Method of alloying deposited metal with carbon during arc welding and surfacing

Abstract

FIELD: welding technologies.SUBSTANCE: invention relates to alloying methods in electric arc welding and surfacing with a consumable electrode in a protective gas environment and can be used to form coatings and layers of metal operating under conditions of abrasive and impact wear, as well as for a wide range of low-carbon and low-alloy steels. The method includes feeding a protective gas mixture based on carbon monoxide into the welding and surfacing zone, feeding an electrode wire, exciting an electric arc between the consumable electrode and the product in said gas environment, and creating a permanent connection. The protective gas mixture additionally comprises acetylene, and the metals of the permanent joint are alloyed with carbon due to the formation of atomic carbon during the thermal dissociation of acetylene under the influence of the arc temperature, followed by the transfer of atomic carbon into the molten metal of the weld pool, whereas the content of acetylene in the mixture is regulated depending on the specified carbon content in the deposited metal, ensuring that the carbon content in the deposited metal exceeds that of the original electrode material by 0.02-0.80%.EFFECT: ensuring precise adjustment of the deposited layer by adjusting the carbon content by changing the concentration of acetylene in the mixture, eliminating the formation of pores and cracks characteristic of hydrocarbon gases; and ease of implementation due to the use of standard equipment.1 cl, 1 ex

Description

[0001] The invention relates to alloying methods in electric arc welding and surfacing with a consumable electrode in a protective gas environment and can be used to form coatings and layers of metal operating under conditions of abrasive and impact wear, as well as for a wide range of low-carbon and low-alloy steels.

[0002] A known method of alloying a welded joint with a carbon-containing gas of refractory metals during arc welding with a non-consumable electrode in an inert gas environment, in which a binary mixture of a carbon-containing gas, which is acetylene, amounting to 3-4 vol.%, with an inert gas, which is argon, is introduced into the root zone of the seam, and pure argon is supplied to the surface of the seam and the tungsten electrode, a welding arc is excited and a permanent connection is created (patent RU 2027564, IPC B23K 9 / 16 (1995.01), B23K 35 / 38 (1995.01).

[0003] This method allows for partial introduction of additives from the gas phase, but requires separate supply of two gas streams, which increases the complexity of its implementation due to the complexity of the equipment design and reduced process productivity. Furthermore, the absence of a reducing component in the protective atmosphere does not provide reliable protection against oxidation of alloying elements in the arc zone, even with the inertness of argon, due to possible oxygen impurities. It also does not allow for controlled alloying of the deposited metal during welding and consumable electrode surfacing, resulting in reduced weld quality.

[0004] The closest to the proposed invention in technical essence and the achieved result (prototype) is a method for alloying the deposited metal during arc welding and surfacing, including the supply of a protective reducing gas environment to the welding and surfacing zone, the supply of electrode wire, excitation of the arc and the formation of a permanent connection. As a protective gas environment, gas mixtures based on carbon monoxide containing vapors of organometallic compounds are used, which are metal carbonyls, and alloying of the metals of the permanent connection is carried out due to the dissociation of the organometallic compounds included in the protective gas environment (patent RU 2697132, IPC B23K 9 / 16 (2006.01), B23K 35 / 38 (2006.01).

[0005] The disadvantages of the method of alloying the deposited metal in arc welding and surfacing include, firstly, the significant complexity of the process and increased safety requirements due to the use of toxic and thermally unstable organometallic compounds; secondly, increased labor intensity and reduced productivity, since the supply of carbonyl vapors requires special metering and sealed equipment; thirdly, limited ability to increase the hardness and regulate the structure of the deposited layer, since alloying of the metal is carried out mainly by elements included in the composition of carbonyls, and does not provide for a controlled change in the carbon content in the deposited metal,

[0006] The technical problem solved by the invention is to create a method for alloying deposited metal with carbon during arc welding and surfacing, which allows, firstly, to reduce the complexity of the process and safety requirements due to the use of industrial gases instead of toxic and thermally unstable organometallic compounds; secondly, to reduce the labor intensity of the process and to increase productivity due to the use of standard equipment, existing production lines for surfacing wear-resistant coatings, integration into existing gas welding equipment and the use of only available industrial gases; thirdly, to expand the possibilities for increasing the hardness and regulating the structure of the deposited layer by controlled increase in the carbon content in the deposited metal compared to the electrode material.

[0007] The technical result consists in a controlled increase in the carbon content in the deposited metal compared to the electrode material by changing the concentration of acetylene in the gas mixture with an increase in the hardness of the permanent joint; in preventing the burnout of manganese, silicon and other alloying elements, since carbon monoxide ensures the reducing nature of the atmosphere, preventing the burnout of alloying elements; in the implementation of the use of standard wires and available industrial gases, which leads to a reduction in the cost of the alloying process.

[0008] The solution to this technical problem is achieved by the fact that in the method of alloying the deposited metal with carbon during arc welding and surfacing, which includes feeding a protective gas mixture based on carbon monoxide into the welding and surfacing zone, feeding an electrode wire, exciting an electric arc between the consumable electrode and the product in the said gas environment, creating a permanent connection, according to the invention, the protective gas mixture additionally contains acetylene, and alloying the metals of the permanent connection with carbon is carried out due to the formation of atomic carbon during the thermal dissociation of acetylene under the influence of the arc temperature, followed by the transition of atomic carbon into the molten metal of the weld pool, while regulating the acetylene content in the mixture depending on the specified carbon content in the deposited metal, ensuring that the carbon content in the deposited metal exceeds that of the original electrode material by 0,02-0.80%.,

[0009] This results in an increase in the carbon content of the deposited metal, resulting in increased hardness. This also expands the process's technological capabilities by regulating the composition of the gas environment.

