Graphite Dies Surface Has A Soft Spot

- May 15, 2017-

Graphite Dies Defects and prevention of graphite mould heat Treatment

1. Graphite Dies Graphite mould surface has soft spots

The surface of graphite mould has soft spots after heat-treatment, which will affect the abrasion resistance of graphite mould and reduce the service life of graphite mould.

(1) Graphite Dies Cause

1 The graphite mould has oxidized skin, rust spots and partial decarburization on the surface before heat treatment.

2 The graphite mould quenching heating, cooling quenching medium selection improper, quenching medium impurity excessive or aging.

(2) Graphite Dies Precautionary measures

1 The graphite mold should be removed before heat treatment of oxidation skin, rust spots, when the quenching heating properly protected graphite mold surface, should be used as far as possible vacuum furnace, salt bath furnace and protection atmosphere furnace heating.

2 The graphite mold quenching after heating cooling, should choose the appropriate cooling medium, for the long-term use of cooling medium to often filter, or periodically replacement.

2. Graphite Dies Graphite Mold heat treatment before the poor organization

Graphite mold final ductile tissue coarse uneven, the ball is not perfect, the organization has a mesh, ribbon and chain-like carbide, which will make graphite mold after quenching easily cracks, resulting in scrap graphite mold.

(1) Graphite Dies Cause

1 The original microstructure of graphite mould steel material has serious carbide segregation.

2 The forging process is not good, such as the forging heating temperature is too high, the deformation amount is small, the stop forging temperature is high, after forging the cooling rate is slow, so that the forging organization is coarse and has mesh, ribbon and chain-like carbide existence, so that the spheroidization annealing is difficult to eliminate.

3 The Spheroidization annealing process is not good, such as annealing temperature too high or too low, isothermal annealing time is short, can cause spherical annealing organization uneven or bad spheroidization.

(2) Graphite Dies Precautionary measures

1 generally should be based on graphite mold working conditions, production volume and the material itself to strength and toughness, as far as possible to choose good quality graphite mold steel material.

2 improve the forging process or the use of positive fire preparation heat treatment, to eliminate the raw materials mesh and chain-like carbide and carbide heterogeneity.

3 The carbide segregation of high carbon graphite mould steels which cannot be forged are serious and refined heat treatment.

4 Graphite Dies to establish the correct spherical annealing process specification for the forging dies, the tempering heat treatment and fast leveling annealing work can be used.

5 Graphite Dies reasonable furnace to ensure the uniformity of temperature in the furnace die billet.