Fuel for rockets, Zeppelins points toward green heat solution

It’s the most nettlesome problem in the quest to ditch fossil fuels: how can you get thousand-degree heat used in factory furnaces without pumping billions of tons of greenhouse gases into the atmosphere?

Heat-intensive processes like steelmaking and oil refineries are the starting point for production of everything from cars to life-saving medicines. But fueling their ultra-high temperatures requires burning coal, oil and natural gas. That makes industry responsible for about 20% of the carbon dioxide produced by humans and heating processes, and a bigger emitter than all cars and aircraft combined.

Under mounting pressure from protesters and climate-conscious investors, major industrial companies and governments are scrambling for a solution. They’re finding the most likely alternative may be hydrogen.

“Hydrogen has a big advantage,” said Markus Krebber, the finance director of RWE, Germany’s largest electricity generator. “You can use it in everything that’s difficult to electrify, from long distance trucks, barges, trains, maybe planes one day. It will be needed to decarbonize the power sector 100%.”

The gas is the world’s most abundant element and powered rockets and airships in the last century. It flames at 2 000 °C, while giving off no more than water vapor as exhaust.

The biggest problem with hydrogen is that it’s currently expensive to make — and most often is derived by splitting up molecules of natural gas, producing carbon dioxide in the process.

But that’s changing. Some of Europe’s most important names in energy and industry are racing to develop emissions-free ways of producing hydrogen. They’re focused on using electrolysis, where an electric current passes through water, splitting off hydrogen atoms from oxygen. That technology is well known and growing cheaper by the year. When it’s driven by renewable energy, it makes what the industry calls green hydrogen.

“It’s not witchcraft,” said Thomas Kolf, a professor at the Karlsruhe Institute of Technology. He’s the lead engineer on a project to convert green electricity into hydrogen and methane in the east German town of Falkenhagen. “The question is, how do you scale it up?”

A handful of blue-chip companies are leading the race to commercialize green hydrogen. They include utilities such as Uniper and RWE, machinery maker Siemens and industrial gas giant Air Liquide.

Having successfully piloted small-scale plants, they’re partnering with deep-pocketed oil majors such as Royal Dutch Shell to bring production to commercial scale. Governments are starting to think about the potential for green hydrogen and how to nurture its production and distribution.

The push to develop green hydrogen technology comes as Europe’s biggest industrial firms grapple with climate activists, politicians and investors demanding to know how they’ll slash emissions. A string of extreme weather events have pushed the environment to the forefront of public consciousness and is driving gains for green parties in elections.

“Cutting carbon in half by 2030 and reaching net-zero carbon before 2050 will help avoid the most catastrophic impacts of climate change on our economy, communities and environment,” said Mindy Lubber, board member at Climate Action 100+, which speaks for investors managing more than $35-trillion of assets. They want companies to act “more quickly” or risk being excluded from funds.

With measures such as improving insulation and training staff to curb energy use mostly exhausted, industrial firms are now looking at hydrogen to open up a deeper level of decarbonization. Steelmaker Thyssenkrupp AG in November started testing hydrogen in its Duisburg steel mill.

Europe’s energy industry is anticipating quick growth in the market for emission-free sources of the gas if only because consumers and governments are looking more closely at the issue. That’s pushing automakers, appliance manufacturers and others to seek emission-free sources of steel.

Even the world’s top natural gas exporter thinks a piece of the market will embrace hydrogen. Gazprom, the Russian company that supplies much of Europe’s gas, is trialing hydrogen at the Siberian town of Tomsk. Researchers are refining a process that heats the methane found abundantly under the frozen Siberian tundra into solid carbon and hydrogen gas. The carbon could go into chemical production and the gas used as an emissions-free fuel for heavy industry.

Gazprom’s embrace of hydrogen as a growing alternative to natural gas comes alongside President Vladimir Putin’s about-turn on climate policy. The president, who once joked that snow-covered Russia could use higher temperatures, this September signed the world’s fourth-largest greenhouse gas emitter to the Paris Agreement on climate change, citing more frequent freak weather events.

Gazprom’s engineers are also investigating whether they can insert hydrogen gas into natural gas pipeline networks.

