An easy-to-remove slag iron-based coated welding rod for multi-layer and multi-pass welding

Abstract

The present invention belongs to the technical field of welding materials, specifically an easy-to-remove slag iron-based coated welding rod for multi-layer and multi-pass welding. It comprises an iron-based welding core, a coating and an epoxy resin film, the coating is coated around the welding section of the iron-based welding core, and the epoxy resin film is coated on the outer surface of the coating. The components of the epoxy resin film include, by mass percentage: 20%-25% nickel sulfide particles treated with a coupling agent, 5%-8% nano-silicon powder treated with a coupling agent, 8%-12% nano-manganese powder treated with a coupling agent, 6%-8% curing agent, and the balance is epoxy resin. The particle size of the nickel sulfide particles is 20μm-30μm, and the thickness of the epoxy resin film is 40μm-80μm. The coated welding rod of the present invention has a stable arc during welding, a high slag removal rate after welding, and good mechanical properties of the obtained weld, which is suitable for multi-layer and multi-pass welding. The present invention is an innovation in coated welding rods.

Description

Technical Field

[0001] The invention belongs to the technical field of welding materials, in particular to an easy-to-remove slag iron-based coated welding rod for multi-layer and multi-pass welding. Background Art

[0002] Coated welding rods generally consist of a metal core and a coating. The coating is applied evenly and centripetally to the core. The core is typically a metal wire of a specific length and diameter. During welding, the wire conducts the welding current, generating an arc between the workpiece and the rod tip, converting electrical energy into heat. Furthermore, the wire itself melts, becoming filler metal and fusing with the liquid base metal to form the weld. Currently, the most widely used in industrial production are iron-based coated welding rods, meaning the core wire is primarily composed of iron. For filler welding with wide and deep grooves, multi-pass welding is required. After each pass, the slag covering the weld metal must be removed before proceeding to the next step. However, with conventional iron-based coated welding rods, the slag is difficult to remove after welding, and some residue remains on the weld surface. If the next layer is welded in this situation, defects such as slag inclusions can be introduced into the deposited metal, seriously affecting the mechanical properties of the weld.

[0003] In order to solve the above technical problems, technicians in this field have carried out corresponding scientific research work, especially in the composition of the drug cover, and have made many technical improvements and researches.

[0004] During welding, the electrode coating is first broken into small pieces by the heat and force of the arc and enters the molten pool. Because the welding arc is a mobile heat source, only a part of the coating that is broken into small pieces and enters the molten pool is completely melted, while the other part does not have time to completely melt (but its surface can melt) and combines with other substances to form slag. Therefore, the unmelted part of the coating is not evenly distributed in the slag (causing the unmelted coating components in the slag to be distributed very unevenly, which is an important reason for the difficulty in slag removal).

[0005] Chinese patent 202110513202.6 discloses a welding rod with high slag coverage and easy slag removal after welding (application date May 11, 2021). It adopts a scheme of adding scandium fluoride to the flux coating, and takes advantage of the property of scandium fluoride to shrink when heated and expand when cooled, so the slag formed after welding is easier to remove. The existing problems are as follows: ① Scandium fluoride, which has the property of thermal contraction and cold expansion, is the main substance of this invention, but it exists in the flux coating. During welding, part of the flux coating melts but the other part does not melt. The unmelted part is not evenly distributed in the formed slag, but falls off in blocks into the molten pool without time to disperse (only the surface part melts), and quickly solidifies to form slag. Therefore, the distribution of scandium fluoride in the slag is not uniform, resulting in some slag being easy to slag off and some slag being difficult to slag off; ② Part of scandium fluoride decomposes during arc burning, and the generated fluoride ions are extremely detrimental to arc burning, the welding arc is unstable, and the weld quality is poor; ③ Experiments have shown that the thermal contraction and cold expansion effect of scandium fluoride is not obvious, and the effect on the improvement of slag removal is small, and it cannot fully meet the requirements of multi-layer and multi-pass welding.

