Low-alloy corrosion-resistant welding wire and welding method thereof

Abstract

The invention discloses a low-alloy corrosion-resistant welding wire and a welding method, and relates to the technical field of welding. The low-alloy corrosion-resistant welding wire comprises the following chemical components: 0.03%-0.10% of C, 0.2%-0.3% of Si, 0.8%-2.4% of Mn, 0%-1.5% of Ni, 0.4%-1.5% of Cr, less than or equal to 0.005% of S, less than or equal to 0.005% of P, less than or equal to 0.02% of Als and Fe. The components of the welding wire do not comprise alloy elements such as Cu, Mo and Ti, a proper amount of Cr and Ni are added, and the compactness of a welding line rust layer, especially the compactness of an inner rust layer can be remarkably improved by adding Cr into the welding wire, so that the welding wire has excellent corrosion resistance; and by adding a proper amount of Ni element, grains can be refined, so that the structure is more easily converted into acicular ferrite, and the toughness of a welding seam is improved. By the adoption of the welding wire, the impact toughness of obtained weld metal reaches 80% or above of that of low-alloy corrosion-resisting steel, under the flowing accelerated corrosion condition, the corrosion step of the weld and a heat affected zone / base metal is smaller than 30 microns, the flowing medium corrosion resistance and impact resistance of a steel pipe are remarkably improved, and application and popularization of the low-alloy corrosion-resisting steel in a heat supply pipe network are promoted.

Description

Technical Field

[0001] The present application relates to the technical field of wire preparation, and particularly relates to a low-alloy corrosion-resistant wire and a welding method thereof. Background Art

[0002] The service life of steel is related not only to the performance of the steel plate, but also to the corrosion resistance of the weld. In a flowing medium, a primary battery will be formed between the weld and the heat-affected zone / base metal. If the potential at the weld is low, accelerated corrosion will occur, becoming the weak zone of the steel pipe and significantly shortening the service time.

[0003] In order to meet the corrosion performance of the weld, in the prior art, a large amount of corrosion-resistant elements such as Si, Mo, Ni, Cu, Cr, and trace harmful elements are added to the wire to improve the corrosion resistance of the wire. However, the addition of alloying elements will also reduce the comprehensive performance such as the welding process applicability of the wire and the mechanical properties of the weld. Summary of the Invention

[0004] The present application provides a low-alloy corrosion-resistant wire and a welding method thereof to solve the following technical problem: how to balance the mechanical properties and corrosion resistance of the weld.

[0005] In a first aspect, the present application provides a low-alloy corrosion-resistant wire. In terms of mass fraction, the chemical composition of the wire includes: C: 0.03% - 0.10%, Si: 0.2% - 0.3%, Mn: 0.8% - 2.4%, Ni: 0% - 1.5%, Cr: 0.6% - 1.5%, S ≤ 0.005%, P ≤ 0.005%, Als ≤ 0.02%, and Fe.

[0006] Optionally, the diameter of the low-alloy corrosion-resistant wire is 2.5 mm - 4.0 mm.

[0007] In a second aspect, the embodiment of the present application further provides a welding method, using the low-alloy corrosion-resistant wire described in the first aspect, including the following steps:

[0008] Obtain a steel plate to be welded with a thickness d;

[0009] According to the thickness d of the steel plate to be welded, determine the diameter Φ and welding heat input Q of the low-alloy corrosion-resistant steel wire;

[0010] Select the welding gap g, post-weld reinforcement height h, and reinforcement width t;

[0011] Determine the ratio ω / v of the wire feeding speed ω and the welding speed v

[0012] Based on the ω / v and the welding heat input Q, determine the welding parameters;

[0013] Weld the steel plate to be welded with the low-alloy corrosion-resistant welding wire to obtain a welded joint;

[0014] Among them, the diameter Φ of the welding wire satisfies the following relationship: 0.4d ≤ Φ ≤ 0.6d;

[0015] The ratio Q / d of the welding heat input Q to the thickness d of the steel plate to be welded is 23 kJ / cm 2 ~50 kJ / cm 2 ;

[0016] The ratio ω / v of the wire feeding speed ω and the welding speed v satisfies

[0017] Among them, n is the number of welding passes.

[0018] Optionally, the steel plate to be welded is a low-alloy corrosion-resistant steel, and its chemical composition by mass fraction includes: C: 0.03% - 0.10%, Si: 0.2% - 0.3%, Mn: 0.4% - 1.0%, S ≤ 0.005%, P ≤ 0.005%, Als ≤ 0.02%, Cr: 0.2% - 1.2%, Ni: 0% - 1.2% and Fe.

