Method of production of high-pressure seamless cylinder from corrosion-resistant steel

Abstract

Blank of corrosion-resistant steel is coated with coating of water glass with thickness of 20 to 150 μm, cured at 15 to 60° C., and heated in an induction furnace to the temperature of 1180° C. to 1260° C. The heated up blank is without cooling by water descaling transferred into an extrusion press and extruded here, while the coating is broken to pieces and largely removed. Drawing in a horizontal drawing press and necking are performed. After forming to the final shape of the cylinder, leftovers of coating are removed by pressure blasting. A corrosion-resistant thin-walled seamless high-pressure cylinder with volume of 5 to 260 litres is manufactured.

1 . Method of production of high-pressure seamless cylinder from corrosion-resistant steel, in which the starting steel blank ( 1 ) is heated in an induction furnace and then inserted into an extrusion press where it is upset and backward extruded in two steps, from which during the first step, the blank ( 1 ) is inserted into a die ( 4 ) with a vertically moving piercing tool ( 7 ), and here it is moulded by means of extrusion until a thick-walled hollow semi-product ( 5 ) having an inner cavity, walls and bottom is moulded from it, after which this semi-product ( 5 ) is removed from the extrusion press, turned by 90°, and seated in this position into a horizontal drawing press, where the second step of forming in terms of backward drawing takes place, when during this second step, the semi-product ( 5 ) is put on a drawing mandrel having the diameter corresponding to the required final inner diameter of the produced cylinder, and in this drawing press, the semi-product ( 5 ) is extruded through a stripper ring and roller cartridges fitted with reduction rollers by means of which it is rolled on the mandrel, while this rolling is performed so long until the semi-product ( 5 ) acquires the required outer and inner diameter, after which the final shape of the cylinder bottom is formed by insertion of the semi-product ( 5 ) bottom into a sizing die and subsequently, in the course of the backward movement of the drawing mandrel, the semi-product ( 5 ) is pulled off from the drawing mandrel with the help of stripping jaws, aftercooled, and subsequently necked, by which the shape of the manufactured cylinder is finished, characterized by that even before heating in the induction furnace, the blank ( 1 ) is coated on at least 85% of its surface with coating ( 2 ) from material based on water glass with thickness of 20 to 150μτπ, this coating ( 2 ) is cured by drying at the temperature of 15 to 60° C. and only after this curing, the blank ( 1 ) is subjected to heating in the induction furnace. 
     
     
         2 . Method of production of high-pressure seamless cylinder from corrosion-resistant steel according to  claim 1 , characterized by that the material applied to the blank ( 1 ) for example by spraying or by brush consists of suspension containing 20 to 40% w. w. of sodium silicate or potassium silicate or mixture of these silicates, and 40 to 80% w. w. of water, while in the case of presence of admixtures such as bore-silicates and/or corrosion inhibitors, the admixtures are contained in the amount of maximum 20% w. w. 
     
     
         3 . Method of production of high-pressure seamless cylinder from corrosion-resistant steel according to  claim 1  characterized by that the blank ( 1 ) with the coating ( 2 ) from material based on water glass is heated in the induction furnace to the temperature of 1180° C. to 1260° C. 
     
     
         4 . Method of production of high-pressure seamless cylinder from corrosion-resistant steel according to  claim 1 , characterized by that after the blank ( 1 ) with coating ( 2 ) is heated up in the induction furnace, the blank ( 1 ) with coating ( 2 ) is taken out of here and during persistence of its temperature of minimum 1110° C., it is inserted into the extrusion press without performing water jetting of scale between the removal from the induction furnace and insertion into the extrusion press. 
     
     
         5 . Method of production of high-pressure seamless cylinder from corrosion-resistant steel according to  claim 1 , characterized by that during the first step of mechanical working, in the course of piercing, the coating ( 2 ) of material based on water glass is broken to pieces by pushing of the piercing tool ( 7 ) to the blank ( 1 ) and the coating ( 2 ) cracks off during extrusion in the extrusion press until at least its predominant part is removed, 
     
     
         6 . Method of production of high-pressure seamless cylinder from corrosion-resistant steel according to  claim 5 , characterized by that after the final shape of the cylinder is formed from the semi-product ( 5 ), the leftovers of coating ( 2 ) based on water glass are removed from the surface of the semi-product ( 5 ) by pressure blasting of its outer as well as inner surface. 
     
     
         7 . Method of production of high-pressure seamless cylinder from corrosion-resistant steel according to  claim 1 , characterized by that the blank ( 1 ) is made of corrosion-resistant steel while the resulting cylinder is made as a seamless cylinder in the volume range from 5 litres up to 260 litres, as a single necked or double-necked cylinder for any volume within the said range. 
     
     
         8 . Method of production of high-pressure seamless cylinder from corrosion-resistant steel according to  claim 7 , characterized by that in the second step of forming, the semi-product ( 5 ) wall is pressed to the thickness of 2 to 21.5 mm.