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Enterprise name: Zongsheng Precision Mould Co., Ltd. 

Contact: Mr. Nie 13923298099 (Wechat same number). 

Miss Jia 15820657628 (Wechat same number). 

Tel: 0757 2226 9630. 

0757 color 22269276. 

Email: 261909968@qq.com. 


Fax: 0757 2226 9631 22269276. 

Web site: en.fszongsheng.com. 

Add: no. 1, Rongye 6 road, Fengxiang industrial zone, Daliang, Shunde district, Foshan city, Guangdong province

Heat treatment Technology of plastic Mould and High quality bottle blowing Mould parts

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Heat treatment Technology of plastic Mould and High quality bottle blowing Mould parts

Release date:2019-05-14 Author: Click:

Different kinds of steel are selected as plastic moulds, their chemical composition and mechanical functions are different, so the production process is different; similarly, the heat treatment process of different types of plastic die steel is also different. 

This section mainly introduces the manufacturing process of plastic mold and the characteristics of heat treatment process. 

I. the manufacturing process of plastic moulds. 


Dies made of low carbon steel and low carbon alloy steel. 

For example, the process path of 20BZ 20CrBE 20CrMnTi steel is as follows: high quality blow bottle die blanking, forging die blank annealing, mechanical roughing, cold extrusion forming, recrystallization annealing, mechanical finishing, Carburizing, quenching, tempering, grinding and polishing.



Dies made of high alloy carburized steel. 

For example, the process of 12CrNi3A steel 12CrNi4A is as follows: blanking "forging die billet" normalizing and high temperature tempering "mechanical rough machining" high temperature tempering "finishing" Carburizing "quenching, tempering" grinding and polishing "installation. 


Quenched and tempered steel die. 

For example, the process path of 45pc40Cr steel is as follows: blanking, forging die blank, annealing, mechanical rough machining, quenching and tempering, mechanical finishing, finishing, polishing and installation. 


Dies made of carbon tool steel and alloy tool steel. 

For example, the process path of steel such as T7AZ, T10A, CrWMnMague, 9SiCr, etc., is as follows: plastic bottle embryo die blanking, forging into die blank, spheroidizing annealing, mechanical rough machining, stress relieving annealing, mechanical semi-finishing, quenching, tempering, grinding and polishing. 


Prehardened steel die. 

For example, 5NiSiCaBa3Cr2Mo (P20) and other steels. 

With regard to the direct use of bar processing, because the supply state has been pre-hardened, it can be directly processed and polished and installed. 

For those who want to be forged into billets and then processed and formed, the process path is as follows: blanking, "forging", spheroidizing annealing, planing or milling, "pre-hardening treatment (34~42HRC)", "mechanical roughing", stress relief annealing, "mechanical finishing" and "polishing" installation.


2. Heat treatment characteristics of plastic moulds. 

(1) Heat treatment characteristics of Carburized steel plastic mould. 


For plastic moulds with high hardness, high wear resistance and high toughness, Carburizing steel should be selected, and Carburizing, quenching and low temperature tempering should be used as the final heat treatment. 


For the requirement of carburized layer, the thickness of carburized layer is 0.8mm to 1.5mm, 1.3mm to 1.5mm when plastic with hard filler is limited, and 0.8~1.2mm when soft plastic is limited. 

The carbon content of the carburized layer is 0.7%-1.0%. 

If carbon and nitriding are selected, the wear resistance, corrosion resistance, oxidation resistance and anti-stickiness will be better. 


The Carburizing temperature is generally 900 ~ 920 ℃, and the medium temperature carbonitriding is 840 ~ 860 ℃ for small moulds with disorderly cavity. 

The Carburizing holding time is 5 to 10 hours, which should be selected according to the requirements of the thickness of the carburized layer. 

In the Carburizing process, it is suitable to choose the step Carburizing process, that is, in the high temperature stage (900 ~ 920 ℃), the carbon is quickly infiltrated into the surface layer of the parts, and in the middle temperature stage (820 ~ 840 ℃), the thickness of the Carburizing layer is mainly added. in this way, a uniform and reasonable gradient dispersion of carbon concentration is established in the Carburizing layer, which is convenient for direct quenching. 


The quenching process after Carburizing can be selected according to different types of steel, such as de novo heating and quenching, step-by-step Carburizing and direct quenching (such as alloy carburized steel). Direct quenching after medium-temperature carbonitriding (such as small fine dies formed by cold extrusion of industrial pure iron or low carbon steel); air-cooled quenching after Carburizing (such as large and medium-sized dies made of high alloy Carburized steel).


(2) Heat treatment of hardened steel plastic mould. 


The molds with disorderly shapes are heat treated after rough machining, and then finished. The injection mold quotation can ensure the minimum deformation during heat treatment. For fine moulds, the deformation should be less than 0.05%. 


The appearance of the plastic mold cavity is very strict, so it is necessary to ensure that the appearance of the cavity is not oxidized, decarburized, eroded, overheated and so on in the process of quenching and heating. 

It should be heated in a protective atmosphere furnace or in a salt bath furnace after severe deoxidization. if you choose a general box-type resistance furnace, the protective agent should be applied on the mold cavity surface, and the heating speed should be controlled at the same time, and a relatively gentle cooling medium should be selected during cooling. control the cooling rate to avoid deformation, cracking and scrapping in the quenching process. 

Generally, hot bath quenching is better, and pre-cooling quenching can also be selected. 


It should be tempered in time after quenching, the tempering temperature should be higher than the working temperature of the die, and the tempering time should be sufficient, depending on the die data and cross-section size, but at least above 40~60min. 

(3) Heat treatment of prehardened steel plastic mould. 


The pre-hardened steel is supplied in the pre-hardened state and generally does not need heat treatment, but sometimes it needs to be forged, and it is necessary to heat-treat the forging die billet. 


Spheroidizing annealing is generally used in the pre-heat treatment of pre-hardened steel, which is intended to eliminate forging stress, obtain uniform spherical pearlite arrangement, reduce hardness, improve plasticity, and improve the cutting function or cold extrusion function of die billet. 


The pre-hardening process of pre-hardened steel is simple, most of them choose quenching and tempering treatment, and tempered sorbite arrangement is obtained after quenching and tempering. 

The temperature scale of high temperature tempering is very wide, which can satisfy all kinds of working hardness requirements of the die. 

Because of the good hardenability of this kind of steel, oil-cooled, air-cooled or nitrate step-by-step quenching can be selected during quenching. 

Table 3 Mel 27 shows the pre-hardening process of some pre-hardened steel for reference. 

Table 3 pre-hardening process of partial prehardened steel of Mel 27. 

Steel grade heating temperature / ℃ cooling mode tempering temperature / ℃ pre-hardness HRC. 

3Cr2Mo 830-840 oil-cooled or 160-180 ℃ nitrate salt classification 580-650-28-36. 

5NiSCa 880,930 Oil cooling 550,680 30,45. 

8Cr2MnWMoVS 860m900 oil or air cooling 550m620 42x48. 

P4410 830 # 860 oil-cooled or nitrate classification 550 # 650 35 # 41. 

SM1 8300850 Oil cooling 6200660 3642Oil cooling

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Foshan Shunde Zongsheng Precision Mould Co., Ltd. 

Tel: 0757 Tel: 22269630 / 13923298099 (Mr. Nie). 

Web site: www.fszongsheng.com. 

Add: no. 1, Rongye 6 road, Fengxiang industrial zone, Daliang, Shunde district, Foshan, Guangdong

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