Gas shielded solid wire rod and welding wire for improving arc stability in all-position welding

Abstract

This invention discloses a gas-shielded solid welding wire rod for improving the stability of all-position welding arcs. It contains Fe and unavoidable impurity elements, and further contains the following chemical elements in the following mass percentages: C: 0.01–0.03%; Si: 0.8–1.3%; Mn: 1.1–1.9%; S: 0.009–0.020%; P: 0.006–0.018%; Ca: 0.008–0.04%; Mg: 0.004–0.02%; Al: 0.003–0.015%; Ti: 0.08–0.25%; Cr: 0.06–0.22%; Cu: 0.45–0.75%; Ce: 0.05–0.20%. Accordingly, this invention also discloses a welding wire made using this wire rod. The welding wire of this invention can improve the stability of all-position welding arcs.

Description

Technical Field

[0001] This invention relates to a welding wire rod and welding wire, and more particularly to a gas-shielded solid welding wire rod and welding wire. Background Technology

[0002] Solid wire gas metal arc welding is a commonly used welding method in various industrial fields. It has the advantages of mature and stable technology, convenient operation, high efficiency and low cost. By matching specific welding materials and welding process specifications, it can meet the requirements of structural integrity and safety in various application scenarios, including conventional static mechanical properties, dynamic fatigue properties, corrosion resistance, and high temperature resistance.

[0003] However, welding in many industrial structures often involves complex spatial welding positions, such as all-position welding of pipelines, welding of energy medium storage tanks and spherical tanks in complex spatial positions, and vertical and overhead welding of important steel structures. In these non-flat and horizontal welding positions, the weld droplets undergo unstable transitions due to gravity, and the weld pool's spreadability deteriorates under gravity, posing a significant challenge to weld quality. Therefore, the stability of the welding arc itself and the resulting droplet transition characteristics are crucial for ensuring weld quality, and achieving arc stability through welding wire design can provide a practical solution for engineering applications.

[0004] Chinese patent document CN103962743A, published on August 6, 2014, entitled "A Welding Wire for All-Position Welding of X100 Pipeline Steel and Its Preparation Method," discloses a welding wire that achieves strength matching and toughness matching for X80 and above high-grade pipeline steel pipes through basic chemical element combination configuration, with some also possessing certain corrosion resistance. Its design mechanism primarily ensures strength through solid solution strengthening of alloying elements, and ensures appropriate low-temperature impact toughness through commonly used alloying elements to delay phase transformation temperature and high-melting-point precipitates to promote low-temperature phase transformation nucleation and grain refinement within the grain. However, it does not address how to improve arc stability.

[0005] Based on this, it is desirable to provide a gas-shielded solid welding wire that can improve the stability of the welding arc in all positions. Summary of the Invention

[0006] One of the objectives of this invention is to provide a gas-shielded solid welding wire rod for improving the stability of all-position welding arcs. It is based on the mechanism of stabilizing the arc by increasing the electron emission capability of the arc combustion zone through low ionization potential chemical elements. Through the highly correlated effects of various elements, the stability of the all-position welding arc is guaranteed within a certain range of welding wire composition design, thereby ensuring the quality of all-position welding.

[0007] To achieve the above objectives, the present invention provides a gas-shielded solid welding wire rod for improving the stability of all-position welding arcs, which contains Fe and unavoidable impurity elements, and further contains the following chemical elements in the following mass percentages:

[0008] C: 0.01~0.03%; Si: 0.8~1.3%; Mn: 1.1~1.9%; S: 0.009~0.020%; P: 0.006~0.018%; Ca: 0.008~0.04%; Mg : 0.004~0.02%; Al: 0.003~0.015%; Ti: 0.08~0.25%; Cr: 0.06~0.22%; Cu: 0.45~0.75%; Ce: 0.05~0.20%.

[0009] This invention also provides a gas-shielded solid welding wire rod for improving the stability of all-position welding arcs, wherein the mass percentage content of each chemical element is as follows:

[0010] C: 0.01–0.03%; Si: 0.8–1.3%; Mn: 1.1–1.9%; S: 0.009–0.020%; P: 0.006–0.018%; Ca: 0.008–0.04%; Mg: 0.004–0.02%; Al: 0.003–0.015%; Ti: 0.08–0.25%; Cr: 0.06–0.22%; Cu: 0.45–0.75%; Ce: 0.05–0.20%, with the balance being Fe and unavoidable impurities.

