A low-temperature high-manganese steel submerged arc horizontal welding wire, flux and preparation method and welding method thereof for LNG ships

Abstract

The present invention discloses a submerged arc horizontal welding wire, flux and a preparation method and a welding method of low-temperature high-manganese steel for LNG ships, and belongs to the technical field of welding materials and their preparation. The welding wire of the present invention comprises: C, Mn, Ni, Mo, Si, S, P, Cr, W, Nb, N, Ti, Al, Zr, and the balance is iron and inevitable impurities; the flux comprises: CaF2, SiO2, Al2O3, CaO, MgO, aluminum-manganese-iron alloy and rare earth fluoride. The welding wire and flux provided by the present invention are suitable for submerged arc horizontal welding, and effectively solve the problems of thermal cracks, alloy element burnout, undercut, pits and the like in existing welding materials. The yield strength of the prepared weld metal is ≥480MPa, the tensile strength is ≥710MPa, the impact absorption energy of the Charpy pendulum impact test at ‑196°C is ≥95J, the lateral expansion is ≥1.22mm, there are no solidification cracks and reheating cracks, and there are no cracks in the side bending test.

Description

Technical Field

[0001] The invention relates to a low-temperature high-manganese steel submerged arc horizontal welding wire for LNG ships, a flux and a preparation method and a welding method thereof, belonging to the technical field of welding materials and preparation methods thereof. Background Art

[0002] Liquid natural gas (LNG) has gradually become an important alternative in the energy industry due to its clean and efficient characteristics. The main material for commercial LNG storage tanks is 9Ni steel, but due to the high price of Ni, many countries have conducted research on new LNG storage tank materials. In this process, low-temperature high-manganese steel has received widespread attention as a new type of low-temperature material. The C and Mn elements in low-temperature high-manganese steel have the function of stabilizing austenite. When the Mn content is greater than 25%, the high-manganese steel is a fully austenitic structure with good strength and low-temperature impact toughness.

[0003] Many steel companies have carried out research and development of low-temperature high manganese steel. At present, they can industrially produce low-temperature high manganese steel plates of different thicknesses. Tests have shown that they have excellent plasticity and toughness, far exceeding the latest IMO requirements. At the same time, the steel plates have good weldability.

[0004] Submerged arc welding is a commonly used welding method for low-temperature high manganese steel. However, the submerged arc welding materials for low-temperature high manganese steel are still very limited. Nickel-based alloy welding materials can be used for welding low-temperature high manganese steel, but their cost is relatively high. Therefore, it is necessary to provide a submerged arc horizontal welding wire and flux suitable for LNG ship low-temperature high manganese steel to solve the problems of easy thermal cracking, alloy element burning, undercut, pits, etc. in existing welding materials. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a low-temperature high-manganese steel submerged arc horizontal welding wire, a flux and a preparation method and a welding method thereof for LNG ships.

[0006] The technical solution of the present invention:

[0007] One of the purposes of the present invention is to provide a low-temperature high-manganese steel submerged arc horizontal welding wire for LNG ships. The chemical composition of the welding wire, measured by weight percentage, includes: C: 0.3-0.5%, Mn: 23-27%, Ni: 2-6.5%, Mo: 0.4-2%, Si≤0.1%, S≤0.005%, P≤0.005%, Cr: 2.5-5.0%, W: 0.8-3.0%, Nb: 0.05-0.5%, N: 0.01-0.03%, Ti: 0.01-0.05%, Al≤0.02%, Zr: 0.01-0.03%, and the balance is iron and inevitable impurities.

[0008] In the invention, the reasons for setting the chemical composition range of the low temperature high manganese steel submerged arc horizontal welding wire for LNG ships are as follows:

[0009] C: 0.3% to 0.5%; when the C content exceeds 0.06%, the strength and hardenability of the weld can be significantly improved. At the same time, C has the function of promoting the formation of austenite and stabilizing austenite, so a certain amount of carbon needs to be added. However, when the C content exceeds 0.6%, it is easy to form brittle carbides at the grain boundaries, reducing the low-temperature toughness of the alloy. Therefore, in the present invention, the C content is controlled to 0.3% to 0.5%.