“We think it will be a very good solution which will decrease emissions,” said Elena Burmistrova, the chief executive officer at Gazprom’s export arm.

In the woodlands skirting Falkenhagen, Uniper has successfully generated hydrogen from electrolysis powered by a wind turbine.

The gas could be transported to industrial companies or used to store energy generated by wind turbines, according to Axel Wietfield, head of storage at the utility. The project has caught the eye of oil major BP Plc. Both companies are working on a larger project that would provide 100 MW of energy, the size of a small power plant.

While the companies are all confident the project will work, question marks remain over whether hydrogen can ever be profitable.

“The problems with hydrogen are more economic than technical,” Wietfield said.

Those economic hurdles are daunting. Green hydrogen costs between $2.50 to $6.80 a kilogram to make due to the relatively high costs of renewable-powered electrolysis, according to analysis from BloombergNEF. Those costs would need to fall below $2 dollars in order to make renewable hydrogen competitive with coal, and to around 60 cents to beat the cheapest natural gas-based production, according to BNEF.

But those production costs are expected to tumble as electrolysis technology becomes more efficient and production is scaled up. Moves by European governments to increase the cost of carbon dioxide emissions could further tilt the economics of the market in favor of hydrogen.

European companies increasingly expect such fillips to come soon. German Chancellor Angela Merkel’s climate cabinet said in September green hydrogen would play a central role in “rebuilding” Germany’s industrial base as it moves to zero emissions by 2050.

There’s other hurdles. Manufacturing huge amounts of green hydrogen may strain electricity grids overwhelmed by the revolution in electric cars. It may be that production is concentrated in southern Europe, where the gas can be made most cheaply with abundant solar power.

But for now, hydrogen is offering the most plausible solution to one of the most intricate problems for the transition away from fossil fuels. Concerns about climate change will continue to rise, but so will demand for metals, building materials and chemically-derived medicines, all of which start with a powerful source of heat.

“If I have to make a bet for the future, hydrogen is definitely one of those,” said Fatih Birol, executive director at International Energy Agency, said in an interview with Bloomberg TV.


SAA faces regulator inquiry over sale plan

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South African Airways (SAA) officials will be summoned to a meeting with regulators next month to disclose details about talks with potential equity partners and give assurances that any deal won’t violate foreign-ownership laws.

Under the Air Services Licensing Act of 1990, airlines must be at least three-quarters owned by South Africans to operate a domestic service. That would prevent international operators from buying more than a 25% stake from the government, unless the rules are changed.

“We are going to be calling SAA to next month’s meeting to share with us what their plans are,” said Mike Mabasa, chairman of the Air Services Licensing Council, which regulates domestic aviation within South Africa. “If they are already in conversations with strategic equity partners we need to know what that entails.”

Finance Minister Tito Mboweni said last month the government is talking with potential investors in SAA, which is technically insolvent and reliant on bailouts and other forms of state support to survive. The carrier last week triggered a plan to cut 944 jobs to reduce costs – leading to an ongoing strike that started on Friday.

Two labor groups on Sunday said they are consulting with workers about intensifying the strike across the aviation industry after failing to reach a deal over wage increases and job cuts at the weekend. The National Union of Metalworkers of South Africa and the South African Cabin Crew Association argue that ending the outsourcing of services would help reduce costs.

“It is clear to us that the management of SAA is not prepared to do what is necessary to save the airline,” they said in a joint statement.

Ethiopian Airlines Group Chief Executive Officer Tewolde Gebre Mariam has said the continent’s biggest airline would consider taking a stake in SAA, a partner in the Star Alliance. Virgin Atlantic Airways founder Richard Branson has also indicated an interest.

“If some tough decisions need to be made, we’ll make them,” Public Enterprises Minister Pravin Gordhan said on Thursday. He’s previously said the company will need to remove unnecessary costs to attract a viable buyer.

Routes to some international destinations including London and New York had been due to resume Sunday night.

SAA’s ongoing battle with unions may prove decisive to the carrier’s survival, with an estimated R50-million of losses incurred with every day of strike action, and little in the way of leeway in terms of cash reserves. Labor groups are demanding a reversal of the plan to reduce the workforce by about a fifth on top of an 8% pay rise and other employment benefits.