[0011] Furthermore, the mass percentage content of each chemical element in the gas-shielded solid welding wire rod of the present invention further satisfies at least one of the following:

[0012] C: 0.015~0.025%;

[0013] Si: 1.0–1.3%;

[0014] Mn: 1.5–1.6%;

[0015] S: 0.013~0.020%;

[0016] P: 0.006~0.014%;

[0017] Ca: 0.02–0.026%;

[0018] Mg: 0.012–0.02%;

[0019] Al: 0.009–0.012%;

[0020] Ti: 0.1–0.15%;

[0021] Cr: 0.09–0.16%;

[0022] Cu: 0.55–0.75%;

[0023] Ce: 0.08–0.16%.

[0024] This invention relates to welding wires with arc stability characteristics during automated circumferential welding of pipelines in all positions. Considering the significant challenges posed by the changing spatial welding position during all-position pipeline welding to the uniform formation of the weld, a continuous and stable welding arc and the resulting stable droplet transfer are required to ensure weld quality. This invention systematically analyzes the influence of relevant chemical elements on welding arc stability, particularly based on the mechanism that low-ionization-potential chemical elements can enhance the electron emission capability of the arc combustion region, thereby achieving a stable arc. Considering the highly correlated effects of various elements, the invention ensures all-position welding arc stability within a certain range of welding wire composition design, thus guaranteeing all-position welding quality. Simultaneously, optimized alloy element design ensures the basic mechanical properties of the weld metal, meeting the service requirements of all-position welded structural engineering.

[0025] Specifically, the design principles of each chemical element in this invention are as follows:

[0026] C: Carbon is an inherent non-metallic element in steel and the element that contributes the most to the strength of iron-carbon alloys. Simultaneously, carbon significantly expands the austenite region, helping to delay solid-state phase transformation to low temperatures during post-weld cooling, forming a low-temperature phase transformation structure dominated by bainite with good toughness, reducing or avoiding the appearance of blocky ferrite, and making a significant contribution to the toughness of the weld metal. However, carbon can react violently with oxygen in both the droplet and molten pool stages, which is detrimental to the stability of the welding arc. Therefore, this invention controls C to be 0.01–0.03%.

[0027] Silicon (Si) is the most important deoxidizer in welding wire, ensuring the purity of the weld metal. Deoxidation products are also easily peeled off after welding, thus guaranteeing the basic mechanical properties of the weld metal. Simultaneously, silicon significantly reduces the surface tension of the weld droplets, refining the spray transition droplets within a certain composition range, which is beneficial to the stability of the welding process. However, if the silicon content is too high, the surface tension of the droplets decreases sharply, making it difficult to form a stable droplet spray transition. Even under high-current welding conditions, unstable short-circuit transitions will occur, which is detrimental to the stability of the welding arc and the entire welding process. Therefore, this invention controls the Si content to be 0.8–1.3%.

[0028] Manganese (Mn) is an important deoxidizing and solid solution strengthening element in carbon steel and low-alloy high-strength steel welds, second only to carbon in its contribution to weld strength. Simultaneously, manganese significantly expands the austenite region; increasing the manganese content within a certain range promotes low-temperature solid-state phase transformation. Increasing the bainite content under low-temperature solid-state phase transformation conditions, reducing or even eliminating blocky ferrite, can improve weld metal toughness while ensuring weld metal strength. However, if the manganese content is too high, the strong solid solution strengthening effect can lead to a decrease in weld metal ductility and toughness. Furthermore, manganese has a high ionization potential, reducing the electron emission capability in the arc region, which is detrimental to the stability of the welding arc. Therefore, this invention controls the Mn content to be 1.1–1.9%.