[0019] Optionally, the thickness d of the steel plate to be welded is 6 mm - 10 mm.

[0020] Optionally, the diameter Φ of the welding wire is 2.5 mm - 4.0 mm.

[0021] Optionally, the welding gap g ≤ 5 mm.

[0022] Optionally, the welding parameters include the welding speed v, the welding current I and the voltage U.

[0023] Optionally, before welding the steel plate to be welded with the low-alloy corrosion-resistant welding wire to obtain a welded joint, it further includes:

[0024] Cover the surface of the steel plate to be welded with welding flux.

[0025] Optionally, the basicity of the welding flux > 2.0.

[0026] Optionally, the weld of the welded joint has at least the following properties: the impact toughness of the weld is greater than 80% of the toughness of the base metal; under the conditions of flow-accelerated corrosion, the corrosion step of the weld and the heat-affected zone / base metal < 30 μm.

[0027] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0028] The present application discloses a low-alloy corrosion-resistant welding wire and a welding method. The chemical composition of the low-alloy corrosion-resistant welding wire includes C: 0.03% - 0.10%, Si: 0.2% - 0.3%, Mn: 0.8% - 2.4%, Ni: 0% - 1.5%, Cr: 0.4% - 1.5%, S ≤ 0.005%, P ≤ 0.005%, Als ≤ 0.02% and Fe. The wire composition does not include alloying elements such as Cu, Mo, Ti, etc., and appropriate amounts of Cr and Ni are added. Adding Cr to the wire can significantly improve the compactness of the weld rust layer, especially the inner rust layer, making it have excellent corrosion resistance; adding an appropriate amount of Ni element can refine the grains, making its structure more likely to transform into acicular ferrite, thereby improving the impact toughness of the weld. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0030] To more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 Schematic diagram of a welding method process according to some embodiments of the present application;

[0032] Figure 2 Experimental results of the welded joint obtained in Example 1 after 12 months of flow-accelerated corrosion;

[0033] Figure 3 Experimental results of the welded joint obtained in Example 2 after 12 months of flow-accelerated corrosion;

[0034] Figure 4 Experimental results of the welded joint obtained in Example 3 after 12 months of flow-accelerated corrosion;

[0035] Figure 5 Experimental results of the welded joint obtained in Comparative Example 1 after 12 months of flow-accelerated corrosion;

[0036] Figure 6 Experimental results of the welded joint obtained in Comparative Example 2 after 12 months of flow-accelerated corrosion;

[0037] Figure 7 Schematic diagram of a welding method process according to some embodiments of the present application. DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part rather than all of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0039] The various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of this application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within that range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of the range; in addition, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0040] In this text, terms such as "including" mean "including but not limited to". Relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, or B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "multiple" means two or more; "at least one kind", "at least one of the following items (pieces)" or similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces); for example, "at least one of a, b, or c", or "at least one of a, b, and c" can both mean: a, b, c, a-b (that is, a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple respectively. The "parts representation method" such as parts by weight and parts by mass represents the proportional relationship between each component. In the proportional relationships involved in this text, the parameters that need to be described by proportion should be understood as the antecedents of the proportion formula in the order of description, and the proportional numbers should be understood as the consequents of the proportion formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one by one with the proportional numbers in the proportion formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0041] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in this text can be obtained through market purchase or can be prepared by existing methods.

[0042] In a first aspect, the present application provides a low-alloy corrosion-resistant welding wire. In terms of mass fraction, the chemical composition of the welding wire includes: C: 0.03% to 0.10%, Si: 0.2% to 0.3%, Mn: 0.8% to 2.4%, Ni: 0% to 1.5%, Cr: 0.4% to 1.5%, S ≤ 0.005%, P ≤ 0.005%, Als ≤ 0.02%, and Fe.

[0043] In the above embodiment, the addition of alloying elements Cu, Mo, and Ti in the welding wire is reduced, the content of each element in the welding wire is controlled, and the welding wire is used for welding. The obtained weld has corrosion resistance and impact resistance. The specific reasons are as follows:

[0044] In this embodiment, 0.8% to 2.4% of Mn is added to the welding wire. The purpose is to have certain deoxidation and desulfurization effects during welding, prevent hot brittleness, improve the strength and hardness of the weld, and improve the toughness of the weld. When the content of Mn exceeds 2.4%, the tendency of grain growth in the weld is obvious, and the impact toughness is reduced. When the content of Mn is less than 0.8%, the aforementioned target effects cannot be exerted. Exemplarily, the content of Mn in the welding wire can be selected as 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2% or 2.4%.

