Welding joints: types of seams and joints

In carrying out welding work obtained various compounds.Welding seams can be connected not only metals, but other dissimilar materials.Stacked in a one-piece assembly elements is a compound that can distinguish between several sites.

Zone weld joint

compound obtained in the process of welding is divided into these zones:

• fusion place - the boundary between the base metal and weld metal obtained.In this zone are grains that differ in their structure from the state of the parent metal.This occurs due to partial melting during the welding process.FIELD
• HAZ - zone of the base metal which has not undergone melting, although in the process of heating the metal structure it has been changed.
• weld - a site that formed during crystallization during cooling of the metal.

types of welded joints

Depending on the location of the abutting items relative to each other compounds are divided into these types:

1. butt.Joining of construction elements is performed in one plane end faces to each other.Depending on the different thicknesses of the parts can ends relative to each other vertically displaceable.
2. Angle connection.In this case, the combination of the ends is made at an angle.The welding process is carried out on the edges of adjacent parts.
3. lap joints.Details for welding disposed in parallel with partial overlap.
4. end connection.Sealing members aligned parallel to each other and are joined at the ends.
5. T-joints.In this case, the end of one part is adjacent to another side of the angle.

welded joints and characterize types of welds, which can be qualified in some respects.

Indicators weld

There are several parameters that can be characterized by all received welds:

• width - is the size of the seam between the boundaries that are drawn visible weld lines;
• root of the weld - its reverse side, which is in the maximum distance from the front side;
• bulge - determined in the most convex part of the joint and the distance from the plane of the base metal to the border most of the projection;
• concave - this indicator is relevant if it has a place in the weld because, in fact, is a defect;This parameter is determined at the point where the seam has a maximum deflection - away from the plane of the base metal measured size concavity;
• leg seam - it takes place only in the corner and T-joints;measured by this indicator closest to the lateral surface of the workpiece to a restrictive line on the surface of the second seam.

Types of joints by the method of execution

• sided welds.They are performed with full penetration of the metal over the entire length.
• Bilateral execution.According to the technology after unilateral welding, the weld root is removed, and only after this welding is performed with the other hand.
• Single-layer joints.Performs single-pass welding with a single weld bead.
• Multilayer seams.They should be used in thick metal, that is, when run in a single pass welding is not possible by technology.Layer seam will consist of several rollers (passes).This will limit the spread of the field of thermal effects and get a solid and high-quality weld.

Types of welds on the spatial position and extent

There are such provisions welding:

• lower when the weld seam is at the bottom of the horizontal plane, that is. E. 0º angle relative to the ground;
• horizontal direction of the welding is carried out horizontally, and the item can be at an angle of 0º to 60º;
• vertical welded in this position the surface is in the plane of 60º to 120º, and welding is carried out in a vertical direction;
• ceiling when the work is carried out at an angle 120-180º, ie welds are located above the master;
• "in the boat", that provision refers only to the corner or T-joints, the item exhibited at an angle, and welding is carried out "in a corner".

breakdown length:

• continuous as performed nearly all joints, but there are exceptions;
• broken seams, they take place only in the corner joints;Bilateral joints of this type can be carried out in a staggered and in the chain manner.

Cutting Edge

This design feature is used in the case where the thickness of the metal used for welding, larger than 7 mm.Cutting edge - the removal of metal from the edges in some form.This process is performed in the one-pass welding of butt joints.This is necessary in order to get a correct weld.As for the thick material cutting needed to initially melted the root canal and then following the deposited bead uniformly filling the cavity boil throughout the thickness of the metal.

cutting edges can be carried out, if the thickness of the metal is not less than 3 mm.Because lower temperatures lead to burn-through.Cutting is characterized by design parameters: gap - R;included angles - α;dullness - with.The location of these parameters shows a drawing of the weld.

cutting edges increases the amount of consumables.Therefore, this value are trying to minimize.It is divided into several types by design:

• V-shaped;
• X-shaped;
• Y-shaped;
• U-shaped;
• crevice.

Features cutting edges

For small welding material thickness of 3 mm to 25 mm is usually applied one-sided V-shaped cutting.The bevel can be performed on both faces or on one of them.The metal thickness of 12-60 mm it is advisable to weld with two-way X-shaped butchering.The angle α at cutting in X, V shape is 60º, if the bevel is performed on only one edge, the value α is equal to 50º.For the thickness of 20-60 mm is the most economical consumption of the deposited metal in the U-shaped cutting.The bevel may also be arranged on one or both ends.Blunting be 1-2 mm, and the gap value is equal to 2 mm.For a large metal thickness (over 60 mm), the most effective way would be slotted cutting edges.For welded joints is very important this procedure, it affects several factors seam:

• performance compound;
• strength and quality of the weld;
• economy.

Standards and guests

1. manual arc welding.Weld seams and connections in accordance with GOST 5264-80 include types, design dimensions for welding, coated electrodes in all positions.This does not include only steel piping.
2. welding steel pipes.GOST 16037-80 - defines the basic types, cutting edges, structural dimensions with mechanized welding.
3. pipeline welding of copper and copper-nickel alloys.GOST 16038-80.
4. Arc welding of aluminum.Welded seams.GOST 14806-80 - the shape, size, edge preparation for manual and mechanized welding of aluminum and its alloys, the process is performed in a protective atmosphere.
5. submerged.GOST 8713-79 - welding seams and connections are automated or mechanized welding in the air, on the flux cushion.Distributed on the metal thickness of 1.5 to 160 mm.
6. aluminum welding in inert gases.GOST 27580-88 - the standard for the manual, semiautomatic and automatic welding.It is performed by a non-consumable electrode in an inert gas with filler material and the aluminum cover thickness of 0.8 to 60 mm.

designation weld

According to the regulations the presence of welds is shown on the assembly drawings and the general appearance.Welds depicted by solid lines, if they are visible.And if on the contrary - the broken segments.From these lines are removed callouts with one-way arrows.Symbol of welds performed on the shelf by the leader.Inscription is above the shelf, if the seam is on the front side.In the other version designation will be under the shelf.This includes information about the seam in the following sequence:

• Auxiliary signs.At the intersection of leader can stand with shelf icon:

○ - closed seam;

┐ - weld seam is produced during installation.

• designation welds, structural elements and their compounds GOST.
• Name seam standard.
• welding method of regulatory standards.
• Specify leg, this paragraph only applies to the corner joints.
• seam discontinuity, if any.This specifies the location of the pitch and welding segments.
• Additional icons auxiliary values.Consider them as a separate item.

Auxiliary designations

These signs are also applied on top of the shelf, if the weld visible in the drawing, and under it when the invisible:

• removing the weld reinforcement;
• surface treatment that will ensure a smooth transition to the base metal, excluding nodules and irregularities;
• seam is performed on an open line;This mark applies only to visible welds in the drawing;
• surface finish of the joint.

To simplify, if all seams construction made by one guest, have the same cutting edge design and dimensions, marking and welding standards specified in the specifications.The design may not be anything but a large number of identical stitches.Then they were split into groups and assigns them a sequence number to each group separately.At one point the seam full designation.The rest put only serial numbers.The number of groups and the number of stitches in each of them must be specified in the standard documentation.