Wire for welding 690mpa low weld crack sensitive pressure vessel steel and welding process thereof

Abstract

The present application provides a kind of 690MPa low welding crack sensitivity pressure vessel steel welding wire and its welding process, the component of the welding wire and its mass percentage are C:0.04-0.09%, Mn:1.1-1.5%, Si:0.4-0.8%, Cr:0.5-0.9%, Cu:0.3-0.6%, Ni:0.5-0.8%, P≤0.09%, S≤0.008%, Ti:1.1-1.6%, the rest is Fe and inevitable impurities.During welding process, the welding mode of gas shielded welding is used to weld steel plate, and the protective gas used in the welding process contains N2 gas.The present application makes N2 in protective gas and more Ti elements in welding wire generate TiN in situ under high-temperature arc heating, pinning in grain boundary, refining grain size, improving weld toughness, and meeting the requirement of low temperature toughness at-50 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel welding for low-temperature pressure vessels, in particular to a 690MPa low-welding-crack-sensitivity pressure vessel steel welding wire and a welding process thereof. BACKGROUND

[0002] With the development of national economy and society, the use of energy storage equipment in China is rapidly increasing. In order to protect national energy security, a large number of petrochemical storage equipment such as ethylene has been built in China. In order to comply with the current green development trend of lightweight large-scale infrastructure and engineering equipment, the strength of steel for low-temperature pressure vessels also needs to be improved on the basis of the existing, thereby reducing the use of steel while ensuring the carrying capacity. After the strength is changed, the corresponding supporting welding material must be changed, because welding is an extremely important step in the construction process of storage tanks and other facilities, and the selection of appropriate welding material plays an important role in the safety and economy of storage tank construction.

[0003] The existing low-temperature pressure vessel steel welding material in the market cannot match the new strength level of bridge steel.

[0004] Patent publication No. CN113145991A "A yield strength of 690MPa weathering steel gas shielded welding process" through the tensile strength of 880MPa of the gas shielded welding wire with the component ratio of C0.065-0.067%, Mn1.35-1.5%, Si0.35-0.37%, Cr0.33-0.36%, Cu0.08-0.1%, Ni2.71-2.95%, S0.001-0.002%, P0.001-0.002%, adopts a 60°X type groove; 20%Ar+80%CO2 mixed protective gas, the weld impact energy after welding is 355-270J at-20℃.

[0005] Patent publication No. CN110625294A "A high-strength high-toughness weathering steel gas shielded welding wire" its main component ratio is C: 0.03-0.11, Mn: 0.7-0.15%, Si: 0.25-0.9%, Ni: 0.55-1.4%, Cu: 0.15-0.4%, Ti: 0.05-0.18%, S<0.015%, P<0.02%. A 550MPa high-strength high-toughness weathering steel welding wire is prepared by the component ratio. The welding wire has excellent welding process performance, stable welding arc, small spatter, and beautiful forming without air holes.

[0006] Patent publication number CN106334883A "A high-strength and high-toughness gas shielded flux-cored wire for bridge steel" provides a welding material suitable for 500MPa high-strength grade bridge steel, especially Q500qE bridge steel plate welding. The invention includes a sheath and a sheath-wrapped core, and the main components of the core are rutile in a proportion of 30-50%. The remaining components include feldspar, quartz, silicon-manganese alloy, metallic manganese, magnesium powder, nickel powder, etc.

[0007] Patent number CN107009047A "A high-strength steel gas shielded arc welding solid core welding wire" provides a composition ratio: C element 0.06-0.12%, Si element 0.6-1%, Mn element 1.5-2%, P element <0.025%, S element <0.2%, Ni element 0.1-0.6%, Cr element 0.6-0.8%, Cu element <0.25%, V element 0.02-0.1%, Ti element 0.08-0.25%, B element 0.002-0.008%, according to the composition ratio A kind of high-strength steel gas shielded welding wire with excellent weldability, wide process window and low production cost is prepared.

