- 1 Welding joints: types of seams and joints
- 2 Varieties and technology of welding seams - ceiling, horizontal, vertical
- 3 Types of welds and seams
Welding joints: types of seams and joints
In carrying out welding operations produce different compounds. Welds can be connected not only metals but also other dissimilar materials. Stacked in one-piece assembly elements comprise a compound which can differentiate into several sections.
The compound obtained in the welding process divided into such zones:
- Position fusion - 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 thermal influence - the base metal zone which is not subjected to reflow, although during heating of the metal, its structure has been changed.
- The welding seam - portion which is formed during the crystallization in the cooling of the metal.
Depending on the location of the abutting items each are divided into types relative to each other such compounds:
- 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.
- Gusset. 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.
- Compound overlap. Details for welding arranged in parallel with partial overlap.
- End connection. Weldable elements are aligned parallel to each other and are joined at the ends.
- T-joint. In this case, one end parts adjacent to the other side portion at an angle.
Welding connections also characterize the types of welds, which can be qualified in some respects.
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;
- weld root - the reverse side thereof which is in the maximum distance from the front side;
- bulge - is determined in the most convex part of the joint and is denoted the distance from the plane of the base metal to the highest protrusion boundary;
- 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 the greatest deflection - by him to the ground metal plane size measured concavity;
- cathetus seam - it occurs only in the corner and T-joints; measured in this figure the smallest distance from the side surface of one work piece before the preamble seam line on the second surface.
Types of sutures by the method of execution
- Unilateral welds. They are executed with full metal penetration along the entire length.
- Two-way design. 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 seams. Single pass welding performed with a single weld bead.
- Multilayer seams. Their use is expedient when a large thickness of the metal, i.e. when to perform welding in a single pass is not possible for the 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 length
Distinguish such welding position:
- lower when welded seam located in a lower horizontal plane ie 0º angle relative to the ground..;
- horizontal welding direction being horizontal and the item can be angled from 0º to 60º;
- vertical, in this position weldable surface is in plane from 60º to 120º, and welding is carried out in the vertical direction;
- Ceiling when the work is carried out at an angle 120-180º, that is, the welds are located above the master;
- "In the boat", that provision refers only to the corner or T-joints, the item is set at an angle, and welding is carried out "in a corner."
The breakdown by length:
- continuous, so it runs almost all joints, but there are exceptions;
- Intermittent stitches, they occur only at the corner joints; Bilateral joints of this type can be carried out both in chess and in the chain order.
This design feature applies in the case where the thickness of the metal used for welding, more than 7 mm size. Cutting edge - is removal of metal from the edges in some form. This process is performed when the single pass welding of butt joints. This is necessary in order to get a proper weld. As for thick material, cutting is required to initially melted the root pass and then next bead uniformly filling the cavity boil throughout the thickness of the metal.
Cutting edges can be performed if the metal thickness is less than 3 mm. Because of its lower value will result in burn-through. Cutting is characterized by the constructive parameters: gap - R; corner cutting edges - α; dullness - with. The location of these parameters shows a drawing of the weld.
Beveling increases the amount of consumables. Therefore, this value are trying to minimize. It is divided into several types by design:
For small thicknesses of material to be welded from 3 to 25 mm are normally used one-sided V-shaped cutting. The bevel may be performed at both ends or at one of them. Metal 12-60 mm it is advisable to weld with double sided X-shaped bunching. 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 would be most economical rate of weld metal when U-shaped cutting. The bevel may also be formed on one or both ends. Dullness 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 is slit cutting edges. For the welded joint is very important this procedure, it affects several joint factors:
- functionality compound;
- strength and quality of the weld;
- Manual arc welding. GOST 5264-80 welds and compounds include types, design dimensions for welding coated electrodes in all spatial positions. This does not include only steel piping.
- Welding steel pipes. GOST 16037-80 - defines the basic types, cutting edge design sizes at the mechanized welding method.
- Welding pipes made of copper and copper-nickel alloys. GOST 16038-80.
- Arc welding of aluminum. Welded seams. GOST 14806-80 - shape, size, edge preparation for manual and mechanized welding of aluminum and its alloys, the process is performed in a protective atmosphere.
- Submerged arc. GOST 8713-79 - welding seams and connections are made automatic or mechanized welding on weight, on flux cushion. It extends to the metal thickness of 1.5 to 160 mm.
