What is Hardening in Welding?

Hardening is a process of quenching steel from the austenitic temperature range so as to produce martensite or a hard structure. The purpose of hardening is to increase the strength and hardness of the steel so that it can better resist wear, abrasion, and impact. Hardening can also improve the weldability of the steel by increasing its toughness.

What is Hardening used for?

Hardening is often used in welding to improve the strength and hardness of the weld joint. The hardening process can also be used to improve the appearance of the weld by creating a harder, more polished surface. Hardening is typically performed more ductile steel is desired, the steel may be quenched in water or oil.

Types of hardening

Depending on the desired properties of the steel, different hardening methods may be used:

  1. Air hardening is a type of hardening that involves heating the steel to a temperature above its critical temperature and then quenching it in the air. This type of hardening is typically used for steels that cannot be quenched in water or oil, such as high-carbon steels.
  2. Nitrogen hardening is a type of hardening that involves heating the steel to a temperature above its critical temperature and then quenching it in nitrogen. This type of hardening is typically used for steels that cannot be quenched in water or oil, such as high-carbon steels.
  3. Water hardening is a type of hardening that involves heating the steel to a temperature above its critical temperature and then quenching it in water. This type of hardening is typically used for steels that are not as hardenable as air-hardening or oil-hardening steels.
  4. Oil hardening is a type of hardening that involves heating the steel to a temperature above its critical temperature and then quenching it in oil. This type of hardening is typically used for steels that are not as hardenable as air-hardening or water-hardening steels.
  5. Tempering is the process of heating the steel to a temperature below its critical temperature and then cooling it. The purpose of tempering is to reduce the brittleness that can occur during quenching. Tempering can also improve the ductility and toughness of the steel.

What is the difference between hardening and tempering?

  • Hardening is a process of quenching steel from the austenitic temperature range so as to produce martensite or a hard structure. The purpose of hardening is to increase the strength and hardness of the steel.
  • Tempering is the process of heating the steel to a temperature below its critical temperature and then cooling it.

Stick welding hardened steel

The most common type of welding process used for hardening is stick welding. Stick welding uses an electrode that is consumable, meaning that it melts during the welding process and becomes part of the weld.

Hardening code

When hardening is specified in welding, there is usually a code that specifies the type of hardening to be used. The most common codes are:

  • A – air hardening.
  • N – nitrogen hardening.
  • W – water hardening.
  • O – oil hardening.
  • T – tempering.

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Hardening (metallurgy)

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