According to different chemical compositions, tool steel is often divided into three categories: carbon tool steel, alloy tool steel, and high speed steel (essentially high alloy tool steel). According to the use of tool steel machining , it can be divided into three categories: cutting tool steel, die steel and measuring tool steel.
- 1. Carbon tool steel: Carbon tool steel has a high carbon mass fraction between 0.65 and 1.35%, and belongs to sub-eutectoid, eutectoid or hypereutectoid steel according to its organization. After heat treatment, the surface of carbon tool steel can obtain higher hardness and wear resistance, the core has better toughness; the annealing hardness is low (not greater than HB207), and the processing performance is good. However, its red hardness is poor. When the working temperature reaches 250 ℃, the hardness and wear resistance of the steel drop sharply, the hardness drops below HRC60, and the hardenability of this type of steel is low. Larger tools cannot be hardened (the diameter of hardened in water is 15mm), and the hardness of the surface hardened layer and the central part are very different during water quenching. Make the tool easy to deform during quenching. Or the formation of cracks. In addition, the quenching temperature range is narrow, and the temperature should be strictly controlled during quenching. Prevent overheating, decarburization and deformation.
- 2. T7, T7A hypoeutectoid steel: It has good plasticity, toughness and strength, and a certain hardness, can withstand vibration and impact loads, but has poor cutting ability. Used in to manufacture tools that are not subject to impact load, and require appropriate hardness and wear resistance, and good toughness, such as forging dies, chisels, hammers, punches, metal shears, reamers, steel stamps Woodworking tools, pneumatic tools, machine tool steel tips, fitter tools, drilling tools, blunt surgical and medical appliances, etc.
- 3. T8, T8A eutectoid steel: It is easy to overheat during quenching and heating, the deformation is also large, the plasticity and strength are relatively low, it is not suitable to manufacture tools that withstand large impact, but after heat treatment, it has higher hardness and wear resistance. Used to manufacture tools whose cutting edges do not heat up during work, such as woodworking tools, pneumatic tools, fitter tools, simple molds, rivet punches, center hole punches and punches, tools for cutting steel, bearings, cutting tools, aluminum tin alloy Die-casting plates and cores, and various types of springs.
- 4. T8Mn, T8MnA eutectoid steel: with high hardenability and hardness, but low plasticity and strength. Used to manufacture woodworking tools, hand saw blades, marking tools, rivet dies, clockwork, band saw blades, circular saw blades, coal mine chisels, masonry chisels, etc.
- 5. T9, T9A hypereutectoid steel: with higher hardness, but lower plasticity and strength. It is used to manufacture various tools that require higher hardness and certain toughness, such as marking tools, rivet dies, press dies, punches, woodworking tools, agricultural machinery cutting parts, rock drilling tools, and mold shunt nails.
- 6. T10, T10A hypereutectoid steel: the grain is fine, and it will not overheat during the heating of quenching (temperature reaches 800℃), and it can still maintain the fine grain structure; there is undissolved excess carbide in the steel after quenching, so it has T8 and T8A steels have higher wear resistance, but lower toughness.
Used to make tools with cutting edges that do not heat up during work, tools with sharp edges and a little toughness that do not withstand impact loads, such as tools for machining wood, hand saws, hand wood tools, machine fines Wood tools, twist drills, drawing dies, punching dies, cold heading dies, screw cones, reamer tools, thread rolling plates, turning tools, planers, milling cutters, currency stamping dies, cold cut edges and punching dies with uniform small cross-section , Low-precision and simple-shaped pallets, fitter scrapers, hard rock drills, tools for making rivets and nails, screwdrivers, files, chisels for carving, cutters for cutting paper and tobacco leaves, etc.
- 7. T11, T11A hypereutectoid steel: It has good comprehensive mechanical properties (such as hardness, wear resistance and toughness, etc.), the grains are finer, and it is less sensitive to the growth of grains and the formation of carbide networks when heated . Used to make tools whose cutting edges do not become hot during work, such as saws, chisel knives, taps, files, scrapers, springs, gauges, reamers, die cutting tools, tobacco cutting tools, small size and no sharp cross-section Varying cold dies and woodworking tools. T12, T12A hypereutectoid steel. Due to the high carbon content. After quenching, there are still many excess carbides, so the hardness and wear resistance are high, but the toughness is low, and the quenching deformation is large. Not suitable for manufacturing tools with high cutting speed and impact load. Used to manufacture tools that are not subject to impact load, the cutting speed is not high, and the cutting edge is not hot, such as turning tools, milling cutters, drill bits, reamers, reamers, taps, die, scrapers, gauges, blades, small punch Heads, steel files, saws, clockwork, knives for cutting tobacco leaves, and cold-cutting dies and punching dies with small cross-sectional dimensions.
It is used to manufacture metal cutting tool steel that are not subject to impact loads but require extremely high hardness, such as razors, scrapers, wire drawing tools, files, carving tools, drills, and tools for hard rock processing and carving.