Plasma surfacing flux-cored wire resistant to abrasive wear and preparation method of plasma surfacing flux-cored wire

Abstract

The invention relates to a plasma surfacing flux-cored wire resistant to abrasive wear and a preparation method of the plasma surfacing flux-cored wire. The plasma surfacing flux-cored wire comprises an outer skin and a flux core. The flux core comprises the following components in percentage by weight: 1.6 percent to 3.8 percent of C, 0.4 percent to 1.0 percent of Si, 0.4 percent to 1.2 percent of Mn, 2.10 percent to 4.1 percent of B, 15.0 percent to 24.0 percent of Cr, 4.1 percent to 7.2 percent of Nb, 4.3 percent to 7.7 percent of W, 0.1 percent to 0.5 percent of La and the balance of Fe; and the outer skin is a cold-rolled carbon steel strip. The flux-cored wire has the advantages that welding layer metal obtained through plasma surfacing by adopting the flux-cored wire has high comprehensive mechanical properties, the hardness can reach HRC65 or above after surfacing is conducted for 2-3 mm, the flux-cored wire is used for protection of easily-abraded positions of agricultural equipment, and the service life of the agricultural equipment is greatly prolonged.

Description

Technical Field

[0001] The invention belongs to the field of welding materials, and in particular relates to a plasma cladding flux-cored welding wire resistant to abrasive wear and a preparation method thereof. Background Art

[0002] Domestic agricultural machinery is characterized by large usage, various types and low manufacturing precision. Due to the harsh working conditions, agricultural machinery often comes into contact with soil, sand, crop straw, roots, etc. when working in the field, and is subject to severe abrasive wear and a small amount of impact wear. The service life of domestic agricultural machinery is far lower than the international advanced level, and its quality directly affects the working efficiency and reliability of the whole machine.

[0003] High-end agricultural machinery is mainly manufactured abroad. In order to obtain agricultural machinery with high wear resistance and long life, most high-end agricultural machinery equipment manufacturers abroad use surface engineering technology to prepare a wear-resistant layer containing a hard phase on the cutting edge of agricultural machinery cutting tools. The hardness of the surfacing green forage knife alloy layer produced by John Deere using surfacing technology is HRC60~HRC65, and it has achieved good results in actual use. Silage machines and green forage harvesting machinery produced by companies such as Bellota, New Holland and Lely Storm use cladding technology to form a WC carbide layer on the cutting edge of the cutter blade. Compared with the mature surface engineering technology used abroad to strengthen the cutting edge of agricultural machinery tools, there is still a large gap between domestic related research and foreign countries. Summary of the invention

[0004] The purpose of the present invention is to provide a plasma surfacing flux-cored welding wire resistant to abrasive wear and a preparation method thereof, so as to improve the wear resistance of the surfacing layer, and when the formed plasma surfacing layer is subjected to external abrasive wear and rolling, it is not easy to cause micro-flaking and reduce the wear resistance. The flux-cored welding wire can form a surfacing layer containing hard phases such as WC, NbC, Fe2B, etc. on the surface of agricultural machinery or parts with fast wear, so that the surfacing layer has excellent abrasive wear resistance and a certain ability to resist low stress impact.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A plasma cladding flux-cored welding wire resistant to abrasive wear, comprising an outer sheath and a flux core;

[0007] The drug core comprises by weight percentage

[0008] C: 1.6% ~ 3.8%, Si: 0.4% ~ 1.0%, Mn: 0.4% ~ 1.2%, B: 2.10% -4.1%, Cr: 15.0% ~ 24.0%, Nb: 4.1% ~ 7.2%, W: 4.3% ~ 7.7%, La: 0.1% ~ 0.5%, the rest is Fe;

[0009] The outer skin is a cold-rolled carbon steel strip.

