High-porosity-resistance nickel-based welding rod and preparation method and application thereof

Abstract

The invention belongs to the technical field of welding materials, and particularly provides a high-porosity-resistance nickel-based welding rod which comprises a core wire and a coating wrapping the surface of the core wire. The coating comprises 12-16 parts of fluorite, 10-15 parts of marble, 4-6 parts of rutile, 2-4 parts of aluminum oxide, 3-6 parts of sodium fluoride, 2-4 parts of aluminum fluoride, 0.5-1 part of sodium carbonate, 0.5-1 part of CMC, 26-30 parts of chromium metal, 3-5 parts of molybdenum powder, 4.5-7 parts of ferroniobium, 6-9 parts of medium carbon ferromanganese, 2-4 parts of rare earth ferrosilicon, 1-4 parts of ferrotitanium and 6-12 parts of iron powder. When an alternating current power supply is adopted for welding, a good welding process is achieved during horizontal, transverse, vertical and pitching positions, no tail red exists, deslagging is easy, the tensile strength of deposited metal of the welding rod ranges from 640 MPa to 790 MPa, the yield strength is larger than or equal to 400 MPa, the ductility is larger than or equal to 35%, the impact toughness at the temperature of minus 196 DEG C is larger than or equal to 70, and the welding rod has excellent low-temperature toughness.

Description

Technical Field

[0001] The present invention belongs to the technical field of welding materials, and particularly relates to a nickel-based electrode with high porosity resistance, a preparation method thereof, and an application thereof. Background Art

[0002] Liquefied Natural Gas (LNG) is liquid natural gas formed by purification and liquefaction processes, with methane as the main component. At normal pressure, the volume of LNG is approximately 1 / 600 of its gaseous volume under standard conditions, and its temperature is around -162.5°C. LNG producers usually store the product in LNG cryogenic storage tanks. The main material used for manufacturing LNG storage tanks is 9% Ni steel. 9% Ni steel is a medium-carbon martensitic low-alloy steel with low alloying degree, low price, and excellent cryogenic properties. It is the only Ni-rich steel that can be used under cryogenic conditions and has been widely used in China for manufacturing LNG infrastructure such as LNG ships, LNG storage tanks, and LNG pipelines. The welding methods for 9% Ni steel mainly include: submerged arc automatic welding (SAW), shielded metal arc welding (SMAW), and gas tungsten arc welding (GTAW), among which shielded metal arc welding is the most widely used.

[0003] Welding of 9% Ni steel usually uses high-nickel welding materials. Due to the high content of Ni element in the deposited metal, on the one hand, liquid nickel can dissolve a large amount of H2, O2, and CO gases, and on the other hand, the poor fluidity and fast solidification of the weld metal caused by the high nickel content are likely to lead to a rapid decrease in the solubility of the weld metal during the condensation period, resulting in porosity and hydrogen embrittlement. In engineering applications, especially when welding butt joints, needle-shaped pores that are difficult to detect easily occur in the weld, and on-site construction can only solve the porosity problem by grinding and repair welding. Therefore, improving the porosity resistance of nickel-based electrodes and solving the porosity problem during the welding process of nickel-based electrodes can reduce the labor intensity of welding and improve the welding efficiency. Summary of the Invention

[0004] The object of the present invention is to overcome the problem that existing nickel-based electrodes are prone to cause porosity during the welding process, increasing the welding labor intensity.

[0005] To this end, the present invention provides a nickel-based electrode with high porosity resistance, including a welding core and a coating wrapped on the surface of the welding core. By weight fraction, the coating includes 12 - 16 parts of fluorite, 10 - 15 parts of marble, 4 - 6 parts of rutile, 2 - 4 parts of alumina, 3 - 6 parts of sodium fluoride, 2 - 4 parts of aluminum fluoride, 0.5 - 1 part of soda ash, 0.5 - 1 part of CMC, 26 - 30 parts of metal chromium, 3 - 5 parts of molybdenum powder, 4.5 - 7 parts of ferroniobium, 6 - 9 parts of medium-carbon ferromanganese, 2 - 4 parts of rare earth ferrosilicon, 1 - 4 parts of ferrotitanium, and 6 - 12 parts of iron powder.

