PRODUCTION METHOD OF SEAMLESS PIPES OF MAJOR AND MIDDLE DIAMETRES FOR STEAM BOILERS, STEAM PIPELINES AND COLLECTORS OF UNITS WITH HIGH AND OVERCRITICAL STEAM PARAMETERS Russian patent published in 2009 - IPC B21B19/04 

FIELD: metallurgy.

SUBSTANCE: invention relates to pipe rolling, particularly it relates to production method of seamless pipes of major and the middle diametres for steam boilers, steam pipelines and collectors of units with high and overcritical steam parameters from hot-rolled pipes - blanks with geometry deviation from requirements of TU143R-55-2001, TU14-3-460-2003. Method includes ingots melting in electric and open-hearth furnace of steels 20, "15ГС", "15ХМ", "12Х1МФ", 15Х1М1Ф", "12Х2МФСР", "10Х9МФБ", "10Х9" "В2МФБР", "12Х11 В2МФ", "08Х16Н9М2", 12Х18Н12Т" and 10Х13Г12БС2Н2Д2", ingots forging into forged pieces with setting ratio from 2.0 till 3.0 subject to steel grade, continuous casting of steel grades 20, "15ГС", "12Х1МФ", "15Х1М1Ф" and "15ХМ" with its following forging into blanks with setting ratio not less than 1.5, ends cutting of forged pieces with removing of shrink and bottom-most portion, ingots smelting of current steel grades by means of electroslag refining, mechanical operation of forged pieces and ingots of electroslag refining into blanks per specified diametre, heating of blanks and ingots till the plasticity temperature subject to steel grade, its broaching in skew-roll piercing mill into cupped blanks, cupped blanks rolling on Pilger rolling mills into pipes of diametre 219-530 mm with walls thickness from 9.0 till 90mm with rolling-out, subject to diametre and wall thickness, calibration, flattening, ultrasonic inspection, scrapping and acceptance of pipes diametre 219-245 mm of single-precise with tolerance for diametre ±1.0%, pipes of diametre from 245 till 530 mm toleranced+1.25/-1.0%, pipes of diametre 219-530 mm tolerance by wall thickness +20/-5.0%, when pipes of diametre from 325 till 530 mm with walls thickness from 40 till 90 mm with geometry deviation are completed into pipes - blanks in lots, heated till the plasticity temperature and rolled at tube mill with Pilger rolling mills into pipes of minor diametre and minor walls thickness, and pipes with walls thickness less than 40 mm are rolled on mills "ХПТ" 250 and "ХПТ" 450 into pipes of minor size per wall and diametre.

EFFECT: providing of decreasing of metal discharge coefficient with repartition of forged blank, "НЛЗ" or electroslag refining ingot - boiler pipe and cost reduction of boiler pipes.

11 cl, 1 tbl