[0010] In the flux core, C comes from one or more of graphite, micro-carbon ferrochrome, high-carbon ferrochrome, chromium carbide, and cold-rolled carbon steel strip; Si comes from ferrosilicon FeSi75; Mn comes from electrolytic manganese; Cr comes from one or more of high-carbon ferrochrome FeCr68C8, micro-carbon ferrochrome, and chromium carbide; Nb comes from ferroniobium powder; W comes from tungsten carbide; B comes from ferroboron; La comes from nano La2O3 powder;

[0011] The C content in the graphite is greater than 99.0wt%; the Si content in ferrosilicon FeSi75 is 72.0wt% to 78.0wt%; the Mn content in electrolytic manganese is more than 99.9wt%;

[0012] The high carbon ferrochrome FeCr68C8 contains 65.0wt% to 69.0wt% Cr and 8.0wt% to 9.0wt% C; the low carbon ferrochrome contains 65.0wt% to 69.0wt% Cr and 0.01wt% to 0.05wt% C; the chromium carbide contains 88.0wt% to 92.0wt% Cr and 9.0wt% to 11.0wt% C;

[0013] The Nb content in the ferroniobium powder is more than 65.0wt%; the W content in the tungsten carbide is more than 95.0wt%; the B content in the ferroboron is more than 19.3wt%; and the La2O3 content in the nano La2O3 powder is more than 99.9wt%.

[0014] The particle size of the micro-carbon ferrochrome, high-carbon ferrochrome and chromium carbide powder is less than 380um; the particle size of the electrolytic manganese, ferroboron, ferroniobium, ferrosilicon FeSi75 and micro-carbon ferrochrome powder is less than 250um.

[0015] The diameter of the flux-cored welding wire is 1.2-2.8 mm.

[0016] A method for preparing a plasma cladding flux-cored welding wire resistant to abrasive wear comprises the following steps:

[0017] 1) The raw material powders are mixed evenly in a powder mixer, and then placed in a vacuum heating furnace for heating and drying to obtain a mixed core powder;

[0018] 2) rolling a cold-rolled carbon steel strip into a U-shaped groove, and then adding 26% to 50% of the mixed flux core powder of the total weight of the flux cored welding wire into the U-shaped groove; closing the U-shaped groove to wrap the flux core therein, and finally obtaining a flux cored welding wire with a diameter of 1.2 to 2.8 mm by drawing and reducing the diameter one by one.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The plasma surfacing flux-cored welding wire reinforced with multiple wear-resistant particles prepared by the method of the present invention, under the high temperature of plasma surfacing, multiple alloying elements such as Cr, W, B, Nb and carbon in the flux core form multiple carbides, generating network-distributed M7C3 carbides and dispersed fine MC carbides, giving full play to the effects of dispersion strengthening and fine grain strengthening; boron elements and alloying elements can form granular or lath-shaped boron-containing strengthening phases such as M2B and Fe3 (C, B), playing the role of precipitation strengthening. Carbides, borides and carborides work together to improve the wear resistance of the surfacing layer. Rare earth oxide La2O3 promotes heterogeneous nucleation and refines primary M7C3 carbides, so that when the organizational structure is subjected to external abrasive wear and rolling, it is not easy to cause micro-flaking and reduce wear resistance.

[0021] 2. The outer skin of the flux-cored welding wire is a cold-rolled carbon steel strip coated with powder. In order to achieve the composition of the final metal coating, flux cores and welding skins with different compositions are used, so that the final prepared coating can meet the design requirements and the composition is easy to adjust. The powder used in the present invention is mechanically ground powder, which is low in price and highly economical.

[0022] 3. The weld metal obtained by plasma surfacing with the flux-cored welding wire exhibits high comprehensive mechanical properties. After surfacing 4mm, the hardness can reach HRC65 or above. According to the ASTM-G65 dry sand rubber wheel abrasive wear test, the weight loss of the wear-resistant layer does not exceed 0.02g. It is used to protect the easily worn parts of agricultural machinery and tools, greatly improving the service life of agricultural machinery and tools. In addition, during the process of entering the soil, the agricultural machinery and tools are protected by single-sided surfacing, and the unprotected surface wears quickly, resulting in self-sharpening, which further improves the performance of agricultural machinery and tools. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the microstructure diagram of the flux-cored wire after plasma surfacing in Example 1.

[0024] Figure 2 This is the microstructure diagram of the flux-cored wire after plasma surfacing in Example 2.

