Flawless rotor housings for the Nuclear Industry

Pleissner Guss GmbH is one of the leading cast steel manufacturers in Europe. At Pleissner, top-class cast products are manufactured, which are mainly used in valves, pumps, energy machines and other mechanical engineering products.

As part of a new project, welding optimization work had to be carried out on a rotor housing for a process gas blower in a nuclear power plant. In particular, this concerned the inlet and outlet of the bearing housings and their cover designs. The end product is used in the nuclear sector. Against this background, RCC-M standards had to be adhered to during manufacture. Therefore, it was also important to ensure complete documentation of the welding process during the careful welds.

In order to produce a flawless, completely tight component, a complete welding solution from voestalpine Böhler Welding was selected:

• Fillermetal: FOXcore 13/4-MC metal flux-coredwire (1.2mm)
• Weldingmachine: URANOS 4000 GSM multiprocess system with Böhler Arc-Kennline for FOXcore 13/4-MC
• On-site service: Our field service team worked closely with the customer and a regional partner performance dealer to analyze the customer's requirements and develop a customized solution.
• Documentation software: weld@net^®  PCM (Production Control Monitor)
• PPE: Use of a BÖHLER Air is a blower respiratory protection system (PAPR system) that provides the welder with the best possible protection against particles and gases.

The process gas blowers to be welded are cast from the material X 5 CrNiMo 13 4 (stainless, soft-martensitic chromium-nickel steel with molybdenum additive; temperature range from -60 °C to +300 °C). To ensure that the material retains its properties of good toughness with limited hardness (in this case max. 23 HRC) after the welding work, the component was preheated and compliance with the necessary interpass temperatures was guaranteed. Following the welds, additional stress-relief annealing was performed. The challenge was to avoid hardness peaks so that the properties of the weld metal could match those of the base metal as closely as possible.

The FOXcore 13/4-MC metal flux-cored wire was used in the welding operations to ensure the avoidance of bonding defects with maximum freedom from pores. The easy handling and high deposition rate of FOXcore 13/4-MC resulted in high productivity with excellent welding behavior and very low spatter formation. The wire showed good wetting behavior in the application and produced a smooth surface. The wide arc ensured uniform flank penetration and prevented bonding defects. The precise matching of the alloy of the filler metal to the material resulted in very good notched impact strength and strength of the weld metal even after heat treatment. The extremely low content of diffusible hydrogen, at a maximum of 3 ml/100 g, also ensured cold cracking resistance.

In order to be able to use the advantages of the Böhler FOXcore 13/4-MC, an optimized parameterization is to be aimed at. For this purpose, the responsible welding engineer at Pleissner decided to purchase several multiprocess units, the URANOS 4000 GSM from Böhler Welding. The welding machine was equipped ex works with a special characteristic curve for the FOXcore 13/4-MC. This ensured an optimum arc right at the start.

The weld@net system from Böhler Welding was used for documentation purposes. Several URANOS 4000 GSM welders were connected to this system. This made it possible to document the comprehensive recording and monitoring of all welding parameters with reports and diagrams. In addition, implementation of any necessary corrective measures could be guaranteed in real time in this way.

Thanks to the interaction of the aforementioned solution modules, it was possible to solve the welding task with its high demands on heat guidance, testing effort and manual dexterity against the background of this complex component, including the necessary documentation. voestalpine Böhler Welding and the partner performance dealer PEDO Schweißtechnik were always the direct contacts at all process steps: no matter whether factory certificates were needed, welding parameters had to be adjusted, material issues had to be clarified or data documentation had to be ensured.

Particularly in this project, which was so demanding in terms of materials technology, the concept of supplying all solution modules from a single source proved to be a major advantage.

Partner Performance distributor of Böhler Welding - PEDO Schweiß, Löt- und Verschleißschutztechnik from Katlenburg-Lindau: Owner Peter Dommes has significantly initiated, developed and accompanied the project through his commitment. Our partner took over the planning, commissioning, wire supply, and handing over of the works certificates according to RCC-M 2007 standard and took over the daily service on site.