New welding process for armor steels: DLHP® welding technology provides impetus for a wide range of security applications

Background: The Hagen-based company Stahlkontor, a specialist in the processing of high-strength steels, has developed a new, fully mechanized welding process for armor steels and applied for a patent. The “Double LaserHybrid Process (DLHP®)” promises increased safety and quality, accelerated production and even economic advantages.
An interview with Managing Director Heiko Drawe and welding engineer Dipl.-Ing. Roman Litschmann, Stahlkontor GmbH & Co. KG, about the technical and economic background of DLHP® welding.

? How did Stahlkontor come to develop the DLHP® welding process?
Heiko Drawe: New materials and optimized processing methods have significantly driven specialization in the defense, aviation and civil protection sectors in recent years. Specialized contract manufacturers such as Stahlkontor are required to master the processes, which are strictly defined by standards and manufacturer requirements, in a comprehensible manner – this know-how is decisive for orders. Some years ago, we decided to actively follow this development, and even more: we wanted to set new technical impulses in some of our core competences, as a sustainable cooperation offer to our customers, so to speak.
Roman Litschmann: From our experience in contract manufacturing for a wide variety of safety-relevant components, we naturally know our customers’ pain points. We are actively involved in material testing, explosive and ballistic testing, and we know that the weld seam can be a critical area of components and assemblies made of armor steel. So begannen wir bereits vor einigen Jahren damit, unsere werkstoff- und schweißtechnischen Prozesskenntnisse zu bündeln. Ziel war es, einen vollmechanisierten Schweißprozess zu entwickeln, der unseren Kunden und uns einen deutlichen Nutzen bringt. Taking into account the strictest safety requirements.

? What makes the weld seam on armor plate a “critical” area?
Roman Litschmann: For us, the reference process for welding armor plate is the manual, multilayer MAG welding process. In MAG welding, one reduces the negative influences of local heat input into the material by dividing longer seams into sections and welding the individual parts “alternately,” i.e., in several approaches of about 300 mm each. When professionally implemented, this process leads to satisfactory results in terms of safety, but it is time-consuming and, due to the frequent weld approaches, harbors the increased risk of bonding defects, which can have a negative influence on the protective effect. In addition, the component quality suffers in terms of dimensional stability due to the frequent heating. The “wavy” shape results from welding stresses and angular shrinkage, mainly in thin-walled component structures. Thus, an additional straightening process usually has to be carried out to produce the desired flatness of the component. The higher welding speeds in the DLHP® welding process compared to conventional welding processes result in narrower heat-affected zones in the structures, which lead to an improvement in the mechanical-technological as well as the ballistic properties.
Heiko Drawe: In developing the DLHP® welding process, we addressed several points that are important to our customers. For example, the optimization of safety, quality, production time and costs were on our list of requirements for the new process. The actual news is: With the DLHP® welding process, we can offer our customers an alternative process that leads to a demonstrably safer product at the same or even slightly lower cost – and in significantly shorter production time and with improved visual appearance of the component. We have provided the relevant evidence both internally and externally, including successfully passed comparative gating and bombardment tests in accordance with WTD standards.

? For which components and assemblies is the new DLHP® welding process suitable?
Heiko Drawe: DLHP® welding makes sense wherever long weld seams are intended for joining armor steels and high-strength fine-grained structural steels and, in addition to the safety requirements, a uniform appearance of the weld seam is also desired. These can be floor assemblies and roofs of armored vehicles, but also system components of doors, gates or facades of higher protection classes as well as other special components for civil and defense protection. Further areas of use are found in applications for high-strength fine-grained steels, for example in the construction of special vehicles used in crane construction and firefighting equipment. Important in this regulated environment: Complete documentation and traceability of all process parameters is fully ensured, as DLHP® welding is a fully mechanized, CNC-controlled process, with online quality monitoring.

? DLHP® welding is faster and reduces time spent on rework. How will this be noticeable to your customers in order processing?
Heiko Drawe: To take an example from defense technology: Manufacturers of armored wheeled and tracked vehicles have seen a steady increase in demand in recent years – forecasts see orders doubling in the medium term. With DLHP® welding technology, we can cope much better with the expected increase in capacity in component and assembly production – without any compromises to the specific safety requirements of our customers.

? When will the new process be introduced at Stahlkontor?
Heiko Drawe: The DLHP® welding process is currently in the final phase of patent registration and testing. An introduction of the new technology into series production will take place in the fourth quarter of 2017. The new process is already firmly integrated into our medium-term production planning.

Stahlkontor – specialist for processing high-strength steels
Stahlkontor is a leading international, independent system supplier of parts and assemblies made of high-strength steels and armor steels for the defense, aviation, industrial and rail vehicle sectors as well as other civil security applications. The Hagen-based company with around 250 employees has many years of materials and process experience, state-of-the-art machinery and uses powerful programming and design software for economical, fast and volume-adapted order processing. The wide range of cutting, blasting, machining and joining technologies available in-house includes the fully mechanized Double LaserHybrid Process (DLHP®) developed by Stahlkontor itself and patented in 2017 – currently the most economical and safety-engineering process for welding armor steels. For more information, visit www.stahlkontor.de