Coal mine hydraulic support gas shielded welding wire with strength higher than 900 MPa and preparation method thereof

Abstract

This invention provides a gas-shielded welding wire for coal mine hydraulic supports with a strength higher than 900 MPa and its preparation method. The chemical composition of the gas-shielded welding wire, by mass percentage, includes: C: 0.03~0.06, Si: 0.51~0.70, Mn: 1.35~1.64, P≤0.010, S≤0.005, Cr: 0.20~0.38, Ni: 2.35~2.65, Cu: 0~0.09, Mo: 0.45~0.70, Ti: 0.015~0.030, Nb: 0.025~0.035, Ce: 0.002~0.006, B: 0.0005~0.0012, O≤0.004, N≤0.006, with the balance being Fe and other unavoidable impurities. The beneficial effects of the present invention are: (1) By rationally designing the chemical composition, the yield strength of the weld metal is ≥820 MPa, the tensile strength is ≥900 MPa, the elongation is ≥21%, and the low-temperature impact toughness at -40℃ is ≥75 J; (2) After welding, the inclusions in the weld are dispersed and refined, and the structure is mainly composed of refined acicular ferrite rather than bainite and martensite, resulting in excellent weld strength and toughness; (3) By optimizing the composition ratio of the welding wire and developing a stable welding wire preparation process based on the composition, the comprehensive performance of the weld of the high-strength coal mine hydraulic support is taken into account.

Description

Technical Field

[0001] This invention belongs to the field of high-strength welding materials for hydraulic supports in coal mines, specifically relating to a gas-shielded welding wire compatible with Q800M~Q890M steel for hydraulic supports in coal mines and its preparation method. The weld metal has a yield strength ≥820 MPa, tensile strength ≥900 MPa, elongation ≥21%, and low-temperature impact toughness ≥75 J at -40℃. Background Technology

[0002] Hydraulic supports in coal mines are the core support equipment for fully mechanized mining faces, primarily responsible for roof support, maintaining the mining area space, and moving equipment. Their structural stability directly determines the mine's safety and production efficiency—under complex underground geological conditions, the supports must withstand periodic mine pressure impacts and roof subsidence loads, while also meeting dynamic operational requirements such as rapid support movement and adaptive posture adjustment. With the proportion of thick coal seam mining in my country increasing to over 45%, traditional Q550 grade steel is no longer sufficient to meet the material strength, lightweight, and impact resistance requirements of 10-meter-high mining supports. Q800M~Q890M steel, with its high tensile strength and excellent performance (over 120 J impact energy at -40℃), has gained widespread attention in the stiffening plates, lugs, and valve blocks of hydraulic supports in coal mines. Compared to traditional steel, it reduces structural weight by up to 18% under the same load-bearing conditions, lowering energy consumption in underground transportation. With a 45% increase in yield strength, the working resistance of the support can exceed 20,000 kN, and the support height can be extended to 12 meters, meeting the needs of efficient mining of extra-thick coal seams of 8-10 meters. Due to structural complexity or confined space, these areas generally employ gas-shielded welding. However, due to the increased strength of the steel, welding defects in gas-shielded welding are frequent, severely limiting the widespread application of this strength level of steel. The core issue lies in the lagging development of the welding wire matching system. Mainstream welding materials on the market struggle to achieve a balance between the strength and toughness of the Q800M~Q890M base material and excellent weld metallurgical quality, making the joint a high-risk area for structural failure.

[0003] Many domestic welding material manufacturers and research institutes have also conducted a lot of research work in the early stages of the development of high-strength gas shielded welding wire.

[0004] The invention patent with publication number CN119177408A discloses an 1100MPa grade ultra-high strength wire rod and its preparation method. Its chemical composition is controlled by the following requirements in mass percentage (wt.%): C: 0.065~0.18, Si: 1.13~1.82, Mn: 1.59~1.97, Cr: 0.41~0.98, Ni: 3.25~4.62, Cu: 0~0.12, Mo: 0.41~0.98, Ti: 0.04~0.10, V: 0~0.5. The welding wire steel wire rod with this composition system is expected to be prepared into a high-strength gas shielded welding wire after further drawing and copper plating processes. The wire rod contains a large amount of deoxidizing elements Si, Ti, and Mn, which can effectively ensure the deoxidation performance of the welding wire. However, the high addition of Si and Cr in the welding wire makes it easy to generate a large number of large-size M / A components during the welding process. The hydraulic support needs to withstand dynamic loads during service, and the large-size M / A components can easily become crack initiation sites, resulting in poor impact toughness and fatigue performance of the weld metal.