[0006] Specifically, the composition of the welding core is as follows: C ≤ 0.03 wt%, Mn ≤ 0.05 wt%, Si (0.15 - 0.30) wt%, P ≤ 0.002 wt%, S ≤ 0.003 wt%, Ni ≥ 99.5 wt%, Ti (0.02 - 0.04) wt%, and the rest are inevitable impurities.

[0007] Specifically, by mass percentage, the proportion of the coating in the above nickel-based welding electrode is 30 - 35%.

[0008] The present invention also provides a method for preparing the above nickel-based welding electrode with high porosity resistance, which includes the following steps: stirring and mixing the coating powder evenly; adding a binder to the evenly mixed powder, stirring, and then coating it on the welding core; baking to obtain the nickel-based welding electrode.

[0009] Specifically, the above binder is potassium-sodium water glass.

[0010] Specifically, the concentration of the above potassium-sodium water glass is 42°Be〞 - 43°Be〞, and the addition amount is 200 ml / kg based on the mass of the coating powder.

[0011] Specifically, after adding the binder to the evenly mixed powder and stirring, it is fed into a welding electrode extrusion coater and coated on the welding core under a pressure of 12 - 16 MPa.

[0012] Specifically, the above baking process is: baking at 100 - 120°C for 2 hours and at 240 - 250°C for 2 hours. Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0013] The nickel-based welding electrode with high porosity resistance provided by the present invention meets the GB / T 13814 ENi6133 technical conditions. The welding electrode uses an alternating current power source for welding, has excellent porosity resistance, solves the porosity problem in the welding process of nickel-based welding electrodes, can reduce the labor intensity of welding, and improve the welding efficiency. The all-position welding process performance of this welding electrode is good, there is no tail red during welding, and slag removal is easy. The tensile strength of the deposited metal of the welding electrode

[0014] ≥550 MPa, the yield strength ≥ 360 MPa, the elongation ≥ 22%, and it has excellent low-temperature toughness at -196°C.

[0015] The following will further elaborate on the present invention in conjunction with the accompanying drawings. Description of the Drawings

[0016] Figure 1 is the cross-sectional view of the drawn bar in Example 1 of the present invention.

[0017] Figure 2 is the cross-sectional view of the drawn bar in Comparative Example 1 of the present invention.

[0018] Figure 3It is the bending specimen diagram of Embodiment 1 of the present invention.

[0019] Figure 4 It is the bending specimen diagram of Comparative Example 1 of the present invention. Detailed implementation manners

[0020] The technical solutions in the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Although the representative embodiments of the present invention have been described in detail, those of ordinary skill in the technical field to which the present invention pertains will understand that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be defined by the appended claims and their equivalents.

[0021] The present invention provides a nickel-based electrode with high anti-pore property, including a welding core and a coating wrapped on the surface of the welding core. By weight fraction, the coating includes 12-16 parts of fluorite, 10-15 parts of marble, 4-6 parts of rutile, 2-4 parts of alumina, 3-6 parts of sodium fluoride, 2-4 parts of aluminum fluoride, 0.5-1 part of soda ash, 0.5-1 part of CMC, 26-30 parts of metal chromium, 3-5 parts of molybdenum powder, 4.5-7 parts of ferroniobium, 6-9 parts of medium-carbon ferromanganese, 2-4 parts of rare-earth ferrosilicon, 1-4 parts of ferrotitanium, and 6-12 parts of iron powder. By mass percentage, the proportion of the coating in the nickel-based electrode is preferably 30-35%.

[0022] Fluorite: The fluorides in fluorite can reduce the surface tension of the liquid metal, lower the viscosity of the liquid metal, thereby increasing its air permeability and improving the anti-pore performance; at the same time, it adjusts the melting point of the slag. When the fluorite content is lower than 9wt%, the anti-pore ability is insufficient, and extremely small needle-shaped pores are likely to appear in the weld. When the fluorite content is higher than 16wt%, the slag removal becomes poor.

