Monthly Archives: October 2013

Differences between various Coated Steel Products

The most versatile, recyclable, environmental friendly metal in world – Steel, is an amazing metal. It has answers to all applications, products.

For Steel users, it might be a tough task in getting to know the different coated steel products that are available, their significance and selecting the right product that suits their application the best.

This article is aimed at helping a bit in knowing the differences between various coated steel products and their usage.

Basically there are four types of most commonly used metal based steel coated products

  1. Galvanised (GI)
  2. Galvannealed (GA)
  3. Galvalume (GL)
  4. Galfan (GL)
  5. Aluzinc – Not considered here as its usage is not very high.

The above mentioned designations viz., GI, GA, are normally used as a short form to designate the grades. This nomenclature can be different in different countries.

The basic purpose of coated steel is to prevent corrosion and enhance the surface life of base metal.  Zinc acts as a cathodic protection and prevents the base metal from corroding. Each of these coated steel has its own application, depending on where they are used and to which environment they would be exposed to.

The below table illustrates the basic differences between these metallic coated steel products in a simple way.

Table 1

S.No

Parameter

Galvanized

Galvannealed

Galvalume

Galfan

1 Coating

Zinc on Steel

Zinc on Steel.

Zinc reacts with Iron to form Zinc iron alloy

43.5% Zinc; 55% Aluminium; 1.5% Silicon.

95% Zinc, 5% Aluminium on Steel

2 Coating designation

Z

ZF

AZ

ZGF/ZA

3 Application

Ducting, roofing

Deep drawn Automobile parts/ outer panels

Metal Buildings/ Roofing

White goods/ some automobile parts

4 Corrosion resistance ( on a scale of 1 to 5)

3

2

4

5

5 Spangle on surface

Present

No. Matte finish surface

No

No

6 Method

Hot dipped continuous or Electrogalvainsed

Annealing after hot dipped galvanising

Hot dipped continuous

Hot dipped continuous

Galfan is the most recent invention of the above.

Galvalume and Galfan are registered and patented trademarks brands and only those manufacturers with license from the brand owners can produce and sell in these brands.

There are different grades within each variety of above products based on

  1. Strength of the Steel
  2. Coating Mass – Amount of coating
  3. Surface protection (Oiling, chemical passivation, organic passivation)
  4. Surface Quality

Coated Steel is normally designated with a combination alpha-numeric characters.  The below example would help identify the grade from such designations.

Designation:

Coated steel are normally designated as follows

Grade of steel + coating + spangle designation + surface quality + surface treatment.

Just to give an example let us consider the grade,

DX53D ZF140 MBC

DX53D – Deep Drawing grade (European Standard).

ZF – Galvannealed

255 – Coating mass

M – Mini spangle

B – “B” type surface Quality

C – Chemical Passivation.

American and European Standards are most commonly used to designate the grades of coated products.

Color coated steel (Pre-painted steel) is normally on base material of GI, GL. They are designated as PPGI and PPGL. Products of GI and GL when sold without color coating or pre-painting, they are referred as “Bare” GI or “Bare GL.

Pre-painted Galvanised iron (PPGI) & Pre-painted Galvalume (PPGL). PPGL is the famous of the two.

There is one more coated product available in market called “Aluzinc” & “Aluminized Steel”.  These are not considered here, as their demand is not significant compared to the other types mentioned here.

Happy Steeling!

Steel Import Regulation in India

 

India being a net importer of steel is fairly an open & WTO compliant market for many countries to trade its steel products.

For the past year and a half, many must be pondering over the announcements of BIS (Bureau of Indian Standards) on regulation for steel imports. Though some of them in the trade are fairly apprised of the regulation, it can still be a jinx for many.

This article helps in understanding this steel import regulation in India, which is BIS approval

Owing to concern on the quality of steel being imported, there have been some initiatives to prune on the quality front, to have a check on the inflow of inferior quality and to maintain quality standards.

BIS, a government regulatory body has made it mandatory for all the steel companies (manufacturers) to get themselves approved and registered under BIS, to sell steel in India.

These regulation necessitates all steel mills wanting to export its products to India to apply for the BIS registration, along with all requisite documents, and have the mill audited.  BIS registration can be a fairly time consuming process and companies applying for it should already have this in mind.