[0005] Invention patent CN103331529B discloses a mixed gas-shielded welding wire with a tensile strength ≥1100MPa and its application method. Its chemical composition, by mass percentage (wt.%), is controlled as follows: C: 0.07~0.22, Si: 0.60~0.90, Mn: 1.40~1.80, Ni: 1.50~2.30, Cr: 0.15~0.65, Mo: 0.3 With the following composition ratios: Cu: 0.10–0.30, Ti: 0.10–0.15, B: 0.002–0.005, V: 0.10–0.50, P≤0.010, S≤0.006, Als≤0.01, N≤0.002, O≤0.002, this welding wire achieves a weld microstructure dominated by fine bainite and high-density low-carbon martensite, resulting in high strength. However, the high C, B, and V content in this welding wire leads to a high hardening tendency and a greater susceptibility to welding cracks. Furthermore, the large amount of V also makes it impossible to guarantee excellent weld metallurgical quality, resulting in significant welding spatter.

[0006] Chinese patent application CN118789164A discloses a 1000MPa grade low-temperature high-toughness gas-shielded welding wire for marine engineering. Its chemical composition, by mass percentage (wt.%), is controlled as follows: C: 0.05-0.12%, Si: 0.3-0.6%, Mn: 1.0-2.0%, Ni: 1.5-3.0%, Cr: 0.4-1.0%, Mo: 0.75-1.0%, S≤0.005%, P≤0.005%. This welding wire, through its composition design with Mn, Ni, Cr, and high Mo content, can achieve high strength. However, the deoxidizing elements in this welding wire are only Si and Mn, resulting in limited deoxidizing performance. This may lead to a high oxygen content in the weld, which can easily cause defects such as porosity, slag inclusions, and lack of fusion, and even cracks.

[0007] Furthermore, while existing high-strength welding wires utilize a large amount of alloying elements to ensure weld strength, they fail to adequately consider the wire's drawability and the weld's metallurgical quality. The addition of elements such as Mn, Mo, and Cr increases the hardness and compositional segregation of the welding wire rod, making it prone to breakage during drawing. The addition of deoxidizing elements such as Si, Mn, and Ti increases the number of large, insoluble inclusions in the weld. The small molten pool and rapid cooling rate of gas-shielded welding easily lead to large inclusions remaining in the steel, thereby increasing crack susceptibility and reducing the weld's impact toughness. Summary of the Invention

[0008] This invention addresses the challenges of achieving both excellent strength and toughness as well as metallurgical quality in the weld seams of existing high-strength coal mine hydraulic support steel gas shielded welding wires, as well as the frequent wire breakage during the wire preparation process. It provides a gas shielded welding wire for coal mine hydraulic supports with a strength exceeding 900 MPa and its preparation method. The invention optimizes the component ratio of the welding wire and develops a stable welding wire preparation process based on the composition, thereby achieving a balance between the comprehensive performance of high-strength coal mine hydraulic support weld seams.

[0009] To solve the above technical problems, the technical solution adopted by the present invention is: a gas-shielded welding wire for coal mine hydraulic supports with a strength higher than 900MPa, wherein the chemical composition of the gas-shielded welding wire, by mass percentage, includes: C: 0.03~0.06, Si: 0.51~0.70, Mn: 1.35~1.64, P≤0.010, S≤0.005, Cr: 0.20~0.38, Ni: 2.35~2.65, Cu: 0~0.09, Mo: 0.45~0.70, Ti: 0.015~0.030, Nb: 0.025~0.035, Ce: 0.002~0.006, B: 0.0005~0.0012, O≤0.004, N≤0.006, balance being Fe and other unavoidable impurities. Among them, the five harmful elements Pb+Sn+As+Sb+Bi≤0.008.

