Those involved in the operation of various mechanisms, sometimes faced with the need to surfacing on the surface of the part in a particular place. Broken fasteners, partially or completely worn during operation of the part, edge, worn sleeve. Each of these cases involves the restoration of the part using the deposition of a new durable metal layer on the worn area. Such processing allows not only to perform restoration, but also to give the details new, more valuable properties. For example, by surfacing using a carbide layer on the basis of a part made of low carbon steel, it is possible to obtain a part with increased wear resistance or other operational properties.
This most simple, but at the same time effective way is suitable not only for restoring the suitability (operability) of metal parts. Using metal welding with an electrode, you can modify the sample, giving it shaped features, strengthen the properties of the surface layer, work on strength and wear resistance.
Features and terminology: the main thing about the concept of “surfacing”
What is the secret of this technology, what features it has and how to implement it in everyday life, we will try to understand together. The reader is hardly interested in industrial technologies, especially with the use of robotic machines. Therefore, we will further examine the features of metal surfacing manually, that is, with the help of electrodes for welding.
In everyday life, under the concept of metal, a person can also mean an alloy, for example, steel. If verbally these names can be generalized, then in the work the use of technologies for a specific metal / alloy and the working details are different.
It is simply unrealistic to consider the topic in detail because of the volume of the proposed material, therefore, when starting to familiarize yourself with such a process, first clarify the details regarding working with metal of the selected type. All that we offer you in the article is recommendations for surfacing.
In general, metal surfacing has similarities with welding; it does not hurt to get acquainted with the latest technologies applied to the processing of alloys and metals: copper, aluminum, cast iron, stainless steel and others in terms of the specifics of the proposed work.
Surfacing refers to the joining of metals of a dissimilar nature by depositing one molten metal on the surface of another. The filler material is the one that is applied, the main one - subjected to surface treatment according to the method of metal deposition.
Technological features of the procedure
The interpenetration of hot metals into each other occurs at the level of molecules.
For this, the surface layer of the base is heated to a degree of melting to a shallow depth, and the additive to a liquid state.
The advantages of metal welding include the ability to control the thickness of the layer and the application of the additive on the sample, regardless of its shape.
The name of the alloy from English comes from the word mixing and is used in terminology as a homogeneous compound. The main characteristics of the alloy include increased reliability, since it is impossible to give the metals separation to the initial state by mechanical action.
Basic rules of surfacing
In the work, the basic rules for metal deposition are distinguished.
The melt depth of the upper layer of the main part should be minimal. This effect can be achieved with an elementary tilt of the electrode, made in the direction opposite to the direction of its movement.
With minimal mixing of metals of a heterogeneous nature, the residual stress is reduced, which eliminates the risk of deformation of parts in individual areas.
During the procedure, monitor the amount of the additive, because its excess can lead to complications in further work, which is accompanied by even greater labor costs and lead times.
Electrode surfacing technology
Before starting work, preliminary metal cleaning is carried out, which consists of two stages: stripping and degreasing.
Electrode surfacing is the most common method for producing a homogeneous layer. The simplicity of the technology makes it the main application both in the production environment and at home.
The electrode with a special coating is selected based on the objectives of the processing. This choice also depends on the type of metal from which the base is smelted. Depending on the brand of electrode, the resulting layer acquires the necessary characteristics.
The circuit connection is direct or reverse. The second option is used more often, as it is convenient. For work, a constant voltage of "+" on the coated electrode is required.
Features of the procedure
The shaped features and layer thickness depend on the cross section of the electrode. To ensure high-quality surfacing, the voltage and current strength of the arc must be minimized, but this requires proper coordination. Practical skills are acquired with experience and in the future do not cause difficulties for the worker.
Surfacing: little secrets
With increasing voltage, the scar begins to increase not in volume but in width, which contributes to an increase in the length of the arc. Each type of electrode has its own characteristics of use. For example, do you know how important it is to pre-heat the base? When working with low-allergenic steel, this condition is not always necessary. In which mode is it best to cool a part? And what current level to set? All technological details of surfacing are marked in the accompanying documentation for the type of electrode you have chosen. As for the quality of surfacing, it increases along with the heating temperature, the value of which is approximately the same for all types of electrodes and amounts to + 300 º. Carrying out work related to surfacing at home, you will have to acquire a thermal furnace, for example, an electric chamber.
Features of plasma surfacing of metal
Durable almost inextricable under any pressure pressure nodes are produced using plasma surfacing. With the help of such processing, each of the products passed through the procedure acquires the necessary dielectric, thermal, physical and other properties. In other words, products are hardened during surfacing. Metal cutting, as well as its processing, is performed using a special torch with a hot plasma stream.
Products made using plasma arc surfacing are characterized by wear resistance, heat resistance, acid resistance, etc.
Compared to surfacing using an electrode, plasma surfacing has several advantages, but can only be used in production conditions. To install a special installation and purchase equipment for working with such units at home is at least an expensive pleasure. Therefore, think again whether there is a need to purchase a tool for rare use at home or is there a place to use a good old electrode, which will be more financially beneficial, but not the worst option.
Surfacing seams and their types
To get a high-quality coating of the main part with another alloy, start laying the next scar on the opposite side of the product. In this case, the surfacing layers are not superimposed sequentially (one after the other), but arbitrarily - then in one, then in another section. The use of such a metal surfacing technology will help to avoid partial deformation of the substrate during overheating.
Depending on the technology and purpose, surfacing seams are divided into several categories.
Depending on the type of workpiece, use one of the scar patterns:
- a helix formed from rollers of a homogeneous alloy;
- a series of closed circles created from deposited scars;
- metal strokes located along the generatrix.
The first of the methods is most often used when carrying out work in the conditions of mechanized production. Therefore, we will not delve into this process. We will familiarize ourselves with other methods of processing flat and volumetric parts in more detail, having studied their specificity and scope.
Seams for flat surfaces
When processing planes, one of the technologies for applying a homogeneous layer is used: narrow or wide scars, a continuous layer. Let's get acquainted with these types of metal surfacing.
Narrow hatching
The method of application is narrow scars. They are laid with an overlap of about 1/3 of the entire seam length.
Wide roller application
The processing technique with wide rollers consists in smooth perpendicular movement of the electrode relative to the axis of the weld. In this case, oscillatory movements are performed, the configuration of which is selected based on the volumes of the main part.
Combined surfacing
The use of combined processing is appropriate in cases where it is required to obtain a continuous homogeneous layer. For this, surfacing is done with narrow scars located at a distance slightly less than their width from each other. After applying the first layer, the base is stripped to get rid of slags, and another layer of molten metal is applied to the remaining voids.
For cylindrical surfaces
In addition to the above, they use another popular technology for surfacing using electrodes - in a protected gas environment. The processing principle is not difficult. In fact, it is in another way - the acquisition of a cylinder filled with a special gas mixture: argon, helium, any other, depending on the type of filler material used in the surfacing. This option is best suited for a small home workshop.
Although the purchase of a gas cylinder for working with metals at home is unlikely to be appropriate. With your own hands it is easier to perform surfacing using electrodes as we examined in the article.
I would like to hope that here you will find all the answers to your questions, figured out the concept of the technological process and clarified for yourself how to properly weld at home.