[0008] Patent number 112719692A "A 900MPa high-strength steel gas shielded solid core welding wire and its preparation method" by component ratio C element 0.04-0.06%, Si element 0.2-0.3%, Mn element 1.3-1.5%, Ni element 3-3.4%, Cr element 0.4-0.6%, Mo element 0.5-0.7%, Ti element 0.04-0.1%, P <0.006, S <0.005%, a gas shielded welding wire is prepared, which is cast into continuous casting billet by desulfurized molten iron, and then rolled into a wire rod with a diameter of 0.8-1.6mm. Wire rod, wire rod is coated with boric sand after pickling and descaling, and then subjected to rough drawing and tempering, and then plated with copper to form a 0.8-1.6mm welding wire.

[0009] Patent number CN111975244A "A 650MPa tensile strength CO2 gas shielded welding wire and wire rod for unpainted weathering steel bridge" uses a composition ratio of C element 0.04-0.09%, Si element 0.55-0.85%, Mn element 1.7-2.1%, P element 0.005%, S element 0.015%, Cr, 0.46-0.65%, Ni element 1.1-1.8%, Cu element 0.15-0.38%, Ti element 0.1-0.2%, B element 0.003-0.005%, Al element <0.015%, Zr <0.045%, Ce <0.003%. A gas shielded welding wire with excellent crack resistance and high strength and toughness is prepared.

[0010] Patent No. 112935627A "A flux-cored wire for welding of fire-resistant weathering steel" by component ratio C element 0.04-0.11%, Mn element 0.8-1.55%, Si element 0.3-0.75%, P element 0.01-0.02%, S element <0.02%, Cr element 0.05-0.2%, Ni element 0.8-1.25%, Mo element 0.25-0.5%, Cu element 0.1-0.35%, V element 0.025-0.07%, Ti element 0.03-0.15%. A yield strength greater than 460MPa of the core gas shielded welding wire can have excellent performance such as fire resistance, high temperature resistance and weather resistance, and can be applied to high-rise buildings.

[0011] In the above disclosed patent, there is no welding material that can meet the strength level of 690MPa and meet the low temperature toughness of-50℃, and most of them use expensive alloy elements such as nickel to increase the cost of welding wire. And this way of refining grain size to improve low temperature toughness by in-situ generating TiN second phase particles through oxide metallurgy is almost blank. Therefore, in order to meet the market demand, it is necessary to develop new welding materials that can meet the requirements, and can improve the low temperature toughness of the weld of the low temperature pressure vessel while ensuring the strength. SUMMARY

[0012] According to the above technical problem, a 690MPa low welding crack sensitivity pressure vessel steel welding wire and its welding process are provided. The present application mainly uses the principle of oxide metallurgy to make N2 in the protective gas and more Ti elements in the welding wire in-situ generate TiN under high temperature arc heating, pin in the grain boundary, refine the grain size and improve the weld toughness, so that the welding wire can meet the requirements in strength, toughness, low temperature toughness and other basic properties, and can meet the requirements of industrial production in production cost and process.

[0013] The technical means adopted by the present application are as follows:

[0014] A 690MPa low welding crack sensitivity pressure vessel steel welding wire, the composition and its mass percentage of the welding wire are as follows:

[0015] C: 0.04%-0.09%, Mn: 1.1%-1.5%, Si: 0.4%-0.8%, Cr: 0.5%-0.9%, Cu: 0.3%-0.6%, Ni: 0.5%-0.8%, P≤0.09%, S≤0.008%, Ti: 1.1%-1.6%, the rest is Fe and inevitable impurities.

[0016] Its preparation method is: through the component proportioning, removing sulfur in molten iron smelting process, then through a series of processes such as intermediate frequency induction furnace steelmaking-LF furnace refining-casting-rolling to form the wire rod. The welding wire.

[0017] Element proportioning:

[0018] C: can improve the strength of steel, but the increase of C content will reduce the toughness of the weld and increase the welding crack sensitivity, therefore it is controlled in the range of 0.04%-0.09%.

[0019] Mn: in addition to being able to remove S and deoxidize, it can also improve the strength of the weld through solid solution strengthening and promote the formation of needle-shaped ferrite with good strength and toughness in the weld, therefore Mn: 1.1%-1.5%.

[0020] Si: can deoxidize and improve the strength of the weld, but too much Si will reduce the toughness of the weld and increase the welding spatter, therefore Si: 0.4%-0.8%.

