Preliminary Requirements

Procedure

1. SUBTASK 70-31-02-860-003 General

   1. 
      CAUTION
      WELDING MUST BE DONE IN A CLEAN AREA WHICH HAS PROTECTION FROM DRAFTS THAT CAN MOVE THE ARGON GAS.

      Introduction.

      1. This task provides general data for the weld repair of cracks and the replacement of material to metal parts with argonarc welding. In some cases changes to this general data or the use of special procedures is necessary. These changes will be given in detail in the Engine Manual. The Engine Manual is the primary authority. The weld group will be given in the applicable repair. Weld classification is given in Step.

      2. A laser welding can be used in place of the argon arc process for weld build-up repairs provided it can be demonstrated that the necessary quality standard can be achieved. The consumable materials must be approved by IAE.

2. SUBTASK 70-31-02-860-001 Safety Precautions

   
   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.
   
   WARNING
   ULTRAVIOLET LIGHT PRODUCED DURING ARC WELDING CAN BE HAZARDOUS. WEAR APPROPRIATE PERSONAL PROTECTIVE EQUIPMENT.
   
   WARNING
   FUMES PRODUCED DURING WELDING CAN BE HAZARDOUS. MAKE SURE VENTILATION IS ADEQUATE OR WEAR APPROPRIATE PERSONAL PROTECTION.

   1. The health and safety guidelines in this procedure are to provide a basis for safe working practice. It remains the responsibility of the operator to make sure the work is done safely.

3. SUBTASK 70-31-02-120-001 Clean the Part Before you Weld

   
   CAUTION
   ABRASIVE MEDIA, STAINLESS STEEL WIRE BRUSHES, ABRASIVE MOPS, AND ROTARY FILES, USED TO PREPARE WELDS MUST BE CLEAN AND FREE FROM GREASE. DIRTY TOOLS CAN TRANSFER CONTAMINATION TO THE WELD PREPARATION WHICH CAUSES WELD DEFECTS.

   1. Before welding, it is essential to remove all dirt, oxide, paints and coatings from the weld edges and the surrounding surfaces on both sides of the material.

      1. Clean the parts to be welded by one of the methods in the SPM TASK 70-11-01-300-503 (vapour degreasing), or SPM TASK 70-11-03-300-503 (aqueous cleaning), or SPM TASK 70-11-26-300-503 (local degreasing with solvent), or SPM TASK 70-11-34-300-503 (aqueous degreasing). Then, if necessary, clean the surface to be welded by a suitable abrasive method. Examples of suitable methods are: abrasive mop, or rotary file, or abrasive blasting with CoMat 05-003 ABRASIVE MEDIUM ALUMINUM OXIDE, 120/220 GRADE. After abrasive blasting, it may be necessary to scurf mop the edges with carbide paper. Titanium alloys may need to be etched if weld porosity is a problem.

         1. A stainless steel wire brush can be used to remove rough scale, but wire brushes can polish over contamination so the final preparation must be by an abrasive technique.

         2. Stainless steel wire brushes can be used to clean welds between passes on multipass welds.

      2. Make sure all loose particles have been removed and grease have be removed.

      3. Immediately before welding, degrease the part again.

   2. If a specific cleaning procedure is necessary, the procedure will be specified in the Engine Manual.

4. SUBTASK 70-31-02-310-001 Shielding Gas used in Welding Repair Methods

   1. The shielding gas is needed to protect the molten weld pool from atmospheric contamination. The top of the weld is shielded by the gas from the welding torch; for automatic welds a trailing shroud may also be required. The back of the weld also needs to be protected. This shielding can be provided by:

      1. A backing fixture with a recess for gas feed.

      2. A diffuser box.

      3. Purging the interior of the component.

      4. An argon box.

   2. It is recommended that regular argon purity checks are made. A dewpoint of -40 deg F (-40 deg C) or better is satisfactory.

   3. The usual shielding gas for repair welding is CoMat 03-010 ARGON GAS.

      1. For nickel alloys, the use of a mixture of 95 percent argon/5 percent hydrogen is permitted. This will give better depth of penetration and a clean underbead.