[0029] Sulfur (S) is often controlled as a harmful impurity in flat or horizontal welding to avoid hot cracking and embrittlement of the weld metal. However, in this invention, sulfur can significantly improve the surface tension of the molten droplets at the tip of the welding wire, and under certain conditions, it has a significant effect on refining the droplets. Whether in low or high welding current ranges, the refined droplets can significantly improve the stability of the welding arc. However, if the sulfur content is too high, it not only causes a severe tendency for hot cracking in the weld metal but also makes it difficult to form a stable droplet-shaped transition in the arc region, resulting in unstable short-circuit transitions, which is detrimental to the stability of the welding arc and the welding process. Therefore, in this invention, sulfur is not considered an impurity element, and its content is controlled at 0.009–0.020%.

[0030] Phosphorus (P) is often strictly limited as a harmful impurity in low-alloy steel welding wires (excluding weathering steel), mainly because it can form brittle compounds with iron and cause severe segregation, leading to significant embrittlement of the weld metal and increasing its tendency to cold crack. However, in this invention, phosphorus can also significantly improve the surface tension of the molten droplets at the tip of the welding wire under certain conditions, which helps to form finer droplets, thereby achieving a relatively stable droplet transfer over a wider welding current range and improving the stability of the welding arc. Similarly, if the phosphorus content is too high, it not only causes a severe tendency for cold cracking in the weld metal, but also makes it difficult to form a round droplet transfer due to the reduced surface tension of the droplets at the tip of the welding wire, resulting in unstable short-circuit transfer over a wide current range, which is detrimental to the stability of the welding arc and the welding process. Based on this, P is not considered an impurity element in this invention, and its content is controlled at 0.006% to 0.018%.

[0031] Ca and Mg: Magnesium and calcium are both highly reactive alkaline earth metals. Their low ionization potential gives them a high electron emission capability in the welding arc region, which significantly improves the stability of welding arc combustion and droplet transfer in this invention. Calcium also serves as an additive in the refining process of welding wire steel, helping to ensure its purity. However, excessive addition of magnesium and calcium not only increases the amount of welding slag but also degrades the overall performance of the weld metal. Therefore, this invention controls the content of Ca to 0.008–0.04% and Mg to 0.004–0.02%.

[0032] Al: Aluminum is also a reactive metal commonly found in low-alloy steels. In this invention, it not only acts as a highly efficient deoxidizer but also possesses characteristics of low ionization potential and high electron emission capability, which are beneficial for improving the stability of the welding arc. However, if the aluminum content is too high, excessive aluminum solution will lead to a deterioration in the toughness of the weld metal. Based on this, the Al content is controlled at 0.003–0.015% in this invention.

[0033] Furthermore, it should be noted that since magnesium, calcium, and aluminum are all highly reactive metallic elements, they need to be added during the deoxidation and refining process of the welding wire steel to ensure the yield in the final welding wire product and to avoid unnecessary burn-off during the smelting stage. Additionally, it is preferable to add them as an aluminum-magnesium alloy, which can effectively guarantee the magnesium yield.

[0034] Titanium (Ti) plays multiple beneficial roles in low-alloy steel welding wire. In this invention, titanium itself, as a low-ionization potential element, enhances the electron emission capability of the arc region and improves the stability of the welding arc. Furthermore, it has a higher yield than the three highly reactive metals, magnesium, calcium, and aluminum, and is relatively easier to add during the smelting process. Secondly, as a chemical element with strong affinity for oxygen, carbon, and nitrogen, titanium plays a role in deoxidation, carbon fixation, and nitrogen fixation during the molten pool reaction stage, improving the purity of the weld metal and ensuring the overall performance of the weld joint. Based on this, this invention controls the Ti content to 0.08–0.25%.

[0035] Chromium (Cr) in weld metal effectively ensures strength through post-weld cooling and hardening. Simultaneously, under the condition of sufficient austenite content, an appropriate chromium content helps suppress dendritic growth in the as-cast weld, reduces overall grain size, decreases high-temperature bulk ferrite structure, and promotes the formation of low-temperature bainite structure, thus improving the overall performance of the weld metal. Based on this, the Cr content in this invention is controlled at 0.06–0.22%.

[0036] Cu, a face-centered cubic metal, significantly enhances strength when dissolved in ferrite, while also improving matrix toughness by leveraging the numerous slip systems inherent in face-centered cubic metals. Furthermore, when the copper content reaches a certain range, it exhibits significant precipitation strengthening during multi-layer, multi-pass welding thermal cycling, preventing interpass softening. Based on this, the present invention controls the Cu content to be 0.45–0.75%.

