The correctness and thoroughness of the preparation of metal for welding determines the quality of the joints of two or more metal products during it. There are several types of metal, each of which requires an individual approach. This process includes several stages that the raw material must go through before being sent for welding.
A series of actions to be performed to prepare the metal for welding:
- edit;
- cleaning;
- markup;
- cutting;
- installation and tack.
Burn and rule the metal correctly: the subtleties of technology
Preparation rules include the removal of any unevenness, curvature or other defects on the surface by editing. The peculiarity of the procedure lies in the pressure exerted on the material, produced using a press or manually (hammer blows).
Interestingly, both ferrous and non-ferrous metals are edited.
Methods
So what's the difference between hand and machine straightening?
When handmade, the product (detail) is placed on a steel or cast iron straightening plate / anvil and hit with a hammer.
Mechanically working metals, it is possible to obtain perfectly correct items on special machines and workbenches.
Metal dressing can be either cold or hot.
The initial stage of preparing metal for welding also includes bending the material. This type of work belongs to locksmith. During the procedure, the workpiece is bent, following the specified angle and radius, until it reaches the desired shape.
When manually bending, a machine and a press are used. They make it by eye, according to markings, patterns, samples.
Compliance with the technological sequence of metal preparation for welding will result in welds that are durable and reliable.
Important! To avoid possible defects, metal products are thoroughly cleaned from traces of grease and rust.
How to clean the material from grease and rust?
When in contact with air, the metal reacts chemically with oxygen, forming oxides. As a result, rust is formed, other impurities are formed, which lead to the formation of various defects in the welding seam.
Important! Make sure that during the processing of metal, nooil, scale, moisture. This is highly undesirable.
There are two cleaning methods that are carried out at the stage of preparing the metal for welding:
1. Mechanical. Cleaning the surface in this way, use special cleaning machines or sandpaper. If it is required to achieve a rough surface, then the metal is subjected to hydroabrasive treatment, by means of which a microrelief is created on the surface, which contributes to the formation of an even stronger seam during welding.
2. Chemical. The surface of the metal is cleaned by dipping it in a special chemical solution.
Marking metal parts
The initial stage of work with the material is the preparation of the metal surface for welding. After that, proceed to the markup. When basting, the contours of parts with marks are outlined on a sheet of metal. Here they show the places of folds, the centers of holes and other subtleties of future structural elements. Having coped with such work, they proceed to chopping or cutting metal - a stage at which it is necessary to be extremely careful and accurate. Even the slightest error can lead to defective finished products.
When the marking lines have already been drawn, work continues with the use of a center punch - a special machine that makes small indentations on the surface of the sheet. So traces of basting will be preserved in the process of further processing of the material.
Important! Performing markupstainless steel parts, experts recommend using a center punch.
As a result of the preparation of metal for welding with the performance of locksmith operations, the configuration of future structural details is determined. When marking or basting, the surface of the metal sheet is pre-primed. "What is the difference between these concepts?" - you ask. Marking is directly related to individual production, basting - to the industrial production of parts. To produce a batch of identical parts, a specially prepared template is used for marking, which is made from plywood or a thin sheet of metal. The procedure for applying the pattern during markup is called basting.
Cutting or cutting metal sheets before welding
When preparing and assembling metal for welding, first remove the surface layer of the metal - a chamfer. To do this, use an edge-cutting machine or a special gas-cutting machine. Sometimes the felling is done by hand, using a manual or pneumatic chisel.
The lines of the edges along which the metal will be cut in the future are laid using a nickel marker, they look like two parallel lines. The upper edge of the chamfer is determined along the inner edge, the outer one passes in the lower part of the chamfer. If the risks were not previously applied, then the master uses a ruler when chopping.
In order not to make mistakes during the procedure, treat your work with great attention and watch the force of pressing the tool while drawing the line.
When chamfering, the edges of the sheets are securely fastened. Those sheets that are not in place are trimmed directly on the rack or after being placed on the floor, but even then the material is firmly clamped so that the sheets do not move during impact.
Details of metal cutting
This mechanical operation is carried out when there is a need to obtain a straight cut. Basically, the procedure is carried out using scissors if a straight cut is required, and metal sheets do not exceed 20 mm in thickness.
In the conditions of production, a special farm is installed - guillotine shears with a knife length of 1-3 m or press knives with blades up to 70 cm in length.
Sheets less than 6 mm thick are cut along straight or curved lines with roller shears by oxy-fuel or plasma-arc cutting. This technique for separating parts is acceptable for working with both alloyed steel and non-ferrous metals. Flux cutting can be used for them, and cold cutting of rods, regardless of diameter, is carried out using round toothed or friction saws.
Tack before metal welding
Tacking is the last of the stages, which involves preparing the metal for welding. The requirements and features of working with metal products require the use of the most effective method of fixing the placed parts in relation to each other.
Welding tack - short weld.
Features of the use of technology
Using an oven mitt allows you to:
- avoid displacement of welded structural elements during welding;
- avoid reducing constipation in relation to other parts;
- achieve an increase in structural rigidity;
- reduce the percentage of deformation of parts.
Parts pre-assembled into a single structure are tacked by spot welding. For this, stationary welding machines and special clamps are used. The use of clothespins makes it possible to achieve high precision in the pre-assembly of a system consisting of several elements. It is good that this method allows you to correct the distance "between" or the position of the parts before preparing the metal for welding and assembling the structure. Carry out the procedure manually or using automated systems.
Important! Manual processing is based on basting made before assembly, in places where tacks will be made in the future.
The reliability and ease of use of the future product depends on how correctly the tacks are made.
Requirements for tacks
The quality of tacks depends on several factors. When working on metal, pay attention to the following details:
- Electrodes: their brand must match the brand of the material used to weld the parts. So, if in the futureit is planned to carry out semi-automatic welding using wire, then the electrodes must correspond to it.
- The length of the tack should not exceed 20 mm. Its thickness is ideally 2 times less than the future welding seam.
- Watch how the metal is being prepared for welding. The choice of manual arc welding mode in this case depends on the technical indicators of the design. The welding current in this process is also of no small importance. Its value should be selected correctly, taking into account the indicators of the strength and voltage of the current used in further welding of the structure. For reliability, the current is chosen 20% more than the one that will be used in the future.
- The tacks are firmly welded.
- Watch out for potholder placements. They should not be done anywhere, but at the expected points of greatest stress of the structure after assembly, as well as in places of possible deformation.
- Never place the tack at the intersections (crossings) of the welds.
Some rules for making tacks
When working with automatic welding, tacks are placed in relation to the first pass on the opposite side. There are cases when, due to technical characteristics, it is necessary to place them on the side of the first passage. When doing this operation, it is important to observe the number of tacks so as not to overdo it.
Before you start welding, pay attention to the appearance of the tacks made at the previous stage. They are also neededprepare for final welding: clean from slag and caught metal spatter, clean - make the tack spot smooth and almost even.
Working with metal is a labor-intensive and energy-intensive process. Being engaged in work related to the manufacture of steel metal structures, you will have to work hard. In order to achieve efficiency in the manufacture of metal parts, structural elements must not only be welded, combined into one whole, but also pre-prepared, which you already understood after reading the article.
