Metal working method and metal workpieces by it

Using the tailored blank material as a material, its features can be further utilized, setting the boundary of the portion not part of the predetermined heat treatment it is easy, and simplifies the equipment and process control required for the metalworking to provide a metal working method and which according to the metal workpiece can. Metalworking method, previously joined the temperature temperature is relatively low metal material by raising the temperature is relatively high metal material and infrared heating by infrared heating, and bonding to form an integrated metal material, wherein integrated metal material is simultaneously and entirely infrared heating, in the integrated metal material in the infrared heating, to a predetermined temperature to the temperature temperature is relatively high portion corresponding to the predetermined heat treatment after reaching the temperature the temperature is relatively low portion is completed the infrared heating before reaching the predetermined temperature, comprising a heating step.