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The Characteristics of Plastic Mold Heat Treatment-Hot runner thermostat of the use of the scope and application scenarios
Aug 30, 2017

Hot runner thermostat of the use of the scope and application scenarios

(1) carburizing steel plastic mold heat treatment characteristics

1. For high hardness, high wear resistance and high toughness requirements of the plastic mold, to use carburizing steel to manufacture, and carburizing, quenching and low temperature tempering as the final heat treatment.


2. The requirements of the carburizing layer, the general thickness of the carburized layer of 0.8 ~ 1.5mm, when the hard material containing compressed plastic mold carburizing layer thickness requirements of 1.3 ~ 1.5mm, when the soft plastic carburizing layer Thickness of 0.8 ~ 1.2mm. The carbon content of the carburized layer is preferably from 0.7% to 1.0%. If the use of carbon, nitrogen infiltration, the wear resistance, corrosion resistance, oxidation resistance, anti-sticking even better.


3. Carburizing temperature is generally 900 ~ 920 ℃, complex cavity of small molds take 840 ~ 860 ℃ medium temperature carbonitriding. Carburizing insulation time of 5 ~ 10h, the specific thickness of the layer should be based on the requirements to choose. Carburizing process to the use of grading carburizing process is appropriate, that is, high temperature stage (900 ~ 920 ℃) to quickly penetrate the surface of carbon-based parts; medium temperature stage (820 ~ 840 ℃) to increase the thickness of the carburizing layer, Carburized layer to establish a uniform and reasonable carbon concentration gradient distribution, easy to direct quenching.


4. After carburizing the quenching process by different steel, carburizing can be used: reheating quenching; grading carburizing directly after quenching (such as alloy carburizing steel); medium temperature carbonitriding directly after quenching (such as industrial Pure iron or low carbon steel cold extrusion forming small precision molds); carburizing after air cooling quenching (such as high alloy carburizing steel manufacturing large and medium mold).


(2) heat treatment of hardened steel plastic mold

1. The shape of the more complex mold, after roughing that is heat treatment, and then finishing, in order to ensure the minimum deformation when heat treatment, for precision molds, deformation should be less than 0.05%.


2. Plastic mold cavity surface requirements are very strict, so in the quenching process to ensure that the cavity surface is not oxidized, not decarburization, no erosion, but hot and so on. Should be in the protection of the atmosphere furnace or in the strict deoxygenated salt bath after heating, if the use of ordinary box-type resistance furnace heating, should be coated on the mold surface coating agent, while controlling the heating rate, cooling should be selected more moderate Cooling medium, control the cooling rate, in order to avoid deformation in the quenching process, cracking and scrapped. Generally hot bath quenching is better, can also be used pre-cold quenching way.


3. After quenching should be timely tempering, tempering temperature is higher than the mold working temperature, tempering time should be sufficient, depending on the length of mold material and section size, but at least 40 ~ 60min or more.

(3) pre-hardened steel mold heat treatment


1. Pre-hard steel is pre-hard supply, generally do not need heat treatment, but sometimes need to change forging, after the forging of the mold blank must be heat treatment.


2. Pre-heat treatment of pre-hardened steel is usually carried out by ball annealing, the purpose is to eliminate the forging stress, to obtain uniform spherical pearlite structure, reduce hardness, improve plasticity, improve the die blank cutting performance or cold extrusion performance.


3. Pre-hardened steel pre-hardening process is simple, most of the use of quenched and tempered, quenched and tempered after the sorbite body. High temperature tempering temperature range is wide enough to meet the mold's various hardness requirements. As a result of this kind of steel good hardenability, quenching can be used oil cooling, air cooling or nitrate salt quenching.

(4) aging hardening steel plastic mold heat treatment


1. Time hardening steel heat treatment process in two steps basic process. First, the solution treatment, that is, the steel heated to high temperature, so that a variety of alloying elements into the austenite, the completion of austenite after quenching martensite. The second step of the aging treatment, the use of aging to achieve the final requirements of the mechanical properties.


2. Solution treatment Heating in the salt bath furnace, box furnace, the heating time are desirable: 1min / mm, 2 ~ 2.5min / mm, quenching with oil cold, good hardenability of steel can also be air-cooled. If the forging die can accurately control the final forging temperature, forging directly after the solution quenching.


3. The aging treatment is best carried out in a vacuum furnace, if carried out in the box furnace, for the anti-cavity surface oxidation, the furnace must pass into the protective atmosphere, or with alumina powder, graphite powder, cast iron, Under the conditions of protection. Boxing protection should be appropriate to extend the heating time, otherwise it is difficult to achieve aging effect.



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