The Future of Stainless Steel - New Generation Grades of Ferritic Stainless Steel

Austral Wright Metals has introduced two new generation grades of ferritic stainless steel. 445M2 and AWM GP404GP(R) are in addition to older ferritic grades that have long been available.

Figure 1. Corrosion resistant pergola brackets

Different Grades of Ferritic Stainless Steel

Austral Wright Metals have responded to the rising price of nickel by offering the market sustainable alternatives to the familiar grades 304 and 316. After extensive research and consultation with premium Japanese steel mills, grades AWM GP404GP(R) and 445M2 were selected as alternatives to 304 and 316 respectively.

These grades are made with state of the art steelmaking technology to provide a safe choice. They have higher chromium content (at least 21%) than the grade replaced (18%), and they are guaranteed to have corrosion resistance at least as good, usually better. They don't contain nickel, so they are much more stable and lower in price.

Figure 2. AWM 404GPR is easily worked and can be applied to many applications

Characteristics of the New Ferritic Grades of Stainless Steel

They have the extra benefit all ferritic grades have of freedom from stress corrosion cracking and better atmospheric corrosion resistance (tea staining). Plus they behave like carbon steel in the workshop, so are easier to cut and form and give a better looking product.

These are 'new generation' ferritic grades, with extra low carbon and fully stabilised, so don't suffer the poor weldability and toughness of the more familiar ferritic grades, 430 and 409.

Ferritic stainless are words that are appearing increasingly frequently in stainless steel circles. The term applies to a group of stainless steels whose structure is ferrite, just like carbon steels. Such steels can possess excellent corrosion resistance, adequate ductility and are easily worked.

Like the more familiar austenitic stainless steels, they are not responsive to hardening by heat treatment, and in addition they are not hardened by cold work. This is a benefit in fabrication, since they have much lower work hardening than the austenitic stainless steels and behave like carbon steel.

Unlike traditional grades 304 & 316, AWM GP404GP(R) and 445M2 have a ferritic microstructure, more of the corrosion resisting element chromium and on top of that, they have no nickel. That gives AWM GP404GP(R) and 445M2 some big technical benefits over 304 & 316.

Ferritic grades AWM GP404GP(R) and 445M2 have excellent punchability, bendability and weldability, making them easier to fabricate than austenitic grades 304 & 316. The much lower rate of work hardening gives lower forming loads and less springback with less tool wear. AWM GP404GP(R) and 445M2 behave like carbon steel - cleaner cuts, less distortion, longer tool life - and cost savings in workshop. AWM GP404GP(R) and 445M2 are new generation stainless steels with equal or better corrosion resistance than the grades they replace. This guarantees safe performance over a long life span. All this with a significant cost advantage over the traditional grades 304 & 316.

Corrosion Resistance of Ferritic Stainless Steel

445M2 can be used as an alternative to grade 316. It is a high chromium (22%) Japanese ferritic grade with 1.1% molybdenum, and has equal or better corrosion resistance than grade 316 - a grade well known for its anti-corrosion properties.

Field trials have shown us that it has substantial corrosion resistance, and it is performing better than grade 316. Being ferritic, there are also cost savings because it is nickel-free.

Manufacturing of Ferritic Stainless Steel

The world stainless steel industry is increasingly turning to ferritic stainless steels as a solution to the unstable price of nickel. Ask Austral Wright Metals for the ISSF Publication "THE FERRITIC SOLUTION". The world-leading Japanese mills now produce twice as much ferritic stainless as austenitic stainless, and the rest of the world is rapidly catching up. This isn't a temporary situation, it's a shift in the way stainless steel is used, and Austral Wright Metals are leading the way in Australia.

Being ferritic also makes it easy to fabricate as the grade has less work hardening and less tool wear when compared to austenitic (nickel containing) stainless steels. Like all ferritic grades it is immune to stress corrosion cracking in chloride containing waters.

The grade is also easily weldable, and is not sensitised (loss of corrosion resistance), as some of the older ferritic stainless steel grades can be - as long as good practice is followed.

The grade has high thermal conductivity and a low thermal expansion, so it is quicker to weld with minimal tack welds required.

In addition to this, the ferritic grades do not have any nickel added during the manufacturing process. This helps to keep the cost lower and more stable in comparison to traditional grades of stainless steel.

Due to the ease of manufacture and less toolwear, we are starting to see increasing interest from manufacturers who use stainless steel in manufacturing, particularly if they are using punching or perforating as part of the process."

Features of the New Ferritic Grade Stainless Steel

Perhaps the most important aspect of ferritic grades is that their austenitic alternatives can be seen as options to their tried-and-true brothers.

