at room temperature (20℃); Grade Q235C requires impact toughness tests at 0℃; Grade Q235D requires impact toughness tests at -20℃.
Deoxidation method symbols: F stands for boiling steel; b stands for semi-quiet steel; Z stands for quiet steel; TZ stands for special quiet steel. Quiet steel may not be marked with a symbol, that is, both Z and TZ may not be marked. For example, Q235-AF represents grade A boiling steel.
③ Special-purpose carbon steels, such as bridge steel.
④ Q represents the yield strength of steel, and the number following it indicates the yield strength value (MPa). When necessary, the quality grade (A, B, C, D, E) and deoxidation method (F, b, Z) are marked after the number.
- 40Cr – One of the most widely used steel grades, it belongs to alloy structural steel.
Main features: After quenching and tempering treatment, it has excellent comprehensive mechanical properties, low-temperature impact toughness and low notch sensitivity. It has good hardenability. When oil-cooled, it can achieve high fatigue strength. When water-cooled, complex-shaped parts are prone to cracking.
Its cold bending plasticity is medium. After tempering or quenching and tempering, it has good machinability, but poor weldability and is prone to cracking. Preheating to 100-150℃ is required before welding. It is generally used in the quenched and tempered state and can also undergo carbon-nitrogen co-nitriding and high-frequency surface hardening treatment.
Application examples: After quenching and tempering, it is used to manufacture medium-speed and medium-load parts, such as machine tool gears, shafts, worms, splined shafts, and pin sleeves, etc. After quenching and tempering and high-frequency surface hardening, it is used to manufacture parts with high surface hardness and wear resistance, such as gears, shafts, spindles, crankshafts, mandrels, sleeves, pins, connecting rods, screws and nuts, intake valves, etc.
After quenching and medium-temperature tempering, it is used to manufacture parts subjected to heavy loads and medium-speed impacts, such as oil pump rotors, sliders, gears, spindles, and rings. After quenching and low-temperature tempering, it is used to manufacture parts subjected to heavy loads, low impacts, and high wear resistance, such as worms, spindles, shafts, and rings. After carbonitriding, it is used to manufacture large-sized transmission parts with high low-temperature impact toughness, such as shafts and gears.
- HT150 – Gray cast iron – HT150 represents gray cast iron with a tensile strength of 150 MPa.
Main features: It belongs to medium-strength cast iron parts, with good casting performance, simple process, small casting stress, and no need for artificial aging; it has certain mechanical strength and good shock absorption.
Application examples: gearboxes, machine tool beds, boxes, hydraulic cylinders, pump bodies, valve bodies, flywheels, cylinder heads, pulleys, bearing covers, etc.
- 35 – Common Materials for Various Standard Parts and Fasteners.
Main features: Moderate strength, good plasticity, high cold plasticity, and fair weldability. It can be locally upset and drawn in the cold state. It has low hardenability and is used after normalizing or quenching and tempering.
Application examples: Suitable for manufacturing small cross-section parts and parts that can withstand large loads, such as crankshafts, levers, connecting rods, hooks and rings, etc., as well as various standard parts and fasteners.
- 65Mn – a commonly used spring steel.
Main features: After heat treatment and cold drawing hardening, it has relatively high strength, certain toughness and plasticity; under the same surface condition and fully quenched state, the fatigue limit is comparable to that of alloy springs, but the hardenability is poor.
Application examples: Small-sized flat and round springs of various types, seat cushion springs, spring coils, and also can be made into spring rings, valve springs, clutch spring plates, brake springs, cold-rolled helical springs, retaining rings, etc.
- 0Cr18Ni9 – the most commonly used stainless steel (American steel grade 304, Japanese steel grade SUS304).
Properties and applications: It is the most widely used stainless heat-resistant steel, such as equipment for food processing, general chemical equipment, and equipment for nuclear energy industry.
- Cr12 – a commonly used cold working die steel (American steel grade D3, Japanese steel grade SKD1).
Properties and Applications: Cr12 steel is a widely used cold working die steel, belonging to the high-carbon and high-chromium type of ledeburitic steel. This steel has good hardenability and excellent wear resistance. Due to the high carbon content of 2.3% in Cr12 steel, it has poor impact toughness, is prone to brittle fracture, and is likely to form uneven eutectic carbides.
Cr12 steel, due to its excellent wear resistance, is widely used in the manufacturing of cold stamping dies, punches, blanking dies, cold heading dies, punches and cavities of cold extrusion dies, drill sleeves, gauges, wire drawing dies, embossing dies, threading dies, drawing dies, and cold pressing dies for powder metallurgy, etc., which are subject to relatively low impact loads but require high wear resistance.
- DC53 – a commonly used cold work die steel imported from Japan.
Properties and Applications: High-strength and high-toughness cold working die steel, with the steel grade from Daido Special Steel Co., Ltd. of Japan. After high-temperature tempering, it features high hardness, high toughness, and good wire-cutting performance. It is used for precision cold stamping dies, drawing dies, thread rolling dies, cold blanking dies, punches, etc. 10, SM45 – Common carbon plastic mold steel (Japanese steel grade S45C).