[0010] Mn: 23% to 27%; the main function of Mn is to form stable austenite and improve the toughness of the material. Mn in the matrix structure exists in the form of solid solution, which has a solid solution strengthening effect on the matrix and improves the low-temperature toughness of the material. Considering the burnout of Mn element during welding and the compatibility of Mn content with the base material, the Mn content is controlled at 23% to 27% in the present invention.

[0011] Ni: 2% to 6.5%; Ni combines with non-metallic atoms to form a solid solution, segregates at the grain boundary, and plays a role in solid solution strengthening and improving the strength of the weld. At the same time, Ni is also a very good austenite stabilizing element. When the addition amount does not exceed 9%, it significantly improves the low-temperature toughness of the alloy. When the Ni addition amount exceeds 9%, the weld hardenability is higher and the tendency to produce hot cracks is significantly increased. Therefore, the present invention controls the Ni content to 2% to 6.5%.

[0012] Mo: 0.4% to 2%; When the Mo content is above 0.4%, the strength of the weld deposited metal is significantly improved through solid solution strengthening. However, when the Mo content exceeds 2.5%, the stacking fault energy of the alloy is reduced. Under low-temperature impact, phase transformation-induced plasticity occurs to form martensite, which reduces the low-temperature toughness of the material. Therefore, the present invention controls the Mo content to 0.4% to 2%.

[0013] Si≤0.1%; Si has a good deoxidation effect. Adding Si at a content of 0.1-0.4% can effectively deoxidize the weld metal. When the Si content exceeds 0.4%, the stacking fault energy will be reduced, and martensite will be easily formed under low-temperature impact, which will reduce the low-temperature toughness. Considering that the flux will introduce a part of Si during the welding process, the Si content is controlled below 0.1% in the design of the welding wire of the present invention.

[0014] P≤0.005%, S≤0.005%; P is an impurity that causes high temperature cracking. S reacts with Fe to form low melting point compounds such as FeS, which causes high temperature cracking. However, due to the uneven composition, the P and S often contained in welding materials should be limited to a low range as much as possible. In the present invention, the P and S contents are controlled to be below 0.005%.

[0015] Cr: 2.5-5.0%; when the amount of Cr added exceeds 1.2%, it can significantly play a role in solid solution strengthening and improve the strength of the alloy. At the same time, Cr can promote the twinning transformation of low-temperature high-manganese steel, reduce the amount of martensite transformation, and improve the low-temperature performance of the alloy. However, when the Cr content exceeds 5%, coarse chromium compounds are formed, which reduces the strength and toughness of the material. Therefore, the present invention controls the Cr content to 2.5%-5.0%.

[0016] W: 0.8-3.0%; the compound formed by W and non-metallic elements has a higher melting point, which reduces the solidification temperature range during the solidification process of the alloy and reduces the possibility of forming thermal cracks. At the same time, the compound formed by W is smaller and evenly distributed on the surface of the matrix, which has a pinning effect on dislocations. In the present invention, the W content is controlled at 0.8%-3.0%.

[0017] Nb: 0.05-0.5%; Nb is beneficial to the formation of bainite and improves the hardenability of the alloy, but too high a Nb content will promote the formation of island martensite, so the present invention controls the Nb content to 0.05%-0.5%.

[0018] N: 0.01-0.03%; N can combine with Ti to form TiN precipitates uniformly distributed on the surface of the base material, pinning dislocations and indirectly affecting the performance of the weld. However, when the N content exceeds 0.03%, the solid-soluted N accumulates in the weld metal, which reduces the low-temperature toughness. Therefore, the present invention controls the N content to 0.01%-0.03%.

[0019] Ti: 0.01-0.05%; Ti has the function of inhibiting the formation of coarse carbides at grain boundaries and strengthening the grain boundaries, but excessive Ti will precipitate as coarse oxides to reduce the toughness of the material, so the present invention controls the Ti content to 0.01%-0.05%.

[0020] Al≤0.02%; Al can play a certain role in solid solution strengthening, and Al can also deoxidize and denitrify the weld metal, but too much Al will reduce the strength of the material, and the corrosion resistance of the weld will be reduced when the aluminum content is high.

[0021] Zr: 0.01-0.03%; Zr can effectively improve the slag removal and deoxidation effects of the alloy, and Zr has a good improvement effect on the undercut and pits caused by the alloy liquid dripping during horizontal welding. However, too high a Zr content will promote the formation of tight welding slag, weaken the chemical reaction of the weld metal, and is not conducive to exhaust, and the mechanical properties of the weld are poor. In the present invention, the amount of Zr added is controlled to 0.01%-0.03%.

