Welding News Avesta in unique FLNG project. Läckeby Products is expanding. Avesta Welding s flux programme

Transcription

1 Welding News Some of the features in this issue... Avesta in unique FLNG project Läckeby Products is expanding Avesta Welding s flux programme How to weld fully austenitic steels: Part 2

2 Welding News As the year draws to its close Looking back over the past 12 months, 2012 can be summarised as an interesting year full of activities and innovation. As you have certainly read in previous issues of Welding News, our new duplex flux cored wire (Avesta FCW 2507/P100-PW) is taking the market by storm. It has been great fun following product development from concept to market success. During the year, we have also added a new brochure to our much appreciated How to weld series. The new addition, How to weld fully austenitic stainless steels, can also be read about in this Welding News. Please see part 2 of the article on welding fully austenitic steels. From time to time, I am asked how Avesta Welding, Böhler Welding Group and voestalpine fit together. This Welding News has a few details on the subject. It also touches on the strength and stability that springs from having the backing of a major corporation such as voestalpine. After an eventful twelve months, it is important to take a little well earned time for relaxation. We can then return even stronger for 2013 and Avesta Welding s celebration of its 80th year as a stainless steel brand. Naturally enough, this anniversary will be marked in various ways. Finally, I would like to wish all our readers a merry Christmas and a happy New Year. Remember that whenever stainless steel is to be welded, the natural choice is Avesta Welding 100% Stainless! Avesta Welding in unique FLNG project Floating liquefied natural gas (FLNG) is a new technology that will give access to offshore gas fields that would otherwise have been far too expensive or difficult to develop. Shell Prelude FLNG is the first plant of its kind in the world and its stainless steel pressure vessels will be welded using filler metals from Avesta Welding. Böhler Welding Group Asia Pacific has received an order for 48 tonnes of welding consumables from Doosan Engineering & Construction in South Korea. The customer has ordered 316L filler metals for welding cryogenic pressure vessels destined for Shell Prelude FLNG in Browse Basin, Australia. These vessels will be made in accordance with ASME section VIII, divisions I and II. Our products satisfied the demands in respect of performance at -196 C and the stringent requirements in respect of lateral expansion and elongation. Qualification of the welding procedures is now under way. The following welding methods and filler metals will be used: SAW Avesta 316L/SKR + Avesta Flux 807 FCAW Avesta FCW 316L/SKR Cryo TIG Avesta 316L /SKR MMA Avesta 316L /SKR Cryo Fredrik Hägg, marketing manager Avesta Welding and Böhler Welding Group Nordic AB Merry Christmas & a happy New Year! Photo: Shell Shell Prelude FLNG will be the world s largest offshore plant (488 m long, 74 m wide and a displacement of around 600,000 tonnes). Editorial Eva Söderberg, Tel: eva.soderberg@avestawelding.com Translations Transtext 2002 Cover picture One of the many water treatment plants worldwide supplied by Läckeby Water Group.

3 Welding News Läckeby specialists in water treatment When it comes to health and survival, few factors are as critical as access to clean water. However, this access is both limited and uneven. Hence the importance of cleaning, reusing and processing water correctly. Läckeby Water Group has great expertise in this art of environmental management in practice. Earth s water will not run out. It circulates in a never ending cycle and, in principle, the quantity is constant. Nonetheless, to make use of our life-maintaining water, it has to be clean. This quality is not always easily achieved. Quite simply, we have to be better at looking after the precious drops. An important element in this is research and development into improved methods of cleaning and reusing our water. Many years experience and own production Läckeby Products, part of the Läckeby Water Group, has long experience in the above matters. It has been in the industry since 1935 and is now the leader in water treatment and the processing of biological waste. Besides Läckeby Products, the group also has the Purac Puregas AB and Purac AB brands. Läckeby Products manufactures products for treating waste, potable and process water. Its range of both in-house developed and licensed products further includes products for sludge treatment. Design, development and manufacture of a number of the products that are most important as regards the functionality, operating cost and operational safety of all types of plant are taken care of in-house. The new pickling bath is a full 10 metres long. This enables immersion pickling of very large objects. Having almost 80 years in the industry, the company has gained expertise (not least through decades of contract operations worldwide) that has grown ever deeper with the passage of time. Good stainless steel relations Most of the company s products are stainless steel. For many years, it has been using welding and pickling products from Avesta Welding and Avesta Finishing Chemicals respectively. These are supplied via a single distributor, Svetsteknik i Kristianstad AB. Läckeby Products is one of our oldest and best customers, comments Magnus Christenson, sales engineer at Svetsteknik. We have a strong and close relationship. To top up its stocks of certain goods such as welding consumables, the preponderance of which come from Avesta Welding, we regularly visit