      2. For corrosion resistant steels, the use of a mixture of 95 percent argon/5 percent hydrogen is permitted provided the heat treatment at the tempering temperature is carried out within 3 days of welding. Refer to TASK 70-31-02-310-510-008.

      3. Argon/helium mixtures may be permitted with the written authority of IAE.

5. SUBTASK 70-31-02-310-002 Precautions to Decrease the Risk of Distortion

   1. To decrease the risk of distortion on large casings, attach them with a clamp to a rigid baseplate. This will hold them when they are welded or during subsequent heat treatment.

      NOTE

      Chill plates must have a groove to clear the weld line. The groove can also be used to supply the argon to the back of the weld.

   2. Chill plates that have the contours of the parts must be used to remove heat when there is a risk of unwanted distortion.

   3. Copper chill plates must be chromium plated to prevent contamination of the weld with copper.

6. SUBTASK 70-31-02-310-003 The Equipment Necessary to make a Weld

   1. All welding plant and equipment must be maintained to the manufacturer's instructions. Make sure the equipment works correctly before you start welding.

   2. The equipment must give sufficient argon coverage before the arc is made and after the weld run is completed. The equipment must permit the supply of argon to the opposite side of the weld. When argon is fed to the underside of the weld a separate flow meter shall be used. The argon supply to the torch and fixture shall be free from leaks.

   3. Tubing For The Supply Of The Argon

      NOTE

      It is permitted to use alternative tube material if the alternative tube material has no negative effect on the quality of the argon gas, the welding equipment, or the welds.

      1. To transfer the argon from the permanent metallic pipe work (wall source) to the weld power unit use metallic pipework or PTFE tubing.

      2. To transfer argon from the power unit to the welding torch use Polychloroprene (Neoprene).

      3. For argon backing lines use Polychloroprene (Neoprene).

         NOTE

         A rectifier with an output range of 10 to 150 amperes will be sufficient for most applications, but one with a range of 5 to 300 amperes recommended. The current range shall be adjustable in small increments or linearly over the range of the power source. The meter scale shall enable small current increments to be readily seen.

   4. The current output of the equipment must be compatible with the thickness and composition of the materials to be welded.

   5. The arc must be initiated by a high frequency (HF) or impulse generated spark. Touch starting of the arc is not permitted. Automatic control to increase the weld current from the minimum necessary for arc initiation to the pre-set weld current over the first few seconds of the weld sequence is permitted.

      1. To prevent the formation of stop craters, or cracks, when the arc is extinguished, a method of current decay control is permitted.

   6. 

      CAUTION

      POOR EARTH CONTACT CAN CAUSE ARC DAMAGE ON THE PART AWAY FROM THE AREA BEING WELDED.

      To prevent arc damage a good earth connection shall be made either directly onto the component, or to the fixture in which the component is secured. Do not rely on the connection of the earth lead to the electrical contact on the bench.

   7. 
      WARNING
      DO NOT BREATH DUST PARTICLES WHEN SHARPENING THORIATED TUNGSTEN ELECTRODES. THORIUM EMITS ALPHA RADIATION, OBEY LOCAL HEALTH AND SAFETY PROCEDURES FOR SAFE WORK PRACTICES.

      Electrodes

      NOTE

      The different types of electrode have different emissivity, if the electrode type is changed then automatic welds must be revalidated.

      NOTE

      If the repair documentation calls for Thoriated elctrodes for manual welds then the alternatives quoted below can be used.

      1. For DCEN output welding Thoriated, Ceriated or Lanthanated tungsten electrodes can be used.

      2. For AC output welding either Thoriated, Zirconated, Ceriated, or Lanthanated tungsten electrodes can be used.

7. SUBTASK 70-31-02-310-004 Preheating Before you Weld

   1. For a satisfactory weld some metal types must be heated before they are welded. When it is necessary to pre-heat the material you must use one of the procedures that follow:

      1. Put the part in a cool furnace and slowly increase the temperature of the component in a small amounts to the specified temperature. After the necessary time, remove the part and weld it while it is hot.

