Klass.-Nr./Class.No. 04 84 6 Welded Seam Repairs on Aluminum Structures
Product Evaluation and Notes on Procedure Konzernnorm Descriptors: welding, welded seam repair, aluminum, aluminiu
The English translation is believed to be accurate. In case of discrepancies the German version shall govern.
VW 011 42
Changes The following changes have been made as compared to the VW 011 42: 1996-10 issue:
Quality of photographs improved Section 1: Reference PV 6465 changed into VW 011 06-3
Previous issues VW 01142: 1996-10 1 Scope
This standard specifies procedures for the repair of welded seams that exhibit unacceptable external characteristics when evaluated according to VW 011 06-3. Only those characteristics explicitly described in section 4 may be repaired. The specified procedures shall be used to cut away and repair weld the depicted irregularities. The external characteristics of the reworked areas shall again be checked for their adherence to VW 011 06-3. The requirements and preparations necessary for reworking the irregularities are given. 2 Requirements
As is the case with production, also rework and repair are subject to defined requirements: These include sufficient qualification of the welder and certain requirements for component quality. Component quality consists of different ingredients; the reworked component must meet the requirements in each point. The process engineering technology to be used is restricted to that used in production. 2.1 Welder
Only qualified aluminum welders (qualification according to DIN EN 287-2) may carry out the repair work. To provide additional qualification, the employees shall be trained in performing preparatory measures for the repair works (e.g. cleaning the weld area, removing flaws, etc.). 2.2 Component
As the general requirements for a component are not only related to the quality of the welded seam but also to its specified shape, and as this shape may vary as a function of the applied welding heat and the thereby induced distortion, correspondence with the component shape shall be ensured for extensive repair works and/or intense heat application.
Form FE 41 -10.99
Page 1 of 7
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The component to be repaired must be released for repair, i.e. at the time of rework the process must be thoroughly documented. Components already signed out as scrap and components indicated in red must not be repaired, even if this were possible from the technical point of view.
Norm vor Anwendung auf Aktualit?t prüfen / Check standard for current issue prior to usage.
Page 2 VW 011 42: 2002-05 2.3 Process engineering
The processes used are manual MIG and TIG welding. Boundary conditions such as system settings, filler metals etc. must correspond to those in production; they are to be taken from the related work instructions. The welder decides on the basis of his/her experience which welding method is used. For special applications the method to be used preferably is specified in the list of irregularities requiring rework. 3 Preparation
The areas to be prepared for rework are differentiated corresponding to the following groups of flaws: ─ Flaws which can be reworked without welding and be evaluated OK after mechanical grinding or milling ─ Flaws which require rewelding and preliminary mechanical rework, if necessary The required preparatory processing steps are given in Figure 1: to Figure 9: within the specification of rework measures for specific irregularities. The basic work instructions shall always be adhered to. Tools: The tools to be used must always be appropriated, clean and free of grease and oil:
─ ─ ─
Stainless steel brushes Grinding wheels Hand milling cutters, e.g. operated by compressed air; the air must be free of oil or the tool ventilation must be situated on the tool-side turned away from the workpiece Procedure
Possible irregularities of the exterior welded seam characteristics and their removement are described in Figure 1: to Figure 9:. Open end craters On the left-hand image in Figure 1: an open end crater is represented. This irregularity can be removed by using filler material, see right-hand image in Figure 1:. Mechanical preparatory works are not mandatory. TIG or MIG welding are suitable welding procedures.
Figure 1: Open end craters Left: Before rework
Right: After rework
Page 3 VW 011 42: 2002-05 4.1 Melted-on weld spatter
In the case of impermissible melted-on weld spatter (e.g. on functional surfaces), see left-hand image in Figure 2:, mechanical removement is permissible. The base material surface shall be protected as far as possible. For an example of carefully removed weld spatter see right-hand image in Figure 2:. Some excess weld metal has also been removed.
