How to cook low-alloy steels: the secrets of a successful weld
A type of steel in which, in addition to carbon, iron and impurities, there are also alloying components, is called low-alloyed. It is actively used in the surgical, jewelry and engraving sphere due to its strength and the ability to withstand temperatures of 200 degrees Celsius.
It is important that the level of impurities in the composition of the steel does not exceed 2.5%. These "additives" include silicon, chromium, vanadium, manganese, and others. These components make steel special, qualitatively distinguishing from other options.
In addition to significant strength, carbon and low-alloy structural steels are characterized by a good welding index and viscosity level. Low-alloyed steel has a minimum threshold of cold brittleness, and the “filling” of additional components (chromium and nickel) makes products made from it non-corrosive - to find out the exact characteristics of rolled metal products https://sortmet.ru/
Features of welding low alloy steels
The process of welding low-alloy steel is complex and time consuming. It has a sensitive thermal exposure threshold, which can cause overheating in the weld area.
The cooling rate of such a metal in the process of welding exceeds the usual rates, especially when it comes to steel with an impressive thickness. That is why the appearance of martensite, an alloy structure, which is characterized by low ductility and considerable hardness, is a frequent occurrence in such welding.
Special attention should be paid to the selection of welding electrodes. The content of "harmful" components in the form of phosphorus or sulfur should not be present in the composition. This trick can significantly improve the quality of the weld.
If such products are used at the lowest possible temperatures, metal creep is excluded. In such a case, it is necessary to use a fine-grained metal structure. This will increase the structural strength and plasticity of the product.
Also, the labor-intensive welding process of this type of steel requires high professional skills and experience in working with such materials.
Welding technology for low alloy steels
Low carbon varieties are not difficult to weld. Such options are not subject to the overheating process, which can lead to poor plasticity of the product.
With increasing carbon levels, the welding process also changes. It is important to monitor the temperature in the area of welding. You can use a welding method called "cascade" or "blocks."
Material that is planned to be subjected to welding work, you must first clean. Surfaces and edges should be free of rust, dirt, paint and other nuances.
It is recommended to cut the welding places and clean them thoroughly with an abrasive tool. This is done flush with the base metal.
Welding of low-alloy steels is largely determined by GOST. If you need to know all the features and technical nuances, then you should resort to studying the documentation that regulates the process of welding low-alloyed steel.
When the thickness of the steel is over 25 mm, it uses the method of preheating the welding spot to a temperature of 120-160 degrees Celsius.
At air temperatures of minus 15 degrees and below, such heating is used regardless of the material thickness.
Particular attention is paid to the welding of low-alloy heat-resistant options.In the process cracks may form in the area of thermal influence. This happens more often if carbon or chromium is too high. Therefore, starting the process of welding, it is very important to choose a loyal thermal mode, and to choose the right electrodes - there are 9 options for this type of steel.
A common cause of cracks in the welding zone is hydrogen dissolved in steel. It enters the weld zone from the electrode coating, moisture or rust. To eliminate this negative point, you need:
- increase the temperature of the calcination of the electrodes;
- use low-temperature heat treatment to remove hydrogen;
- apply high tempering in all types of steel.
The use of an electrode that does not melt in argon, protects the metal and guarantees considerable strength.
To control the temperature regime to prevent overheating, use thermocouples, thermal indicator pencils or thermoelectric pyrometers.
In some cases it is rational to continue heating and close the seam with asbestos cloth after the welding process in order to preserve the thermal regime.
It is recommended to weld short seams on the front side, middle ones - from the middle towards the ends, and long ones - backwards - in a stepped manner.
The nuances of welding low-alloy steel
For the welding process to be successful, it is necessary to take into account the nuances of such work:
- the possibility of defects in the form of weld cracks;
- can be used to pre-weld the root root;
- arc welding of this type has become desirable to accompany with the restriction of heat input;
- The choice of welding method should be based on the reduction of stress in welded joints.
If you adhere to such recommendations, you can weld low alloy steel and avoid work defects.