“SAA pretends as if its service is indispensable, which is not the case,” because it has just a 20% market share, and other carriers can step in in the event of its demise, said Gerhard Papenfus, chief executive officer of the National Employers’ Association of South Africa. “This notion of indispensability, however, emboldens the trade unions to make unrealistic demands.”

Tlali Tlali, SAA’s spokesperson, didn’t answer calls to his mobile phone seeking comment.


SA’s Gina to lead trade and investment mission to Mozambique

South Africa’s deputy minister of trade, industry and competition Nomalungelo Gina will lead a group of business people on a mission to Mozambique later this month with the aim of increasing bilateral relations between the two countries, her department said on Monday.

The department is organising and funding the November 24-29 visit through its Export Marketing and Investment Assistance (EMIA) scheme whose objective is to develop export markets for South African products and services.

The department said trade with Mozambique, South Africa’s third largest trading partner on the continent, grew from R43.9-billion in 2013 to R52.4-billion in 2018.

South African companies, state-owned enterprises as well as small, medium and micro enterprises (SMMEs) have invested across a broad spectrum of sectors in Mozambique with 43 foreign direct investment projects recorded between January 2003 and March 2019.

These projects represent a total capital investment of over R90 billion, which is an average investment of R3-million per project with over 8 500 employment opportunities created, according to the trade department.

Gina said the upcoming mission was an ideal platform for South African companies looking to export value-added products and services and those seeking investment opportunities in Mozambique.

“The specific focus of the mission will be on designated industrial and infrastructure projects as envisaged in the memorandum of understanding on economic cooperation between the two countries,” she said.

“These include the liquefied natural gas projects in the Northern Cabo Delgado province, electricity generation, transmission and distribution systems, water supply systems, transport infrastructure such as ports, rail and roads and the industrial development zones.”

The projected economic boom associated with the development of the gas sector in Mozambique was expected to have multiple positive spin-offs for the rest of the economy, Gina said, adding that natural gas discoveries were attracting investments and providing numerous opportunities for South African firms looking to expand into the neighbouring country.


Transport union slams PRASA over escalating railway infrastructure vandalism

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The decision by the Passenger Rail Agency of South Africa (PRASA) to terminate contracts of 20 private security companies at the end of October has left railway infrastructure vulnerable to vandalism, says the United National Transport Union (Untu).

In a statement on Friday by Untu spokesperson Sonja Carstens, the union lays all manner of accusations at PRASA, saying “the leadership of Untu repeatedly warned the [PRASA] board that the decision [to terminate security contracts] exposed their staff and commuters and the assets of PRASA as the SA Police Service have never in the past came to the party.

“But the board disagreed and Untu told them the proof would be in the pudding.”

As the statement puts it, Untu has been inundated with videos of vandalism at various train stations across the country.

“Unfortunately, the result is massive damage to the infrastructure which is funded with taxpayers money and yet another devastating blow to PRASA employees who has to sit back and look at how their jobs are being placed at risk,” said Steve Harris, general secretary of Untu.

But, PRASA has hit back, saying they have already started deploying their own internal security personnel “while strategically planning with the rapid railway police and greater collaboration with other security partners”.

“PRASA can now report that the first tranche of deployments of the rapid railway police has been deployed in the Western Cape and Gauteng including law enforcement units and other security cluster divisions in the protection of commuters, staff and assets,” said spokesperson for the agency, Nana Zenani.

On the crackdown on the inexplicably high rate of crime bedeviling railway’s across the country, PRASA’s group CEO Dr Nkosinathi Sishi said: “We are bridging the gap between deploying our own security personnel and additional technology in ensuring that we remove the dependence on just personnel deployments.

“We will now be able to profile suspects and conduct the necessary investigations as well which was a strength we did not have previously.”


EPP advocates for real estate investment policy in Poland

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JSE-listed EPP has urged the Polish government to introduce real estate investment trust (Reit) legislation for the country to make it more open for investment.

COO Rafał Kwiatkowski believes the Polish property sector could be an excellent avenue for creating wealth and would be a good vehicle for people to invest their retirement savings.

