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what are the heat treatment processes for cutting circular knives
1、 overview of the overall heat treatment processsources：k8凯发旗舰 | publishdate：2026.10.12
the heat treatment of the slitting round cutter belongs to the precision tool steel heat treatment, and the entire process generally includes raw material preparation heat treatment, rough machining quenching, tempering, and some working conditions may add deep cold treatment and stress relief tempering to the cutting tool. the goal of the entire process is to achieve appropriate hardness of the cutting edge while retaining the toughness of the substrate, reducing the risk of heat treatment deformation and cracking, and ensuring stable use of the tool under high-speed shear and repeated impact conditions. the heat treatment schemes for different materials (high-speed steel, hard alloy, alloy tool steel) vary greatly. the following mainly introduces commonly used alloy tool steel and high-speed steel round knives.
2、 preparation heat treatment
pre heat treatment is arranged after rough forging and before rough machining, commonly known as spheroidization annealing.
the forged steel has coarse grains, uneven structure, and high hardness, which is not conducive to subsequent machining such as turning and drilling. spheroidal annealing transforms the sheet-like carbides inside the steel into spherical particles through slow heating, insulation, and slow cooling with the furnace, reducing material hardness and improving cutting performance. simultaneously releasing the internal stress generated by forging, reducing the tendency for deformation in subsequent precision machining and heat treatment stages.
if the stress on some blanks is low, complete annealing can also be used to refine the grain size and achieve uniform microstructure.
3、 quenching process
quenching is the core process that determines the hardness of cutting tools, which is divided into three stages: preheating, heating and insulation, and cooling.
1. preheating
round knives belong to the category of thin disc parts, with differences in thickness. direct high-temperature heating can produce significant temperature differences, which can easily cause deformation or even cracking. generally, one or two stages of preheating are set up, with sufficient insulation at lower temperatures to make the overall temperature of the workpiece more uniform before entering the high-temperature heating zone. high speed steel cutting tools often use two-stage preheating.
2. austenitized insulation
set the heating temperature and insulation time according to the steel grade to transform the matrix structure into austenite and fully dissolve carbides into the matrix. the insulation time needs to be reasonably controlled: insufficient insulation, insufficient dissolution of carbides, and hardness after quenching that does not meet the design requirements; if the insulation time is too long, the grains will continue to grow, the toughness of the material will decrease, and the cutting tool will easily break.
3. cooling
the cooling method is selected according to the material. alloy tool steel can be oil cooled; high speed steel is commonly gas quenched by introducing high-pressure inert gas into a vacuum heat treatment furnace to achieve uniform cooling. the core of cooling is to control the cooling rate, ensuring tissue transformation while controlling the deformation of the disc-shaped circular knife.
many high-precision slitting circular knives use vacuum quenching. a vacuum environment can reduce surface oxidation and decarburization of cutting tools, ensure the quality of the cutting edge surface, reduce subsequent grinding allowance, and is suitable for products with high requirements for appearance and dimensional accuracy. salt bath quenching still has applications in some scenarios, but there are more surface cleaning processes involved.
4、 cryogenic treatment (optional process)
after quenching and cooling the workpiece to room temperature, cryogenic treatment can be added. place the workpiece in a low-temperature environment for insulation, promote further transformation of residual austenite, improve hardness and dimensional stability, and precipitate small carbides to improve wear resistance.
cryogenic treatment can reduce the dimensional changes of cutting tools during long-term use, making it suitable for high-speed cutting and precision narrow cutting circular knives. however, the process parameters need to be matched with the material, and improper cryogenic parameters can increase internal stress and increase the risk of cracking. not all cutting circular knives need to be arranged for this process.
5、 tempering process
after quenching, the internal stress of the workpiece is high and the brittleness is high, so tempering is necessary. tempering can eliminate residual stresses from quenching, adjust the ratio of hardness and toughness, stabilize the metallographic structure, and prevent spontaneous cracking of cutting tools during storage or use.
1. one tempering: basic stress relief, reducing brittleness;
2. multiple tempering: high speed steel cutting tools commonly use multiple tempering. after each tempering and insulation, cool down and then temper again to gradually decompose residual austenite and release stress.
the tempering temperature directly determines the hardness of the finished product. the hardness of the cutting edge is relatively high, and the wear resistance is better, but the toughness decreases, and it is easy to break the blade when encountering impact; low hardness and better toughness, but the wear rate of the cutting edge will accelerate. the process personnel will set the target hardness range based on the customer's cutting materials (film, non-woven fabric, paper, metal foil).
6、 subsequent stress relief treatment (optional)
after rough grinding of the cutting tool, some high-precision circular knives will undergo low-temperature stress relief tempering. grinding processing introduces grinding stress, and low-temperature stress relief can release the stress generated by grinding, avoiding dimensional drift of the finished product during use and ensuring stable cutting clearance. it is commonly used for thin and high-precision circular knives.