Metal powder core type flux-cored wire for low-temperature high manganese steel and manufacturing method

Abstract

A metal powder core type flux-cored wire for low-temperature high manganese steel comprises a stainless steel skin and flux core powder, the stainless steel skin comprises the following elements in percentage: less than or equal to 0.08% of C, less than or equal to 0.75% of Si, less than or equal to 2.00% of Mn, less than or equal to 0.030% of S, less than or equal to 0.04% of P, 18.0-20.0% of Cr, 10.0-12.0% of Ni and the balance of Fe, and the flux core powder comprises the following components in percentage by weight: 75-85% of medium carbon ferromanganese, 3-5% of rare earth ferrosilicon, 2-3% of niobium powder, 0.05-1% of ferroboron, 2-5% of rutile, 1.0-2.0% of feldspar, 0.7-1.2% of copper powder and the balance of iron. The manufacturing method comprises the steps that a stainless steel band is taken, the flux-cored powder is synchronously added on line, the stainless steel band is subjected to roller forming and diameter reducing treatment, the flux-cored wire is obtained, the diameter of the flux-cored wire is 1.0-1.4 mm, and the filling rate of the flux-cored powder is 33-38%. The method is suitable for low-temperature high manganese steel welding of gas shield welding, and is good in welding manufacturability and stable in mechanical property.

Description

Technical Field

[0001] The invention relates to a metal powder core type flux-cored welding wire for low-temperature high-manganese steel and a manufacturing method thereof. Background Art

[0002] With the surge in energy consumption, over-reliance on fossil energy such as oil and coal has caused severe air pollution. The extensive use of clean energy such as low-sulfur fuel and natural gas has become an inevitable trend. Among all the clean energy currently used, natural gas is favored by countries around the world due to its advantages of being non-toxic, colorless, odorless and non-corrosive. Natural gas transportation is one of the components of fossil energy transportation. The main forms are pipeline transportation and processing into liquefied natural gas through special liquefied natural gas transport ships. Natural gas overseas transportation mainly uses liquefied natural gas transport ships. Liquefied natural gas (LNG) is natural gas that has been compressed and cooled to its condensation point (-161.5℃) and turned into liquid. Usually, liquefied natural gas is stored in low-temperature storage tanks at -161.5 degrees Celsius and about 0.1MPa. Its main component is methane, which is transported by special ships or tank trucks and re-gasified when used. Since the 1970s, the world's liquefied natural gas production and trade volume have increased rapidly. This has further increased the demand for LNG transport ships, storage tank materials and corresponding receiving stations. At present, most LNG ships and storage tanks are made of 9Ni steel, but the price of Ni is high and fluctuates greatly, which greatly limits the development of LNG ships and storage tanks. Therefore, how to reduce the content of Ni under the premise of ensuring the performance requirements of LNG ships and storage tanks has become a new research focus. After a long period of testing, low-temperature high-manganese steel has attracted the attention of various countries. Low-temperature high-manganese steel has become an ideal structural material for the new generation of advanced clean energy storage and transportation key equipment (LNG ships and storage tanks) due to its low cost and excellent plasticity and toughness. It can also show strong adaptability in extreme low temperatures and marine corrosive environments. High manganese steel for LNG ships and storage tanks is currently the first in the world to be developed and promoted by Posco. Ultra-low temperature austenitic high manganese steel has the advantages of high performance and low cost. Low-temperature high manganese steel not only meets the requirements of LNG ships and storage tanks in strength, but also has excellent plasticity and wear resistance. Its cost is only 70% to 80% of 9Ni steel. It has outstanding economic benefits and is the most competitive material of choice for LNG ships and storage tanks in the future. Its application prospects are immeasurable and has become a research hotspot in countries around the world.

