A flux-cored wire for gas-electric vertical welding of crude oil storage tank steel that can withstand a heat input of 150 kJ / cm

Abstract

The present invention discloses a flux-cored wire for gas-electric vertical welding of crude oil storage tank steel capable of withstanding a heat input of 150 kJ / cm, belonging to the technical field of welding materials. It includes a wire outer skin and powder filled in the cavity of the wire outer skin. It is characterized in that the components of the powder include, by mass percentage: rutile 20 - 30%, sodium fluoride 1 - 3%, potassium feldspar 2 - 6%, quartz 3 - 5%, ferrosilicon 5 - 8%, electrolytic manganese 15 - 20%, nickel powder 5 - 10%, copper powder 0.5 - 3%, ferromolybdenum 2 - 3%, ferrotitanium 0.5 - 2%, tin powder 0 - 1%, rare earth oxide 1 - 3%, and the balance is iron powder and unavoidable impurities. The flux-cored wire of the present invention has excellent welding process performance. Under a welding heat input of 80 - 150 kJ / cm, the weld deposited metal meets the requirements of ReL≥490 MPa, Rm≥610 MPa, A%≥17%, and -20°C KV2≥60 J.

Description

Technical Field

[0001] The present invention belongs to the technical field of welding materials, and particularly relates to a flux-cored wire for gas-electric vertical welding of crude oil storage tank steel that can withstand a heat input of 150 kJ / cm. Background Art

[0002] With the development of China's economic society, the import volume of oil has been increasing year by year. As of 2020, China's oil import volume reached 540 million tons, and the external dependence reached 73.6%. The safety issues of crude oil transportation and storage have become one of the focuses of attention for crude oil safety. Most of the existing crude oil storage tanks use traditional high-strength ship plate steel, which can meet the strength, toughness, and welding performance requirements during general construction and use. However, these ship plates have poor corrosion resistance during service, and are difficult and costly to maintain. Especially in recent years, with the large export and transportation of high-sulfur and high-acid crude oil in the Middle East, the corrosion problem of crude oil storage tanks has become increasingly serious, greatly shortening the service life of crude oil storage tanks and even threatening the safety of crude oil storage. During the crude oil storage process, there is both hydrogen sulfide corrosion and marine environment corrosion; as an important welding material for steel plate welding, when the flux-cored wire is used for welding corrosion-resistant steel, it is required that the weld metal not only has the characteristics of high strength and high toughness, but also has good resistance to hydrogen sulfide corrosion and coastal environment corrosion. The existing flux-cored wires for crude oil storage tank welding are difficult to meet the requirements of high strength, high toughness, and good corrosion resistance, especially the mechanical properties and corrosion resistance of the weld after large heat input welding decrease; therefore, the development and application of new flux-cored wires are urgently needed.

[0003] In the prior art, for example, Chinese invention patent CN106624445A discloses a flux-cored wire for corrosion-resistant steel, and the composition of its flux core is 15-25% of titanium dioxide, 2-6% of potassium fluoride, 4-10% of silicon dioxide, 0.4-0.8% of zirconium dioxide, 3-6% of ferrotitanium alloy, 5-10% of graphite, 3-7% of boron carbide, 2-8% of silicomanganese alloy, 6-10% of nickel, 2-6% of aluminum oxide, 0.5-1.5% of ferric oxide, and 0.5-2.5% of copper, with the balance being iron powder; the filling rate of the flux core is 30-40%. This flux-cored wire contains a large amount of graphite, and the graphite will increase the C content in the weld metal and reduce the corrosion resistance of the weld metal.