- Welding of aluminum in inert gases. GOST 27580-88 - standard on the manual, semiautomatic and automatic welding. It is performed by a non-consumable electrode in inert gases with filler material and covers the aluminum a thickness of 0.8 to 60 mm.
According to regulations presence of welds is shown in the assembly drawings or in the general form. Displaying welds in solid lines, if they are visible. And if on the contrary - the dashed line segments. From these lines are removed callouts with one-sided arrow. Symbol of welds performed on a shelf by the leader. The inscription is on the shelf, if the seam is on the front side. In the embodiment, reverse designation will be located under the shelf. This includes information about the seam in the following sequence:
- Auxiliary signs. At the intersection of the leader with a shelf icon may be:
┐ - seam welding is done during installation.
- Designation of welds, their structural elements and GOST Connection.
- Name seam standard.
- Welding method according to regulatory standards.
- Leg indicated, this paragraph applies only to the corner joints.
- seam discontinuity, if any. This specifies the location of the step and the welding segments.
- Additional icons auxiliary values. Consider them as a separate item.
These signs are also applied on top of the shelf, if the welding seam visible in the drawing, and under it, when the invisible:
- 9shy; 9shy; Removing the weld reinforcement;
- surface treatment and which provide a smooth transition to the base metal, eliminating sagging and unevenness;
- the seam is performed on an open line; This mark applies only to visible in the drawing welding seams;
- surface finish weld.
To simplify, if all construction joints are made by one guest, have the same cutting edge design and dimensions, marking and welding standards specified in the specifications. The structures may be all, but a large number of identical seams. Then they split into groups and assign serial numbers to each group separately. At one point the seam full designation. On the other put only a serial number. The number of groups and the number of stitches in each of them should be specified in the standard documentation.
Varieties and technology of welding seams - ceiling, horizontal, vertical
Weld - line of the molten metal at the edges of two mating structures, resulting from exposure to an electric arc steel. The type and configuration of the seams is selected individually for each case, its choice will depend upon such factors as the capacity of the equipment used, the thickness and chemical composition of the welded alloys. Such a seam welding also occurs when a soldering iron polypropylene tubes.
This article describes the types of welds and technology implementation. We will study the vertical, horizontal and ceiling joints, as well as learn how to perform their cleaning and inspection of defects on the subject.
1 Classification of welds
Classification of joints on the varieties performed on many factors, chief among which is the type of connection. Under this option the seams are divided into:
Let us consider each of the options presented in detail.
This connection method is applied when welding the end portions of pipes, square profile and sheet metal. Connecting parts are arranged so as to leave a gap of 1.5-2 mm (desired fixation clamps details) between their edges. When working with sheet metal, the thickness of which does not exceed 4 mm, the seam is laid only on one side, in sheets 4-12 mm it can be a double, single still, at a thickness of 12 mm - only double.
Methods for cutting seams
If the thickness of the wall parts is 4-12 mm, necessary mechanical trimming edges and sealing the edges of one of the following methods. Compound particularly thick metal (12 mm) recommended performed using an X-shaped stripping, other embodiments there are disadvantageous because of the need for large quantities of metal to fill the seam, which increases the flow electrodes.
However, in some cases it may be decided welder cooking thick metal one seam, which requires filling it in multiple passes. Seams such a configuration called multilayered, multilayer seam welding technology is shown in the image.
Overlap joints used exclusively for welding sheet metal 4.8 mm thick, the plate boil on both sides, which excludes the possibility of ingress of moisture between the sheets and their subsequent corrosion.
performing such a seam is extremely demanding technology to observe the correct angle of inclination of the electrode that should vary in the range of 15-40 degrees. In case of abnormal filling seam metal will be displaced from the joint line, thereby greatly reducing the strength of the connection.
T-connection is made in the form of letter "T9raquo ;, it can be executed with two, or with one hand. Number of seams and the need for cutting the end of the part depends on its thickness:
- to 4 mm - single seam without cutting the ends;
- 4-8 mm - double, without cutting;
- 4-12 mm - with single sided bunching;
- more than 12 mm - double-sided, double cutting.
One variety of tee connections corner seam is used to join two perpendicular or inclined to one another metal sheets.
