600MPa-grade high-toughness ultralow-hydrogen welding rod

Abstract

The invention relates to the technical field of welding materials, and provides a 600MPa-grade high-toughness ultralow-hydrogen welding rod which comprises a core wire and a coating arranged on the surface of the core wire, and the coating is prepared from, by weight, 22-32 parts of marble, 16-24 parts of feldspar, 8-12 parts of fluorite, 10-15 parts of titanium dioxide, 4-8 parts of medium-carbon ferromanganese, 1.2-3.0 parts of low-carbon ferrosilicon and 6-12 parts of titanium sesquioxide. According to the technical scheme, the problems of high weld crack rate and high diffusible hydrogen content in the prior art are solved.

Description

Technical Field

[0001] The invention relates to the technical field of welding materials, and in particular to a 600MPa-grade high-toughness ultra-low hydrogen welding rod. Background Art

[0002] With the rapid development of the national economy, the trend of large-scale steel structure manufacturing has become increasingly obvious, and the strength grade of the steel used is getting higher and higher. In the manufacturing of welded structures such as hydropower, engineering machinery, storage tanks, and submarines, the tensile strength of 600MPa is already the main steel grade. Electrode arc welding still occupies an important proportion in the manufacturing of these structures.

[0003] 600MPa steel has both high strength and toughness, and due to the high alloy content, it also has a certain crack sensitivity. The welding rods supporting 600MPa also require high strength and toughness, and more importantly, strong welding adaptability and low diffusible hydrogen content to reduce crack sensitivity.

[0004] The main technical means to obtain high toughness is to add metal Ni, which can reduce the ductile-brittle transition temperature of the material and improve the toughness of the material. However, Ni is an expensive metal and the cost of adding Ni increases significantly.

[0005] Hydrogen is one of the important factors that cause cold cracks in welds. During the cooling process of welding, hydrogen atoms will diffuse and gather in stress concentration areas or weak parts of the weld. When the hydrogen content reaches a certain level and there is sufficient restraint stress and sensitive metallographic structure at the same time, cold cracks may be caused. Cold cracks usually appear within a period of time after welding, are delayed, and are not easy to be found, so they are potentially very dangerous. This type of crack will seriously reduce the toughness and strength of the weld, making the weld prone to brittle fracture during use, posing a great threat to the safety of the structure. At the same time, too much hydrogen will be dissolved in the lattice of the weld metal, causing the lattice to distort and generate internal stress, thereby reducing the toughness and plasticity of the weld metal. This means that the weld is more likely to break when subjected to dynamic loads such as impact or vibration, reducing the fatigue resistance and reliability of the welded structure. For example, in the welding of some mechanical parts that are subjected to cyclic loads, excessive hydrogen content may cause fatigue cracks in the weld prematurely, shortening the service life of the parts. The main way to reduce the diffusible hydrogen content is to add fluorite (CaF2), using the metallurgical reaction CaF2+2H=Ca+2HF to reduce the hydrogen content in the weld. Although adding fluorite reduces the diffusible hydrogen content, it also deteriorates the operating performance of the welding rod.

[0006] In summary, it is necessary to develop a high-toughness welding rod that does not add precious metal elements such as Ni, reduces the amount of fluorite, and reduces the diffusible hydrogen content and weld crack rate, so as to be suitable for the welding of 600MPa tensile strength grade steel. Summary of the invention

[0007] The present invention provides a 600MPa-grade high-toughness ultra-low hydrogen welding rod, which solves the problems of high weld crack rate and high diffusible hydrogen content in the related art.

[0008] The technical solution of the present invention is as follows: The present invention provides a 600MPa-grade high-toughness ultra-low hydrogen welding rod, comprising a welding core and a coating arranged on the surface of the welding core, wherein the coating raw materials include the following components in parts by weight: 22 to 32 parts of marble, 16 to 24 parts of feldspar, 8 to 12 parts of fluorite, 10 to 15 parts of titanium dioxide, 4 to 8 parts of medium-carbon ferromanganese, 1.2 to 3.0 parts of low-carbon ferrosilicon, and 6 to 12 parts of titanium oxide.