[0045] In this embodiment, 0.03% to 0.1% of C is added to the welding wire. The purpose is that the carbon element and the manganese element cooperate during welding to improve the strength and hardness of the weld and increase the brittleness of the weld. When the C content is less than 0.03%, the strength and hardness of the weld during welding do not meet the requirements. When the C content exceeds 0.1%, the brittleness is relatively large, the toughness is insufficient, and it is easy to break during welding with the welding wire. Exemplarily, the content of C in the welding wire can be selected as 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%.

[0046] In this embodiment, 0.2% to 0.4% of Si is added to the welding wire. The purpose is that when silicon is used together with manganese, it can further reduce the oxygen in the weld, improve the fluidity and crack resistance of the weld. An appropriate Mn-Si ratio can reduce the melting point of the oxides formed in the molten pool, float to the surface of the weld during welding, and reduce the influence on the weld performance. When the Si content is less than 0.2%, the deoxidation effect is insufficient, reducing the impact toughness and corrosion resistance of the weld. When the Si content exceeds 0.4%, the spatter during the welding process is relatively large, affecting the welding quality. Exemplarily, the Si content in the welding wire can be selected as 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.30%, 0.32%, 0.34%, 0.36%, 0.38% or 0.4%.

[0047] In this embodiment, 0% to 1.5% of Ni is added to the welding wire. The purpose is that the grains are prone to coarsening during the melting and solidification of the welding wire. Adding an appropriate amount of Ni element can refine the grains, making its structure more likely to transform into acicular ferrite, thereby improving the corrosion resistance and toughness of the weld, and improving the ductility and plasticity of the weld. When the Ni content exceeds 1.5%, the hardenability of the weld is too large, and a high-hardness structure is easily formed, reducing the impact toughness. Exemplarily, the Ni content in the welding wire can be selected as 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%.

[0048] In this embodiment, 0.4% to 1.5% of Cr is added to the welding wire, aiming to significantly improve the compactness of the rust layer of the weld, especially the inner rust layer, enhance the corrosion resistance and oxidation resistance of the weld, and increase the hardness and wear resistance of the weld. When the Cr content is less than 0.4%, the corrosion resistance of the weld is insufficient; when the Cr content exceeds 1.5%, the grain growth of the weld is serious and the impact toughness deteriorates. Exemplarily, the Cr content in the welding wire can be selected as 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%.

[0049] As an alternative embodiment, the diameter of the low-alloy corrosion-resistant welding wire is 2.5 mm to 4.0 mm.

[0050] In the above embodiment, the size of the welding wire diameter is related to the welding efficiency. If the welding wire diameter is less than 2.5 mm, the welding wire is too thin, and the matching welding current and voltage are small. To achieve the welding purpose, the number of welding passes must be increased, which is not conducive to improving the welding efficiency; if the current and voltage are increased to improve the welding efficiency, the welding wire is likely to melt. If the welding wire diameter is greater than 4 mm, the welding wire diameter is too large, and the matching welding current and voltage are large, and situations such as burn-through are likely to occur. Exemplarily, the diameter of the welding wire can be 2.5 mm, 2.8 mm, 3.0 mm, 3.2 mm, 3.5 mm, 3.8 mm, and 4.0 mm.

[0051] In a second aspect, the embodiment of the present application further provides a welding method, using the low-alloy corrosion-resistant welding wire described in the first aspect, as Figure 1 shown, including the following steps:

[0052] S1. Obtain a steel plate to be welded with a thickness of d;

[0053] S2. Determine the diameter Φ of the low-alloy corrosion-resistant steel welding wire and the welding heat input Q according to the thickness d of the steel plate to be welded;

[0055] S3. Select the welding gap g, the post-weld reinforcement height h, and the reinforcement width t;

[0056] S4. Determine the ratio ω / v of the wire feeding speed ω and the welding speed v;

[0057] S5. Determine the welding parameters based on the ω / v and the welding heat input Q;

[0058] S6. Weld the steel plate to be welded with the low-alloy corrosion-resistant steel welding wire to obtain a welded joint;

[0059] The wire diameter Φ satisfies the following relationship: 0.4d ≤ Φ ≤ 0.6d;

[0060] The ratio Q / d of the welding heat input Q to the thickness d of the steel plate to be welded is 23 kJ / cm 2 ~50 kJ / cm 2 ;

[0061] The ratio ω / v of the wire feeding speed ω and the welding speed v satisfies

[0062] where n is the number of welding passes.