[0003] However, the welding materials matching low-temperature high-manganese steel on the market have not been perfect (according to reports, there are only welding rods, submerged arc welding materials and argon arc welding wires). Therefore, it is difficult to obtain low-temperature high-manganese steel weld metal that meets the requirements of engineering use, which hinders the promotion of low-temperature high-manganese steel. Patent application number and publication number CN202010378599.8, CN 111660035 A disclose a tungsten inert gas arc seamless flux-cored welding wire for ultra-low temperature high-manganese steel welding and a preparation method thereof. It consists of a flux core powder and a steel outer skin wrapped with the flux core powder. The filling mass of the flux core powder accounts for 25-35% of the total weight of the welding wire. The flux core powder includes the following components by weight percentage: 70-80% manganese metal, 1-2% ferrosilicon, 10-15% nickel metal, 1-2.5% high carbon ferrochrome, 0.1-0.4% titanium powder, 1-1.5% graphite, 3-5% tungsten powder, and 0.2-0.6% rare earth. High-frequency welding is used to weld at the joint to make the seamed pipe into a seamless pipe, and then annealing, drawing, straightening and cutting are carried out to prepare a tungsten inert gas arc seamless flux-cored welding wire with a diameter of 2.4 mm. The flux-cored welding wire is a relatively thick welding wire used only for tungsten inert gas arc welding. In addition, the seamless welding wire technology is used, and the welding wire cost is relatively high. Patent application number and publication number CN201710194207.0 and CN107009046A disclose a tungsten inert gas arc welding solid welding wire for ultra-low temperature high manganese steel welding. The technical scheme is: the chemical composition of the tungsten inert gas arc welding solid welding wire for ultra-low temperature high manganese steel welding is: C is 0.25-0.55wt%, Mn is 23-26wt%, Ni is 8-10wt%, W is 3-5wt%, P≤0.002wt%, S≤0.001wt%, and the balance is Fe and unavoidable impurities. The solid welding wire contains 8% to 10% Ni and 3% to 5% W, which not only makes the welding wire cost high. Patent application number and publication number CN202211377493.1 and CN115647650A disclose a low-temperature high-manganese steel submerged arc horizontal welding wire, flux and its preparation method and welding method for LNG ships. The invented welding wire includes: C, Mn, Ni, Mo, Si, S, P, Cr, W, Nb, N, Ti, Al, Zr, and the balance is iron and unavoidable impurities; the flux includes: CaF 2 、SiO 2 、Al 2 O 3, CaO, MgO, aluminum-manganese-iron alloy and rare earth fluoride. The welding wire is a solid welding wire with a diameter of 2.4 mm. The welding wire and flux invented are used for submerged arc horizontal welding of low-temperature high-manganese steel for LNG ships. Patent application number and publication number CN202110742536.0 and CN113458654A disclose an ultra-low temperature high-manganese steel welding wire, welding rod and preparation method thereof. The composition of the welding wire contains C: 0.2-0.5%, Mn: 26-32%, Si: 0.02-0.10%, Ni≤5%, Cr: 1.5-6.5%, Mo: 0.3-1.5%, S≤0.02%, P≤0.04%, and the balance contains Fe and unavoidable impurities. The welding rod is equipped with a special low-component coating on the basis of the welding wire. The prepared welding wire is a solid welding wire for fully automatic submerged arc welding of low-temperature high-manganese steel with a diameter of Φ4.0 mm. The prepared welding rod has a diameter of Φ3.2 mm and is used for manual arc welding.

[0004] Metal powder cored flux-cored welding wire is a type of flux-cored welding wire, which combines the advantages of solid welding wire and flux-cored welding wire, and is the main direction of future filler wire development. Compared with solid welding wire, metal powder cored flux-cored welding wire has a higher cross-section current density, thus bringing higher welding efficiency, and has the advantages of multi-layer and multi-pass welding without slag cleaning, which greatly improves work efficiency. Metal powder cored flux-cored welding wire has better wettability, permeability and side wall fusion performance, especially in V-shaped welds and fillet welds, which can reduce the tendency of unfused defects, make the weld surface smooth and beautiful, and the weld joint quality is high.

