High-hardness wear-resistant flux-cored wire for open arc surfacing of coal mine machinery and preparation method of high-hardness wear-resistant flux-cored wire

Abstract

The invention discloses a high-hardness wear-resistant flux-cored wire for open arc surfacing of coal mine machinery, which belongs to the technical field of welding materials and consists of flux-cored powder and a carbon steel strip. The flux core powder comprises the following raw materials of 20%-80% of high-carbon ferrochrome, 1%-8% of high-carbon ferromanganese, 1%-10% of graphite, 1%-5% of ferrotitanium, 1%-5% of silicon carbide, 0.5%-4% of boron carbide and 0.1%-2% of cryolite. The welding wire is applied to repairing of the chain wheel of the scraper conveyor of the coal mine, the service life is 2.3 times that of a common welding wire, and the comprehensive cost is reduced by 40%.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, and more specifically to a high-hardness, wear-resistant flux-cored welding wire for open-arc surfacing welding in coal mine machinery and its preparation method. Background Technology

[0002] In coal mining and processing, key components such as crusher hammers, trough liners, and scraper conveyor wear plates are subjected to a combination of impact, abrasive wear, and corrosion over long periods, leading to rapid surface failure. Statistics show that equipment downtime replacement costs account for more than 15% of total production costs, significantly increasing overall costs. Traditional solutions mainly rely on complete replacement or surface welding repair. Complete replacement requires frequent equipment disassembly, causing production interruptions and significantly increasing the cost per ton of coal produced. While conventional welding repair can extend component lifespan, it has significant drawbacks. When using solid welding wire in conjunction with submerged arc welding or gas shielded welding, the hardness (usually ≤55HRC) and wear resistance of the deposited metal are insufficient, making it difficult to withstand the wear of coal ore. High-carbon, high-alloy flux-cored welding wire weld layers are prone to hot cracking, especially in stress concentration areas such as hammerhead cutting edges, where spalling occurs under impact loads. Improper preheating temperature control during on-site repair (generally below 300℃) leads to hydrogen-induced cooling cracks between the substrate and the weld layer, reducing bond strength.

[0003] Existing wear-resistant flux-cored welding wires are mostly designed for general working conditions. Their alloy systems are not well-suited to the impact and abrasive wear environments of coal mines. The distribution of carbide reinforcing phases is uneven, and stress concentration is exacerbated when the size of the hard phase exceeds 20μm. Although excessive addition of boron increases hardness, it reduces toughness to 15J / cm. 2 The following factors accelerate fatigue failure. Furthermore, the poor matching between the welding process parameters and the component structure results in a repair layer thickness fluctuation exceeding ±1.5mm, requiring secondary processing and increasing time and energy costs.

[0004] Therefore, there is an urgent need to develop specialized wear-resistant flux-cored welding wire and supporting processes that can be used for field welding repairs. By optimizing alloy composition and deposition control, efficient repair and performance improvement of wear-resistant parts for coal mining machinery can be achieved. Summary of the Invention

[0005] In view of this, the present invention provides an open arc welding flux-cored wire suitable for surface strengthening and repair of coal mine mechanical parts, which has high hardness and excellent wear resistance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A high-hardness wear-resistant flux-cored welding wire for open arc welding in coal mine machinery is composed of flux-cored powder and carbon steel strip, wherein the flux-cored powder accounts for 20%-50% of the mass of the welding wire, and the remainder is carbon steel strip;

[0008] The core powder comprises the following raw materials by mass percentage:

[0009] The composition is: 1%-8% high-carbon ferromanganese, 1%-10% graphite, 1%-5% ferrotitanium, 1%-5% silicon carbide, 0.5%-4% boron carbide, 0.1%-2% cryolite, with the balance being high-carbon ferrochrome.

[0010] The high-carbon ferrochrome contains a Cr content of not less than 65%, a C content of 8-10%, and the balance is Fe.

[0011] The high-carbon ferromanganese contains not less than 75% Mn, 7-8% C, and the balance is Fe.