         A blanket element may be attached behind the weld area to keep the pre-heat temperature.

      2. If specified by the Engine Manual, the part can be locally pre-heat with a blanket element where the weld is to be made.

      3. If you cannot use these procedures, and it is permitted by the engine Manual, locally pre-heat the part with a flame or torch. This procedure is not recommended but if it is used you must take care not to let the component become too hot.

8. SUBTASK 70-31-02-370-001 Heat Treatment After you Weld

   1. Rigid casings and parts on which weld distortion affect the fit of the part in the engine shall be heat treated in a furnace.

   2. Where the weld distortion is local and acceptable, particularly on large fabricated parts, the use of thermal blanket heating elements may be accepted.

      1. For a details of specific heat treatment requirements, refer to the Engine Manual and the SPM TASK 70-31-02-310-501-004.

9. SUBTASK 70-31-02-370-002 The Local Heat Treatment of Repair Welds

   
   CAUTION
   WELDS ON PARTS THAT ROTATE MUST NOT BE GIVEN LOCAL HEAT TREATMENT UNLESS SPECIFIED IN THE APPLICABLE REPAIR.
   
   CAUTION
   LOCAL HEAT TREATMENT SHALL ONLY BE USED WHERE THE GEOMETRY OF THE COMPONENT ALLOWS ADEQUATE ACCESS FOR HEATING ELEMENTS. INCORRECT PLACEMENT OF HEATER ELEMENTS, THERMOCOUPLES OR INSULATION CAN CAUSE OVERHEATING OF COMPONENTS OR UNDER HEATING OF REPAIR WELDS.

   1. General.

      This subtask is for the local heat treatment of repair welds on engine parts with Flexible beaded heating elements, blanket elements and heating tape used as an alternative to a furnace. The use of this type of equipment is specified in the applicable Repair. This type of heat treatment removes the problems of putting large components in furnaces and with the distortion of parts.

   2. Two suppliers of local heat treatment equipment are as follows:

      Supplier code number: KD475.

      Supplier code number: U0891.

   3. Prepare the surfaces that are to be heat treated as follows:

      1. Make sure that the surface to be treated is dry and that grease, paint or other unwanted material has been removed.

         NOTE

         The heating elements and the surrounding area must be well insulated (lagged) with suitable refractory blankets to retain the heat.

      2. Make sure the heating surface of the element is in complete contact with the surface to be heated.

   4. The electrical power must be supplied through a variable transformer, for example, a welding plant control unit.

   5. The equipment shall have a temperature recorder or indicator, a recorder is recommended.

   6. A rate of increase in temperature of 18 deg F per minute (10 deg C per minute) maximum is recommended.

   7. Time shall be allowed for the heat to soak through the part and for the temperature to stabilise before the heat treatment time begins.

   8. Temperature Control.

      1. Thermocouples that can get to 1832 deg F (1000 deg C) must be used. They must be attached to the component, or as near to the surface as possible, but must not touch the element.

      2. Each heater element must have an independent temperature control.

      3. For complicated geometries or large areas several monitor thermocouples should be used to make sure uniformity of heat treatment.

      4. Thermocouples may be attached by micro-spot welds.

   9. After heat treatment the component shall be allowed to cool under the insulation.

10. SUBTASK 70-31-02-310-007 Test the Competency of the Welder

    1. Welders must be fully approved by the applicable regulatory authority.

    2. When you test the competency of a welder to repair aluminum castings, a satisfactory test will be as follows:

       1. Do a usual repair weld in a piece of discarded casing of the applicable material.

       2. Visually inspect the quality of the weld.

       3. Examine the weld radiograpically to a specified method.

       4. Cut the sample across the weld and examine the micro-structure for signs of porosity and other defects if specified.

11. SUBTASK 70-31-02-220-001 Inspection of Welds

    1. General.

       1. This subtask gives the quality acceptance standard for visual inspection of butt and fillet welds. Individual repair schemes take precedence over the requirements of this section.