[0021] Cr: is one of the main elements to improve the corrosion resistance of steel and weld, which can form a dense oxide film on the surface of steel to prevent further intrusion of corrosive media. In order to improve the corrosion resistance of the welded joint in the atmospheric environment, the proportion of Cr element is increased compared with the conventional welding wire composition. In addition, Cr can also promote the formation of needle-shaped ferrite in the weld and improve the strength of the weld, therefore Cr: 0.5%-0.9%.

[0022] Cu: has good corrosion resistance, especially in steel, which can effectively protect iron elements, and can also produce precipitation strengthening effect through the phase change process of iron to improve the strength and toughness of the weld. But copper element is easy to produce "hot brittleness", so Ni element needs to be added to prevent this phenomenon, therefore Cu: 0.3%-0.6%.

[0023] Ni: can greatly improve the low temperature toughness of the weld, reduce the ductile-brittle transition temperature, and also reduce the self-corrosion potential of the weld to improve the corrosion resistance of the weld. But the price of Ni is high, and its content should be limited for cost consideration, therefore Ni: 0.5%-0.8%.

[0024] Ti: can form compounds with non-metallic elements in the weld as nucleation points for needle-shaped ferrite, promote the formation of needle-shaped ferrite, and thus improve the toughness of the weld, therefore Ti: 1.1%-1.6%.

[0025] S, P elements are harmful elements in the weld, which can easily lead to the generation of welding hot cracks and reduce the toughness of the weld, but a small amount of P element can help to improve the corrosion resistance of the weld. Therefore, the content of S is controlled to be ≤0.008, and the content of P element is controlled to be ≤0.09.

[0026] The application also discloses a welding process of the 690MPa low welding crack sensitive pressure container steel.

[0027] Preferably, the protective gas is composed of Ar gas and N2 gas, the volume fraction of the N2 gas is 5%-9%, and the balance is Ar gas. The Ar gas can hinder the oxygen element in the air from entering the weld, the N2 gas can provide N element when forming fine dispersed TiN, and can also isolate the weld from the contact of external air to play a protective role. The high content of Ti element in the welding wire can generate uniformly dispersed TiN in situ through redox reaction under the action of high-temperature arc and the protection of N2. The TiN particles can hinder the growth of austenite grains and the expansion of coarse grain zone at a higher temperature, refine the grain size, and play a fine-grain strengthening role. In addition, this in-situ generated oxide can greatly ensure uniformity.

[0028] Preferably, the welding process parameters of the gas shielded welding are as follows: welding current 250-320A, welding voltage 25-30V, protective gas flow rate 16-25L / min, and interlayer temperature during welding 100-150℃.

[0029] Preferably, before welding, the welding sides of the two steel plates are processed, so that after the butt joint of the two steel plates is fixed, the groove is X-shaped, and the angles of the upper part and the lower part of the groove are both 60°. The groove is carefully cleaned to remove oil stains, rust and other impurities.

[0030] Preferably, the sizes of the upper part and the lower part of the groove are different, forming an upper-lower asymmetric structure, so that more welding is performed at the end with a larger opening, thereby reducing the welding stress.

[0031] Compared with the prior art, the application has the following advantages:

[0032] The welding process using the welding wire provided by the present application obtains a weld with tensile strength greater than 690MPa, low temperature impact energy at-50℃ greater than 100J, excellent low temperature toughness, small spatter during welding, and good weldability. The welding wire can be used for the engineering construction of a new generation of 690MPa low weld crack sensitive pressure vessel steel, ensuring good weldability during welding and low temperature toughness of the welded joint after use, and safety during long-term use in low temperature environment in the north. It lays a solid foundation for the development of China's energy security.

[0033] Based on the above reasons, the present application can be widely popularized in the field of low temperature pressure vessel steel welding. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 The present application is a schematic diagram of the groove structure in the specific embodiment. DETAILED DESCRIPTION

[0036] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0038] As shown in Figure 1 A welding wire for 690MPa low weld crack sensitive pressure vessel steel, the composition and mass percentage of the welding wire are as follows:

[0039] C: 0.04%-0.09%, Mn: 1.1%-1.5%, Si: 0.4%-0.8%, Cr: 0.5%-0.9%, Cu: 0.3%-0.6%, Ni: 0.5%-0.8%, P≤0.09%, S≤0.008%, Ti: 1.1%-1.6%, and the rest is Fe and inevitable impurities.

