Welding technology permanently and integrally joins metallic materials. In construction, deconstruction and extraction it plays a central role: from manufacturing and adapting auxiliary structures, through repairing equipment, to safely severing or securing components during an ongoing project. In conjunction with the application areas concrete demolition and special deconstruction, strip-out and cutting, rock excavation and tunnel construction, natural stone extraction as well as special operations, welding technology enables reliable solutions coordinated with hydraulic tools such as concrete pulverizers or stone and concrete splitters.
Definition: What is meant by welding technology
Welding technology encompasses all procedures by which metals are permanently joined through the input of heat, force, or both. A distinction is made between fusion welding (for example arc processes such as SMAW stick, MAG/MIG or TIG) and pressure welding (for example resistance spot welding). Depending on the process, welding consumables, shielding gases and defined heat-affected zones are used. The goal is an material-bonded joint with sufficient load-bearing capacity, toughness and durability—considering the material, component geometry and loading.
Basics of welding processes in deconstruction and construction
In the context of demolition, deconstruction and assembly, electrically powered arc processes are primarily used. They are robust, mobile and controllable—even under changing on-site conditions on the construction site.
E-Hand (manual metal arc welding)
Universal process with coated stick electrodes. Suitable for sites with limited infrastructure, tolerant of slightly contaminated surfaces, but with higher slag and spatter formation. Popular for assembly and repair work on auxiliary structures, adapter plates and reinforcements.
MAG/MIG (gas metal arc welding)
Productive process with continuous wire. MAG for unalloyed and low-alloy steels, MIG for aluminum and higher-alloy materials. Delivers high deposition rates and clean seams, but requires wind protection and appropriate shielding gas coverage.
TIG (tungsten inert gas welding)
High-quality, controlled seams with low notch effect, ideal for thin-walled components, stainless steel and precision joints. In deconstruction it is especially useful where dimensional accuracy is critical and rework must be minimized.
Thermal cutting and gouging
Oxy-fuel cutting, plasma cutting and carbon-arc gouging are used to sever or open steel sections. These hot works require careful planning, particularly in sensitive environments such as tanks, shafts or areas with flammable substances.
Materials, heat-affected zone and joint design
On-site welding work predominantly involves unalloyed and low-alloy steels for auxiliary structures, support frames, brackets and stiffeners. Decisive factors are joint preparation, heat input and cooling conditions to avoid cracking, hard zones or distortion.
Working in line with the material
- Low-alloy structural steels: Often weldable on site; consider preheating for thicker sections.
- High-strength fine-grained steels: Limit heat input, use appropriate filler materials and observe interpass temperatures.
- Quenched and tempered components: Consider risk of hardening cracks; if permitted at all, work only with qualified procedures and explicit approval.
Heat-affected zone (HAZ)
The HAZ is mechanically and metallurgically altered. Adjusted heat input (current, voltage, travel speed), controlled interpass temperatures and, if necessary, preheating limit unfavorable hard or brittle structures.
Joint preparation and form
Defined bevels, root gaps and tack points ensure penetration, prevent lack of fusion and reduce rework. The choice between fillet welds, butt welds or combined geometries depends on load path and accessibility.
Welding technology in combination with concrete pulverizers and stone and concrete splitters
Mechanical cutting and splitting processes govern the deconstruction of concrete and natural stone. Welding technology complements these methods by enabling auxiliary means and temporary interfaces.
- Concrete pulverizers: During deconstruction stages, embedded items, reinforcement and clamping points occur. Welded attachment brackets, protective guards or temporary guides can improve material flow and safety. The actual pulverizer components should be serviced exclusively in accordance with the manufacturer’s specifications; welding that alters the structure of safety parts must be avoided unless there is an explicit release.
- Stone and concrete splitters: Welded constructions are often used for drill mounts, storage racks or support frames. They facilitate positioned placement of splitting cylinders and distribute forces evenly into substructures.
In both cases, welding work primarily concerns peripheral and auxiliary structures, not function-critical components of the tools. Mechanical cutting (for example with hydraulic steel shears or Multi Cutters) reduces fire load and is often preferable to thermal cutting for steel components.