       2. In this subtask, "t" is the material thickness.

       3. For weld build up repairs, the requirements of this standard shall be met with the exception of the geometric requirements. For porosity assessment, "t" will be the depth of the build up to a maximum of 3 mm, the repair scheme may give additional requirements.

       4. Where adjacent parts have differing thickness, the sectional thickness of the thinner must be taken as representative of t.

    2. Pre-weld inspection:

       1. The joint faces must be clean.

       2. All other faces must be clean for a minimum of 0.250 inch (6.35 mm) each side of the weld.

       3. Figure shows acceptable step conditions in butt weld joints at the pre-weld inspection.

       4. For filled welds, joint edge spaces to a maximum of 30%t are permitted.

       5. In fillet weld joints, joint face spaces of 15%t are permitted before welding.

       6. Joint edge gaps of 10% for unfilled welds.

    3. Post weld inspection.

       Table 2. Butt Welds

       Feature		Requirement
       Concavity		Permitted up to 10%t provided it blends smoothly with the parent metal, see Figure.
       Weld bead		Weld beads must blend smoothly into the parent metal.
       Maximum weld crown height		50%t for manual welds (Aluminum 100%t maximum) 30%t for mechanical welds (Aluminum 50%t maximum) See Figure.
       Maximum bead penetration		50t for manual or mechanical welds (Aluminum 100%t) See Figure. Excessive penetration seen as large particles of weld metal on the opposite side of the weld is not permitted.
       Lack of penetration and fusion		Not permitted. See Figure. Lack of fusion is not permitted.
       Parent metal thinning		Maximum 10%t. See Figure.
       Undercutting		Less than 10%t is permitted provided there is no sharp change of section. See Figure.
       Cracks		Not permitted in the weld or adjacent heat affected zone (HAZ).
       Porosity		Isolated pores are permitted provided that: They have a minimum separation of 1.00 inch (25.4 mm). The depth is not more than half the diameter of the pore. The depth does not exceed: 30%t in Group 1 welds 40%t in Group 2 welds 50%t in Group 3 welds.
       Stop and start craters		Not permitted in Group 1 and Group 2 welds. In Group 3 welds, maximum permitted diameter is 0.030 inch (0.75 mm)
       Weld width		Maximum Figure Welds shall be consistent with full penetration of the weld. The weld bead shall have uniform width; local variations are permitted up to 1.5 W Figure.
       Changes in the weld path direction		Changes in the weld path must be smooth and uniform. The maximum permitted deviation is 25 percent W in a distance of 3W. See Figure.
       Arc damage		Arc damage to the part at the earthing contact or fixture is not permitted.
       Heavy oxidation		Not permitted.
       Titanium discolouration		Refer to Step.

       Table 3. Fillet welds

       Feature		Requirement
       Weld beads		Must be blend smoothly with the parent metal but can range in shape from lightly convex to lightly concave.
       Bridging		Not permitted See Figure
       Undercutting		10%t is permitted provided there is no sharp change in the section.
       Overlap and blunt toes		Not permitted See Figure
       Complete penetration of the material		Not permitted unless suitable argon backing has been used.
       Arc damage		Arc damage to the part at the earthing contact or fixture is not permitted.
       Heavy oxidation		Not permitted
       Titanium discolouration		Refer to Step.

12. SUBTASK 70-31-02-860-004 Weld Classification

    1. There are three groups of welded joint as follows:

       Group 1		Highly or lightly stressed weld - failure or leakage will have an effect on the safety of the aircraft - basic inspection procedures together with radiographic and penetrant or radiographic and magnetic inspection must be done on these welds.
       Group 2		Highly stressed weld - failure or leakage will not have an effect on the safety of the aircraft - basic inspection procedures together with radiographic or penetrant or magnetic inspection must be done on these welds.
       Group 3		All other welds, basic inspection procedures must be done.