[0023] Marble: Its main functions are to generate gas and slag, protect the weld from being oxidized and nitrided by air; in addition, it keeps the weld metal at a high alkalinity, reduces the impurity content, and is beneficial to making the weld metal obtain more excellent properties. At the same time, marble has an obvious arc stabilizing effect and can also increase the fluidity of the slag, and has an obvious effect on improving the spreading of the slag.

[0024] Rutile: Its main functions are to generate slag, refine the molten droplets, improve the arc stability, and improve the weld formation. When its content is lower than 4wt%, the effect of improving the arc stability is not obvious. When its content is higher than 6wt%, the slag is not easy to spread, affecting the slag removal.

[0025] Alumina: Its main function is to generate slag and adjust the slag alkalinity, so that the slag alkalinity does not increase excessively in this fluoride slag system, achieving the purpose of improving the slag fluidity.

[0026] Sodium fluoride: Its main functions are dehydrogenation, adjusting the melting point of the slag, and reducing the viscosity of the liquid metal. When its content exceeds 6wt%, it has an adverse effect on the arc stability.

[0027] Aluminum fluoride: Its main functions are dehydrogenation and adjusting the melting point of the slag. In the present invention, through the combined action with sodium fluoride, the dehydrogenation effect is better.

[0028] Soda ash: It has a lubricating effect, improves the extrusion coating performance of the electrode, and makes the surface of the electrode smooth and beautiful.

[0029] CMC (carboxymethyl cellulose): It is a plasticizer, increasing the viscosity of the coating and improving the extrusion coating performance of the electrode.

[0030] Chromium metal: It transfers chromium element to the weld metal to meet the requirements of the chemical composition of the deposited metal. It makes the weld have excellent corrosion resistance, but too high chromium content will affect the toughness of the weld.

[0031] Molybdenum powder: It transfers molybdenum element to the weld metal to meet the requirements of the chemical composition of the deposited metal. Molybdenum can significantly improve the strength and hardness of the weld metal, but too high content will also affect the toughness of the weld metal.

[0032] Ferroniobium: It transfers niobium element to the weld to meet the requirements of the chemical composition of the deposited metal. Nb is a strong carbide-forming element, which can form stable NbC and improve the intergranular corrosion resistance. During the welding process, a small amount of Nb is oxidized to NbO, which forms spinel oxide with Cr2O3 and affects slag removal. Therefore, a small amount of strong deoxidizer also needs to be added to the coating to reduce the generation of NbO and Cr2O3 and improve the slag removal performance.

[0033] Medium-carbon ferromanganese: It deoxidizes and desulfurizes, transfers Mn element and carbon element to the weld metal to meet the requirements of the chemical composition of the deposited metal, and improves the strength of the weld metal through the C element.

[0034] Rare earth ferrosilicon: It deoxidizes and transfers Si element to the weld metal. The rare earth can also purify the weld, inhibit the liquid crack of the deposited metal, and improve the crack resistance. However, when the addition amount is higher than 4%, with the increase of the Si element, it significantly makes slag removal difficult.

[0035] Ferrotitanium: It is a strong deoxidizer, deoxidizing and denitrifying, reducing pores while reducing the production of spinel oxide and improving the slag removal performance. Ferrotitanium can also improve the arc stability.

[0036] The welding core used in the present invention is a special welding core, and the coating adopts the fluoride type (CaF 2Type) basic slag system. The fluoride slag system has excellent fluidity and gas permeability, which is extremely beneficial to improving the spreading of basic molten slag and the anti-porosity performance. Through the combination of components with specific contents in the coating, it has excellent all-position operation performance and slag removal performance. To improve the extrusion performance of the electrode, a small amount of soda ash is added to the coating to increase the lubricity of the coating.

