Lecture 5

Damascus University Spring 2015 Instructor: Dr. Nachwan Khair

UK EUROCODES

Lecture 5

Welding Welding is the process of joining metal parts by fusing them and filling in with molten metal from the electrode

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Figure illustrates the shielded manual metal arc-welding process

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Automatic welding using a continuous coated electrode

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Submerged arc-welding (SA). Lecture 5

Gas shielded welding metal arc inert gas (MIG).

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Advantages of welding Welding offers many advantages over other joining methods:

Freedom of design, and the opportunity to develop innovative structures;

Easy introduction of stiffening elements; Less weight than in bolted joints because

fewer plates are required; (50t the Wall Viaduct) Welded joints allow increased usable space

in a structure; Protection against the effects of fire and

corrosion are easier and more effective. Lecture 5

Defects and testing of welding

Cracks can occur in welds and adjacent parts of the members being joined

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Defects and testing of welding

Faulty welding procedure can lead to the following defects in the welds, all of which reduce the strength:

1. Over-reinforcement and undercutting; 2. Incomplete penetration and lack of side-wall fusion; 3. Slag inclusions and porosity.

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Tests applied to welding

1. Visual inspection for uniformity of weld;

2. Surface tests for cracks using dyes or magnetic particles;

3. X-ray and ultrasonic tests to check for defects inside the weld.

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Types of welds The two main types of welds:

Butt weld Fillet weld

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Design of butt welds The design resistance of a full penetration butt weld should be taken as equal to the design resistance of the weaker of the parts connected, provided that the weld is made with a suitable consumable which will produce all-weld tensile specimens having both a minimum yield strength and a minimum tensile strength not less than those specified for the parent metal.

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Fillet welds Fillet welds may be used for connecting parts where the fusion faces form an angle of between 60 and 120.

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Fillet welds finishing at the ends or sides of parts should be returned continuously, full size, around the corner for a distance of at least twice the leg length of the weld, unless access or the configuration of the joint renders this impracticable.

Fillet welds

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Intermittent fillet welds 1.Intermittent fillet welds should not be used in

corrosive conditions. 2.In an intermittent fillet weld, the gaps (L1 or L2 )

between the ends of each length of weld Lw should fulfil the requirement given in Figure 4.1.

3. In an intermittent fillet weld, the gap (L1 or L2 ) should be taken as the smaller of the distances between the ends of the welds on opposite sides and the distance between the ends of the welds on the same side.

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Intermittent fillet welds 4.In any run of intermittent fillet weld there should

always be a length of weld at each end of the part connected.

5.In a built-up member in which plates are connected by means of intermittent fillet welds, a continuous fillet weld should be provided on each side of the plate for a length at each end equal to at least three-quarters of the width of the narrower plate concerned (see Figure 4.1).

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Intermittent fillet welds The smaller of Lwe 0,75 b and 0,75 b1 For build-up members in tension: The smallest of L1 16 t and 16 t1 and 200 mm For build-up members in compression or shear: The smallest of L2 12 t and 12 t1 and 0,25b and 200 mm.

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