Basic Method of Carburizing

Basic Method of Carburizing

What is Carburizing?

Carburizing is one of the foremost wide used methods, of case hardening. the aim of case hardening is to extend the surface hardness of steel. 

During this method, the steel is introduced to a carbon-rich atmosphere and elevated to a temperature range of 850 to 950oC for a definite quantity of your time. due to this Carbon starts diffused into the surface layer of the fabric.  

The speed of diffusion depends upon the time and temperature zone at that the fabric is maintained. when carburizing material is quenched in order that the carbon is locked within the structure. 

The hardness is moderately enhanced, however, it will be hardened once more through the flame or induction hardening. It’s potential to carbonize solely a selected portion of the component(ie., gear tooth). The hardness achieved by Carburizing is fifty-five to sixty-eight HRC and also the carbon content within the surface layer is enhanced to 0.75 to 1.2%

The surface to not be carburized ought to be copper plated or covered with amphibole power mixed in clay cement.

Carburizing methods

They ar four basics methods of Carburizing that are widely used for case hardness. They are

1. Pack or Solid Carburizing
2. Gas Carburizing
3. Liquid Carburizing
4. Vacuum Carburizing

Pack or solid Carburizing

In this method, parts to be case harden is packed in  AN atmosphere with high carbon content like bone black, charcoal or metal carbonate. The parts area unit heated to temperature varies from

850 to 950oC in order that the carbon is diffused into the outer surface of the fabric.

The diffusion rate of carbon is relying upon the composition of the half, temperature and time. The outer surface of the fabric is hardened whereas the core of the fabric remains ductile. The case-hardens depth is just about zero.1 to 2 mm.

Normally this method is employed for soft steels with a carbon content of zero.2% or less that can not be hardened by easy heating and extinction.

Advantages of Pack Carburizing

• It is the best method of Carburizing
• Less cost of capital

 

Gas Carburizing

This method contains gases capable of forming atomic carbon at high temperature over components product of low-carbon steel. The gases wildly used for this method are monoxide, gas, a combination of paraffin, paraffin, and fuel. 

The parts to be Carburizing is placed in a chamber and heated to a temperature vary of 900 to 950oC. Then the Carburizing gas is competent the chamber for an amount of five to 10hours. Due To this high temperature, the carbon within the gas is diffused into the surface of the part and its case hardened.

When compare with pack Carburizing, this technique is simpler for Carburizing the parts. This technique will be employed in production.

Advantages of Gas Carburizing

1. It takes less time when put next with pack Carburizing technique
2. Control is a lot of correct to realize surface carbon content and case hardness
3. When compare with pack Carburizing, sophisticated form parts area unit carburized by this technique.

Liquid Carburizing

In this method, the steel parts area unit immersed in a very liquefied carbon-rich bathtub of molten salts. The molten salt contains a combination of sodium carbonate, common salt, and carbide. The reaction within the bath is

Basics of Carburizing and methods of Carburizing

This saturates the metal with carbon. the tub is replenished from time to time. The parts area unit immersed within the bath at a temperature of around 870 to 900oC. in order that the carbon is subtle into the surface of the steel. during this technique the time needed for carburizing the metal surface of zero.2 to 0.3mm in thirty-five to 55min.

Then the metal is then undergone fast extinction to lock the carbon within the structure. By this technique uniform case hardening is obtained when put next with different strategies.

Advantages of Liquid Carburizing

1. Uniform case hardening depth is obtained
2. Components area unit free from reaction
3. Soot isn’t fashioned on the surface of the part

Vacuum Carburizing

In the vacuum Carburizing technique, the part is placed terribly} very low-pressure vessel. The pressure within the vessel is maintained around zero.5 to ten bar. The gases employed in this technique area unit ethyne, gas and fuel. 

The part is heated to temperature vary from 900 to 1000oC then the gas is competent in the vacuum chamber. The gas decomposed and also the free carbon diffused into the part surface. Uniform Carburizing is obtained by this technique.

The problem oxidization is reduced in vacuum Carburizing thanks to low element gifts within the chamber.

Advantage of Vacuum Carburizing

• Carburizing time is extremely less when put next with different strategies.
• Uniform Carburizing is obtained by this technique.
• The oxidation of case hardening material is reduced.