What factors affect the outer diameter accuracy of hot-rolled square tubes?

The outer diameter accuracy of hot-rolled square tubes is determined artificially, and the result depends on the customer, the customer's requirements for the outer diameter of seamless tubes, the operation and accuracy of steel tube sizing equipment, and the steel tube sizing process system.

 

The hot-rolled square tube sizing method is an important factor in determining the outer diameter tolerance of steel tubes. For hot-rolled square tubes sizing by longitudinal rolling, the outer diameter accuracy of steel tubes can reach about 1%, while the outer diameter accuracy of seamless tubes sizing by oblique rolling is as high as 0.5%.

 

The influence of the process system on the outer diameter of steel tubes is mainly determined by the rolling temperature and temperature stability of the steel tube sizing mill. When the rolling temperature of steel tubes is high, the shrinkage of hot-rolled square tubes after rolling is large, which often easily exceeds the outer diameter to produce negative deviations of steel tubes; on the contrary, low rolling temperature may exceed positive deviations and become defective products. Therefore, the steel tube rolling mill should be continuously adjusted according to the size specifications of the sizing hot-rolled square tubes, steel tube grades, temperature conditions, and tool wear conditions.

 

 

The requirements for anti-corrosion steel pipe coatings are mainly in the following three aspects:

 

(1) The coating formed by good corrosion-resistant coatings should be relatively stable when in contact with various corrosive media such as acids, alkalis, salts, industrial sewage, chemical atmosphere, etc., and cannot be dissolved, swollen or decomposed by the corrosive media, nor can it react chemically with the media to generate new harmful substances;

 

(2) The good anti-permeability coating can better prevent the corrosion of the pipeline surface when in contact with highly permeable liquid or gas media;

 

(3) Good adhesion and flexibility: The coating cannot fall off due to vibration or slight deformation of the pipeline, and the coating is required to have a certain mechanical strength.

 

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