FABRICATION METHOD OF SEAMLESS HOT-DEFORMED TUBES OF LARGE AND MEAN DIAMETRES FROM DIFFICULT-TO-FORM GRADES OF STEEL AND ALLOYS ON TUBE-FORMING INSTALLATION WITH PILGER MILLS Russian patent published in 2010 - IPC B21B21/00 

FIELD: metallurgy.

SUBSTANCE: invention refers to fabrication method of seamless hot-deformed tubes of large and mean diametres from difficult-to-form grades of steel and alloys on tube-forming installations with pilger mills, and can be used at fabrication of tubes with diametre of 219-550 mm on tube-forming installation with pilger mills. Method involves drilling in workpieces and ingots of electroslag remelting process of central hole with diametre of 100+5.0 mm, heating of workpieces and ingots of electroslag remelting process to ductility temperature, their conversion to hollow thick-walled shells in one skew rolling mill with further rolling to thin-walled shells in the second skew rolling mill, which are installed in-series; at that, conversion of drilled workpieces and ingots of electroslag remelting process from difficult-to-form grades of steel and alloys with diametre of up to 500 mm is performed in one skew rolling mill, and workpieces and ingots of electroslag remelting process of more than 500 mm are converted to thick-walled shells in the second skew rolling mill installed parallel to the first one with an offset of inlet and outlet sides, conversion of drilled workpieces and ingots of electroslag remelting process from difficult-to-form grades of steel and alloys with diametre of up to 500 mm is performed in skew rolling mill with drawing µ= 1.2-1.5 and rise as to diametre of 3.0-5.0%, and conversion of drilled workpieces and ingots of electroslag remelting process with diametre of more than 500 mm is performed to thick-walled shells on the first skew rolling mill with drawing µ=1.1-1.15 and rise as to diametre of 2.0-3.5%, and rolling to thin-walled shells - in the second skew rolling mill with drawing µ=1.1-1.25 and rise as to diametre of 3.0-4.5%.

EFFECT: possibility of forming stock of orders with tubes in small batches, and reducing production cost of tube products.

2 cl, 1 tbl