[0063] In the above embodiment, submerged arc welding is carried out using the low-alloy corrosion-resistant steel wire described in the first aspect. Since there are no alloying elements such as Cu, Mo, and Ti in the wire, only appropriate amounts of Cr and Ni elements are required. Combining with this welding method, the corrosion resistance of the steel pipe to flowing media and the impact performance can be significantly improved, and the service life of the steel pipe can be extended.

[0064] Controlling the diameter d of the wire to satisfy 0.4d ≤ Φ ≤ 0.6d with the thickness d of the steel plate to be welded helps to improve the welding efficiency and is more likely to obtain a weld joint without welding defects. When the welding diameter Φ is greater than 0.6d, welding defects such as welding leakage are likely to occur; when the welding diameter Φ is less than 0.4d, the number of welding passes needs to be increased, reducing the welding efficiency.

[0065] Controlling the ratio Q / d of the welding heat input Q to the steel plate thickness d to be 23 kJ / cm 2 ~50 kJ / cm 2 helps to more precisely control the welding process window. When Q / d is greater than 50 kJ / cm 2 , the weld grains are coarse, and the risk of welding leakage increases; when Q / d is less than 23 kJ / cm 2 , the welding efficiency is reduced and welding defects such as lack of fusion are likely to occur. Exemplarily, the ratio Q / d of the welding heat input Q to the steel plate thickness can be controlled to be 23 kJ / cm 2 , 25 kJ / cm 2 , 30 kJ / cm 2 , 35 kJ / cm 2 , 40 kJ / cm 2 , 45 kJ / cm 2 or 50 kJ / cm 2 .

[0066] Controlling the ratio ω / v of the wire feeding speed ω and the welding speed v to satisfy The reason is that during the welding process, it is necessary to satisfy the volume to be filled = the volume of wire consumption.

[0067] In the above embodiments, first, the thickness d of the steel plate to be welded is obtained according to actual requirements, and the wire diameter Φ and welding heat input Q are determined based on the thickness d of the steel plate to be welded. Among them, the purpose of selecting the wire diameter is to ensure the matching of the wire and the thickness of the steel plate to be welded, and the value of the welding heat input Q may directly affect the performance of the welded joint. Then, according to the actual welding requirements, the welding gap g, the height h of the post-weld reinforcement, and the width t of the reinforcement are determined. Secondly, the ratio ω / v of the wire feeding speed ω and the welding speed v is obtained through the calculation formula of "volume to be filled = volume of wire consumed", and this ratio directly affects the stability of the welding process and the quality of the weld seam. By reasonably adjusting this ratio, the smooth progress of the welding process and the uniformity of the weld seam can be ensured. According to the above welding heat input Q and the ratio ω / v of the wire feeding speed ω and the welding speed v, specific welding parameters can be determined, including the welding current I, the welding voltage U, and the welding speed v, etc., which ensures the controllability of the welding process and the quality of the weld seam. Finally, the steel plate to be welded is welded using the specific low-alloy corrosion-resistant steel wire and the set welding parameters in this application to obtain a welded joint that meets the requirements. This welding method ensures an optimized welding method for the low-alloy corrosion-resistant steel wire and the steel plate to be welded through precise measurement, reasonable parameter selection, and strict control of the welding process, thereby being able to obtain high-quality welded joints.

[0068] As an alternative embodiment, the steel plate to be welded is a low-alloy corrosion-resistant steel, and its chemical composition by mass fraction includes: C: 0.03% - 0.10%, Si: 0.2% - 0.3%, Mn: 0.4% - 1.0%, S ≤ 0.005%, P ≤ 0.005%, Als ≤ 0.02%, Cr: 0.2% - 1.2%, Ni: 0% - 1.2%, and Fe.

[0069] In the above embodiments, this low-alloy corrosion-resistant steel is selected for welding because the main chemical elements of this corrosion-resistant steel are basically the same as those of the wire, and it itself has certain corrosion resistance. When combined with the wire in this application for submerged arc welding, the corrosion resistance can be further improved.

[0070] As an alternative embodiment, the thickness d of the steel plate to be welded is 6 mm - 10 mm.

[0071] In the above embodiments, the reason for controlling the thickness of the steel plate to be welded to be 6 mm - 10 mm is that the thickness of common low-alloy corrosion-resistant steel pipes is usually 6 mm - 10 mm. Exemplarily, the thickness of the steel plate to be welded can be 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm.