[0004] Chinese invention patent CN109128573A discloses a gas shielded flux-cored wire for high heat input electro-gas welding based on the grain refinement mechanism, including a flux-cored wire outer skin and its internal powder. Among them, the flux-cored wire outer skin is made of low-carbon steel cold-rolled strip, and its component mass percentage is: C < 0.06%, Si < 0.3%, Mn < 0.8%, P < 0.02%, S < 0.01%, and the balance is Fe and inevitable impurities; the component mass percentage of the powder is: one or both of titanium dioxide or rutile: 1 - 5%, quartz sand: 2 - 6%, feldspar: 3 - 8%, magnetite: 1 - 5%, one or several of lithium oxide, sodium oxide or potassium oxide: 2 - 5%, low-carbon ferromanganese: 10 - 15%, aluminum powder: 3 - 8%, ferrotitanium: 3 - 8%, nickel powder: 2 - 6%, rare earth silicon: 2 - 6%, magnesium powder: 1 - 3%, and the rest is reduced iron powder; in the deposited metal composition of this wire, C: 0.02 - 0.06%; Si: 0.1 - 0.4%; Mn: 0.8 - 1.6%; S ≤ 0.01; P ≤ 0.02%; Ni: 0.2 - 0.8%; Cu: 0 - 0.2%; Ti: 0.02 - 0.06%; Al: 0.04 - 0.1%; B ≤ 0.001%; Mg: 0.02 - 0.06%; this wire contains more magnesium powder in the flux core, and the magnesium powder will reduce the welding stability, increase the tendency of welding hot cracks, and easily cause slag inclusions, etc.; at the same time, this wire does not contain corrosion-resistant elements such as Mo and Sn, and the pitting corrosion resistance of the weld metal is poor.

[0005] Chinese invention patent CN109128585A discloses a gas shielded flux-cored wire for high heat input electro-gas welding based on the structure homogenization mechanism, including a flux-cored wire outer skin and powder. Among them, the flux-cored wire outer skin is made of cold-rolled thin strip; the powder accounts for 15 - 25% of the total mass of the flux-cored wire, and its component mass percentage is: one or both of titanium dioxide or rutile: 1 - 3%, feldspar: 2 - 6%, water glass: 1 - 4%, lithium oxide: 1 - 4%, low-carbon ferromanganese: 4 - 10%, ferrosilicon: 4 - 8%, aluminum powder: 1 - 5%, ferromolybdenum: 2 - 5%, nickel powder: 2 - 6%, rare earth silicon: 4 - 8%, boron powder: 0.05 - 0.1%, and the rest is reduced iron powder. In the deposited metal composition of this wire, C: 0.08 - 0.12%; Si: 0.2 - 0.4%; Mn: 0.4 - 0.7%; S ≤ 0.01%; P ≤ 0.01%; Ni: 0.1 - 0.6%; Cu ≤ 0.2%; Mo: 0.07 - 0.2%; Al: 0.03 - 0.08%; B ≤ 0.001%; this flux-cored wire contains a large amount of aluminum powder, and the aluminum element will increase the tendency of welding hot cracks, and easily form slag inclusions to reduce the mechanical properties of the joint; at the same time, the deposited metal of this wire does not contain elements such as Sn and Ti, which is not conducive to the pitting corrosion resistance and toughness of the weld metal.

[0006] Chinese invention patent CN102699566A discloses a flux-cored wire for oil tanker cargo oil tanks. The deposited metal of the flux-cored wire contains, by mass percentage: C: 0.01 - 0.2%, Si: 0.1 - 1.5%, Mn: 0.5 - 2.5%, P ≤ 0.025%, S ≤ 0.012%, Ni: 0.01 - 2.5%, Cu: 0.01 - 1%, Ti: 0.01 - 0.5%, 0 ≤ Cr ≤ 1%, 0 ≤ Mo ≤ 1%, 0 ≤ W ≤ 1%, 0 ≤ B ≤ 0.1%, 0 ≤ Re ≤ 0.1%, 0 ≤ Al ≤ 0.1%, and the balance is iron and other inevitable impurities. According to requirements, the deposited metal of the flux-cored wire may also contain, by mass percentage: at least one of 0 < Sb ≤ 0.3%, 0 < Sn ≤ 0.3%, 0 < As ≤ 0.3%, 0 < Se ≤ 0.3%, 0 < Pb ≤ 0.3%. The flux-cored wire contains Al and Cr elements. The aluminum element will increase the tendency of welding hot cracks and is prone to forming slag inclusions, reducing the mechanical properties of the joint.

