Alloy tool steel, hardenability hardenability and toughness, wear resistance than carbon tool steel high, according to use can be divided into cutting tools, tooling and gage steel 3. The high carbon content steel (carbon mass fractionis greater than 80%) used for the manufacture of cutting tools, measuring tool and die, this kind of steel after quenching hardness above HRC60, and have sufficient wear resistance; carbon content medium steel (mass fraction of carbon 0.35%~0.70%) used for the manufacture of hot work die, this kind of steel after quenching the hardnessslightly lower, to HRC50~55, but a good toughness.

(a) cutting tool steel

Cutting tool produced strong wear and heat in working conditions, and the vibration and shock loading certain.Cutting tool steel has high hardness, wear resistance and good toughness, red hardness. In order to ensure its highhardness, meet the needs of the formation of carbides, mass fraction of carbon steel in general in the 0.80%~1.45%.Chromium is the main alloy elements of this kind of steel, the mass fraction of 0.50%~1.70% in general, some steelcontaining tungsten, in order to improve the performance of metal cutting. This kind of tool steel with alloying elements, so the hardenability than carbon tool steel, small deformation resulting from heat treatment, with high hardness and wear resistance. Steel commonly used are steel, silicon steel and chromium tungsten steel etc..

(two) die steel

The mold can be broadly classified as mould, cold hot mold and plastic mold 3, used for forging, stamping, cutting,die casting etc.. Because of various kinds of moulds for different purposes, the work condition is complex, so the die steel, according to the mold working conditions, should have the strength, hardness, high wear resistance, enough toughness, and high hardenability, hardenability and other process performance. Because of the different purposes,the work condition is complex, so the die steel performance requirements are also different.

Cold working die includes a die, drawing die, drawing die, stamping die, thread rolling dies, thread rolling plate, Leng Dunmo and cold extrusion die. Cold working die steel, according to their manufacturing with working conditions,should have high hardness, strength, wear resistance, enough toughness, and high hardenability, hardenability and other process performance. For the purpose of alloy tool steel is usually belong to the high carbon alloy steel,carbon content was above 0.80%, chromium is an important alloying element of this kind of steel, the mass fraction is usually not more than 5%. But for some wear resistance requirement is very high, quenching after deformation is small die steel, high chromium content up to 13%, and in order to form a large number of carbide, carbon content in steel is also very high, up to 2.0%~2.3%. Cold working die steel with high carbon content, the organization mostlyhypereutectoid steel or ledeburite steel. Steel used in high carbon low alloy steel, high carbon chromium steel,chrome molybdenum steel, medium carbon chromium tungsten Bracelet steel etc..

Hot work die for hammer forging, forging, extrusion and die-casting of several main types, including hot forging die,press forging die, stamping die, hot extrusion die and metal die casting die. Hot die on the job in addition to beargreat mechanical stress, but also bear the repeatedly heated and cooled do use, caused by thermal stress. Hot work die steel should have high hardness, strength, hardness, wear resistance and toughness, but also should have thehigh temperature strength, good thermal fatigue, thermal stability and corrosion resistance, also has highhardenability, to ensure that the whole section is consistent to mechanics. For die casting die steel, also has asurface layer after repeated heating and cooling does not crack, and to the liquid metal flow impact and erosionperformance. This kind of steel is usually belongs to the medium carbon alloy steel, carbon content in the 0.30%~0.60%, which belongs to the sub eutectoid steel, there is also a part of steel as the alloy adding more (such as tungsten, molybdenum, vanadium) and become the eutectoid and hypereutectoid steel. Steel used in chromiummanganese steel, nickel chromium steel, chrome steel etc..

Plastic mould comprises a mould for thermoplastics and thermosets mould. Plastic mould steel with strength,hardness, wear resistance, thermal stability and corrosion resistance properties of certain. In addition, but also has the advantages of good manufacturability, such, as heat treatment becomes small, good processing performance,good corrosion resistance, grinding and polishing good performance, welding performance is good, high roughness,good thermal conductivity and working conditions of size and shape stability. In general, injection molding or extrusion die can be used for hot work die steel; thermosetting molding and mold requested high wear resistance,high strength can be used for cold working die steel.

(three) for measuring tool steel

Gage should has good dimensional stability, high wear resistance, high hardness and certain toughness. Therefore,gauge steel, with high hardness, stable structure, good wear resistance, and the grinding and processing properties,good heat treatment deformation small, small expansion coefficient and good corrosion resistance. This kind of steel is usually belongs to hypereutectoid steel, alloy elements added chromium, manganese, molybdenum, tungsten.Steel commonly used with chromium, chromium tungsten steel, manganese steel etc..