Electrode for ac welding of 9ni steel

Abstract

The application discloses an electrode for AC welding of 9Ni steel, which is characterized by comprising a welding core and a coating, wherein the welding core is a pure nickel welding core, and the coating is composed of powder bonding; the components of the powder are as follows in percentage by weight: 16-20% of fluoride; 20-25% of carbonate; 1-5% of titanium oxide; 2-6% of potassium titanate; 3-5% of tungsten powder; 1-3% of tungsten oxide; 1-3% of atomized ferrosilicon; 1-6% of electrolytic manganese; 5-10% of ferro-niobium; 10-15% of molybdenum powder; 25-28% of metallic chromium; 1-5% of iron powder; 0.1-0.6% of graphite; and 1-3% of seaweed salt. The electrode is used for AC welding, and the electrode has excellent AC stable arc property, and the welding cladding metal has good technical performance at-196 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal welding, and particularly relates to a 9Ni steel electrode for alternating current welding. BACKGROUND

[0002] With the rapid development of global integration and industrialization, the demand for energy is increasing, while on the other hand, global climate warming requires each country to reach the peak of carbon and carbon neutrality, so the demand for clean energy is increasing, and the status and role of natural gas as clean fuel are increasingly prominent. Global natural gas production and consumption are showing a rapid growth trend. The transportation and storage of liquefied natural gas require a large number of low-temperature storage tanks (LNG storage tanks), and the working environment requires that the material for manufacturing LNG storage tanks has good low-temperature toughness and good strength in a low-temperature environment.

[0003] 9Ni steel is a medium alloy steel developed by the International Nickel Company of the United States, and the organization is martensite plus bainite. This steel still has good low-temperature impact toughness, high strength and corrosion resistance at very low temperatures, and has less alloy content, low thermal expansion rate and good welding performance. Therefore, 9Ni steel has become one of the main materials for manufacturing LNG storage tanks.

[0004] In recent years, LNG technology has developed rapidly, and LNG storage tanks have basically achieved localization design and manufacturing, so the demand for 9Ni steel and supporting welding materials has been greatly stimulated, and the most used in the engineering application of LNG storage tanks is the electrode for manual arc welding. At present, one kind of domestic electrode ensures the alternating current welding process performance by reducing the fluorides in the coating.

[0005] CN106181115A discloses a low-splashing 9Ni steel nickel-based electrode, which comprises a welding core and a coating. The coating composition comprises, by weight percentage: 6-15% cryolite, 21-24% marble, 10-14% rutile, 2-8% silicon oxide, 2-7% strontium carbonate, 2-6% metallic molybdenum, 2-3% metallic manganese, 1-6% borax, and 05-3% seaweed salt.

[0006] CN113414519A discloses an alternating current ENi6620 nickel-based electrode and its preparation method and welding method, including an electrode core and a coating covering the surface of the electrode core, the coating composition and content are: marble 6-10 parts by weight, strontium carbonate 3-6 parts by weight, fluorite 6-9 parts by weight, potassium cryolite powder 2-5 parts by weight, potassium fluoborate 0.5-1.5 parts by weight, rutile 2-6 parts by weight, electrolytic manganese 5-8 parts by weight, metallic chromium 25-30 parts by weight, molybdenum iron 15-22 parts by weight, titanium iron 2-5 parts by weight, tungsten powder 3-6 parts by weight, niobium iron 5-9 parts by weight, soda ash 1-3 parts by weight, potassium titanate 2-6 parts by weight, rare earth fluoride 1-4 parts by weight, zirconium dioxide 0.5-2.5 parts by weight, rare earth silicon iron 0.5-3.5 parts by weight.

[0007] In these two patents, the fluoride in CN106181115A is less than 15% (6-15% cryolite), and the fluoride in CN113414519A is also less than 15% (fluorite 6-9 parts by weight, potassium cryolite powder 2-5 parts by weight, potassium fluoborate 0.5-1.5 parts by weight), the fluoride in the coating plays a dehydrogenation role, making the molten pool have lower diffusible hydrogen, thereby ensuring good low-temperature mechanical property indicators. Another domestic electrode is alkaline slag system to ensure mechanical property indicators, with more carbonates and fluorides, but the alternating current welding stability is not very stable.