    2. In all three groups the requirements must be met unless otherwise stipulated in the engine manual.

    3. If no classification is given in the Engine Manual, the weld shall be assumed to be a Group 3 weld but the inspection requirements in the repair scheme shall be followed.

13. SUBTASK 70-31-02-310-005 Do a Bend Test on the Titanium Welds

    1. If there is a concern about the effectiveness of the shielding of a titanium weld then a bend test out on a sheet test piece.

    2. Any test piece requirement will be specified in the Engine Manual.

14. SUBTASK 70-31-02-230-001 Penetrant and Magnetic Particle Inspection Procedure of Welds

    1. Where there is a requirement for Fluorescent Penetrant or Magnetic Particle Inspection this will be specified in the Engine Manual. Parts are examined with penetrant or magnetic particles to find surface defects. The indications must be examined with a X5 to X10 lens.

    2. Refer to the SPM TASK 70-23-00-230-501 Fluorescent Penetrant Inspection - General Information for information on fluorescent penetrant inspection methods and control.

    3. Refer to the SPM TASK 70-24-00-240-501 Magnetic Particle Inspection - General Information, and SPM TASK 70-24-01-240-501 Magnetic Particle Inspection Procedures, for the information on magnetic particle inspection method and control.

    4. Defects must be contained within the weld and separated by defect free weld to be permitted as specified in Step.

15. SUBTASK 70-31-02-260-001 Radiographic Inspection Procedure of Welds

    1. If radiographic inspection is necessary, this will be specified in the Engine Manual in accordance with the weld classification.

    2. In addition to the radiographic inspection requirement associated with the weld classification, radiographic inspection may be required on welds where subsurface defects are likely to occur, such as, weld build up.

    3. Refer to the SPM TASK 70-26-01-260-501 for methods and control of radiographic inspection.

    4. Radiological inspection acceptance standard.

       The repair scheme may override the requirements of this specification.

       Table 5. Butt welds

       DEFECT		GROUP 1		GROUP 2		GROUP 3
       Cracks		None		None		None
       Re-entrant effect		None		None		None
       Heavy oxidation (coking).		None		None		None
       Lack of penetration		None		None		None
       Lack of fusion		None		None		0.25 inch (6.35 mm) long, below the surface and 2.00 inches (50.8 mm) apart
       Cavities		Spherical, below the surface, 50%t and 1.00 inch (25.4 mm) apart
       Non-metallic inclusions		0.075 inch (1.91 mm) major dimension and 2.00 inches (50.8 mm) apart, no sharp corners.
       Tungsten inclusions		0.025 inch (0.64 mm) major dimension or 50%t maximum and 50 mm apart
       Porosity, see Figure		1-A,B,C,D 2-B,C,D,E 3-C,D 7		1-A,B,C,D 2-B,C,D,E 3-C,D 7		1-A,B,C,D 2-B,C,D,E 3-C,D 4-D 7 8
       Interdendritic shrinkage (IDS)		0.075 inch (1.91 mm) long		0.100 inch (2.54 mm) long		0.150 inch (3.80 mm) long
       Undercut		10%t if there is no sharp change in section
       Thinning		10%t if there is no sharp change in section

       Table 6. Fillet welds

       DEFECT		GROUP 1		GROUP 2		GROUP 3
       Cracks		None		None		0.100 inch (2.54 mm) long 2.00 inches (50.8 mm) apart
       Re-entrant effect		None		None		None
       Heavy oxidation (coking)		None		None		None
       Lack of root penetration		A total of 0.25 inch (6.35 mm ) or 30% of length. Use the lower value.		A total of 0.25 inch (6.35 mm) or 30% of length. Use the lower value.		A total of 0.50 inch (12.7 mm) or 30% of length. Use the lower value.
       Cavities		Spherical, below the surface 80%t and 1.00 inch (25.4 mm) apart
       Non-metallic inclusions		0.125 inch (3.17 mm) major dimension and 2.00 inches (50.8 mm) apart, no sharp corners.
       Tungsten inclusions		0.025 inch (0.65 mm) major dimension		0.050 inch (1.27 mm) major dimension		0.050 inch (1.27 mm) major dimension
       Porosity, see Figure		1-A,B,C,D 2-B,C,D,E 3-C,D 7 8		1-A,B,C,D 2-B,C,D,E 3-B,C,D 7 8		1-A,B,C,D 2-A,B,C,D,E 3-A,B,C,D,E 4-D 7 8 9-A,B,C
       Thinning		10%t. If there is no sharp change in section.
       Undercut		None		None		None