[0010] Furthermore, the chemical composition of the gas-shielded welding wire satisfies 0.019≤Ω≤0.036, where Ω=(25Ce+68B) / (Si+3Mn+85Ce+36Ti).

[0011] Furthermore, the chemical composition of the gas-shielded welding wire satisfies 2.30≤Φ≤3.71, where Φ=(21B+15Nb+10Ti+9Mo+Ni+2Mn) / (3Si+4Cr+18C).

[0012] Furthermore, the gas-shielded welding wire is welded using a mixed gas of 80-95% Ar and 5-20% CO2 and / or O2. Under the process conditions of 10-20 kJ / cm heat input, the weld metal yield strength is ≥820 MPa, tensile strength is ≥900 MPa, elongation is ≥21%, and low-temperature impact toughness at -40℃ is ≥75 J.

[0013] Furthermore, in the weld, 1mm 2 The proportion of inclusions larger than 1 micrometer in the region shall not exceed 6%, and the proportion of acicular ferrite in the weld shall not be less than 80%.

[0014] This invention also provides a method for preparing gas-shielded welding wire for coal mine hydraulic supports with a strength higher than 900 MPa, for preparing the above-mentioned gas-shielded welding wire, the preparation method comprising the following steps: (1) Preparation of wire rod for welding wire: Smelt welding wire steel according to the chemical composition and proportion of gas shielded welding wire, and prepare a billet with the required composition; forge at 1000~1100℃, heat treatment at 1100~1200℃ for 2 h, phosphorus treatment at 1020~1050℃, precision rolling at 880~950℃, and diameter reduction at 800~830℃ to prepare wire rod for gas shielded welding wire with a diameter of φ of 5.5 mm; (2) Preparation of welding wire by wire rod drawing: φ5.5mm wire rod is annealed at 700~800℃ and held for 2h. The wire rod is then reduced from φ5.5mm to φ3.85mm in the welding wire production line. After that, it is annealed at 700~800℃ and held for 2h. The wire rod is then further reduced to φ1.2mm to obtain gas shielded welding wire. (3) Copper plating of welding wire: Copper is uniformly plated on the surface of gas shielded welding wire using a chemical method to obtain finished welding wire.

[0015] Furthermore, in step (2), the φ5.5mm wire rod is reduced to φ3.85mm three times, and the diameters after the three reductions are φ5.05mm, φ4.35mm and φ3.85mm respectively.

[0016] Furthermore, in step (2), the φ3.85mm wire rod is reduced to φ1.2mm three times, and the diameters after the three reductions are φ2.45mm, φ1.85mm and φ1.2mm respectively.

[0017] Furthermore, the copper plating thickness is 0.20–0.22 micrometers.

[0018] The beneficial effects of the present invention are: (1) By rationally designing the chemical composition, the yield strength of the weld metal is ≥820 MPa, the tensile strength is ≥900 MPa, the elongation is ≥21%, and the low-temperature impact toughness at -40℃ is ≥75 J; (2) After welding, the inclusions in the weld are dispersed and refined, and the structure is mainly composed of refined acicular ferrite rather than bainite and martensite, resulting in excellent weld strength and toughness; (3) By optimizing the composition ratio of the welding wire and developing a stable welding wire preparation process based on the composition, the comprehensive performance of the weld of the high-strength coal mine hydraulic support is taken into account.

[0019] The present invention will now be described in detail with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a comparison diagram of the metallurgical quality and radiographic testing results of the gas-shielded welding wire of the present invention and the weld seam of the comparative example. Figure 1 In the diagram, a1 is the weld quality diagram of the gas-shielded welding wire in Example 1, a2 is the radiographic testing result diagram of the gas-shielded welding wire in Example 1, b1 is the weld quality diagram of the gas-shielded welding wire in Comparative Example 1, and b2 is the radiographic testing result diagram of the gas-shielded welding wire in Comparative Example 1.

[0021] Figure 2 The image shows typical inclusions in the gas-shielded welding wire of the present invention and the comparative weld. Figure 2 In the diagram, a is an image of inclusions in the gas-shielded weld seam of Example 3, and b is an image of inclusions in the gas-shielded weld seam of Comparative Example 2.