[0006] Chinese patent 201710489158.3 discloses a stainless steel welding rod that is spatter-resistant and easy to remove slag (application date June 24, 2017). The invention employs a method of spraying a coating dispersion onto the surface of the welding rod base with a spray gun, and then spraying certain substances that can generate nano-cryolith onto the welding rod base, effectively improving the material's properties of being prone to spattering and difficult to remove slag during welding. However, there are the following problems: ① The cryolite used has the chemical formula Na3AlF6, which decomposes and produces a large amount of HF gas. The fluorine ions generated under the action of the arc are extremely detrimental to arc combustion, resulting in unstable welding arcs and poor weld quality. ② Experiments show that the bond formed between the oxide and the slag on the weld surface is slightly loose, but it still cannot change the incomplete slag removal condition, which can easily cause defects such as slag inclusions in the deposited metal. In other words, the addition of nano-cryolith cannot improve the slag removal performance to meet the requirements of multi-layer and multi-pass welding.

[0007] How to solve the above problems is an urgent task for scientific and technological personnel in this field. Summary of the Invention

[0008] The purpose of the present invention is to provide an iron-based coated welding rod with easy slag removal for multi-layer and multi-pass welding, which solves the following technical problems: how to make the arc burning of the welding rod stable during welding, evenly distribute the substances that are easy to remove slag in the formed slag, and significantly improve the slag removal performance.

[0009] The present invention adopts the following technical solutions:

[0010] A slag-removable iron-based coated welding rod for multi-layer and multi-pass welding comprises an iron-based welding core, a flux coating and an epoxy resin film. The iron-based welding core comprises a flux coating section and a welding clamp clamping section. The flux coating is coated around the flux coating section of the iron-based welding core, and the epoxy resin film is coated on the outer surface of the flux coating.

[0011] The ingredients and mass ratio of the coating are: 30-40 parts of titanium dioxide, 18-22 parts of calcium carbonate, 10-15 parts of silicon dioxide, 10-15 parts of potassium feldspar, 10-12 parts of mica, 12-15 parts of ferromanganese, and 5-8 parts of ferrotitanium.

[0012] The epoxy resin film comprises, by mass percentage, 20%-25% nickel sulfide particles treated with a coupling agent, 5%-8% nano silicon powder treated with a coupling agent, 8%-12% nano manganese powder treated with a coupling agent, 6%-8% curing agent, and the remainder being epoxy resin.

[0013] The particle size of the nickel sulfide particles is 20 μm-30 μm.

[0014] The particle size of the nano-silicon is 60nm-80nm, and the particle size of the nano-manganese is 60nm-80nm.

[0015] The coupling agent is any one of silane coupling agent KH-560 and silane coupling agent KH-570.

[0016] The curing agent is any one of cardanol-modified phenolic amine, phthalic anhydride, and the like.

[0017] The epoxy resin film has a thickness of 40 μm-80 μm.

[0018] The steps for preparing an easily slag-removable iron-based coated welding rod for multi-layer and multi-pass welding of the present invention are as follows:

[0019] Prepare an iron-based coated welding rod using conventional methods → spray the prepared epoxy resin emulsion onto the surface of the prepared welding rod coating using a spray gun at 5MPa-8MPa → allow to cure for 20-24 hours → dry at 80-90°C for 2-2.5 hours → allow to cool to room temperature. The preparation process of the epoxy resin emulsion is as follows:

[0020] 1) Pretreatment of nickel sulfide particles: nickel sulfide particles and a coupling agent are mixed in a ratio (mass ratio) of 1: (1.5-3), anhydrous ethanol equal to the mass of the nickel sulfide particles is added, and the mixture is magnetically stirred for 36-48 hours, filtered, and vacuum dried at 70°C-80°C for 12-18 hours.

[0021] 2) Pretreatment of nano-silicon powder: Mix the nano-silicon powder and the coupling agent in a ratio of 1: (1.5-3) (mass ratio), add anhydrous ethanol equal to the mass of the nano-silicon powder, stir magnetically for 36h-48h, filter, and vacuum dry at 70℃-80℃ for 12h-18h.

[0022] 3) Pretreatment of nano-manganese powder: nano-manganese powder and coupling agent are mixed in a ratio of 1: (1.5-3) (mass ratio), anhydrous ethanol equal to the mass of nano-manganese powder is added, and after magnetic stirring for 36h-48h, the mixture is filtered and vacuum dried at 70℃-80℃ for 12h-18h.

[0023] 4) Prepare the diluent: mix xylene and n-butanol in a volume ratio of (4-5):1.

[0024] 5) Preparing an intermediate emulsion: adding the diluent prepared in 4) to the epoxy resin, wherein the mass of the diluent is 110%-125% of the mass of the epoxy resin, and mechanically stirring the mixture until uniform.

