Defects and Prevention of Heat Treatment of Expandable Graphite Mold
In recent years, the expansion of graphite mold with its excellent characteristics of the impact of mold market, becoming the darling of the mold industry. The following Cobo Wei expansible graphite products manufacturers to talk about the expansion of graphite mold heat treatment in the existence of defects and prevention methods.
1, Expandable Graphite mold surface with soft spots
Expandable Graphite mold heat treatment after the surface of a soft point, will affect the wearability of Expandable Graphite mold, reducing the life of Expandable Graphite mold.
1) Expandable Graphite mold in the heat treatment before the surface of the scale, rust and local decarburization.
2) Expandable Graphite mold quenching after heating, cooling quenching medium selection improper, quenching medium impurities or too much.
(2) Precautionary measures
1) Expandable Graphite mold heat treatment should be removed before the scale, rust, in the quenching and heating appropriate protection of the surface of the expansive graphite mold, should try to use vacuum furnace, salt bath furnace and protective atmosphere furnace heating.
2) Expandable Graphite mold quenching After cooling, should choose the appropriate cooling medium, long-term use of the cooling medium to be frequently filtered, or regularly replaced.
2, Expandable Graphite mold heat treatment before the poor organization
Expandable Graphite mold The final spheroidized tissue is roughly uneven, the ball is not perfect, the organization has mesh, ribbon and chain carbide, which will make the expansion of graphite mold after quenching easy to produce cracks, resulting in expansible graphite mold scrapped The
1) Expandable Graphite Die Steel Material Original organization with severe carbide segregation.
2) Forging process is poor, such as forging heating temperature is too high, the deformation is small, the forging temperature is high, forging the cooling speed is slow, so that forging tissue thick and reticulate, ribbon and chain carbide exists, the ball It is difficult to eliminate when annealing.
3) ball annealing process is poor, such as the annealing temperature is too high or too low, isothermal annealing time is short, can cause spheroidized annealing uneven or spheroidized.
(2) Precautionary measures
1) should generally be based on the working conditions of the expansive graphite mold, the production batch and the material itself, the strength and toughness performance, try to choose a good quality expansive graphite mold steel material.
2) to improve the forging process or the use of normalizing heat treatment to eliminate the raw materials in the network and chain carbide and carbide nonuniformity.
3) can not be forged carbide segregation serious high carbon expansible graphite die steel can be solid solution heat treatment.
4) for the forging of the blank after the development of the correct ball annealing process specifications, can be used quenched and tempered heat treatment and rapid uniform fine ball annealing.
5) reasonable furnace, to ensure that the furnace mold temperature uniformity.
3, Expandable Graphite mold quenching crack
Expandable Graphite mold after quenching is the largest flaw in the process of heat treatment of Expandable Graphite mold, will make the processing of a good expansible graphite mold scrapped, so that the production and the economy caused great losses.
(1) the cause of the occurrence
1) Expandable Graphite mold material has a serious mesh carbide segregation.
2) There are mechanical or cold plastic deformation stresses in the Expandable Graphite mold.
3) Improper heat treatment of Expandable Graphite molds (improper heating or cooling, improper selection of quenching and cooling medium, low cooling temperature, too long cooling time, etc.).
4) Expandable Graphite mold shape complex, uneven thickness, with sharp corners and threaded holes, so that thermal stress and tissue stress is too large.
5) Expandable Graphite mold quenching Heating temperature is too high to produce overheating or overheating.
6) Expandable Graphite mold quenching after tempering is not timely or tempering insulation time is insufficient.
7) Expandable Graphite mold rework quenching and heating, without intermediate annealing and heating again quenching.