GB/T 22560-2008Gas nitrocarburizing of iron and steel parts (English PDF)

6.2 Temperature measurement & control device

6.2.1 The temperature measurement and temperature control device shall comply with the provisions of JB/T 10175.

6.2.2 The heating chamber of the periodic furnace AND each heating zone of

the continuous furnace shall be equipped with its own automatic temperature control and recording device.

6.2.3 Within the predetermined processing temperature range, the total

temperature error, which is indicated by the instrument, shall not exceed ±3 °C.

6.3 Maintenance of equipment

Equipment shall be regularly repaired, according to requirements, to maintain the normal state of the equipment. It shall keep its maintenance records.

6.4 Commonly used penetrants

The technical indicators of the penetrants shall comply with the provisions of

JB/T 9209.

6.4.1 Organic compounds, which contain nitrogen and carbon atoms, such as

triethanolamine, formamide, etc., can be used alone or together with other organic compounds.

6.4.2 Use the ammonia as main gas. Add any kind of gas, such as alcohol cracking gas, carbon dioxide, endothermic atmosphere, exothermic atmosphere. The quality of ammonia gas shall meet the requirements of the first-class products in GB 536-1988.

7.1 Preparation before processing

7.1.1 Confirm the technical requirements of the parts for nitrocarburizing, including the nitrocarburized location, the nitrocarburized depth, the surface hardness, the metallographic structure, etc.

7.1.2 Use appropriate methods to remove oil stains and rust spots, on the

surface of the parts for nitrocarburizing.

7.1.3 Parts for nitrocarburizing, which is to be subject to partial nitrocarburizing, shall be treated with anti-seepage treatment. The anti-seepage agent shall comply with the provisions of JB/T 9199.

7.1.4 Perform stress relief treatment on slender, thin-walled precise parts for

nitrocarburizing. The treatment temperature is generally 20 °C higher than the nitrocarburizing temperature; it shall be kept for a sufficient time; the anti- oxidation measures shall be taken.

7.1.5 Select process equipment; check piping system, heating equipment, control instruments, etc.

7.1.6 The specimens for testing shall be placed together with the furnace. The material, pretreatment, processing conditions of the specimens shall be the same as the parts for nitrocarburizing.

7.2 Furnace loading

7.2.1 When using the material basket (fixture), it shall check its safety performance in advance; remove oil stains.

7.2.2 The workpiece shall be installed in the effective heating area. Pay attention to the furnace loading method, loading amount, loading position, mutual gap of the workpiece and the specimen; prevent the distortion of the workpiece; ensure a good circulation of the atmosphere in the furnace.

7.3 Gas nitrocarburizing process

7.3.1 The heating rate, nitrocarburizing temperature, atmosphere composition, nitrocarburizing time shall be set and controlled, according to the material and technical requirements of the workpiece.

7.3.2 During the treatment process, attention shall be paid to the fluctuation of furnace temperature and the amount of infiltration agent added; the exhaust speed should be fast after entering the furnace; preheating measures can be taken, if necessary.

7.3.3 The commonly used nitrocarburizing temperature is 520 °C ~ 570 °C.

7.3.4 The commonly used nitrocarburizing time is 2 h ~ 4 h.

7.4 Cooling

7.4.1 Oil is usually used as the coolant. Other coolants can also be selected, according to technical requirements.

7.4.2 If the surface color is required, the cooling process after nitrocarburizing shall be carried out, in a nitriding atmosphere or other protective atmosphere.

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