Vacuum Heat Treatment of Cross Groove Fine Punching Die

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The screw cross groove fine punching die has to bear a lot of high-frequency repeated impact, compression and bending stress in the production and use. The main failure mode is the early fracture or fatigue fracture of the cross groove bar, and the case of wear failure is rare. Therefore, the cross groove fine punch has high requirements on strength and toughness. The original use of salt bath furnace quenching, its service life is only about 10,000 times, or even lower. In recent years, the use of vacuum furnace quenching has doubled the service life, generally reaching 40,000 to 50,000 times, and the highest has reached about 180,000 times.

Technical requirements:

(1) The hardness is 58~62HRC, preferably 61~62HRC. Due to low hardness (58~60HRC), it is prone to wear failure and high hardness (63~64HRC), which is prone to chipping and early breakage.

(2) No tiny cracks, knocked edges, decarburization and other surface defects are allowed.

(3) In order to reduce surface defects, grinding and polishing should be carried out.

Process flow:

Blanking-annealing-roughing-cold extrusion-grinding-polishing-heat treatment quenching-aging-overall polishing-rust-proof treatment-general inspection-warehousing.

Heat treatment process: annealing process ① Box protection (charcoal + cast iron chips), divided into three boxes, loaded into RJX-45-9 box furnace. ②Low temperature furnace (400℃) or below. Since the cross groove fine punching die is formed by cold extrusion, the hardness after annealing is required to be less than 95HRB. ③The cooling rate should be strictly controlled in the cooling stage with the furnace, and the rate should not be higher than 30℃ per hour

Quenching process

①Drying Dry the material basket fixture. ②Clean the cross groove fine punching die with gasoline, dry it naturally and install it in the furnace. ③ Load the furnace and place the dies evenly in the material basket, separated by layers of metal mesh. Each layer of the material basket can put 200 pieces, and the three layers can hold about 600 pieces. ④Preheating Vacuum heating is radiation heating, and the temperature of the workpiece lags behind the temperature indicated by the instrument, so two-stage preheating is adopted. After the die enters the heating chamber, the vacuum is started. When the vacuum degree reaches 6.67Pa, it can be heated by electricity. The preheating temperature of the first stage is 580 °C, and the holding time is 60 minutes, and the preheating temperature of the second stage is 850 °C, and the holding time is 50 minutes. ⑤ Heating and quenching The heating temperature is 1210℃, and the holding time is 40min. In order to prevent die sticking and evaporation of alloy elements, the heating chamber should be filled with 99.995% high-purity nitrogen of 1*103Pa after reaching the temperature. ⑥The cooling adopts ZZ-2 vacuum oil, and the oil is heated to 40℃ before quenching. After the fine punching die is out of the heating chamber, it is firstly air-cooled for 60s, then stirred and cooled in oil for 5 minutes, and then air-cooled.

Tempering process

The equipment used for tempering is a nitrate tempering furnace (the ideal equipment should be a vacuum tempering furnace). The tempering temperature is 550℃±10℃, and the time is 2.5h*3 times. The hardness after tempering is generally 60~62HRC. The degree of tempering should also be checked by metallographic examination. If the degree of tempering is normal or insufficient, supplementary tempering should be carried out. Special attention should be paid to strictly control the temperature accuracy (preferably two instruments, over-temperature alarm) to prevent the occurrence of explosion accidents of nitrate furnaces

Aging treatment

The equipment used for cloud aging is obviously an oil bath furnace, the aging temperature is 1600℃±10℃, the aging time is 6~8h, and cryogenic treatment can be carried out if conditions permit.

Cleaning treatment

After the aging treatment, the fine die is cooled to room temperature and cleaned with gasoline in time. After passing the inspection, anti-rust treatment shall be carried out in time.

Anti-rust treatment

In order to ensure rust prevention between processes, anti-rust treatment should be carried out with anti-rust liquid in time. Generally, it should be soaked for 10~20min, otherwise the anti-rust effect is not good.

Equipment selection: The VOGQ series vacuum heat treatment furnace produced by SIMUWU is a high-quality product for the vacuum heat treatment process of tooling and molds. Good temperature control accuracy and temperature control uniformity ensure the effective progress of the vacuum heat treatment process. SIMUWU specializes in the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.