Tips for selecting the right material for your steel tube

How can we improve the aesthetic of coatings? How do we extend the life of the product in an outdoor environment? How do we stop the steel splitting when performing tight radius bends? Where is your steel sourced from?

These are some of the questions often asked when Industrial Tube customers are searching for the right material for their product. Sales Manager, Jared Knapp, has written an overview of the options and explains some of the key differences and applications for the main materials offered by Industrial Tube Manufacturing.

Mild steel is cold-formed into our Precision Tubing using one of the following base materials:

CRCA (Cold Rolled Close Annealed),
HRPO (Hot-Rolled Pickled Oiled),
Pre-Galvanized Steel, or
ACMS (Aluminised Steel).

Each type of steel has distinct properties and applications as outlined below and are primarily sourced from leading mills in New Zealand and Australia.

1. CRCA (Cold Rolled Close Annealed)

Applications: Precision Tubing, manufactured using CRCA mild steel, is typically used for applications that require a higher-grade surface finish for improved application of coatings, precise dimensional OD and ID tolerances and superior formability and ductility. This can include domestic and commercial furniture, automotive exhausts, shop fitting & displays, fencing and gates and medical durables.

Manufacturing Process: The steel is hot rolled and pickled before undergoing cold rolling passes to improve dimensional accuracy and surface finish, followed by 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. Finally, the coil goes through the skin-pass mill.

Properties: CRCA has a smooth, bright surface finish, tight tolerances, and significantly improved formability and ductility compared to hot rolled steel due to a lower yield strength
and high elongation.

Industrial Tube sources CRCA mild steel from BlueScope Australia and stock 1.2, 1.4, 1.6 and 2.0mm. AS/NZS 1365:1996 (R2016), AS/NZS 1595:1998 (R2016) and ASTM A1008/A1008M – 21a

2. HRPO (Hot-Rolled Pickled Oiled)

Applications: Precision Tubing manufactured using hot-rolled strip is used for applications that include outdoor structures, automotive roll cages, hardware, cargo barriers, tools, fencing and racking systems.

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

Properties: HRPO maintains some of the inherent properties of hot-rolled steel, including less precise dimensions and a steel grey appearance. However, due to the additional processing, the surface is very suitable for powder coating and other finishes. The yield strength of the base material is typically 50% higher and elongation 30% lower than CRCA. It is often referred to as Semi-Bright.

Industrial Tube sources HRPO from New Zealand Steel in 2.0mm and 2.5/2.6mm. AS/NZS 1365:1996 (R2016)

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 continuously hot-dip galvanised to the required specification. More information here: NZS Coating Plant

Properties: Like CRCA, this product has good formability and ductility with tight thickness tolerances. The Z275 (275 g/m2) zinc coating 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 Galvsteel™ from New Zealand Steel and we stock 1.2, 1.6 and 2.0mm. AS/NZS 1365:1996 (R2016) and AS 1397-2021.

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 Aluminised steel from either South Korea or Japan and we offer 1.6 and 2.0mm. ASTM A 463-96a and JIS G3314-2022