Forging mandrel for hot-forging tubular workpieces of metal

Abstract

The invention relates to a forging mandrel for hot-forging tubular workpieces of metal, said mandrel comprising a mandrel body and a mandrel bar, in which forging mandrel the mandrel body is composed of a heat-resistant material. The forging mandrel according to the invention is embodied here in such a way that the mandrel body is provided, at least in the work zone, with a layer which reduces the dissipation of heat into the mandrel body during the forging process and adheres firmly to the mandrel body, wherein the layer has a lower thermal conductivity than the material of the mandrel body and has a thickness of at least 50 μm.

1 .- 6 . (canceled) 
     
     
         7 . A forging mandrel for hot-forging a tubular workpiece of metal, comprising:
 a mandrel body made of heat-resistant material; and   a layer adhering firmly upon the mandrel body at least in a work zone thereof, said layer being configured to reduce heat dissipation into the mandrel body during forging and having a thermal conductivity which is lower than a thermal conductivity of the material of the mandrel body, said layer having a thickness of at least 50 μm.   
     
     
         8 . The forging mandrel of  claim 7 , wherein the layer is an oxide layer. 
     
     
         9 . The forging mandrel of  claim 7 , wherein the layer is applied onto the mandrel body through a flame-spraying process. 
     
     
         10 . The forging mandrel of  claim 7 , wherein the layer is applied onto the mandrel body through plasma spraying. 
     
     
         11 . The forging mandrel of  claim 7 , wherein the thermal conductivity of the layer is lower by at least 50% than the thermal conductivity of the material of the mandrel body. 
     
     
         12 . The forging mandrel of  claim 7 , wherein the mandrel body is constructed in the form of a hollow body which is provided with an opening on one side and includes an internal cooling device which extends at least into the work zone. 
     
     
         13 . The forging mandrel of  claim 7 , wherein the mandrel body has a mandrel bar to allow displacement of the mandrel body within the workpiece in axial and rotatable manner.