[0025] Figure 3 This is the microstructure diagram of the flux-cored wire after plasma surfacing in Example 3. DETAILED DESCRIPTION

[0026] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0027] A plasma cladding flux-cored welding wire resistant to abrasive wear comprises an outer skin and a flux core; the flux core comprises C: 3.6% to 5.4%, Si: 0.9% to 1.2%, Mn: 1.0% to 1.8%, B: 2.10%-4.1%, Cr: 40.0% to 52.0%, Nb: 4.1% to 7.2%, W: 4.3% to 7.7%, La: 0.1% to 0.5%, and the rest is Fe. The outer skin is an SPCC steel strip. The diameter of the flux-cored welding wire is 1.2 to 2.8 mm.

[0028] In the flux core, C comes from one or more of graphite, low-carbon ferrochrome, high-carbon ferrochrome, and chromium carbide; Si comes from ferrosilicon FeSi75; Mn comes from electrolytic manganese; Cr comes from one or more of high-carbon ferrochrome FeCr68C8, low-carbon ferrochrome, and chromium carbide; Nb comes from ferroniobium powder; W comes from tungsten carbide; B comes from ferroboron; and La comes from nano-La2O3 powder.

[0029] The C content in graphite is greater than 99.0%; the Si content in ferrosilicon FeSi75 is 72.0% to 78.0%; the Mn content in electrolytic manganese is more than 99.9%. The Cr content in high-carbon ferrochrome FeCr68C8 is 65.0% to 69.0%, and the C content is 8.0% to 9.0%; the Cr content in micro-carbon ferrochrome is 65.0% to 69.0%, and the C content is 0.01 to 0.05%; the Cr content in chromium carbide is 88.0% to 92.0%, and the C content is 9.0 to 11.0%. The Nb content in ferroniobium powder is more than 65.0%; the W content in tungsten carbide is more than 95.0wt%; the B content in ferroboron is more than 19.3%; the La2O3 content in nano La2O3 powder is more than 99.9%.

[0030] Among them, micro-carbon ferrochrome, high-carbon ferrochrome, chromium carbide, and reduced iron powder pass through a 40-mesh sieve, and the powder particle size is ≤380um. Metallic chromium, FeSi75, silicon carbide, electrolytic manganese, ferroniobium, and boron carbide pass through a 60-mesh sieve, and the powder particle size is ≤250um. The particle size of tungsten carbide and graphite is ≤75um. The particle size of lanthanum oxide is ≤500nm.

[0031] A method for preparing a plasma cladding flux-cored welding wire resistant to abrasive wear comprises the following steps:

[0032] 1) The raw material powders are mixed evenly in a powder mixer (mixing time is 30 to 120 minutes), and then placed in a vacuum heating furnace for heating and drying (heating temperature is 200 to 400° C., time is 60 to 180 minutes) to obtain a mixed core powder;

[0033] 2) rolling a cold-rolled carbon steel strip into a U-shaped groove, and then adding 26% to 50% of the mixed flux core powder of the total weight of the flux cored welding wire into the U-shaped groove; closing the U-shaped groove to wrap the flux core therein, and finally obtaining a flux cored welding wire with a diameter of 1.2 to 2.8 mm by drawing and reducing the diameter one by one.

[0034] In the process of plasma surfacing with the flux-cored welding wire, argon gas protection is adopted, the surfacing current is 155-165A, the welding gun travel speed is 100-150mm / min, and the ion gas flow rate is 1.5-2L / min.

[0035] The flux-cored welding wire can be used for both plasma cladding and laser cladding, and has wide applications and strong applicability. The flux-cored welding wire is resistant to abrasive wear and can resist low stress impact.

[0036] Example 1

[0037] See Figure 1 A method for preparing a plasma cladding flux-cored welding wire resistant to abrasive wear comprises the following steps:

[0038] Step 1: Weigh the powder, 3.6g of low carbon ferrochrome, 76.4g of high carbon ferrochrome, 50g of chromium carbide, 90g of metallic chromium, FeSi75

[0039] 0.4g, silicon carbide 4.6g, electrolytic manganese 5g, ferroniobium 76g, boron carbide 30g, tungsten carbide 60g, graphite 1g, lanthanum oxide 3g, the above components total 400g.

[0040] Step 2: Mix the powder and place it in a powder mixer for 30 minutes.

[0041] Step 3: Dry the powder. Place the weighed powder in a heating furnace and heat it to 300°C for 120 minutes to remove moisture from the powder.

