The disadvantage of scabbing in hot rolled seamless steel pipes is the presence of dents on the inner surface of the pipes, similar to the size of soybean seeds. Most of the scabbing contains black brown or gray black foreign objects. The influencing factors of internal scabbing include factors such as deoxidizers, spraying process, and spindle wetting. Let's take a look at how to control the internal surface defects of seamless steel pipes with the editor of the seamless steel pipe manufacturer:
1. Deoxidizer
The oxide is specified to be in a molten state when the core shaft is pre penetrated. Its strength and other strict requirements.
1) The particle size of the deoxidizer powder is generally required to be around 16 mesh.
2) The content of sodium stearate in the deoxidizer should reach more than 12% to enable it to fully burn in the inner wall of the capillary.
3) The blowing amount of the deoxidizer is determined based on the surface area of the capillary, which is generally 1.5-2.0g/dm2. The amount of deoxidizer obtained by blowing different diameters and lengths of capillary varies.
2. Injection process parameters
1) The injection pressure should be matched with the diameter and length of the capillary, ensuring strong blowing and sufficient combustion, while preventing incomplete combustion of the deoxidizer from being blown away by the cyclone from the capillary.
2) The blowing time should be controlled based on the length and direction of the capillary, with no floating hydroxide in the capillary being blown out as the benchmark.
3) The height of the nozzle should be controlled based on the diameter of the capillary to ensure excellent alignment. Clean the nozzle once per train, and remove the nozzle for cleaning after long-term shutdown. To ensure a uniform blowing of the deoxidizer on the inner wall of the capillary, optional equipment and rotating air pressure should be used in the process of blowing the deoxidizer.
3. Spindle lubrication
Poor lubrication effect of the spindle or low temperature of the spindle lubricant can result in internal scabbing. In order to increase the temperature of the core shaft, a single cooling water cooling method can be used. During the production process, it is necessary to strictly control the temperature of the core shaft to ensure that the surface temperature of the core shaft before spraying lubricant is between 80-120 ℃, and the temperature of the core shaft cannot exceed 120 ℃ for a long time to ensure that the lubricant on its surface is dry and dense before pre threading. Operators should regularly check the lubrication condition of the core shaft.