4 Welding News the company. If it needs anything between these scheduled visits, we can often supply at short notice. Of course, another advantage is that, if necessary, we can get expert technical support from Avesta Welding and Avesta Finishing Chemicals. It is truly great to see how Läckeby Products has developed over the years and how it is now further establishing its leading position in the industry. Product development increasingly important Every customer has its special requests and needs, explains Johan Andersson, Läckeby Products production manager. We are continuously trying to tailor our products to the customer s unique conditions. Product development is an ever ongoing process that, nowadays, is also largely governed by new requirements in environmental legislation. New pickling plant Everyone who welds stainless steel knows that post-treatment is necessary to ensure that welds are corrosion resistant. Chemical surface treatment, pickling, is the best method of achieving this. Läckeby Products has used pickling ever since the 1990s and, during this time, has gained great experience and knowledge in the area. When, earlier this year, operations were being moved and investment made in an entirely new pickling plant, it was only natural to turn to Avesta Finishing Chemicals (AFC) in Malmö. AFC is experienced in complete solutions for all types of pickling plants. Contact at an early stage has enabled AFC to contribute its know-how, practical advice and solutions all the way from planning and installation to start-up and monitoring. Spray pickled receiving units for the receiving, homogenisation and onward transport of waste. Läckeby Water Group Läckeby Water Group is an independent, privately-owned Swedish group that offers contracting, products and servicing for water treatment and biogas production. The corporation has been in the industry since It is established on three continents and, thus far, has completed contracts in 70 countries worldwide. With a turnover of around SEK 850 million, the group now leads its field. Read more at Immersion pickling in progress. AFC has many years of expertise in providing support for customers via the continuous checking of pickling bath operation (and making recommendations in respect thereof). This gives lower costs, even and high quality of pickled goods, documented process control and, through optimisation of the pickling process, reduced negative environmental impact. All this is included in AFC s pickling bath service concept, something that is attracting the attention of an increasing number of customers. Housing both production and pickling, the new plant is in Kalmar in premises that were formerly Bombardier s workshops. The pickling hall occupies roughly 350 m 2 and, at 10 x 1.8 x 2.1 m, the bath is suitable for immersion pickling even really large constructions. Thanks to its generous proportions, the hall additionally accommodates spray pickling. Subcontract pickling for other companies is now also possible. We are extremely pleased with the collaboration with Avesta Finishing Chemicals, states Johan Anderson. We will continue developing and making products that can contribute to what we call environmental management in practice. With our new pickling hall, we are well equipped for the future.

5 Welding News Avesta Welding s flux programme Avesta Welding offers three different fluxes for the submerged arc welding of stainless steels and nickel base alloys. All three are suitable for joint welding and cladding. Avesta 801 Avesta 801 is a Cr-compensated neutral flux that has a basicity index of 1.0. It is designed for welding with austenitic filler metals such as 308L/MVR and 316L/SKR. Avesta 805 This Cr-compensated flux has a basicity index of 1.7. It is intended for welding with all types of stainless steel filler metals from standard austenitic and duplex to nickel base alloys. Avesta 807 This is a neutral (non-cr-compensated) flux with a basicity index of 2.7. It is intended for welding with all types of stainless steel filler metals from austenitic standard steels to duplex and nickel base alloys. One advantage of an unalloyed flux is that the ferrite content in the weld metal will not differ significantly from that of the filler metal. Avesta 807 is widely used where impact strength requirements are high and the ferrite content must be controlled, e.g. 3 8 FN (WRC-92). This latter requirement is very difficult to satisfy using alloyed fluxes. Mechanical properties Mechanical properties do not differ drastically between these fluxes. However, broadly speaking, it can be said that impact strength using 805 and 807 is slightly better than it is when using 801. Despite the higher basicity of 805 and 807, their weldability is just as good as that of 801. Slag removal and weld finishes are both perfect. Submerged arc welding is a quick and efficient method for welding thicker workpieces. Welding flux Filler metals EN ISO Properties Avesta 801 Austenitic SA CS 2 Cr DC Low basicity, Cr-compensated Avesta 805 All SA AF 2 Cr DC High basicity, Cr-compensated Avesta 807 All SA FB 2 64 DC High basicity, non-cr compensated For optimum results, it is important to combine the right filler metal with the right flux.

