Core Technology of Wear-Resistant Welding Wire: How High-Carbon Chromium Iron Powder Enhances Wear Resistance
I. Analysis of Key Influencing Factors on Wear Resistance of Wear-Resistant Welding Wire
1.1 Composition and Microstructure of Welding Wire Matrix Material
The matrix material of welding wire is the foundation of wear-resistant welding wire, and its chemical composition and microstructure exert a fundamental impact on the wear resistance of deposited metal. From the perspective of chemical composition, elements such as carbon, manganese, and silicon in the matrix material not only affect the welding process performance of the welding wire but also interact with elements in the reinforcing material to regulate the formation and distribution of strengthening phases in the deposited metal. For example, carbon can form carbides with elements like chromium and tungsten, while manganese can improve the fluidity of the molten pool and enhance the compactness of welded joints. In terms of microstructure, the grain size and phase composition of the matrix material directly determine the initial mechanical properties of the deposited metal. A matrix material with a fine-grained structure typically has higher strength and toughness, providing an excellent carrier for the uniform distribution of strengthening phases. Moreover, the proportion of phases such as pearlite and ferrite in the matrix also affects the hardness and wear resistance of the deposited metal. Rational regulation of the matrix microstructure is an important basis for improving wear resistance.
1.2 Types and Distribution Rules of Alloy Strengthening Phases
Alloy strengthening phases are the core elements for improving the wear resistance of wear-resistant welding wire, and their type, quantity, size, and distribution state directly determine the effect of wear resistance improvement. In the deposited metal of wear-resistant welding wire, common alloy strengthening phases mainly include carbides, nitrides, borides, etc. Among them, carbide phases are widely used due to their high hardness and stability. Different types of carbide phases have different hardness and stability. For instance, the hardness of Cr₇C₃ reaches as high as 1800–2200 HV, which is much higher than that of the matrix material, exerting a significant effect on improving wear resistance. In addition, the distribution rule of alloy strengthening phases is also crucial. Uniformly dispersed strengthening phases can more effectively hinder the movement of abrasive particles and avoid excessive local wear. Conversely, the aggregation and segregation of strengthening phases will lead to uneven performance of the deposited metal, reducing its wear resistance and toughness. Therefore, rationally selecting the type of alloy strengthening phases and regulating their uniform distribution through technical means are key links to improve the wear resistance of wear-resistant welding wire.
1.3 Regulation Mechanism of Welding Process on Wear Resistance of Deposited Metal
The welding process is a key procedure connecting the welding wire with the matrix material and forming the deposited metal. Its process parameters (such as welding current, voltage, welding speed, type of shielding gas, etc.) play an important regulatory role in the chemical composition, microstructure, and wear resistance of the deposited metal. The magnitude of welding current and voltage directly affects the welding heat input, which in turn influences the temperature and cooling rate of the molten pool. A higher heat input will increase the temperature of the molten pool, cause grain coarsening of the deposited metal, and excessive dissolution of strengthening phases, thereby reducing its hardness and wear resistance. On the other hand, a lower heat input may lead to insufficient welding, resulting in defects such as incomplete penetration and slag inclusion, which also affect the performance of the deposited metal. Welding speed affects the forming quality and cooling rate of the deposited metal; a reasonable welding speed can ensure the deposited metal has a uniform thickness and dense structure. The type and flow rate of shielding gas are mainly used to prevent oxidation of the molten pool, ensure the stability of the welding process, and avoid adverse effects of oxidation products on the performance of the deposited metal. Therefore, optimizing welding process parameters to achieve precise regulation of the microstructure of the deposited metal is an important guarantee for improving the wear resistance of wear-resistant welding wire.