[0042] Step 4: Filling the powder, select a cold-rolled carbon steel strip (such as SPCC steel strip) with a thickness of 0.3mm and a width of 10mm as the outer skin, use alcohol to remove the grease on the surface of the outer skin, and bend the outer skin into a U shape, fill the powder obtained in step 3 into the outer skin, the powder filling amount is 40%, and then close the outer skin.

[0043] Step 5: Drawing the welding wire: The drawing process is used to make the finished welding wire. The diameter of the wear-resistant flux-cored welding wire is 2.4 mm.

[0044] Step 6: Prepare The flux-cored welding wire is welded on the Q235 steel plate with a plasma cladding machine, with a thickness of more than 4 mm, and air-cooled to room temperature.

[0045] The hardness of the surfacing layer is 65.3HRC. The ASTM G65 friction and wear dry sand rubber wheel testing machine is used for friction and wear test. The contact form of the friction pair is line contact. The rubber wheel has a diameter of 178mm, a width of 10mm, and a hardness of 60 Shore. The load is 130N, the speed of the rubber wheel is 200r / min (the linear speed is 1.68m / s), and the abrasive flow rate is 340-360g / min. The test duration is 3000 revolutions of the rubber wheel. The mass loss of the sample before and after wear is weighed using an analytical balance with an accuracy of 0.1mg. The wear loss of the surfacing layer is 0.0169g.

[0046] Example 2

[0047] See Figure 2 A method for preparing a plasma cladding flux-cored welding wire resistant to abrasive wear comprises the following steps:

[0048] Step 1: Weigh the powder, 67.1g of low carbon ferrochrome, 108.5g of high carbon ferrochrome, 54.6g of chromium carbide, 63g of metallic chromium, FeSi75

[0049] 1.6g, silicon carbide 1.2g, electrolytic manganese 4.0g, ferroniobium 74g, boron carbide 53g, tungsten carbide 68g, graphite 3.0g, lanthanum oxide 2.0g, the above components total 500g.

[0050] Step 2: Mix the powder and place it in a powder mixer for 30 minutes.

[0051] Step 3: Dry the powder. Place the weighed powder in a heating furnace and heat it to 300°C for 120 minutes to remove moisture from the powder.

[0052] Step 4: Filling with powder, select a cold-rolled carbon steel strip with a thickness of 0.3mm and a width of 10mm as the outer skin, use alcohol to remove the grease on the surface of the outer skin, and bend the outer skin into a U shape, fill the powder obtained in step 3 into the outer skin, the powder filling amount is 50%, and then close the outer skin.

[0053] Step 5: Drawing the welding wire: the welding wire is made into a finished product by a drawing process. The diameter of the wear-resistant flux-cored welding wire is 2.8 mm.

[0054] Step 6: Prepare The flux-cored welding wire was overlay-welded on the Q235 steel plate with a plasma overlay welding machine, with a thickness of >4 mm, and air-cooled to room temperature.

[0055] Example 3

[0056] See Figure 3 A method for preparing a plasma cladding flux-cored welding wire resistant to abrasive wear comprises the following steps:

[0057] Step 1: Weigh the powder, 42g of low-carbon ferrochrome, 77g of high-carbon ferrochrome, 25g of chromium carbide, 40g of metallic chromium, 752.0g of FeSi, 1.0g of silicon carbide, 2.3g of electrolytic manganese, 66g of ferroniobium, 44g of boron carbide, 48g of tungsten carbide, 1.0g of graphite, and 1.7g of lanthanum oxide, totaling 350g of the above components.

[0058] Step 2: Mix the powder and place it in a powder mixer for 30 minutes.

[0059] Step 3: Dry the powder. Place the weighed powder in a heating furnace and heat it to 300°C for 120 minutes to remove moisture from the powder.

[0060] Step 4: Filling with powder, select a cold-rolled carbon steel strip with a thickness of 0.3mm and a width of 10mm as the outer skin, use alcohol to remove the grease on the surface of the outer skin, and bend the outer skin into a U shape, fill the powder obtained in step 3 into the outer skin, the powder filling amount is 35%, and then close the outer skin.

[0061] Step 5: Drawing the welding wire: The welding wire is made into a finished product by a drawing process. The diameter of the wear-resistant flux-cored welding wire is 1.6 mm.

[0062] Step 6: Prepare The flux-cored welding wire is welded on the Q235 steel plate with a plasma cladding machine, with a thickness of more than 4 mm, and air-cooled to room temperature.