6 Welding News Great interest in petrochemicals There is strong growth in the petrochemicals industry, not least in Asia, and interest is worldwide. These phenomena were clearly evidenced by the high attendances at the events Böhler Welding Group (BWG) recently held in India and China. Seminar in Mumbai, Indien In conjunction with India Essen Welding & Cutting 2012, BWG organised a petrochemicals seminar. Running from the afternoon to the evening in a nearby venue, it offered technical presentations by BWG engineers. The seminar brought together over 130 engineers and representatives from refinery, engineering and inspection companies such as Hindustan Petroleum, Technimont ICB, Uhde Heurtey and TÜV as well as from manufacturers such as Larsen & Toubro, ISGEC, Godrej, Petron, Virgo, Essar Heavy, etc. The petrochemicals conference in Zhuhai attracted some one hundred attentive participants. Despite a long day at the trade fair, the audience was lively and interested. The presentations were interesting and highly appreciated. Conference in Zhuhai, Kina There is also great interest and strong growth in petrochemicals in China. For this reason, BWG held a petrochemicals conference in Zhuhai from the 19th to the 23rd of November. The conference was primarily directed at institutions, constructors and end users. Attendance was good with some one hundred engineers accepting the invitation. As the petrochemicals industry uses a great deal of stainless steel, representatives from Avesta Welding also accepted an invitation to speak on this use. Böhler Welding Group at India Essen Welding & Cutting 2012 The fifth India Essen Welding & Cutting, held in Mumbai at the start of November, assembled 150 exhibitors from 13 countries and a total of 10,500 visitors. Böhler Welding Group (BWG) had its own stand. Here, BWG representatives from India were amongst those presenting the group s Avesta Welding, Böhler Welding, Soudokay, T-PUT and UTP brands. The stand was a fine platform for meetings and discussions with both present and potential customers and colleagues who had travelled from all parts of India. Part of Böhler Welding Group s trade fair team. From left to right: Roshan Rampure, Neeraj Tiwari, Satnam Singh, Jürgen Tuchtfeld, Jayshree Bardey, Abby Joseph, Chandrakala Parab, Volker Gross, Richard Jandl, Roland Haselsteiner, Alexander Thulin, Max Bergmayr, Amitabha Bhattacharya and Kamal Shah.

