Method for producing plated black heart malleable cast iron member, plated black heart malleable cast iron member, and pipe joint
Provided is a method capable of producing a plated black heart malleable cast iron member having a plating layer with excellent adhesiveness to a black heart malleable cast iron member, while having less burden on the environment, compared to conventional methods.
1. A method for producing a plated black heart malleable cast iron member having a plating layer on a surface of a black heart malleable cast iron member, the method comprising:
performing graphitization in a non-oxidizing and decarburizing atmosphere to form a ferrite layer on the surface of the black heart malleable cast iron member such that an oxide layer formed on the ferrite layer during graphitization has a thickness of 20 μm or less;
immediately thereafter, immersing the black heart malleable cast iron member obtained after the graphitization, in a flux for 3.0 minutes or more so as to remove the oxide layer;
heating the black heart malleable cast iron member taken out of the flux, to 90° C. or higher; and
performing hot-dip plating on the heated black heart malleable cast iron member.
2. The method for producing a plated black heart malleable cast iron member according claim 1 , wherein the non-oxidizing and decarburizing atmosphere is an atmosphere in which a partial pressure of oxygen is 10 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 a plated black heart malleable cast iron member according to claim 2 , wherein the non-oxidizing and decarburizing atmosphere contains a converted gas generated by combustion of a mixed gas of combustion gas and air.
4. The method for producing a plated black heart malleable cast iron member according to claim 2 , wherein the black heart malleable cast iron member is heated to 100° C. or higher and 250° C. or lower in the step of heating the black heart malleable cast iron member after being taken out of the flux.
5. The method for producing a plated black heart malleable cast iron member according to claim 2 , wherein the flux is an aqueous solution containing a weakly acidic chloride.
6. The method for producing a plated black heart malleable cast iron member according to claim 2 , wherein the step of performing the hot-dip plating includes performing hot-dip galvanizing.
7. The method for producing a plated black heart malleable cast iron member according to claim 1 , further comprising the step of preheating the black heart malleable cast iron member at a temperature of 275° C. or higher and 425° C. or lower before the step of performing the graphitization.
8. The method for producing a 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.
9. The method for producing a plated black heart malleable cast iron member according to claim 8 , wherein at least the first graphitization in the step of performing the graphitization is performed in the non-oxidizing and decarburizing atmosphere.
10. The method for producing a 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.
11. The method for producing a plated black heart malleable cast iron member according to claim 1 , wherein the black heart malleable cast iron member is heated to 100° C. or higher and 250° C. or lower in the step of heating the black heart malleable cast iron member after being taken out of the flux.
12. The method for producing a plated black heart malleable cast iron member according to claim 1 , wherein the flux is an aqueous solution containing a weakly acidic chloride.
13. The method for producing a plated black heart malleable cast iron member according claim 1 , wherein the flux is an aqueous solution containing zinc chloride and ammonium chloride.
14. The method for producing a plated black heart malleable cast iron member according to claim 1 , wherein the step of performing the hot-dip plating includes performing hot-dip galvanizing.
15. The method for producing a plated black heart malleable cast iron member according to claim 1 , wherein the black heart malleable cast iron member is a pipe joint.
16. The method for producing a plated black heart malleable cast iron member according to claim 1 , wherein the method excludes shot blasting.