Hot rolled and cold drawn pipe difference between five:
Because hot rolled pipe and cold rolling production process is different, so the hot-rolled tube that sells on the market is divided into hot rolled seamless steel pipe and hot rolling welded steel pipe; And cold rolled tube can be side impact beams divided into cold rolled seamless steel tube and cold rolling welded steel pipe, cold rolled seamless steel tube and can be divided into circular tube and special-shaped tube of the two.
Actually, hot rolling pipe and cold rolled after molding, the difference is not very big, at the same time, the mechanical properties of them are about the same. Finally, small make up remind everybody, even if you have intend to buy these pipes must choose a more formal, with strong strength, word of mouth good manufacturers to buy, like this only then can guarantee the quality of pipe material and the use of life.
304 stainless steel tube by adding chromium, nickel and other metal elements, and the composition is relatively high, is easy to become a high density of passivation oxide film, so it has excellent corrosion resistance, not easy to rust. , however, in some circumstances, such as coastal areas or wet warehouse and chlorine ion can easily penetrate and erode the passive cold drawn tubes film of stainless steel, stainless steel will with the passage of time gradually corrosion and rust, passivation treatment can improve the corrosion resistance of stainless steel pipe.
Passivation is a kind of passive film, due to the effect of metal and oxide, the passive film on the metal surface is very thin, dense, good coverage, strong adsorption. Is usually a metal oxide, usually of metal oxide compound. It will be completely separate metal and corrosion media, prevent metal contact with the corrosive medium, to dissolve metal ground to a halt, passivity, anti-corrosion effect.
After passivation, not an increase of 304 stainless steel tube thickness, change color, improve product precision and added value, make the operation more convenient; Passivation process has no reaction, passivator reusable, long service life and cost more economy; Passivation promote oxygen molecules structure metal surface passivation membrane, membrane layer density, stable performance and repair in the air at the same time, the rust-proof method compared to the passivation film is more stable, resistant to corrosion.
But it is important to note that if the 304 stainless steel tube surface dirt before passivation, and should be mechanical cleaning, then oil removal. If the passivation liquid cannot remove oil on the surface of the beam impact tubes oil will affect the quality of the passivation. Therefore, you cannot omit oil and removal. Oil and removal can be used in lye, emulsifier, organic solvent and steam. For passivation solution, HNO3 should be controlled between 20% ~ 50%. According to the electrochemical test, HNO3 concentration less than 20% of the passivation film quality is not stable, easy to produce pitting, but should not be greater than 50% HNO3 concentration, to prevent excessive passivation. If 304 stainless steel tube surface after pickling passivation spots or stains, available fresh passivation solution or high concentration of nitric acid scrubbing. Eventually passivation of stainless steel pipe should be pay attention to protect, use polyethylene film or dress, avoid different metal and nonmetal contact.
The section distribution of cold rolling tube with hot rolled tube have some different, this is because the production molding, the causes of residual stress is different. This leads to the residual stress of cold rolling tube cross section of some bend, and the residual stress of hot rolled tube belongs to the thin film.