Furnace of heat treatment, the method of heat treatment, and the directions for use of furnace of heat treatment

Abstract

A furnace of heat treatment capable of keeping a stable nitriding quality for a long period of time is provided. The furnace of heat treatment performs a halogenation treatment and a nitriding treatment by heating a steel material under a predetermined atmosphere. An alloy containing Ni ranging between 50 mass % or more and 80 mass % or less and Fe ranging between 0 mass % or more and 20 mass % or less is used as a material of surfaces of core internals exposed to a treatment space where the nitriding treatment is performed. Accordingly, a nitriding reaction is hardly caused on the surfaces of the core internals, and the halogenation treatment and the nitriding treatment to an article to be treated can be stably executed for a long period of time. Further, a nitrided layer can be stably formed according to purposes on any types of steel materials including a steel type hard to be nitride.

1 . A furnace of heat treatment for performing a halogenation treatment and a nitriding treatment by heating a steel material under a predetermined atmosphere, an alloy that contains Ni ranging between 50 mass % or more and 80 mass % or less and Fe ranging between 0 mass % or more and 20 mass % or less being used as a material of a surface of a core internal exposed to a treatment space where the nitriding treatment is performed, and when the halogenation treatment and the nitriding treatment are repeated, in a case where the nitrided layer formed on the surface of the core internal has a thickness beyond 25 μm, at least a portion of the nitrided layer being removed. 
     
     
         2 . The furnace of heat treatment according to  claim 1 , wherein a surface roughness of the surface of the core internal is equal to or less than 1.6 μm in Ra. 
     
     
         3 . The furnace of heat treatment according to  claim 1 , wherein a test piece made of the same material as a material of the surface of the core internal is placed within the treatment space. 
     
     
         4 . A method of heat treatment for performing a halogenation treatment and a nitriding treatment by heating a steel material under a predetermined atmosphere, comprising:
 using an alloy containing Ni ranging between 50 mass % or more and 80 mass % or less and Fe ranging between 0 mass % or more and 20 mass % or less as a material of a surface of a core internal exposed to a treatment space where at least the nitriding treatment is performed; and   removing at least a portion of a nitrided layer, when the halogenation treatment and the nitriding treatment are repeated, in a case where the nitrided layer formed on the surface of the core internal has a thickness beyond 25 μm.   
     
     
         5 . Directions for use of furnace of heat treatment for performing a halogenation treatment and a nitriding treatment by heating a steel material under a predetermined atmosphere, comprising:
 using an alloy containing Ni ranging between 50 mass % or more and 80 mass % or less and Fe ranging between 0 mass % or more and 20 mass % or less as a material of a surface of a core internal exposed to a treatment space where the nitriding treatment is performed; and   removing at least a portion of a nitrided layer, when the halogenation treatment and the nitriding treatment are repeated, in a case where the nitrided layer formed on the surface of the core internal has a thickness beyond 25 μm.   
     
     
         6 . The directions for use of the furnace of heat treatment according to  claim 5 , wherein at least a portion of the nitrided layer or all of the nitrided layer is removed so that a surface roughness of the surface of the core internal becomes 1.6 μm or less in Ra. 
     
     
         7 . The directions for use of the furnace of heat treatment according to  claim 5 , wherein at least a portion of the nitrided layer or all of the nitrided layer is removed and cracks generated in the surface are substantially eliminated. 
     
     
         8 . The directions for use of the furnace of heat treatment according to  claim 5 , wherein a test piece made of the same material as and having a similar surface roughness to the material of the surface of the core internal is placed within the treatment space, and when the halogenation treatment and the nitriding treatment are repeated, a thickness of the nitrided layer formed on the surface of the core internal is estimated based on a state of the test piece. 
     
     
         9 . The directions for use of the furnace of heat treatment according to  claim 5 , wherein at least a portion of the nitrided layer is removed so that a surface hardness becomes 900 Hv or less. 
     
     
         10 . The directions for use of the furnace of heat treatment according to  claim 5 , wherein at least a portion of the nitrided layer is removed so that a thickness of the nitrided layer becomes 25 μm or less. 
     
     
         11 . The furnace of heat treatment according to  claim 2 , wherein a test piece made of the same material as a material of the surface of the core internal is placed within the treatment space. 
     
     
         12 . The directions for use of the furnace of heat treatment according to  claim 6 , wherein at least a portion of the nitride layer or all of the nitride layer is removed and cracks generated in the surface are substantially eliminated. 
     
     
         13 . The directions for use of the furnace of heat treatment according to  claim 6 , wherein a test piece made of the same material as and having a similar surface roughness to the material of the surface of the core internal is placed within the treatment space, and when the halogenation treatment and the nitriding treatment are repeated, a thickness of the nitrided layer formed on the surface of the core internal is estimated based on a state of the test piece. 
     
     
         14 . The directions for use of the furnace of heat treatment according to  claim 7 , wherein a test piece made of the same material as and having a similar surface roughness to the material of the surface of the core internal is placed within the treatment space, and when the halogenation treatment and the nitriding treatment are repeated, a thickness of the nitrided layer formed on the surface of the core internal is estimated based on a state of the test piece. 
     
     
         15 . The directions for use of the furnace of heat treatment according to  claim 12 , wherein a test piece made of the same material as and having a similar surface roughness to the material of the surface of the core internal is placed within the treatment space, and when the halogenation treatment and the nitriding treatment are repeated, a thickness of the nitrided layer formed on the surface of the core internal is estimated based on a state of the test piece. 
     
     
         16 . The directions for use of the furnace of heat treatment according to  claim 6 , wherein at least a portion of the nitrided layer is removed so that a surface hardness becomes 900 Hv or less. 
     
     
         17 . The directions for use of the furnace of heat treatment according to  claim 7 , wherein at least a portion of the nitrided layer is removed so that a surface hardness becomes 900 Hv or less. 
     
     
         18 . The directions for use of the furnace of heat treatment according to  claim 8 , wherein at least a portion of the nitrided layer is removed so that a surface hardness becomes 900 Hv or less. 
     
     
         19 . The directions for use of the furnace of heat treatment according to  claim 6 , wherein at least a portion of the nitrided layer is removed so that a thickness of the nitrided layer becomes 25 μm or less. 
     
     
         20 . The directions for use of the furnace of heat treatment according to  claim 7 , wherein at least a portion of the nitrided layer is removed so that a thickness of the nitrided layer becomes 25 μm or less. 
     
     
         21 . The directions for use of the furnace of heat treatment according to  claim 8 , wherein at least a portion of the nitrided layer is removed so that a thickness of the nitrided layer becomes 25 μm or less. 
     
     
         22 . The directions for use of the furnace of heat treatment according to  claim 9 , wherein at least a portion of the nitrided layer is removed so that a thickness of the nitrided layer becomes 25 μm or less.