[0063] Example 4

[0064] A method for preparing a plasma cladding flux-cored welding wire resistant to abrasive wear comprises the following steps:

[0065] Step 1: Weigh the powder, 68g of low carbon ferrochrome, 55.8g of high carbon ferrochrome, 145g of chromium carbide, 21g of metallic chromium, FeSi75

[0066] 2.0g, silicon carbide 1.5g, electrolytic manganese 4.4g, ferroniobium 72g, boron carbide 28g, tungsten carbide 76g, graphite 3.5g, lanthanum oxide 2.8g, the above components total 480g.

[0067] Step 2: Mix the powder and place it in a powder mixer for 30 minutes.

[0068] Step 3: Dry the powder. Place the weighed powder in a heating furnace and heat it to 300°C for 120 minutes to remove moisture from the powder.

[0069] Step 4: Filling with powder, select a cold-rolled carbon steel strip with a thickness of 0.3mm and a width of 10mm as the outer skin, use alcohol to remove the grease on the surface of the outer skin, and bend the outer skin into a U shape, fill the powder obtained in step 3 into the outer skin, the powder filling amount is 48%, and then close the outer skin.

[0070] Step 5: Drawing the welding wire: the welding wire is made into a finished product by a drawing process. The diameter of the wear-resistant flux-cored welding wire is 2.8 mm.

[0071] Step 6: Prepare The flux-cored welding wire is welded on the Q235 steel plate with a plasma cladding machine, with a thickness of more than 4 mm, and air-cooled to room temperature.

[0072] Example 5

[0073] A method for preparing a plasma cladding flux-cored welding wire resistant to abrasive wear comprises the following steps:

[0074] Step 1: Weigh the powder, 126.5g of low carbon ferrochrome, 42g of high carbon ferrochrome, 34g of chromium carbide, 18g of metallic chromium, FeSi75

[0075] 1.8g, silicon carbide 1.5g, electrolytic manganese 5.0g, ferroniobium 92g, boron carbide 53.5g, tungsten carbide 81.5g, graphite 2.0g, lanthanum oxide 2.2g, the above components total 460g.

[0076] Step 2: Mix the powder and place it in a powder mixer for 30 minutes.

[0077] Step 3: Dry the powder. Place the weighed powder in a heating furnace and heat it to 300°C for 120 minutes to remove moisture from the powder.

[0078] Step 4: Filling with powder, select a cold-rolled carbon steel strip with a thickness of 0.3mm and a width of 10mm as the outer skin, use alcohol to remove the grease on the surface of the outer skin, and bend the outer skin into a U shape, fill the powder obtained in step 3 into the outer skin, the powder filling amount is 46%, and then close the outer skin.

[0079] Step 5: Drawing the welding wire: the welding wire is made into a finished product by a drawing process. The diameter of the wear-resistant flux-cored welding wire is 2.8 mm.

[0080] Step 6: Prepare The flux-cored welding wire is welded on the Q235 steel plate with a plasma cladding machine, with a thickness of more than 4 mm, and air-cooled to room temperature.

[0081] Example 6

[0082] A method for preparing a plasma cladding flux-cored welding wire resistant to abrasive wear comprises the following steps:

[0083] Step 1: Weigh the powder, 220g of low carbon ferrochrome, 59g of high carbon ferrochrome, 35.4g of chromium carbide, 15g of metallic chromium, FeSi75

[0084] 2.1g, silicon carbide 1.5g, electrolytic manganese 5.0g, ferroniobium 68g, boron carbide 32g, tungsten carbide 48g, graphite 2.0g, lanthanum oxide 2.0g, the above components total 490g.

[0085] Step 2: Mix the powder and place it in a powder mixer for 30 minutes.

[0086] Step 3: Dry the powder. Place the weighed powder in a heating furnace and heat it to 300°C for 120 minutes to remove moisture from the powder.

[0087] Step 4: Filling with powder, select a cold-rolled carbon steel strip with a thickness of 0.3mm and a width of 10mm as the outer skin, use alcohol to remove the grease on the surface of the outer skin, and bend the outer skin into a U shape, fill the powder obtained in step 3 into the outer skin, the powder filling amount is 49%, and then close the outer skin.