[0007] Therefore, while meeting the requirements for the mechanical properties of welded joints in relevant standards, specifications, etc., developing a corrosion-resistant flux-cored wire that can improve the corrosion resistance of crude oil storage tanks and extend their service life is of great significance for promoting the oil and gas construction in China. Summary of the Invention

[0008] The problem to be solved by the present invention is to provide a flux-cored wire for gas-electric vertical welding of crude oil storage tank steel that can withstand a heat input of 150 kJ / cm. The deposited metal of the flux-cored wire meets the requirements of ReL ≥ 490 MPa, Rm ≥ 610 MPa, elongation ≥ 17%, -20°C KV2 ≥ 60 J, and the annual average corrosion rate (CR) of the deposited metal in the typical corrosion environment of a corrosion-resistant crude oil storage tank steel, referring to the IMO "Inspection Guide for Corrosion-Resistant Steel for Cargo Oil Tanks of Crude Oil Tankers", is ≤ 0.9 mm; when observing the base metal and the weld with a metallurgical microscope at 100 times, no obvious corrosion steps appear, and the corrosion depth difference is less than 30 μm, which can meet the welding requirements of large crude oil storage tanks.

[0009] To solve the above technical problems, the technical solution adopted by the present invention is: a flux-cored wire for gas-electric vertical welding of crude oil storage tank steel that can withstand a heat input of 150 kJ / cm, including a wire outer skin and powder filled in the cavity of the wire outer skin. The composition of the powder, by mass percentage, includes: rutile 20 - 30%, sodium fluoride 1 - 3%, potassium feldspar 2 - 6%, quartz 3 - 5%, ferrosilicon 5 - 8%, electrolytic manganese 15 - 20%, nickel powder 5 - 10%, copper powder 0.5 - 3%, ferromolybdenum 2 - 3%, ferrotitanium 0.5 - 2%, tin powder 0 - 1%, rare earth oxide 1 - 3%, and the balance is iron powder and inevitable impurities.

[0010] Further, the diameter of the flux-cored wire is 1.6 mm.

[0011] Furthermore, the outer skin of the welding wire is made of low-carbon steel strip, and its composition by mass percentage includes: C: 0 - 0.04%, Si: 0 - 0.03%, Mn: 0.15 - 0.3%, P: 0 - 0.01%, S: 0 - 0.01%, Al: 0 - 0.03%, O: 0 - 0.005%, N: 0 - 0.003%, and the balance is Fe and inevitable impurities.

[0012] Furthermore, when the flux-cored wire is used in electro-gas vertical welding with a heat input of 80 - 150 kJ / cm, the deposited metal of the weld seam meets the requirements: ReL ≥ 490 MPa, Rm ≥ 610 MPa, A% ≥ 17%, -20°C KV2 ≥ 60 J.

[0013] Furthermore, the elements in the deposited metal of the flux-cored wire weld seam by mass percentage include C 0.04 - 0.08%, Si 0.1 - 0.7%, Mn 0.8 - 1.6%, P ≤ 0.015%, S ≤ 0.005%, Ni 0.5 - 1.5%, Cu 0.05 - 1.0%, Mo 0.1 - 0.5%, Ti 0.01 - 0.05%, Sn 0.01 - 0.3%, Ce ≤ 0.6%, Mg ≤ 0.005%, Zr ≤ 0.01%, Al ≤ 0.015%, Cr ≤ 0.05%, V ≤ 0.015%, and the balance is iron powder and inevitable impurities, and the total content of the four harmful elements Pb + As + Sb + Bi ≤ 100 ppm.

[0014] Furthermore, the weight loss Φ of the deposited metal after welding the flux-cored wire is 0.030 ≤ Φ ≤ 0.090, where Φ = (5×C + 0.5×Mn + S + P + 5×Cr) / (10×Ni + 3×Mo + 15×Cu + 10×Sn + 10×Ce + 15×Ni×Sn).

[0015] Furthermore, the annual average corrosion rate (CR) of the deposited metal of the weld seam in the corrosion environment of a typical corrosion-resistant crude oil storage tank steel is ≤ 0.9 mm.

[0016] Furthermore, the microstructure of the deposited metal of the weld seam is composed of fine acicular ferrite, bainite and ferrite, and the proportion of the acicular ferrite and the bainite is not less than 80%.