It should also be noted that not all steel products come under the gamut of BIS regulation.

I have divided the list to flat and long products and highlighted the products that fall under BIS and have also enlisted the products that are exempt of it.

BIS is Mandatory for following Products:

Flat Products:

  1. Hot Rolled Coils – Carbon Steel –  All dimensions- SS400, S235,275,355,40,500,etc.,
  2. Hot Rolled plates -Medium & high tensile structural steel – SS400, S235,275,355,400,500 etc.,
  3. Boiler quality carbon steel plates – Intermediate and high temperature – SA 515, 516, gr 60, 65, 70 all equivalent of it viz., P235NH, GH, P265 GH etc., – All dimensions.
  4. Cold Rolled Grain Oriented
  5. Cold Rolled non grain oriented –  Fully processed ( Watt loss not exceeding by 5.3 watt/kg or 1.5 Tesla/50Hz)
  6. Cold rolled non grain oriented  – semi processed ( Watt loss not exceeding by 5.3 watt/kg or 1.5 Tesla/50Hz)
  7. Plain & corrugated Galvanized coils/ sheets

The initial notifications exempted thickness > 80 mm and < 6mm from BIS. But subsequent notifications have made BIS mandatory for these dimensions as well.

In general all Hot rolled carbon steel flat products comes under this regulation.

All Alloy Steel flat products does not fall under BIS.

Following Flat products are exempt of BIS:

  1. All Cold rolled products, other than electrical steel mentioned above.
  2. Galvannealed
  3. Galvalume (bare)
  4. Galfan
  5. Aluzinc
  6. All pre-painted steel
  7. Aluminized steel
  8. Tin Plate
  9. Stainless Steel –  Coils /  Sheets –  Hot and Cold Rolled. 

Long Products & Semis:

Following long products fall under BIS regulation

Similar to Flat products all carbon steel semis (irrespective of dimension) are subjected to BIS regulation

  1. Ingots
  2. Billets
  3. Blooms
  4. Slabs
  5. Re bars  8 mm and above
  6. Structural grade wire rods and wires
  7. Beams –  610 <Depth <= 1016 mm
  8. Columns – 305 <size <= 356
  9. Angles –  between 50x50x4 to 100x100x8

Following Long products are exempt from BIS:

  1. Pipes/ tubes (ERW, Seamless, CDW)
  2. Alloy steel semis –  Billets, Blooms, Slabs, Ingots.
  3. Alloy steel bars ( hexagons, square, flat, rounds, octagons)
  4. Alloy steel wire rods and wires
  5. Stainless steel bars ( flat, round, square,hexagon, octagon)
  6.  Re-bars less than 8 mm.
  7. Bulb Flats.

Having gone through the products that does/ doesn’t fall under BIS, there can be a question of what is the definition of alloy steel and what is the minimum alloying content required to qualify as an alloy steel.  The definition of alloy steel according to Indian customs is given below,

Definition of Alloy Steel:

If any of the following alloying element is greater than or equal to below mentioned level, the steel will fall under alloy steel category.

Steel not complying with the definition of stainless steel and containing by weight one or more of the following elements in the proportion shown:

–        0.3% or more of aluminium

–        0.0008% or more of boron

–        0.3% or more of chromium

–        0.3% or more of cobalt

–        0.4% or more of copper

–        0.4% or more of lead

–        1.65% or more of manganese

–        0.08% or more of molybdenum

–        0.3% or more of nickel

–        0.06% or more of niobium

–        0.6% or more of silicon

–        0.05% or more of titanium

–        0.3% or more of tungsten (wolfram)

–        0.1% or more of vanadium

–        0.05% or more of zirconium

–        0.1% or more of other elements (except sulphur, phosphorus, carbon and nitrogen), taken separately.

The initiative from BIS to dissuade the import of inferior quality is undisputable, but looking at the time taken to get the BIS registration, one tends to ponder if this is a way to insulate the domestic industry from cheap imports.

No wonder India still continues to receive quite a good amount of hot rolled coils, plates, wire rods from China with Boron added which does not fall under BIS !!