A piercing machine includes a plurality of skewed rolls, a plug, a mandrel bar and an outer surface cooling mechanism. The outer surface cooling mechanism is disposed around the mandrel bar at a position that is rearward of the plug, and with respect to an outer surface of a hollow shell advancing through a cooling zone which has a specific length in an axial direction of the mandrel bar and which is located rearward of the plug, as seen from an advancing direction of the hollow shell, the outer surface cooling mechanism ejects a cooling fluid toward an upper part of the outer surface, a lower part of the outer surface, a left part of the outer surface and a right part of the outer surface of the hollow shell to cool the hollow shell inside the cooling zone.

A method for rolling tubes on a continuous tube rolling mill involves deforming a tube billet using a mandrel assembly. The mandrel assembly includes cylindrical mandrel configured such that its ends can be alternately coupled to an attachment of the mandrel assembly. The mandrel is configured such that its ends have portions with a beveled lateral surface, wherein the angle of the generatrix of said surface to the longitudinal axis of the mandrel is between 10 and 70 degrees. The deformation of tube billets is carried out until the amount of wear on the working regions at both ends of the mandrel is not less than 25% of a critical value, then the mandrel is sharpened. The invention increases the service life of a mandrel, reduces the formation of flaws on the inside surface of the tubes, and prevents accidents from occurring during the rolling process.

A method for rolling tubes on a continuous tube rolling mill involves deforming a tube billet using a mandrel assembly. The mandrel assembly includes cylindrical mandrel configured such that its ends can be alternately coupled to an attachment of the mandrel assembly. The mandrel is configured such that its ends have portions with a beveled lateral surface, wherein the angle of the generatrix of said surface to the longitudinal axis of the mandrel is between 10 and 70 degrees. The deformation of tube billets is carried out until the amount of wear on the working regions at both ends of the mandrel is not less than 25% of a critical value, then the mandrel is sharpened. The invention increases the service life of a mandrel, reduces the formation of flaws on the inside surface of the tubes, and prevents accidents from occurring during the rolling process.

A rolling mill for rolling hollow or, in all cases, concave rod-shaped bodies, in particular tubes, in particular seamless tubes, said rolling mill comprising a rolling section (10) with a plurality of mill stands and/or rolling dies (11) arranged in succession to define a rolling axis Y, said rolling mill further comprising moving means for moving a mandrel (20) and a tubular blank (21) fitted onto an end portion (22) of said mandrel (20) along said rolling axis and through said mill stands or rolling dies (11) in succession; wherein said moving means are structured so as to move said mandrel (20) and said blank (21) along said rolling axis Y and through said mill stands or rolling dies (11) in succession by applying a traction on said mandrel.

A sliding sleeve for a synchronous manual transmission assembly is produced by the following steps: a tubular blank is provided in which an internal toothing arrangement is present, and the blank which is provided with the internal toothing arrangement is further processed to form a plurality of sliding sleeves.

A sliding sleeve for a synchronous manual transmission assembly is produced by the following steps: a tubular blank is provided in which an internal toothing arrangement is present, and the blank which is provided with the internal toothing arrangement is further processed to form a plurality of sliding sleeves.

A plug for rolling of a seamless steel pipe, the plug having an oxide layer composed of a cobalt-base oxide on a surface of a coating layer formed by coating a surface of a base metal with cobalt or a cobalt-base alloy, a method for manufacturing the plug and a method for manufacturing a seamless steel pipe using the plug.

A plug for rolling of a seamless steel pipe, the plug having an oxide layer composed of a cobalt-base oxide on a surface of a coating layer formed by coating a surface of a base metal with cobalt or a cobalt-base alloy, a method for manufacturing the plug and a method for manufacturing a seamless steel pipe using the plug.

A ring rolling device includes a drive roller and a rotatable revolving drum, in which five mandrels are rotatably mounted. Ring blanks can be mounted around the mandrels. By rotating the revolver drum, the mandrels move towards and away from the drive roller. The revolver drum is arranged in relation to the drive roller such that by rotating the revolver drum a decreasing roll gap is formed between a mandrel approaching the drive roller and the drive roller, in which roll gap a ring blank mounted around the mandrel is rolled during the rotating of the revolver drum. The revolver drum has four rotatably mounted support rollers, said support rollers supporting the mandrel in the direction of the rotational axis of the revolving drum, such that, during the rolling process, the mandrel is located between the support rollers and the press element.

A ring rolling device includes a drive roller and a rotatable revolving drum, in which five mandrels are rotatably mounted. Ring blanks can be mounted around the mandrels. By rotating the revolver drum, the mandrels move towards and away from the drive roller. The revolver drum is arranged in relation to the drive roller such that by rotating the revolver drum a decreasing roll gap is formed between a mandrel approaching the drive roller and the drive roller, in which roll gap a ring blank mounted around the mandrel is rolled during the rotating of the revolver drum. The revolver drum has four rotatably mounted support rollers, said support rollers supporting the mandrel in the direction of the rotational axis of the revolving drum, such that, during the rolling process, the mandrel is located between the support rollers and the press element.