[0008] In order to increase the fluoride content, CN111590240A discloses a 9%Ni steel matching nickel-based electrode for overhead welding, the coating uses high-alkalinity CaCO3-MgCO3-CaF2 low-hydrogen slag system, the coating composition is: calcium carbonate 20-26%; magnesium carbonate 15-24%; calcium fluoride 10-15%; potassium cryolite 10-16%; sodium carbonate 0-1%; rutile 3-8%; metallic manganese 2-4%; rare earth silicon iron 2-5%; titanium iron 1-3%; aluminum powder 0.5-3.0%; molybdenum powder 10-15%; tungsten powder 2.5-4.0%; zirconium powder 1-4%; alginate 0.5-2.5%.

[0009] Although the fluoride in this patent is greatly increased to more than 20% (calcium fluoride 10-15%; potassium cryolite 10-16%), the alkalinity is also high, and the carbonate content exceeds 35% (calcium carbonate 20-26%; magnesium carbonate 15-24%), the excessive carbonate makes the molten pool too violent during alternating current welding, and the large amount of fluoride further exacerbates the instability of alternating current welding, because F ions are high ionization potential elements, and a large amount of F ions destroy the stability of alternating current.

[0010] The stability of the welding arc directly determines whether the welding process can be continuously and smoothly carried out and influences the quality of the final weld. The arc instability is easy to cause the poor fusion of the base material and the weld, and to produce defects such as pores and slag. The stability of the welding arc is generally related to the welding parameters, and mainly the performance of the welding material and the characteristics and types of the welding power source.

[0011] It is well known that the stability of the direct current welding is obviously better than that of the alternating current power source, because the positive and negative poles are changed 50 times per second in the alternating current welding, and the current passes through zero point 100 times per second. When the current passes through zero point each time, the arc will be extinguished instantaneously, which will cause the weakening of the electron emission and the gas ionization, and is easy to cause the arc instability. However, the magnetic blow is easy to occur in the welding of 9Ni steel, so the alternating current welding has to be adopted, so we must solve this problem by improving the characteristics of the welding material.

[0012] The arc stability of the welding material depends on its own chemical composition. Different chemical elements have different ionization potentials, and the smaller the ionization potential is, the easier the ionization is. Therefore, the more the easily ionized elements and compounds contained in the welding material are, the more stable the arc is. The welding material of the acid slag system is easy to be welded by alternating current because it contains more easily ionized substances. However, the welding material of the alkaline slag system contains more fluorides. Fluorine not only has high ionization potential, but also has great affinity with electrons, can capture the electrons in the arc, form negative ions, and reduce the number of electrons, thereby reducing the stability of the arc. For example, the welding material of the acid slag system contains more easily ionized substances, so it is easy to be welded by alternating current. However, the welding material of the alkaline slag system contains more fluorides, so it is not easy to be welded by alternating current.

[0013]

[0014] Therefore, we want to invent a kind of welding material which contains a certain amount of fluorides, so that it has better dehydrogenation performance and can obtain good technical indexes, and cannot use the traditional alkaline slag system to cause the fluorine content to be too high and affect the stability of the alternating current welding. SUMMARY

[0015] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art, and to provide a welding rod for 9Ni steel for alternating current welding, which can meet the alternating current welding of 9Ni steel and meet various welding technical indexes.

[0016] The welding rod for 9Ni steel for alternating current welding can contain a certain amount of fluorides, so that it has better dehydrogenation performance and can obtain good technical indexes, and can overcome the problem that the traditional alkaline slag system causes the fluorine content to be too high and affects the stability of the alternating current welding.

[0017] In order to achieve the purpose of the present application, the technical scheme adopted is:

[0018] A welding rod for 9Ni steel for alternating current welding, comprising a welding core and a coating,

[0019] The core part is pure nickel core, and the coating part is composed of powder bonding;

[0020] The components of the powder are as follows in weight:

[0021] 16%-20% of fluoride;

[0022] 20%-25% of carbonate;

[0023] 1%-5% of titanium oxide;

[0024] 2%-6% of potassium titanate;

[0025] 3%-5% of tungsten powder;

[0026] 1%-3% of tungsten oxide;

[0027] 1%-3% of atomized ferrosilicon;

[0028] 1%-6% of electrolytic manganese;

[0029] 5%-10% of niobium iron;

[0030] 10%-15% of molybdenum powder;

[0031] 25%-28% of metallic chromium;

[0032] 1%-5% of iron powder;

[0033] 0.1%-0.6% of graphite;

[0034] 1%-3% of seaweed salt.

[0035] In a preferred embodiment of the present application, the weight ratio of the coating to the electrode body is (3.5-4.5):10.

[0036] In a preferred embodiment of the present application, the tungsten oxide is WO3, W20O58, W18O49, WO2.

