Internal Defect Control of Small Diameter High-Pressure Boiler tube

DataTime:[2016-10-7]

Small diameter high-pressure boiler tube surface defects that affect the quality, mainly due to waste generation. Defect localization and analysis, mainly for the defect depth 0.2 ~ 0.5mm, the length of 20 ~ 50mm superficial cracks, which causes the piercing of minute defects generated in the process, or rolling the first and second plurality of specifications by trauma, four planes in the rolling process by the inner surface of the high-pressure boiler tubes oxide residue effects formed in the slide and scarring defects, these defects after rolling sheets minus aggravated squash and stretch.

Through the high-pressure boiler tube double length number tracking found that injury concentrated in the steel tube end report first, twice-foot (from the pipe end within 25m), is closely related to the capillary head borax oxide accumulation, small-diameter steel pipe defect in the front of the capillary the higher the ratio of the rolling zone appears.

Through the above analysis we can draw the following conclusions:

(1) the presence of perforated capillary end in addition to the adverse effects of oxidation issues that need to be improved.

(2) the presence of a work surface and rolling rack rolling defects within the designated road, we need to start to be addressed from the hole, lubrication improvement.

(3) Save dryer sheets high total reduction ratio in diameter, in the presence of the shortage of raw tube defects can not be completely eliminated during rolling.

To reduce and control deficiencies, should take the following improvement measures;

(1) production of 30 ranging from a head injury will change, because the elimination of head generated within the fold.

(2) the production of small diameter high-pressure boiler tubes use no injuries mandrel, the mandrel to eliminate defects produced.

(3) pre-production of the perforated guide and roll away from the measurement, ensure ovality coefficient control within the scope of process requirements.

(4) save photos Save machine wall rate increased to 10 to 15% (previously 5-8%).

(5) finishing temperature controlled at above 860 ℃, increase reheating temperature section 5-8 (1020 +/- 10) ℃, save high-pressure water descaling according to the outer surface of the control in the case of 8 ~ 18MPa, improve Zhang reduction machine exit velocity to 5.5m / s or more.

(6) selection of phosphate instead of sodium sulfide as the main additive borax oxide skin reaction due to phosphate and form a melt, reducing rolling gather at the inner surface of the roll gap during rolling and rolling objects, reducing internal scarring and Stroke tract of chance.

(7) continue to track and analyze the state of the rolling surface anatomy of the card after the tube and the actual measurement data, for rolling the first and second planes pass design improvements make mature ideas, design principles and elements, improved rolling pass 185,151 designed to reduce the total elongation factor, reducing the process Zhang reducing the rate of reduction machine single purpose, to improve the surface roughness of the inner pipe.

(8) this study of existing conditions increase the speed of the mandrel stopper way.

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