One of the main conditions for obtaining a high-quality and correct welding seam are quality, properly selected electrodes for welding with an inverter apparatus.
The modern market has a very large range for electric welding. All of them differ in type, coating material and other characteristics. Below we suggest that you familiarize yourself with the available options and choose the most suitable one.
Content
Types of welding electrodes for inverter
All existing electrodes for electric welding are divided into melting and non-melting. At the heart of the melting electrode is a wire rod made of metal wire, covered with a special coating on the outside. Thanks to the coating, the welding arc can stably burn, and the coating also provides good protection of the seam from gas and slag.
Electrodes, the purpose of which is to weld steels of an undefined composition, as well as copper, stainless steel, cast iron and other metals, are made from a certain alloy. Non-consumable types of electrodes are used most often when working with argon welding.
Working welding elements are available in different lengths and diameters. The length of the electrode depends on the features of alloying the wire rod of the product, and can be from 30 to 45 centimeters.
Regardless of the diameter, all types of electrodes are widely used. The only exception is the diameter of 1.6 mm. This type of electrodes is only available on request. Russian welders are practically not used.
The most commonly used classification of all existing electrodes is their intended use. Based on this parameter, the electrodes are divided into:
• Designed to work with carbon and low alloy steels.
• For working with high-strength heat-resistant steels.
• "Electrodes for stainless steel" - for working with high-alloy steel.
• "Electrodes for aluminum".
• Electrodes for welding copper parts and products based on it.
• Electrodes for cast iron.
• For repair and surfacing.
• For welding operations on metals whose composition is not defined.
A classification by type of coating of electrodes is also quite often used. There are four main types of coatings, but only two are widely used.
Electrodes of the basic type.
They received their name because the electrode rod has a so-called main coating. The most popular among the main electrodes is the SSSI 13/55 model. The use of this product makes it possible to obtain high-quality seams having high impact resistance, strength and ductility. In addition, these joints rarely show crystalline cracks, they are poorly prone to "aging". Electrodes SSSI, as a rule, are used for welding works of increased responsibility, and products that will work in harsh conditions. The drawbacks of this type of electrodes include the elongation of the arc, the instability of the coating to moisture and rust, the appearance of scale or oil in the weld region. Together, all this can lead to the appearance of micropores. In addition, the main electrodes can only be operated on reverse direct current.
The second type of electrodes has a rutile coating.
These products are used in welding parts made of metal with a low carbon content. Most often, the brand MR-3 is used. These electrodes are distinguished by good technological qualities, namely:
• The electric arc stably burns both on a constant and alternating current.
• The hot metal is practically not sprayed.
• High quality seams for any position of the parts to be welded.
• Very good separation of slag.
• Electrodes can be used to work on dirty and rusty surfaces.
• Ready weld seams have a very good appearance, without pores and cavities.
• Suitable for welding parts made of steel with low carbon content.
We select the electrode taking into account the material and operating mode
The correct choice of the electrode for operation, of course, plays a big role, however, in addition, it is still necessary to know with what polarity and current it is necessary to work in each specific case. Almost all inverters use direct current. Working with direct current, the electrode part can be connected in several ways, namely:
If the polarity is straight, the electrode is connected to "minus" and the part to "plus".
When working on reverse polarity - on the contrary, the electrode is connected to the "plus", and the workpiece to "minus".
During operation, a higher temperature is produced on the direct polarity, if compared with the same values when operating on reverse polarity. Therefore, work on reverse polarity makes sense in the following cases:
• If you want to weld thin sheet metal. Since the temperature on the reverse polarity is smaller, the workpiece will not burn.
• When working with high alloy steels. "Reverse" in this case significantly reduces the probability of overheating of the part.
To work on direct polarity is better with massive billets, which need to be warmed up well for high-quality welding.
In welding, there are three main characteristics that directly affect the quality of work:
• Welding current.
• The diameter of the workpiece.
• Thickness of the working material.
To begin with, it is necessary to determine the dependence of the diameter of the working element and the thickness of the part to be worked on. For example, steel thickness of up to 1.5 mm. it is brewed almost always with the help of a semi-automatic machine or argon welding.
Arc welding is practically not used for this. Steel thickness of 2mm is cooked with electrodes with a diameter of 2.5mm. To qualitatively weld steel thickness of 3 mm, you need electrodes with a diameter of 2.5-3 mm.
For steel thickness of 5 mm - electrode 3.2-4 mm.
In work with products with a thickness of 6 to 12 mm. Working elements with a diameter of 4-5 mm are used.
For steel thicker than 13 mm. an electrode of 5 mm is used.
An important point: the larger the diameter of the electrode, the lower the density of the working current. As a result, the arc begins to oscillate, "wander", change the length and behave unstably. Because of this, the depth of the seam decreases, and the width, on the contrary, increases. In most cases, manufacturers of such electrodes indicate on the packaging the required welding current. If the manufacturer has not indicated the necessary information, it is necessary to focus on the following indicators:
• For an electrode 2 mm in diameter, a current of 55-65 A is required.
• For an electrode with a width of 2.5 mm - 65-80 A.
• For 3 mm - 70-130A.
• For 4 mm - 130-160 A.
• For 5 mm - 180-210 A.
• For 6 mm - 210-240 A.
Proceeding from the foregoing - when choosing a working element of a certain diameter for welding, it is necessary first of all to pay attention to the thickness of the workpiece. If you work on a thin metal electrode with a large diameter, or exceed the welding current, there will always be pores in the joint.
Marking of welding electrodes
The most common brand among foreign manufacturers of electrodes is ESAB.
The name of each type of electrodes of this brand begins with OK, followed by a 4-digit designation. There are so many variations on sale, but the most common are the following:
• OK 46.00 - the electrode is almost identical to the properties of the brand MR-3. Excellent for working with low-alloy and carbon steels. Suitable for AC and DC. Provides high-quality seam.
• OK 48.00. Designed to work on responsible structures. Work only on direct current.
• OK 61.30 and OK 63.20. Used for welding "stainless steel" of almost all brands. Before buying, you should definitely ask the sales consultant if these electrodes are suitable for working with a particular brand of stainless steel.
• OK 68.81. Beautiful model. Excellent for welding products from steels of undefined composition and difficult to weld parts.
• OK 92.60. Electrodes for cast iron and the connection of cast iron parts with different types of steels.
• OK 96.20. Electrodes for aluminum.
Criteria for selecting suitable electrodes
Analyzing all of the above, you can identify several key points, which must be sure to pay attention, choosing electrodes for electric welding. To begin with, you need to determine exactly which metal to work with and choose an electrode by the type of metal. If you have to work with a responsible design, it is better not to save money and buy products from a well-known manufacturer. For example, Swedish products, which we mentioned above, have proved very good. If you need to weld carbon steel parts, be sure to keep the surface clean. If it is covered with oil, moist or rusty, you should purchase electrodes that have a rutile coating. If it is necessary to work on critical structures, it is recommended to use working elements with a basic coating.
However, in any situation, you need to remember that all products require preliminary surface preparation. In addition, you need to accurately determine the thickness of the workpiece, based on which, select the optimal welding current.
The selection process should be approached as responsibly as possible. If the electrodes are selected correctly, even the cheapest inverter can cook almost any metal at the highest level.
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