Tubes can receive a number of finishing operations to change the steel’s structure, grain size, tensile strength or mechanical properties.

Anneal

Annealing is heating uniformly to a temperature within or above the critical range, and cooling at a controlled rate to a temperature under the critical range.

The treatment produces a definite microstructure, usually one designed for best machineability. It is also used to; remove stresses; induce softness; and alter ductility, toughness or other mechanical properties.

Hot Bed Cooling

This is the standard process of air cooling the steel immediately following the rolling operation. The steel is transferred to a special table or hot bed that continuously advances the product across the bed. Steel that is hot bed cooled may require additional thermal treatment to obtain optimum machineability or required mechanical properties.

Normalize

The steel is heated uniformly to a temperature of at least 37°C (99°F) above the critical range, and then cooled in air to room temperature.

This treatment produces a recrystallization and refinement of the grain structure, and gives the product uniformity in hardness and structure.

Quench (Quench Hardening)

This process heats the steel uniformly to a temperature above the critical range and then cools it rapidly in a liquid medium.

Spheroidize Anneal

This special type of annealing requires an extremely long cycle. Spheroidize annealing is used to produce a globular condition of the carbide and maximum softness for best machineability or to maximize cold formability. 

Stress Relieve

Stress relieving is a final thermal treatment used when stress-free material is desired. It restores elastic properties and minimizes distortion on subsequent machining or hardening operations.

This treatment is usually applied on material that has been heat treated (quenched and tempered).

Normal practice is to heat to a temperature of 37°C (99°F) lower than the tempering temperature used to establish mechanical properties and hardness.

Temper

Tempering heats uniformly to a temperature under the critical range, holding at that temperature for a designated period of time and cooling in air. This treatment produces one or more of the following end results:

• Softens the steel for later machining or cold working (also referred to as a process temper).
• Improves the ductility and relieves stresses resulting from prior treatment or cold working.
• Produces the desired mechanical properties or structure in the second step of the double treatment.

Mill Anneal

This is a controlled cooling of the steel immediately following piercing. In some low and medium carbon alloy grades, this method produces the optimum hardness and microstructure for machineability.