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 varieties of metal, each of which requires an individual approach. This process includes several stages that the raw materials must pass through before they go to the weld.
A number of actions to be performed to prepare the metal for welding:
- editing
- cleaning;
- markup;
- cutting;
- installation and tack.
We bend and rule metal correctly: the subtleties of technology
The preparation rules include the elimination of any irregularities, curvature or other defects on the surface through dressing. The peculiarity of the procedure lies in the pressure exerted on the material produced by means of a press or manually (hammer blows).
Interestingly, both ferrous and non-ferrous metals undergo editing.
Methods
So what are the differences between manual and machine editing?
When a hand-made product (part) is placed on a steel or cast iron leveling plate / anvil and hammering is carried out.
By machining metals mechanically , it is possible to obtain perfectly correct objects on special machines and workbenches.
Editing metal can be both cold and hot.
To the initial stage of preparation of metal for welding include bending of the material. This type of work belongs to metalwork. During the procedure, the workpiece is bent, following a given angle and radius, until it reaches the desired shape.
For manual bending, a machine and a press are used. They produce it by eye, according to markings, patterns, samples.
Compliance with the technological sequence of the preparation of metal for welding will result in welds that are distinguished by strength and reliability.
Important! To avoid possible defects, metal products are thoroughly cleaned from traces of grease and rust.
How to clean material from grease and rust?
In contact with air, the metal enters into a chemical reaction with oxygen, forming oxides. As a result of this, rust is formed, other contaminants are formed, which lead to the formation of diverse weld seam defects.
Important! Make sure that in the process of processing the metal on its surface does not get oil, scale, moisture. This is highly undesirable.
Two cleaning methods are distinguished, which are carried out at the stage of preparing the metal for welding:
1. Mechanical. When cleaning the surface in this way, use special cleaning machines or sandpaper. If you need 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 more durable weld in the welding process.
2. Chemical. The metal surface is cleaned by dipping it in a special chemical solution.
Marking of metal parts
The initial stage of work with the material is the preparation of the metal surface for welding. After that, they begin to markup. Carrying out the outline, the contours of the parts with marks are outlined on a sheet of metal. The bend points, hole centers and other subtleties of future structural elements are shown here. Having coped with such work, they proceed to cutting or cutting metal - the stage at which it is necessary to be extremely careful and accurate. Even the slightest error can lead to the rejection of finished products.
When the marking lines have already been drawn, work continues with the use of a punch - a special machine that makes small indentations on the surface of the sheet. So traces of basting will be saved in the course of further processing of the material.
Important! When marking stainless steel parts, experts recommend using a punch.
As a result of the preparation of metal for welding with the implementation of locksmith operations, the configuration of future structural parts 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, marking is to the industrial production of parts. To produce a batch of identical parts, a specially prepared template is used for marking, which is made of plywood or a thin sheet of metal. The procedure for applying the patterns when marking was called basting.
Chopping or cutting metal sheets before welding
When preparing and assembling the metal for welding, first remove the surface layer of the metal - the bevel. To do this, use an edge trimming machine or a special gas cutting machine. Sometimes cutting is done with one's own hand, using a manual or pneumatic chisel.
The edge lines, along which metal will be cut in the future, are laid with the help of a nickel marker, they look like two parallel lines. The upper edge of the chamfer is determined by the inner one, the outer one passes in the lower part of the chamfer. If risks were not previously applied, then the master uses a ruler when cutting.
In order not to make a mistake during the procedure, be very attentive to the work and watch the force of pressing the tool during the line.
When chamfering, the edges of the sheets are firmly fixed. Those sheets that are not in place are chipped directly on the shelf or after being placed on the floor, but even then the material is firmly clamped so that the sheets do not move during the impact.
The subtleties 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 you want to get a straight cut, and metal sheets do not exceed 20 mm in thickness.
In production conditions, a special farm is installed - guillotine scissors with a knife length of 1-3 m or press knives with blades up to 70 cm in length.
Sheets with a thickness of less than 6 mm are cut in straight or curved lines with roller scissors by means of gas-oxygen or plasma-arc cutting. This technique of separation of parts is acceptable for working with alloy steel and non-ferrous metals. In relation to them, gas flux cutting can be used, and cold cutting of the rods, regardless of diameter, is carried out using round gear or friction saws.
Tack before welding metal
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 application of the methodology of the most effective way of fixing the placed parts in relation to each other.
Welding tack - short weld.
Features of the application of technology
Using a tack allows you to:
- avoid displacement of welded structural elements during welding;
- Avoid reducing constipation in relation to other parts;
- to achieve increased rigidity;
- reduce the percentage of deformation of parts.
Parts pre-assembled into a single design are seized by spot welding. For this, stationary welding machines and special clamps are used. The use of clothespins makes it possible to achieve high accuracy during the preliminary assembly of a system consisting of several elements. It is good that this method allows you to adjust the distance “between” or the position of the parts before preparing the metal for welding and assembling the structure. The procedure is carried out manually or using automated systems.
Important! Manual processing is based on the sketches made before assembly, in the places of which tacks will be made in the future.
The reliability and ease of use of the future product depend on how correctly tacking is performed.
Tack Requirements
The quality of the tack depends on several factors. When performing metal work, pay attention to such details:
- Electrodes: their brand must match the brand of material used to weld the parts. So, if in the future it is planned to carry out welding work semi-automatically using wire, then the electrodes should correspond to it.
- Tack length should not exceed 20 mm. Its thickness is ideally 2 times less than the future welding seam.
- Watch how metal preparation for welding is carried out. The choice of manual arc welding in this case depends on the technical parameters of the design. Welded current in this process is also of no small importance. Its value should be selected correctly, taking into account the strength and voltage indicators 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 places for tacking are firmly boiled.
- Keep track of tack placements. They should not be done anywhere, but at the supposed points of greatest structural stress after assembly, as well as in places of possible deformation.
- In no case place the tack at the intersection (intersection) of the welds.
Some rules for doing tack
Performing work using automatic welding, tacks are placed in relation to the first pass from the opposite side. There are times when, due to technical characteristics, you have to place them on the side of the first pass. When performing such an operation, it is important to observe the number of tacks in order not to overdo it.
Before starting welding work, pay attention to the appearance of the tacks made at the previous stage. They also need to be prepared for final welding: clean from toxins and metal splashes caught, clean up - make the tack point smooth and almost even.
Working with metal is a laborious and energy-intensive process. Pursuing work related to the manufacture of steel metal structures, you will have to work hard. In order to achieve effectiveness in the manufacture of metal parts, structural elements must not only be welded together in a single unit, but also preliminarily prepared, as you already understood by reading the article.