[0037] In a preferred embodiment of the present application, the fluoride is any one or more of calcium fluoride, sodium fluoroaluminate and potassium fluoroaluminate.

[0038] In a preferred embodiment of the present application, the carbonate is any one or more of calcium carbonate, strontium carbonate, lithium carbonate and barium carbonate.

[0039] The present application has the following beneficial effects:

[0040] The AC welding with the electrode of the present application has excellent AC arc stability, and the welding cladding metal has good technical performance at -196 degrees Celsius.

[0041] It can realize that both containing a certain amount of fluoride, making it better dehydrogenation performance, while good technical index can be obtained; overcome the problem that the traditional alkaline slag system leads to too high fluoride content, affecting the stability of alternating current welding. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The state after welding is CN111590240A.

[0043] Figure 2 The state after welding is CN111590240A.

[0044] Figure 3 The weld effect diagram after slag removal is CN111590240A.

[0045] Figure 4 The weld effect diagram after slag removal is CN111590240A. DETAILED DESCRIPTION

[0046] In order to meet the manual arc welding requirements of 9Ni steel for alternating current welding, the main difference between the present application and the prior art scheme is that:

[0047] First, the coating of the electrode in the present application adopts a unique fluoride-carbonate-tungsten oxide slag system, and the fluoride in the coating dilutes the welding pool, improves the fluidity of the nickel-based alloy welding pool, is beneficial to the overflow of harmful gas, and the fluoride ion combines with hydrogen to reduce the diffusion hydrogen content in the pool and prevent the generation of hydrogen pores.

[0048] Second, carbonate is added in the present application, which mainly plays a role in slagging and gas making, and strontium carbonate and the like also have moisture absorption resistance, which can better reduce the diffusion hydrogen content of the pool.

[0049] Third, tungsten oxide (WOX) is added in the powder of the present application, which has two effects: one is that it increases the addition amount of fluoride in the coating. Generally, with the increase of fluoride, the slag system will deteriorate alternating current welding, because fluoride is a counter-ion material, which will rob the electrons in the arc, and tungsten oxide will react first with fluoride ions to protect the electrons in the arc, and the specific reaction is as follows:

[0050]

[0051] Fourth, the melting point of tungsten oxide is relatively high, which can improve the high-temperature melting point of the molten slag during welding, and make the all-position welding process better.

[0052] The effects of other components in the powder in the coating of the electrode in the present application are shown in Table 1 as follows:

[0053]

[0054] Considering that the main element in the chemical composition of the pure nickel welding core is Ni element, in order to match the Ni-Cr-Mo alloy system adopted by the electrode for 9Ni steel, other elements must be supplemented in the coating.

[0055] Therefore, 3%-5% of tungsten powder, 5%-10% of niobium iron, 10%-15% of molybdenum powder and 25%-30% of metal chromium are added in the coating; meanwhile, 1%-3% of atomized ferrosilicon and 1%-6% of electrolytic manganese are added to facilitate desulfurization and deoxidization.

[0056] In addition, 0.1%-0.6% of graphite in mass percentage is added in the coating to refine the transition droplet and reduce the electrode spatter. 1%-5% of iron powder is added to improve the fluidity of the molten pool and improve the arc stability. 1%-3% of seaweed salt is added to improve the press coating property and improve the arc stability.

[0057] In order to facilitate the public to understand, the technical solutions of the present application and the technical effects thereof will be further described in detail through specific embodiments as follows: Embodiment 1:

[0058] In this embodiment, the welding core is a pure nickel welding core, and 100 parts are taken.

[0059] The mass percentages of the components of the powder of this embodiment are shown as follows:

[0060] Calcium fluoride 15 parts,

[0061] Sodium fluoroaluminate 1 part,

[0062] Calcium carbonate 18 parts,

[0063] Strontium carbonate 1 part,

[0064] Lithium carbonate 1 part,

[0065] Titanium oxide 1.5 parts,

[0066] Potassium titanate 2 parts,

[0067] Tungsten powder 5 parts,

[0068] Tungsten oxide 2.5 parts (a mixture of tungsten oxide WO3:W 18 O 49 =2:1),

[0069] Atomized ferrosilicon 2 parts,

[0070] Electrolytic manganese 2 parts,

[0071] Niobium iron 8.5 parts,

[0072] Molybdenum powder 11 parts,

[0073] Metal chromium 27 parts,

[0074] 2 parts iron powder

[0075] 0.1 parts graphite

[0076] 1 part seaweed salt. Example 2:

[0077] The welding core used in this embodiment is the same as that in Embodiment 1.