[0037] Since the resistivity of the alloy steel core is higher than that of the pure nickel welding core, the phenomenon of tail red is likely to occur during welding. Usually, when only one-third of the electrode remains, it is already completely tail red. The resistivity of the pure nickel welding core is lower than that of the alloy welding core, which can effectively improve the tail red. Therefore, on the basis of the pure nickel welding core, in order to improve the process performance of the electrode, the composition of the welding core is redesigned. The welding core components are as follows:

[0038] C: 0.01wt%, Mn: 0.01wt%, Si: 0.01wt%, P: 0.001wt%, S: 0.001wt%, Ni: 99.6wt%. Si: 0.23wt%, Ti: 0.025wt%.

[0039] Adding Si element to the welding core can improve the fluidity of the liquid metal and has an obvious improvement effect on the weld formation. When adding alloys through the coating, it is easy to cause difficult slag removal; when adding in the welding core, it can not only play the role of transitional alloy, but also improve the fluidity of the liquid metal and has no influence on slag removal;

[0040] Adding Ti element to the welding core can refine the weld metal and is obviously beneficial to improving and stabilizing the low-temperature impact toughness.

[0041] Adding Si and Ti elements on the basis of the pure nickel welding core has an obvious effect on improving the fluidity of the molten pool and the anti-porosity performance.

[0042] The present invention also provides a preparation method of the above nickel-based electrode, including the following steps:

[0043] (1) Stir the coating powder and mix it evenly;

[0044] (2) Add K2Na1 water glass with a concentration of 42°Be〞 - 43°Be〞 to the evenly mixed powder at an addition amount of 200 ml / kg, stir for 15 - 30 minutes, and after stirring, send it into the electrode extrusion machine and coat it on the welding core at a pressure of 12 - 16 MPa;

[0045] (3) The extruded electrode is baked at 100 - 120°C for 2 hours, 240 - 250°C for 2 hours, and finally baked at a high temperature of 420°C for 1 - 2 hours to obtain the nickel-based electrode.

[0046] Next, the effect of the high anti-porosity nickel-based electrode of the present invention is studied through specific examples.

[0047] Example 1:

[0048] This example provides a nickel-based electrode with high porosity resistance. The composition of the coating powder is shown in Table 1, and the welding core is a pure nickel welding core. The welding cores used in each example are from the same batch with the same chemical composition, as shown in Table 2, and the coating ratio is 35%. The preparation method is as follows:

[0049] (1) Stir the coating powder and mix it evenly;

[0050] (2) Add K2Na1 water glass with a concentration of 43°Be〞 at an addition amount of 200 ml / kg to the evenly mixed powder and stir for 30 minutes. After stirring, feed it into the electrode extrusion machine and coat it on the welding core at a pressure of 14 MPa;

[0051] (3) The coated electrode is baked at 100°C for 2 hours, 240°C for 2 hours, and finally baked at a high temperature of 420°C for 2 hours to obtain the electrode.

[0052] Example 2:

[0053] This example provides a nickel-based electrode with high porosity resistance. The composition of the coating powder is shown in Table 1, and the welding core is a pure nickel welding core, with the composition shown in Table 2, and the coating ratio is 34%. The preparation method is as follows:

[0054] (1) Stir the coating powder and mix it evenly;

[0055] (2) Add K2Na1 water glass with a concentration of 43°Be〞 at an addition amount of 200 ml / kg to the evenly mixed powder and stir for 30 minutes. After stirring, feed it into the electrode extrusion machine and coat it on the welding core at a pressure of 16 MPa;

[0056] (3) The coated electrode is baked at 120°C for 2 hours, 250°C for 2 hours, and finally baked at a high temperature of 420°C for 2 hours to obtain the electrode.

[0057] Example 3:

[0058] This example provides a nickel-based electrode with high porosity resistance. The composition of the coating powder is shown in Table 1, and the welding core is a pure nickel welding core, with the composition shown in Table 2, and the coating ratio is 35%. The preparation method is as follows:

[0059] (1) Stir the coating powder and mix it evenly;

[0060] (2) Add potassium sodium silicate with a concentration of 43°Be〞 to the uniformly mixed powder at an addition rate of 200 ml / kg, stir for 30 minutes, and after stirring, feed it into a welding electrode extrusion machine and coat it on the welding core under a pressure of 15 MPa;

[0061] (3) The coated welding electrode is baked at 120°C for 2 hours, 250°C for 2 hours, and finally baked at a high temperature of 420°C for 2 hours to obtain the welding electrode.

