There are three main ways to change the properties of die steel steel:Alloy composition、Smelting process、Heat treatment
There are three main ways to change the properties of die steel steel:
1、Alloy composition
Carbon: C
Increase the hardness of quenched tissue;
Forming carbide to improve wear resistance;
Reduced toughness;
Reduce weldability
Cr: Cr
Increase the hardness of steel, forming hard and stable chromium carbide, thus improving wear resistance;
Can improve the hardenability of steel;
When Cr content exceeds 12%, it is resistant to corrosion and provides good optical rotation
Mo, Mo
Mo is a strong carbide forming element to improve wear resistance.
Mo b b 0 0.5% can restrain the tempering brittleness caused by other alloy elements.
Provide red hardness, thermal intensity;
Increase the hardenability, temper stability
V: V
High hardness carbides can be formed to improve wear resistance.
Fine steel grain, reduce the sensitivity of overheating
Improve the strength, toughness and tempering stability of steel
Nickel: Ni
Ni can increase the hardenability of die steel;
Ni refines grains
Sulfur (S)
Often exists in steel in the form of MnS, breaks the continuity of matrix, deteriorates the material’s toughness, corrosion resistance, optical rotation, discharge processing, etch, can improve the cutting ability of the material.
2、Smelting process
Common steelmaking process
(1) electroslag remelting (ESR)
The thick billet is placed in the electroslag furnace, and a strong current is put into the furnace to produce a very high temperature, so that the thick billet is melted into molten steel, and the molten steel flows through the electroslag, and the impurities are filtered and absorbed by the electroslag, so as to achieve the purification effect.The overall remelting is fast, but some very fine impurities are not removed.
(2) vacuum arc remelting (VAR)
In a vacuum furnace, a strong electric current is applied to the steel shell. The bottom of the steel shell begins to melt, and the impurities are vaporized into gas and pumped away, thus improving the purity of the steel.It is characterized by thorough removal of impurities but slow overall remelting.
3、Heat treatment
The heat treatment of die steel refers to the process of heating and then cooling, by controlling the heating temperature, holding time and cooling speed of steel to change the properties of steel, in order to meet the requirements of processing or use.The main heat treatment processes are: annealing, quenching, tempering.
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