16. SUBTASK 70-31-02-260-002 Radiographic Inspection of Welds in Light Alloy Castings

    1. There are two standards of inspection given for welds in light alloy castings: Standard A and Standard B. Standard A is the highest.

       NOTE

       Standard A must only be used when it is specified in the Engine Manual in which various angles of X-ray shots are usually recommended.

       1. Standard A.

          1. Sharp line indications are not permitted.

          2. Tungsten inclusion indications of not more than 0.025 inch (0.64 mm) diameter maximum are permitted, provided the defects are separated by 50 mm minimum.

          3. Porosity indications of not more than 0.050 inch (1.27 mm) diameter maximum are permitted, provided the defects are separated by 50 mm minimum.

          4. Lack of penetration or fusion is not permitted.

             NOTE

             This standard is relevant to all welds in light alloy materials where the Engine Manual specifies radiographic inspection but does not give a standard.

       2. Standard B.

          1. Sharp line indications are not permitted.

          2. Tungsten inclusion indications of not more than 0.025 inch (0.64 mm) diameter maximum are permitted, provided the defects are separated by 25 mm minimum.

          3. Porosity indications of not more than 0.050 inch (1.27 mm) diameter maximum are permitted, provided the defects are separated by 25 mm minimum.

          4. Lack of penetration of fusion is not permitted.

17. SUBTASK 70-31-02-220-002 Visible Inspection of Titanium Welds

    1. Do not blend or polish titanium welds unless specified in the Engine manual. If it is necessary to blend or polish titanium welds visual inspection must be carried out first. Visual inspection must take place before heat treatment which may affect the discolouration.

    2. Discolouration.

       1. Silver to light straw weld beads are acceptable.

       2. Dark straw, Blue, Grey and White weld beads are unacceptable.

       3. Dark straw to blue is acceptable in the heat affected zone parallel to the weld bead provided that it does not encroach on the weld bead. Subsequent welds must not be carried out on an area which has discoloured.

18. SUBTASK 70-31-02-310-010 Rewelding

    1. Weld defects may be dressed out and rewelded. When dressing out defects minimum metal shall be removed. Wherever possible the dressing shall be confined to the weld.

    2. If the defect is not repaired successfully after three attempts, the method of repair should be changed or the part scrapped.

    3. All rewelds must be inspected using the technique used to inspect the original weld and be assessed to the original standard.

    4. Rewelding of discoloured titanium welds is NOT permitted.

19. SUBTASK 70-31-02-310-008 Materials to be Welded and Filler Wire

    1. For approved examples of materials to be welded and the recommended filler wire, refer to the SPM TASK 70-31-02-310-501-002.

20. SUBTASK 70-31-02-310-009 Orbital Torch Welding

    1. This subtask is deleted. Refer to the SPM TASK 70-31-02-310-501-003.

21. SUBTASK 70-31-02-860-002 Equipment and Materials.

    1. Equipment and Materials - deleted.

22. SUBTASK 70-31-02-310-006 Weld Test Samples

    1. Weld Test Samples - deleted.

Figure: Permitted butt joint step conditions

Permitted butt joint step conditions



Figure: Butt weld

Butt weld



Figure: Butt weld

Butt weld



Figure: Butt weld

Butt weld



Figure: Fillet weld

Fillet weld



Figure: Porosity limits

Porosity limits



Figure: Visual inspection limits

Visual inspection limits



Figure: Overlap and Blunt toe

Overlap and Blunt toe