Internal scale defects in hot-rolled seamless steel pipes are surface imperfections within the钢管, resembling small dents the size of soybean grains, with most scales containing foreign matter that is grey-brown or grey-black in color. Factors influencing internal scale include descaling agents, blowing processes, mandrel lubrication, and more. Let's take a look at how to control internal surface defects in seamless steel pipes with the help of an editor from a seamless steel pipe manufacturer:

Detergent Oxidizer

Oxides must be in a molten state during the pre-piercing of the core rod. Stringent requirements regarding force and other specifications apply.

The particle size of the deoxidizer powder is generally required to be around 16 mesh.

2) The content of sodium stearate in the deoxidizer must exceed 12% to ensure its complete combustion within the capillary bore.

3) The blowing amount of the descaling agent is determined based on the surface area of the capillary inner surface, which is generally 1.5-2.0g/dm². The dosage of descaling agent varies depending on the diameter and length of the capillary.

2. Blowing Process Parameters

1) The blast pressure should match the tube diameter and length, ensuring both effective blowing and complete combustion, while preventing any unburned oxidizing agents from being blown out of the tube by the gas flow.

2) The blow-off time should be adjusted based on the diameter and length of the capillary, with the standard being no suspended metal oxides remaining inside the capillary after blowing.

3) The nozzle height should be adjusted according to the capillary diameter to ensure proper alignment. The nozzle should be cleaned once per shift, and removed for cleaning during extended downtime. To ensure uniform blowing of the descaler agent along the inner wall of the capillary, an optional device is used at the nozzle blowing station, accompanied by a rotating air pressure.

3. Core Bar Lubrication

Poor lubrication effect of the core rod or excessively low lubricant temperature can lead to internal scabbing. To increase the core rod temperature, a single cooling water cooling method can be employed. Strict control over the core rod's temperature is required during the production process, ensuring the surface temperature of the core rod is between 80-120°C prior to the application of the lubricating agent. The core rod temperature should not remain above 120°C for extended periods to ensure that the lubricant on its surface dries and becomes dense before pre-piercing. Operators should regularly inspect the lubrication condition of the core rod.