Those who operate various mechanisms are sometimes faced with the need to weld on the surface of a part in a particular place. Broken fasteners, partially or completely worn parts during operation, edge, worn bushing. Each of these cases involves the restoration of the part using the surfacing of a new durable metal layer on the worn area. Such processing allows not only to restore, but also to give the part new, more valuable properties. For example, hardfacing on the base of a mild steel part can result in a part with improved wear resistance or other performance properties.
Such the simplest, but at the same time effective method 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 shape features, enhance the properties of the surface layer, work on strength and wear resistance.
Features and terminology: basic about the concept of "surfacing"
What is the secret of thistechnology, 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 deal with the features of metal surfacing manually, that is, using 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 particular metal / alloy and working parts differ.
Considering the topic in detail is simply unrealistic due to the amount of material offered, therefore, when starting to get acquainted with such a process, first clarify the details regarding working with the metal of the selected type. All that we offer you in the article are 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.
Under the surfacing means the connection of metals of a dissimilar nature by applying one molten metal to the surface of another. The filler material is the one that is applied, the main one is the one subjected to surface treatment according to the metal surfacing method.
Technological features of the procedure
The interpenetration of hot metals into each other occurs at the levelmolecules.
To do this, the main surface layer is heated to the degree of melting to a shallow depth, and the additive to a liquid state.
The advantages of weld overlay welding include the ability to control the thickness of the layer and apply an additive to 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 bring the metals to their original state by mechanical action.
Basic rules for floating
In the work, the basic rules of metal surfacing are distinguished.
The melt depth of the top layer of the main part should be minimal. This effect can be achieved with an elementary tilt of the electrode, done in the direction opposite to the direction of its movement.
With minimal mixing of heterogeneous metals, the residual stress is reduced, which eliminates the risk of deformation of parts in certain areas.
When carrying out the procedure, keep an eye on the amount of the additive, because its excess can lead to complications in further work, which is accompanied by even greater labor costs and deadlines.
Technology of welding with electrodes
Before starting work, a preliminary cleaning of the metal is carried out, which consists of two stages: stripping and degreasing.
Surfacing of metal with an electrode is the most common method for obtaining a homogeneous layer. The simplicity of the technology makes it a staple in both production and home use.
Electrode with a special coating is selected based on the processing goals pursued. This choice also depends on the type of metal from which the base is smelted. Depending on the brand of the electrode, the resulting layer acquires the necessary characteristics.
Connecting the circuit - direct or reverse. The second option is used more often, as it is more convenient. To carry out the work, a constant voltage "+" on the coated electrode is necessary.
Features of the procedure
Shape features and layer thickness depend on the cross section of the electrode. To ensure high-quality welding, arc voltage and current must be minimized, but this requires correct coordination. Practical skills are acquired with experience and do not cause difficulties for the worker in the future.
Surfacing: little secrets
When the voltage increases, 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 preheat the base? When working with low-allergenic steel, this condition is not always necessary. In which mode is it best to cool the part? And what level of current to set? All technological details of surfacing are noted in the accompanying documentation for the type you have chosen.electrodes. As for the quality of surfacing, it increases along with the heating temperature, the value of which for all types of electrodes is approximately the same and amounts to + 300 ºС. When carrying out work related to surfacing at home, you will have to acquire a thermal furnace, for example, an electric chamber furnace.
Features of plasma metal surfacing
Strong, almost inseparable units under any pressure force are produced using plasma surfacing. With the help of such processing, each of the products that have passed the procedure acquires the necessary dielectric, thermal, physical and other properties. In other words, the products are hardened during the surfacing process. Metal cutting, as well as its processing, is performed using a special cutter with a hot plasma flow.
Plasma arc cladding products are wear-resistant, heat-resistant, acid-resistant, etc.
Compared to welding with an electrode, plasma welding has a number of advantages, but can only be used in production conditions. Mounting a special installation and purchasing 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 there is a place to use the good old electrode, which will turn out to be more profitable financially, but by no means the worst option.
Field welds and their types
To get qualitycoating the main part with another alloy, start laying the next scar from the opposite side of the product. In this case, the layers of surfacing are not superimposed sequentially (one after the other), but arbitrarily - first in one, then in another area. The use of this technology of metal surfacing will help to avoid partial deformation of the base during overheating.
Field welds are divided into several categories depending on technology and purpose.
Depending on the type of workpiece, one of the scar layouts is used:
- helix formed from homogeneous alloy beads;
- a series of closed-type circles created from built-up scars;
- metal strokes along the generatrix.
The first of the methods is most often used when working in mechanized production. Therefore, we will not delve into this process. We will get acquainted with the rest of the methods of processing flat and three-dimensional parts in more detail, having studied their specifics 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
Method of application - narrow scars. They are laid with an overlap of about 1/3 of the entire length of the seam.
Applying wide rollers
The method of processing with the help of wide rollers consists in a smooth perpendicular movement of the electrode relative to the axis of the deposit. Whereinperform oscillatory movements, the configuration of which is selected based on the volume of the main part.
Combined hardfacing
The use of combined processing is appropriate in cases where it is required to obtain a continuous homogeneous layer. To do this, the surfacing is carried out with narrow scars, located at a distance slightly less than their width from each other. After applying the first layer, the base is cleaned, getting rid of slags, and another layer of molten metal is applied to the remaining voids.
For cylindrical surfaces
In addition to those listed above, another popular surfacing technology is used when using electrodes - in a protected gas environment. The principle of processing is not complicated. In fact, it is different - the acquisition of a cylinder filled with a special gas mixture: argon, helium, any other, depending on the type of filler material used in surfacing. This option is best suited for a small home workshop.
Although buying 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 discussed in the article.
I would like to hope that here you have found all the answers to your questions, figured out the concept of the technological process and clarified for yourself how to properly carry out surfacing at home.