[0012] In this invention, high-carbon ferrochrome is used to adjust the composition of the cladding metal and increase its hardness. High-carbon ferromanganese can stabilize the arc, deoxidize and purify the molten pool, and enhance the mechanical properties of the weld layer. Graphite can adjust the fluidity of the molten pool, wire feeding smoothness, and arc stability, as well as deoxidize and desulfurize, and prevent porosity. Carbon participates in alloying to form carbides. Ferrotitanium is used for deoxidation and weld purification, improving welding processes and refining grains. Silicon carbide can improve hardness and wear resistance, adjust the fluidity and wettability of the molten pool, and assist in deoxidation. Boron carbide can provide a hard phase, improve the wear resistance of the weld layer, and refine the grains. Cryolite is used to reduce the content of diffusible hydrogen, stabilize the arc, and improve the slag removal properties of the molten slag.

[0013] Furthermore, the Ti content in the ferrotitanium is not less than 30%.

[0014] This invention also provides a method for preparing the above-mentioned high-hardness wear-resistant flux-cored welding wire for open-arc welding in coal mine machinery, comprising the following steps:

[0015] (1) Weigh the raw materials according to the above mass fraction, and mix the weighed core powder raw materials evenly to obtain core powder;

[0016] (2) Roll the carbon steel strip into a U-shape to form a U-shaped groove, and add core powder into the U-shaped groove;

[0017] (3) The U-shaped groove containing the core powder is pressed into a cylindrical shape, compacted by rollers, and then drawn into diameter by polycrystalline die several times to finally obtain the welding wire.

[0018] Furthermore, the width of the carbon steel strip is 10-16mm and the thickness is 0.3mm-0.6mm.

[0019] Furthermore, the characteristic feature is that the diameter of the welding wire is 1.0-4.0 mm.

[0020] The drawing reduction in step (3) is performed 5 times, with each reduction compression rate being 5-20% of the current diameter.

[0021] The beneficial effects of this invention are as follows:

[0022] The welding wire of this invention optimizes the flux core composition by introducing multiple hard phase-forming elements such as high-carbon ferrochrome, boron carbide, and silicon carbide. This forms a network of (Cr,Fe)7C3 carbides and dispersed SiC particles in the weld overlay, resulting in a weld overlay hardness of 58-65 HRC and significantly improved wear resistance. In the repair application of scraper conveyor sprockets in coal mines, its service life is 2.3 times that of ordinary welding wires. By adding ferrotitanium and cryolite, the generation of hot cracks and hydrogen-induced cooling cracks during the weld overlay process is effectively suppressed, making it less prone to spalling even in complex stress areas. It is suitable for the high-impact and high-wear conditions of coal mining machinery. The welding wire prepared by this invention has good shape, no surface defects, and stable filling rate. It adopts an open arc weld overlay process, which is simple to operate, requires low interlayer temperature control, and produces a uniform weld overlay thickness without incomplete fusion, significantly reducing the difficulty of on-site repair. This welding wire combines high hardness, high wear resistance, good crack resistance, and process adaptability, effectively extending the life of components, avoiding complete replacement, reducing equipment downtime, and achieving a service life 2.3 times that of ordinary welding wire. This reduces overall costs by 40%, resulting in significant economic benefits. It is particularly suitable for surface strengthening and repair of coal mine machinery components. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the forming process of the flux-cored welding wire of the present invention.

[0024] Figure 2 The image shows the appearance of the formed flux-cored welding wire prepared according to the present invention, wherein the surface of the welding wire is free of burrs, scratches, and rust.

[0025] Figure 3 This is a cross-sectional view of the four-layer weld overlay in Embodiment 1 of the present invention (the layer thickness is uniform);

[0026] Figure 4 This is a surface view of the No. 45 steel plate substrate after sandblasting treatment in Example 1 of the present invention (Sa = 3.2 μm);

[0027] Figure 5 The microstructure of the fusion zone after welding in Embodiment 1 of the present invention (without unfused areas);

[0028] Figure 6 The image shown is a metallographic diagram of the weld overlay layer in Embodiment 1 of the present invention.

[0029] Figure 7 The figure shows the results of the friction coefficient measurement of the weld overlay in Embodiment 1 of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] Cold-rolled carbon steel strip (14mm wide, 0.4mm thick) with a diameter of 0.4mm and a thickness of 14mm is selected. The flux-cored powder accounts for 45% of the welding wire mass, with the remainder being carbon steel strip.