[0022] Figure 3 This is a comparison diagram of the original austenitic grain size and weld microstructure between the gas-shielded welding wire of the present invention and the gas-shielded welding wire of the comparative example. Figure 3 In the figure, a1 is the average width of the original austenitic grain boundary of the gas-shielded welding wire weld in Example 5, a2 is the weld microstructure of the gas-shielded welding wire in Example 5, b1 is the average width of the original austenitic grain boundary of the gas-shielded welding wire weld in Comparative Example 3, and b2 is the weld microstructure of the gas-shielded welding wire weld in Comparative Example 3. Detailed Implementation

[0023] This invention provides a gas-shielded welding wire for coal mine hydraulic supports with a strength higher than 900 MPa. The chemical composition of the gas-shielded welding wire, by mass percentage, includes: C: 0.03~0.06, Si: 0.51~0.70, Mn: 1.35~1.64, P≤0.010, S≤0.005, Cr: 0.20~0.38, Ni: 2.35~2.65, Cu: 0~0.09, Mo: 0.45~0.70, Ti: 0.015~0.030, Nb: 0.025~0.035, Ce: 0.002~0.006, B: 0.0005~0.0012, O≤0.004, N≤0.006, with the balance being Fe and other unavoidable impurities. Among these, the five harmful elements Pb+Sn+As+Sb+Bi≤0.008.

[0024] The design basis for each chemical component in this invention is as follows.

[0025] Carbon (C): Increased C content is beneficial for improving the strength and hardness of steel, and enhances the tensile properties of welds through solid solution strengthening. However, excessive carbon significantly increases crack susceptibility, reduces the drawability of welding wire steel, and easily introduces a hard and brittle second phase. In this invention, the C content is 0.03~0.06%, preferably 0.04~0.05%.

[0026] The addition of Si can act as a deoxidizer to reduce weld porosity, improve strength, and enhance resistance to high-temperature oxidation. However, excessive silicon can easily generate large-sized M / A components in the weld, leading to a decrease in weld metal toughness. Furthermore, it promotes the formation of brittle silicate inclusions, increasing the risk of welding spatter. In this invention, the Si content is 0.51~0.70%, preferably 0.53~0.62%, and more preferably 0.55~0.59%.

[0027] Mn: Mn can also play a deoxidizing role in welds, and can improve weld strength and toughness, and inhibit the hot brittleness of sulfur. However, excessive Mn can cause segregation problems, making the welding wire prone to breakage during drawing. It can also lead to local embrittlement and an increased tendency for cold cracking. In this invention, the Mn content is 1.35~1.64%, preferably 1.38~1.61%, and more preferably 1.41~1.56%.

[0028] Both phosphorus (P) and sulfur (S) are elements that should be avoided as much as possible in welds. P significantly increases the cold brittleness of weld metal and reduces its low-temperature toughness, while sulfur combines with iron to form low-melting-point FeS, which can trigger solidification cracks in the weld. Therefore, the content of P should be controlled to ≤0.010%, and the content of S to ≤0.005%.

[0029] Cr: Adding an appropriate amount of Cr to the welding wire can increase its stiffness and effectively improve the strength of the weld. However, excessive addition can reduce the wire's drawability. Furthermore, Cr can cause carbide precipitation, increasing the weld's brittleness and hardness. In this invention, the Cr content is 0.20~0.38%, preferably 0.21~0.35%, and more preferably 0.25~0.29%.

[0030] Ni: Adding Ni to welding wire can significantly improve low-temperature toughness and reduce the ductile-brittle transition temperature. However, excessive addition increases the viscosity of the molten pool, which can easily lead to hot cracking. Therefore, the content of Mn and Cu must be controlled when adding Ni. In this invention, the Ni content is 2.35~2.65%, preferably 2.38~2.61%, and more preferably 2.44~2.52%.

