The crucible defects in the hot-rolled seamless steel pipe are present on the inner surface of the steel pipe, similar to the size of the soybean granules. Most of the crucibles have foreign objects that are taupe or grayish black. The influencing factors of internal crusting are: oxide removal agent, injection process, mandrel lubrication and other factors. Control measures:
1. Oxide removal agent:
The oxide is required to be in a molten state when the mandrel is pre-punched. Its strength and other strict requirements.
1) The particle size of the oxide removing agent is generally required to be about 16 mesh.
2) The content of sodium stearate in the oxide removal agent should be above 12% so that it can be fully burned in the inner cavity of the capillary.
3) According to the inner surface area of the capillary tube, the amount of the oxide removal agent is generally determined to be 1.5-2.0 g/dm2, and the diameters of the capillary tubes of different diameters and lengths are different.
2. Injection process parameters:
1) The injection pressure should be matched with the diameter and length of the capillary tube to ensure that the purge is strong, the combustion is sufficient, and the deoxidizer that is not completely burned cannot be blown away from the capillary by the air flow.
2) The purge time should be adjusted according to the direct and length of the capillary tube, and the metal oxide in the capillary tube is not blown out as the standard.
3) The height of the nozzle should be adjusted according to the diameter of the capillary to ensure good alignment. The nozzle should be cleaned once for each shift, and the nozzle should be removed for cleaning for a long time. In order to ensure that the de-oxidizing agent is uniformly purged on the inner wall of the capillary tube, an optional device is used at the spraying and deoxidizing agent station, and is equipped with a rotating air pressure.
3. Mandrel lubrication:
If the mandrel is not well lubricated or the mandrel lubricant temperature is too low, it will cause internal crusting. In order to increase the temperature of the mandrel, it is possible to use only one cooling water to cool. During the production process, the temperature of the mandrel rod must be strictly controlled to ensure that the surface temperature of the mandrel bar before spraying the lubricant is 80-120 ° C, and the temperature of the mandrel bar cannot be higher than 120 ° C for a long time to ensure that the lubricant on the surface of the surface before drying is dense and dense. Operators should always check the lubrication of the mandrel.
