METHOD FOR PRODUCING INGOT-BLANKS BY ELECTROSLAG REFINING OF LOW-DUCTILE STEEL CONTAINING BORON AND FOR ROLLING TUBES OF SUCH BLANKS IN TUBE ROLLING PLANTS WITH PILGER MILLS FOR FURTHER CONVERSION OF TUBES TO HEXAHEDRAL TUBE-BLANKS FOR COMPACTED STORAGE OF WASTE NUCLEAR FUEL Russian patent published in 2008 - IPC B21B21/04 B21B23/00 B23P6/04 

FIELD: production of ingot-blanks by electroslag refining of low-ductile steel containing boron and rolling tubes of such blanks in tube rolling plants with pilger mills for further conversion of rolled tubes to hexahedral tube-blanks used for compacted storage of waste nuclear fuel.

SUBSTANCE: method comprises steps of casting ingots with size 470-490 x 1700-1750 mm by electroslag refining; mechanically working them by turning to ingot-blanks with size 460 - 480 x 1700 - 1750 mm; drilling central opening with diameter 100±5.0 mm; heating them till yielding temperature 1060 - 1090°C; piercing ingots in skew rolling mill on mandrel with diameter 275 mm to sleeve with size 470 - 480 x 290 in. x 2500 - 2600 mm at elongation degree 1.47 - 1.51; rolling sleeves in pilger mill with backing carbonaceous rings to conversion tube-lengths with size 290 x 12 x 22000-23000 on mandrel with diameter 264 -265 mm at elongation degree 10.25 - 11.0; cutting off pilger heads and seed ends by hot cutting saw; cutting tube-lengths by two tubes of the same length or to tubes with length multiple to length of conversion blank; further straightening tubes in six-roll straightening machine at using temperature of heating for rolling. Electroslag refining ingots are cast in the form of hollow ingots with size 480 x 270 in. x 2450 ± 50 mm. Bottom and shrinkage portions of hollow electroslag refining ingots forming pilger head and seed end at rolling conversion tubes are cast of ductile carbon kinds of steel. Height values of bottom and shrinkage portions of ductile carbon steel are determined from expressions Lb = (0.12 - 0.15)Lt, Ls = (0.05 - 0.06)Lt where Lb - height of bottom portion of hollow ingot of ductile carbon steel, mm; Ls - height of shrinkage portion of hollow ingot of ductile carbon steel, mm; Lt -total height of hollow ingot (2450±50)mm. Hollow ingots are bored and turned at shrinkage side to hollow blanks with size 470 x 280 in. mm till boundary of fusion of two metals in bottom portion of ingots or till shifting to side of ductile carbon steel by 50 - 80 mm at surface roughness degree Rz = 40 mcm or less. At turning, smooth transition from main metal to ductile carbon steel in bottom portion of ingot is provided in the form of truncated cone along distance 50 - 80 mm. Bimetallic hollow ingot-blanks are heated till yielding temperature 1040 -1060°C according to mode for heating steel containing 1.3 - 1.8% of boron. After removing technological crops such as pilger heads and seed ends of ductile carbon steel, - at side of pilger heads and seed ends portions of tubes of ductile carbon steel with length 500 -700 mm are left. Then after cutting tube-lengths by two tubes of the same length or by tubes with length multiple to length conversion blank, tubes are guided for further warm straightening in six-roll straightening machine by their ends of ductile carbon steel. Openings for pulling chain at warm shaping are drilled in tube-blanks with carbon ductile end portions in zones of tube-blanks of ductile carbon steel. Ends of tube-blanks of ductile carbon steel are removed before heat treatment while performing all further operations of manufacturing process.

EFFECT: lowered quantity of rejected tubes, improved efficiency of pilger mills, reduced cost of commercial hexahedral tube-blanks.

10 cl, 1 tbl