How to control the defects on the inner surface of seamless tube

How to control the defects on the inner surface of seamless tube? The scarring defect in the hot continuous rolling seamless tube exists on the inner surface of the steel pipe, which is similar to the pit of the size of a soybean grain. Most of the scars have gray-brown or gray-black foreign matter. The influencing factors of internal scarring include: deoxidizer, injection process, mandrel lubrication and other factors. Let’s follow the carbon steel tube manufacturer to see how to control the inner surface defects of seamless steel tubes: 1. Deoxidizer The oxide is required to be in a molten state when the mandrel is pre-pierced. 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 scavenging agent should reach more than 12%, so that it can fully burn in the capillary lumen. 3) Determine the injection amount of the deoxidizer according to the inner surface area of the capillary, generally 1.5-2.0g/dm2, and the amount of the deoxidizer sprayed by the capillary with different diameters and lengths is different. 2. Injection process parameters 1) The injection pressure should be matched with the diameter and length of the capillary, which not only ensures powerful blowing and sufficient combustion, but also prevents the incompletely burned scavenger from being blown away from the capillary by the airflow. 2) The purging time of the seamless steel pipe manufacturer should be adjusted according to the directness and length of the capillary, and the standard is that there is no suspended metal oxide in the capillary before being blown out. 3) The height of the nozzle should be adjusted according to the capillary diameter to ensure good centering. The nozzle should be cleaned once every shift, and the nozzle should be removed for cleaning after a long shutdown. In order to ensure that the deoxidizing agent is evenly blown on the inner wall of the capillary, an optional device is used at the station for blowing the deoxidizing agent, and it is equipped with a rotating air pressure. 3. Mandrel lubrication If the lubrication effect of the mandrel is not good or the temperature of the mandrel lubricant is too low, internal scarring will occur. In order to increase the temperature of the mandrel, only one cooling water cooling method can be adopted. During the production process, it is necessary to strictly control the temperature of the mandrel to ensure that the surface temperature of the mandrel is 80-120°C before spraying the lubricant, and the temperature of the mandrel should not be higher than 120°C for a long time, so as to ensure that the lubricant on the surface is dry and dense before pre-piercing , The operator should always check the lubrication condition of the mandrel. Post time: Jan-05-2023