Steel Sheets

Sheet Metal Material Selection

Sheet metal material selection process is crucial part of product design. It affects part design, cost, manufacturing process and part performance. In this article we will discuss sheetmetal materials their advantages and limitations. 

Sheet metal material selection process can be divided into two parts.

  1. Selection of Sheet Thickness
  2. Type of Material

Following Factors affect the selection of sheet thickness and type of material.

  • Required Product Strength
  • Weight Constrains
  • Cost Constrains
  • Required Corrosion Resistance
  • Assembly Process 
  • Material Availability

Sheet Thickness

Sheet metal materials are available in standard sheet thickness. Enclosure sheet thickness depends on product size, weight and loads acting on it. Structural simulation is performed to calculate required sheet thickness. 

Sheet Metal Material

Various sheet metal material grades are available in the market. Sheets are manufactured using hot rolling or cold rolling operation. Type of rolling operation also affect sheet metal properties Material selection is done based on product requirements. This article covers commonly used sheetmetal materials.

CRCA (Cold Rolled Close Annealed Steel)

CRCA is cheapest available sheetmetal material. It is highly prone to corrosion. After annealing oil is applied on CRCA sheet to improve corrosion resistance for short duration (2 to 3 weeks). 

As per IS 513 (2008) various CRCA grades are given below.

Advantages of CRCA Material

  • Superior Surface Quality
  • Good Strength
  • Excellent Weld-ability and Dimensional accuracy
  • Low Cost
  • Deep Drawn and Extra deep drawn grades are also available

Limitations Of CRCA Material

  • Highly prone to corrosion
  • Final finish cost is high
  • High weight
Galvanized Iron (GI) Steel

GI sheets are Zinc coated CRCA sheets. Zn coating improves the corrosion resistance. GI sheets are available in ordinary (O), drawing (D), deep drawing (DD), extra deep drawing (EDD) grades.

Galvanized steel are available in various zinc plating thickness. For example 120gsm, 200gsm, 300gsm or 600gsm sheets. 200gsm stands for 200 gram zinc coating in one square meter area. GI sheets are available as per IS 277:2003 standard.

Advantages Of Galvanized Iron Sheets

  • Superior Surface Quality
  • Good Strength
  • Excellent Dimensional accuracy
  • Deep Drawn and Extra deep drawn grades are also available
  • Better corrosion resistance compared to CRCA sheets. 

Limitations of GI Sheets

  • Not recommended if welding is used as assembly operation.
  • High Weight
  • Higher cost compared to CRCA sheets
Aluzinc Steel

Aluzinc is Aluminium and Zinc coated steel sheets. AlZn coating improves corrosion resistance. Its micro-structure consists of approx. 80 %  aluminium and 20 % zinc‐rich phase with a thin inter-metallic layer. 

Aluminum in aluzinc coating provides additional aluminium barrier. Whereas zinc‐provides sacrificial protection against corrosion at cut edges.

Advantages of Aluzinc Steel Sheets

  • High Corrosion resistance and Strength
  • Superior Surface Quality and Excellent Dimensional accuracy
  • Deep Drawn and Extra deep drawn grades are also available

Limitations of GI Sheets

  • Welding is not recommended on Aluzinc sheets
  • High Weight
  • Higher cost compared to CRCA and GI sheets
Aluminium

Aluminium is second most widely used metal in the world. It is available in various grades.

Commonly used Aluminium grades is sheet metal industry.

  • 5052-H32 : Good Formability, commonly used sheet grade 
  • 5052-H34 : Fair Formability, excellent corrosion resistance & Welding characteristics
  • 1050-H14 : Good Weldability
  • 6061
  • 5251-H22 : Applications in marine environments

Advantages of Aluminium Sheets

  • Low  Weight
  • High weight to Strength ratio
  • Excellent corrosion resistance
  • Good Thermal and Electrical Conductivity
  • Recyclable

Limitations of Aluminum Sheets

  • Aluminum is three times costlier than CRCA
  • Weldability is not good

Stainless Steel Sheets (SS)

SS is a corrosion resistant alloy steel containing more than 10.5% chromium. Stainless steel offers good corrosion resistance due to naturally occurring chromium-rich oxide film formed on the surface of the steel. 

Commonly used stainless steel grades in sheet metal industry:

  • SS-304
  • SS-304-L
  • SS-304-H
  • SS-316

Advantages Of Stainless Steel

  • Excellent corrosion resistance
  • Ease of fabrication
  • Food grades are available
  • Good Weldability
Limitations of stainless Steel Sheets
  • High Cost
  • Limited finish options are available

Summery

Properties CRCA GI Aluzinc Aluminium Stainless Steel
Strength Good Good Good Low Very Good
Weight High High High Low High
Corrosion Resistance Low Low Good High Very High
Weldability Very Good NR* NR* Good Very Good
Cost $ $ $$ $$ $$$
Note : NR* = Not Recommended : Welding on pre coated sheets will remove coationg on welded area. That results in reduction in corrosion resistance.

Conclusion :

To sum up, variety of sheet metal material grades are available. Depending on product application and cost material is finalized. We recommend you to also check sheet metal design guidelines.

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