Abstract: A method of preparing bimetallic tubes or pipes for roll-forming ribs therefrom, in which the external tube is subjected to initial compressive stress is introduced, is characterized by roughening the ends of the internal tube, and after placing the internal tube in the external tube the ends of the external tube are clamped on the roughened segments of the internal tube with simultaneous axial displacement of a part of the material of the external tube corresponding to said compressive stresses of a required quantity. From the tube assembly thus prepared ribs are drawn. It is preferable that at least one end of the external tube is formed conically during clamping.

Abstract: A method and apparatus for rolling transversely ribbed pipe consists in that the rib after forming is deflected in the direction of rolling parabolically, the external pipe is pressed down to the core pipe, and deflecting the rib and pressing down the external pipe onto the core pipe is carried out during one revolution of the pipe, and afterwards the rib is straightened.The apparatus has three tools provided with roll-formed disks, for supporting and straightening, whereby the second - in the direction of rolling - part of the profile of supporting disks is concave, preferably parabolically, and the last - in the direction of rolling - tool is provided with a supporting disk the outer diameter of which is from 0.1 to 0.8 mm larger than the outer diameter of the other supporting disks.

Abstract: A method of forming ribs on tubes or pipes is characterized by applying to the material of the tube, from which the rib is formed, initial compressive stresses preferably ##EQU1## where Fo denotes the area of the cross-section of the tube before drawing, Fr denotes the area of the cross-section of the core of the tube after drawing the rib, and Re is the plasticity limit. Next, ribs are drawn by driven tools with roll-formed disks while maintaining said compressive stress.

Abstract: There is provided a method for preservation of horticultural products in freshness by circulation of the atmosphere surrounding these products and removal of ethylene from it on the outside of the storage chambers, consisting in removing ethylene by catalytic combustion. Combustion of ethylene is carried out advantageously in the presence of platinum catalyst, obtained by impregnation of active aluminum oxide of specific surface area of about 200 m.sup.2 /g with a 0.05-0.5% solution of chloroplatinic acid followed by drying and heating in the stream of air at the temperature up to 550.degree. C. Ethylene combustion is carried out advantageously in the presence of platinum catalyst additionally activated by impregnation with oleic acid at the temperature of 60.degree.-80.degree. C., slow heating in the stream of nitrogen up to the temperature of 400.degree.-450.degree. C. for 2 hrs, followed by heating in the stream of air at the temperature 500.degree.-550.degree. C.

Abstract: A rolling mill is characterized in that three hydraulic actuators, positid in a mill frame and comprising yokes with attached rolling tools therein, are provided with a piston rod having two pistons. The outer piston co-operates with an external cylinder which is mounted on a body of the actuator by means of a threaded joint. The inner piston co-operates with an internal cylinder attached slidably within said body.At one end, the piston rod is provided with a thrust flange being in contact with spacer washers mounted on the external cylinder, whereas the opposite end of said piston rod includes a stop positioned in a seat of a slider, said stop co-operating with a shoulder on said slider. The slider is mounted slidably on a bottom of the internal cylinder, the end portion of said slider having a pressure flange to press down a tool yoke to the bottom of the internal cylinder during rolling operation.

Abstract: A method and apparatus of forming ribbed pipes, after an initial pipe resssing in which bending of the rib of the plane perpendicular to the rolled pipe axis takes place, and straightening of the rib thenafter. Then on duplex metal pipes, the outside pipe is additionally compressed to the core pipe.A tool for performing the aforementioned is equipped with a disk section for bending the rib, it is formed of a thrust disk and a straightening disk. When rolling a duplex metal pipe at least one compressing disk is placed therebetween.