Hot work tool and method for producing same

Abstract

The invention relates to a hot work tool, in particular a piercing mandrel or a rolling bar for producing seamless pipes or a forging mandrel for hot forging tubular workpieces made of metal, said tool having a main tool body ( 2 ), wherein at least one working area of the main tool body ( 2 ) is provided with a coating ( 4 ). In order to achieve an improved strength of the coating ( 4 ) on the main tool body, according to the invention the main tool body ( 2 ) has a profiled surface ( 5 ) and the coating ( 4 ) is applied to the profiled surface ( 5 ). The invention further relates to a method for producing such a hot work tool.

1 . A hot-machining tool, particularly a piercing mandrel or a rolling bar for making seamless pipes or a forging mandrel for hot forging of tubular work pieces made of metal, the machine tool having a base body, the machine-tool base body being provided with a coating at least in a machining region, wherein the machine-tool base body has a surface profiling and the coating is applied to the surface profiling. 
     
     
         2 . The hot-machining tool according to  claim 1 , wherein the surface profiling forms an undercut in an axis direction of the machine tool, the surface profiling particularly is formed by a plurality of ridges and grooves on the surface of the machine-tool base body. 
     
     
         3 . The hot-machining tool according to  claim 1 , wherein the machine-tool base body consists of steel. 
     
     
         4 . The hot-machining tool according to  claim 1 , wherein the coating is a layer that protects against thermal and mechanical stresses. 
     
     
         5 . The hot-machining tool according to  claim 1 , wherein the coating is applied by means of a thermochemical coating method. 
     
     
         6 . A method of making a piercing mandrel or a rolling bar for making seamless pipes or a forging mandrel for hot forging of tubular work pieces made of metal, wherein the method has the following steps:
 a) providing a machine-tool base body with a surface profiling by mechanical machining;   b) applying a coating to the machine-tool base body.   
     
     
         7 . The method according to  claim 6 , wherein, to make the surface profiling, a plurality of raised regions and grooves are formed on the surface of the machine-tool base body, the raised regions being configured as projecting ridges that extend over a predetermined length along a longitudinal axis of the machine tool and that are raised above the grooves by a predetermined height. 
     
     
         8 . The method according to  claim 7 , wherein the grooves are filled with the coating, at least to the height of the ridges, during application of the coating according to step b) of  claim 6 , a preferably the surface of the coating exceeds the height of the ridges. 
     
     
         9 . The method according to  claim 6 , wherein after step a) and before step b) according to  claim 6 , part of the machine-tool base body is subjected to thermochemical conversion that in particular comprises making an iron oxide, particularly preferably of scale. 
     
     
         10 . The method according to  claim 6 , wherein application of the coating according to step b) of  claim 6  takes place by flame spraying, plasma spraying, or by a thermochemical method. 
     
     
         11 . A method of making a piercing mandrel, the method comprising the steps of:
 machining into an outer surface of the mandrel an array of outwardly projecting ridges separated by outwardly open grooves; and   applying a coating to the outer surface over the ridges and grooves that generally fills the grooves.   
     
     
         12 . The mandrel-making method defined in  claim 11 , wherein the coating is applied in a thickness greater than a depth of the grooves so as to cover and embed the ridges. 
     
     
         13 . The mandrel-making method defined in  claim 11 , further comprising the step after machining the formations into the outer surface and before applying the coating of:
 thermochemically converting an outer surface of the mandrel at the grooves and ridges so as to increase adherence of the coating to the tool.   
     
     
         14 . The mandrel-making method defined in  claim 13  wherein the mandrel is of steel and the thermochemical conversion is oxide formation. 
     
     
         15 . The piercing mandrel made by the method of  claim 11 .