--- --- Annealing quenching and tempering

One. Types of annealing

1. Complete annealing and isothermal annealing

Also known as full annealing recrystallization annealing, generally referred to as annealing, the annealing is mainly used for sub-eutectoid composition of carbon steel and alloy steel casting, forging and hot-rolled profiles, sometimes used for welding structures. Usually often as some non-heavy parts of the final heat treatment, or as a pre-heat treatment of certain artifacts.

2. Spheroidizing

Ball annealing is mainly used hypereutectoid carbon steel and alloy tool steel (such as manufacturing cutting tools, measuring tools, molds used steel). Its main purpose is to reduce the hardness to improve machinability, and hardened to prepare for the future.

3. Stress relief annealing

Stress relief annealing, also known as low-temperature annealing (or tempering), which is mainly used to eliminate annealing castings, forgings, welded parts, hot-rolled, cold-drawn pieces of residual stress and the like. If not eliminate these stresses will cause steel after a certain time, or deformation or cracks in the subsequent machining process.

II. Quenching, the cooling medium is the most commonly used salt, water and oil. Brine hardening of the workpiece, easy to obtain high hardness and smooth surface, not prone to hardening of the soft spot is not hard, but it is easy to make a serious deformation of the workpiece, and even cracking occurred. The oil is used as quenching medium applies only to the stability of supercooled austenite over a relatively large number of small-sized steel or hardened steel workpiece.

III. The purpose of tempering steel

1. Reduce the brittleness, to eliminate or reduce stress, the presence of steel after quenching great stress and fragility, if not tempered tend to make steel parts deformation or cracking.

2.
To obtain the desired mechanical properties of the workpiece, the workpiece after quenching and high hardness brittleness, in order to meet the different performance requirements of the various parts, can be adjusted by appropriately tempered with hardness, brittleness is reduced to give the required toughness, plastic.

3. Stable workpiece dimensions

4. For certain alloy steel annealing difficult softened quenching (or normalizing) is often used after tempering, the steel carbide appropriate aggregation reduces the hardness to Liqie cutting processing.