[0005] Moreover, currently, there are only argon arc welding wires, submerged arc welding wire fluxes and manual arc welding rods for low-temperature high-manganese steel, but there is no relevant research on gas shielded welding wires with flexible operation and high welding efficiency. Summary of the invention

[0006] The first technical problem to be solved by the present invention is to provide a metal powder cored flux-cored welding wire for low-temperature high-manganese steel, which is suitable for low-temperature high-manganese steel welding by gas shielded welding, has good welding processability and stable mechanical properties.

[0007] The second technical problem to be solved by the present invention is to provide a method for manufacturing the above-mentioned metal powder cored flux-cored welding wire for low-temperature high manganese steel. The method has simple steps, readily available raw materials, and convenient processing.

[0008] To solve the above-mentioned first technical problem, the present invention provides a metal powder cored flux-cored welding wire for low-temperature high manganese steel, comprising a 304 stainless steel sheath and flux core powder, wherein the mass percentages of the element components of the 304 stainless steel sheath are: C≤0.08%, Si≤0.75%, Mn≤2.00%, S≤0.030%, P≤0.045%, Cr=18.0-20.0%, Ni=10.0-12.0%, and the balance is Fe, and the mass percentages of the components of the flux core powder are: medium carbon ferromanganese 75%-85%, rare earth ferrosilicon 3%-5%, niobium powder 2%-3%, ferroboron 0.05%-1%, rutile 2%-5%, feldspar 1.0%-2.0%, copper powder 0.7%-1.2%, and the balance is iron powder.

[0009] For the purpose of simple explanation, the metal powder cored flux-cored welding wire for low temperature high manganese steel described in the present invention is referred to as the welding wire below.

[0010] Advantages of this welding wire:

[0011] Medium carbon ferromanganese is added to the flux core powder of the welding wire. Manganese (Mn) in the medium carbon ferromanganese in the welding wire is mainly used to achieve the content of manganese in low temperature high manganese steel. The carbon (C) in the medium carbon ferromanganese can play a deoxidation role in the welding process of the welding wire. The C element remaining in the weld metal after welding can react chemically with other alloy elements to form carbides, which plays a strengthening role and improves the strength and wear resistance of low temperature high manganese steel. The addition amount of medium carbon ferromanganese in the welding wire of the present invention is 75%-85%.

[0012] This welding wire adopts metal powder cored flux cored welding wire slag system. Rutile slag has a high solidification temperature and can improve the weldability in all positions. The appropriate amount of addition is 2-5%. If the amount is too low, the weldability in all positions will be poor. If the amount is too high, a large amount of welding slag will be generated on the weld surface.

[0013] Ferroboron is added to the flux core powder of this welding wire. Boron is added to improve the ultra-low temperature toughness of high manganese austenitic steel. Boron can play the role of "grain boundary adhesive" in low-temperature high manganese steel. The improvement of the ultra-low temperature toughness of high manganese steel by boron is because the segregation of boron at the grain boundary eliminates the segregation of manganese, thereby improving the ultra-low temperature toughness of high manganese steel, but the higher the boron content, the better. The same treatment was performed on high manganese steels with different boron contents, and their ultra-low temperature toughness was compared. It was found that under the condition of a certain boron content, the ultra-low temperature toughness of high manganese steel will first increase and then decrease with the increase of boron content. The amount of ferroboron added to the welding wire of the present invention is preferably 0.05%-1.0%.

[0014] Rare earth ferrosilicon is added to the flux core powder of the welding wire. Silicon, the main component of rare earth ferrosilicon, plays a major role in deoxidation during welding. The rare earth element cerium (Ce) in rare earth ferrosilicon plays a role in desulfurization and deoxidation in the low-temperature high manganese steel welding wire of the present invention. In addition, trace amounts of Ce can significantly refine the microstructure of low-temperature high manganese steel. The mechanism of action is that after adding Ce, in the welding molten pool during welding, large-sized, angular inclusions and long strip-shaped inclusions are modified into small-sized, spherical Ce-containing inclusions. The generated Ce-containing submicron inclusions can serve as an effective core for heterogeneous nucleation of the δ-Fe phase, refining the microstructure of the low-temperature high manganese steel. With the increase of the Ce content in the low-temperature high manganese steel, the strength, plasticity and impact toughness of the low-temperature high manganese steel all show a significant upward trend. The refinement of the microstructure of the low-temperature high manganese steel by Ce and the modification of the inclusions by Ce are the main reasons for improving the mechanical properties of the low-temperature high manganese steel. The Si content in rare earth ferrosilicon is about 40%. According to the national standard for low temperature high manganese steel, the Si content is less than 0.5%. According to the calculation of the welding wire filling rate, the addition amount of rare earth ferrosilicon in the welding wire of the present invention is preferably 3.0%-5.0%.