[0022] It is further defined that the chemical composition of the welding wire, by weight percentage, includes: C: 0.35-0.45%, Mn: 24-27%, Ni: 3.5-6.5%, Mo: 1.2-2%, Si≤0.008%, S≤0.005%, P≤0.005%, Cr: 3.0-4.5%, W: 1.5-3.0%, Nb: 0.15-0.35%, N: 0.01-0.03%, Ti: 0.015-0.045%, Al≤0.02%, Zr: 0.015-0.030%, and the balance is iron and unavoidable impurities.

[0023] It is further defined that the chemical composition of the welding wire, by weight percentage, includes: C: 0.38%, Mn: 25%, Ni: 4%, Mo: 1.6%, Si: 0.008%, S: 0.003%, P: 0.004%, Cr: 4.2%, W: 2.6%, Nb: 0.2%, N: 0.02%, Ti: 0.035%, Al: 0.02%, Zr: 0.02%, and the balance is iron and unavoidable impurities.

[0024] It is further defined that the chemical composition of the welding wire, by weight percentage, includes: C: 0.42%, Mn: 24%, Ni: 5.5%, Mo: 2%, Si: 0.005%, S≤0.003%, P≤0.003%, Cr: 3.5%, W: 2.5%, Nb: 0.2%, N: 0.02%, Ti: 0.002%, Al: 0.02%, Zr: 0.02%, and the balance is iron and unavoidable impurities.

[0025] The second object of the present invention is to provide a method for preparing the above-mentioned low-temperature high-manganese steel submerged arc horizontal welding wire for LNG ships. The method is: weigh each component in proportion, and successively undergo vacuum induction furnace melting, refining, forging, heat treatment, drawing, surface treatment and layer winding processes to obtain a finished welding wire with a diameter of Φ2.4mm.

[0026] It is further defined that the method comprises the following steps:

[0027] Step 1, batching and furnace charging: weigh and batch the raw materials according to the weight fraction, and load the raw materials into the vacuum induction furnace for melting;

[0028] Step 2, refining: adding refining agent to remove impurities and refine crystals;

[0029] Step 3, forging and rolling: rough forging, fine forging, and rolling the resulting ingot;

[0030] Step 4, heat treatment: stress relief annealing after rolling;

[0031] Step 5, drawing: the material is roughly drawn and finely drawn to obtain a welding wire with a diameter of Φ2.4mm;

[0032] Step 6, surface treatment: polishing after drying;

[0033] Step 7, Packaging: Precision wind the qualified welding wire into layers and pack it.

[0034] The third object of the present invention is to provide a flux for use with the above-mentioned LNG ship low-temperature high-manganese steel submerged arc horizontal welding wire. The chemical composition of the flux, by weight percentage, includes: CaF2: 15-35%, SiO2≤5%, Al2O3: 15-30%, CaO: 8-20%, MgO: 5-20%, aluminum-manganese-iron alloy: 0.5-3%, and rare earth fluoride: 0.1-0.5%.

[0035] In the invention, the reasons for setting the chemical composition range of the submerged arc horizontal welding flux for low temperature high manganese steel for LNG ships are as follows:

[0036] CaF2: 15-35%; CaF2 has the effect of reducing the viscosity of the alloy liquid. In the present invention, there are many types of alloys added, the interfacial tension of the alloy liquid is large, the viscosity is large, and the fluidity of the alloy is poor, which often causes pits, weld nodules and other problems during the horizontal welding process. Therefore, CaF2 needs to be added to the flux. In addition, F decomposed by CaF2 - Ions and H + The ions combine to form HF, which reduces the hydrogen embrittlement tendency of the weld metal and improves the low-temperature toughness of the alloy. In the present invention, the amount of fluorite added is controlled to be 15% to 35%.

[0037] SiO2≤5%; SiO2 is an acidic oxide that can improve the pH of the slag system. At the same time, SiO2 can improve the fluidity of the alloy and promote the discharge of slag. However, during the welding process, the flux will transfer Si to the weld metal. A small amount of Si in the weld alloy can play a deoxidation role, but excessive silicon oxides will increase the brittleness of the alloy and reduce the low-temperature performance of the alloy. In the present invention, the amount of SiO2 added is controlled to ≤5%.