[0078] The mass percentages of each component of the powder in this embodiment are as follows:

[0079] 18 parts of calcium fluoride

[0080] Two parts of potassium fluoroaluminate,

[0081] 17 parts calcium carbonate

[0082] 1 part strontium carbonate,

[0083] 3 parts titanium dioxide

[0084] 4 parts potassium titanate

[0085] 3.5 parts tungsten powder

[0086] 2 parts of tungsten oxide (tungsten oxide WO3:W) 20 O 58 (a mixture of 3:1)

[0087] One part of atomized ferrosilicon,

[0088] Electrolytic manganese 4.5 parts,

[0089] 6 parts of niobium iron,

[0090] 9 parts of molybdenum powder

[0091] Metallic chromium 26.5 parts,

[0092] 1.5 parts iron powder

[0093] 0.3 parts graphite

[0094] 1.2 parts seaweed salt. Example 3:

[0095] The welding core used in this embodiment is the same as that in Embodiment 1.

[0096] The mass percentages of each component of the powder in this embodiment are as follows:

[0097] 16 parts of calcium fluoride

[0098] Two parts of potassium fluoroaluminate,

[0099] 15 parts calcium carbonate

[0100] 9 parts of barium carbonate

[0101] Lithium carbonate 1 part,

[0102] Titanium oxide 2.5 parts,

[0103] Potassium titanate 2.5 parts,

[0104] Tungsten powder 3 parts,

[0105] Tungsten oxide 1.5 parts (a mixture of tungsten oxide WO3: WO2 = 1:1),

[0106] Atomized ferrosilicon 1.5 parts,

[0107] Electrolytic manganese 3.5 parts,

[0108] Ferrocolumbium 7.5 parts,

[0109] Molybdenum powder 7 parts,

[0110] Metallic chromium 26 parts,

[0111] Iron powder 1 part,

[0112] Graphite 0.5 parts,

[0113] Seaweed salt 1 part.

[0114] The φ3.2mm hand welding rods made according to the embodiments 1-3 were used to carry out the cladding metal welding test, and the welding process parameters are shown in Table 2; the chemical composition and mechanical properties of the cladding metal were determined, and the details are shown in Tables 3 and 4.

[0115] Table 2 The optimized welding process parameters of the 9Ni steel electrode for alternating current welding

[0116]

[0117] Table 3 The chemical composition of the cladding metal of the 9Ni steel electrode for alternating current welding (mass percentage %)

[0118]

[0119] Table 4 The mechanical properties of the cladding metal of the 9Ni steel electrode for alternating current welding

[0120]

[0121] It can be seen that, compared with CN111590240A, the -196℃ impact energy (J) of the present application is significantly improved, and the highest of CN111590240A is 91.7 while the lowest in the present application is 110.

[0122] And the CN111590240A patent has the defect that the arc is unstable and easy to cause the base material and the weld to be not well fused, and is easy to produce pores and slag inclusions.

Claims

1. A welding electrode for 9Ni steel used in AC welding, characterized in that, The welding core and the coating are two parts, The welding core part is pure nickel welding core, and the coating part is composed of powder bonding; The components of the powder are as follows by weight: 16%-20% of fluoride; 20%-25% of carbonate; 1%-5% of titanium oxide; 2%-6% of potassium titanate; 3%-5% of tungsten powder; 1%-3% of tungsten oxide; 1%-3% of atomized ferrosilicon; 1%-6% of electrolytic manganese; 5%-10% of niobium iron; 10%-15% of molybdenum powder; 25%-28% of metallic chromium; 1%-5% of iron powder; 0.1%-0.6% of graphite; 1%-3% of seaweed salt.

2. The electrode for welding 9Ni steel for AC welding according to claim 1, characterized by The weight ratio of the coating to the electrode body is (3.5-4.5):

10.

3. The electrode for welding 9Ni steel for AC welding as set forth in claim 1, characterized in that, The tungsten oxide is WO3, W 20 O 58 W 18 O 49 WO2 4. The electrode for welding 9Ni steel for AC welding as set forth in claim 1, characterized in that The fluoride is any one or more of calcium fluoride, sodium fluoroaluminate and potassium fluoroaluminate.

5. The electrode for welding 9Ni steel for AC welding as set forth in claim 1, characterized in that, The carbonate is any one or more of calcium carbonate, strontium carbonate, lithium carbonate and barium carbonate.

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