Products for the protection of continuous cast moulds for cast-iron pipes

1. Powder product for the protection of centrifugal casting molds used for the manufacture of cast iron pipes, comprising a mixture of:

at least one inoculating alloy;

at least one strongly reducing metal that is volatile at the temperature of liquid cast iron, the at least one strongly reducing metal being in the form of at least one non-ferrous alloy, and being present in an amount of 0.3 to 18% by weight of the product; and

optionally inert mineral powder.

2. Product according to claim 1 , wherein the at least one inoculating alloy comprises a mixture of a plurality of inoculating alloys.

3. Powder product for the protection of centrifugal casting molds used for the manufacture of cast iron pipes, comprising a mixture of:

at least one inoculating alloy;

at least one strongly reducing metal that is volatile at the temperature of liquid cast iron; and

optionally inert mineral powder,

wherein the at least one strongly reducing metal comprises magnesium present in an amount of between 0.5 and 2% by weight of the powder product.

4. Product according to claim 1 , wherein the at least one non-ferrous alloy contains less than 10% by weight of Fe.

5. Product according to claim 4 , wherein the at least one non-ferrous alloy is an SiCa alloy containing, by weight:

Si 58-65%; Ca 27-35%; Fe 2-7%; Al 0.4-2%.

6. Product according to claim 5 , containing between 15 and 40% by weight of said SiCa alloy.

7. Powder product for the protection of centrifugal casting molds used for the manufacture of cast iron pipes, comprising a mixture of:

at least one inoculating alloy;

at least one strongly reducing metal that is volatile at the temperature of liquid cast iron; and

between 0.2and 15% by weight of an inert mineral powder.

8. Product according to claim 7 , wherein the inert mineral powder is selected from the group consisting of calcium fluoride, magnesium fluoride and mixtures thereof.

9. Process for manufacturing a powder product for the protection of centrifugal casting molds used for the manufacture of cast iron pipes, comprising at least one inoculating alloy, at least one strongly reducing metal that is volatile at the temperature of liquid cast iron and inert mineral powder, comprising forming a powder premix of the at least one strongly reducing metal and the inert mineral powder, and mixing the powder premix with the at least one inoculating alloy in powder form,

wherein the at least one strongly reducing metal constitutes 15 to 60% by weight of the premix.

10. In a process for molding cast iron comprising bringing molten cast iron into contact with an inside surface of a centrifugal casting mold,

the improvement comprising protecting the mold by applying to the inside surface a powder product comprising at least one inoculating alloy and at least one strongly reducing metal that is volatile at the temperature of the molten cast iron, before bringing the molten cast iron into contact with the inside surface of the mold, the at least one strongly reducing metal being present in an amount of 0.3 to 18% by weight of the product.

11. Process according to claim 10 , wherein the at least one inoculating alloy comprises a mixture of a plurality of inoculating alloys.

12. Process according to claim 10 , wherein the at least one strongly reducing metal is an element in column II of the periodic table of elements.

13. Process according to claim 12 , wherein the at least one strongly reducing metal is an element in subgroup IIa of the periodic table of elements.

14. Process according to claim 13 , wherein the at least one strongly reducing metal is magnesium or calcium.

15. Process according to claim 14 , wherein the product contains between 0.5 and 2% by weight of magnesium.

16. Process according to claim 10 , wherein the product additionally comprises between 0.2 and 15% by weight of an inert mineral powder.

17. Process according to claim 16 , wherein the inert mineral powder is selected from the group consisting of calcium fluoride, magnesium fluoride and mixtures thereof.

18. In a process for molding cast iron comprising bringing molten cast iron into contact with an inside surface of a centrifugal casting mold,

the improvement comprising protecting the mold by applying to the inside surface a powder product comprising at least one inoculating alloy and at least one strongly reducing metal that is volatile at the temperature of the molten cast iron, before bringing the molten cast iron into contact with the inside surface of the mold,

the at least one strongly reducing metal being added in the form of at least one non-ferrous alloy which is an SiCa alloy containing, by weight:

Si 58-65%; Ca 27-35%; Fe 2-7%; Al 0.4-2%.

19. Process according to claim 18 , wherein the product contains between 15 and 40% by weight of said SiCa alloy.

20. Powder product for the protection of centrifugal casting molds used for the manufacture of cast iron pipes, comprising a mixture of:

at least one inoculating alloy;

at least one strongly reducing metal that is volatile at the temperature of liquid cast iron, the at least, one strongly reducing metal being in the form of at least one non-ferrous alloy; and

optionally inert mineral powder,

wherein the at least one non-ferrous alloy is an SiCa alloy containing, by weight:

Si 58-65%; Ca 27-35%; Fe 2-7%; Al 0.4-2%.

21. Product according to claim 20 , containing between 15 and 40% by weight of said SiCa alloy.