[0031] Cu: Adding Cu to the weld helps to form ε-Cu in the weld and improve the weld strength. However, in welds with high Ni content, the increase of Cu will increase the susceptibility to brittle cracks. Considering that copper plating of the welding wire will increase the Cu content in the subsequent weld, the Cu content of this series of welding wires is low, which is 0~0.09%, preferably 0.03~0.08%, and more preferably 0.05~0.07%.

[0032] Mo: The transition of Mo to the weld seam can significantly lower the phase transformation point and effectively refine the weld seam structure. It is one of the main elements for maintaining the high strength of the weld seam in this patent. However, when its content increases, it can easily cause carbide aggregation and increase crack susceptibility. In this invention, the Mo content is 0.45~0.70%, preferably 0.48~0.68%, and more preferably 0.55~0.61%.

[0033] Ti: Ti is a strong deoxidizer. It interacts with Si and Mn in the weld to exert a deoxidizing effect, and its oxides can serve as nucleation sites for acicular ferrite. However, as its content increases, the inclusions become larger and more prone to aggregation, reducing the bonding ability between the inclusions and the matrix, and becoming crack initiation sites. In this invention, the Ti content is 0.015~0.030%, preferably 0.018~0.026%, and more preferably 0.022~0.025%.

[0034] Nb: Nb can remove nitrogen in the weld, and its co-precipitation with C and N results in smaller particle sizes. This can strengthen the weld by precipitation and also pin grain boundaries, refining the austenite grains. However, excessive Nb can reduce weldability and result in poor weld metallurgical quality. In this invention, the Nb content is 0.025~0.035%, preferably 0.026~0.034%, and more preferably 0.028~0.031%.

[0035] Ce: Rare earth elements in welds can modify inclusions, reduce their size, and enhance their heterogeneous nucleation ability. Furthermore, Ce agglomerates at grain boundaries, lowering interfacial energy, inhibiting the nucleation of grain boundary ferrite, and refining the weld microstructure. However, high Ce content can easily lead to fibrous steel formation during the casting of welding wire, and also coarsen the size of inclusions. In this invention, the Ce content is 0.002~0.006%, preferably 0.003~0.006%, and more preferably 0.004~0.005%.

[0036] B: During welding, B transitions into the weld, can agglomerate at grain boundaries, reduce interfacial energy, and can also combine with Mo to significantly improve hardenability and refine the acicular ferrite structure. However, when its content is high, the weld's crack susceptibility increases, and the risk of weld cracking rises. In this invention, the B content is 0.0005~0.0012%, preferably 0.0007~0.0011%, and more preferably 0.0008~0.0009%.

[0037] Increased oxygen (O) content in the weld can lead to large inclusions and porosity defects; while excessive nitrogen (N) content can cause aging embrittlement. For welds with high strength, the O and N contents should be minimized to ensure excellent strength and toughness, with O content ≤0.004% and N content ≤0.006%.

[0038] In welds, the five harmful elements (Pb, Sn, As, Sb, and Bi) segregate at grain boundaries, inducing welding hot cracking and lamellar tearing, significantly reducing strength and ductility. Furthermore, higher Pb content leads to greater spatter during welding. The recommended control level for these five harmful elements is ≤0.008% (Pb + Sn + As + Sb + Bi).

[0039] In addition to the above-mentioned requirement to reasonably control the chemical composition range of each element, the following innovative technical requirements must also be set to accurately regulate the relative addition amounts of some key elements. To ensure that the welding wire has both high strength and toughness, the total elements C, Si, Mn, Mo, Ni, Cr, Ti, Nb, Ce, and B in the welding wire, calculated by weight percentage according to their chemical composition, must meet the following conditions: 0.019≤Ω≤0.036, 2.30≤Φ≤3.71, where Ω=(25Ce+68B) / (Si+3Mn+85Ce+36Ti); Φ=(21B+15Nb+10Ti+9Mo+Ni+2Mn) / (3Si+4Cr+18C).