[0017] The beneficial effects of the present invention are as follows: (1) The flux-cored wire of the present invention has excellent welding process performance. Under the welding heat input of 80 - 150 kJ / cm, the deposited metal of the weld seam meets the requirements of ReL≥490 MPa, Rm≥610 MPa, A%≥17%, and -20°C KV2≥60 J. At the same time, it has good corrosion resistance. When welding with the new corrosion-resistant storage tank steel, referring to the IMO "Inspection Guide for Corrosion-Resistant Steel for Cargo Oil Tanks of Crude Oil Tankers", the annual average corrosion rate (CR) of the weld metal in the corrosion environment of typical corrosion-resistant crude oil storage tank steel ≤0.9 mm can meet the actual use requirements; at the same time, taking the base metal as a comparison, when observing under a metallurgical microscope at 100 times, no obvious corrosion steps appear between the base metal and the weld seam, and the corrosion depth difference is less than 30 μm. It can meet the technical indicators for the welding of corrosion-resistant crude oil storage tanks. (2) Through reasonable alloy composition matching, the present invention designs the composition of the flux-cored wire; for the flux core, reasonable mineral and alloy components are formulated, and by adding rare earth oxides to the flux core to transition rare earth elements to the weld seam, the weld metal can be effectively refined. (3) The flux core composition of the present invention is reasonably matched, with the advantages of small spatter, easy slag removal, and good weld formation.

[0018] The present invention will be described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the weld formation diagram of Example 1 of the present invention;

[0020] Figure 2 It is the weld formation diagram of Example 6 of the present invention;

[0021] Figure 3 It is the weld formation diagram of Comparative Example 1;

[0022] Figure 4 It is the typical microstructure morphology diagram of the deposited metal of Example 1 of the present invention;

[0023] Figure 5 It is the typical microstructure morphology diagram of the deposited metal of Example 6 of the present invention;

[0024] Figure 6 It is the typical microstructure morphology diagram of the deposited metal of Comparative Example 1;

[0025] Figure 7 It is the coupon specimen diagram of the deposited metal of Example 1 of the present invention after corrosion;

[0026] Figure 8 It is the coupon specimen diagram of the deposited metal of Example 6 of the present invention after corrosion;

[0027] Figure 9 It is the coupon specimen diagram of the deposited metal of Comparative Example 1 after corrosion. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention provides a flux-cored wire for welding the wall plates of crude oil storage tanks, comprising a wire sheath and powder filled in the cavity of the wire sheath. In the present invention, the diameter of the flux-cored wire is 1.6 mm, and the cross-section of the wire sheath of the flux-cored wire is in an O shape.

[0029] The components of the above powder include, by mass percentage: rutile 20-30%, sodium fluoride 1-3%, potassium feldspar 2-6%, quartz 3-5%, ferrosilicon 5-8%, electrolytic manganese 15-20%, nickel powder 5-10%, copper powder 0.5-3%, ferromolybdenum 2-3%, ferrotitanium 0.5-2%, tin powder 0-1%, rare earth oxide 1-3%, and the balance is iron powder and inevitable impurities.

[0030] The functions and mechanisms of the components in the powder are as follows:

[0031] Rutile: The main component of rutile is titanium dioxide. The main function of rutile is to form slag, and it can also adjust the melting point of the slag, improve the weld formation, refine the molten droplets and improve the welding process performance. The content of rutile is 20-30%, preferably 20-28%, and more preferably 22-26%.

[0032] Sodium fluoride: Its main function is to form slag, which can increase the alkalinity of the electrode, reduce the melting point and surface tension of the slag, and increase the fluidity of the slag; in addition, it can also reduce the diffusible hydrogen content in the weld and improve the impact toughness of the weld metal. The content of sodium fluoride is 1-3%, preferably 2-3%.

[0033] Potassium feldspar: The main components of potassium feldspar are K2O and SiO2, which have the functions of forming slag and stabilizing the arc. The content of potassium feldspar is 2-6%, preferably 3-6%, and more preferably 5-6%.

[0034] Quartz: The main component is silicon dioxide. Quartz can adjust the viscosity of the slag, refine the molten droplets and improve the weld formation. The content of quartz is 3-5%, preferably 4-5%.

[0035] Ferrosilicon: An alloy powder, which can transfer carbon and silicon elements to the weld. At the same time, silicon is a precipitation deoxidation element, which cooperates with manganese element and has a good deoxidation effect. The content of ferrosilicon is 5-8%, preferably 6-8%, and more preferably 7-8%.

[0036] Electrolytic manganese: An alloy powder, which can transfer carbon and manganese elements to the weld and improve the weld strength. The content of electrolytic manganese is 15-20%, preferably 17-20%, and more preferably 18-20%.