[0025] 6) The pretreated nickel sulfide particles, nano silicon powder and nano manganese powder prepared in 1), 2) and 3) are added to the intermediate emulsion prepared in 5) and mechanically stirred until uniform.

[0026] 7) Add a curing agent to the emulsion prepared in 6) and stir mechanically to obtain the desired epoxy resin emulsion.

[0027] The present invention has the following beneficial technical effects:

[0028] The present invention sprays an epoxy resin film (containing nickel sulfide particles, nano manganese powder, and nano silicon powder) on the surface of the fluorine-free coating:

[0029] 1) Because nickel sulfide particles, nano-silicon, and manganese nanoparticles are present in the epoxy resin that wraps the electrode coating, they can all enter the molten pool and melt. Since welding is a process in which the heat source moves rapidly, part of the nickel sulfide particles that enter the molten pool decompose and part do not have time to decompose. However, because the two parts are in the coating state and melted by heat before entering the molten pool, the two parts of the sulfide are evenly dispersed. The decomposed nickel sulfide generates nickel atoms and sulfur atoms, and the sulfur reacts with nano-silicon / manganese to generate nano-silicon sulfide / nano-manganese sulfide particles. The other part of the nickel sulfide particles that have not had time to decompose (the particle size is 20μm-30μm, and this particle size range is very conducive to the generation of loose slag. Experiments have shown that the effect of nickel sulfide particles outside this particle size range on generating loose slag is not significant and is not easy to remove slag), nano-silicon sulfide particles, nano-manganese sulfide particles, combined with the product of the coating reaction, directly form slag. The nickel sulfide in the slag is evenly distributed and has a strong thermal contraction and cold expansion property. The nano-scale silicon sulfide and nano-scale manganese sulfide generated by the reaction are very conducive to the flow and floating of the slag, and avoid the formation of spinel-type structured compounds. The slag removal rate after welding can reach 100%, which is beneficial to multi-layer and multi-pass welding.

[0030] 2) During the welding process, no fluorine ions harmful to the arc are generated, and the arc burns stably.

[0031] 3) The nickel produced by the decomposition of nickel sulfide can alloy the weld metal and effectively improve its overall performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The main cross-sectional view of an easily removable iron-based coated electrode for multi-layer and multi-pass welding;

[0033] Figure 2 It is along Figure 1 Sectional view along line AA.

[0034] In the figure: 1. Iron-based welding core; 1-1. Welding section; 1-2. Welding clamp holding section; 2. Coating; 3. Epoxy resin film. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0036] like Figure 1 and Figure 2 As shown, a slag-removable iron-based coated welding rod for multi-layer and multi-pass welding includes an iron-based welding core 1, a flux coating 2 and an epoxy resin film 3. The iron-based welding core 1 includes a flux coating section 1-1 and a welding clamp clamping section 1-2. The flux coating 2 is coated around the flux coating section 1-1 of the iron-based welding core 1, and the epoxy resin film 3 is coated on the outer surface of the flux coating 2.

[0037] The ingredients and mass ratio of the coating 2 are: 30-40 parts of titanium dioxide, 18-22 parts of calcium carbonate, 10-15 parts of silicon dioxide, 10-15 parts of potassium feldspar, 10-12 parts of mica, 12-15 parts of ferromanganese, and 5-8 parts of ferrotitanium.

[0038] The epoxy resin film 3 comprises, by mass percentage, 20%-25% nickel sulfide particles treated with a coupling agent, 5%-8% nano silicon powder treated with a coupling agent, 8%-12% nano manganese powder treated with a coupling agent, 6%-8% curing agent, and the remainder being epoxy resin.

[0039] The particle size of the nickel sulfide particles is 20 μm-30 μm.

[0040] The particle size of nano-silicon is 60nm-80nm, and the particle size of nano-manganese is 60nm-80nm.

[0041] The coupling agent is any one of silane coupling agent KH-560 and silane coupling agent KH-570.

[0042] The curing agent is any one of cardanol-modified phenalkamine, phthalic anhydride, and the like.

[0043] The thickness of the epoxy resin film 3 is 40 μm to 80 μm.

[0044] Examples and Comparative Examples

[0045] (1) In all the following examples and comparative examples, the welding rods used were from the same batch of J422 welding rods with a diameter of 4.0 mm, and were dried before the epoxy resin film was prepared on their surfaces.