[0062] Example 4:

[0063] This example provides a nickel-based welding electrode with high porosity resistance. The composition of the coating powder is shown in Table 1, the welding core is a pure nickel welding core, the composition is shown in Table 2, and the coating ratio is 34%. The preparation method is as follows:

[0064] (1) Stir the coating powder and mix it evenly;

[0065] (2) Add potassium sodium silicate with a concentration of 43°Be〞 to the uniformly mixed powder at an addition rate of 200 ml / kg, stir for 30 minutes, and after stirring, feed it into a welding electrode extrusion machine and coat it on the welding core under a pressure of 14 MPa;

[0066] (3) The coated welding electrode is baked at 120°C for 2 hours, 250°C for 2 hours, and finally baked at a high temperature of 420°C for 2 hours to obtain the welding electrode.

[0067] Example 5:

[0068] This example provides a nickel-based welding electrode with high porosity resistance. The composition of the coating powder is shown in Table 1, the welding core is a pure nickel welding core, the composition is shown in Table 2, and the coating ratio is 33%. The preparation method is as follows:

[0069] (1) Stir the coating powder and mix it evenly;

[0070] (2) Add potassium sodium silicate with a concentration of 43°Be〞 to the uniformly mixed powder at an addition rate of 200 ml / kg, stir for 30 minutes, and after stirring, feed it into a welding electrode extrusion machine and coat it on the welding core under a pressure of 14 MPa;

[0071] (3) The coated welding electrode is baked at 120°C for 2 hours, 250°C for 2 hours, and finally baked at a high temperature of 420°C for 2 hours to obtain the welding electrode.

[0072] Table 1 Composition of coating powder for each example (parts)

[0073]

[0074]

[0075] Table 2 Chemical Composition of Welding Core for Each Example (mass percentage %)

[0076] C Mn Si P S Ni Ti Impurity Example 0.01 0.01 0.23 0.001 0.001 99.6 0.025 0.123

[0077] Comparative Example 1:

[0078] This comparative example provides a nickel-based welding electrode. The composition of the coating powder, the proportion of the coating, and the preparation scheme are the same as those in Example 1, except that the chemical composition of its welding core is shown in Table 3.

[0079] Table 3 Chemical Composition of Welding Core for Comparative Example (mass percentage %)

[0080] C Mn P S Ni Impurity Example 0.01 0.01 0.001 0.001 99.7 0.278

[0081] Example 6:

[0082] The nickel-based welding electrodes prepared in Examples 1-5 and Comparative Example 1 were subjected to physical and chemical property tests on the deposited metal. The groove, dimensions, sampling method, and position of the test plate were carried out in accordance with the Chinese national standard GB / T 13814 "Nickel and Nickel Alloy Welding Electrodes". The welding operation was carried out using an AC straight polarity power supply. The welding core diameter was 3.2 mm, the welding current was 110-120 A, and the welding speed was 26.0 cm / min. The chemical composition of the deposited metal of the welding electrodes prepared in each example is shown in Table 4, the mechanical properties of the as-welded deposited metal are shown in Table 5, and the mechanical properties of the vertical butt joint are shown in Table 6. The cross-section of the tensile bar and the results of the bending specimen of Example 1 and Comparative Example 1 are as Figures 1 - 4 shown.

[0083] Table 4 Chemical Composition of Deposited Metal (wt.%)

[0084]

[0085] Table 5 Mechanical Properties of Deposited Metal

[0086] Tensile strength Yield strength Elongation Impact absorption energy (-196 °C) Technical requirements ≥550 ≥360 ≥27 ≥70 Example 1 706 462 39 99113100 Example 2 675 429 43 99107129 Example 3 664 457 41 103107111 Example 4 699 458 38 106112105 Example 5 687 435 39 10510298 Comparative example 1 608 485 15 644458

[0087] Table 6 Mechanical Properties of Vertical Butt Joint

[0088]

[0089] The tensile strength of the deposited metal of the welding electrodes in each example is ≥550 MPa, the yield strength is ≥360 MPa, the elongation is ≥22%, and the impact toughness at -196 °C is ≥70. The anti-pore performance is excellent. When welding in the flat, horizontal, vertical, and overhead positions, there is no tail red, the weld formation is beautiful, slag removal is easy, the slag can fall off in one piece, and the weld surface is smooth.