EPP is the largest owner of shopping centres in Poland, but has witnessed the benefits of Reit legislation in South Africa, which was promulgated in May 2013.

The South African listed property sector has seen market capitalisation soar over the past two decades, rising from roughly R6-billion in 2000 to R300-billion currently.

Today, there are 32 Reits for investors to choose from, including diversified, retail, residential, office and industrial and speciality Reits. An increasing number of these now have property holdings in international markets.

“Polish citizens cannot invest in Reits because there is no legislation allowing for it.

“This would be simple legislation for the government to pass and would have a positive effect on the economy, especially now that Poland has been rated among the most developed countries by ratings agency S&P for a full year and, like the rest of the world, will have to deal with the economic fallout from trade wars and slowdowns in neighbouring economies,” Kwiatkowski points out.

He adds that Poland is still among the nations that are best poised to avoid negative growth or a recession.

While the Polish government has room to make adjustments in debt levels and is taking actions to stimulate consumer spending, there is some simple legislation that would have a very positive effect that it could do right now – Reit legislation.

Reits offer a means for everyday investors to invest in commercial real estate. When an investor buys shares in a Reit, they are getting small portions of real estate held in a portfolio managed by a corporation that is publicly traded.

It allows investors to own a share in investment-grade properties on the same basis as if they had bought the properties directly, with the added benefit of value created through active, professional management.


Packaging solution proves successful

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Since polymer supplier Vesconite Bearings introduced a minimum of two layers of corrugated cardboard packaging around each of its dispatched polymer bushings and rods, the company has had no returns from breakages, owing to transportation.

The company instituted this as a packaging standard after a complaint by a customer led it to investigate its packaging policies.

Vesconite Bearings then decided that – if stock items could not be packed into rigid tube-like cores – rods and bushings would be placed in corrugated board, with the ends folded and taped for protection.

Rods and bushings would be further wrapped in corrugated cardboard, so that cardboard would provide additional packaging.

For airfreight packaging, the package would be included in a box where it weighed less than 20 kg and secured to a pallet if the box or set of boxes weighed more than 20 kg, to ensure easy handling.

The company believes that this set of packaging policies ensures customer satisfaction since corrugated cardboard – with an arched paper that fits between two liners – can carry a range of weights, protect against moisture, and is a sustainable, recyclable packaging solution.

“We have entered a new era in which you never get any returns as a result of breakages during transportation,” says Vesconite Bearings stores manager Martin Nyathi.

He notes the company’s packaging prevents cracking and breaking so that customers receive their orders intact.


Trio makes for steely supply

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Three of South Africa’s most prominent companies in the stainless steel supply chain are completing a substantial supply to a gold mine in the Southern African Development Community.

The project entails the supply of 250 t of grade 2 304 stainless steel for the manufacture of ten tanks – the largest of which measures 12 m in diameter and 12.7 m in height.

The proudly 100% Africa-to-Africa supply chain includes raw materials being supplied by stainless steel manufacturer Columbus Stainless, while the material processing and manufacture is being headed up by metals supplier Stalcor and the tank manufacture by steel fabricators Betterect.

Columbus Stainless local sales and market development manager Lerato Mashigo says the company supplied grade 2304 for the project, which is in duplex stainless steel.

She highlights that this family of stainless steel grades has a dual or mixed crystal structure consisting of relatively equal proportions of austenite and ferrite, which contributes to its high strength and superior corrosion resistance.

“Lean duplex, such as the 2304, is classified such because they are not highly alloyed. The grade predominantly comprises 23% chromium and 4% nickel, with manganese and nitrogen added for strength.”

Mashigo notes that Columbus Stainless has successfully produced various grades of duplex stainless steel – including 2001, 2304 and 2205 – since 2005 for the local and export markets.

“The challenge is addressing South Africa’s confidence in brand SA. South Africa needs to continuously support locally manufactured products, and realise that South African manufacturers have the skills and capabilities,” she adds.

Stalcor projects manager James Barnard highlights the success of “team South Africa” in terms of its ability to produce duplex stainless steel, manufactured for critical applications. This project will be a great reference point when promoting local products to the South African steel industry.

