High-tech modern welding is carried out in accordance with generally accepted quality criteria. The final product of the work is welding seams, the types and designations of which are classified, described and divided by quality and implementation methods.
What is a weld
The terms "weld" and "weld" often mean the same thing, but some sources share both formulations.
According to the simplest designation, the weld is an integral connection of parts by welding.
A more complex definition is associated with the physics of the process: the weld is a section of crystallized or deformed substance that combines several parts. Welding joints and seams, one way or another, are perceived as one and the same definition.
Classification
Types and designations of welds are determined by their characteristics. The classification of joints is based on the spectrum of their application. According to the external parameter, the seams are divided into:
- Convex, with reinforcement.
- Concave, with relaxed construction.
- Flat.
Depending on the type of execution, the seams are divided into one-sided and two-sided, according to the number of passes by the electrode - into single-pass and double-pass. Single-layer and double-layer methods of penetration are also distinguished.
According to the length of the seams are classified into:
- One-sided solid.
- One-sided intermittent.
- Point. Characteristic for a contact electric cooker.
- Bilateral chain.
- Bilateral checkerboard pattern.
By spatial arrangement they are divided into:
- Lower horizontal.
- Ceiling vertical.
- To the boat.
- Semi-ceilinged.
- Semi-horizontal.
- Semi-vertical.
According to the vector of force, they are classified into:
- Flank, or longitudinal. The force is applied in parallel to the penetration.
- Transverse. The force is applied perpendicularly.
- Combined. Combines all varieties.
- Squint. The interaction is carried out at an angle.
The designation of welds according to GOST, depending on the functions and purpose, is divided into durable, sealed and durable. In terms of width, a filament seam is distinguished, the value of which does not exceed the diameter of the electrode rod, and the broadened one, which is performed by vibrations in the transverse direction during welding.
According to GOST, a strict designation of the types of welds and joints is described. Information about the type of mount and how it is performed is reflected in the special icons used in the preparation of the drawings.
Types of welds
The type of weld used depends on the materials, their thickness and design features. Understanding the specifics of welding parts and avoiding defective work is possible only with the appropriate theoretical training. The reason for the weak mechanical resistance of the joints in most cases is the insufficient penetration of the joints. Proper weld quality and strength are achieved by choosing the right types and modes of welding. The training of welders includes not only the practical, but also the theoretical part - the study of the norms and rules, symbols of welds, features of the equipment used. Knowing the basic principles of using these or other fixtures and welding allows you to get a durable and strong connection.
Butt seams
Type of welding joints, most often used on pipes, sheet structures and end sections. It is formed with minimal expenditure of time, effort and materials. Such butt fasteners are characterized by their own characteristics: thin sheets of metal are welded without bevel edges.
Joints of products with a greater thickness require pre-treatment, which consists in beveling for a greater depth of boiling. Such preliminary preparation is carried out for metal products whose thickness is in the range of 8-12 millimeters. Thicker metals combine double-sided welding with bevelled edges. Butt joints are most often performed in a horizontal plane.
T-joints
Designation of T-type welds is made in the form of the letter "T". The width of the weld depends on the thickness of the objects to be joined, the features of bonding affect how the connection will be - one-sided or two-sided.
The electrode is held at an angle of 60 degrees when working with metal parts of different thicknesses. The welding process is simplified if tacking is used or the "boat" method - it reduces the number of undercuts. T-seam is applied in one pass. For this type, automatic electric welding machines are widely used.
Lap seams
Seams used for welding sheet metals up to 12 millimeters thick. The materials to be joined are overlapped and boiled on both sides along the joints. The inside of the structure to be welded must be insulated from moisture. Additional perimeter welding is carried out in order to strengthen the bond.
The formation of the joint by means of an overlap seam is carried out between the surface of one product and the end face of another. This welding method significantly increases the consumption of materials, which is taken into account in advance. Before starting work, the metal sheets are aligned and carefully pressed against each other.
Corner
Designation of welds made at a certain angle to each other. A characteristic feature is the provision of better penetration through the use of preliminary bevels. This not only increases the depth of the weld, but also increases the reliability of the entire structure. Strength is enhanced, including through bilateral welding of metal products without gaps in the edges. Such electric welds are characterized by a large amount of deposited metal.
Ceiling seams
One of the most difficult to perform electric welding operations due to the location of the seam above the welder. It is created by the minimum electric current strength by an intermittent welding seam. The designation of ceiling and vertical joints in the instructions contains warnings about the complexity of the work and the need for the welder to have certain skills to achieve maximum quality. Ceiling joints are resorted to in conditions where it is not possible to displace the welded structures: work with pipes, ceiling channels and beams at construction sites, all kinds of metal structures. The specifics and nuances of performing ceiling joints are mastered only in practice.
Cleaning seams
Welded seams after finishing work have an uneven texture, protruding above the surface and leaving behind a drop of metal, traces of slag and scale. All this is removed, and the process itself is called the cleaning of the seams.
It is carried out in several stages:
- With a chisel or hammer, the scale gets off.
- The site with a seam is processed by a grinder.
- Sometimes tinning is carried out - a thin layer of molten tin is applied.
Marriage and possible defects
The most common in welders' work is a curved seam with uneven filling. A similar defect is possible due to uneven electrode guidance. It is eliminated only with a set of welder experience.
The second most frequent defect is the wrong choice of arc length or current strength, which leads to the appearance of uneven filling or “undercuts”. Depending on the type of defect, either the aesthetics of the joints or their strength may suffer.
Lack of fusion
Under the lack of fusion in the rules for the designation of welds and other instructions, we understand the insufficient filling of the joint of parts with metal. Appears in the following cases:
- Lack of or poor quality material edge treatment.
- Low amperage.
- Electrode speed too high.
Undercut and burn
Undercut is an unnecessary groove along the seam. The defect arises from a long arc. It is prevented by shortening the arc length or by setting a greater current strength.
Burn through - a hole in the seam - occurs for several reasons:
- Large gap between the edges of the metal.
- High amperage.
- Slow motion of the electrode.
Inflows and pores - small holes that appear in large numbers and adversely affect the strength of the finished seam. There may be several reasons for their appearance:
- Traces of rust and dirt on the metal.
- Contact with molten metal oxygen during work on a draft.
- Low quality metal edge processing.
- Low-quality electrodes.
- Application of filler wire.
In violation of the integrity of the seams cracks occur. They occur after cooling of the molten metal and portend the destruction of the compound. You can save the situation only by digesting the seam or by completely removing it with the subsequent imposition of a new one.
Cooking tips for different types of compounds
It is not difficult to learn how to apply high-quality and durable welds on your own: for this purpose, a large amount of professional literature is offered, which not only gives tips on cooking, but also the ratio of Russian and international designations of welding seams with other nuances. Each type of seam has its own subtleties that must be mastered.
Beginners are advised to start work with electric arc welding and competent preparation of the necessary tools.
The following equipment is being prepared for electric arc welding:
- Devices for welding.
- Electrodes of the correct diameter.
- Hammer or chisel to clean the seams.
- Metal brush for cleaning the welded area.
- Special light filter and mask.
Special and at the same time simple requirements are imposed on the welder’s clothes: it must be tight, always with gloves and long sleeves. When working with old welding equipment, it is advisable to use a rectifier and a transformer.