[0072] As an alternative embodiment, the welding gap g ≤ 5 mm.

[0073] In the above-described embodiments, the reason for controlling the welding gap g ≤ 5 mm is that the welding gap is related to parameters such as the number of welding passes, wire feeding speed, and welding speed during welding. An appropriate gap ensures welding quality, improves welding efficiency, avoids welding defects, and guarantees the stability of the welded structure. Specifically, an appropriate welding gap can ensure the stable combustion of the arc during welding, making the penetration depth and width of the weld reach the requirements, thereby obtaining good welding quality; it can reduce the adjustment time during welding, ensure the continuity and stability of the welding process, avoid welding interruptions and rework caused by gap problems, and improve welding efficiency; avoid defects such as cracks and bubbles that may affect the safety and strength of the welded structure; guarantee the dimensional accuracy and shape stability of the welded structure. Exemplarily, the welding gap can be 0 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, or 5 mm. As an alternative embodiment, the welding gap is 0.

[0074] As an alternative embodiment, the welding parameters include: welding current I, welding voltage U, and welding speed v.

[0075] As an alternative embodiment, before obtaining the welded joint by welding the steel plate to be welded with the low-alloy corrosion-resistant welding wire, it further includes:

[0076] Cover the surface of the steel plate to be welded with welding flux.

[0077] In the above-described embodiments, the reason for covering the surface of the steel plate to be welded with welding flux before welding is as follows: 1) Remove the oxide film: During the welding process, an oxide film may form on the surface of the steel plate to be welded due to the action of high temperature and air, which hinders the attachment of the welding wire to the steel plate surface; after covering the steel plate to be welded with welding flux, during the welding process, the welding flux will melt and boil under the action of high temperature, thereby breaking through the oxide film and expelling the air between the welding wire and the steel plate to be welded at the same time, promoting the isolation of the surface of the steel plate to be welded from the air, and the welding wire directly adheres to the steel plate to be welded; 2) Improve wettability: The welding flux can improve the fluidity of the welding wire and the wettability of the welding wire to the surface of the steel plate to be welded during the welding process; when the welding wire touches the boiling welding flux, its fluidity increases, and it can better fill the weld to form a high-quality welded joint; 3) Protect the welding point: Prevent impurities and oxides generated during the welding process from entering the weld and affecting the welding quality; 4) Accelerate the welding process and improve welding efficiency.

[0078] As an alternative embodiment, the basicity of the welding flux > 2.0.

[0079] In the above-described embodiments, the reason for controlling the basicity of the welding flux > 2.0 is that although the selection of the welding flux does not affect the corrosion resistance of the weld, if a welding flux with a basicity below 2.0 is used, it may result in poor impact toughness of the weld.

[0080] As an alternative embodiment, the weld of the welded joint has the following properties: the impact toughness of the weld is greater than 80% of the toughness of the base metal; under the conditions of flow-accelerated corrosion, the corrosion step between the weld and the heat-affected zone / base metal is < 30 μm.

[0081] The present application will be further described below in conjunction with specific embodiments. For the experimental methods without specific conditions indicated in the following embodiments, they are generally determined according to national standards / industry standards; if there are no corresponding national standards / industry standards, they are carried out according to general international standards, conventional conditions or the conditions recommended by the manufacturer.

[0082] Example 1

[0083] This example provides a low-alloy corrosion-resistant welding wire, and its chemical composition by mass fraction includes: C: 0.05%, Si: 0.25%, Mn: 1.4%, Cr: 0.6%, Ni: 1.0%, P: 0.001%, S: 0.001%, and the balance is Fe and inevitable impurities.

[0084] Welding is carried out using the said welding wire, including the following steps:

[0085] Obtain the steel plate to be welded, and its chemical composition by mass fraction includes: C: 0.04%, Si: 0.25%, Mn: 0.45%, S: 0.001%, P: 0.002%, Cr: 0.4%, Ni: 0.6%, and the balance is Fe and inevitable impurities, and its impact energy at -20 °C is 110 J (5 mm).