[0009] In the present invention, the low carbon ferrosilicon in the coating contains silicon, which can play a role in solid solution strengthening and deoxidation in the weld. When manganese and silicon exist at the same time, the deoxidation product can float up and the weld metal can be purified. However, too high a silicon content will increase the hardenability of the weld metal. Therefore, only 1.2 to 3.0 parts of low carbon ferrosilicon are needed in the coating formula.

[0010] In the present invention, the medium carbon ferromanganese in the coating contains manganese element, and as the manganese content increases, the yield strength and tensile strength of the weld metal can be greatly improved. However, when the manganese content is too high, the impact toughness of the weld metal will be greatly reduced, so the amount of medium carbon ferromanganese in the coating formula is controlled between 4 and 8 parts. In addition, the carbon in the medium carbon ferromanganese can make up for the burnout of carbon in the welding core.

[0011] In the present invention, marble is added to the coating, and marble is an important gasifier and slag-forming agent in low-hydrogen type welding rods. The sulfur content can be reduced through chemical reaction, which has the effect of improving the impact toughness of weld metal. However, if the marble content is too high, the acid-base balance of the slag will be affected, and the slag removal performance will be deteriorated. Therefore, the amount of marble in the present invention is controlled to be 22-32 parts.

[0012] In the present invention, feldspar is added to the coating, and feldspar is also an important slag-making agent. A certain proportion of feldspar and marble can maintain the acid-base balance of the slag and make the deoxidation and desulfurization products float smoothly. Therefore, the amount of feldspar in the present invention is controlled to be 16-24 parts.

[0013] In the present invention, fluorite is added to the coating, and fluorite is an important dehydrogenation component. In the design of ultra-low hydrogen welding rods, fluorite is added and pre-dried with the coating components to reduce the diffusible hydrogen content to 4-8 mL / 100 g. However, fluorite seriously affects the viscosity of the welding slag, which affects the protective effect of the welding slag on the weld; fluorite also has a negative impact on the health of welding operators. In the present invention, the amount of fluorite is controlled at 8-12 parts, which is about 2 / 3 of the conventional amount, effectively improving the operating performance of the welding rod.

[0014] In the present invention, titanium dioxide is added to the coating, and the titanium dioxide is a molding agent and a plasticizer for the welding rod.

[0015] As a further technical solution, the welding core is H08A welding wire.

[0016] As a further technical solution, the H08A welding wire is composed of the following components in mass percentage: C 0.04%~0.10%, Si ≤0.03%, Mn 0.4%~0.65%, S 0.002%~0.015%, P ≤0.030%, and the balance is iron and inevitable impurities.

[0017] As a further technical solution, according to the test method specified in GB / T 2652-2022 "Transverse tensile test of destructive tests on welds of metallic materials", the tensile strength of the 600MPa grade high-toughness ultra-low hydrogen welding rod is 600~700MPa.

[0018] As a further technical solution, the average particle size of the titanium oxide is 0.5-3 μm.

[0019] In the present invention, the average particle size of titanium oxide is controlled to be 0.5-3 μm. If the particle size exceeds this, the ferrite-inducing effect becomes poor.

[0020] The present invention also proposes a method for preparing a 600MPa grade high-toughness ultra-low hydrogen welding rod, comprising the following steps: S1. Drawing and cutting the H08A welding wire coil to obtain a welding core; S2, mixing the components of the coating raw material with water glass to obtain a coating; S3, press-coating the coating on the welding core, and drying it to obtain a 600MPa grade high-toughness ultra-low hydrogen welding rod.

[0021] As a further technical solution, the welding core has a length of 350-400 mm and a diameter of 3.2-4.0 mm.

[0022] As a further technical solution, the specific gravity of the water glass is 1.67~1.92.

[0023] As a further technical solution, the mass of the water glass is 16% to 24% of the mass of the coating.

[0024] As a further technical solution, the mass ratio of the coating to the welding core is 0.4~0.6:1.

[0025] As a further technical solution, the drying temperature is 370-390° C. and the drying time is 1.5-2.5 hours.

