Method for producing brake drum and a brake drum

1. A brake drum manufacturing method, wherein the method comprises:

forming a brake drum shell;

forming a structural layer inside said brake drum shell; and

forming a friction layer inside said structural layer;

wherein forming said structural layer comprises heating said brake drum shell being heated to 800° C.˜830° C.; and

while spinning said brake drum shell on a centrifugal casting machine, molten steel or iron are poured into said brake drum shell to form said structural layer.

2. A method for producing brake drum as claimed in claim 1 , wherein forming said friction layer comprises:

cooling said structural layer down to a temperature between 1350° C. and 1400° C.; and

while spinning said brake drum shell on a centrifugal casting machine,

pouring 1400° C.˜1430° C. molten iron containing an appropriate amount of Mo or other alloying element being poured into said structural layer to form said friction layer as an abrasion-resistant cast iron friction layer.

3. A method for producing brake drum as claimed in claim 2 , wherein forming said brake drum shell comprises forming an inner side surface of said brake drum shell into the raised pattern.

4. A method for producing brake drum as claimed in claim 3 , including, after the roll extrusion, applying an anti-oxidation treatment to the inner side surface of said brake drum shell.

5. A method for producing brake drum as claimed in claim 1 including post-process machining work on an inner surface of the cylindrical brake drum friction layer.

6. A method for producing brake drum as claimed in claim 1 , wherein said structural layer has a thickness of 3 mm˜4 mm at its thinnest point and said braking friction layer has a thickness of 4 mm˜5 mm.

7. A brake drum manufacturing method, wherein the method comprises:

forming a brake drum shell;

forming a structural layer inside said brake drum shell; and

forming a friction layer inside said structural layer;

wherein forming said brake drum shell includes:

molding a high-quality steel sheet into round piece with a hole in the middle, then placed on a suitable die, and extrusion stretched by a press machine into a bowl-shaped semi-finished shell for the brake drum;

forming the bowl-shaped semi-finished brake drum shell in a suitable die into a cylindrical semi-finished shell, and shaping an inner side surface of said shell to have a raised pattern; and

the cylindrical brake drum shell being subject to roll extrusion to make the cylindrical wall wavy.

8. A method for producing brake drum as claimed in claim 7 including post-process machining work on an inner surface of the cylindrical brake drum friction layer.

9. A method for producing brake drum as claimed in claim 8 , wherein said structural layer has a thickness of 3 mm˜4 mm at its thinnest point and said braking friction layer has a thickness of 4 mm˜5 mm.

10. A brake drum comprising:

a brake drum shell;

a braking structural layer arranged inside said brake drum shell; and

a braking friction layer inside said structural layer for braking;

wherein said brake drum shell has a raised pattern on its inner surface and said structural layer has a receiving groove accommodating to said raised pattern; and wherein:

three different metallic materials are used for three-layer construction of the shell, the structural layer and the friction layer are made of different molten metallic materials cast within the steel shell with steel or gray iron for the structural layer and a Mo-containing, abrasion-resistant alloy cast iron for the braking friction layer so that atoms from these two adjacent but different metallic materials inter-diffuse across an interface to form a solid fusant or an inter-metallic compound, thereby generating a very strong metallurgical bond.