[0086] The thickness d of the steel plate to be welded is 8 mm, the diameter Φ of the selected welding wire is 4 mm, and the welding heat input Q / thickness d is 36.6 kJ / cm 2 ;

[0087] Select the welding gap g to be 0, the height h of the post-weld reinforcement is 3 mm, the width t of the reinforcement is 15 mm, and the wire feeding speed and welding speed ω / v = 1.79 are calculated;

[0088] Determine the welding speed v to be 6.5 mm / s, the wire feeding speed ω to be 11.64 mm / s, the welding current to be 550 A, and the welding voltage to be 32 V according to the above values;

[0089] Cover the steel plate to be welded with the welding flux, the basicity of the selected welding flux is 2.5, and the welding flux is dried in a furnace at 350 °C for 2 hours before welding;

[0090] Weld one pass on each of the front and back sides to obtain a welded joint.

[0091] The impact performance of the welded joint was tested by taking standard impact specimens in accordance with GB / T 2650. The minimum impact energy of the welded joint at -20 °C appeared in the weld zone, with a value of 92 J, reaching 84% of the low-alloy corrosion-resistant steel, indicating good impact resistance.

[0092] A 40×20×5 mm welded joint specimen was taken and subjected to flow-accelerated corrosion testing. After 12 months, the results were as Figure 2 shown. As can be seen from Figure 2 , no corrosion steps appeared between the weld and the heat-affected zone / base metal, proving good corrosion resistance.

[0093] Example 2

[0094] This example provides a low-alloy corrosion-resistant welding wire. Its chemical composition by mass fraction includes: C: 0.05%, Si: 0.25%, Mn: 1.4%, Cr: 0.6%, Ni: 0.2%, P: 0.001%, S: 0.001%. The balance is Fe and unavoidable impurities.

[0095] Welding was carried out using the said welding wire, including the following steps:

[0096] Obtain the steel plate to be welded. Its chemical composition by mass fraction includes: C: 0.04%, Si: 0.25%, Mn: 0.5%, S: 0.001%, P: 0.002%, Cr: 0.2%, and the balance is Fe and unavoidable impurities. Its impact energy at -20 °C is 121 J (5 mm).

[0097] The thickness d of the steel plate to be welded is 6 mm, the diameter Φ of the selected welding wire is 3.2 mm, and the welding heat input Q / thickness d is 24.2 kJ / cm 2 ;

[0098] Select the welding gap g to be 0.5 mm, the post-weld reinforcement height h to be 1.5 mm, and the reinforcement width t to be 10 mm. Calculate the ratio of the wire feeding speed ω to the welding speed v, ω / v = 1.12;

[0099] Determine the welding speed v to be 8 mm / s, the wire feeding speed ω to be 8.96 mm / s, the welding current I to be 410 A, and the welding voltage U to be 28.3 V;

[0100] Cover the steel plate to be welded with welding flux. The selected welding flux basicity is 3.0. Dry the welding flux in a furnace at 350 °C for 2 hours before welding;

[0101] Weld one pass on each side, obtaining a welded joint.

[0102] Welding was carried out using the said welding wire, and the welding parameters are specifically as follows:

[0103] The impact performance of the welded joint was tested by taking standard impact specimens according to GB / T 2650. The minimum impact energy of the welded joint at -20 °C appeared in the weld zone, with a value of 99 J, reaching 82% of that of the low-alloy corrosion-resistant steel, proving its good impact resistance.

[0104] A 40×20×5 mm welded joint specimen was taken and subjected to flow-accelerated corrosion test. After 12 months, the results obtained are as Figure 3 shown. It can be seen from Figure 3 that the corrosion step between the weld and the heat-affected zone / base metal is about 10 μm, proving its good corrosion resistance.

[0105] Example 3

[0106] This example provides a low-alloy corrosion-resistant welding wire. Its chemical composition by mass fraction includes: C: 0.05%, Si: 0.25%, Mn: 1.4%, Cr: 1.2%, Ni: 0.3%, P: 0.001%, S: 0.001%, and the balance is Fe and unavoidable impurities.

[0107] Welding was carried out using the said welding wire, including the following steps:

[0108] Obtain the steel plate to be welded. Its chemical composition by mass fraction includes: C: 0.04%, Si: 0.25%, Mn: 0.5%, S: 0.001%, P: 0.002%, Cr: 1.0%, Ni: 0.2%, and the balance is Fe and unavoidable impurities. Its impact energy at -20 °C is 99 J (5 mm).