[0037] Ce: Rare earth cerium, as an active metallic element added to welding wire, primarily exerts its beneficial effects during the molten pool reaction stage. In this invention, Ce can refine the weld droplets, thereby ensuring the stability of droplet transfer over a wide welding process range, and consequently, the stability of the welding arc. Furthermore, rare earth cerium can effectively reduce the harmful effects of sulfur and phosphorus during the molten pool reaction. Simultaneously, rare earth cerium can also reduce the harmful effects of oxygen in the molten pool, purifying the weld metal and ensuring the overall performance indicators of the weld metal. Based on this, the Ce content is controlled at 0.05%–0.20% in this invention.

[0038] Furthermore, the mass percentage of unavoidable impurity elements in the gas-shielded solid welding wire rod of the present invention satisfies the following conditions: O≤0.0025%, N≤0.006%.

[0039] Furthermore, the unavoidable impurity element mass percentage content satisfies: 0 ≤ 0.002%.

[0040] The unavoidable impurities in this invention are mainly O and N. Oxygen and nitrogen negatively impact both the stability of the welding process and the final performance indicators of the weld metal; therefore, they should be kept at as low levels as possible during process operation. Specifically, increased oxygen content causes violent chemical reactions between the molten droplets and metallic elements and carbon in the arc region, generating not only a large amount of spatter but also abnormal fluctuations in the welding arc. Simultaneously, increased oxygen content reduces the surface tension of the weld droplets, hindering the formation of small, stable spherical droplets. Instead, it tends to form short-circuit transitions over a wider welding process range, reducing the stability of the welding arc and the welding process, which is detrimental to the quality of all-position welding. Furthermore, increased oxygen content leads to increased slag, and the resulting oxide inclusions cause weld metal embrittlement. Excessive nitrogen content can form nitride aggregates with related alloying elements, and excessive nitrogen dissolved in ferrite also leads to severe weld embrittlement.

[0041] Furthermore, in the gas-shielded solid welding wire rod described in this invention, its welding arc stability equivalent A st The control range is 3.1 to 4.6, where:

[0042] A st=72[Mg]+65[Ca]+16[Ti]+8[Al]-230[O]-40[C], where each chemical element is represented by the value before the percentage sign of its mass percentage content.

[0043] To ensure the stability of the welding arc and the resulting welding quality under all-position welding conditions, this invention creatively proposes a welding arc stability equivalent A, based on the mechanism that low-ionization-potential chemical elements can enhance the electron emission capability of the arc combustion region, thereby achieving a stable arc. st .

[0044] Welding arc stability equivalent A st The design primarily considers the positive correlation between several important low-ionization potential chemical elements and the welding arc stability, as well as the significant negative impact of individual elements on arc stability. It employs a sequential optimization and composite addition method during the welding wire steel smelting process to ensure the yield of beneficial chemical elements in the final welding wire product. From the perspective of improving the electron emission capability of the welding arc combustion zone and stabilizing the welding arc, magnesium, calcium, titanium, and aluminum have a strong positive correlation, while oxygen and carbon are very detrimental to the stability of the welding arc.

[0045] Under the premise of balancing the strength and toughness of the weld metal, the welding arc stability equivalent A st Control it within the range of 3.1 to 4.6. If the welding arc stability equivalent A... st If the value is too small, the welding arc stability effect will be difficult to exert. Conversely, if the welding arc stability equivalent A is too large... st If the amount is too large, it will lead to problems such as increased slag after welding, increased weld defect rate, and excessive embrittlement of weld metal due to excessive addition of welding arc stabilizing elements.

[0046] Furthermore, in the gas-shielded solid welding wire rod described in this invention, the microstructure of its deposited metal is a low-temperature phase transformation structure dominated by bainite, and the content of bulk ferrite formed during the high-temperature phase transformation process is less than 5%.

[0047] Furthermore, in the gas-shielded solid welding wire rod described in this invention, the properties of its deposited metal meet the following requirements: tensile strength ≥ 625 MPa, yield strength ≥ 550 MPa, and low-temperature impact energy KV2 ≥ 80 J at -10℃.