[0037] Nickel powder: Nickel is an austenite stabilizing element that can exist in the austenite and ferrite in a mutually soluble form with Fe, improving strength and low-temperature impact toughness. At the same time, Ni can also refine grains, inhibit the precipitation of grain boundary ferrite, and nickel element is also a widely used corrosion-resistant element. The content of nickel powder is 5 - 10%, preferably 8 - 10%, more preferably 9 - 9.5%.

[0038] Copper powder: Copper element has good corrosion resistance. The Cu element will increase the austenite grain size and easily cause the coarsening of the weld microstructure. The content of copper powder is 0.5 - 3%, preferably 2 - 3%, more preferably 2.5 - 3%.

[0039] Ferromolybdenum: Molybdenum is a carbide-forming element, which has an obvious effect on improving strength and refining grains, and the loss of molybdenum element during the welding process is less. The content of ferromolybdenum is 2 - 3%, preferably 2.5 - 3%.

[0040] Ferrotitanium: When Ti element is added to the submerged arc welding wire, it can form dispersed oxides and nitrides. These finely dispersed inclusions can promote the intragranular nucleation of acicular ferrite, inhibit grain boundary ferrite, effectively refine grains, and improve the low-temperature toughness of the weld. The content of ferrotitanium is 0.5 - 2%, preferably 0.8 - 1.2%, more preferably 0.95 - 1.2%.

[0041] Tin powder: The addition of tin can improve the strength, hardness and corrosion resistance of the weld at the same time. During the anodic corrosion process of tin, it continuously accumulates on the corrosion surface of the steel matrix to form a dense tetravalent tin compound film, which has the effect of blocking the anodic corrosion of the matrix and inhibiting the occurrence of pitting corrosion, greatly improving its corrosion resistance. The content of tin powder is 0 - 1%.

[0042] Rare earth oxide: mainly rare earth cerium element. Rare earth elements have the functions of desulfurizing and dephosphorizing, and their oxidation products have the function of heterogeneous nucleation. The content of rare earth is 1 - 3%.

[0043] The above-mentioned welding wire sheath is made of low-carbon steel strip, and its composition by mass percentage includes: C: 0 - 0.04%, Si: 0 - 0.03%, Mn: 0.15 - 0.3%, P: 0 - 0.01%, S: 0 - 0.01%, Al: 0 - 0.03%, O: 0 - 0.005%, N: 0 - 0.003%, and the balance is Fe and unavoidable impurities.

[0044] When the flux-cored wire is used for electro-gas vertical welding with a heat input of 80 - 150 kJ / cm, the weld deposited metal meets ReL≥490 MPa, Rm≥610 MPa, A%≥17%, -20℃ KV2≥60 J.

[0045] The elements in the flux-cored wire weld deposited metal include, by mass percentage, C 0.04~0.08%, Si 0.1~0.7%, Mn 0.8~1.6%, P≤0.015%, S≤0.005%, Ni 0.5~1.5%, Cu0.05~1.0%, Mo 0.1~0.5%, Ti0.01~0.05%, Sn 0.01~0.3%, Ce≤0.6%, Mg≤0.005%, Zr≤0.01%, Al≤0.015%, Cr≤0.05%, V≤0.015%, the balance being iron powder and unavoidable impurities, and the four harmful elements Pb +As+Sb+Bi≤100ppm.

[0046] Over time, the exterior of storage tanks is subject to erosion by rainwater and weathering, potentially rendering them unusable. This is known as tank exterior corrosion. The primary contributing factors are atmospheric oxygen and water vapor, as well as sulfur dioxide and hydrogen sulfide in rainwater. These substances form electrolyte solutions on the tank exterior, causing electrochemical reactions that accelerate corrosion. The gas phase within the tank is primarily composed of gaseous hydrogen sulfide escaping from crude oil and produced water, along with water, carbon dioxide, and other sulfides entering through valves. Within the tank, these gases condense, eventually forming an acidic liquid that corrodes the interior. This localized reaction is primarily due to galvanic coupling and electrode occlusion. This phenomenon is more pronounced in weld joints, particularly when the weld metal is poorly matched to the base metal. This can lead to accelerated corrosion of the weld metal or the base metal, causing localized stress concentrations and other issues. Therefore, the alloying element composition of the weld metal is regulated so that the weld corrosion weight loss Φ meets the requirements of 0.030≤Φ≤0.090; Φ=(5×C+0.5×Mn+S+P+5×Cr) / (10×Ni+3×Mo+15×Cu+10×Sn+10×Ce+15×Ni×Sn).