[0109] The thickness d of the steel plate to be welded is 8 mm, the diameter Φ of the selected welding wire is 3.2 mm, and the welding heat input Q / thickness d is 27.6 kJ / cm 2 ;

[0110] Select the welding gap g to be 0, the height h of the post-weld reinforcement is 3 mm, and the width t of the reinforcement is 15 mm. The ratio ω / v of the wire feeding speed ω and the welding speed v is calculated to be 1.79;

[0111] Determine the welding speed v to be 5.5 mm / s, the wire feeding speed ω to be 9.85 mm / s, the welding current I to be 450 A, and the welding voltage U to be 27 V;

[0112] Cover the steel plate to be welded with welding flux. The basicity of the selected welding flux is 2.5. Before welding, dry the welding flux in a furnace at 350 °C for 2 hours;

[0113] Use the spiral welding form to make the steel plate to be welded into a steel pipe to obtain a welded joint.

[0114] The impact performance of the welded joint was tested by taking standard impact specimens in accordance with GB / T 2650. The minimum impact energy of the welded joint at -20 °C appeared in the weld zone, with a value of 87 J, reaching 88% of that of the low-alloy corrosion-resistant steel, indicating good impact resistance.

[0115] A 40×20×5 mm welded joint specimen was taken and subjected to flow-accelerated corrosion testing. After 12 months, the results were as Figure 4 shown. As can be seen from Figure 4 , there were no corrosion steps between the weld and the heat-affected zone / base metal, proving good corrosion resistance.

[0116] Comparative Example 1

[0117] This comparative example provides a low-alloy corrosion-resistant welding wire. Its chemical composition by mass fraction includes: C: 0.05%, Si: 0.25%, Mn: 0.5%, Cr: 0.8%, P: 0.001%, S: 0.001%, and the balance is Fe and unavoidable impurities.

[0118] Welding was carried out using the said welding wire, including the following steps:

[0119] Obtain the steel plate to be welded. Its chemical composition by mass fraction includes: C: 0.04%, Si: 0.25%, Mn: 0.45%, S: 0.001%, P: 0.002%, Cr: 0.8%, and the balance is Fe and unavoidable impurities. Its standard impact energy at -20 °C is 105 J (5 mm).

[0120] The thickness d of the steel plate to be welded is 8 mm, the diameter Φ of the selected welding wire is 3.2 mm, and the welding heat input Q / thickness d is 37.5 kJ / cm 2 ;

[0121] Select the welding gap g to be 0, the post-weld reinforcement height h to be 3 mm, and the reinforcement width t to be 15 mm. Calculate the ratio of the wire feeding speed ω to the welding speed v, ω / v = 1.79;

[0122] Determine the welding speed v to be 6.2 mm / s, the wire feeding speed ω to be 11.10 mm / s, the welding current I to be 510 A, and the welding voltage U to be 36 V;

[0123] Cover the steel plate to be welded with flux. The selected flux basicity is 2.5. Before welding, dry the flux in a furnace at 350 °C for 2 hours;

[0124] Weld one pass on each side to obtain the welded joint.

[0125] The impact performance of the welded joint was tested by taking standard impact specimens according to GB / T 2650. The minimum impact energy of the welded joint at -20 °C appeared in the weld zone, with a value of 56 J, only reaching 53% of that of the low-alloy corrosion-resistant steel, indicating that its impact resistance is poor and does not meet the requirements.

[0126] A 40×20×5 mm welded joint specimen was taken for flow-accelerated corrosion testing. After 12 months, the results were as Figure 5 shown. As can be seen from Figure 5 , the corrosion step height between the weld and the heat-affected zone / base metal was approximately 53 μm, indicating that the weld has poor resistance to flow corrosion and does not meet the corrosion resistance requirements.

[0127] Comparative Example 2

[0128] This comparative example provides a low-alloy corrosion-resistant welding wire. Its chemical composition by mass fraction includes: C: 0.05%, Si: 0.25%, Mn: 1.4%, Cr: 1.5%, P: 0.001%, S: 0.001%, and the balance is Fe and unavoidable impurities.

[0129] Welding was carried out using the said welding wire, including the following steps:

[0130] Obtain the steel plate to be welded. Its chemical composition by mass fraction includes: C: 0.04%, Si: 0.25%, Mn: 0.5%, S: 0.001%, P: 0.002%, Cr: 1.0%, Ni: 1.0%, and the balance is Fe and unavoidable impurities. Its impact energy at -20 °C is 122 J (5 mm).

