City Steel Heat Treating offers a full range of surface treatments to provide desired properties such as wear resistance, fatigue strength, and tensile strength. We can provide case hardening of steels with lower carbon content by Carburizing, or Carbonitriding. We offer Gas Nitriding to provide exceptionally hard surfaces on steel with very little risk of distortion. We can also provide selective Surface Hardening of steels with higher carbon content using our Induction Processes.

Annealing is a process involving heating and cooling, usually applied to produce softening of the metal to facilitate machining or forming operations. The term also refers to treatments intended to alter mechanical or physical properties, produce a definite microstructure, or remove gases. The temperature of the operation and the rate of cooling depend upon the material being annealed and the purpose of the treatment.
Full Annealing is a softening process in which steel is heated to a temperature above the transformation range, and after being held for a sufficient time at this temperature, is cooled slowly in the furnace to a temperature below the transformation range. Depending upon the alloy, temperatures for this process range from 1450°F to 1650°F. This process is typically only required for higher alloy steels, cast irons, and complex alloys.
Process Annealing, or sub-critical annealing, is usually applied to steel to soften the steel sufficiently to allow further processing, such as cold working or machining. The steel is heated close to, but below the transformation range, and then cooled. Temperatures for this process range from 1000°F to 1300°F, depending upon the alloy.
Stress Relief Annealing can be used to relieve internal stress from forming, machining, or welding in steel if further processing is not required. The steel is heated to about 1100°F and cooled.

Normalizing is a process in which steel is heated to a temperature above the transformation range and then cooled in still air. The purpose of the treatment is to obliterate the effects of any previous heat treatment and to insure a good result on re-heating for hardening or full annealing.

Hardening and Tempering are used to provide the best combination of hardness, strength, and toughness in a steel for a given engineering purpose. This treatment consists of heating the steel above the transformation range, holding for a long enough time to insure uniform temperature and solution of the carbon and alloying elements in an austenitic microstructure, followed by rapid cooling (quenching) to a fully martensitic structure. The cooling medium can be air, oil, water, molten salt, fluidised bed, or a gas such as argon or nitrogen. Upon completion of hardening, the steel is in it’s hardest but most brittle condition. It is necessary to perform a subsequent tempering or drawing or process to produce a softer but much tougher condition.

How it works

STEP 1

Parts are racked into a basket and placed into the furnace. The parts are racked to insure proper heating/cooling and to minimize distortion.

STEP 2

Parts are heated to a temperature above the transformation point, typically above 1500 degrees Fahrenheit. Parts are then quenched in oil to complete the hardening process. The parts are kept in a protective atmosphere during the entire process to prevent surface contamination or degradation.

STEP 3

Parts are removed from the furnace to continue to subsequent processing such as cleaning and tempering.

Tempering, sometimes called Drawing, is the process of re-heating hardened steels to reduce hardness and increase toughness. The tempering temperature depends upon the desired properties and the purpose for which the steel is to be used. Increasing the tempering temperature will reduce the hardness of the steel while increasing the toughness.