The material of the unlocking tool-
High-speed tool steel, high-speed tool steel is mainly used to manufacture high-efficiency cutting tools.
Due to its high red hardness, good wear resistance, high strength and other characteristics, it is also used to manufacture molds, rolls, high-temperature bearings and high-temperature springs with high performance requirements.
After heat treatment, the use hardness of high-speed tool steel can reach above HRC63, and it can still maintain high hardness at a working temperature of about 600 ℃, and its toughness, wear resistance and heat resistance are good.
The quenching temperature of high-speed steel is very high, close to the melting point. Its purpose is to dissolve more alloy carbide into the matrix, so that the steel has better secondary hardening ability.
The hardness of high-speed tool steel increases after quenching, which is the first hardening, but the higher the quenching temperature, the lower the strength and toughness after tempering.
After quenching, the tempering hardness at low temperature below 350 ℃ decreases and the tempering hardness at temperature above 350 ℃ gradually increases to 520 ~ Tempering in the range of 580 ℃ (Different chemical composition, different tempering temperature)
The second hardness peak appears and exceeds the quenching hardness, which is secondary hardening. This is an important characteristic of high speed tool steel.
The main alloying elements of annealed high-speed tool steel are Molybdenum, chromium and vanadium, and some high-speed tool steel are added with cobalt, aluminum and other elements.
This kind of steel belongs to the high carbon and high alloy steel, one of the main structure characteristics is containing a lot of carbide.
The carbide in the as-cast high-speed tool steel is eutectic carbide, which is broken into particles and distributed in the steel after hot pressure processing, which is called primary carbide;
Carbide precipitated from austenite and martensite matrix is called secondary carbide.
These carbide has a great influence on the properties of high speed tool steel, especially the secondary carbide, which has a great influence on the properties of the steel such as the grain size and the secondary hardening.
The quantity and type of carbide are related to the chemical composition of steel, while the particle size and distribution of carbide are related to the deformation of steel.
Tungsten and molybdenum are the main alloying elements of high-speed tool steel, which play an important role in secondary hardening and other properties of steel.
Chromium plays an important role in hardenability, oxidation resistance and wear resistance of steel, and also plays a certain role in secondary hardening.
Vanadium plays an important role in secondary hardening and wear resistance of steel, but reduces grindability.
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