[0131] The thickness d of the steel plate to be welded is 8 mm. Select the diameter Φ of the welding wire to be 3.2 mm, and the welding heat input Q / thickness d is 37.5 kJ / cm 2 ;

[0132] Select the welding gap g to be 0, the post-weld reinforcement height h to be 3 mm, and the post-weld reinforcement width t to be 15 mm. Calculate the ratio of the wire feeding speed ω to the welding speed v, ω / v = 1.79;

[0133] Determine the welding speed v to be 6.2 mm / s, the wire feeding speed ω to be 11.10 mm / s, the welding current I to be 510 A, and the welding voltage U to be 36 V;

[0134] Cover the steel plate to be welded with the welding flux. The selected welding flux basicity is 1.5. Dry the welding flux in a furnace at 350 °C for 2 hours before welding;

[0135] Weld one pass on each side to obtain the welded joint.

[0136] The impact performance of the welded joint was tested by taking standard impact specimens according to GB / T 2650. The lowest impact energy of the welded joint at -20 °C appeared in the weld zone, with a value of 72 J, which was 59% of that of the low-alloy corrosion-resistant steel, indicating that its impact resistance was poor and did not meet the requirements.

[0137] A 40×20×5 mm welded joint specimen was taken and subjected to a flow-accelerated corrosion test. After 12 months, the results were as Figure 6 shown. It can be seen from Figure 6 that there was no corrosion step between the weld and the heat-affected zone / base metal, indicating good corrosion resistance of the weld.

[0138] In summary, by using the low-alloy corrosion-resistant welding wire provided in the embodiment of the present application and combining the submerged arc welding method provided in the present application, alloying elements such as Cu, Mo, and Ti do not need to be added to the welding wire, and the corrosion resistance of the welded joint to flowing media and the impact performance can be significantly improved, so that the impact toughness of the obtained weld metal reaches more than 80% of that of the low-alloy corrosion-resistant steel, and under the condition of flow-accelerated corrosion, the corrosion step between the weld and the heat-affected zone / base metal is < 30 μm.

[0139] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features claimed in the present application.

Claims

1. A low alloy corrosion resistant welding wire, wherein the chemical composition of the low alloy corrosion resistant welding wire comprises, by mass fraction, C: 0.03% to 0.10%, Si: 0.2% to 0.3%, Mn: 0.8% to 2.4%, Ni: 0% to 1.5%, Cr: 0.4% to 1.5%, S≤0.005%, P≤0.005%, Als≤0.02%, and Fe.

2. A welding method, using the low alloy corrosion resistant welding wire according to claim 1, comprising the following steps: Obtaining a steel plate to be welded having a thickness of d; Determine the diameter Φ of the low alloy corrosion resistant steel welding wire and the welding heat input Q according to the thickness d of the steel plate to be welded; Select the welding gap g, the weld excess height h and the excess width t; Determine the ratio ω / v of the wire feeding speed ω and the welding speed v; Determining welding parameters according to the ω / v and the welding heat input Q; The steel plates to be welded are welded using the low alloy corrosion resistant welding wire to obtain welded joints; The welding wire diameter Φ satisfies the following relationship: 0.4d≤Φ≤0.6d; The ratio Q / d of the welding heat input Q to the thickness d of the steel plate to be welded is 23 kJ / cm 2 ~50kJ / cm 2 ; The ratio ω / v of the wire feeding speed ω and the welding speed v satisfies in, n is the number of welding passes.

3. The welding method according to claim 2, wherein the steel plate to be welded is low alloy corrosion resistant steel, and the chemical composition thereof includes, by mass fraction: C： 0.03%~0.10%, Si: 0.2%~0.3%, Mn: 0.4%~1.0%, S≤0.005%, P≤0.005%, Als≤0.02%, Cr: 0.2%~1.2%, Ni: 0%~1.2%, the balance is Fe and unavoidable impurities.

4. According to the welding method of claim 2 or 3, the thickness d of the steel plate to be welded is 6 mm to 10 mm.

5. The welding method according to claim 2, wherein the welding wire diameter Φ is 2.5 mm to 4.0 mm. The welding method according to claim 2 , wherein the welding gap g is ≤ 5 mm.

7. The welding method according to claim 2, wherein the welding parameters include welding speed v, welding current I and voltage U.

8. The welding method according to claim 2, wherein the low alloy corrosion resistant welding wire is used to weld the steel plate to be welded, and before obtaining the welded joint, the method further comprises: The surface of the steel plate to be welded is covered with flux.

9. The welding method according to claim 8, wherein the basicity of the flux is greater than 2.

0.

10. According to the welding method of claim 2, the weld of the weld joint has at least the following properties: the impact toughness of the weld is greater than 80% of the toughness of the parent material; under flow accelerated corrosion conditions, the corrosion step between the weld and the heat affected zone / parent material is less than 30μm.

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