Planning, workflow and power supply
Clean planning saves time, reduces risks and improves seam quality. A structured workflow is crucial, especially under construction site conditions.
- Assessment: Identify the material, component thickness, accessibility, load path and environmental conditions (wind, moisture).
- Select the process: SMAW stick for robust assembly, MAG/MIG for productive serial seams, TIG for precision.
- Joint preparation: Dress edges, remove oxides and coatings, place tack welds.
- Control heat input: Record parameters, monitor interpass temperature, counteract distortion (backstep sequence, fixtures).
- Rework: Remove slag, visual inspection, non-destructive testing if required.
Safety and fire protection for hot works
Welding, oxy-fuel cutting and gouging are considered hot works and require fire and explosion protection measures. Requirements can vary by object and should always be assessed project-specifically.
- Remove fire loads, shield against sparks, keep extinguishing agents ready.
- Gases and vessels: Work on tanks, pipelines and cavities only after gas testing and suitable cleaning or inerting measures. Special tools such as tank cutters are used only in designated, approved applications.
- Provide ventilation and fume extraction for welding fumes; use personal protective equipment.
- Observe release processes (for example hot work permit); ensure supervision and post-work monitoring.
Alternative cutting and joining methods in deconstruction
Depending on the objective, welding can be replaced by mechanical or bolt-based methods to avoid heat and sparks.
- Mechanical cutting: steel shears and Multi Cutters minimize thermal effects and are often the first choice in steel–concrete composites.
- Mechanical joining: Screw connections, clamps and press-fit constructions facilitate disassembly and reuse.
- Splitting instead of flame cutting: rock wedge splitter and stone and concrete splitters separate brittle materials in a controlled manner without thermal influence zones.
Quality assurance, testing and documentation
The quality of a welded joint is ensured by qualified personnel, clear instructions and testing.
- Welding instructions: Define parameters, filler materials and sequences; keep and document them for recurring work.
- Testing: Visual inspection, dimensional control, and, where applicable, non-destructive testing (for example magnetic particle testing) for safety-relevant seams.
- Traceability: Mark components, batches and changes in a traceable manner; implement changes only after approval.
Environmental and occupational health protection
Good visibility of the work area, low exposure and an orderly workplace improve results and protect the team.
- Capture and extract welding fumes; operate and maintain filters.
- Assess noise and vibration sources; plan working hours and breaks accordingly.
- Separate material residues by type; dispose of consumables in an environmentally sound manner.
Practice relevance to application areas
Concrete demolition and special deconstruction
Temporary steel structures such as shoring, protective covers or support frames are often welded. Where reinforcement is exposed, mechanical cutting is safe and efficient; welding on reinforcement should only be carried out with approval and appropriate qualification.
Strip-out and cutting
In buildings with high fire load, mechanical cutting takes priority. Where welding is required (for example brackets for temporary utilities), protective measures and clearly defined work areas are crucial.
Rock excavation and tunnel construction
Assembly frames, drill rig carriers and cable tray supports are frequently welded. Due to confined conditions, pay particular attention to sparks, fume extraction and escape routes.
Natural stone extraction
Frames and stops for splitting operations are often built as welded steel structures. Even load distribution and sufficient stiffness increase process reliability.
Special operations
For unusual tasks—such as the controlled opening of tanks—tailored, welded auxiliary structures are possible. Hot works are performed only after careful risk assessment and with suitable tools such as tank cutters.
Maintenance and repair work
Wear parts are generally replaced. Weld repairs on load-bearing or safety-relevant components are performed only after assessment and approval. Non-critical add-on parts, guards or brackets, on the other hand, can often be economically rewelded or adapted.
Best practices for robust results
- Preparation over improvisation: Clean edges, defined bevels, appropriate root gaps.
- Manage distortion: Backstep welding, fix components, control heat input.
- Document: Record parameters, filler materials, preheat and interpass temperatures.
- Combine: Purposefully integrate mechanical methods (for example with concrete pulverizers, steel shears) and welding technology.
This creates a reliable interplay of welding technology and hydraulic tools from Darda GmbH—practical, safe and appropriate to the materials.