Circular tube billet - heat - perforation to heading, annealing and pickling to apply oil (copper), multi-channel time cold drawing (cold) and billet tube - heat treatment - straightening to hydrostatic test (NDT) - tag, put in storage.
Before their production process steps are basically the same, the difference from the fourth step, circular tube billet after punch to heading, annealing, should be used after annealing specialized precision seamless tube washing, acid liquid acid pickling, oil, and then followed by cold drawing through multi-channel time (cold) and billet tube, special heat treatment, heat treatment, will be straightening.
Steel pipe by the conveyor belt to the metal detection after straightening aluminium coated steel tube machine (or water pressure experiment) for internal inspection, if the steel pipe internal crack, air bubble, will be detected, steel pipe quality through rigorous after the manual pick, steel pipe quality, spray paint on the number, specification, batch number, etc.
The analysis found in the center of the thickness and 1/4 are obvious and oxidation zone of crack, crack is also near the oxide particles.
The fracture the entire roll there are varying degrees of inner crack, crack mainly exists in plate volume precision seamless tube, near presented continuously through morphology, rolling crack at higher risk.
From the point of market information, the recent steel plant resources, the side impact door beams arrival of the goods quantity is relatively abundant, but due to the downstream terminal purchasing power is limited, slower to stock market, the general merchants cut prices to increase in shipments, other local inventories last week rose slightly, the arrival of the goods plus steel plant volume continues to increase, in the case of poor demand, is expected to music from precision seamless tube market continue to weak lower probability.
Precision seamless tube thick-walled seamless steel pipe cause analysis:Observed under scanning electron microscopy (sem) steel hot rolled seamless steel tube rolling crack defect morphology, fracture is obvious in central crack.
The thick wall seamless steel pipe steel hot rolling crack side impact beams crack and its further observed that at the end near the crack exists obvious oxide particles, crack exists along the intracrystalline cracks, at the end near the crack exhibit the polygonal ferrite morphology.
Near crack within 30 um oxide particle characteristics is closely related to the original defects of continuous casting billet, casting billet in reheating furnace heating for a long time caused the cracks near the element is oxidation, form a thick layer of oxide particles, after the final genetic defects to heat volume.