Brake drum and method for producing the same

A method for producing a brake drum by fastening a friction member to an inner circumferential surface of a backup member formed of an Al alloy, said method comprising:

• a step of producing an Al-base composite material by causing a reinforcing material of metal nitride to contact magnesium nitride and causing the Al alloy to penetrate into the reinforcing material with at least part of the reinforcing material exposed as a metal part through reducing action of the magnesium nitride;
• and
• a step of forming, by extrusion, the Al-base composite material into a cylindrical member having projecting and depressed portions on an outer periphery thereof, an inner diameter of said cylindrical member constituting an inner diameter of said brake drum;
• a step of cutting said cylindrical member into a width corresponding to said brake drum, to thereby provide said friction member;
• and
• a step of setting said friction member in a casting mold and cast-enveloping the set friction member by the Al alloy functioning as said backup member.