1.4 Core Evaluation Indicators and Standardized Testing Methods for Wear Resistance
Accurate evaluation of the wear resistance of wear-resistant welding wire is the basis for promoting technological research and development and application. At present, a series of core evaluation indicators and standardized testing methods have been formed in the industry. Core evaluation indicators mainly include hardness, wear loss, relative wear resistance, etc. Hardness is an important index to measure the material's resistance to local deformation and wear, usually tested by Brinell hardness (HB), Rockwell hardness (HRC), or Vickers hardness (HV) methods. Deposited metal with high hardness generally has better wear resistance. Wear loss refers to the mass loss or volume loss of the material under certain wear conditions; the smaller the wear loss, the better the wear resistance of the material. Relative wear resistance is obtained by comparing the wear loss of the tested material with that of the standard material, which can more intuitively reflect the wear resistance advantages of the tested material. Standardized testing methods mainly include abrasive wear test, impact wear test, sliding wear test, etc. Different testing methods simulate different wear conditions, enabling a comprehensive evaluation of the wear resistance of wear-resistant welding wire under different service conditions. For example, the abrasive wear test mainly simulates the working conditions of mining machinery subjected to abrasive cutting, while the impact wear test simulates the working conditions of engineering machinery subjected to the combined action of impact and wear. Through standardized testing methods and evaluation indicators, objective and accurate data support can be provided for the performance comparison and technological research and development of wear-resistant welding wire.
II. Preparation Process and Adaptation Technology of High-Carbon Chromium Iron Powder in Wear-Resistant Welding Wire
2.1 Optimization of Wear-Resistant Welding Wire Preparation Process and High-Carbon Chromium Iron Powder Addition Method
2.1.1 Ratio Design and Uniform Mixing Process of High-Carbon Chromium Iron Powder in Flux-Cored Welding Wire
Flux-cored welding wire is one of the most widely used carriers for high-carbon chromium iron powder. In its preparation process, the ratio design and uniform mixing process of high-carbon chromium iron powder are the keys to ensuring the performance of the welding wire. In terms of ratio design, it is necessary to reasonably determine the proportion of high-carbon chromium iron powder and other components (such as iron powder, ferromanganese, ferrosilicon, graphite, slag former, etc.) according to the target wear resistance, welding process performance, and comprehensive mechanical property requirements of the welding wire. If the proportion of high-carbon chromium iron powder is too low, insufficient carbide phases will be formed, and the strengthening effect will be insignificant. If the proportion is too high, the toughness of the deposited metal will decrease, the susceptibility to welding cracks will increase, and the cost will also rise. Generally, it is reasonable to control the proportion of high-carbon chromium iron powder in flux-cored welding wire between 20% and 40%. In terms of uniform mixing process, to ensure the uniform distribution of high-carbon chromium iron powder inside the flux core, it is necessary to adopt efficient mixing equipment and reasonable mixing processes. Currently, commonly used mixing equipment includes conical mixers and double-helix mixers. During the mixing process, parameters such as mixing time and rotation speed need to be controlled to avoid uneven mixing or particle agglomeration. In addition, before mixing, high-carbon chromium iron powder and other components need to be dried to remove moisture and impurities, ensuring mixing quality and the welding process performance of the welding wire.
2.1.2 Preparation Technology of High-Carbon Chromium Iron Powder Coating on the Surface of Solid Welding Wire
In addition to flux-cored welding wire, coating the surface of solid welding wire with a coating containing high-carbon chromium iron powder is also an important application form of high-carbon chromium iron powder. The core of this preparation technology is to mix high-carbon chromium iron powder with binders and other alloying elements to prepare coating materials through certain technological means, uniformly coat them on the surface of solid welding wire, and form a coating with a certain thickness and strength after drying and curing. The key to this technology lies in the formula design of coating materials and the optimization of coating processes. In the coating material formula, the content of high-carbon chromium iron powder needs to be reasonably adjusted according to the target performance. The binder should have good bonding strength and high-temperature stability to ensure that the coating does not fall off or decompose during the welding process. In terms of coating processes, common methods include dip coating, spray coating, roll coating, etc. The dip coating method has the advantages of simple process and low cost but poor uniformity of coating thickness. The spray coating method can obtain a uniform coating thickness but has high equipment costs. The roll coating method combines the advantages of simple process and uniform coating thickness, so it is widely used. In addition, the drying and curing processes of the coating are also crucial; the temperature and time need to be controlled to ensure the coating has good strength and stability and avoid defects during the welding process.
