To provide a method for surface treatment and heat treatment of a metal product by which hardness of a surface of the metal product is increased by increasing the carbon content in the surface of the metal product when projecting projection materials even when the metal product is composed of a metal such as SS400, aluminum and aluminum alloy which can not be hardened or is hardly hardened.

In the method for surface treatment and heat treatment of a metal product, a projection material 8 having the hardness equal to or more than that of the metal product is projected on the surface of the metal product 3 at the projecting rate of ≥ 100 m/sec, and the temperature in the vicinity of the surface is raised to A3 transformation point or higher, the metal product is composed of a metal which is hardly hardened such as SS400, aluminum and aluminum alloy. The projection material is coated with carbon, nickel, cobalt or the like on its surface, or formed of a material mixed with a single metal or a plurality of these metals. The carbon content on the surface of the metal product is increased thereby.

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