[0026] The working principle and beneficial effects of the present invention are: In the present invention, titanium oxide is added to the coating raw material, and 10wt% to 25wt% of the titanium oxide added to the coating will directly transition to the molten pool. Since the weld metal structure is mainly a mesh of grain boundary ferrite and lath bainite in the crystal, the grain boundary ferrite is very developed, and the network structure becomes a brittle phase. The lath bainite is composed of MA components alternately formed by elongated ferrite and ferrite. The brittle MA component becomes a crack source under impact load, and the ferrite lath forms a fast channel for crack expansion, which greatly reduces the toughness. The titanium oxide transitioned to the molten pool becomes the core of spontaneous nucleation, inhibits the nucleation of grain boundary ferrite, and promotes the rapid nucleation and growth of intracrystalline ferrite. Because titanium oxide is dispersed and distributed, the number is large, and the distance between adjacent titanium oxides is very small, and the adjacent intracrystalline nucleation ferrites intersect with each other to form a closed structure. Titanium oxide makes the effective grain size of the induced precipitated intragranular ferrite very small, limiting the crack extension. Therefore, in the present invention, adding titanium oxide to the coating improves the impact toughness and reduces the crack rate.

[0027] Another function of titanium oxide is to act as a hydrogen trap, hindering the diffusion of hydrogen atoms in the weld, thereby reducing crack sensitivity. Due to the addition of titanium oxide, the diffusible hydrogen content can be reduced to below 4mL / 100g with a smaller amount of fluorite. When the titanium oxide content in the coating raw material is less than 6 parts, the effect of improving toughness and reducing the diffusible hydrogen content is not significant. When the content is greater than 12 parts, a large amount of powder will enter the slag. Therefore, when the present invention controls the titanium oxide content to 6 to 12 parts, the content of diffusible hydrogen is reduced. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the following comparative examples and embodiments, the calcium carbonate content in the marble is 94wt%, and the particle size is 200 mesh, the silicon dioxide content in the feldspar is 84wt%, and the particle size is 200 mesh, the calcium fluoride content in the fluorite is 95wt%, and the particle size is 200 mesh, the titanium dioxide content in the titanium dioxide is 98wt%, and the particle size is 300 mesh, the carbon content in the medium carbon ferromanganese is 2.0wt%, the manganese content is 78wt%, and the silicon content in the ferrosilicon is 75wt%.

[0030] Example 1 A 600MPa grade high-toughness ultra-low hydrogen welding rod, comprising a welding core and a coating arranged on the surface of the welding core, wherein the raw materials of the coating comprise the following components in parts by weight: 24 parts of marble, 21 parts of feldspar, 11 parts of fluorite, 12 parts of titanium dioxide, 5.5 parts of medium carbon ferromanganese, 2.6 parts of low carbon ferrosilicon, and 10 parts of titanium oxide; The welding core is H08A welding wire; H08A welding wire is composed of the following components in mass percentage: C 0.072%, Si 0.02%, Mn 0.52%, S 0.006%, P 0.013%, and the balance is iron and unavoidable impurities; The average particle size of titanium oxide is 1.76 μm; The preparation method of 600MPa grade high toughness ultra-low hydrogen welding rod comprises the following steps: S1. Drawing and cutting the H08A welding wire coil to obtain a welding core; S2, mixing the components of the coating raw material with water glass to obtain a coating; S3, press-coating the coating on the welding core, drying, and obtaining a 600MPa grade high-toughness ultra-low hydrogen welding rod; The length of the welding core is 400mm and the diameter is 4.0mm; The specific gravity of water glass is 1.85; The mass of water glass is 17.5% of the mass of the coating; The mass ratio of coating to welding core is 0.46:1; The drying temperature is 380°C and the time is 2h.

[0031] Example 2 The difference between this embodiment and embodiment 1 is that the raw material of the coating in this embodiment includes the following components by weight: 25 parts of marble, 20 parts of feldspar, 10 parts of fluorite, 11 parts of titanium dioxide, 5.0 parts of medium carbon ferromanganese, 2.2 parts of low carbon ferrosilicon, and 9 parts of titanium trioxide; The average particle size of titanium oxide is 2.65 μm.