[0038] Al2O3: 15-30%; Al2O3 is a neutral oxide. The purpose of adding Al2O3 to the flux is to remove slag and improve the quality of the weld. In the present invention, in order to better improve the performance of the weld metal, more types of metals are added, and the chemical reaction is violent, which is not conducive to the discharge of slag. Therefore, Al2O3 is added to ease the chemical reaction and promote the formation of a smooth and flat weld. However, adding too much Al2O3 will increase the interfacial tension of the weld metal and increase the undercut tendency of horizontal welding. Therefore, in the present invention, the amount of Al2O3 added is controlled to 15%-30%.

[0039] CaO: 8-20%; CaO is an alkaline oxide that can adjust the pH of the slag system and improve the viscosity and interfacial tension of the molten droplet. At the same time, CaO can also react with S and P to reduce the S and P content and improve the crack resistance of the weld. At the same time, CaO also has a certain arc stabilization effect to prevent spatter during welding. In the present invention, the amount of CaO added is controlled at 8% to 20%.

[0040] MgO: 5-20%; MgO is a basic oxide with strong alkalinity and is an important material for adjusting the acidity and alkalinity of the flux. MgO is a good slag-forming material and promotes the formation of a smooth weld. However, adding more MgO will reduce the fluidity of the welding slag and weaken the slag removal effect. In the present invention, the amount of MgO added is controlled to 5%-15%.

[0041] Aluminum-manganese-iron alloy: 0.5-3%; aluminum and manganese promote the formation of stable austenite and improve the toughness of the material. Aluminum and manganese in the matrix structure exist in the form of solid solution, which plays a solid solution strengthening role on the matrix and improves the low-temperature toughness of the material. Since aluminum and manganese will be burned to a certain extent during welding, aluminum and manganese-iron alloys are added to the flux to increase the aluminum and manganese content in the weld metal through flux transition. In the present invention, the addition amount of aluminum-manganese-iron alloy is controlled at 0.5% to 3%.

[0042] Rare earth fluoride: 0.1-0.5%; The role of adding rare earth fluoride is that due to the large number of metal types contained in the welding wire composition, the interface tension is large and the wettability is poor, which leads to the undercut problem of submerged arc welding horizontal welding. Therefore, adding rare earth fluoride improves the wettability of the submerged arc welding weld metal and prevents undercut. At the same time, rare earth elements can strengthen the grain boundary and improve the mechanical properties of the alloy. In the present invention, the addition amount of rare earth fluoride is controlled to be 0.1%-0.5%.

[0043] It is further defined that the chemical composition of the flux, calculated by weight percentage, includes: CaF2: 28-35%, SiO2: 2.5-5%, Al2O3: 24-30%, CaO: 12-20%, MgO: 15-20%, aluminum-manganese-iron alloy: 1.5-3.0%, and rare earth fluoride: 0.1-0.45%.

[0044] It is further defined that the chemical composition of the flux, measured by weight percentage, includes: CaF2: 32%, SiO2: 4.5%, Al2O3: 27%, CaO: 16%, MgO: 18%, aluminum-manganese-iron alloy: 2.2%, and rare earth fluoride: 0.3%.

[0045] It is further defined that the chemical composition of the flux, measured by weight percentage, includes: CaF2: 32%, SiO2: 3%, Al2O3: 28%, CaO: 16%, MgO: 18%, aluminum-manganese-iron alloy: 2.7%, and rare earth fluoride: 0.3%.

[0046] It is further defined that the content of electrolytic manganese in the aluminum-manganese-iron alloy is 45% by mass, the content of aluminum is 35% by mass, and the content of iron is 20% by mass.

[0047] The fourth object of the present invention is to provide a method for preparing the above-mentioned LNG ship low-temperature high-manganese steel submerged arc horizontal welding flux, which comprises weighing each component in proportion, dry-mixing evenly, adding pure sodium water glass at a weight ratio of 15% of the flux, stirring evenly and then granulating, sintering at 800±20°C, and screening.

[0048] It is further defined that the method comprises the following steps:

[0049] (1) Ingredients: Weigh the flux according to the weight fraction of each component and put the raw materials into a mixer.

[0050] (2) Dry mixing: Stir for 30 minutes to ensure that the raw materials are evenly mixed.

