Medium carbon steels and low alloy steels with enhanced machinability

Medium carbon steels and low alloy steels comprising:

• a) a tin bulk content of from about 0.02 to about 0.09 weight percent;
• b) a sum of the tin bulk content and a copper bulk content of no greater than about 0.10 weight percent;
• and
• c) a microstructure having a concentration of tin at ferrite grain boundaries in an amount of at least about five times the tin bulk content.

Medium carbon steels and low alloy steels comprising:

• a) an antimony bulk content of from about 0.02 to about 0.09 weight percent;
• b) a sum of the antimony bulk content and a copper bulk content of no greater than about 0.10 weight percent;
• and
• c) a microstructure having a concentration of antimony at ferrite grain boundaries in an amount of at least about five times the antimony bulk content.

A process for preparing medium carbon steels and low alloy steels, the method comprising the steps of:

• a) providing a steel containing MEA;
• b) developing ferrite grain boundaries in the steel;
• and
• c) concentrating the MEA at the ferrite grain boundaries;
• wherein the MEA bulk content of the steel is from about 0.02 to about 0.09 weight percent and the sum of the MEA bulk content and the copper bulk content is no greater than about 0.10 weight percent.

A process for preparing medium carbon steels and low alloy steels, the method comprising the steps of:

• a) providing a steel containing tin;
• b) developing ferrite grain boundaries in the steel;
• and
• c) concentrating the tin at the ferrite grain boundaries;
• wherein the tin bulk content of the steel is from about 0.02 to about 0.09 weight percent and the sum of the tin bulk content and the copper bulk content is no greater than about 0.10 weight percent.

A process for preparing medium carbon steels and low alloy steels, the method comprising the steps of:

• a) providing a steel containing antimony;
• b) developing ferrite grain boundaries in the steel;
• and
• c) concentrating the antimony at the ferrite grain boundaries;
• wherein the antimony bulk content of the steel is from about 0.02 to about 0.09 weight percent and the sum of the antimony bulk content and the copper bulk content is no greater than about 0.10 weight percent.