[0015] Niobium powder (Nb) is added to the flux core powder of the welding wire. The study on the effect of Nb microalloying on the microstructure and mechanical properties of low-temperature high-manganese steel found that the addition of Nb can improve the yield strength and tensile strength of low-temperature high-manganese steel. The main reason is that the addition of Nb hinders the growth of grains and refines the grains. The refinement of grains will increase the critical strain of strain-induced twins and inhibit strain-induced twins. In addition, Nb atoms and C atoms can form NbC precipitation. The NbC precipitation phase precipitated from low-temperature high-manganese steel will hinder the grain boundary migration and dislocation movement of low-temperature high-manganese steel, thereby significantly improving the yield strength, tensile strength and work hardening ability of low-temperature high-manganese steel. However, too high a content of Nb added will lead to a decrease in elongation. The amount of niobium powder added to the welding wire of the present invention is 2.0%-3.0%.

[0016] Feldspar is added to the flux core powder of this welding wire. Feldspar can adjust the viscosity of molten iron and slag, which is beneficial to all-position welding. However, too much addition will cause increased smoke and spatter. Therefore, the addition amount of feldspar should be controlled between 1% and 2%.

[0017] Copper powder (Cu) is added to the flux core powder of the welding wire. For low-temperature high-manganese steel, Cu, as an austenite stabilizing element, has a high solid solubility in austenite and can improve the low-temperature toughness of low-temperature high-manganese steel. The amount of copper powder added to the welding wire of the present invention is 0.7% to 1.2%.

[0018] This welding wire uses 304 stainless steel strip as the outer skin. 304 stainless steel strip contains Cr and Ni elements, so there is no need to add chromium powder (or ferrochrome) and nickel powder to the welding wire of the present invention. It is suitable for low-temperature high-manganese steel welding with gas shielded welding, with good welding processability and stable mechanical properties.

[0019] In order to solve the above second technical problem, the present invention provides a method for manufacturing a metal powder cored flux-cored welding wire for low temperature high manganese steel, comprising the following steps:

[0020] (1) Prepare the core powder in proportion;

[0021] (2) A stainless steel strip with elemental composition that meets the requirements is used as the stainless steel outer skin, and core powder is added online synchronously;

[0022] (3) The stainless steel strip after adding the flux core powder is subjected to roller forming and diameter reduction treatment to obtain a finished flux cored welding wire, the diameter of the finished flux cored welding wire is 1.0-1.4 mm, and the flux core powder filling rate is 33%-38%.

[0023] For the purpose of simple explanation, the method for manufacturing a metal powder cored flux-cored welding wire for low temperature high manganese steel described in the present invention is referred to as this method below.

[0024] Advantages of this method: This method has simple steps, readily available raw materials, and convenient processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the surface morphology of the weld of metal powder cored flux cored wire for low temperature high manganese steel.

[0026] Figure 2 It is the XRD spectrum of the deposited metal of the metal powder cored flux cored wire for low temperature high manganese steel.

[0027] Figure 3 It is a metallographic diagram of the weld metal of metal powder cored flux cored wire for low temperature high manganese steel.

[0028] Figure 4 This is a transmission electron microscope image of the weld metal of a metal powder cored flux cored wire for low temperature high manganese steel.