- DCCr12MoV – Wear-resistant chromium steel (domestic production).
This steel has a lower carbon content than Cr12 steel and contains Mo and V. The unevenness of carbides has been improved. Mo can reduce carbide segregation and enhance hardenability, while V can refine grains and increase toughness. This steel has high hardenability and can be fully hardened when the cross-section is below 400mm.
It can still maintain good hardness and wear resistance at 300-400℃. Compared with Cr12, it has higher toughness, less volume change during quenching, and high wear resistance and good comprehensive mechanical properties.
Therefore, various molds with large cross-sections and complex shapes that can withstand significant impacts can be manufactured, such as common drawing dies, punching dies, blanking dies, trimming dies, curling dies, wire drawing dies, cold extrusion dies, cold shearing scissors, circular saws, standard tools, measuring tools, etc.
- SKD11 – Toughness chromium steel (produced by Hitachi, Ltd., Japan).
Technically, the casting structure of the steel has been improved, and the grain size has been refined. Compared with Cr12mov, the toughness and wear resistance have been enhanced. The service life of the mold has been prolonged.
- D2 – High carbon high chromium cold work steel (Made in the USA).
It features high hardenability and quenchability, excellent wear resistance, good high-temperature oxidation resistance, good rust resistance after quenching and polishing, and minimal deformation during heat treatment. It is suitable for manufacturing various cold working dies, tools and measuring tools that require high precision and long service life, such as drawing dies, cold extrusion dies and cold shearing knives.
- SKD11 (SLD) – High-chromium steel with high toughness and no deformation. Produced by Hitachi, Ltd. of Japan.
Due to the increase of Mo and V content in the steel, the casting structure of the steel is improved, the grains are refined, and the morphology of carbides is improved. Therefore, the strength and toughness (bending strength, deflection, impact toughness, etc.) of this steel are higher than those of SKD1 and D2, and the wear resistance is also increased.
Moreover, it has higher tempering resistance. Practical tests have proved that the service life of the steel mold is longer than that of Cr12mov. It is often used to manufacture molds with high requirements, such as drawing dies and molds for grinding wheel impact.
- DC53 – High toughness high chromium steel, produced by Daido Steel Co., Ltd., Japan.
The heat treatment hardness of DC53 is higher than that of SKD11. After high-temperature tempering (520-530°C), it can reach a high hardness of 62-63HRC. In terms of strength and wear resistance, DC53 surpasses SKD11. Its toughness is twice that of SKD11. In cold working die manufacturing, DC53 rarely shows cracks and crazing, significantly enhancing its service life.
The residual stress is small. The residual stress can be reduced by high-temperature tempering. The cracks and deformations after wire cutting are suppressed. The cutting and grinding properties exceed those of SKD11. It is used for precision stamping dies, cold forging, deep drawing dies, etc.
- SKH-9 – A general-purpose high-speed steel with excellent wear resistance and high toughness. Produced by Hitachi, Ltd. of Japan, it is used in cold forging dies, wire cutters, drill bits, reamers, punches, etc.
- ASP-23 – Powder metallurgy high-speed steel, produced in Sweden. It features extremely uniform carbide distribution, excellent wear resistance, high toughness, easy machinability, and stable dimensions after heat treatment. It is suitable for various long-life cutting tools such as punches, deep drawing dies, drill jigs, milling cutters, and shearing blades.
- P20 – General purpose plastic mold steel, made in the USA. Suitable for electrical discharge machining (EDM). Delivered in pre-hardened condition HB270-300. Quenched hardness HRC52.
- 718 – High-precision large and small plastic molds, made in Sweden. Especially suitable for electrical discharge machining (EDM) operations. Delivered in pre-hardened condition with HB290-330. Quenched hardness: HRC52.
- Nak80 – High mirror finish, high precision plastic mold steel, produced by Daido Steel Co., Ltd. of Japan. Pre-hardened condition upon delivery: HB370-400. Quenched hardness: HRC52.
- S136 – Anti-corrosion and mirror-polished plastic mold, made in Sweden. Pre-hardened condition upon delivery with HB < 215. Quenched hardness HRC52.
- H13 – Commonly used die-casting molds, suitable for aluminum, zinc, magnesium and alloy die-casting, hot forging dies, and aluminum extrusion dies.
- SKD61 – Advanced die-casting mold, produced by Hitachi, Ltd. of Japan. It has a significantly longer service life than H13 due to electroslag remelting technology. It is suitable for hot forging dies and aluminum extrusion dies.
- 8407 – Advanced die-casting molds, Swedish made, hot stamping dies, aluminum extrusion dies.
- FDAC – Sulfur is added to enhance its machinability. The factory pre-hardness is 338-42HRC, allowing for direct engraving and carving without the need for quenching or tempering. It is suitable for small-batch molds, simple molds, various resin products, sliding components, mold parts with short delivery times, zipper molds, and spectacle frame molds.
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