[0047] The C element in the weld metal can easily cause corrosion of the metal matrix; the Mn element is a weak carbide-forming element, which will reduce the metal's antioxidant ability; impurity elements such as S and P can easily cause intergranular corrosion; since crude oil storage tanks are often in high-salt, high-humidity environments, the Cl- therein will react with Cr to cause pitting corrosion; Ni, Mo, and Cu are all corrosion-resistant elements and are widely used in corrosion-resistant steels; an appropriate amount of Sn element can form a Sn-containing complex, the product of which can stably exist in an acidic Cl ion environment to isolate chloride ions and protect the matrix, reduce the corrosion rate, increase the self-corrosion potential, and reduce the self-corrosion current density. At the same time, Sn and Ni elements have a synergistic effect in corrosion resistance; an appropriate amount of Ce element can increase the corrosion resistance of the matrix and improve the uniformity of the matrix's corrosion resistance.

[0048] The technical solution of the present invention is described in detail below with reference to specific embodiments.

[0049] The ingredient ratios of the flux-cored wires in Examples 1-5 and Comparative Examples 1-3 are shown in the following table: 。

[0050] Under the condition of a heat input of 150 kJ / cm, the groove form and welding parameters of the surfacing welding test are shown in the following table:

[0051] 。

[0052] Under the condition of a heat input of 100 kJ / cm, the chemical compositions of the weld deposited metals of Examples 1-5 and Comparative Examples 1-3 are shown in the following table:

[0053] 。

[0054] Under the condition of a heat input of 150 kJ / cm, the groove form and welding parameters of the surfacing welding test are shown in the following table:

[0055] 。

[0056] Under the condition of a heat input of 150 kJ / cm, the chemical compositions of the weld deposited metals of Examples 6-10 and Comparative Examples 1-3 are shown in the following table:

[0057] 。

[0058] The mechanical properties and corrosion resistance of each example and comparative example are shown in the following table:

[0059] 。

[0060] As Figure 1 shown, it can be seen from the weld formation diagram of Example 1 of the present invention that the formation of the flux-cored wire is good, the weld surface is smooth without undercut; the back of the weld also has good formation ability, and the weld formation is delicate without undercut phenomenon.

[0061] As Figure 2 shown, it can be seen from the weld formation diagram of Example 6 of the present invention that the formation of the flux-cored wire is good, the weld surface is smooth without undercut; the back of the weld also has good formation ability, and the weld formation is delicate without undercut phenomenon.

[0062] As Figure 3 shown, it can be seen from the weld formation diagram of Comparative Example 1 of the present invention that the welding processability of the flux-cored wire is poor, there is an arc extinguishing phenomenon during welding, and there is undercut at the weld edge.

[0063] As Figure 4 shown is the metallographic microstructure of Example 1, Figure 5For the metallographic microstructure of Example 6, the main types of the deposited metal microstructure of the welding wires in Example 1 and Example 6 of the present invention are fine acicular ferrite (AF), bainite (GB), and a small amount of massive ferrite (PF). The sum of AF and GB accounts for no less than 80%. The size of the acicular ferrite is 5-20 μm, the size of the bainite is 15-40 μm, and the size of the massive ferrite is 40-60 μm. The acicular ferrite has an interlocking structure, which can well organize the propagation of cracks and improve the toughness of the weld. The bainite structure can enhance the strength of the weld metal and at the same time improve the toughness of the weld. The massive ferrite structure is relatively large, which is not conducive to improving the toughness and strength of the weld. Through alloy element regulation, the present invention inhibits the formation of PF in the weld microstructure. Therefore, the deposited metal of the welding wire of the present invention has excellent low-temperature toughness.

[0064] As Figure 6 shown is the metallographic microstructure of Comparative Example 1. A large amount of massive ferrite exists in the weld metal, and the massive ferrite will reduce the mechanical properties and corrosion resistance of the weld metal.

[0065] As Figure 7 shown, the surface of the corrosion coupon specimen of the deposited metal in Example 1 of the welding wire of the present invention is smooth and there are no obvious corrosion pits, indicating that the deposited metal of the welding wire of the present invention has good corrosion resistance.

[0066] As Figure 8 shown, the surface of the corrosion coupon specimen of the deposited metal in Example 6 of the welding wire of the present invention is smooth and there are no obvious corrosion pits, indicating that the deposited metal of the welding wire of the present invention has good corrosion resistance.