[0051] (3) Wet mixing: Add pure sodium water glass and stir for 120 minutes to mix the ingredients evenly.

[0052] (4) Granulation: The uniformly mixed wet material is granulated by rotation to obtain granules of 20 to 50 mesh.

[0053] (5) Sintering: The flux is sintered in a sintering furnace at 800±20℃ to remove the moisture in the welding material and the combined water of the raw materials.

[0054] (6) Screening: Screen the dried flux and select qualified products.

[0055] The fourth object of the present invention is to use the above-mentioned welding wire and flux to perform a submerged arc horizontal welding process for low-temperature high manganese steel for LNG ships. The welding process parameters are: welding current 280~350A, arc voltage 26~32V, welding speed 40~50cm / min, heat input 8.74~16.8kJ / cm, and welding angle 60°~120°.

[0056] It is further defined that the welding angle is 75° to 85° or 95° to 105°.

[0057] It is further defined that the thickness of the welding specimen is 20 to 45 mm and the V-groove angle is 45°.

[0058] The welding wire and flux provided by the present invention contain a certain amount of Mn element, and a certain amount of carbon, silicon, nickel, chromium, molybdenum and other elements that stabilize austenite and improve strength are also added during the design of the welding wire. In addition, in order to prevent cracks and improve grain boundary strength, some tungsten, titanium, aluminum, niobium and some rare earth elements need to be added. Compared with the prior art, the present application also has the following beneficial effects:

[0059] (1) The present invention reduces the content of precious metals such as Ni, Cr, and Mo as much as possible while ensuring the strength and toughness of the weld metal, thereby reducing the cost of the product, and adding Zr and rare earth fluoride to the flux to improve the wettability of the weld metal, making the welding wire and the flux matched therewith more suitable for submerged arc horizontal welding, and having a good improvement effect on the problems of thermal cracks, alloy element burnout, undercut, pits, etc. existing in the existing welding materials. In addition, by adding W to generate high melting point compounds, the solidification interval is shortened, the tendency of hot cracks in the weld metal is reduced, and the problems of hot cracks, alloy element burnout, undercut, pits, etc. existing in the submerged arc horizontal welding of warm high manganese steel are further solved.

[0060] (2) The weld metal prepared by the welding material of the present invention has good compatibility with the low-temperature high-manganese steel base material. The aluminum-manganese-iron alloy and rare earth fluoride used in the flux of the present invention solve the problem of coarse structure in the welding process. The Zr and Ti combined deoxidation of the welding wire solves the low-temperature impact performance, which has originality and improves the low-temperature performance.

[0061] (3) The weld metal prepared by the welding wire and flux provided by the present invention has a yield strength of ≥480MPa, a tensile strength of ≥710MPa, an impact absorption energy of ≥95J in a Charpy pendulum impact test at -196°C, a lateral expansion of ≥1.22mm, no solidification cracks and reheating cracks, and no cracks in a side bending test. It meets the requirements of liquefied natural gas storage tanks for weld metal performance BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 Schematic diagram of submerged arc horizontal welding angle, where θ1 = 60° is the minimum inclination angle of horizontal welding, and θ2 = 120° is the maximum inclination angle of horizontal welding. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0064] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0065] Embodiment 1:

[0066] The chemical composition of the welding wire of this embodiment, measured by weight percentage, includes: C: 0.38%, Mn: 25%, Ni: 4%, Mo: 1.6%, Si: 0.008%, S: 0.003%, P: 0.004%, Cr: 4.2%, W: 2.6%, Nb: 0.2%, N: 0.02%, Ti: 0.035%, Al: 0.02%, Zr: 0.02%, and the balance is iron and other inevitable impurities.

[0067] The preparation method of the welding wire is as follows: each component is weighed in proportion, and the welding wire with a specification of Φ2.4 mm is obtained through smelting, forging, heat treatment, drawing and surface treatment.

[0068] The chemical composition of the flux of this embodiment, measured by weight percentage, includes: CaF2: 32%, SiO2: 4.5%, Al2O3: 27%, CaO: 16%, MgO: 18%, aluminum-manganese-iron alloy: 2.2%, and rare earth fluoride: 0.3%.

[0069] The preparation method of the flux is as follows: weigh the components in proportion, dry mix, add pure sodium water glass for wet mixing, granulate, sinter at 800° C., and sieve to obtain the flux.

