Defects and treatment of cold drawn steel pipe
Defects and treatment of cold drawn steel pipe is as following:
1, folding: pulling system, cold drawn steel pipe inside and outside surfaces rendered straight or spiral direction of folding, the emergence of local or long pass on the pipe.
The cause: the surface of the pipe material folded or flat debris, severe abrasions and cracks the Tube mill repair at corners or aspect ratio (H / b) is not enough.
Prevention and elimination method: in strict accordance with the procedures required tube material grinding. Substandard pipe material is not put into operation a preventive measure. The a good perforation hot order strict quality.
2, size of tolerance (including the wall thickness of the ultra-poor, uneven wall thickness, diameter ultra-poor, oval) diameter exceeding the scope of the standard deviation, in the same section on the wall side of the thin, thick, diameter ranging from the minor axis difference beyond the standard requirements.
The causes: 1, of drawing mold selection is not only, or Rui stick (internal model) improperly adjusted. 2 draft within the mold design and manufacture of unreasonable or badly worn or stiff enough to cause deformation wear. 3, heat treatment for a long time and high temperature. Uneven or heat treatment performance. 4, changes in the law of the wall empty pull properly controlled, pull tab preparation unreasonable. 5, cold drawn steel pipe straightening squashed job cards gage is not zero, large errors.
Prevention and elimination methods: 1, correct design and manufacturing and optional extubation mold. 2, the correct implementation of the heat treatment system, uniform heating. 3, Correctly adjust the leveler, often proofreading extubation machine parts location and measuring tools. 4, correct and reasonable preparation pulling watchmaking master the different kinds of steel, the law of the increase or decrease of the different specifications of steel pipe wall. 5, ovality no grid, judged as qualified products, ovality out of line can be re-straightening, resectable local ovality outrageous.
3, the program presents: cold drawn steel pipe surface the longitudinal linear scratches called zoned Road. Zoned tract of varying lengths, wear a narrow range, multi-ditch like visible ditch.
The causes: 1, the draft table is not smooth, crack or knot metal. 2, the the hammerhead transition part edges and corners, wear tool. 3, Owe pickling or capillary residual oxide scale. 4, greasing, phosphating, saponification process operating properly. 5, inside and outside the mold, damaged or badly worn. 6, the intermediate annealing is uneven, the deformation amount is insufficient.
Prevention and elimination method: 1, improve the quality of extubation mold surface. 2, Oxide pickling, rinse, uniform solid coating. 3, hammerhead transition in part to rounded corners. 4, Ground inspection of the mold and the surface of the steel pipe, identify problems and timely treatment.
4, shaking pattern: cold drawn steel pipe surface along the length was the the spiky ring wave or wave-by the same arrangement, local or long pass appeared on the surface of the steel pipe inside and outside.
The causes: 1, uneven performance after heat treatment, poor lubrication, the saponification uneven. 2, Rui thin rod, Rui lever pull system produces elastic deformation caused by jitter. 3, the draft shape unreasonable entrance cone angle too, so that the the steel die hole contact area is too small, so that the the draft system deformation unstable surface jitter.
Prevention and elimination method: 1, processing procedures required to achieve softening uniform performance. 2, take a good quality of pickling, phosphating, saponification. The specified variable sleet drawing. 3, the correct selection of the size Rui rod.
5, pulling concave: steel pipe longitudinal direction, the wall was strip inward depression, its length no rules.
The causes: 1, non-the pistil stick drawing (empty Stubbs) thin steel pipe, reducing excessive. 2, the end of the steel pipe hammer edges and corners, the transition part folds. 3, the the local thin wall of the pipe material (such as grinding repair point).
Rational allocation by the amount of reduction to the prevention and elimination method: 1, empty pull the thin-walled tube. 2, hammerhead end edges and folds. 3, a partial defect of the surface of the pipe material, the clean-up, the aspect ratio should be reasonable.
6, Cracking (diastema): cold drawn steel pipe presented penetrate the wall of the longitudinal split, through long-localized cracking.
The causes: 1, excessive pressure, even pulling too many passes, tube material work hardening serious, especially empty Stubbs. 2, Improper heat treatment, surface pipe material plastic made different to reactive work hardening is not total elimination. 3, steel tube drawing heat treatment in a timely manner. 4, low plasticity steels are easier to crack.
Prevention and elimination method: 1, a reasonable preparation for pulling a tab. 2, alloy steel tube and pull even pulling steel pipe to heat treatment in a timely manner. 3, heat treatment according to process requirements, the cooling rate should be reasonable control, its performance even eliminate work hardening.
7, too pickling: cold drawn steel pipe surface render the hole like sesame-shaped cracks, the severity of different general outer surface serious than the inner.
The causes: 1, steel pipe surface oxide thickness uneven, loose and firmly. 2, the pickling time is too long. 3, pickling concentration is low, a high content of ferrous sulfate in the case of high pickling temperature easy before pickling. 4, the acid concentration is uneven, the solution does not flow, corrosion uneven.
Prevention and Elimination: 1, to properly execute pickling technical operation. 2, heat treatment operations, to prevent uneven thickness of steel pipe surface oxide scale. Strictly implement the wash hanging wash look, ground inspection, to prevent over-pickling.
8, Cold drawn steel pipe surface into a piece of fine dot-like pits, pitting: (Ma surface pits) partial or continuous on the steel surface.
The causes: 1, heat treatment caused the iron skin is too thick, pressed into straightening iron skin peeling and pitting. 2, after pickling residual oxide scale or saponification liquid dirt, pitting pull. 3, tube pickling, parked too long rust caused by a pockmarked face. 4, the tube surface oil, heat treatment coalesce into oil point fired heating pockmarked face.
Prevention and elimination of the method: 1, the correct implementation of the heat treatment furnace installed system. 2, adhere to the quick turnaround. 3, pickling do wash, do not owe wash drawing in a timely manner after pickling.
9, Drawing Fracture: Drawing produce strange sounds, lack of lubrication effect, mold Rui nap strain tube drawing machine load increases, the lower yield.
Causes: 1, before the procedure does not comply with the rules, problems on certain aspects, such as pickling carbonization (hydrogen embrittlement), caused by the cold-drawn steel tube drawing fracture. 2, phosphating is not up to the transition (too old) caused phosphate coating off the drawing unfinished saponification purpose, which produce cold drawn strange sounds constantly. 3, saponification temperature is too low or too high, the concentration is insufficient, the insufficient amount of saponified adsorption or soap was acidified loss of lubricating effect. 4, phosphating cause mold Rui and tube wall damage, drawing the load increases.
Prevention and elimination methods: 1, the procedure strictly, to control pickling concentration, temperature, time, wash rinse, changing the water. 2, regular checks of the phosphating solution of total acidity, free acidity, the formation of a sufficient amount of phosphate film. 3, the control of the saponification temperature, concentration, keep groove Soap clean.