[0040] The preparation method is as follows: through the component proportioning, sulfur is removed in the molten iron smelting process, and then through a series of processes such as intermediate frequency induction furnace steelmaking, LF furnace refining, casting and rolling, 5.5 mm diameter wire rod is formed. The wire rod is made into The welding wire.

[0041] A welding process of a 690MPa low welding crack sensitivity pressure vessel steel, the steel plate is welded by adopting the welding mode of gas shielded welding, the welding wire containing the above components is used in the welding process, and the protective gas used in the welding process contains N2 gas.

[0042] The protective gas is composed of Ar gas and N2 gas, the volume fraction of N2 is 5%-9%, and the rest is Ar gas. Ar gas can hinder the oxygen element in the air from entering the weld, N2 can provide N element when forming fine dispersed TiN, and also can isolate the weld from the outside air to play a protective role. The high content of Ti element in the welding wire can generate dispersed and uniformly distributed TiN in situ under the action of high temperature arc and the protection of N2. TiN particles can hinder the growth of austenite grains and the expansion of coarse grain zone at high temperature, refine the grain size, and play a fine grain strengthening role. And this in-situ generated oxide can greatly ensure uniformity.

[0043] The welding process parameters of the gas shielded welding are as follows: welding current 250-320 A, welding voltage 25-30 V, protective gas flow rate 16-25 L / min, and interlayer temperature during welding 100-150℃.

[0044] Before the two steel plates are welded, the welding sides of the two steel plates are processed, so that after the butt joint of the two steel plates is fixed, the bevel is X-shaped, the angles α of the upper and lower parts of the bevel are both 60°, and the root face L of the bevel is 2 mm. The bevel near the bevel is carefully cleaned to remove oil stains, rust and other impurities. The upper and lower parts of the bevel are different in size, forming an upper and lower asymmetric structure, so that more welding is performed at the end with a larger opening, thereby reducing the welding stress.

[0045] The following eight examples are used to illustrate the present embodiment in detail, the components of the welding wire and the percentage of the eight examples are shown in Table 1, the welding process parameters are shown in Table 2, and the weld performance is shown in Table 3.

[0046] Table 1: Components of the welding wire and the percentage

[0047]

[0048] Table 2: Welding parameters

[0049]

[0050] Table 3: Mechanical properties of the weld

[0051]

[0052] As can be clearly seen from Table 3, the welding wire provided by the present embodiment and the weld prepared by using the welding wire have a tensile strength greater than 690 MPa, and a low-temperature impact energy at -50℃ greater than 100 J, and excellent low-temperature toughness.

[0053] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A welding wire for a 690 MPa low weld crack sensitivity pressure vessel steel, characterized by, The component of the welding wire and its mass percentage are as follows: C: 0.04%-0.09%, Mn: 1.1%-1.5%, Si: 0.4%-0.8%, Cr: 0.5%-0.9%, Cu: 0.3%-0.6%, Ni: 0.5%-0.8%, P≤0.09%, S≤0.008%, Ti: 1.1%-1.6%, and the rest is Fe and inevitable impurity elements; The steel plates are welded by adopting the welding mode of gas shielded welding, the welding wire is used in the welding process, and the protective gas used in the welding process contains N2; The protective gas is composed of Ar and N2, the volume fraction of N2 is 5%-9%, and the rest is Ar; The N2 in the protective gas and the Ti element in the welding wire are oxidized and reduced in situ to generate uniformly distributed TiN under high-temperature arc heating, which is pinned on the grain boundary and refines the grain size.

2. A welding process for a 690 MPa low weld crack sensitive pressure vessel steel according to claim 1, characterized in that, The welding process parameters of the gas shielded welding are as follows: welding current 250-320 A, welding voltage 25-30 V, protective gas flow rate 16-25 L / min, and interlayer temperature in the welding process 100-150 DEG C.

3. The welding process of a 690 MPa low weld crack sensitive pressure vessel steel according to claim 1, characterized in that, Before the two steel plates are welded, the welding sides of the two steel plates are processed, so that after the butt joint of the two steel plates is fixed, the bevels are X-shaped, and the angles of the upper and lower parts of the bevels are both 60 DEG.

4. A welding process for a 690 MPa low weld crack sensitive pressure vessel steel according to claim 3, characterized in that, The sizes of the upper and lower parts of the bevels are different.

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