Gas Carburizing is to increase the carbon content and a certain carbon concentration gradient in the surface layer of steel parts. The Chemical Heat Treatment process of heating and holding steel parts in Carburizing medium to make carbon atoms penetrate into the surface layer of steel parts is called Carburizing . Carburizing steel generally uses ordinary Carbon Steel , high-quality carbon structural steel and low-carbon alloy structural steel, and Q235 steel can also be used.
1. Carburizing The workpiece surface shall be free from rust, dirt, cracks, scratches and other defects.
2. For the area of the workpiece surface that does not require Carburizing , surface copper plating or anti- Carburizing coating can be used to prevent Carburizing . After Carburizing , the Carburizing layer can also be cut away from the part that does not require Carburizing . The thickness of the copper plating layer should generally be greater than 0.03mm; the thickness of the anti- Carburizing coating should generally be greater than 0.3mm, and the coating is required to be dense.
3. When using the drip-type Carburizing , the Carburizing agent is generally methanol (forms carrier gas); kerosene or acetone, ethyl acetate (forms enriched gas), other types of Controlled Atmosphere Carburizing can also be used when conditions allow. To obtain high-quality Carburizing and reduce carbon black, it is best to use aviation kerosene for dripping.
4. Prepare the test specimen and the intermediate test specimen. The test specimen should be taken from the same batch of parts, and the surface of the test specimen must not have rust or oil contamination. The intermediate test specimen is generally a Φ10mm×10 steel test bar.
1. Check Equipment before furnace startup (refer to the operating procedures of the Pit-type Gas Carburizing Furnace)
2. According to the furnace shutdown time and the furnace pot conditions, carry out furnace pot Carburizing in accordance with the provisions of the process documents. For the furnace pot Carburizing time, it is generally 6-12h for new furnace pots, and generally about 2-4h for old furnace pots.
3. Furnace Charging:
a. Place workpieces with the same material, the same Carburizing layer Technical Requirement , and the same post-heat treatment method Carburizing into the same furnace for production. Place the test specimen at a representative position of Material Basket . The loading capacity and charging height of each furnace shall be less than the maximum loading capacity and charging height specified in Equipment .
b. To ensure unobstructed circulation of Carburizing Atmosphere inside the furnace, make Carburizing layer uniform, a gap greater than 5mm both vertically and horizontally should be left between workpieces.
c. Material Basket When loading into the furnace, place vertically, each layer Material Basket should be neat, no gaps allowed, and suspend the test sample bar into the middle at the same time.
d. After the workpiece enters the furnace, tighten Furnace Lid , air leakage is not allowed. After dropping in Carburizing agent, the furnace pressure should be maintained at 196-490Pa. Ignite the exhaust gas, the flame height should be 200-300mm.
4. Carburizing a. Carburizing Process curve: According to the requirements of material and Carburizing layer microstructure, Carburizing process curve is specified by relevant process documents. Generally, for Low Alloy Steel steel workpieces that require strict control of carbide, you can refer to the process curve diagram as (1-4). For Low Carbon Steel , Low Alloy Steel workpieces that do not require strict control of carbide, you can refer to the process curve diagram.
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