[0040] Refining the weld microstructure is key to achieving high strength and toughness. Traditional high-strength gas-shielded welding wires primarily produce lath bainite and martensite, but their high hardness leads to high weld crack susceptibility. This invention, through the addition of the aforementioned alloying elements, prepares a high-strength weld microstructure dominated by high-density acicular ferrite. By controlling the ratio of Ce, B, Si, Mn, and Ti (25Ce+68B) / (Si+3Mn+85Ce+36Ti) to a value between 0.019 and 0.036, not only are nano- and submicron-sized liquid-phase precipitates introduced, but also the segregation of B and Ce at grain boundaries is effectively achieved. Submicron-sized particles act as ferrite nucleation sites, while nano-sized particles pin the original austenite grain boundaries, refining the grains. The segregation of elements at the grain boundaries can reduce the interface energy and inhibit the formation of grain boundary ferrite. Through the above, it can be ensured that ferrite nucleates within small austenite grains, and they compete with each other to grow, which can effectively obtain fine ferrite laths.

[0041] In addition, the addition of C, Si, Mn, Mo, Ni, Cr, Ti, Nb, and B elements ensures weld strength through solid solution strengthening, precipitation strengthening, and dislocation strengthening. However, large-sized carbides in the weld significantly increase crack initiation susceptibility and reduce weld toughness. Controlling the ratio of Si, Cr, and Mn (elements that easily produce large-sized carbides) to the main weld strengthening elements (21B+15Nb+10Ti+9Mo+Ni+2Mn) / (3Si+4Cr+18C) to 2.30-3.71 reduces toughness loss while maintaining high strength in the weld metal.

[0042] The present invention also provides a method for preparing the above-mentioned gas-shielded welding wire, which specifically includes the following steps.

[0043] (1) Preparation of wire rod for welding wire: Welding wire steel is smelted according to the composition and alloy ratio of claim 1, and a cast billet with the required composition is prepared; then it is forged at 1000~1100℃, held at 1100~1200℃ for 2 h, phosphoricated at 1020~1050℃, precision rolled at 880~950℃, and reduced in diameter at 800~830℃ to prepare wire rod for gas shielded welding wire with a diameter of φ of 5.5 mm; (2) Preparation of welding wire by wire rod drawing: φ5.5mm wire rod is annealed at 700~800℃ and held for 2h. The wire rod is then reduced in diameter three times in the welding wire production line: φ5.5mm→φ5.05mm→φ4.35mm→φ3.85mm. After that, it is annealed at 700~800℃ and held for 2h. Then, it is reduced in diameter three times in the production line: φ3.85mm→φ2.45mm→φ1.85mm→φ1.2mm to obtain gas shielded welding wire.

[0044] As the strength of welding wire increases, it is prone to breakage without annealing treatment, and also prone to breakage with fewer reduction cycles, thus reducing efficiency. In this invention, the welding wire undergoes one heat treatment followed by three reduction cycles, and then another heat treatment and three reduction cycles to finally obtain the required diameter of the finished welding wire. This ensures no breakage and provides good drawing performance.

[0045] (3) Copper plating of welding wire: The surface of commercial welding wire is uniformly plated with copper of 0.20 to 0.22 micrometers by chemical method to obtain finished welding wire.

[0046] The aforementioned gas-shielded welding wire is used in welding with a mixed gas of 80-95% Ar and 5-20% CO2 and / or O2. Under process conditions of 10-20 kJ / cm heat input, the weld metal yield strength ≥820 MPa, tensile strength ≥900 MPa, elongation ≥21%, and low-temperature impact toughness ≥75 J at -40℃. The weld thickness is 1 mm. 2 The proportion of inclusions larger than 1 micrometer in the region shall not exceed 6%, and the proportion of acicular ferrite in the weld shall not be less than 80%.

[0047] The gas-shielded welding wire of the present invention will be further explained and described below with reference to specific embodiments.

[0048] Seven heats of welding wire steel according to the embodiments of the present invention and three heats of welding wire steel according to the comparative examples were prepared in a 100 kg vacuum induction furnace. The elemental composition of the welding wire steel according to the embodiments of the present invention meets the requirements of the present invention. The welding wire steels of the embodiments and the comparative examples were melted and cast sequentially according to a certain elemental composition ratio to obtain as-cast alloy billets. The composition of the welding wire steels of the embodiments and the comparative examples was analyzed according to GB / T 4336 "Spark Source Atomic Emission Spectroscopy Analysis Method (Conventional Method) for Carbon Steel and Medium and Low Alloy Steels". The specific chemical composition is shown in Table 1.