He explains that the coils were supplied as 20 t mother coils. This enabled the fabricator to get the optimum lengths required according to the product design. “The result of this was a decrease in welding and scrap, also resulting in time and consumables saved.”

The collaboration among the three companies assisted in mitigating not only shipping costs but also the extra five to six weeks of shipping delays, which would have been incurred had the client ordered the same product from an international supplier, adds Barnard.

He enthuses that Stalcor is a fully fledged stockist and supplier that supports clients. The company also does not compete against but rather works alongside respective markets in processing and fabrication. “We have the infrastructure, and the people who have a vast amount of experience and product expertise to easily navigate through a project of this size.”

“With this, we hope that South African mines, engineering procurement, construction management, as well as fabricators, would see the benefit of buying locally produced stainless steel,” says Barnard.

Betterect MD Nicolette Skjoldhammer tells Engineering News that some tanks were sent to site fully fabricated, while the large tanks were partially fabricated for final completion on site. “We saved the client between six and eight weeks of the total lead time using locally manufactured material.”

She suggests that there is still a wealth of expertise in South Africa and the industry needs to highlight and celebrate it to encourage growth in the sector.

“South African companies are perfectly situated to service growing local and export demand, especially since the steel industry is still one of the biggest employers and with an enormous amount of growth forecast in Southern and Central Africa,” concludes Skjoldhammer.


New membership structure set for stainless steel sector

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The Southern Africa Stainless Steel Development Association (Sassda) is at a turning point in its history as it gears up for the future with the introduction of a new tiered membership model that will launch in March 2020, says Sassda acting executive director Michel Basson.

As opposed to a standard flat-rate-type membership fee, which Sassda’s members had paid every year since the early seventies, the new structure offers a set of highly competitive membership packages, in terms of cost and, most importantly, inherent added value.

This means that membership is tailor-made for the specific requirements of each member and packed with the support and services required to grow the client’s business. The new membership fee structure is based on the member’s level of activity in the stainless steel industry. In most cases, this is based on the number of employees involved in the direct conversion of stainless steel and even ‘entry’ level membership holds the core services and added value synonymous with Sassda’s new approach. Sassda now offers a tangible value proposal to members and members will be able to not only get tangible value for the membership fee, but will be able to generate even more value through active participation in Sassda initiatives.

Basson asserts that being a Sassda member automatically offers the benefit of proven technical support and advice as well as access to world-class training. Sassda helps clients market their business, while effectively lobbying and promoting export potential, essentially increasing the client’s influence and networking opportunities.

“The new membership model follows months of researching and benchmarking the new membership packages against the best in the world to come up with a set of options that are in touch and in tune with local business needs. Membership will be very similar to that of the Australian association with a proven track record of effectively serving the industry for more than a decade,” highlights Basson.

He adds that, for its members to be fully informed of the new developments, staff are currently travelling across South Africa, conducting face-to-face meetings with each member company to inform them of Sassda’s vision for 2020.

Moreover, Basson says it is Sassda’s goal to continue developing the local industry by assisting it in converting more stainless steel tonnage into world-class products.

“This, in turn, will stimulate technology use, people development and job creation,” he adds.

The South African stainless steel industry has aligned itself with the notion of Industry 4.0 and understands that local manufacturers need to be at the forefront of any developments, Basson points out.

“This can only help South Africa to remain globally competitive, which is a drive that has become increasingly important amid a stagnating South African market.”

Moreover, it is critical to find alternative markets for organisational growth.

Basson asserts that, in years past, many companies conducted manual operations in their production departments. This has changed to outsourcing specialised services such as laser or high-definition plasma cutting and other highly technical operations.

Currently, many companies regard activities such as computer numerical control cutting and bending, even robotic welding, as a commodity, with most competitive workshops now equipped with these technologies.

“It is believed that this will now be followed by a wave of higher skill level training, since adding this type of technology to production facilities creates a requirement for new positions, such as operators and programmers.”

