Tips for selecting the right material for your steel tube

25 Oct 2023

Key Account Manager Jared Knapp explains how to select the right steel tube, from Industrial Tube Manufacturing’s various material offerings. It is common for our customers to ask us about the differences between the different steel materials utilised in Precision Tubing, as well as how each material is designed to meet a specific application.

Mild steel coils are manufactured into Precision Tubing using either CRA (Cold Rolled Annealed), HRPO (Hot-Rolled Pickled and Oiled), Pre-Galvanized Steel, or ACMS (Aluminised Steel) treatment. These have distinct types of base material with different properties and applications and are largely sourced from leading New Zealand and Australian mills.

Here are the key differences and some of the applications for each:

1. CRA (Cold Rolled Annealed) 

Applications:  Precision tubing, manufactured using CRA mild steel, is typically used for applications that require a higher grade surface finish for improved application of coatings, tight dimensional OD and ID tolerances (telescoping) and superior formability and ductility.  This can include domestic and commercial furniture, automotive products, shop fitting & displays,  fencing and gates, tooling, sporting equipment and healthcare products.

Manufacturing Process: CRA starts as hot-rolled steel, then undergoes cold rolling passes to improve dimensional accuracy and surface finish, and finally annealing, which relieves the internal stresses built up during the cold rolling process.  In this process, the cold rolled steel coil is batch annealed by heating above its recrystallisation temperature, soaking the steel at that temperature and then cooling it.

Properties: CRA typically has a smooth, bright surface finish, tight tolerances, and significantly improved formability and ductility compared to hot rolled steel.

We source this product from Bluescope Steel Australia and offer 1.2, 1.4, 1.6 and 2.0mm.

2. HRP (Hot-Rolled Pickled) 

Applications: Precision tubing, manufactured using HRP mild steel is used for applications that include outdoor structures, automotive roll cages, hardware, cargo barriers and racking systems.

Manufacturing Process: HRP starts as hot-rolled steel and undergoes pickling – which is a three stage/bath process using Hydrochloric Acid – and oiling to improve surface quality and prevent corrosion.

Properties: HRP maintains the inherent properties of hot-rolled steel, including a slightly rougher surface finish and less precise dimensions compared to CRA. It has the (application specific) advantage of typically achieving a 50% higher yield strength than CRA and a higher strength overall (UTS). It is often referred to as ‘Semi-Bright’.

Industrial Tube sources this product from New Zealand Steel (BlueScope) in Glenbrook in 2.0mm and 2.5/2.6mm.

3. Pre-Galvanised  

Applications: Precision tubing manufactured from Pre-Galvanised steel is used in many applications where corrosion resistance, tight dimensional tolerances and/or formability are important. This can include agricultural and horticultural, shade structures, outdoor furniture, playgrounds, conveyors and fencing.

Manufacturing Process: The GALVSTEEL™ product starts off as cold rolled steel, before entering the coating plant, where it is in-line annealed and hot-dip galvanised to the required specification. More information here: NZS Coating Plant

Properties: Similar to CRA, this product has excellent formability and ductility with tight thickness tolerances. The Z275 (275 g/m2) zinc coating on both sides provides a smooth and uniform spangled finish. Our induction welded tube has the weld area repaired with an in-line zinc spray during the milling process.

Industrial Tube sources this product from New Zealand Steel and offer 1.2, 1.6 and 2.0mm.

GALVSTEEL™ is a trademark of New Zealand Steel Limited

4. ACMS (Aluminised Steel) 

Applications: Precision tubing manufactured from Aluminised steel is used extensively in automotive exhaust systems due to its heat resistance and corrosion protection.

Manufacturing Process: Cold Rolled EDDS (Extra-deep drawing steel) is coated with aluminium-silicon alloy in an in-line hot dipped process comparable to Pre-Galvanised steel.

Properties: EDDS is low carbon steel with the highest formability, ductility, and drawability when compared to other drawing steels. The aluminium coating provides up to twice the heat resistance of zinc and performs well up to 677 °C.

Industrial Tube sources this product from either South Korea or Japan and we offer 1.6 and 2.0mm.

For further information please contact us today.

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