Metal Corp Steel

Introduction

This guide is designed to assist in the purchasing of sheet and coil by highlighting the 4 common areas where discrepancies can occur. These areas are;

1. Thickness
2. Coating Weights
3. Gross Weight Billing
4. Sheets per Tonne.

The result of any errors in these areas can be directly related to possibly using the incorrect material for the requirement and incurring costs or paying for material that has not been billed in the correct manner.

Use of these guidelines will assist in minimizing any inaccuracies.

1. Thickness

Steel thickness is where most confusion occurs.

Base Metal Thickness.

When ordering sheet metal the material should be ordered in metric thickness (not imperial gauge) to two decimal places, nominating Base Metal Thickness (BMT) eg. 0.75mm
The applicable Australian Standard (AS/NZ 1365) states that "the specified thickness shall be the thickness of the steel base which is the thickness required for design purposes".
The coating thickness is only relevant in determining the amount of corrosion protection. If it has been included in the steels thickness measurement the base steel will be thinner and therefore the product will not have the expected strength. Or example, a 0.50mm base metal thickness product with a Z275 coating mass, is approximately 8% thicker that 0.50mm total coated thickness (TCT).
If the coating mass is known, the thickness of the coating can be deducted from the TCT (refer to Table 1), to establish the BMT.

BUYING TIP:
ALWAYS ORDER AND SPECIFY METRIC BASE METAL THICKNESS

2. Coating Weights.

Zinc, Zinc-Iron or Zinc-Aluminium alloy is applied to the steel base for corrosion protection. The simple rule is that, with Zinc, the degree of corrosion protection is in direct proportion to the coating mass.
Given that the protection of the product generally determines the "life" of the item, care must be taken in specifying what coating class is required. For example, a product with a coating mass of 180g/m ² in Zinc simply will not last as long as one with 275g/m ².
Coating class designators are often confused with the material strength in the product description. The coating class is generally indicated by the Z, ZF, ZS or AZ and usually follows the strength or grade designator in the product description.
Eg. G2 Z275 Indicates commercial strength galvanized with 275 g/m ² of coating.

BUYING TIP:
ALWAYS SPECIFY THE COATING CLASS OF THE PRODUCT

	TABLE 1 - Approximate Coating Thickness
	Coating Class (g/m²)		Approx. Coating Thickness (mm)
	ZS 30		0.01mm
	ZF 100		0.02mm
	Z200		0.03mm
	Z275		0.04mm
	Z350		0.05mm
	Z450		0.07mm
	Z600		0.09/ 0.10mm (2.00mm>)
	AZ150		0.05mm
	AZ200		0.06mm

3. Gross Weight Billing.

Coil should always be ordered, supplied and invoiced on a net mass basis, excluding any packing materials. Ensure that the weight of any pallets or packing material is not included in the invoice mass.
Some products carry both net and gross weight labels to assist with transport and storage.
However, material should only ever be billed at net weight. If there is doubt on the received mass, the coil should be weighed or failing that, the approximate weight can be calculated using this simple formula:

Coil mass (kg) =	6.16546 x width (mm) x [ OD² (mm) - bore² (mm) ]
	1000000

4. Sheets per Tonne.

There are two ways to order sheet:
(i)  Price per Sheet
(ii) Price per Tonne (with a nominal sheet count).

(i) Price per Sheet.

The price is quoted per sheet, the order is placed for a specific number of sheets and the Invoice is a straight multiplication of the number of sheets times the price per sheet.

(ii) Price per tonne

The price is quoted per tonne. The number of sheets per tonne is dependant on size, type and coating mass. The sheets per tonne should be agreed prior to acceptance of the order.
Therefore low tonnage rate does not necessarily equate to low rate per sheet. Check the sheets per tonne if quoted a tonnage rate for sheet. Use the formula below or refer to the sheet and coil calculator or Tables 4 to 9 for standard size sheets.
Use this formulas to calculate Sheets per Tonne.

M² / Tonne =	1000000
	DENSITY FACTOR X THICKNESS (MM) + CM

SHEETS / TONNE =

M² / Tonne ÷ WIDTH IN METRES ÷ LENGTH IN METRES

	TABLE 2 - COATING MASS FACTOR (CM)
	Coating Class (g/m²)		Coating Mass Factor
	ZS 30		70
	ZF 100		130
	Z200		220
	Z275		290
	Z350		370
	Z450		470
	Z600		650/ 680 (2.00mm>)
	AZ150		170

	TABLE 3 - DENSITY FACTOR = WEIGHT PER METRE³
	MATERIAL TYPE		FACTOR (DF)
	MILD STEEL		7850
	STAINLESS STEEL		8177
	ALUMINIUM		2710

		Table 4 Nominal Sheet Count per Tonne - Uncoated (46K PDF)
		Table 5 Nominal Sheet Count per Tonne - ZS 30 hot dipped zinc iron alloy coating, 30g/M² (73K PDF)
		Table 6 Nominal Sheet Count per Tonne - ZF 100 hot dipped zinc iron alloy coating, 100g/M² (79K PDF)
		Table 7 Nominal Sheet Count per Tonne - Z200 hot dipped zinc coating, 200g/M² (69K PDF)
		Table 8 Nominal Sheet Count per Tonne - Z275 hot dipped zinc coating, 275g/M² (69K PDF)
		Table 9 Nominal Sheet Count per Tonne - AZ150 hot dipped aluminium zinc coating, 150g/M² (67K PDF)

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