[0048] Another object of the present invention is to provide a gas-shielded solid welding wire, which is made from gas-shielded solid welding wire rod as described above.

[0049] In the preparation process, the wire rod is first smelted, refined, cast, hot rolled, and annealed in a vacuum electric furnace to obtain a wire rod that meets the requirements for welding wire processing and manufacturing. Then, the finished welding wire is prepared by drawing and winding the welding wire.

[0050] Furthermore, the surface of the gas-shielded solid welding wire of the present invention has a copper plating layer.

[0051] The present invention can also improve the welding arc stability by increasing the conductivity and wire feeding stability of the welding wire by plating copper on the surface of the welding wire.

[0052] During preparation, copper plating is performed after the wire drawing step.

[0053] Since the preparation process of the wire rod and welding wire in this case is not an improvement over the prior art, that is, conventional processes in the field can be used, the preparation process of the wire rod and welding wire will not be described in detail in this invention.

[0054] The gas-shielded solid welding wire rod and welding wire described in this invention have the following beneficial effects:

[0055] The gas-shielded solid welding wire rod and welding wire described in this invention break with conventional design thinking. They consider the significant impact of welding arc stability and droplet transfer stability on the quality of all-position welding. Based on the mechanism that low-ionization-potential chemical elements significantly improve the electron emission capability of the arc combustion region to obtain a stable welding arc, a welding arc stability equivalent Ast, which is highly correlated with various chemical elements, is proposed. At the same time, considering the basic mechanical properties of the weld metal, a comprehensive optimization design of the welding wire chemical composition system is carried out. Theoretically, this ensures the stability of the welding arc and droplet transfer during welding in complex spatial positions, thereby ensuring the quality of weld formation. This provides a brand-new welding material solution for welding plates in complex spatial positions and for all-position welding of pipelines.

[0056] The gas-shielded solid welding wire rod and welding wire of the present invention have moderate strength and good toughness, are widely used and have universality. They solve the problem of matching welding materials in multiple industrial fields with spatial welding requirements and achieve a breakthrough in key material technology in related fields.

[0057] The gas-shielded solid welding wire rod and welding wire of this invention achieve an organic combination of stable arc combustion, stable droplet transition, and reactive alloying of the molten pool through the control of the synergistic relationship of chemical elements. This results in stable welding quality and weld metal with good comprehensive performance, achieving the most ideal performance indicators at a lower cost, and combining economy and applicability. Detailed Implementation

[0058] The following will provide further explanation and description of the gas-shielded solid welding wire rod and welding wire of the present invention with reference to specific embodiments. However, such explanation and description do not constitute an improper limitation on the technical solution of the present invention.

[0059] Examples 1-6

[0060] Table 1 lists the mass percentage of each chemical element in the gas-shielded solid welding wire rods and welding wires of Examples 1-6.

[0061] Table 1. (wt%, balance Fe and other unavoidable impurities besides O and N)

[0062]

[0063] The gas-shielded solid welding wires described in Examples 1-6 of this invention are all prepared using the following steps:

[0064] The ingots are smelted, refined, and cast in a vacuum electric furnace to obtain ingots with the chemical composition shown in Table 1. Then, the wire rods are hot rolled, annealed, drawn, copper-plated, wound, and packaged to finally obtain finished welding wire with a diameter of 1.0 mm.

[0065] All-position welding process performance tests were conducted on the gas-shielded solid welding wires of Examples 1 to 6 to evaluate the welding arc stability, droplet size and transition stability, and all-position weld formation quality. The gas-shielded solid welding wires of Examples 1 to 6 were qualitatively evaluated using three indicators: arc stability, droplet transition stability, and overall weld formation quality.

[0066] In the performance evaluation test of pipeline all-position welding process, since the edge characteristics of multi-layer and multi-pass filler welds are not easy to observe, only the forming quality of the cap weld is evaluated. The cap welding current is 190-210A, the welding voltage is 20-22V, and the welding speed is 300-350mm / min. Appropriate welding torch oscillation is performed according to the bevel width before cap welding to ensure the bevel edge coverage and edge fusion quality of the single-pass cap weld.