It is important to understand that corrosion resistance in stainless steels is mainly dependent on the chromium and molybdenum contents of the various grades. In a nutshell, the higher the chromium and molybdenum content, the higher the corrosion resistance.

These new generation ferritic stainless steels provide a very cost effective alternative to traditional grades and we are experiencing strong demand.

Customer Case Study - Modern Industries and BHP Billiton Nickel Project

Modern Industries (WA) recently completed a major contract for BHP Billiton's Ravensthorpe Nickel Project. New Generation ferritic stainless steel 445M2 was used from Austral Wright Metals and Nisshin Steel, Japan for cladding insulation in a sulphuric acid plant at Ravensthorpe, WA.

Modern Industries have built an enviable track record in Australia and South East Asia providing construction and maintenance services to the mining, energy, oil and gas industries, particularly thermal and acoustic engineering solutions. Modern Industries Director Steve Skea evaluates his experience with 445M2:

"We were looking for a better alternative to the familiar marine grade stainless steel 316. Austral Wright Metals offered us 445M2, and convinced us of the better atmospheric corrosion performance. That was important, because although the Ravensthorpe project is 46 km from the ocean, so salt isn't the problem, we were insulating a sulphuric acid plant - and that's an arduous service for stainless steel.

We found the new grade very easy to work with - it saved us money in time and rework while we were pre-fabricating in our workshop in Perth. The extra precision we got in the pre-fabs was also a great help when we got out on site at Ravensthorpe, 500 km east of here.

We moved from 316 and 445M2 over the life of the job, so we got a fair comparison between the grades. We'll use it again for this sort of job - and anywhere else where we used to use 316."

445M2 is a modern stainless steel that does not contain nickel, unlike the better known austenitic stainless steel grades like 304 and 316. Instead, Nisshin Steel in Japan use modern, state-of-the-art vacuum processing steelmaking technology to produce a premium stainless steel without an expensive addition of nickel.

Figure 3. BHP Billiton's Ravensthorpe Nickel Project in WA. Modern Industries used 445M2 for the sulphuris acid plant.

Customer Case Study - Corrosion Resistant Filter Plenums for Centrifugal Air Blowers

WA company Jako Industries designed and manufactured five filter plenums for centrifugal air blowers supplying aeration tanks with filtered air at the Beenyup Wastewater Treatment Plant in WA. The plenums are in a very corrosive environment, so the choice of materials was critical.

After considering the older marine grade 316 stainless steel, Jako Industries selected the new generation ferritic marine grade 445M2 because of its corrosion resistant properties. It is also an easier material to work with.

Jako Industries was able to deliver an excellent finished product within the specified parameters, costs and time frames.

Figure 4. Jako Industries consulted Austral Wright Metals on the technical considerations of the application and were delighted that 445M2 was the chosen stainless steel.

Customer Case Study - UNSW Air Conditioning and Ventilation Systems

The Applied Science Building at the University of NSW is a landmark in the Eastern Suburbs of Sydney. This world-class multi-storey complex of research laboratories and lecture theatres has recently been extended and upgraded, including the air conditioning and fume extraction systems.

The new air conditioning and ventilation systems were placed on the roof. Management at the University were concerned that the upgrade would be a major disruption and not one they wished to endure more than once in a generation. They needed materials to be long lasting and require minimal maintenance.

As contractors on the project, Croydon Industries chose a new generation marine grade stainless steel. 445M2 was selected for the ducts on the roof, which are exposed to a marine atmosphere, created by surf at Maroubra Beach, just a few kilometres away.

Brian Clark at Croydon Industries says, "This was the first time we used 445M2, and we were a bit apprehensive - but it gave us no problems. It formed very easily, producing clean lines and well shaped panels with no flaws.

The stream diffuser sheet of perforated metal was a dream to make. The punching ran cool, the sheet came out flat, with very little burr and at a lower cost than the familiar 316. We're glad we opted to use 445M2, it's been a win-win for all".

Figure 5. The stream diffuser sheet construted with perforated 445M2 was a dream to make.

Customer Case Study - Cooking it up with Bertocchi

Bertocchi Smallgoods make the highest quality smallgoods - hams, bacon, salamis and other specialised continental smallgoods. The salted hams are cooked in ovens that create a steamy salty and corrosive atmosphere. The walls and ceiling of the factory are regularly cleaned, but the life of painted steel linings was too short for the high standards set by Bertocchi.

This is where stainless steel stepped in. The hardness and smoothness of stainless steel enable it to resist the adhesion of soils and bio-films, and the excellent corrosion resistance allows it to be easily cleaned and sanitised.