[0029] Figure 5 It is the tensile fracture morphology of the weld metal of the metal powder cored flux cored wire for low temperature high manganese steel DETAILED DESCRIPTION

[0030] Embodiment 1:

[0031] The invention discloses a metal powder core type flux-cored welding wire for low-temperature high-manganese steel, comprising a 304 stainless steel outer skin and flux core powder. The mass percentages of the elements of the 304 stainless steel outer skin are as follows: C≤0.08%, Si≤0.75%, Mn≤2.00%, S≤0.030%, P≤0.045%, Cr=18.0-20.0%, Ni=10.0-12.0%, and the balance is Fe. The mass percentages of the components of the flux core powder are as follows: 80% of medium carbon ferromanganese, 5% of rare earth ferrosilicon, 3% of niobium powder, 0.08% of ferroboron, 5% of rutile, 1.0% of feldspar, 1.2% of copper powder, and the balance is iron powder.

[0032] A method for manufacturing a metal powder cored flux-cored welding wire for low temperature high manganese steel comprises the following steps:

[0033] (1) Prepare the core powder in proportion;

[0034] (2) A stainless steel strip with elemental composition that meets the requirements is used as the stainless steel outer skin, and core powder is added online synchronously;

[0035] (3) The stainless steel strip after adding the flux core powder is subjected to roller forming and diameter reduction treatment to obtain a finished flux cored welding wire. The diameter of the finished flux cored welding wire is 1.2 mm, and the flux core powder filling rate is 38%.

[0036] Embodiment 2:

[0037] A metal powder core type flux-cored welding wire for low-temperature high-manganese steel comprises a 304 stainless steel outer skin and flux core powder, wherein the mass percentages of the various element components of the 304 stainless steel outer skin are: C≤0.08%, Si≤0.75%, Mn≤2.00%, S≤0.030%, P≤0.045%, Cr=18.0-20.0%, Ni=10.0-12.0%, and the balance is Fe, and the mass percentages of the various components of the flux core powder are: medium carbon ferromanganese 75%, rare earth ferrosilicon 4%, niobium powder 2.5%, ferroboron 0.05%, rutile 4%, feldspar 1.5%, copper powder 1.0%, and the balance is iron powder.

[0038] A method for manufacturing a metal powder cored flux-cored welding wire for low temperature high manganese steel comprises the following steps:

[0039] (1) Prepare the core powder in proportion;

[0040] (2) A stainless steel strip with elemental composition that meets the requirements is used as the stainless steel outer skin, and core powder is added online synchronously;

[0041] (3) The stainless steel strip after adding the flux core powder is subjected to roller forming and diameter reduction treatment to obtain a finished flux cored welding wire. The diameter of the finished flux cored welding wire is 1.0 mm, and the flux core powder filling rate is 35%.

[0042] Embodiment 3:

[0043] The invention discloses a metal powder core type flux-cored welding wire for low-temperature high-manganese steel, comprising a 304 stainless steel outer skin and flux core powder. The mass percentages of the elements of the 304 stainless steel outer skin are as follows: C≤0.08%, Si≤0.75%, Mn≤2.00%, S≤0.030%, P≤0.045%, Cr=18.0-20.0%, Ni=10.0-12.0%, and the balance is Fe. The mass percentages of the components of the flux core powder are as follows: medium carbon ferromanganese 85%, rare earth ferrosilicon 3%, niobium powder 2%, ferroboron 1%, rutile 2%, feldspar 2.0%, copper powder 0.7%, and the balance is iron powder.

[0044] A method for manufacturing a metal powder cored flux-cored welding wire for low temperature high manganese steel comprises the following steps:

[0045] (1) Prepare the core powder in proportion;

[0046] (2) A stainless steel strip with elemental composition that meets the requirements is used as the stainless steel outer skin, and core powder is added online synchronously;

[0047] (3) The stainless steel strip after adding the flux core powder is subjected to roller forming and diameter reduction treatment to obtain a finished flux cored welding wire. The diameter of the finished flux cored welding wire is 1.4 mm, and the flux core powder filling rate is 33%.

[0048] In the above embodiment, the outer skin is made of 304 stainless steel strip, and the chemical composition and properties are shown in Table 1 and Table 2.

