How to do the Stainless Steel Selection for your Application

Due to the tremendous advancement of the material science, there are many verities of stainless steel available in market. And you as a design engineer may be getting confused as which one to use

What is Stainless Steel?

  • Stainless steel is a kind of alloy steel in which considerable amount of chromium (Cr) is present apart from iron, carbon and the other alloying elements. The chromium percentage is important in stainless steel as this chromium upon reacting with the oxygen of the atmosphere creates the chromium oxide and this chromium oxide is primarily responsible to protect the steel from rust.
  • As per “AISI” the minimum amount of chromium requires to call an alloy steel as stainless steel is 4%. However, most of the stainless steel available in market consists of more than 10% chromium.

Impacts of Some Basic Alloying Elements to the Properties of Steel

The presence of the following elements in stainless steel will impact your stainless steel material selection according to applications. Why? Look below:

  • Chromium (Cr): Increase corrosion resistance.
  • Manganese (Mn): Increase ductility, wear resistance and high temperature strength.
  • Nickel (Ni): Increase impact strength and toughness and corrosion resistance.
  • Molybdenum (Mo): Increases marine and acidic corrosion resistance.
  • Vanadium (V): Increase the creep and the impact resistance.
  • Silicon (Si): Increase elasticity and acid resistance.
  • Sulphur (S): Increase machinability.
  • Boron (B): Increases the hardenability means your hardening effect reach to the higher depth in presence of boron.

Which Grade of Stainless Steel You Should Choose

The AISI grades (adopted in SAE as well) of stainless steels are widely followed across industry for dealing with stainless steel. Below are the few very popular stainless steel grades used across the industry:

  • Grade 303:

Alloying elements – Cr, Ni, S

Application:

– Where lot of machining need to be performed on the material.

–         The component made from the material won’t be used in corrosive environment.

–         Nuts, gears, bolt etc.

  • Grade 304:

Alloying elements – Cr, Ni

Application:

– Suitable for the components require forming.

–         Moderate corrosion resistance.

–         Kitchen sink, dairy and distillery equipments.

  • Grade 316:

Alloying elements – Cr, Ni, Mo

Application:

–  Good corrosion resistance.

–   Costly.

–   Good for formed components.

  • Grade 430:

Alloying elements          – Cr

Application:

– Good for acidic and chemical resistance.

–   Less corrosion resistance.

  • Grade 410:

Alloying elements – Cr

Application:

– Good for machining application.

–         Cheaper.

–         Less corrosion resistance.

Conclusion

The main factors for the stainless steel material selection according to applications are the alloying elements and the crystalline structure. While considering a stainless steel for any application you must consider the properties of the stainless steel grade as well as the cost.

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