[0046] (2) In all the following examples and comparative examples, the epoxy resin emulsion was prepared according to the following steps:

[0047] 1) Pretreatment of nickel sulfide particles: nickel sulfide particles and a coupling agent are mixed in a ratio (mass ratio) of 1: (1.5-3), anhydrous ethanol equal to the mass of the nickel sulfide particles is added, and the mixture is magnetically stirred for 36-48 hours, filtered, and vacuum dried at 70°C-80°C for 12-18 hours.

[0048] 2) Pretreatment of nano-silicon powder: Mix the nano-silicon powder and the coupling agent in a ratio of 1: (1.5-3) (mass ratio), add anhydrous ethanol equal to the mass of the nano-silicon powder, stir magnetically for 36h-48h, filter, and vacuum dry at 70℃-80℃ for 12h-18h.

[0049] 3) Pretreatment of nano-manganese powder: nano-manganese powder and coupling agent are mixed in a ratio of 1: (1.5-3) (mass ratio), anhydrous ethanol equal to the mass of nano-manganese powder is added, and after magnetic stirring for 36h-48h, the mixture is filtered and vacuum dried at 70℃-80℃ for 12h-18h.

[0050] 4) Prepare diluent: mix xylene and n-butanol in a volume ratio of (4-5):1.

[0051] 5) Preparing epoxy resin emulsion: adding the diluent prepared in 4) to the epoxy resin, wherein the mass of the diluent is 110%-125% of the mass of the epoxy resin, and mechanically stirring the mixture to obtain a uniform mixture.

[0052] 6) The pretreated nickel sulfide particles, nano-silicon powder and nano-manganese powder prepared in 1), 2) and 3) are added to the emulsion prepared in 5), and mechanically stirred until uniform.

[0053] 7) Add a curing agent to the emulsion prepared in 6) and stir mechanically to obtain the desired epoxy resin emulsion.

[0054] (3) In all the following examples and comparative examples, the preparation method of the easily slag-removable iron-based coated welding rod for multi-layer and multi-pass welding is as follows:

[0055] Prepare an iron-based coated welding rod according to the conventional method → ​​spray the prepared epoxy resin emulsion onto the coating surface of the prepared welding rod with a spray gun at 5MPa-8MPa → let it stand and cure for 20h-24h → dry at 120℃-130℃ for 2h-2.5h → let it stand and cool to room temperature.

[0056] (4) In all the following embodiments and comparative examples, a multi-layer multi-pass butt welding test was conducted on a Q345 steel plate with a thickness of 20 mm, with a V-shaped groove. The number of layers was 4, and the number of weld passes in each layer from bottom to top was 1, 2, 4, and 7, respectively. After the weld was cooled, the slag removal rate was tested according to formula 3-1 in the "Welding Materials Handbook" (Edited by Long Weimin and Chen Yong, ISBN978-7-111-46777-9, Machinery Industry Press, July 2014), and the tensile strength of the deposited metal was experimentally determined according to GB / T 2652-2008 "Tensile Test Methods for Welds and Deposited Metals".

[0057] Example 1

[0058] (1) An iron-based coated welding rod was prepared according to a conventional method (the composition and mass ratio of the coating were: 35 parts of titanium dioxide, 20 parts of calcium carbonate, 12 parts of silicon dioxide, 12 parts of potassium feldspar, 11 parts of mica, 12 parts of ferromanganese, and 6 parts of ferrotitanium) and dried at a temperature of 150°C-180°C for 1.5 hours.

[0059] (2) preparing an epoxy resin emulsion, the composition and weight percentage of which are as follows: 20% nickel sulfide particles (particle size of 20 μm-30 μm) treated with silane coupling agent KH-570, 5% nano silicon powder treated with silane coupling agent KH-570, 8% nano manganese powder treated with silane coupling agent KH-570, 6% cardanol-modified phenalkamine, and the remainder being epoxy resin.

[0060] (3) Take out the welding rod dried in the oven and cool it to 100℃-110℃.

[0061] (4) Spray the prepared epoxy resin emulsion onto the coating surface of the welding rod using a spray gun at 5 MPa-8 MPa.

[0062] (5) Let the above welding rod stand and solidify for 20h-24h

[0063] (6) Dry at 80-90°C for 2h-2.5h.