[0032] Example 3 The difference between this embodiment and embodiment 1 is that the raw material of the coating in this embodiment includes the following components by weight: 28 parts of marble, 20.5 parts of feldspar, 11.5 parts of fluorite, 9.5 parts of titanium dioxide, 4.8 parts of medium carbon ferromanganese, 2.4 parts of low carbon ferrosilicon, and 11 parts of titanium trioxide; The average particle size of titanium oxide is 2.31 μm.

[0033] Example 4 The difference between this embodiment and embodiment 1 is that the raw material of the coating in this embodiment includes the following components by weight: 23 parts of marble, 17 parts of feldspar, 12 parts of fluorite, 11 parts of titanium dioxide, 5.3 parts of medium carbon ferromanganese, 2.0 parts of low carbon ferrosilicon, and 9 parts of titanium trioxide; The average particle size of titanium oxide is 1.83 μm.

[0034] Example 5 The only difference between this embodiment and embodiment 3 is that the average particle size of titanium oxide in this embodiment is 4.72 μm.

[0035] Example 6 A 600MPa grade high toughness ultra-low hydrogen welding rod, comprising a welding core and a coating arranged on the surface of the welding core, wherein the raw materials of the coating include the following components in parts by weight: 22 parts of marble, 16 parts of feldspar, 8 parts of fluorite, 15 parts of titanium dioxide, 4 parts of medium carbon ferromanganese, 1.2 parts of low carbon ferrosilicon, and 6 parts of titanium trioxide; The welding core is H08A welding wire; H08A welding wire is composed of the following components in mass percentage: C 0.04%, Si 0.03%, Mn 0.4%, S 0.015%, P 0.013%, and the balance is iron and unavoidable impurities; The average particle size of titanium oxide is 0.5 μm; The preparation method of 600MPa grade high toughness ultra-low hydrogen welding rod comprises the following steps: S1. Drawing and cutting the H08A welding wire coil to obtain a welding core; S2, mixing the components of the coating raw material with water glass to obtain a coating; S3, press-coating the coating on the welding core, drying, and obtaining a 600MPa grade high-toughness ultra-low hydrogen welding rod; The length of the welding core is 350mm and the diameter is 3.2mm; The specific gravity of water glass is 1.67; The mass of water glass is 16% of the mass of the coating; The mass ratio of coating to welding core is 0.4:1; The drying temperature is 370°C and the drying time is 2.5 hours.

[0036] Example 7 A 600MPa grade high-toughness ultra-low hydrogen welding rod, comprising a welding core and a coating arranged on the surface of the welding core, wherein the raw materials of the coating comprise the following components in parts by weight: 32 parts of marble, 24 parts of feldspar, 12 parts of fluorite, 15 parts of titanium dioxide, 8 parts of medium carbon ferromanganese, 3 parts of low carbon ferrosilicon, and 12 parts of titanium trioxide; The welding core is H08A welding wire; H08A welding wire is composed of the following components in mass percentage: C 0.1%, Si 0.01%, Mn 0.65%, S 0.002%, P 0.03%, and the balance is iron and unavoidable impurities; The average particle size of titanium oxide is 3 μm; The preparation method of 600MPa grade high toughness ultra-low hydrogen welding rod comprises the following steps: S1. Drawing and cutting the H08A welding wire coil to obtain a welding core; S2, mixing the components of the coating raw material with water glass to obtain a coating; S3, press-coating the coating on the welding core, drying, and obtaining a 600MPa grade high-toughness ultra-low hydrogen welding rod; The length of the welding core is 400mm and the diameter is 4.0mm; The specific gravity of water glass is 1.92; The mass of water glass is 24% of the mass of the coating; The mass ratio of coating to welding core is 0.6:1; The drying temperature is 390°C and the drying time is 2.5h.