[0070] The above welding wire is used to weld low-temperature high manganese steel plates, with a 45° V-shaped groove, a welding current of 320A, a welding arc voltage of 30V, a welding speed of 40cm / min, a heat input of 14.4kJ / cm, and a welding angle of 80°.

[0071] The weld metal made of the welding material used in this embodiment has a yield strength of 483MPa, a tensile strength of 722MPa, an impact absorption energy of 99J in a Charpy pendulum impact test at -196°C, a lateral expansion of 1.24mm, no solidification cracks and reheating cracks, and no cracks in a side bending test. The requirements for weld metal performance for the construction of liquefied natural gas storage tanks are met.

[0072] Embodiment 2:

[0073] The chemical composition of the welding wire of this embodiment, measured by weight percentage, includes: C: 0.38%, Mn: 25%, Ni: 4%, Mo: 1.6%, Si: 0.008%, S: 0.003%, P: 0.004%, Cr: 4.2%, W: 2.6%, Nb: 0.2%, N: 0.02%, Ti: 0.035%, Al: 0.02%, Zr: 0.02%, and the balance is iron and other inevitable impurities.

[0074] The preparation method of the welding wire is as follows: each component is weighed in proportion, and the welding wire with a specification of Φ2.4 mm is obtained through smelting, forging, heat treatment, drawing and surface treatment.

[0075] The chemical composition of the flux of this embodiment, measured by weight percentage, includes: CaF2: 32%, SiO2: 3%, Al2O3: 28%, CaO: 16%, MgO: 18%, aluminum-manganese-iron alloy: 2.7%, and rare earth fluoride: 0.3%.

[0076] The preparation method of the flux is as follows: weigh the components in proportion, dry mix, add pure sodium water glass for wet mixing, granulate, sinter at 800° C., and sieve to obtain the flux.

[0077] The above welding wire is used to weld low-temperature high manganese steel plates, with a 45° V-shaped groove, a welding current of 320A, a welding arc voltage of 30V, a welding speed of 40cm / min, a heat input of 14.4kJ / cm, and a welding angle of 80°.

[0078] The weld metal made of the welding material used in this embodiment has a yield strength of 492MPa, a tensile strength of 745MPa, an impact absorption energy of 102J in a Charpy pendulum impact test at -196°C, a lateral expansion of 1.27mm, no solidification cracks and reheating cracks, and no cracks in a side bending test. The requirements for weld metal performance for the construction of liquefied natural gas storage tanks are met.

[0079] Embodiment 3:

[0080] The chemical composition of the welding wire of this embodiment, measured by weight percentage, includes: C: 0.42%, Mn: 24%, Ni: 5.5%, Mo: 2%, Si: 0.005%, S≤0.003%, P≤0.003%, Cr: 3.5%, W: 2.5%, Nb: 0.2%, N: 0.02%, Ti: 0.02%, Al: 0.02%, Zr: 0.02%, and the balance is iron and other inevitable impurities.

[0081] The preparation method of the welding wire is as follows: each component is weighed in proportion, and the welding wire with a specification of Φ2.4 mm is obtained through smelting, forging, heat treatment, drawing and surface treatment.

[0082] The chemical composition of the flux of this embodiment, measured by weight percentage, includes: CaF2: 32%, SiO2: 3%, Al2O3: 28%, CaO: 16%, MgO: 18%, aluminum-manganese-iron alloy: 2.7%, and rare earth fluoride: 0.3%.

[0083] The preparation method of the flux is as follows: weigh the components in proportion, dry mix, add pure sodium water glass for wet mixing, granulate, sinter at 800° C., and sieve to obtain the flux.

[0084] The above welding wire is used to weld low-temperature high manganese steel plates, with a 45° V-shaped groove, a welding current of 320A, a welding arc voltage of 30V, a welding speed of 40cm / min, a heat input of 14.4kJ / cm, and a welding angle of 80°.

[0085] The weld metal made of the welding material used in this embodiment has a yield strength of 487MPa, a tensile strength of 733MPa, an impact absorption energy of 106J in a Charpy pendulum impact test at -196°C, a lateral expansion of 1.35mm, no solidification cracks and reheating cracks, and no cracks in a side bending test. The requirements for weld metal performance for the construction of liquefied natural gas storage tanks are met.

