Measures of Boiler Tube Defects in the Low-pressure Control

　　Through the low-pressure boiler tube tracking the number of times the foot found concentrated in the steel tube reported injured end of the first, twice feet (from the end of the inner tube 25m), closely related to the capillary head borax oxide accumulation, low-pressure boiler tube defects in capillary higher rates of front rolling to appear. Through the above analysis we can draw the following conclusions:

　　1, The presence of perforated capillary end effects in addition to bad oxidation issues that need to be improved.

　　2, When present on the surface in the rolling rack rolling work plan tract defects, it needs to be addressed from the start hole, lubrication improvement.

　　3, Save higher overall machine diameter ratio of blank pipe in the presence of genetic defects can not be completely eliminated during rolling.

　　To reduce and control deficiencies, should take the following improvements:

　　1, A head injury ranging from the production of 30 will change, eliminate off by head generated.

　　2, The production of low-pressure boiler tubes use no injuries mandrel, the mandrel to eliminate defects produced.

　　3, Pre-production of the perforated roller and guide from distance measurements to ensure ovality coefficient control within the range of process requirements.

　　4, Machine Save Save walls rate increased to 10 - 15% (formerly 5 - 8%).

　　5, Finishing temperature controlled at above 860 ℃, temperature increase reheating 5--8 section (1020 +/- 10) ℃, according to Zhang Save high-pressure water descaling the outer surface of the control situation in 8--18MPa, improving Zhang Save outlet velocity to 5.5m / s or more.

　　6, The choice of phosphate instead of sodium sulfide as the main additive borax is due to iron oxide react with the phosphate to form a melt, reducing rolling gather the inner surface of the roll bite at the time of Rolling was to reduce internal scarring and draw Road produced by chance.

　　7, Continue to follow the inner surface state and the actual measurement data analysis anatomy stuck pipe rolling after rolling on the first two pass design improvements made mature ideas, design principles and elements, improved rolling 185,151 Pass Design , to reduce the total elongation factor, reducing the process Zhang Save reducing the rate of single machine purposes, improve the surface roughness in the steel pipe.

　　8, Under the existing conditions improve research mandrel stopper speed way.

　　Through the above measures, the process gradually fixed, low pressure boiler tubes injuries has been effectively controlled, inspection pass rate stability, an average of 95.5%.