[0037] Comparative Example 1 A welding rod, comprising a welding core and a coating arranged on the surface of the welding core, wherein the raw materials of the coating include the following components by weight: 42 parts of marble, 13 parts of feldspar, 19 parts of fluorite, 5 parts of titanium dioxide, 5.0 parts of medium carbon ferromanganese, 2.3 parts of low carbon ferrosilicon, and 2.1 parts of nickel powder; The welding core is H08A welding wire; The method for preparing a welding rod comprises the following steps: S1. Drawing and cutting the H08A welding wire coil to obtain a welding core; S2, mixing the components of the coating raw material with water glass to obtain a coating; S3, applying the coating on the welding core, drying it, and obtaining the welding rod; The length of the welding core is 400mm and the diameter is 4.0mm; The specific gravity of water glass is 1.85; The mass of water glass is 17.5% of the mass of the coating; The mass ratio of coating to welding core is 0.46:1; The drying temperature is 380°C and the time is 2h.

[0038] Comparative Example 2 A welding rod, comprising a welding core and a coating arranged on the surface of the welding core, wherein the raw materials of the coating comprise the following components by weight: 47 parts of marble, 11 parts of feldspar, 22 parts of fluorite, 4.5 parts of titanium dioxide, 4.6 parts of medium carbon ferromanganese, 2.0 parts of low carbon ferrosilicon, and 2.4 parts of nickel powder; The welding core is H08A welding wire; The method for preparing a welding rod comprises the following steps: S1. Drawing and cutting the H08A welding wire coil to obtain a welding core; S2, mixing the components of the coating raw material with water glass to obtain a coating; S3, applying the coating on the welding core, drying it, and obtaining the welding rod; The length of the welding core is 400mm and the diameter is 4.0mm; The specific gravity of water glass is 1.85; The mass of water glass is 17.5% of the mass of the coating; The mass ratio of coating to welding core is 0.48:1; The drying temperature is 380°C and the time is 2h.

[0039] Comparative Example 3 A welding rod, comprising a welding core and a coating arranged on the surface of the welding core, wherein the raw materials of the coating include the following components by weight: 40 parts of marble, 20.5 parts of feldspar, 11.5 parts of fluorite, 9.5 parts of titanium dioxide, 4.8 parts of medium carbon ferromanganese, 2.4 parts of low carbon ferrosilicon, 2.0 parts of ferromolybdenum, and 1.5 parts of nickel powder; The welding core is H08A welding wire; The method for preparing a welding rod comprises the following steps: S1. Drawing and cutting the H08A welding wire coil to obtain a welding core; S2, mixing the components of the coating raw material with water glass to obtain a coating; S3, applying the coating on the welding core, drying it, and obtaining the welding rod; The length of the welding core is 400mm and the diameter is 4.0mm; The specific gravity of water glass is 1.85; The mass of water glass is 17.5% of the mass of the coating; The mass ratio of coating to welding core is 0.5:1; The drying temperature is 380°C and the time is 2h.

[0040] Comparative Example 4 The difference between this comparative example and Example 3 is that titanium trioxide is not added to the medicinal skin raw material in this comparative example.

[0041] Experimental Example 1 The 600MPa grade high toughness ultra-low hydrogen welding rods or welding rods prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were subjected to performance tests, and the test method was as follows: 40mm steel plate was processed into a V-shaped groove, the welding current was 175A, the voltage was 25V, and the welding speed was 130-170mm / min. The deposited metal was tested according to the method specified in CB / T 4364-2013 "Test Method for Oblique Y-shaped Groove Welding Cracks", and the test results are shown in Table 1.

[0042]

[0043] Comparing Examples 1 to 7 with Comparative Examples 1 to 4, it is shown that the addition of titanium oxide to the coating raw material in the present invention reduces the weld crack rate.

[0044] Experimental Example 2 The 600MPa grade high toughness ultra-low hydrogen welding rods or welding rods prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were subjected to performance tests. The test method was as follows: 40mm steel plate was processed into a V-shaped groove, the welding current was 175A, the voltage was 25V, and the welding speed was 130-170mm / min. The yield strength (R p0.2 ), tensile strength (Rm), elongation at break (A), the absorbed energy KV2 at -40°C was tested according to the method specified in GB / T 229-2020 "Method for Charpy pendulum impact test of metallic materials" to characterize the low-temperature impact toughness, and the diffusible hydrogen content was tested according to the method specified in GB / T 3965-2012 "Determination of diffusible hydrogen in deposited metal". The test results are shown in Table 2.