[0086] Embodiment 4:

[0087] The chemical composition of the welding wire of this embodiment, measured by weight percentage, includes: C: 0.42%, Mn: 24%, Ni: 5.5%, Mo: 2%, Si: 0.005%, S≤0.003%, P≤0.003%, Cr: 3.5%, W: 2.5%, Nb: 0.2%, N: 0.02%, Ti: 0.02%, Al: 0.02%, Zr: 0.02%, and the balance is iron and other inevitable impurities.

[0088] The preparation method of the welding wire is as follows: each component is weighed in proportion, and the welding wire with a specification of Φ2.4 mm is obtained through smelting, forging, heat treatment, drawing and surface treatment.

[0089] The chemical composition of the flux of this embodiment, measured by weight percentage, includes: CaF2: 32%, SiO2: 3%, Al2O3: 28%, CaO: 16%, MgO: 18%, aluminum-manganese-iron alloy: 2.7%, and rare earth fluoride: 0.3%.

[0090] The preparation method of the flux is as follows: weigh the components in proportion, dry mix, add pure sodium water glass for wet mixing, granulate, sinter at 800° C., and sieve to obtain the flux.

[0091] The above welding wire is used to weld low-temperature high manganese steel plates, with a 45° V-shaped groove, a welding current of 320A, a welding arc voltage of 30V, a welding speed of 40cm / min, a heat input of 14.4kJ / cm, and a welding angle of 95°.

[0092] The weld metal made of the welding material used in this embodiment has a yield strength of 491 MPa, a tensile strength of 721 MPa, an impact absorption energy of 96 J in a Charpy pendulum impact test at -196°C, a lateral expansion of 1.22 mm, no solidification cracks and reheating cracks, and no cracks in a side bending test, meeting the requirements for weld metal performance in the construction of liquefied natural gas storage tanks.

[0093] Although the present invention has been disclosed as above in the preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A low temperature high manganese steel submerged arc horizontal welding wire for LNG ships, characterized in that: The chemical composition, by weight percentage, includes: C: 0.35-0.45%, Mn: 24-27%, Ni: 3.5-6.5%, Mo: 1.2-2%, Si≤0.008%, S≤0.005%, P≤0.005%, Cr: 3.0-4.5%, W: 1.5-3.0%, Nb: 0.15-0.35%, N: 0.01-0.03%, Ti: 0.015-0.045%, Al≤0.02%, Zr: 0.015-0.030%, and the balance is iron and unavoidable impurities; The chemical composition of the flux used in conjunction with the above-mentioned LNG ship low-temperature high-manganese steel submerged arc horizontal welding wire includes, by weight percentage: CaF2: 28-35%, SiO2: 2.5-5%, Al2O3: 24-30%, CaO: 12-20%, MgO: 15-20%, aluminum-manganese-iron alloy: 1.5-3.0%, rare earth fluoride: 0.1-0.45%; The aluminum-manganese-iron alloy contains 45% electrolytic manganese, 35% aluminum and 20% iron by mass.

2. A method for preparing the low temperature high manganese steel submerged arc horizontal welding wire for LNG ships according to claim 1, characterized in that: The components are weighed in proportion and sequentially subjected to the processes of vacuum induction furnace melting, refining, forging, heat treatment, drawing, surface treatment and layer winding to obtain a finished welding wire with a diameter of Φ2.4mm.

3. A method for preparing a flux matching the low temperature high manganese steel submerged arc horizontal welding wire for LNG ships according to claim 1, characterized in that: Weigh each component in proportion, dry mix evenly, add pure sodium water glass in a flux weight ratio of 15%, stir evenly and then granulate, sinter at 800±20℃ and sieve.

4. A welding process for submerged arc horizontal welding of low temperature high manganese steel for LNG ships, characterized in that: The submerged arc horizontal welding uses the welding wire and flux described in claim 1, and the welding process parameters are: welding current 280-350A, arc voltage 26-32V, welding speed 40-50cm / min, heat input 8.74-16.8kJ / cm, and welding angle 60°-120°.

5. The welding process for submerged arc horizontal welding of low temperature high manganese steel for LNG ships according to claim 4 is characterized in that: The welding angle is 75°~85° or 95°~105°.

6. The welding process for submerged arc horizontal welding of low temperature high manganese steel for LNG ships according to claim 4 is characterized in that: The thickness of the welding specimen is 20-45 mm, and the V-groove angle is 45°.

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