[0033] The raw materials for the core powder are 84.5% high-carbon ferrochrome, 4% high-carbon ferromanganese, 5% graphite, 3% ferrotitanium, 2% silicon carbide, 1% boron carbide, and 0.5% cryolite. All the raw materials are powders that can pass through an 80-mesh sieve.

[0034] The flux-cored powder is mixed in a three-dimensional motion mixer for 300 minutes. The mixed powder is then dried in a drying oven at 120°C for 24 hours. The mixed powder is then added to the flux-cored wire forming machine with a filling rate of 30%. The carbon steel strip is rolled into a U-shaped groove. The wire drawing speed is set to 15 m / min. The wire is then rolled, filled with powder, and pressed.

[0035] Finally, the wire is drawn and reduced in diameter through dies of 4.0mm, 3.8mm, 3.6mm, 3.4mm, and 3.2mm. The final diameter reaches 3.2mm after passing through a shaping die, and the welding wire is obtained. The filling rate of the welding wire is then checked to see if it is stable.

[0036] The prepared welding wire was used for surfacing on a sandblasted 45# steel plate. The welding current was 260-290A, the welding voltage was 40-50V, and the shielding gas flow rate was 14-16L / min. Four layers were surfacing, with an interpass temperature of less than 150℃. The height of each layer was 10mm, and the dimension of each pass was 10mm. After the sample cooled, surface flaw detection and ultrasonic testing were performed, and no cracks were found on the surface or inside the surfacing layer.

[0037] A 200HRS-150 digital display Rockwell hardness tester was used, with a load of 150kg and a holding time of 5s. Five points were taken to test the hardness of the weld overlay in Example 1, and the average Rockwell hardness of the weld overlay was finally obtained.

[0038] The friction coefficient was measured using an MS-M9000 dynamic damage and protection tester. Three 10*10*15mm wear specimens were taken from the weld overlay. The test parameters were as follows: initial load of 10N, loading time of 5min, test load of 25N, and loading time of 30min. Before the test, the specimens were sanded to a mirror finish and polished, and finally cleaned in an ultrasonic cleaner for 5-10 minutes.

[0039] The test results show that the chemical composition (wt%) of the prepared welding wire is: Fe 86.31, Cr 9.88, Mn 1.85, Si 0.40, and others 1.96. The surface hardness is 59±1 HRC (after polishing). The cross-sectional hardness gradient is: base material 38 HRC → fusion zone 52 HRC → weld overlay 58-64 HRC.

[0040] Table 1 shows the hardness test results of the weld overlay at 5 points.

[0041] 1 2 3 4 5 hardness 58HRC 60HRC 62HRC 65HRC 65HRC

[0042] The metallographic structure of the welding wire is as follows: the matrix is ​​tempered martensite; the reinforcing phase is a network of (Cr,Fe)7C3 carbides + dispersed SiC particles.

[0043] Abrasion resistance of welding wire: coefficient of friction 0.40 (ASTM G99 standard, load 200N).

[0044] Example 2

[0045] Cold-rolled carbon steel strip (14mm wide, 0.4mm thick) with a diameter of 0.4mm and a diameter of 14mm is selected. The flux-cored powder accounts for 50% of the welding wire mass, with the remainder being carbon steel strip.

[0046] The raw materials for the core powder are 79% high-carbon ferrochrome, 8% high-carbon ferromanganese, 1% graphite, 5% ferrotitanium, 1% silicon carbide, 4% boron carbide, and 2% cryolite. All raw materials are powders that can pass through a 30-mesh sieve.

[0047] The powder was placed in a three-dimensional motion mixer and mixed for 300 minutes. The mixed powder was then placed in a drying oven and dried at 120°C for 24 hours. The mixed powder was then added to the powder hopper of the flux-cored wire forming machine, with a filling rate of 35%. The carbon steel strip was rolled into a U-shaped groove, and the wire drawing speed was set. The welding wire underwent winding, powder filling, and pressing.

[0048] Finally, the wire is drawn and reduced in diameter through dies of 4.0mm, 3.8mm, 3.6mm, 3.4mm, and 3.2mm. The final diameter reaches 3.2mm after passing through a shaping die, and the welding wire is obtained. The filling rate of the welding wire is then checked to see if it is stable.

