What are the common steel grades covered in IS 13620?

The standard covers Commercial Quality (CQ), Drawing Quality (DQ), Deep Drawing Quality (DDQ), and Structural Quality (SQ) (Clause 4.1).

What does the coating designation 'Z275' signify?

It signifies a minimum total zinc coating mass of 275 g/m² on both surfaces of the sheet (Table 2).

What is the base material for this coated steel?

The base metal is typically cold rolled low carbon steel sheet and strip, often conforming to IS 513 (Clause 3.1).

Are there specified mechanical properties for Commercial Quality (CQ) grade?

No, CQ grade is not required to have specific tensile or yield properties, but a bend test and minimum elongation are specified (Table 3).

IS 13620

: 1993

Continuous Hot-Dip Zinc/Zinc-Alloy Coated Steel Sheet and Strip - Specification

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This standard specifies the requirements for continuous hot-dip zinc or zinc-alloy coated carbon steel sheets and strips. It details base metal grades, coating mass, dimensional tolerances, mechanical properties, and testing methods for materials used in construction, automotive, appliances, and general engineering.

Specifies the requirements for continuously hot-dip zinc or zinc-alloy coated steel sheet and strip.

Quick Reference Values

Minimum zinc coating mass (Z120)120 g/m² (total both sides)

Minimum zinc coating mass (Z275)275 g/m² (total both sides)

Minimum elongation for Commercial Quality (CQ) grade (t ≥ 0.6 mm)20%

Thickness tolerance for sheets (t < 0.60 mm)±0.05 mm

Thickness tolerance for sheets (0.60 ≤ t < 1.00 mm)±0.06 mm

Maximum Sulphur content in base metal0.040 %

Maximum Phosphorus content in base metal0.040 %

Practical Notes

The coating designation (e.g., Z120, Z275) refers to the total minimum mass of zinc in g/m² on both sides of the sheet, not the thickness.

Always specify the base steel grade (e.g., CQ, DQ, DDQ, SQ) along with the coating mass, as this dictates the material's formability and strength.

Surface finish (e.g., regular spangle, minimized spangle, zero spangle) and condition (e.g., skin passed, oiled) must be specified based on the end-use, especially for painting or aesthetic applications.