Process for producing a balance wheel for a timepiece

A process for producing a balance wheel of a timepiece comprising a serge, a hub and at least one arm connecting the hub to said serge, the hub and the arm being made of a metal alloy, and the serge being made of a second material having a density that is greater than the density of said metal alloy of which the hub and the arm are made, said process including the following steps:

• a) making a mold in the negative shape of the balance wheel;
• a′) inserting a serge or serge parts made of a material that has a density higher than the density of said metal alloy into the mold;
• b) obtaining a metal alloy that has a thermal expansion coefficient of less than 25 ppm/° C. and is able to be in an at least partly amorphous state when it is heated to a temperature between its glass transition temperature and its crystallization temperature;
• c) putting the metal alloy into the mold, said metal alloy being heated to a temperature between its glass transition temperature and its crystallization temperature so as to be hot-molded, and over-molding the serge or the parts of the serge so as to mold a balance wheel with inserts;
• d) cooling said metal alloy so as to obtain a balance wheel with inserts;
• and
• e) releasing the balance wheel obtained in step d) from its mold,
• wherein the process includes a step for over-molding flexible centering components in the hub.