Process for manufacturing hot-dip aluminized pearlitic malleable cast iron and black heart malleable cast iron products

Claim 3

A method as claimed in claim 1 wherein the target cast iron is a malleable pearlitic cast iron with lamellar cementite obtained from white cast iron, the bath temperature being 680*-950*C, the graphitizing annealing temperature being 900*-1,000*C and being applied for 8-16 hours, after which the casting and furnace in which it is inserted are cooled to 730*-880*C and then fast cooled to ambient temperature.

Claim 4

A method as claimed in claim 1 wherein the target cast iron is a malleable pearlitic cast iron with spheroidal cementite obtained from white cast iron, the bath temperature being 680*-950*C, the graphitizing annealing temperature being 900*-1,000*C and being applied for 8-16 hours, after which the casting and furnace in which it is inserted are cooled to 730*-880*C and then fast cooled to ambient temperature, and further comprising an additional annealing at a temperature of 650*-780*C for 0.25-10 hours.

Claim 5

A method as claimed in claim 1 wherein the target cast iron is a malleable pearlitic cast iron with spheroidal cementite obtained from pearlitic malleable cast iron with a lamellar cementite, the bath temperature being 680*-950*C, the graphitizing annealing temperature being 650*-750*C and being applied for 0.25-10 hours, after which the casting is cooled in water to an ambient temperature.

Claim 6

A method as claimed in claim 1 wherein the target cast iron is a malleable pearlitic cast iron with spheroidal cementite obtained from black heart malleable cast iron, the bath temperature being 680*-950*C, the graphitizing annealing temperature being 650*-800*C and being applied for 0.25-10 hours, after which the casting is cooled in water to ambient temperature.

Claim 7

A method as claimed in claim 1 wherein the target cast iron is a ferritic or pearlite-ferritic cast iron obtained from black heart malleable cast iron, the bath temperature being 680*-950*C, the graphitizing annealing temperature being 950*-1,000*C and being applied for 18-24 hours, after which the casting and furnace in which it is inserted are cooled to 730*-880*C and maintained thereat for 30-60 hours and then cooled to ambient temperature.

Claim 8

In a process for manufacturing hot-dip aluminized pearlitic malleable cast iron products with lamellar or coagulated cementite and also black heart malleable cast iron products, which are protected against corrosion and high temperatures by a hot-dip aluminum coating, the improvement comprising: a. hot-dipping castings of non-annealed white cast iron in a bath of aluminum or aluminum alloys at temperatures in the range of 650*-950*C, for a period of time which is necessary for the immersed castings to obtain the bath temperature, the rates of immersing and removing said castings being between 0.5 and 10m/min., b. annealing the thus aluminized castings under oxidizing conditions, at a temperature in the range of 900*-1,000*C for a period of time of 40 hours to obtain graphitization of cementite and simultaneous homogenization of the aluminum coating structure, and c. slowly cooling the castings in a furnace to a temperature in the range of 730*-880*C, then cooling the castings in water, oil or air to the ambient temperature in the case of pearlitic malleable castings, or soaking at temperatures of 730*-880*C for a period of 30-60 hours and subsequently air-cooling the castings to ambient temperature in the case of black heart malleable castings.

Claim 9

In a process for manufacturing hot-dip aluminized pearlitic malleable cast iron products with lamellar or coagulated cementite and also black heart malleable cast iron products, which are protected against corrosion and high temperatures by a hot-dip aluminum coating, the improvement comprising: a. hot-dipping castings of non-annealed white cast iron in a bath of aluminum or aluminum alloys at temperatures in the range of 650*-950*C, for a period of time which is necessary for the immersed castings to obtain the bath temperature, the rates of immersing and removing said castings being between 0.5 and 10m/min., b. annealing the thus aluminized castings under oxidizing conditions, at a temperature in the range of 900*-1,000*C for a period of time of 40 hours to obtain graphitization of cementite and simultaneous homogenization of the aluminum coating structure, and c. slowly cooling the castings in a furnace to a temperature in the range of 730*-880*C, then cooling the castings in water, oil or air to the ambient temperature in the case of pearlitic malleable castings, or soaking at temperatures of 730*-880*C for a period of 30-60 hours and subsequently air-cooling the castings to ambient temperature in the case of black heart malleable castings.