[0067] As Figure 9 shown, obvious corrosion marks and obvious corrosion pits exist on the surface of the corrosion coupon specimen of the deposited metal of Comparative Example 1, and the pitting corrosion phenomenon is serious, indicating that the deposited metal of the welding wire of Comparative Example 1 has poor corrosion resistance.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that it is still possible to modify the specific implementation manners of the present invention or perform equivalent replacements for some technical features. Without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A flux-cored wire for gas-electric vertical welding of crude oil storage tank steel capable of withstanding a heat input of 150 kJ / cm, comprising a wire sheath and powder filled in the cavity of the wire sheath, characterized in that, The components of the said powder, by mass percentage, include: rutile 20 - 30%, sodium fluoride 1 - 3%, potassium feldspar 2 - 6%, quartz 3 - 5%, ferrosilicon 5 - 8%, electrolytic manganese 15 - 20%, nickel powder 5 - 10%, copper powder 0.5 - 3%, ferromolybdenum 2 - 3%, ferrotitanium 0.5 - 2%, tin powder 0 - 1%, rare earth oxide 1 - 3%, and the balance is iron powder and inevitable impurities; The outer sheath of the said welding wire is made of low-carbon steel strip, When the said flux-cored wire is used in electro-gas vertical welding with a heat input of 80 - 150 kJ / cm, the elements in the weld deposited metal of the said flux-cored wire, by mass percentage, include C 0.04 - 0.08%, Si 0.1 - 0.7%, Mn 0.8 - 1.6%, P ≤ 0.015%, S ≤ 0.005%, Ni 0.5 - 1.5%, Cu 0.05 - 1.0%, Mo 0.1 - 0.5%, Ti 0.01 - 0.05%, Sn 0.01 - 0.3%, Ce ≤ 0.6%, Mg ≤ 0.005%, Zr ≤ 0.01%, Al ≤ 0.015%, Cr ≤ 0.05%, V ≤ 0.015%, and the balance is iron powder and inevitable impurities, and the total content of the four harmful elements Pb + As + Sb + Bi ≤ 100 ppm.

2. The flux-cored wire for the electro-gas vertical welding of the crude oil storage tank steel capable of withstanding a heat input of 150 kJ / cm, as claimed in claim 1, wherein The diameter of the said flux-cored wire is 1.6 mm.

3. The flux-cored wire for the electro-gas vertical welding of the steel for crude oil storage tanks capable of withstanding a heat input of 150 kJ / cm according to claim 1, wherein The components of the said outer sheath of the welding wire, by mass percentage, include: C: 0 - 0.04%, Si: 0 - 0.03%, Mn: 0.15 - 0.3%, P: 0 - 0.01%, S: 0 - 0.01%, Al: 0 - 0.03%, O: 0 - 0.005%, N: 0 - 0.003%, and the balance is Fe and inevitable impurities.

4. The flux cored wire for the electro-gas vertical welding of the crude oil storage tank steel capable of withstanding a heat input of 150 kJ / cm according to any one of claims 1 to 3, characterized in that, The weld deposited metal meets the requirements of ReL ≥ 490 MPa, Rm ≥ 610 MPa, A% ≥ 17%, and -20°C KV2 ≥ 60 J.

5. The flux-cored wire for the electro-gas vertical welding of the crude oil storage tank steel capable of withstanding a heat input of 150 kJ / cm, as claimed in claim 4, wherein The weight loss Φ of the weld deposited metal after welding with the said flux-cored wire is 0.030 ≤ Φ ≤ 0.090, where Φ = (5×C + 0.5×Mn + S + P + 5×Cr) / (10×Ni + 3×Mo + 15×Cu + 10×Sn + 10×Ce + 15×Ni×Sn).

6. The flux cored wire for the electro-gas vertical welding of the crude oil storage tank steel capable of withstanding a heat input of 150 kJ / cm according to claim 4, characterized in that, The microstructure of the said weld deposited metal is composed of fine acicular ferrite, bainite and massive ferrite.

7. The flux cored wire for the electro-gas vertical welding of the crude oil storage tank steel capable of withstanding a heat input of 150 kJ / cm according to claim 6, characterized in that, The proportion of the said acicular ferrite and the said bainite is not less than 80%.

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