METHOD FOR PRODUCING BIMETALLIC CENTRIFUGALLY CAST BILLETS AND BIMETALLIC WEAR-RESISTANT TUBES FOR TRANSPORTING ABRASIVE LOOSE MATERIALS AND PULPS IN TUBE ROLLING AGGREGATES WITH PILGER MILLS

摘要

FIELD: metallurgical, tube rolling processes, namely method for producing bimetallic centrifugally cast billets and bimetallic tubes, possibly production of bimetallic billets in centrifugal casting plants and production of tubes in tube rolling plants with pilger mills.;SUBSTANCE: method comprises steps of centrifugal casting of hollow bimetallic billets with wear-resistant inner layer consisting of 50 - 60% of total thickness of wall and with plastic outer layer consisting of 50 -40% of total wall thickness; heating billets up to yielding temperature (1180 - 1200°C); rolling them in tube rolling plants with pilger mills to bimetallic tubes with inner wear-resistant cladding layer consisting of 50% of total wall thickness and elongation degree μ≤ 9.0. Hollow centrifugal cast bimetallic billets are three-layer ones while taking into account furnace loss of plastic outer and inner layers of centrifugal cast bimetallic billets at heating them for rolling in heating furnaces till yielding temperature. Bimetallic tubes are rolled in pilger mills at reducing them along diameter from 100≤ΔD ≤ 180 mm. Thickness of plastic layers of bimetallic centrifugal cast billets is increased while taking into account loss at heating billets for rolling till yielding temperature and at increasing their outer diameter whose values are determined according to given formulae where D -outer diameter of centrifugal cast bimetallic billet, mm; Δ_l - loss value being thinning degree of wall of plastic outer of bimetallic billet at heating it till yielding temperature, mm; K - metal loss coefficient of outer surface of cast bimetallic billet at heating it till yielding temperature; Δ_l ¹ - loss value being thinning degree of wall of plastic inner layer of bimetallic billet at heating it till yielding temperature, mm; K¹ - metal loss coefficient of inner surface of cast bimetallic billet at heating it till yielding temperature. Invention provides possibility for producing high quality (without cross fissures) elongated tubes ( 10 -12 m), lowered metal consumption (by 102 kg per t of metal) at conversion " bimetallic billet - bimetallic tube" due to significantly reduced number of cross fissures at rolling tubes in tube rolling aggregates with pilger mills. It is possible to increase useful life period of tubes for transporting abrasive loose materials in permafrost regions from billets with increased wear resistant layer cast according to invention by 1.5 - 2 times in comparison with tubes rolled according to well known techniques.;EFFECT: increased useful life period of tubes.;6 cl, 1 tbl