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How to prevent seamless steel surface decarbonization

Many of seamless steel tubes and seamless steel surface decarbonization life of the degree. For example, the service life of the rope depends on its fatigue strength and wear resistance, if the rope surface decarbonization exceeded, will reduce carbide surface as a strengthening phase and wear phase, and thus will directly affect the performance of these two . In addition, tool steel, bearing steel surface decarburization if not cleaned, will make tool steel, bearing steel surface layer hardness and abrasion resistance is lowered, and upon quenching, due to different changes in the volume of the outer surface is formed leaving cracks. So, how to prevent seamless steel surface decarbonization is a problem in the production process should be noted. Foreign imports of wire rod decarbonization layer 0.02 ~ 0.04mm, wire rod surface Kobe, Japan, can be done without removal, and the average depth of more than similar domestic products decarburization 0.05mm. We need to take steps to change this situation.

 

Surface decarbonization solve problems, the key in the heat treatment step. Due to oxidation and decarbonization and wire are performed simultaneously, so long as the heat treatment process as far as possible the wire less contact with air can reach the purpose of improving the decarbonization. For example, American Spring Wire Company dual lead groove oil quenching and tempering to deal with the valve spring wire, and achieved the desired results. The production process is: first molten lead wire groove from austenitizing effect, advance the lead was heated to 871 , the wire was in the lead through to achieve austenitizing, quenching and then into the sump, and then enter the first two molten lead trough tempering (482 ). Since the wire is not in contact with air in molten lead, and effectively prevent the decarbonization. The main problem with this process needs to be addressed is how to prevent lead dust contamination.

 

Causing surface decarburization atmosphere is primarily oxygen, water vapor and carbon dioxide and other oxidizing gases. When these oxidizing gases into contact with the heated steel surface oxidation and decarbonization occur simultaneously; the affinity of carbon dissolved in the iron and these gases is relatively large, so the carbon on the surface of the first took off. These gases are generally packed into the furnace; and seamless steel pipe mill scale, rust and residue on the post-cold-drawn steel surfaces of the oven heating will decompose, the reaction of some of the oxidizing gas. We can purposefully control the furnace atmosphere, so that in a reducing state, can effectively prevent surface decarburization. For example, controlling the ratio of carbon dioxide to carbon monoxide in the furnace, at equilibrium, neither oxidation nor decarburization; when the ratio exceeds the equilibrium carbon dioxide, oxidation and decarbonization; oxidation and decarburization does not occur below the equilibrium point . Specific numerical balance of the point to be calculated based on the carbon content of iron and temperature. In addition, the furnace blowing neutral protective nitrogen is also an effective measure. Nitrogen into the furnace can dispel certain segments of the oxidizing atmosphere, while maintaining a positive pressure in the furnace to prevent air infiltration, reduce or avoid steel decarbonization.