[0049] The prepared welding wire was used for surfacing on a sandblasted 45# steel plate. The welding current was 260-290A, the welding voltage was 40-50V, and the shielding gas flow rate was 14-16L / min. Four layers were surfacing, with an interpass temperature of less than 150℃. The height of each layer was 10mm, and the dimension of each pass was 10mm. After the sample cooled, surface flaw detection and ultrasonic testing were performed, and no cracks were found on the surface or inside the surfacing layer.

[0050] Example 3

[0051] Select 0.4mm*14mm carbon steel strip (14mm wide, 0.4mm thick). The flux-cored powder accounts for 20% of the welding wire mass, with the remainder being carbon steel strip.

[0052] The raw materials for the core powder are 82.4% high-carbon ferrochrome, 1% high-carbon ferromanganese, 10% graphite, 1% ferrotitanium, 5% silicon carbide, 0.5% boron carbide, and 0.1% cryolite. All the raw materials are powders that can pass through a 30-mesh sieve.

[0053] The powder was placed in a three-dimensional motion mixer and mixed for 300 minutes. The mixed powder was then placed in a drying oven and dried at 120°C for 24 hours. The mixed powder was then added to the powder hopper of the flux-cored wire forming machine, with a filling rate of 40%. The carbon steel strip was rolled into a U-shaped groove, and the wire drawing speed was set. The welding wire underwent winding, powder filling, and pressing.

[0054] Finally, the wire is drawn and reduced in diameter through dies of 4.0mm, 3.8mm, 3.6mm, 3.4mm, and 3.2mm. The final diameter reaches 3.2mm after passing through a shaping die, and the welding wire is obtained. The filling rate of the welding wire is then checked to see if it is stable.

[0055] The prepared welding wire was used for surfacing on a sandblasted 45# steel plate. The welding current was 260-290A, the welding voltage was 40-50V, and the shielding gas flow rate was 14-16L / min. Four layers were surfacing, with an interpass temperature of less than 150℃. The height of each layer was 10mm, and the dimension of each pass was 10mm. After the sample cooled, surface flaw detection and ultrasonic testing were performed, and no cracks were found on the surface or inside the surfacing layer.

[0056] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A high-hardness, wear-resistant flux-cored welding wire for open-arc surfacing welding in coal mine machinery, characterized in that, It consists of flux-cored powder and carbon steel strip, wherein the flux-cored powder accounts for 20%-50% of the welding wire mass, and the remainder is carbon steel strip; The core powder comprises the following raw materials by mass percentage: The composition is: 1%-8% high-carbon ferromanganese, 1%-10% graphite, 1%-5% ferrotitanium, 1%-5% silicon carbide, 0.5%-4% boron carbide, 0.1%-2% cryolite, with the balance being high-carbon ferrochrome. The high-carbon ferrochrome contains a Cr content of not less than 65%, a C content of 8-10%, and the balance is Fe. The high-carbon ferromanganese contains not less than 75% Mn, 7-8% C, and the balance is Fe.

2. The high-hardness wear-resistant flux-cored welding wire for open-arc surfacing welding in coal mine machinery according to claim 1, characterized in that, The titanium-iron alloy contains no less than 30% Ti.

3. A method for preparing a high-hardness, wear-resistant flux-cored welding wire for open-arc surfacing welding in coal mine machinery, characterized in that, Includes the following steps: (1) Weigh the raw materials according to the mass fraction described in claim 1 or 2, and mix the weighed core powder raw materials evenly to obtain core powder; (2) Roll the carbon steel strip into a U-shape to form a U-shaped groove, and add core powder into the U-shaped groove; (3) The U-shaped groove containing the core powder is pressed into a cylindrical shape, compacted by rollers, and then drawn and reduced in diameter by a polycrystalline die to obtain the final welding wire.

4. The method for preparing a high-hardness wear-resistant flux-cored welding wire for open-arc surfacing welding in coal mine machinery according to claim 3, characterized in that, The carbon steel strip has a width of 10-16mm and a thickness of 0.3mm-0.6mm.

5. The method for preparing a high-hardness wear-resistant flux-cored welding wire for open-arc welding in coal mine machinery according to claim 3, characterized in that, The diameter of the welding wire is 1.0-4.0 mm.

6. The method for preparing a high-hardness wear-resistant flux-cored welding wire for open-arc welding in coal mine machinery according to claim 3, characterized in that, The drawing reduction in step (3) is performed 5 times, with each reduction compression rate being 5-20% of the current diameter.

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