2.2 Experimental Study on Optimization of High-Carbon Chromium Iron Powder Addition Amount
2.2.1 Influence of Addition Amount on Welding Wire Deposition Efficiency
The addition amount of high-carbon chromium iron powder not only affects the wear resistance of the deposited metal but also has a significant impact on the deposition efficiency of the welding wire. Deposition efficiency is an important index to measure the welding performance of the welding wire, referring to the ratio of the mass of deposited metal to the mass of consumed welding wire per unit time. A large number of experimental studies have found that there is a nonlinear relationship between the addition amount of high-carbon chromium iron powder and deposition efficiency. When the addition amount is small, high-carbon chromium iron powder has little effect on deposition efficiency. With the increase of addition amount, deposition efficiency will gradually improve because some elements in high-carbon chromium iron powder can improve the fluidity of the molten pool and promote the melting and deposition of the welding wire. However, when the addition amount exceeds a certain threshold, deposition efficiency will start to decline. This is because high-carbon chromium iron powder has a high density; excessive addition will slow down the melting speed of the welding wire. Meanwhile, the formation of excessive carbide phases will increase the viscosity of the molten pool, hindering the flow and forming of the deposited metal. Therefore, it is necessary to determine the optimal addition range of high-carbon chromium iron powder through optimization experiments to ensure the wear resistance of the deposited metal while taking into account high deposition efficiency.
2.2.2 Evolution Law of Wear Resistance of Deposited Metal with Different Addition Amounts
The wear resistance of deposited metal shows an obvious evolution law with different addition amounts of high-carbon chromium iron powder. Test results show that with the increase of high-carbon chromium iron powder addition amount, the number of carbide phases in the deposited metal gradually increases, and the hardness and wear resistance also increase accordingly. When the addition amount reaches a certain value, the hardness and wear resistance of the deposited metal reach the peak. If the addition amount continues to increase, the hardness and wear resistance of the deposited metal will not improve but will instead decrease, and the toughness will also decrease significantly. This is because when the addition amount is too high, the number of carbide phases is excessive, leading to aggregation and segregation, which results in an uneven microstructure of the deposited metal and local stress concentration. During the wear process, cracks are prone to occur, accelerating wear failure. In addition, excessive carbide phases will also reduce the welding process performance of the deposited metal and increase the risk of welding cracks. Therefore, determining the optimal addition amount of high-carbon chromium iron powder through experiments is the key to achieving a balance between the wear resistance and comprehensive mechanical properties of the deposited metal.
2.3 Compatibility Regulation Technology between High-Carbon Chromium Iron Powder and Other Components of Welding Wire
The compatibility between high-carbon chromium iron powder and other components of welding wire (such as matrix metal, other alloying elements, slag formers, deoxidizers, etc.) directly affects the welding process performance of the welding wire and the performance of the deposited metal. Therefore, effective regulation technologies need to be adopted to ensure good compatibility. Firstly, in terms of component selection, it is necessary to reasonably select other components according to the chemical composition and physical properties of high-carbon chromium iron powder. For example, selecting ferromanganese, ferrosilicon, etc., with good deoxidation ability as deoxidizers can effectively remove oxygen in the molten pool, avoid the formation of oxides between oxygen and chromium, and prevent the impact on the formation of carbide phases. Selecting appropriate slag formers can ensure the formation of good slag during the welding process, protect the molten pool and weld seam, and reduce the generation of defects. Secondly, in terms of ratio regulation, it is necessary to optimize the proportion of each component through experiments to avoid compatibility problems caused by excessive or insufficient amounts of a certain component. For example, an excessively high proportion of slag formers may lead to excessive slag, affecting the forming of the deposited metal; insufficient proportion of deoxidizers cannot effectively remove harmful elements. In addition, the interaction between various components can be improved and compatibility can be enhanced by adding an appropriate amount of master alloys or rare earth elements. Rare earth elements have good purification and modification effects, which can refine grains, improve the distribution of carbide phases, enhance the bonding force between various components, and improve the comprehensive performance of the welding wire.