Figure 2: Area with melted-on weld spatter Left: Before rework Right: After rework 4.2 Misaligned welded joint, incompletely fused edges, weld irregularities
Misaligned welded joint (see left-hand image in Figure 3:) occurs mainly when welding is performed automatically by robots. Often rework is not possible as in addition there is a penetration bead in the case of root penetration. Whether this is necessary must be checked on a case-bycase basis. Incompletely fused workpiece edges (see right-hand upper image in Figure 3:), occurring also in cases of insufficient seam thickness, shall be reworked by welding them over again (see right-hand lower image in Figure 3:). Here, the penetration bead in the case of root penetration shall be taken into consideration.
Figure 3: Left: Misaligned welded joint Right, upper: Incompletely fused edges Right, lower: Reworked by welding-over again
Page 4 VW 011 42: 2002-05 Mechanical preparation of an area can be used to achieve a clean seam transition following the repair of localized irregularities if simple welding over is not sufficient. The rewelding to be carried out will be done manually. Either TIG or MIG welding can be used. MIG welding shall, however, be the preferred technique due to the higher temperatures involved in TIG welding. For an example see Figure 4:
Figure 4: Left: Irregularities in the seam Center: Mechanical preparation Right: Rewelded area 4.3 Cracks on the end crater
Figure 5: depicts cracks on the end crater in a schematic representation. It is often difficult to detect them with the unaided eye. One way of detecting them is using the liquid penetrant test, for example. The cracked area shall be removed up to the bottom of the crack and be rewelded using the preliminarily used filler metal. Just as important as discovering and repairing the crack is analyzing why it occurred. The relevant weld supervisor shall therefore be informed immediately.
End crater with crack
Figure 5: End crater with crack
Page 5 VW 011 42: 2002-05
Localized open pores, impurities (slag)
In cases of localized porosity or slag, the affected area shall be completely prepared mechanically, and the seam shall be completed again using a MIG or TIG welding technique. MIG welding shall be preferred as the heat input of this procedure is lower. It is important to analyze the cause of the porosity. See Figure 6: for an example of porosity on a welded seam; see Figure 7: for an example of a slagged welded seam:
Left: Porous welded seam
Center: Mechanical preparation
Right: Rewelded seam
Left: Slagged seam
Center: Mechanical preparation
Right: Rewelded seam
Page 6 VW 011 42: 2002-05 4.5 Burned-through spots
If the wrong welding parameters are chosen (too hot), the fluid weld metal burns through the material creating a hole. The subsequent filling of the hole is possible only with a backing once a certain size is exceeded. This requires access to the underside of the workpiece. As this access is not available in the majority of cases, reworking is restricted to burn-throughs with a width of 0.8 x seam width. This reworking can be carried out without a backing. The burn-through depicted in the left-hand image in Figure 8: is irreparable due to its size. Part is scrap. The burn-throughs depicted in the center image in Figure 8: (bottom 6 mm, top 8 mm) have been removed using a conical tool.
Figure 8: Left: Irreparable burn-through Center: Reparable burn-through (preparation required) Right: Repaired seam
Page 7 VW 011 42: 2002-05 4.6 Concavity and convexity of welded seams
Where a defect is caused by excess weld material (convex), the top edge of the seam can be ground off (see also Figure 9:). However, sufficient penetration shall be ensured. This is probably not the case with a very curled seam bead; the defect must then be prepared mechanically prior to rewelding (see also Figure 6: and Figure 7:). In contrast, the upper bead of the drop-through at the root can be too large in the case of a concave seam geometry. Reworking is not permitted in this instance. The component is to be scrapped.
Figure 9: Curled seam and sagging seam 4.7 Cracks
Cracks in a seam are not authorized for repair. The repair of non strength-critical parts can be agreed with the relevant quality assurance department in exceptional cases. 5 Referenced standards1 Gas-Shielded Arc Welding, Part 3: Al Welded Joints Approval Testing of Welders – Fusion Welding – Part 2: Aluminium and Aluminium Alloys
VW 011 06-3 DIN EN 287-2
In this section terminological inconsistencies may occur as the original titles are used.