[0049] Table 1 Chemical composition (weight %) of 304 stainless steel strip selected from metal powder cored flux cored welding wire for low temperature high manganese steel in the embodiment of the present invention

[0050] chemical composition C Si Mn S P Cr Ni Fe weight% ≤0.08 ≤0.75 ≤2.00 ≤0.030 ≤0.045 18.0-20.0 10.0-12.0 margin

[0051] Table 2 Performance of 304 stainless steel strip selected from metal powder cored flux cored welding wire for low temperature high manganese steel according to the embodiment of the present invention

[0052] performance Microhardness(HV) Tensile strength(MPa) Elongation(%) Guaranteed value 154 550 45

[0053] The chemical composition and mechanical properties of the deposited metal are shown in Tables 3 and 4.

[0054] Table 3 Chemical composition (weight %) of deposited metal of metal powder cored flux cored welding wire for low temperature high manganese steel according to the embodiment of the present invention

[0055] C Si Mn S P Cr Ni Cu V B Fe Example 1 0.54 0.50 25.8 0.007 0.015 11.1 6.2 0.46 0.12 0.0061 Bal. Example 2 0.47 0.45 22.3 0.008 0.013 11.7 6.5 0.35 0.15 0.0035 Bal. Example 3 0.50 0.32 23.8 0.006 0.014 12.1 6.7 0.23 0.22 0.066 Bal.

[0056] Table 4 Mechanical properties of deposited metal of metal powder cored flux cored welding wire for low temperature high manganese steel according to the embodiment of the present invention

[0057] Performance Indicators Yield strength(MPa) Tensile strength(MPa) Elongation(%) -196℃ Charpy impact energy (J) Example 1 476 692 45.2 68 Example 2 471 687 46.1 70 Example 3 485 700 44.3 64

[0058] The welding process parameters used in the embodiment are shown in Table 5.

[0059] Table 5 Welding process parameters of metal powder cored flux cored wire for low temperature high manganese steel according to the embodiment of the present invention

[0060]

[0061] Example 2 Characterization results see Figure 1 to Figure 5 :

[0062] Figure 1 It is the surface morphology of the weld of metal powder cored flux cored wire for low temperature high manganese steel.

[0063] Figure 2 It is the XRD spectrum of the deposited metal of the metal powder cored flux cored wire for low temperature high manganese steel.

[0064] Figure 3 It is a metallographic diagram of the weld metal of metal powder cored flux cored wire for low temperature high manganese steel.

[0065] Figure 4 This is a transmission electron microscope image of the weld metal of a metal powder cored flux cored wire for low temperature high manganese steel.

[0066] Figure 5 It is the tensile fracture morphology of the weld metal of the metal powder cored flux cored welding wire for low temperature high manganese steel.

Claims

1. A metal powder cored flux-cored welding wire for low temperature high manganese steel, characterized in that: The invention comprises a 304 stainless steel outer skin and a flux core powder. The mass percentages of the elements of the 304 stainless steel outer skin are as follows: C≤0.08%, Si≤0.75%, Mn≤2.00%, S≤0.030%, P≤0.045%, Cr=18.0-20.0%, Ni=10.0-12.0%, and the balance is Fe. The mass percentages of the components of the flux core powder are as follows: medium carbon ferromanganese 75%-85%, rare earth ferrosilicon 3%-5%, niobium powder 2%-3%, ferroboron 0.05%-1%, rutile 2%-5%, feldspar 1.0%-2.0%, copper powder 0.7%-1.2%, and the balance is iron powder.

2. The method for manufacturing a metal powder cored flux-cored welding wire for low temperature high manganese steel according to claim 1, characterized in that: The following steps are involved: (1) Prepare the core powder in proportion; (2) A stainless steel strip with elemental composition that meets the requirements is used as the stainless steel outer skin, and core powder is added online synchronously; (3) The stainless steel strip after adding the flux core powder is subjected to roller forming and diameter reduction treatment to obtain a finished flux cored welding wire, wherein the diameter of the finished flux cored welding wire is 1.0 to 1.4 mm, and the flux core powder filling rate is 33% to 38%.

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