01.09.2012 Stahlmarkt 09-2012

Two major projects were realized at the welding plants Essen and Swietochlowice (Poland). The “Stahlmarkt” reports.

Established as a trading company, the Essen based von Schaewen Group has consistently expanded its competences in the field of steel for over 80 years. Today the family-owned company offers a comprehensive range of products relating to all aspects of the material steel.

The company’s history is distinguished by the constant desire to adapt to the market’s and the customers’ changing requirements and to customize our product portfolio to those needs. This helped us to develop from a mere steel trading company into a service provider whose production and processing facilities complement one another in an ideal manner. Van Schaewen Group, the long-standing and traditional steel-maker, is thus at the same time a supplier of sheet metal and bar steel, a specialist for flame cutting, an established partner for mechanical steel processing and, since 2008, a producer of welding constructions. This led to the establishment of innovative specialist welding companies, first at our headquarters in Essen and later in Swietochlowice, Poland, both of which live up to the highest industry standards.

“At the beginning we carried out welding of large workpieces mainly on a contract basis,“ explains Jörg Köhl, welding engineer and welding supervisor at the Essen-Vogelheim und Swietochlowice locations. “But with increasing experience our ambitions grew, so that we dared approaching more and more complex production tasks. Nowadays we receive orders from all parts of the world for large-size welded structures of a weight of up to 80 tons.” This involves the use of the general-purpose structural steels S235 and S355 as well as the use of state-the-art fine grain structural steels such as S690QL or S960QL, or mixtures of both. Our range of services also includes the production of welding constructions made of material combinations such as S355 with 34CrNiMo6 or 42CrMo4. For such purposes von Schaewen also works with wear- and corrosion-resistant welding consumables. Various welding techniques such as solid wire and filled-wire welding (MAG M), single or double wire submerged arc welding (UP) and manual arc welding (E) are employed. Competence in this specialist area is evidenced by the so-called Major Welding Certificate, i.e. the manufacturer’s qualification for the welding of steel structures according to DIN 18800-7:2002, class E. It goes without saying that our specialist welding companies, like all the other companies of the group, are certificated according to  DIN EN ISO 9001 and meet the necessary “comprehensive quality requirements” in welding in accordance with DIN EN ISO 3834-2.

“To us it has always been basically important not only to deliver a good product, but also to organize the whole production process efficiently,” explains Herr Köhl. “That’s why the increase of welding efficiency is the focus of the development of our production technology. It achieves special significance in the field of mechanized welding of large cross-sections on thick-wall components, which include long welding time and high seam volumes, both being among the largest cost factors.”

“Last year we had the opportunity to push our production possibilities even further to the limit. We received an order from a manufacturer of aluminium and steel rolling mills for rolling supports that were to be welded together,” reports Herr Köhl. The larger of the two models, with a total dimension of  about  530 x 3,000 x 6,250mm, had a weight of about 35t. As the necessary components were forged parts as well as flame-cut shapes, von Schaewen Ltd. was predestined for this job. At first the required rough parts were produced in the forge. Subsequently, the desired shapes were flame-cut into the rough material with its thickness of up to 570mm, and the weld seam preparation was carried out. Mechanical pre-processing and final processing were carried out completely within the company as well. 

 “Due to the large number of operating steps, that order was very time-consuming and labour intensive. Conjointly with our customer and our supplier we worked out a solution how to reduce processing costs by welding a single U, a so-called tulip shape, using the narrow gap welding method. Our customer granted us a considerable credit of trust, so we adapted our powder welding system by upgrading it with a welding plate and started welding,”  explains Herr Köhl. “In the end we had succeeded at welding two blocks with a thickness of 530mm, with a gap of only 45mm at the exit.”

A narrow gap seam is generally characterized by a very narrow weld groove with fusion faces that tend to be mechanically pre-machined The reduction of the weld volume or layers results in a reduction of the welding time, lower tool wear and consequently creates cost savings. In addition, submerged arc welds are characterized by higher quality when compared to MAG welds.

“Having the mechanical processing unit directly on the premises was, of course, a huge advantage. It helped us to reach agreements in a fast and uncomplicated way when the shape of the parts to be welded had to be determined, to make sure that the product really meets the common requirements at the end,” praises Herr Köhl. As the method was applied for the first time, a control test piece with a thickness of 440mm was produced first. It was subsequently sawn into five slices, and the micrograph  of the middle section was processed by an external laboratory. “We were immensely excited to see the  macrosection of our control test piece, and felt very proud to see a homogenous and pore-free narrow gap weld. Then we used the same parameters to weld the actual workpiece – to the utmost satisfaction of our customer.”

At the production site in Swietochlowice we accomplished a project which was similar in scale. For a company in the metal working business we produced two end pieces with an individual weight of 72t and 80t respectively. The extensive capacities at the production site made it possible not only to carry out the MAG welding itself, but also the subsequent blasting and priming. Additionally to the furnace capacity of 4,000 x 4,000 x 8,000mm and a volume capacity of 70t, the site boasts a 5,100 x 6,700 x 12,000mm sized blasting cabinet with a capacity of 80t. This is where everything comes full circle again, as the starting material and bevels for the weld preparation can be provided within the group.

It is thanks to the coordination of the group’s production branches that the customer receives an optimal product at the end of the production process. The following welding works can, for example, be taken into consideration when the starting material for forging or for the production of flame-cut parts is chosen. The mechanical processing supplies shapes that match on a one-to-one basis, and the in-house quality control examines and evaluates the weld seams with ultrasonic testing, surface crack examinations and magnetic particle inspections. In this system, one hand always knows what the other is doing.