Austral Wright Metals supplied panels of grades 304, 316 and 445M2 to be trialed on the walls to find out which grade would produce the required results. After four months, Bertocchi Smallgoods chose the new generation ferritic grade 445M2 to line the factory - ceilings and walls. With superior corrosion resistance to grade 316, 445M2 resists the powerful cleaning agents used to keep the factory clean, as well as the hot, humid, salty atmosphere around the brine lines.

So far, Bertocchi has installed 10 tonnes of 445M2 0.7 x 1219 mm sheet with a 2B finish. The result? A clean, bright factory that's easy to keep that way. And Bertocchi intend to keep going until the entire factory is lined with 445M2 - if only they could find the time to do it !

Customer Case Study - Sharpline Trolleys

Sharpline Holdings recently used new generation ferritic grade AWM GP404GPR in high quality hospital food trolleys used throughout SE Queensland. The trolley is powered, so the environment is controlled. Meals stay hot in the heated compartments and the sweets stay cold in the refrigerated side. And all this in a large trolley that's easy to manoeuvre around small wards.

Sharpline Managing Director Simon Lines says "We have lots of experience with stainless steel, which is robust, looks good and is easy to clean - essential qualities for hospital equipment like these trolleys. We decided to give new generation ferritic stainless steel AWM GP404GP(R) a go for this job, our first time with the grade. It worked like a dream - it bends crisply, welds well, and enabled us to produce excellent trolleys with minimum fuss. Our customer is very satisfied, and we are enthusiastic about the prospect of more orders.

Customer Case Study - Shining Beacon to the Future of Stainless Steel

Auckland based company Metal Design Solutions handcrafted and installed the standing-seam roof made from 445M2 ferritic marine-grade stainless steel supplied by Mico Metals - Austral Wright Metals' sister company in New Zealand. Jan Alberts from Metal Design Solutions says,

"This is a very special roof and we were very excited about this project. We measured it, made the roof off site and then installed it in pieces - there's considerable finishing work done by hand.'

Paul Orsler from Mico Metals says, "445M2 ferritic stainless steel is an ideal alternative to traditional 316 and 316L, because it offers several benefits. One of its key advantages is its superior corrosion resistance due to the high (22%) chromium content."

"The concept we had in mind called for a shiny roofing material - something that had life to it - rather than a dull finish like zinc or a metal like copper that would weather and change colour,' says Jamie Simpkin. 'We chose 445M2 marine-New Zealand's tallest apartment building, the Sentinel beside Takapuna Beach on Auckland's North Shore, is like a shining beacon above Takapuna, the roof of the Sentinel apartment building on Auckland's North Shore, is finished in new-generation 445M2 ferritic marine-grade stainless steel supplied by Mico Metals.grade stainless steel because it gave us the right aesthetic and, when correctly maintained, it won't rust or discolour like other products.'

Ease of fabrication due to its ferritic microstructure, is another major benefit of 445M2, says Paul Orsler. As well as the microstructure aiding fabrication, 445M2 also has a special embossed surface finish, he says, which helps to lower the reflectivity and avoid glare issue.

'This ferritic microstructure means it behaves like carbon steel and can be roll formed just as you would with any powder-coated steel, but it's also fully weldable.' As with all ferritic grades, 445M2 is less dense than standard 316 stainless steel, which gives 3.5% more area per unit of weight. It also has lower thermal expansion and higher thermal conductivity so is less prone to distortion on welding and expansion in the heat of the sun.

And another key advantage of 445M2, especially on large-scale projects such as the Sentinel Apartments, is the upfront cost savings this product offers. Because it contains no nickel, depending on the current nickel price, it can offer significant savings when compared to standard marine-grade stainless steel.

Customer Case Study - Fujitsu & Stramit on Brisbane River

Update on the Fujitsu building: this was the first major building using 445M2 in Australia. Experience with 445M2 in Japan goes back to 1993, but the Fujitsu building was not completed until 2002.

Situated close to the Brisbane River, it has also been next to "the most polluted urban remediation site" in Brisbane for its entire life, as trucks have ferried away the contaminated soil from a century of industrial use - a gas works, wharfs, woolstores, council work depot, oil & fuel storage, timberyards, sawmills and shipyards. And as luck would have it, a record drought has sent little rain to wash off the corrosive dust that has settled all over the building - in Brisbane at the moment, they don't even wash the hire cars!

But the 445M2 has come through with flying colours. There is no tea staining, unlike some adjacent 316 handrails, which have already needed some remediation.

Figure 6. The Fujitsu Building has since received two Queensland Metal Building Product Design awards.

This information has been sourced, reviewed and adapted from materials provided by Austral Wright Metals - Ferrous, Non-Ferrous and High Performance Alloys.

For more information on this source, please visit Austral Wright Metals - Ferrous, Non-Ferrous and High Performance Alloys.