Basson points out that job creation and training are a couple of the many challenges that the stainless steel industry faces. Other challenges include the industry’s heavy reliance on continuous and affordable energy and growing more competitive in a global market. Sassda assists in mitigating these challenges by making industry- and market-related intelligence available, assisting members through training and technical support and continuously lobbying government in this regard.

In the past year, Sassda has worked on the Steel Master Plan initiative with the Department of Trade, Industry and Competition (DTIC), as well as other relevant government departments.

Following a meeting with Trade and Industry Minister Ebrahim Patel in August, an industry input document was submitted to the Minister last month, addressing the needs of the industry, as well as suggestions on the best way forward.

Subsequently, Patel noted at the fifth Southern African Steel and Engineering Indaba, at the Industrial Development Corporation Conference Centre in Sandton, held on September 12 and 13, that all submissions to the DTIC were being scrutinised and that a plan of action would be released in the next couple of months.

In the document, Sassda conveys its hopes to open communications with various African countries, including Kenya, Tanzania, Zambia and Mozambique, to extend outward-bound trade channels.

Sassda has historically found that the outward-bound trade missions – together with the DTIC’s support and endorsement – are the most effective way of obtaining business leads and enquiries.

Basson notes that the National Pavilion in Kitwe, Zambia – where Sassda has made significant inroads in building relationships with business in the area and government bodies – has requested that Sassda offer some of its training courses and other technical services in Zambia.

“In future, we would like to expand our network into other African countries in a similar vein.”

Sassda has had a very good working relationship with the Department of Trade and Industry – developed through years of interaction – which it continues to strengthen now that the department has morphed into the DTIC, and believes that its constructive participation in government initiatives contributes to the wellbeing of the stainless steel industry, Basson concludes.


Medium-term investment buoying stainless steel industry

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Despite a marked downturn in the global stainless steel industry, there are a few medium-term developments on the horizon for Southern Africa, notes research institute Afriforesight Commodities chief commodity economist Nathan Musson.

“There are glimmers of hope in terms of investment in Southern Africa’s stainless steel industry.”

There are four noteworthy investments in this regard.

The first comprises the Chinese-supported $10-billion integrated metallurgical complex mooted for Limpopo’s Musina-Makhado Special Economic Zone (SEZ), which would include three-million-tonne-a-year stainless steel capacity. The timeline for the plant execution is unclear currently as work on the supporting infrastructure and power generation capacity is expected to continue for the next few years.

Secondly, a reindustrialisation project by stainless steel and alloy manufacturer Lamergyre Alloys is in the feasibility stage and planned for the Eastern Cape’s Coega SEZ.

“If all goes according to plan, construction will begin in 2021, with Phase 1 of production resulting in 2.5-million tonnes a year of stainless steel and 1.5-million tonnes a year of alloy steel from about 2024,” suggests Musson.

The third investment involves the world’s largest stainless steel producer Tsingshan, headquartered in China, which is constructing a fully integrated, two-million-tonne-a-year stainless steel mill, in Zimbabwe, after recently signing a $2-billion agreement with the Zimbabwe government. Musson enthuses that this project’s investment potential is up to $10-billion, if the full scope is realised.

Stainless steel manufacturer and supplier Columbus – currently the only local stainless steel producer – has made minor investments to support its existing operations in recent years, with the construction of a new ladle furnace currently also under way.

Global Influence

In referring to the global stainless steel market, Musson says weak global demand growth and fast-growing Asian capacity are headwinds the local industry has “very limited potential to influence”.

Globally, the stainless steel industry is struggling, with a broad slowdown in economic growth, caused by the ongoing US-China trade disputes, he mentions.

While China’s transitioning to a service-based economy has led to a fundamental moderation in economic growth in recent years, its various trade concerns are compounding this effect.

A major ramp-up in low-cost capacity in Asia, primarily in Indonesia – where government will implement policies to restrict the export of nickel ore to promote the domestic beneficiation capacity –is adding to current industry woes.

This slowdown in global demand, coupled with accelerating supply growth, has resulted in lower prices and tighter profit margins for stainless steel producers globally, leaving marginal or inefficient operations at risk.

Musson points out that the local industry must deal with slower global growth and lower export demand – the latter not only because of weaker economic activity but also increasing competition – as well as very weak local demand growth, coupled with limited investment in large-scale metal-intensive projects.