[0049] Table 1 Chemical composition (wt.%, balance Fe) of welding wire steel in Examples 1-7 and Comparative Examples 1-3 .

[0050] The welding wire steels of Examples 1-7 and Comparative Examples 1-3 were subjected to wire rod rolling, wire drawing, and copper plating. Table 2 summarizes the comparative data of key process parameters in the preparation of different welding wire steels. The results show that the wire rod rolling, wire drawing, and copper plating process provided by this invention did not result in wire breakage. The copper plating thickness on the surface of the welding wire was uniform, and the color was bright, significantly improving the wire breakage problem in the comparative examples.

[0051] Table 2. Main process parameters for the preparation of gas shielded welding wires in Examples 1-7 and Comparative Examples 1-3 .

[0052] Welding tests were conducted on typical butt joints of the welding wires prepared in Examples 1-7 and Comparative Examples 1-3. The specific welding process parameters are shown in Table 3. The welding test plate was made of Q800M steel for coal mine hydraulic supports with a thickness of 20 mm, yield strength of 855 MPa, tensile strength of 963 MPa, elongation of 21%, and average impact value at -40 ℃ of 201 J.

[0053] Table 3 Gas shielded welding process parameters for Examples 1-7 and Comparative Examples 1-3 .

[0054] During the welding process of the welding materials in the embodiments and comparative examples, the welding quality was observed. The weld appearance morphology of Embodiment 1 and Comparative Example 1 is shown below. Figure 1 (a1) and Figure 1 (b1). The weld bead produced by welding with the wire of this embodiment is uniformly distributed, has good continuity, and exhibits low welding spatter. In contrast, the weld bead produced by welding with the wire of the comparative embodiment is discontinuous, exhibits undercut, and is non-linear, indicating poor droplet flowability. Moreover, compared to the welding wire of this patent, the welding spatter is greater. After welding, the welds of the embodiment and the comparative embodiment were subjected to radiographic testing, and the results are shown below. Figure 1 (a2) and Figure 1 (b2). Radiographic testing results showed that, compared with the welding wire of the comparative example, the welding wire of the embodiment had no defects such as pores inside, and the weld metallurgical quality was higher. In addition, macroscopic cross-sections of the joints in the defect-free areas of the embodiments and comparative examples were taken, and the weld composition was detected. The results are shown in Table 4.

[0055] Table 4 Chemical composition (wt.%, balance Fe) of weld metals after welding with gas-shielded welding wires of Examples 1-7 and Comparative Examples 1-3 .

[0056] After the composition analysis was completed, the macroscopic cross-section of the joint was polished with 100x~1500x sandpaper. The inclusions were observed and photographed under a metallographic microscope. The inclusion morphology of Example 3 and Comparative Example 2 is shown in the figure. Figure 2 (a) and Figure 2 (b) Compared to the comparative example, the inclusions in the embodiments are smaller in size and mostly circular. Furthermore, the inclusions in the metallographic photographs of the embodiments and comparative examples are 1 mm smaller. 2 The inclusions in the region were statistically analyzed, and the results are shown in Table 5. In the example, the inclusion size greater than 1 μm was no more than 6%. The inclusions were relatively small, which can effectively reduce stress concentration and improve the bonding force with the matrix.

[0057] Table 5. Size distribution of inclusions in gas-shielded welds of Examples 1-7 and Comparative Examples 1-3 .

[0058] The macroscopic cross-sections of the examples and comparative examples were etched with 4% nitric acid alcohol and observed under a metallographic microscope at low and high magnification. The results are shown in the figure. Figure 3 It can be observed through low magnification that ( Figure 3 In the examples a1 and b1, the average width of the original austenitic grains in the welding wire is significantly reduced compared to the comparative example; further high-magnification observation revealed ( Figure 3 In examples a2 and b2), the microstructure within the columnar crystals is dominated by fine acicular ferrite, while the microstructure within the columnar crystals in the comparative example contains a large amount of blocky ferrite and side-plate ferrite.

