TASK 70-31-02-310-501-005 Argonarc Welding Repairs - The Procedure To Weld Aluminum Alloys

DMC:V2500-00-70-31-02-04A-627A-D|Issue No:001.00|Issue Date:2013-03-20

Export Control

EAR Export Classification: Not subject to the EAR per 15 C.F.R. Chapter 1, Part 734.3(b)(3), except for the following Service Bulletins which are currently published as EAR Export Classification 9E991: SBE70-0992, SBE72-0483, SBE72-0580, SBE72-0588, SBE72-0640, SBE73-0209, SBE80-0024 and SBE80-0025.

Copyright

© IAE International Aero Engines AG (2001, 2014 - 2021) The information contained in this document is the property of © IAE International Aero Engines AG and may not be copied or used for any purpose other than that for which it is supplied without the express written authority of © IAE International Aero Engines AG. (This does not preclude use by engine and aircraft operators for normal instructional, maintenance or overhaul purposes.).

Applicability

All

Common Information

TASK 70-31-02-310-501-005 Argonarc Welding Repairs - The Procedure To Weld Aluminum Alloys

General

Aluminum alloys are used where low weight is important and the temperature at which the part operates is low. The type of aluminum used ranges from low strength sheet for non structural parts, to age hardened alloys where strength and creep resistant properties are necessary. Repair by welding is usually done to repair alloy castings.

The weldability of the aluminum alloy depends on the type. Some alloys, (for example: Group ID in SPM TASK 70-31-02-310-501-002, SUBTASK 70-31-02-310-046) are difficult to weld and must only be welded when specified in the Engine Manual.

When aluminum and its alloys are welded, the weld areas and the surface of the filler wire must be very clean. If it is not very clean, porosity, slag inclusions, cracks and an unsatisfactory weld pool will result.

A welding plant with AC power output is used to weld aluminum and its alloys. This breaks and removes the surface oxide on the molten weld pool. AC welding results in a lower proportion of the heat transmitted to the part than with DC welding. Because of the high thermal conductivity of aluminium alloys heat is quickly conducted away from the weld. Thus, very much higher welding currents are necessary for aluminum than for ferrous and nickel base alloys.

It is important to prevent very high heat inputs to keep distortion and cracks to a minimum. Metal removed for weld preparation must be the least necessary to completely remove the defect. The design of the fixture used to hold the part is important as it can be used as a heat soak.

Unwanted weld metal must be kept to a minimum and removed while it is hot.

Refer to the SPM TASK 70-31-02-310-501-001 for other related TASKS.

Preliminary Requirements

Pre-Conditions

NONE

Support Equipment

NONE

Consumables, Materials and Expendables

NONE

Spares

NONE

Safety Requirements

WARNING

IT IS THE RESPONSIBILITY OF THE OPERATOR TO OBTAIN AND OBSERVE THE MANUFACTURER'S MATERIAL SAFETY DATA SHEETS FOR CONSUMABLE MATERIALS. THESE CONTAIN INFORMATION SUCH AS, HAZARDOUS INGREDIENTS, PHYSICAL/CHEMICAL CHARACTERISTICS, FIRE, EXPLOSION, REACTIVITY, HEALTH HAZARD DATA, PRECAUTIONS FOR SAFE HANDLING, USE AND CONTROL MEASURES AND ALSO TO TAKE LOCAL REGULATIONS INTO CONSIDERATION.

Procedure

    1. SUBTASK 70-31-02-310-010 Preparation of the Surface

    1. CAUTION

      DO NOT USE GRINDING WHEELS BECAUSE OF CONTAMINATION OF THE MATERIAL WITH GRINDING WHEEL PARTICLES.

      Use a small, thin tungsten carbide cutter and remove the least material necessary to remove the defect. Chemical etching can be used to make sure of the complete removal of the defect. It is important to remove cracks completely or they could become larger during welding. Do not cut completely through the wall section unless it is necessary to remove the defect.

    2. Completely clean the area to be welded and make sure there is no grease, surface corrosion or unwanted material. Paint and anodized surfaces must be removed. This can be done with chemicals or mechanically, such as a nickel wire brush or a file.

    3. After the weld areas are mechanically cleaned they must be cleaned with a liquid degreaser. Filler wires and rods must also be degreased with this procedure before you weld.

    4. The surfaces will have to be cleaned again if the weld is not completed in 24 hours.

    2. SUBTASK 70-31-02-310-011 The Procedure to Weld Aluminum and its Alloys

    1. Welding must be done with approved AC equipment as specified in SPM TASK 70-31-02-310-501-001.

    2. CAUTION

      THE HEAT MUST NOT BE APPLIED LOCALLY.

      Castings are usually pre-heated to keep distortion and shrinkage cracks to a minimum. The temperature depends on the precipitation temperature of the alloy. Pre-heating data is given in the applicable Repair but the temperature is usually in the range of 266 to 410 deg F (130 to 210 deg C).

    3. The complete casting must be heated to a controlled temperature in an oven or a vapor degreasing tank. After it is pre-heated, the casting must have insulation put on to keep the temperature as long as possible during welding. Do not let the temperature become as low as 212 deg F (100 deg C). Heat the part again if necessary.

    4. If the weld is to fully penetrate the section, argon backing can be used.

    5. Electrode tips must be radiused for a stable arc. An alternative to this is to let the tip become rounded (with the arc at the developed current) on a large piece of light alloy. This procedure keeps tungsten inclusions to a minimum.

    6. The surfaces to be welded must first be fused without filler. This gives a smooth clean surface for the weld and keeps porosity to a minimum. Prevent the use of too much filler.

    7. Between runs the weld must be completely cleaned with a wire brush to remove the oxide layer. When the last run is complete make sure the weld is fused so it is smooth and has no surface porisity.

    8. Immediately the weld is completed, the weld area must have insulation put on it until it becomes cool. Alternatively put the part in an oven to control the rate at which it becomes cool or for post weld heat treatment.

    3. SUBTASK 70-31-02-370-003 The Heat Treatment of Aluminum and its Alloy

    1. The post weld heat treatment will depend on the alloy and will be specified in the applicable Repair. General data is given in SPM TASK 70-31-02-310-501-001 and SPM TASK 70-31-02-310-501-004.

Requirements After Job Completion

Follow-On Conditions

NONE