803WELDING ALUMINUM ALLOYS

803.01Description

This work shall consist of welding aluminum alloys for highway structures. The welding terms used shall be in accordance with definitions included in the AWS Definitions “MD” Welding and Cutting, AWS A3.0. Special conditions shall be fully explained by means of added notes or details.

The aluminum alloys to be welded under these specifications may be any of the following ASTM alloy designations: 10

5052, 5083, 5086, 5456;

MATERIALS

803.02Materials

Materials shall be in acco rdance with the following:

Electrodes .................................................................... 924.01 Filler Material .............................................................. 924.01 Shielding Gases ........................................................... 924.01 Welding Rods .............................................................. 924.01 803.01

Material used for permanent backing shall be at least equivalent in weldability to the base metal being welded. 30

803.03Welding Processes

The welding process shall be by the gas metal-arc process or the gas tungsten-arc process. Other processes may be used if prior approval is given.

Joint details shall be in accordance with design requirements and detail drawings. The location of joints shall not be changed without approval.

Edge preparation shall be by sawing, machining, clipping, or shearing. Gas 40 tungsten-arc or gas metal-arc cutting may also be used. Cut surfaces shall meet the ANSI surface roughness rating value of 1000. Oxygen cutting shall not be used.

Surfaces and edges to be welded shall be free from fins, tears, and other defects which would adversely affect the quality of the weld. Dirt, grease, forming or machining lubricants, and organic materials shall be removed from the areas to be welded by cleaning with a suitable solvent or by vapor degreasing.

The oxide shall be removed from all edges and surfaces to be welded by wire brushing or by other mechanical methods such as rubbing with steel wool or abrasive 50 cloth, scraping, filing, rotary planing, or sanding just prior to welding. If wire brushing is used, the brushes shall be made of stainless steel. Hand or power driven wire brushes which have been used on other materials shall not be used. Where mechanical methods of oxide removal are found to be inadequate, a standard chemical method shall be used. Welding shall be done within 24 h after chemical treatment. When gas tungsten- arc welding with direct curr ent straight-polarity is bei ng used, all edges and surfaces to be welded shall have the oxide removed by a standard chemical method.

Welding shall not be done on anodically treated aluminum unless the condition is removed from the joint area to be welded. 60

All butt welds requiring 100% penetration, except those produced with the aid of backing, shall have the root of the initial weld chipped or machined out to sound metal before welding is started from the second side. Butt welds made with the use of backing shall have the weld metal fused w ith the backing. Where accessible, backing for welds that are subject to computed stress or which are exposed to view on the completed structure and which are not otherwise parts of the structure, shall be removed and the joints ground or machined smooth. In tubular members, butt welds subjected to computed stresses shall be made with the aid of permanent backing rings 70 or strips.

The procedure used for production welding of any particular joint shall be the same as used in the procedure qualification for that joint. 803.03

All welding operations, either shop or field, shall be protected from air currents or drafts so as to prevent any loss of gas shielding during welding. Adequate gas shielding shall be provided to protect the molten metal during solidification. The work shall be positioned for flat position welding whenever practicable. All weld joints shall be dry at the time of welding. 80

The size of the electrode, voltage and amperage, welding speed, gas or gas mixture, and gas flow rate shall be suitable for the thickness of the material, design of joint, welding position, and other circumstances attending the work. Gas metal-arc welding shall be done with direct current, reverse polarity. Gas tungsten-arc welding shall be done with alternating current or with direct current, straight polarity.

When the joint to be welded requires specific root penetration, the Contractor shall make a sample joint and a macro etched cross-section of the weld to demonstrate that the joint welding procedure to be used is attaining the required root penetration. The 90 sample joint shall have a length of at least 1 ft and shall be welded with the electrode, polarity, amperage, voltage, speed, gas mixture, and gas flow rate that are proposed to be used in production welding. Evidence on record may be accepted in lieu of the receding test.

Where preheat is needed, the temperature of preheat shall not exceed 350°F for heat-treated alloys and 600°F for non-heat-treated alloys. The temperature shall be measured by temperature indicating crayons or by pyrometric equipment. Heat-treated alloys shall not be held at the maximum pr eheat temperature or at temperatures near the maximum for more than 30 minutes. 100

Welds will not be accepted if they contain cracks in the welds or in the adjacent base metal, copper inclusions, or porosity in excess of that allowed by the AWS D1.2 Structural Welding Code.

Lack of fusion, incomplete penetration, or tungsten or oxide inclusions will be acceptable only if small and well dispersed.

Undercut shall be no more than 0.01 in. deep when its direction is transverse to 110 the primary stress in the part that is undercut. Undercut shall be no more than 1/32 in. deep when its direction is parallel to the primary stress in the part that is undercut. Overlap shall not be allowed. All craters shall be filled to the full cross-section of the welds. Welds having defects greater than the levels of acceptance specified herein shall be considered as rejected unless corrected in accordance with 803.03(e).

All welds shall be inspected visually to determine compliance with 803.03(c). In addition, all welds subjected to computed stress shall be inspected by the dye penetrant method except as specified below. For highway sign structures, the dye penetrant 120 method shall be used on butt welds in columns and main chord members; on fillet 803.03

welds connecting columns to bases and main chord members, including the associated flanges, gussets, or main load carrying brackets or members; and on fillet welds connecting flanges to the main truss chord members. The dye penetrant tests shall be performed in accordance with ASTM E165, method B. Dye penetrant inspection may be omitted provided that the inspector examines each layer of weld metal with a magnifier of 3X minimum before the next successive layer is deposited.

In lieu of rejection of an entire piece or member containing welding which is 130 unacceptable, the corrective m easures listed below may be allowed if approval is obtained prior to making each repair. Defective welds shall be corrected by removing and replacing the entire weld, or as follows:

The full extent of cracks shall be determined by dye penetrant method or other positive means. The cracks shall be removed throughout their length and depth, and rewelded.

All defective portions shall be removed and rewelded.

All defective portions shall be removed and rewelded.

The weld shall be cleaned and additional weld metal shall be deposited.

Overlap shall be reduced by removal of the excess weld metal. 150

The defective areas shall be removed by chipping or machining. Oxygen cutting shall not be used. Before rewelding, the joint shall be inspected to ensure all the defective weld has been removed. If dye pe netrant has been used to inspect the weld, all traces of penetrant solutions shall be re moved with solvent, water, heat, or other suitable means before rewelding.

803.04Qualification of Procedures, Welders, and Welding Operators

Joint welding procedures shall be qualified previously by tests prescribed in the AWS D1.2 Structural Welding Code. Evidence of previous qualification of the joint 160 welding procedures to be employed may be accepted.

All welders and welding operators shall be previously qualified by tests in accordance with the AWS D1.2 Structural Welding Code. Evidence of previous qualification of the welders and welding ope rators to be employed may be accepted. The same process and type of equipment that is required for execution of the contract work shall be used in qualifying welders and welding operators.

803.04