Medium-carbon steel: grades, properties and alloy characteristics

Medium-carbon steel is a steel that contains no alloying elements and has 0.25-0.6% of carbon and constant impurities. This alloy is classified as a standard-quality steel, smelted in basic oxygen furnaces, and is considered inexpensive due to its relatively low production costs. Its mechanical properties are significantly inferior to other alloys.

This type of steel is also considered a hardening steel, meaning it requires additional heat treatment, including quenching and high-temperature tempering. Medium-carbon steel can be alloyed, which imparts unique mechanical properties. The addition of manganese increases the steel's strength and imparts high elastic properties; these properties are acquired after quenching, tempering, and sometimes normalizing. The addition of chromium and nickel increases strength, toughness, and other processing properties. Alloys of this class have deep hardenability.

Medium-carbon, low-alloy steel is used in mechanical engineering after heat treatment, hardening, and tempering. Some grades are also tempered and normalized. This allows for the manufacture of parts operating under relatively high friction conditions, where there are high vibration and static loads. Medium-carbon structural steel is successfully used for machine parts, but requires further refinement. It is used to manufacture dry-running brake clutches and parts subject to high friction loads.

Because this alloy maintains high hardness and excellent cutting properties for a long time, it is used to manufacture cutting tools. The silicon content increases strength while simultaneously reducing toughness, resulting in reduced hardenability of the parts. This type of alloy is used to make springs. The presence of chromium and manganese in medium-carbon steel also increases strength and wear resistance. The metal is weldable, making it suitable for creating durable welded structures or components.

Medium carbon steel grades

Medium-carbon steel grades are regulated by GOSTs: GOST 1050-75, GOST 380-71.

According to established standards, all alloys are divided into groups:

• A - supplied according to mechanical properties;
• B - by chemical composition;
• B – according to mechanical properties, but taking into account individual requirements for chemical composition.

Medium-carbon steel grades for group A have the following names:

• Art. 0;
• Art. 1;
• Art. 2;
• Art. 3;
• Art. 4;
• Art. 5;
• Art. 6;
• Art. 7.

If the alloy is boiling, the abbreviation “kp” is indicated, semi-killed – “ps”, in the absence of an abbreviation it should be assumed that the steel is killed.

Medium-carbon steel grades of group B are produced using converter, Bessemer and open-hearth methods.

When marking, the production method is indicated by a letter abbreviation:

• "M" - open-hearth;
• "B" Bessemer;
• "K" envelope.

For Bessemer steel group B, it is customary to produce only the following grades: BSt. O, BSt. 3, BSt. 4, BSt. 5, BSt. 6.

Medium-carbon steel grades of group B are produced using the converter and open-hearth processes. The following grades are accepted for open-hearth steel of group B: VMSt. 2, VMSt. 3, VMSt. 4, VMSt. 5. For converter steel of group B, the same grades are designated by the letter "K" (VKSt. 2, VKSt. 3).