This pressure is also amplified by steadily rising manufacturing costs, especially for electricity and labour, although the industry does still have the current advantage of mining and beneficiating the necessary chrome and manganese raw materials locally. Musson says chrome, nickel and to a lesser extent manganese are the key raw materials required to produce stainless steel.


Correct use of consumables makes a good weld

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Branded welding supplier Unique Welding has significantly upgraded its range of stainless steel consumables to improve weld performance to combat a market flooded with low-quality imported stainless steel welding consumables, Unique Welding CEO Nazmi Adams tells Engineering News.

In addition, Unique Welding has partnered with renowned welding expert John du Plessis from welding and metallurgical consulting service provider Spesmet Technology to support clients with welding technology.

“The successful welding of metals, such as stainless steel, can help mitigate expensive base material waste and, subsequently, prevent welding failures, which would be significantly more costly in the long term,” says Du Plessis.

He notes that welding austenitic stainless steel successfully is not more difficult than welding mild steel; however, it is important that the welder follow the rules and standards set out by the industry.

Du Plessis says these rules include using symmetrical double-sided weld joints instead of single-sided joints. “It is also imperative to always weld in a symmetrical fashion while keeping root gaps to a minimum size.”

Moreover, one must keep bevel angles to the minimum angle stipulated for the weld, as well as heat input in the weld required for fusion and penetration, and finally use back stepping as a welding technique.

Stainless Steel Structure

Du Plessis explains that stainless steel is not a single alloy, but rather a large range of different alloys that can be categorised into austenitic stainless steels, ferritic stainless steels, martensitic stainless steel, duplex stainless steels and the precipitation-hardening stainless steels.

Notably, the most widely used alloy group in industrial applications is austenitic stainless steels.

To account for a better weld, the correct welding consumable grade must be used for each of the austenitic stainless steel grades, he emphasises. The austenitic stainless steels consist of the 200 and 300 types, with the latter the most widely used.

There are matching consumables for most of the grades, the exceptions being grade 304, which is normally welded with a 308-type consumable, and grade 321, which is normally welded with a 347-type consumable.

Consumables – which are your welding rods, contact tips, nozzles and diffusers – are either categorised as a straight consumable or carry a suffix. The suffix can be L (a low carbon alloy), H (higher carbon) or N (nitrogen bearing).

For shielded metal arc welding, the 15, 16 and 17 types are used. A 15-type electrode has a lime-based coating and is intended for direct current (dc) electrode positive polarity only. The slag covering is not as thick as that found on the 16- and 17-type coatings.

The weld bead is normally convex in a horizontal fillet weld, with excellent crack resistance. The 15-type electrode provides the best all positional weldability; however, the arc is harsher than the other types.

The 16-type electrode has a rutile-based coating and can be used with both dc and alternating current (ac) polarity. The weld bead in a horizontal fillet is almost flat, while the arc is much softer than the 15-type electrodes, with good all positional welding.

The 17-type electrode has a silica-rutile type coating, and can be used with dc and ac polarity. The additional silicon in the coating acts as a wetting agent, increasing puddle fluidity.

The 17-type electrodes produce a concave weld bead in a horizontal fillet weld and are often used for flat horizontal position welding. These electrodes have limited vertical welding capability. The arc is smooth and relatively soft when welding.

“Given the price difference between these types, the cheapest and often incorrect type is selected by the client or sold incorrectly by a supplier,” highlights Adams.

The austenitic stainless steels do not undergo phase transformation during the heating and cooling cycles during welding as do carbon and low-alloy steels.

Preheating is, therefore, not required to slow the cooling rate in the heat-affected zones to prevent the formation of hard brittle microstructures, such as martensite, which promote cracking.

Austenitic stainless steels are prone to weld metal cracking – hot or solidification cracking – during solidification of the weld pool.

Challenges when welding austenitic stainless steels include hot cracking, contamination, corrosion because of the welding and also distortion.

Adams concludes that a client must “carefully scrutinise the type of consumable, compare actual alloying compositions and consider the risk of weld rework before buying the consumable”.