IGraphite mouldThere are soft spots on the surface after heat treatment, which will affect the abrasion resistance of the graphite mold and reduce the service life of the graphite mold.

The causes are as follows:

(1) before heat treatment, the surface of graphite mold has oxide scale, rust spots and local decarburization.
(2) after the graphite mold is quenched and heated, the cooling quenching medium is improperly selected, and there are too many impurities or aging in the quenching medium.

2 elements of preventive measures

(1) before heat treatment of graphite mould, oxide scale and rust spots shall be removed. The surface of graphite mould shall be properly protected during quenching and heating. Vacuum electric furnace, salt bath furnace and protective atmosphere furnace shall be used for heating as far as possible.
(2) when the graphite mold is cooled after quenching and heating, appropriate cooling medium shall be selected. The cooling medium used for a long time shall be filtered or replaced regularly.

2、 The crack of graphite mold after quenching is the biggest defect in the heat treatment process of graphite mold, which will scrap the processed graphite mold and cause great losses in production and economy.

Electronic sintered graphite mould

The causes are as follows:

(1) the graphite mold material has serious network carbide segregation.
(2) there is machining or cold plastic deformation stress in the graphite mold.
(3) improper heat treatment operation of graphite mold (heating or cooling too fast, improper selection of quenching cooling medium, too low cooling temperature, too long cooling time, etc.).
(4) the graphite mold is complex in shape, uneven in thickness, with sharp corners and threaded holes, resulting in excessive thermal stress and structural stress.
(5) the quenching and heating temperature of graphite mold is too high to cause overheating or overburning.
(6) the tempering of graphite mold after quenching is not timely or the tempering holding time is insufficient.
　　（7）Graphite mouldWhen the repair quenching is heated, it is heated and quenched again without intermediate annealing.
(8) improper grinding process for heat treatment of graphite mold.
(9) there are high tensile stress and micro cracks in the hardened layer of graphite mold during EDM after heat treatment.

10 elements of preventive measures

(1) strictly control the internal quality of graphite mold raw materials
(2) improve forging and spheroidizing annealing process, eliminate network, band and chain carbides, and improve the uniformity of spheroidizing structure
(3) the graphite mold after machining or cold plastic deformation shall be stress relieved annealed (& gt; 600 ℃) and then heat quenched.
(4) for graphite molds with complex shapes, asbestos shall be used to plug threaded holes, wrap dangerous sections and thin walls, and adopt graded quenching or isothermal quenching.
(5) when repairing or renovating graphite molds, annealing or high-temperature tempering is required.
(6) graphite mold shall be preheated during quenching and heating, and precooled during cooling, and appropriate quenching medium shall be selected.
(7) the quenching heating temperature and time shall be strictly controlled to prevent overheating and Overburning of graphite molds.
　（8）Sintered graphite mouldTempering shall be conducted in time after quenching, and the holding time shall be sufficient. High alloy and complex graphite molds shall be tempered for 2-3 times.
  & nbsp; (9) Select correct grinding process and suitable grinding wheel.
(10) improve the EDM process of graphite mold and conduct stress relief tempering.