[0059] Samples were taken from the weld metals of Examples 1-7 and Comparative Examples 1-3 from the areas that passed the flaw detection test, and the mechanical properties of the weld metals were tested. The tensile properties of the weld metals were sampled and tested according to GB / T 228.1 standard, and the impact properties were sampled and tested according to GB / T 2650 standard. Three impact samples were taken from each sample to reduce error. The statistical results of the mechanical property tests are shown in Table 6. The results show that the weld metals of the welding wires in this example can achieve both good strength and toughness. However, the weld metals of the comparative examples exhibited insufficient strength or insufficient toughness.

[0060] Table 6. Mechanical property test results of weld metals after welding with gas-shielded welding wires in Examples 1-7 and Comparative Examples 1-3. .

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A gas-shielded welding wire for coal mine hydraulic supports with a strength higher than 900 MPa, characterized in that, The chemical composition of the gas-shielded welding wire, by mass percentage, includes: C: 0.03~0.06, Si: 0.51~0.70, Mn: 1.35~1.64, P≤0.010, S≤0.005, Cr: 0.20~0.38, Ni: 2.35~2.65, Cu: 0~0.09, Mo: 0.45~0.70, Ti: 0.018~0.026, Nb: 0.025~0.035, Ce: 0.002~0.006, B: 0.0005~0.0012, O≤0.004, N≤0.006, balance Fe and other unavoidable impurities. Among them, the five harmful elements Pb+Sn+As+Sb+Bi≤0.008; The chemical composition of the gas-shielded welding wire satisfies 0.019≤Ω≤0.036, Ω=(25Ce+68B) / (Si+3Mn+85Ce+36Ti). The chemical composition of the gas-shielded welding wire satisfies 2.30≤Φ≤3.71, where Φ=(21B+15Nb+10Ti+9Mo+Ni+2Mn) / (3Si+4Cr+18C).

2. The gas-shielded welding wire according to claim 1, characterized in that, The gas-shielded welding wire is used for welding with a mixed gas of 80-95% Ar and 5-20% CO2 and / or O2. Under the process conditions of 10-20 kJ / cm heat input, the weld metal yield strength is ≥820 MPa, tensile strength is ≥900 MPa, elongation is ≥21%, and low-temperature impact toughness at -40℃ is ≥75 J.

3. The gas-shielded welding wire according to claim 2, characterized in that, 1mm in the weld 2 The proportion of inclusions larger than 1 micrometer in the region shall not exceed 6%, and the proportion of acicular ferrite in the weld shall not be less than 80%.

4. A method for preparing a gas-shielded welding wire for coal mine hydraulic supports with a strength higher than 900 MPa, based on the gas-shielded welding wire according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) Preparation of wire rod for welding wire: Smelt welding wire steel according to the chemical composition and proportion of gas shielded welding wire, and prepare a billet with the required composition; forge at 1000~1100℃, heat treatment at 1100~1200℃ for 2 h, descaling at 1020~1050℃, fine rolling at 880~950℃, and diameter reduction at 800~830℃ to prepare wire rod with a diameter of φ of 5.5 mm for gas shielded welding wire; (2) Preparation of welding wire by wire rod drawing: φ5.5mm wire rod is annealed at 700~800℃ and held for 2h. The wire rod is then reduced from φ5.5mm to φ3.85mm in the welding wire production line. After that, it is annealed at 700~800℃ and held for 2h. The wire rod is then further reduced to φ1.2mm to obtain gas shielded welding wire. (3) Copper plating of welding wire: Copper is uniformly plated on the surface of gas shielded welding wire using a chemical method to obtain finished welding wire.

5. The preparation method according to claim 4, characterized in that, In step (2), the φ5.5mm wire rod is reduced to φ3.85mm three times. The diameters after the three reductions are φ5.05mm, φ4.35mm and φ3.85mm respectively.

6. The preparation method according to claim 4, characterized in that, In step (2), the φ3.85mm wire rod is reduced to φ1.2mm three times. The diameters after the three reductions are φ2.45mm, φ1.85mm and φ1.2mm respectively.

7. The preparation method according to claim 4, characterized in that, The copper plating thickness is 0.20 to 0.22 micrometers.

Images