7 Welding News How to weld fully austenitic steels Part 2: Welding methods and techniques Characterised by their excellent properties, high-alloy fully austenitic steels are used for most applications where requirements are severe. This series of articles will give details of fully austenitic steels, their weldability and areas of use. The second part deals with welding methods and welding techniques. These steels have good weldability and can be welded using all common welding methods. However, compared with low-alloy austenitic steels, more care is needed when handling and welding fully austenitic steels. Welding methods, general All conventional welding methods such as MMA, MIG/MAG, TIG, SAW, FCAW, plasma and laser can be used to weld fully austenitic steels. Property requirements, positional weldability and productivity usually determine the choice of welding method. MMA welding is an excellent method, particularly for position welding, single-sided welding and where access is limited. Avesta Welding has a wide range of covered electrodes for fully austenitic steels: Avesta AWS EN Position 254 SFER (-17) R All positions 383 AC/DC -17 R All positions 904L-3D -17 R All positions 904L-PW -17 R Position welding P12-R -15 B All positions P B All positions P54-15 B Flat P16-15 B All positions Welding with rutile-acid electrodes (-17/R) is possible using both alternating and direct (DC+) current. However, direct current always gives better welding results. To give a weld metal with as low an oxygen content as possible (and thereby minimum oxides and inclusions), The chemical process industry is a typical area of application for fully austenitic stainless steels. all nickel base alloy electrodes have a basic coating (-15/B). The weldability of basic electrodes is, generally speaking, somewhat poorer than that of rutile-acid electrodes. Direct current (DC-) must always be used when welding with basic electrodes. A short arc is to be used for welding. This gives the best stability and reduces the risk of nitrogen pick-up. The latter can lead to pore formation and increase surface oxidation. MIG welding (which, as it is often carried out with an active component in the shielding gas, is really MAG welding) is a particularly good method for welding sheet metal up to around 6 mm thick. A pulsed current is best for welding, but a spray arc can be used in some cases. Drop transfer is considerably more sedate and more controlled with a pulsed arc. The opportunity for position welding, especially vertical-down, is thus very great. The advantage of spray-arc welding is the higher deposition rate. However, arc stability is lower and, because the weld pool is relatively large, position welding possibilities are limited. Arc stability varies greatly between not only different arc types and steel grades, but also between different welding machines.

8 Welding News TIG welding is normally used for thin materials (up to around 4 mm), especially when joining pipes in all welding positions. The method is also highly suitable for welding single-sided root beads (both with and without root backing). Subsequent beads can then be welded using a method with a higher deposition rate. Submerged arc welding of fully austenitic steels is associated with certain difficulties, but can certainly be carried out if the conditions are right. The problem with fully austenitic steels and SAW is the relatively high heat input, which increases the tendency to form secondary precipitates. If present in sufficiently large quantities, these can cause hot cracking or solidification cracking during welding. The risk increases with heat input and the material s thickness (the degree of restraint). To minimise the risk, welding should be with as little restraint as possible and the minimum conceivable heat input (max. 1.5 kj/mm). Regardless of this, productivity is high and the end result is a weld with a very fine finish. Furthermore, the work environment with SAW is considerably better because both fume generation and radiation are minimal. SAW must be with a basic agglomerate flux such as Avesta Flux 805 and a wire diameter of no more than 2.40 mm (max. 3.2 mm with 904L). Flux cored arc welding (FCAW) is suitable for material thicknesses above approximately 2.5 mm. Thanks to the slag that is formed, positional weldability is very good. For welding 254 SMO and 4529, there is Avesta FCW P12-PW flux cored wire. This is an all-round wire for all welding positions. It can also be used for overlay welding and welding 904L. Shielding gases MIG welding is best with a threecomponent gas Ar + 30% He + 1 2% O 2 or 2 3% CO 2. The oxygen and carbon dioxide here serve as arc stabilisers. An addition of 30 50% helium is advantageous. It increases arc energy which, in turn, increases weld pool fluidity and enables higher welding speeds. Pure argon can also be used. The gas flow is typically 15 l/min. An addition of 0.03% NO (nitrogen monoxide) is good not only from the environmental viewpoint (reduced ozone emissions), but also because it has a positive effect on arc stability. TIG welding is usually performed with pure argon as the shielding gas. A typical gas flow is 8 12 l/min. The addition of around 30% helium markedly increases arc energy and thus enables a 20 30% increase in welding speed. An addition of 1 3% hydrogen gives a similar effect and is used particularly for automated welding in tube/pipe manufacture. Single-sided root beads must be welded with a backing gas. This is normally the same as the shielding gas. However, Formier gas (90% N % H 2 ) is an alternative. This also provides good root protection. A backing gas should also be used as early as tack welding and all the way up until weld thickness is at least 8 mm. Backing gas flow is typically 8 12 l/min. FCAW is most suitably performed using argon with an addition of 16 25% carbon dioxide as the shielding gas. A typical gas flow is l/min. Shielding gases for MIG, TIG, FCW and plasma Method Steel grade Shielding gases Edge preparation When welding stainless steels, meticulous edge preparation and the correct choice of joint type are important for good results. This applies even more particularly to fully austenitic steels. Because of the weld pool s slightly poorer fusion penetration and fluidity (compared with standard austenites), the joint must be correctly designed to give full penetration without risking burn-through. The groove angle must be sufficiently wide to allow the welder full control of the arc, weld pool and slag. A groove angle of around 35 (i.e. somewhat larger than for austenitic standard steels) is to be recommended for manual welding. General recommendations: An X-joint can advantageously be used for plate thicknesses above approximately 15 mm. For plate thicknesses above approximately 30 mm, a double U-joint is advantageous. In single-sided welding, a root gap of 2 3 mm and a straight edge of about 0 1 mm are recommended. For double-sided welding, the straight edge can be increased to mm. MIG 904L, P12, P12-0 Nb, P54, P16 Ar + 30% He + 1 3% CO 2 Ar + 30% He + 1 2% O 2 TIG 904L, P12, P12-0 Nb, P54, P16 Ar, Ar + 1 5% H % He or Ar + 2N % He FCAW P12 Ar % CO 2 or 100% CO 2 Root protection 904L, P12, P12-0 Nb, P54, P16 90% N % H 2 or Ar