[0064] (7) Let it cool to room temperature.

[0065] Example 2

[0066] (1) An iron-based coated welding rod was prepared according to a conventional method (the composition and mass ratio of the coating were: 35 parts of titanium dioxide, 20 parts of calcium carbonate, 12 parts of silicon dioxide, 12 parts of potassium feldspar, 11 parts of mica, 12 parts of ferromanganese, and 6 parts of ferrotitanium) and dried at a temperature of 150°C-180°C for 1.5 hours.

[0067] (2) preparing an epoxy resin emulsion, the composition and weight percentage of which are as follows: 25% nickel sulfide particles treated with silane coupling agent KH-570, 8% nano silicon powder treated with silane coupling agent KH-570, 12% nano manganese powder treated with silane coupling agent KH-570, 8% cardanol-modified phenalkamine, and the remainder being epoxy resin.

[0068] (3) Take out the welding rod dried in the oven and cool it to 100℃-110℃.

[0069] (4) Spray the prepared epoxy resin emulsion onto the coating surface of the welding rod using a spray gun at 5 MPa-8 MPa.

[0070] (5) Let the above welding rod stand and solidify for 20h-24h

[0071] (6) Dry at 80-90°C for 2h-2.5h.

[0072] (7) Let it cool to room temperature.

[0073] Example 3

[0074] (1) An iron-based coated welding rod was prepared according to a conventional method (the composition and mass ratio of the coating were: 35 parts of titanium dioxide, 20 parts of calcium carbonate, 12 parts of silicon dioxide, 12 parts of potassium feldspar, 11 parts of mica, 12 parts of ferromanganese, and 6 parts of ferrotitanium) and dried at a temperature of 150°C-180°C for 1.5 hours.

[0075] (2) preparing an epoxy resin emulsion, the components and weight percentages of which are as follows: 22% nickel sulfide particles treated with silane coupling agent KH-570, 7% nano silicon powder treated with silane coupling agent KH-570, 10% nano manganese powder treated with silane coupling agent KH-570, 7% cardanol-modified phenalkamine, and the remainder being epoxy resin.

[0076] (3) Take out the welding rod dried in the oven and cool it to 100℃-110℃.

[0077] (4) Spray the prepared epoxy resin emulsion onto the coating surface of the welding rod using a spray gun at 5 MPa-8 MPa.

[0078] (5) Let the above welding rod stand and solidify for 20h-24h

[0079] (6) Dry at 80-90°C for 2h-2.5h.

[0080] (7) Let it cool to room temperature.

[0081] Comparative Example 1

[0082] An iron-based coated welding rod was prepared using conventional methods. The coating contained Type A powder and Type B powder in an A:B ratio of 11:4 (mass ratio). The Type A powder consisted of 35 parts titanium dioxide, 20 parts calcium carbonate, 12 parts silicon dioxide, 12 parts potassium feldspar, 11 parts mica, 12 parts ferromanganese, and 6 parts ferrotitanium. The Type B powder consisted of 20 parts nickel sulfide particles (20-30 μm in diameter), 5 parts nano-silicon powder, and 8 parts nano-manganese powder. The electrodes were then dried at 150-180°C for 1.5 hours.

[0083] Comparative Example 2

[0084] The method is basically the same as Example 3, except that (2) is as follows: preparing an epoxy resin emulsion, 7% of nano-silicon powder treated with silane coupling agent KH-570, 10% of nano-manganese powder treated with silane coupling agent KH-570, 7% of cardanol-modified phenolic amine, and the balance being epoxy resin.

[0085] Comparative Example 3

[0086] The method is basically the same as Example 3, except that (2) is as follows: preparing an epoxy resin emulsion, 22% of nickel sulfide particles (particle size less than 20 μm) treated with a silane coupling agent KH-570, 7% of nano-silicon powder treated with a silane coupling agent KH-570, 10% of nano-manganese powder treated with a silane coupling agent KH-570, 7% of cardanol-modified phenalkamine, and the balance being epoxy resin.

[0087] Comparative Example 4

[0088] The method is basically the same as Example 3, except that (2) is as follows: preparing an epoxy resin emulsion, 22% of nickel sulfide particles (particle size greater than 30 μm) treated with a silane coupling agent KH-570, 7% of nano-silicon powder treated with a silane coupling agent KH-570, 10% of nano-manganese powder treated with a silane coupling agent KH-570, 7% of cardanol-modified phenalkamine, and the balance being epoxy resin.

