Method for Producing Plated Black Heart Malleable Cast Iron Member, and Plated Black Heart Malleable Cast Iron Member

Abstract

Disclosed is a method for producing a plated black heart malleable cast iron member including a black heart malleable cast iron member and a plating layer formed on a surface of the black heart malleable cast iron member, the method including the steps of: performing graphitization in a non-oxidizing and decarburizing atmosphere; performing a particle projection treatment on a surface of the black heart malleable cast iron member obtained after the graphitization such that silicon oxide remains on the surface; immersing the black heart malleable cast iron member obtained after the particle projection treatment in a flux for 3.0 minutes or more; and performing hot-dip plating on the black heart malleable cast iron member obtained after the immersion in the flux.

1 . A method for producing a plated black heart malleable cast iron member comprising a black heart malleable cast iron member and a plating layer formed on a surface of the black heart malleable cast iron member, the method comprising the steps of:
 performing graphitization in a non-oxidizing and decarburizing atmosphere;   performing a particle projection treatment on a surface of the black heart malleable cast iron member obtained after the graphitization such that silicon oxide remains on the surface;   immersing the black heart malleable cast iron member obtained after the particle projection treatment in a flux for 3.0 minutes or more; and   performing hot-dip plating on the black heart malleable cast iron member obtained after the immersion in the flux.   
     
     
         2 . The method for producing the plated black heart malleable cast iron member according to  claim 1 , wherein the non-oxidizing and decarburizing atmosphere is an atmosphere in which a partial pressure of oxygen is ten times or less as high as an equilibrium partial pressure of oxygen in chemical formula 1 below and higher than an equilibrium partial pressure of oxygen in chemical formula 2 below.
   [Chemical Formula 1]     2Fe(S)+O 2 (g)=2FeO(s)  (1)
     [Chemical Formula 2]     2C(s)+O 2 (g)=2CO(g)  (2)
   
     
     
         3 . The method for producing the plated black heart malleable cast iron member according to  claim 1 , wherein the particle projection treatment is one of shot blasting, shot peening, sand blasting, and air blasting. 
     
     
         4 . The method for producing the plated black heart malleable cast iron member according to  claim 1 , wherein a period of time for performing the particle projection treatment is 3.0 minutes or more and 20 minutes or less. 
     
     
         5 . The method for producing the plated black heart malleable cast iron member according to  claim 1 , further comprising the step of, before the step of performing the graphitization, preheating the black heart malleable cast iron member at a temperature of 275° C. or higher and 425° C. or lower. 
     
     
         6 . The method for producing the plated black heart malleable cast iron member according to  claim 1 , wherein the step of performing the graphitization includes first graphitization that includes heating the black heart malleable cast iron member at a temperature exceeding 900° C. and second graphitization that is performed on the black heart malleable cast iron member at a start temperature of 720° C. or higher and 800° C. or lower and at a completion temperature of 680° C. or higher and 780° C. or lower. 
     
     
         7 . The method for producing the plated black heart malleable cast iron member according to  claim 6 , wherein at least the first graphitization in the step of performing the graphitization is performed in the non-oxidizing and decarburizing atmosphere. 
     
     
         8 . The method for producing the plated black heart malleable cast iron member according to  claim 1 , wherein the non-oxidizing and decarburizing atmosphere contains a converted gas generated by combustion of a mixed gas of combustion gas and air. 
     
     
         9 . The method for producing the plated black heart malleable cast iron member according to  claim 1 , further comprising the step of, after taking the black heart malleable cast iron member out of the flux, heating the black heart malleable cast iron member to a temperature of 90° C. or higher. 
     
     
         10 . The method for producing the plated black heart malleable cast iron member according to  claim 1 , wherein the flux is an aqueous solution containing a weakly acidic chloride. 
     
     
         11 . The method for producing the plated black heart malleable cast iron member according to  claim 1 , wherein the flux is an aqueous solution containing zinc chloride and ammonium chloride. 
     
     
         12 . The method for producing the plated black heart malleable cast iron member according to  claim 1 , wherein the step of performing the hot-dip plating includes a step of performing hot-dip galvanizing. 
     
     
         13 . The method for producing the plated black heart malleable cast iron member according to  claim 1 , wherein the black heart malleable cast iron member is a pipe joint. 
     
     
         14 . A plated black heart malleable cast iron member comprising a black heart malleable cast iron member and a plating layer formed on a surface of the black heart malleable cast iron member, wherein the plating layer is a hot-dip galvanized layer,
 the black heart malleable cast iron member has a work-affected layer on a cast iron surface thereof, and   the hot-dip galvanized layer contains a silicon oxide.   
     
     
         15 . The plated black heart malleable cast iron member according to  claim 14 , which is a pipe joint. 
     
     
         16 . The method for producing a plated black heart malleable cast iron member according to  claim 2 , wherein a period of time for performing the particle projection treatment is 3.0 minutes or more and 20 minutes or less. 
     
     
         17 . The method for producing a plated black heart malleable cast iron member according to  claim 2 , wherein the step of performing the graphitization includes first graphitization that includes heating the black heart malleable cast iron member at a temperature exceeding 900° C. and second graphitization that is performed on the black heart malleable cast iron member at a start temperature of 720° C. or higher and 800° C. or lower and at a completion temperature of 680° C. or higher and 780° C. or lower. 
     
     
         18 . The method for producing a plated black heart malleable cast iron member according to  claim 1 , wherein an area ratio of silicon oxide occupying the surface of the black heart malleable cast iron member after the particle projection treatment is 50% or more relative to an amount of silicon oxide present on the surface of the black heart malleable cast iron member before the particle projection treatment. 
     
     
         19 . The method for producing a plated black heart malleable cast iron member according to  claim 2 , wherein an area ratio of silicon oxide occupying the surface of the black heart malleable cast iron member after the particle projection treatment is 50% or more relative to an amount of silicon oxide present on the surface of the black heart malleable cast iron member before the particle projection treatment.