1. Steel is an alloy of iron and carbon.
2. Metal alloys with an average carbon content lend themselves well to high-alloy steels.
3. Martensite makes the metal hard, which leads to rupture of the weld after cooling.
4. The main indicator of the weldability of low-alloy steels is resistance to cracks after cooling of the metal.
5. ... are considered heat-resistant, cold-resistant and forging.
Ответ: 1. carbon; 2. high-alloy steels; 3. hard, rupture; 4. resistance; 5. forging.