2 Types of seams on the spatial position
In addition to the classification by type of connection, the stitches are divided into varieties, depending on the position in the space, according to which they are:
Vertical seam bottom-up
The problem is the implementation of vertical seams slipping down of the molten metal, which is due to gravity. Here it is necessary to use a short arc - to keep the end of the electrode as close to the metal. Welding vertical joints requires the implementation of preliminary work - stripping and cutting, which are chosen based on the type and thickness of the metal compound. After preparing items fixed in the desired position and cross-connection is made rough "prihvatami9raquo ;, which prevent displacement of the workpieces.
Vertical seam welding can be performed from the top-down or bottom-up, in terms of convenience of the latter variant being preferred. The electrode must be held perpendicular to the connecting member, allowed it to prop up the welded edge of the crater. Movement of the electrode is selected based on the desired thickness of the seam, the most durable joint is achieved with the transverse displacement of the electrode from side to side and loop oscillation.
On the vertical plane of the horizontal-type joints are displayed from left to right or right to left. Welding horizontal seams complicated runoff down the bath, which requires maintaining a large angle of inclination of the electrode - from 80 to 90 0. To prevent inflow of the metal at such positions to be moved without transverse oscillations of the electrode, a method of narrow rolls.
The speed of movement of the electrode is selected so that the arc center held by the upper boundary of the seam and the lower contour of the molten bath did not reach the top end of the previous roll. Particular attention here should be given to the top edge, the most prone to the formation of various defects. To weld the last roller it is necessary to clean the seam formed by the slag and soot.
The most difficult in the performance are ceiling joints. Since in such a spatial position of the molten bath is held solely by surface tension of a metal suture itself must make as narrow as possible. Standard roller width - not more than twice the width of the electrodes used, while the electrodes must be applied to 4 mm diameter.
When routing weld electrode must be held at an angle of 90 to 130 0 to mating planes. Roller electrode formed vibrational movements from edge to edge, wherein in an extreme position of the electrode side delayed, thus avoiding undercuts. Note that welders without experience is not recommended to take on the ceiling joints.
2.1 Welding Technology ceiling joints (video)
2.2 Cleaning and inspection of defects
After forming a seam on the surface is connected parts slag, droplets of molten steel and slag, with the suture itself may have a convex shape and protrude above the plane of the metal. Repair data defects allows cleaning, which is carried out in stages.
Initially, by hammer and chisel you need to remove scale and slag, hereinafter via grinder, equipped with an abrasive disk or sanding machine, aligned joint plane. Grain size of the abrasive wheel is selected based on the required surface smoothness.
Defects weld common inexperienced specialists usually result from uneven or electrode movement and force properly selected current value. Some defects are critical, some can be corrected - in any case, the weld monitoring for their presence is a must.
Consider what the defects are and how to perform their checks:
- Fusions - insufficient filling of the molten metal interface significantly reduces the bond strength. The reasons: a low current, an excessive speed of the electrode. After adjusting the current and reduce the arc length of the defect is eliminated.
They can also form defects such as cracks that appear on the metal cooling step. Cracks come in two configurations - either along a direction transverse to the seam. Depending on the time of formation of cracks classified into hot and cold, the latter appears after solidification interface due to excessive loads that particular weld type can not withstand.
Cold crack is a critical defect, which can lead to complete destruction of the compound. In the case of education it is necessary to re-weld the damaged areas if they are too much - the seam should be cut and re-do.
Types of welds and seams
Welding is one of the main ways to connect, which is used in industry and in the private sphere. This is a relatively cheap and reliable method that provides a permanent connection. Given that there are a plurality of metal species, each of which has the features of sealing, as well as various working conditions and requirements themselves to a compound allocated various types of welded joints and seams.
Alloying Area - takes from 0.1 to 0.4 mm of the base metal. It contains partly fused grain. When the metal is in the warming zone, it becomes acicular structure. It has low strength and high friability.
The zone of thermal influence - it is divided into four sections. The first section applies to the base metal, which is heated up to a temperature above 1100 degrees celsius. It has a coarse structure. Grain in the field, about 12 times larger than the standard. Because overheating decreases toughness, ductility and other mechanical properties of the metal. This is the weakest portion of welding, which often occurs in the gap.
Second portion - a normalizing zone where the base metal is warmed to 900 degrees Celsius. grain structure is much finer than in the previous case. This takes a lot of 1 to 4 mm.
The third portion - the zone of incomplete crystallization. Here, the base metal is warmed from 750 to 900 degrees Celsius. He found both small and large grains. Due to the uneven distribution of the mechanical properties of the crystals are reduced.
