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Three ways to change the properties of mold steel
- Jul 30, 2018 -

Definition of steel】Steel is an iron-carbon alloy containing carbon in the range of 0.0218%-2.11%. An alloy steel is obtained by adding an alloy component such as Cr, Mo, V, or Ni to a common steel material. Our mold steels are all alloy steel. Mold steels are also basic material for paper cutting knife, shear blade, wood cutting knife.


The three ways to change the properties of a mold steel to get better performance of the machine knife:


1. Change the composition of the alloy


(1) Carbon: C


Function: increase the hardness of the quenched structure; form carbides, improve wear resistance; reduce toughness; reduce weldability.


(2) Chromium: Cr


Function: Improve the hardness of steel, form hard and stable chromium carbide to improve wear resistance; improve the hardenability of steel; when Cr content exceeds 12%, it has corrosion resistance and provides good throwing light.


(3) Molybdenum: Mo


Function: Mo is a strong carbide forming element to improve wear resistance; when Mo>0.5%, it can suppress the temper brittleness caused by other alloying elements; provide red hardness, heat strength; improve hardenability and tempering stability.


(4) Vanadium: V


Function: It can form high hardness carbide, improve wear resistance; refine steel grain, reduce superheat sensitivity; improve steel strength, toughness and tempering stability.


(5) Nickel: Ni


Function: Ni can improve the hardenability of steel; Ni can refine grains.


(6) Sulfur: S


Function: It is often present in the form of MnS in steel, which cuts the continuity of the matrix and deteriorates the toughness, corrosion resistance, throwing light, electrical discharge processability and etch resistance of the material, which can improve the cutting ability of the material.


2. Improve the smelting process


(1) Ordinary steelmaking process


(2) Electroslag remelting (ESR) smelting


The crude steel billet is placed in the electroslag furnace, and a high current is applied to make the electric furnace generate a high temperature, so that the crude steel billet is melted into molten steel, the molten steel flows through the electroslag, and the impurities are filtered and adsorbed by the electroslag, thereby achieving the purification effect. The overall remelting speed is fast, but some very fine impurities are not removed.


(3) Vacuum arc remelting (VAR)


In the vacuum furnace, a strong current is applied to the steel embryo, the bottom of the steel embryo begins to melt, and the impurities are vaporized into a gas to be pumped away, thereby improving the purity of the steel. Moreover, it is solidified bit by bit, the solidification speed is very fast, and the structure is changed. Very dense. The characteristic is that the impurities go thoroughly, but the overall remelting speed is slow.


3. Using heat treatment


The heat treatment of steel refers to the process of changing the properties of steel by heating and then cooling, by controlling the heating temperature, holding time and cooling rate of the steel to meet the processing or use requirements.


The main heat treatment processes are: annealing, normalizing, quenching and tempering