9 Welding News Examples of common joint types Joint type 1 I-joint, t < 2.5 mm D = mm Single-sided without root backing I-joint, t < 4.0 mm D = mm Double-sided with root grinding 1. I-joint for single-sided MMA, MIG, TIG and plasma arc welding. Suitable root protection must be used for single-sided TIG welding. Joint type 2 V-joint, t = 4 16 mm α = C = mm D = mm Single-sided without root backing V-joint, t = 4 16 mm α = C = mm D = mm Double-sided with root grinding 2. V-joint (t > 4 mm) for single and doublesided MMA and TIG welding as well as double-sided MIG and FCAW. Joint type 3 V-joint, t = 8 16 mm α = C = 3 6 mm No root gap 3. V-joint for SAW. So that full penetration is possible, the root bead must be ground precisely. Joint type 4 X-joint, t = mm α = C = 3 4 mm No root gap 4. In SAW, an X-joint is to be recommended where plate thickness exceeds 16 mm. Straight edge, 3 4 mm. Joint type 5 V-joint, t = 4 16 mm α = 50 C = mm D = mm Single-sided without root backing 5. Edge preparation for pipe joints. TIG or MMA welding is the most appropriate. Joint type 6 Half V-joint, t = mm α = 50 C = mm D = mm Double-sided 6. Half V-joint with full burn-through. Single-sided welding requires TIG or electrode for the root bead. In this type of joint, the distance between tacks should not exceed 150 mm. This is so that shrinkage does not prevent full burn-through. Joint type 7 U-joint, t > 30 mm α = 10 R = 8 mm C = mm D = mm Single-sided without root backing or double-sided with root grinding 7. Single-sided or double-sided U-joint for welding thick sections, t > 30 mm. The joint can advantageously be made as a symmetrical or asymmetrical double U-joint. Root welding is most suitably carried out as a TIG or MMA weld followed by SAW.