[0010] The proposed method of alloying the metal of a permanent joint with carbon is implemented as follows.

[0011] The metal is pre-prepared for surfacing: the surface is cleaned and shaped to the desired geometry. The welding current, electrode wire diameter, and composition are selected. Depending on the required carbon content, the acetylene content of the shielding gas mixture, the mixture flow rate, and the arc voltage are selected.

[0012] The process of alloying a permanent joint with carbon during surfacing involves feeding a carbon monoxide-based shielding gas mixture into the surfacing zone, feeding an electrode wire, striking an arc, and creating a permanent joint. The process is carried out by striking an arc between the electrode wire and the workpiece while simultaneously supplying a shielding gas mixture. A gas mixture of carbon monoxide and acetylene is used. The permanent joint is created by thermal dissociation of the acetylene in the gas mixture near the electrode under the influence of the arc temperature, forming atomic carbon that is transferred into the molten metal of the weld pool. This, in turn, increases the carbon content in the deposited metal compared to the electrode material.

[0013] An example of implementing the proposed method.

[0014] The surfacing was performed using Sv-08G2S wire at a current of 220 A and a voltage of 25 V. A mixture of carbon monoxide CO and acetylene C2H2 was used as a shielding gas mixture. The carbon content of the electrode material is 0.08%.

[0015] Gas flow rate: 15 l / min. Carbon monoxide (CO) with up to 5% acetylene (C2H2) added was used as the shielding gas mixture. The carbon content in the deposited metal increased by 0.03% compared to the original electrode material.

[0016] The hardness of the deposited layer increased from 190 to 220 HB.

[0017] The microstructure is finely dendritic ferrite-pearlite, no pores or inclusions were found.

[0018] Gas flow rate: 20 l / min. The acetylene C2H2 content in the shielding gas mixture was doubled. The carbon content in the deposited metal increased by 4.1 times to 0.33%. The hardness of the deposited layer increased to 336 HB. The metal structure is bainitic.

[0019] Gas flow rate: 30 l / min. The acetylene C2H2 content in the shielding gas mixture was increased by 4 times compared to the original. The carbon content in the deposited metal increased by 10 times to 0.80%. The hardness of the deposited layer was 550-600 HB. Microstructural heterogeneity in the weld metal was noted.

[0020] Further increase in the acetylene content in the gas mixture leads to the formation of large pores and a significant amount of soot, and further increases the microstructural heterogeneity.

[0021] From the given example, it follows that an increase in the carbon content in the gas mixture leads to an increase in the hardness of the deposited layer.

[0022] The novelty of the proposed method is due to the combination of the following essential features that ensure the achievement of the stated technical result:

[0023] - feeding a protective gas mixture of carbon monoxide CO and acetylene C2H2 into the welding or surfacing zone;

[0024] - excitation of an electric arc between a consumable electrode and a product in a specified gas environment;

[0025] - thermal dissociation of acetylene under the influence of arc temperature with the formation of atomic carbon, which diffuses into the molten metal of the weld pool;

[0026] - maintaining a reducing atmosphere due to carbon monoxide, preventing the oxidation of alloying elements - manganese, silicon and others;

[0027] - adjustment of the acetylene content in the mixture depending on the required level of carbon alloying: increase by 0.02 0.80% compared to the electrode material.

[0028] The specified set of features allows for the controlled carburization of deposited metal without additional reagents, differing from known analogs (patent RU 2027564 and patent RU 2697132) both in the composition of the gas environment and in the mechanism of protection against oxidation and ease of integration into standard equipment.

[0029] The advantages of the invention include cost-effectiveness achieved through the use of standard industrial gases CO and C2H2, the provision of precise adjustment of the deposited layer by adjusting the carbon content by changing the concentration of acetylene in the mixture, the elimination of the formation of pores and cracks characteristic of hydrocarbon gases; ease of implementation due to the use of standard equipment, integration into existing equipment for mechanized welding; a wide range of application for a wide range of low-carbon and low-alloy steels, as well as for parts with increased wear resistance requirements.

[0030] The method is industrially applicable and can be implemented on existing production lines for surfacing wear-resistant coatings.

Claims

A method for alloying deposited metal with carbon during arc welding and surfacing, which includes feeding a protective gas mixture based on carbon monoxide into the welding and surfacing zone, feeding an electrode wire, exciting an electric arc between a consumable electrode and a product in the said gas environment, creating a permanent connection, characterized in that the protective gas mixture additionally contains acetylene, and alloying the metals of the permanent connection with carbon is carried out due to the formation of atomic carbon during the thermal dissociation of acetylene under the influence of the arc temperature, followed by the transfer of atomic carbon into the molten metal of the weld pool, while regulating the acetylene content in the mixture depending on the specified carbon content in the deposited metal, ensuring that the carbon content in the deposited metal exceeds that of the original electrode material by 0.02-0.80%.