[0067] The performance evaluation results of all-position welding process of gas-shielded solid welding wires in Examples 1 to 6 are shown in Table 2.

[0068] Table 2.

[0069]

[0070]

[0071] Note: In Table 2, ○ indicates excellent, ● indicates good, and × indicates poor. Excellent arc stability means welding current fluctuations are less than 3% and welding voltage fluctuations are less than 2%; good arc stability means welding current fluctuations are 3%–6% and welding voltage fluctuations are 2%–5%; poor arc stability means welding current fluctuations are greater than 6% and welding voltage fluctuations are greater than 5%.

[0072] As can be seen from Table 2 above, compared with Examples 1, 2 and 6, the overall performance of the all-position welding process of Examples 3, 4 and 5 of the present invention is better.

[0073] In addition, for the gas-shielded solid welding wires of Examples 1 to 6, the inventors also conducted welding tests on the deposited metal in accordance with the requirements of GB / T 8110-2020 standard, and evaluated the strength and impact toughness of the deposited metal, thereby assessing its mechanical adaptability during service.

[0074] Table 3 lists the mechanical properties of the deposited metal from the gas-shielded solid welding wires in Examples 1-6. During the welding tests of the solid welding wire deposited metals, the welding current was 230-250 A, the welding voltage was 24-26 V, and the welding speed was 340 mm / min.

[0075] Table 3.

[0076] 1 579 660 103 2 570 662 96 3 585 673 166 4 575 668 154 5 576 677 91 6 565 658 83

[0077] As can be seen from Table 3, the gas-shielded solid welding wires of Examples 1-6 of the present invention all meet the following mechanical properties of the deposited metal: tensile strength > 625 MPa, yield strength > 550 MPa, and low-temperature impact energy (KV) > 80 J at -10℃. Among them, Examples 3 and 4 have better mechanical properties.

[0078] It should be noted that the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0079] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A gas-shielded solid welding wire rod for improving the stability of all-position welding arcs, characterized in that, Its mass percentage content of each chemical element is as follows: C: 0.01~0.03%; Si: 0.8~1.3%; Mn: 1.1~1.9%; S：0.009~0.020%； P：0.006~0.018%； Ca: 0.008~0.04%; Mg: 0.004~0.02%; Al: 0.003~0.015%; Ti: 0.08~0.25%; Cr: 0.06~0.22%; Cu: 0.45~0.75%; Ce: 0.05~0.20%; balance Fe and unavoidable impurities; The equivalent A of the arc stability of the gas-shielded solid welding wire rod welding process st The control range is 3.1~4.6, where: In the formula, each chemical element is replaced with the value before the percentage sign of its mass percentage content.

2. The gas-shielded solid welding wire rod as described in claim 1, characterized in that, Its mass percentage content of each chemical element further satisfies at least one of the following conditions: C：0.015~0.025%； Si: 1.0~1.3%; Mn: 1.5~1.6%; S：0.013~0.020%； P：0.006~0.014%； Ca: 0.02~0.026%; Mg: 0.012~0.02%; Al：0.009~0.012%； Ti: 0.1~0.15%; Cr：0.09~0.16%； Cu: 0.55~0.75%; Ce: 0.08~0.16%.

3. The gas-shielded solid welding wire rod as described in claim 1, characterized in that, The unavoidable impurity element mass percentage content must meet the following requirements: O≤0.0025%, N≤0.006%.

4. The gas-shielded solid welding wire rod as described in claim 3, characterized in that, The mass percentage of unavoidable impurity elements must satisfy the following condition: 0 ≤ 0.002%.

5. The gas-shielded solid welding wire rod as described in claim 1, characterized in that, The microstructure of the deposited metal is mainly bainite, with bulk ferrite content of less than 5%.

6. The gas-shielded solid welding wire rod as described in claim 1, characterized in that, Its deposited metal properties meet the following requirements: tensile strength ≥625MPa, yield strength ≥550MPa, and low-temperature impact energy KV2 ≥80J at -10℃.

7. A gas-shielded solid welding wire, characterized in that, It is made from gas-shielded solid welding wire rod as described in any one of claims 1-6.

8. The gas-shielded solid welding wire as described in claim 7, characterized in that, Its surface has a copper plating layer.

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