[0089] Comparative Example 5

[0090] The method is basically the same as Example 3, except that (2) is as follows: preparing an epoxy resin emulsion, 22% cryolite particles treated with silane coupling agent KH-570, 7% nano-silicon powder treated with silane coupling agent KH-570, 10% nano-manganese powder treated with silane coupling agent KH-570, 7% cardanol-modified phenalkamine, and the balance being epoxy resin.

[0091] Comparative Example 6

[0092] The method is basically the same as Example 3, except that (2) is as follows: preparing an epoxy resin emulsion, 22% of scandium fluoride treated with a silane coupling agent KH-570, 7% of nano-silicon powder treated with a silane coupling agent KH-570, 10% of nano-manganese powder treated with a silane coupling agent KH-570, 7% of cardanol-modified phenalkamine, and the balance being epoxy resin.

[0093] Comparative Example 7

[0094] The method is basically the same as Example 3, except that (2) is as follows: preparing epoxy resin emulsion, using 22% nickel sulfide particles treated with silane coupling agent KH-570, 7% cardanol-modified phenolic amine, and the balance being epoxy resin.

[0095] Comparative Example 8

[0096] The method is basically the same as Example 3, except that (2) is as follows: preparing an epoxy resin emulsion, 22% nickel sulfide particles treated with silane coupling agent KH-570, 7% nano-silicon powder treated with silane coupling agent KH-570, 7% cardanol-modified phenolic amine, and the balance being epoxy resin.

[0097] Comparative Example 9

[0098] The method is basically the same as Example 3, except that (2) is as follows: preparing an epoxy resin emulsion, 22% nickel sulfide particles treated with silane coupling agent KH-570, 10% nano manganese powder treated with silane coupling agent KH-570, 7% cardanol-modified phenolic amine, and the balance being epoxy resin.

[0099] Example 10

[0100] The method is basically the same as Example 3, except that (2) is as follows: preparing an epoxy resin emulsion, 20% of nickel sulfide particles treated with silane coupling agent KH-570, 5% of micron-sized silicon powder treated with silane coupling agent KH-570, 8% of micron-sized manganese powder treated with silane coupling agent KH-570, 6% of cardanol-modified phenolic amine, and the balance being epoxy resin.

[0101] Comparative Example 11

[0102] An iron-based coated welding rod was prepared according to a conventional method (the composition and mass ratio of the coating were: 35 parts of titanium dioxide, 20 parts of calcium carbonate, 12 parts of silicon dioxide, 12 parts of potassium feldspar, 11 parts of mica, 12 parts of ferromanganese, and 6 parts of ferrotitanium) and dried at a temperature of 150°C-180°C for 1.5 hours.

[0103] The evaluation results of Examples 1-3 and Comparative Examples 1-11 are shown in Table 1.

[0104] Table 1

[0105] project Arc stability Slag removal rate (%) Tensile strength (MPa) Example 1 excellent 100 462 Example 2 excellent 100 485 Example 3 excellent 100 476 Comparative Example 1 excellent 90 443 Comparative Example 2 excellent 91 440 Comparative Example 3 excellent 90 438 Comparative Example 4 excellent 65 409 Comparative Example 5 Difference 72 401 Comparative Example 6 Difference 90 426 Comparative Example 7 excellent 97 385 Comparative Example 8 excellent 98 439 Comparative Example 9 excellent 98 451 Comparative Example 10 excellent 82 425 Comparative Example 11 excellent 78 426

[0106] From the above comparative examples, it can be seen that in the epoxy resin film:

[0107] 1. Nickel sulfide, nano-silicon powder and nano-manganese powder were mixed into the coating (Comparative Example 1). The welding arc was stable, but the slag removal rate was low and the tensile strength was poor. This shows that the slag removal effect was poor when the above substances were present in the coating, which in turn affected the tensile strength.

[0108] 2. Without nickel sulfide (Comparative Example 2), the welding arc is stable, but the slag removal rate is low and the tensile strength is poor, indicating that nickel sulfide has a great influence on the slag removal property, thereby affecting the tensile strength.