[0088] Step 5: Drawing the welding wire: the welding wire is made into a finished product by a drawing process. The diameter of the wear-resistant flux-cored welding wire is 2.8 mm.

[0089] Step 6: Prepare The flux-cored welding wire is welded on the Q235 steel plate with a plasma cladding machine, with a thickness of more than 4 mm, and air-cooled to room temperature.

[0090] The solder layer properties are shown in Table 1.

[0091] Table 1

[0092] Hardness / HRC ASTM G65 abrasion loss / g Example 1 65.3 0.0169 Example 2 69.1 0.0056 Example 3 66.1 0.0136 Example 4 67.9 0.0112 Example 5 67.4 0.0104 Example 6 66.5 0.0143

[0093] The flux-cored welding wire prepared by the present invention has a certain resistance to low-stress impact, and adopts plasma surfacing technology to obtain surface-reinforced agricultural machinery and implements, and surfacing or cladding is performed on the parts with fast wear and then strengthened, which has the advantages of low cost, good wear resistance, simple process and the like.

Claims

1. A plasma cladding flux-cored welding wire resistant to abrasive wear, characterized in that: including a sheath and a core; The drug core comprises by weight percentage C: 1.6% ~ 3.8%, Si: 0.4% ~ 1.0%, Mn: 0.4% ~ 1.2%, B: 2.10% -4.1%, Cr: 15.0% ~ 24.0%, Nb: 4.1% ~ 7.2%, W: 4.3% ~ 7.7%, La: 0.1% ~ 0.5%, the rest is Fe; The outer skin is a cold-rolled carbon steel strip.

2. The abrasive wear resistant plasma cladding flux-cored welding wire according to claim 1, characterized in that: In the flux core, C comes from one or more of graphite, micro-carbon ferrochrome, high-carbon ferrochrome, chromium carbide, and cold-rolled carbon steel strip; Si comes from ferrosilicon FeSi75; Mn comes from electrolytic manganese; Cr comes from one or more of high-carbon ferrochrome FeCr68C8, micro-carbon ferrochrome, and chromium carbide; Nb comes from ferroniobium powder; W comes from tungsten carbide; B comes from ferroboron; La comes from nano La2O3 powder; The C content in the graphite is greater than 99.0wt%; the Si content in ferrosilicon FeSi75 is 72.0wt% to 78.0wt%; the Mn content in electrolytic manganese is more than 99.9wt%; The high carbon ferrochrome FeCr68C8 contains 65.0wt% to 69.0wt% Cr and 8.0wt% to 9.0wt% C; the low carbon ferrochrome contains 65.0wt% to 69.0wt% Cr and 0.01wt% to 0.05wt% C; the chromium carbide contains 88.0wt% to 92.0wt% Cr and 9.0wt% to 11.0wt% C; The Nb content in the ferroniobium powder is more than 65.0wt%; the W content in the tungsten carbide is more than 95.0wt%; the B content in the ferroboron is more than 19.3wt%; and the La2O3 content in the nano La2O3 powder is more than 99.9wt%.

3. The abrasive wear resistant plasma cladding flux-cored welding wire according to claim 2, characterized in that: The particle size of the micro-carbon ferrochrome, high-carbon ferrochrome and chromium carbide powder is less than 380um; the particle size of the powder of electrolytic manganese, ferroboron, ferroniobium, ferrosilicon FeSi75 and micro-carbon ferrochrome is less than 250um.

4. The abrasive wear resistant plasma cladding flux-cored welding wire according to claim 1, characterized in that: The diameter of the flux-cored welding wire is 1.2-2.8 mm.

5. A method for preparing abrasive wear resistant plasma cladding flux-cored welding wire according to any one of claims 1 to 4, characterized in that: The following steps are involved: 1) The raw material powders are mixed evenly in a powder mixer, and then placed in a vacuum heating furnace for heating and drying to obtain a mixed core powder; 2) rolling a cold-rolled carbon steel strip into a U-shaped groove, and then adding 26% to 50% of the mixed flux core powder of the total weight of the flux cored welding wire into the U-shaped groove; closing the U-shaped groove to wrap the flux core therein, and finally obtaining a flux cored welding wire with a diameter of 1.2 to 2.8 mm by drawing and reducing the diameter one by one.

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