10 Welding News TIG welding produces beatiful welds and is mainly used for thin materials. Pre-weld cleaning To ensure good weldability and reduce the need for post-weld cleaning, all joint surfaces, and the surfaces adjoining these, must be thoroughly cleaned before welding. Dirt, oil and grease must be removed using, for example, a cleaning agent such as Avesta Cleaner. All rough edges, etc. must be carefully removed by gentle grinding. Oxides, paints and primers must be meticulously removed, not only in the joint, but also in the 50 mm from the joint edges. Considering that the fully austenitic steels are normally used in highly corrosive environments, the pre-weld cleaning is particularly important. Tacking So that shrinkage during welding does not prevent full burn-through, precise tack welding is extremely important. Many fully austenitic steels have a high strength, which makes tack welding even more important, than for conventional austenitic materials. For metal thicknesses up to 6 mm, tack length should be mm. This should be increased to mm for thicker workpieces. A suitable distance between tacks is mm. Destortion Fully austenitic steels have a greater coefficient of expansion than do low-alloy steels and duplex stainless steels. This means that distortion during welding is also greater. Consequently, to reduce distortion, tack welding has to be carried out precisely and the welding sequence meticulously planned. Pre-heating Generally speaking, stainless steels (fully austenitic steels included therein) must not be preheated before welding. Welding is normally carried out at room temperature. At lower temperatures, preheating to a maximum of 50 C is advisable. This drives off any moisture that may otherwise lead to pore formation. When welding castings, or where the workpiece is thick or where restraint is high, preheating to a maximum of 100 C may, in certain cases, be advantageous. In these cases, a suitable preheating method is the use of electric blankets or similar. The use of soot-depositing flames can result in local carburisation. This reduces resistance to intergranular corrosion. U x I k x V x 1,000 Interpass temperature Because fully austenitic materials are prone to inter-metallic precipitates, the interpass temperature must not be above 150 C for 904L and 100 C for other fully austenitic materials. Thermal conductivity is of the same order as for austenitic stainless steels, i.e. considerably lower than it is for low-alloy and carbon steels. This means that, compared to carbon steels, it takes longer to reach the correct interpass temperature. The cooling rate can be increased by using compressed air. This is most suitably directed at the back of the plate or the inside of the pipe. Compressed air directed straight into the welded joint presents the risk of contamination. Cooling can also be accelerated by intermittent welding or using a correctly planned welding sequence. The interpass temperature must be measured. Some form of thermometer or thermoelement is appropriate for this. Temperature crayons seldom give good results and must be avoided. Heat input To avoid intermetallic precipitates, the heat input when welding fully austenitic materials must be kept as low as possible without thereby giving rise to any risk of lack of fusion, etc. One general recommendation is a maximum of 1.5 kj/mm. However, the critical upper limit depends very much on welding method and the thickness of the workpiece. For example, MIG is not as sensitive as SAW and a 5 mm joint is less sensitive than a 20 mm joint. Especially in automated welding, heat input is easy to control. It is calculated by the following formula: U x I { } mm/s x 1000 = kj/mm U = voltage I = current V = speed The third and final part of this series of articles will be published in the next issue of Welding News.

11 Welding News voestalpine, Böhler Welding Group, Avesta Welding how do they fit together? Avesta Welding, the 100% stainless steel brand, became a part of Böhler Welding Group as long ago as November However, many people are still not aware of the group and Avesta s place in the overall picture. The corporation Comprising specialised companies that produce, refine and further develop high quality steel products, voestalpine is a global corporation. It is represented on all continents and has some 360 production and sales companies in over 60 countries. With a workforce of approximately 46,000, the turnover is around MEUR 12,000. The corporation s four divisions are all leaders in their individual fields of operation. voestalpine s divisions The group A voestalpine company, Böhler Welding Group is a leading global manufacturer and supplier of filler metals for welding and soldering applications. Böhler Welding Group focuses on industries with the severest technical requirements and on special applications such as oil and gas, offshore, petrochemicals, thermal power stations and pipelines. The group s workforce of around 2,000 generates an annual turnover of approximately MEUR 550. Steel High quality sheet and plate for the most demanding applications Special Steel Tool steel, high-speed steel and special forgings Metal Engineering Processed wire, turnouts, railway systems, seamless tubes, welding consumables Metal Forming Metal processing solutions, precision steel coil and special components for the automotive industry. Metal Engineering s business areas Steel Rail Technology Wire Seamless Tube Turnout Technology Welding Technology (Böhler Welding Group) Böhler Welding Group s brands Via its six specialised brands, Böhler Welding Group offers a wide product portfolio for joining, repairing, maintaining, overlay welding, soldering and brazing. Avesta Welding Avesta Welding is responsible for the 100% stainless steel element in Böhler Welding Group s array of brands. With 80 years in the industry, Avesta has gained special expertise in the welding and pickling of stainless steels. This is no less true for relatively new steels such as duplex and super duplex.