Free-cutting steel and production method thereof and application of free-cutting steel in manufacturing keys

The invention provides free-cutting steel and a production method thereof and application of free-cutting steel in manufacturing keys. The free-cutting steel is prepared from the following chemical components in percentage by weight: 97.85-98.53% of Fe, 0-0.09% of C, 0-0.15% of Si, 1.10-1.40% of Mn, 0.04-0.09% of P, 0.33-0.42% of S and 0-0.2% of impurities, wherein the mass ratio of Mn to S is (3.6-4.2): 1. The free-cutting steel has certain strength, hardness and cutting property, can satisfy the free-cutting property in the process that the user manufactures keys and in the process of processing the keys as well as strength and hardness required by the keys, and is very suitable for manufacturing the keys. The production method comprises the following steps: initially smelting molten iron; refining by an LF furnace; continuously casting; and rolling steel strips. The production method is strong in process operability, good in controllability, stable in technology, low in production cost, good in economic benefit and easy for industrial production on a large scale.