[0090] Figure 2As can be seen from the cross-section of the drawn bar, in Comparative Example 1, there are many micro pores, which are not easily noticed when welding the 1st to 4th layer of welds, but obvious pores appear in the 5th layer, and grinding is required before welding. However, when conducting mechanical form tests, obvious defects can be seen on the tensile specimens. In contrast Figures 1 - 2 It can be seen that Figure 1 It is a ductile fracture, and the drawn bar of Example 1 has obvious necking; Figure 2 There are many dense pores on the cross-section, which is a brittle fracture, and the drawn bar of Comparative Example 1 has no obvious necking and a low elongation rate.

[0091] Figures 3 - 4 They are photos of the side-bending specimens of Comparative Example 1 and Example 1, Figure 3 without defects while Figure 4 obvious defects can be seen.

[0092] The above examples are only illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. Any design identical or similar to the present invention falls within the protection scope of the present invention.

Claims

1. A nickel-based welding rod with high porosity resistance, comprising a welding core and a coating wrapped on the surface of the welding core, characterized in that: Calculated by weight, the coating includes 12-16 parts of fluorite, 10-15 parts of marble, 4-6 parts of rutile, 2-4 parts of alumina, 3-6 parts of sodium fluoride, 2-4 parts of aluminum fluoride, 0.5-1 parts of soda ash, 0.5-1 parts of CMC, 26-30 parts of metallic chromium, 3-5 parts of molybdenum powder, 4.5-7 parts of ferroniobium, 6-9 parts of medium carbon ferromanganese, 2-4 parts of rare earth ferrosilicon, 1-4 parts of ferrotitanium, and 6-12 parts of iron powder.

2. The nickel-based welding rod with high porosity resistance as claimed in claim 1, characterized in that: The welding core composition is: C≤0.03wt%, Mn≤0.05wt%, Si(0.15-0.30)wt%, P≤0.002wt%, S≤0.003wt%, Ni≥99.5wt%, Ti(0.02-0.04)wt%, and the rest are essential impurities.

3. The nickel-based welding rod with high porosity resistance as claimed in claim 1, characterized in that: In terms of mass percentage, the coating ratio in the nickel-based welding rod is 30-35%.

4. The method for preparing a nickel-based welding rod with high porosity resistance according to any one of claims 1 to 3, characterized in that: The following steps are involved: Stir the coating powder and mix it evenly; add a binder to the evenly mixed powder, stir it, and then coat it on the welding core; Baking to obtain nickel-based welding rod.

5. The method for preparing the nickel-based welding rod with high porosity resistance as claimed in claim 4, characterized in that: The binder is potassium sodium water glass.

6. The method for preparing a nickel-based welding rod with high porosity resistance as claimed in claim 5, characterized in that: The concentration of potassium sodium water glass is 42°Be"~43°Be", and the addition amount is 200ml / kg based on the mass of the coating powder.

7. The method for preparing a nickel-based welding rod with high porosity resistance as claimed in claim 4, characterized in that: After adding the binder to the uniformly mixed powder and stirring, the powder is sent into the electrode coating machine and coated on the welding core at a pressure of 12-16MPa.

8. The method for preparing a nickel-based welding rod with high porosity resistance as claimed in claim 4, characterized in that: The baking process is: baking at 100-120°C for 2 hours, baking at 240-250°C for 2 hours, and finally baking at 420°C for 1-2 hours.

9. Use of the nickel-based welding rod with high porosity resistance as claimed in any one of claims 1 to 3 in welding 9% Ni steel.

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