[0109] 3. The nickel sulfide with a particle size of 20μm-30μm is replaced with nickel sulfide with a particle size less than 20μm or a particle size greater than 30μm (Comparative Example 3, Comparative Example 4). The welding arc is stable, but the slag removal rate is low and the tensile strength is poor. This shows that the nickel sulfide particle size less than 20μm or the particle size greater than 30μm has little effect on the slag removal after welding. Only by controlling the nickel sulfide particle size within the range of 20μm-30μm can excellent slag removal be guaranteed.

[0110] 4. When nickel sulfide is replaced with cryolite (Comparative Example 5), the welding arc is unstable, the slag removal rate is low, and the tensile strength is poor; this indicates that cryolite (fluoride ions are formed during welding) affects the stability of the welding arc and the slag removal performance.

[0111] 5. When nickel sulfide is replaced with scandium fluoride (Comparative Example 6), the welding arc is unstable, the slag removal rate is low, and the tensile strength is poor; this indicates that scandium fluoride (fluoride ions formed during welding) affects the stability and slag removal of the welding arc, but the slag removal rate can reach 90%, which has certain benefits for post-weld slag removal but cannot meet the requirements of multi-layer and multi-pass welding.

[0112] 6. Without nano-silicon powder and nano-manganese powder (Comparative Example 7), the welding arc is stable, the slag removal rate is high, and the tensile strength is extremely poor; this shows that although simply adding nickel sulfide can effectively improve the slag removal rate, it is very unfavorable to the tensile strength if desulfurization treatment is not performed.

[0113] 7. Only one of nano-silicon powder or nano-manganese powder (Comparative Example 8, Comparative Example 9) has a stable welding arc, a high slag removal rate, and poor tensile strength; this shows that although the addition of nickel sulfide can effectively improve the slag removal rate, if only nano-silicon powder or only nano-manganese powder is used for desulfurization treatment, the effect is not good and is not conducive to tensile strength. Only the combined desulfurization of the two can achieve better results.

[0114] 8. When using micron-sized silicon and micron-sized manganese for desulfurization (Comparative Example 10), the welding arc is stable, the slag removal rate is low, and the tensile strength is poor; this indicates that the slag generated by micron-sized silicon and micron-sized manganese is not easy to remove, and the desulfurization effect is poor, which is detrimental to the tensile strength.

[0115] 9. The conventional method for preparing iron-based coated welding rods (without epoxy resin film) has a poor slag removal rate (Comparative Example 11), is prone to slag inclusion defects during multi-layer and multi-pass welding, and has low tensile strength.

[0116] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of the present invention. Any equivalent changes or modifications made in accordance with the spirit and essence of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. An easily detachable iron-based coated welding rod for multi-layer and multi-pass welding, characterized by: The invention comprises an iron-based welding core (1), a flux coating (2) and an epoxy resin film (3), wherein the iron-based welding core (1) comprises a flux coating section (1-1) and a welding clamp holding section (1-2), the flux coating (2) is coated around the flux coating section (1-1) of the iron-based welding core (1), and the epoxy resin film (3) is coated on the outer surface of the flux coating (2); The composition and mass ratio of the coating (2) are: 30-40 parts of titanium dioxide, 18-22 parts of calcium carbonate, 10-15 parts of silicon dioxide, 10-15 parts of potassium feldspar, 10-12 parts of mica, 12-15 parts of ferromanganese, and 5-8 parts of ferrotitanium; The epoxy resin film (3) comprises, by mass percentage, 20%-25% of nickel sulfide particles treated with a coupling agent, 5%-8% of nano silicon powder treated with a coupling agent, 8%-12% of nano manganese powder treated with a coupling agent, 6%-8% of a curing agent, and the remainder being epoxy resin; The particle size of the nickel sulfide particles is 20 μm-30 μm; The epoxy resin film (3) has a thickness of 40 μm-80 μm.

2. The easily detachable slag iron-based coated welding rod for multi-layer and multi-pass welding according to claim 1, characterized in that: The particle size of the nano silicon powder is 60nm-80nm, and the particle size of the nano manganese powder is 60nm-80nm.

3. The easily detachable slag iron-based coated welding rod for multi-layer and multi-pass welding according to claim 1, characterized in that: The coupling agent is any one of silane coupling agent KH-560 and silane coupling agent KH-570.

4. The easily detachable slag iron-based coated welding rod for multi-layer and multi-pass welding according to any one of claims 1 to 3, characterized in that: The curing agent is any one of cardanol-modified phenolic amine and phthalic anhydride.

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