The fourth portion - zone recrystallization. FIELD warmed from 450 to 750 degrees Celsius. There is recovering form grains that have been deformed by past impacts. Est width of this portion is 5 to 7 mm.
The zone of the base metal - starts from the portion which warms less than 450 degrees Celsius. Here the structure is similar to the base metal, but due to the heating of the steel loses its properties fortress. Along the boundary are allocated nitrides and oxides that impair communication grains. Metal acquires greater strength at this location, but obtains a lower toughness and ductility.
Full classification of welds and joints
Types of welds are divided into several categories according to various criteria. One of them is the difference in appearance. Here distinguished:
- The concave (they loose);
- Convex (they are also reinforced);
- Normal (they are flat).
According to the type of performance found:
According to the number of passes:
According to the number of layers:
- Multilayer (welding thick metal);
Classification of welds allocates more varieties of length:
- Spot welds (create them by means of resistance welding);
- Bilateral chess;
- Bilateral chain;
- Unilateral intermittent;
- Unilateral continuous.
Types of welds in the direction of the force applied:
- Frontal (transversal) - is carried out perpendicular force;
- Wing (longitudinal) - the force is parallel to the seam;
- Squint - the effort is carried out at an angle;
- Combined - it combines the flank and frontal species.
Types of welding seams and joints on the spatial location:
On the functions and purpose of welds categories are:
- Broadened - made by transverse oscillating movements of the electrode;
- Thread - joint width which practically does not exceed the diameter of the welding electrode.
This is the most common variant, which is a compound of ordinary sheets or end surfaces. It requires a minimum amount of the metal and time. It can be carried out without the bevel edges if thin sheets. For thick products requires preparation of metal for welding, where the bevel edge is required to increase the depth provarkoy. This is true in a thickness of 8 mm and above. If the item is thicker than 12 mm, there must be a bilateral butt joint with beveling. Such compounds are often held in a horizontal position.
"T" T-bar variety of connections and joints are represented as letters. It may be one- or two-sided, and also can combine articles of different thicknesses. If less perpendicularly mounted item, the electrode during welding must be tilted to 60 degrees. You can also use oven gloves to tilt the piece and make a more simple version of Welding "in the boat." This reduces the probability of formation of undercuts. The seam is usually applied in one pass. Now there are many devices for automatic welding of the HQ.
Angular considered compound, which is at an angle of 90 degrees or other values. Such connections often give way edge to the seam was able to lie down to the desired depth to ensure reliability. Bilateral provarkoy makes the connection stronger.
This method is used for welding the sheet thickness less than 1 centimeter. They are placed overlapping each other and boil on both sides. It is necessary to ensure that between them from getting wet. Sometimes, for a better bond, the compound is brewed from the end.
The geometry of the weld
The types of welds and methods of applying them, you should pay attention to the basic geometrical parameters.
- E - the width of the formed weld;
- S - the thickness of the workpiece;
- B - the gap between the welded workpieces;
- T - seam thickness is obtained;
- H - depth-welded portion;
- Q - the size of the convex portion.
- A - the thickness of the fillet weld, which. Beginning convexity value and the calculated heights;
- P - estimated altitude which corresponds to a perpendicular line drawn from the deepest place about the hypotenuse to the melting of large direct triangle inscribed in the outer portion of the seam;
- Q - convexity build-up area;
- K - a fillet weld leg is the distance from the surface of one workpiece to another angle boundaries.
All kinds of welded joints and seams differ markedly in their properties. Therefore, for each specific case it is necessary to select a set of parameters for a successful combination. First, we should pay attention to the spatial position. The more easily passes the work, the better the weld quality. The most user-friendly design are considered horizontal joints, therefore, the master trying to put the workpiece in such a position. Sometimes even have to flip several times the same product, to provide a high quality weld. "Important! It should not be forgotten that the welding of one pass helps to achieve a better fortress than multiple passes. Therefore, it is necessary to find a balance between convenience and number of passes. "
When thick billets always have to carve the edges and then further process the surface to add to her purity. Splice variants are the most simple and preferable for use, since they are easier to fix to avoid distortion geometry items received. In addition to the correct choice of type of joint, it is necessary to pay attention also to the temperature, because then they can move provarkoy zone and the product simply remelting or undercooked.
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