[0045]

[0046] Comparing Examples 1 to 7 with Comparative Examples 1 to 4, it is shown that the addition of titanium oxide to the coating raw material in the present invention reduces the diffusible hydrogen content of the deposited metal, and the 600MPa grade high-toughness ultra-low hydrogen electrode of the present invention is suitable for welding steel with a tensile strength of 600MPa.

[0047] Experimental Example 3 The 600MPa grade high toughness ultra-low hydrogen welding rods or welding rods prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were subjected to performance tests, and the test method was as follows: 40mm steel plates were processed into V-shaped grooves, the welding current was 175A, the voltage was 25V, and the welding speed was 130-170mm / min. The tensile strength (Rm) of the welded joint was tested according to the method specified in GB / T 2651-2023 "Transverse tensile test for destructive tests of metal material welds", and the absorbed energy at -40°C was tested according to the method specified in GB / T 229-2020 "Metallic material Charpy pendulum impact test method" to characterize the low temperature impact toughness. The experimental results are shown in Table 3.

[0048]

[0049] Comparing Examples 1 to 7 with Comparative Examples 1 to 4, it is shown that the addition of titanium oxide with a particle size of 0.5 to 3 μm to the coating raw material in the present invention improves the impact toughness of the weld joint, and the 600 MPa grade high-toughness ultra-low hydrogen welding rod of the present invention is suitable for welding steel with a tensile strength of 600 MPa.

[0050] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A 600MPa grade high toughness ultra-low hydrogen welding rod, characterized in that: It comprises a welding core and a coating arranged on the surface of the welding core, wherein the raw materials of the coating comprise the following components in parts by weight: 22-32 parts of marble, 16-24 parts of feldspar, 8-12 parts of fluorite, 10-15 parts of titanium dioxide, 4-8 parts of medium carbon ferromanganese, 1.2-3.0 parts of low carbon ferrosilicon, and 6-12 parts of titanium oxide.

2. A 600MPa grade high toughness ultra-low hydrogen welding rod according to claim 1, characterized in that: The welding core is H08A welding wire.

3. The 600MPa grade high toughness ultra-low hydrogen welding rod according to claim 1, characterized in that: According to the test method specified in GB / T2652-2022 "Transverse tensile test of destructive tests on welds of metal materials", the tensile strength of the 600MPa grade high-toughness ultra-low hydrogen welding rod is 600~700MPa.

4. The 600MPa grade high toughness ultra-low hydrogen welding rod according to claim 1, characterized in that: The average particle size of the titanium oxide is 0.5-3 μm.

5. The method for preparing a 600MPa grade high toughness ultra-low hydrogen welding electrode according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Drawing and cutting the H08A welding wire coil to obtain a welding core; S2, mixing the components of the coating raw material with water glass to obtain a coating; S3, press-coating the coating on the welding core, and drying it to obtain a 600MPa grade high-toughness ultra-low hydrogen welding rod.

6. The method for preparing a 600MPa grade high toughness ultra-low hydrogen welding electrode according to claim 5, characterized in that: The welding core has a length of 350-400 mm and a diameter of 3.2-4.0 mm.

7. The method for preparing a 600MPa grade high toughness ultra-low hydrogen welding electrode according to claim 5, characterized in that: The specific gravity of the water glass is 1.67-1.

92.

8. The method for preparing a 600MPa grade high toughness ultra-low hydrogen welding electrode according to claim 5, characterized in that: The mass of the water glass is 16% to 24% of the mass of the coating.

9. The method for preparing a 600MPa grade high toughness ultra-low hydrogen welding electrode according to claim 5, characterized in that: The mass ratio of the coating to the welding core is 0.4-0.6:

1.

10. The method for preparing a 600MPa grade high toughness ultra-low hydrogen welding electrode according to claim 5, characterized in that: The drying temperature is 370-390° C. and the drying time is 1.5-2.5 h.

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