Coal mine hydraulic support gas shield welding wire with strength higher than 900 MPa and preparation method of coal mine hydraulic support gas shield welding wire

Abstract

The invention provides a coal mine hydraulic support gas shield welding wire with the strength higher than 900 MPa and a preparation method of the coal mine hydraulic support gas shield welding wire. The gas shield welding wire comprises, by mass, 0.03%-0.06% of C, 0.51%-0.70% of Si, 1.35%-1.64% of Mn, smaller than or equal to 0.010% of P, smaller than or equal to 0.005% of S, 0.20%-0.38% of Cr, 2.35%-2.65% of Ni, 0%-0.09% of Cu, 0.45%-0.70% of Mo, 0.015%-0.030% of Ti, 0.025%-0.035% of Nb, 0.002%-0.006% of Ce, 0.0005%-0.0012% of B, smaller than or equal to 0.004% of O, smaller than or equal to 0.006% of N and the balance Fe and The invention has the following beneficial effects: (1) through reasonable design of chemical components, the yield strength of weld metal is greater than or equal to 820 MPa, the tensile strength is greater than or equal to 900 MPa, the ductility is greater than or equal to 21%, and the low-temperature impact toughness at-40 DEG C is greater than or equal to 75 J; (2) inclusions in a weld joint are dispersed and refined after the welding wire is welded, refined acicular ferrite instead of bainite and martensite is taken as a main structure, and the strength and toughness of the weld joint are excellent; and (3) the composition proportion of the welding wire is optimized, a stable welding wire preparation process is developed according to the components, and the comprehensive performance of the high-strength coal mine hydraulic support welding seam is considered.

Description

Technical Field

[0001] The present invention belongs to the field of high-strength welding materials for coal mine hydraulic supports, and specifically relates to a gas-shielded welding wire and a preparation method thereof that are compatible with Q800M-Q890M steel for coal mine hydraulic supports. 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°C is ≥75 J. Background Art

[0002] Coal mine hydraulic supports are the core support equipment in fully mechanized mining faces, mainly responsible for roof support, stope space maintenance, and equipment pushing functions. Their structural stability directly determines the safety production efficiency of the mine - under complex underground geological conditions, the supports need to withstand periodic mine pressure impacts and roof subsidence loads, while meeting dynamic operation requirements such as rapid support moving and adaptive posture adjustment. With the proportion of thick coal seam mining in China increasing to more than 45%, traditional Q550-grade steel can no longer meet the requirements of 10-meter large mining height supports for material strength, lightweight, and impact resistance. Q800M-Q890M steel has received extensive attention in the rib plates, lugs, and valve blocks of coal mine hydraulic supports due to its high tensile strength and excellent performance with a low-temperature impact energy of over 120 J at -40°C. Compared with traditional steel, its structure weight reduction reaches 18% under the same load-bearing conditions, reducing underground transportation energy consumption; after the yield strength is increased by 45%, the working resistance of the support can exceed 20,000 kN, and the support height can be extended to 12 meters, meeting the requirements of efficient mining of 8-10-meter extra-thick coal seams. Due to reasons such as complex structure or narrow space in these parts, gas shielded welding is generally used. However, due to the increase in steel strength, welding defects frequently occur in gas shielded welding, severely restricting the wide application of this strength grade of steel. The core problem lies in the lag of the welding wire matching system. Mainstream welding materials on the market are difficult to achieve both high strength and toughness of the weld and excellent weld metallurgical quality with the Q800M-Q890M base metal, resulting in the joint becoming a high-risk area for structural failure.

[0003] Many domestic welding material factories and research institutes have also done a lot of research work on the development of high-strength gas shielded welding wires.

[0004] The invention patent with the publication number CN119177408A discloses an ultra-high strength wire rod of 1100 MPa grade and its preparation method. The chemical composition is controlled according to the following requirements by 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 wire rod of the wire welding steel with this composition system is expected to be made into a high-strength gas shielded welding wire through further processes such as wire drawing and copper plating. A large amount of deoxidizing elements Si, Ti, and Mn are added to the wire rod, which can effectively ensure the deoxidation performance of the prepared welding wire. However, the addition amounts of Si and Cr in the welding wire are relatively high, and a large number of large-sized M / A constituents are easily generated during the welding process. The hydraulic support needs to bear dynamic loads during service, and the large-sized M / A constituents are easily become the crack initiation sites, resulting in poor impact toughness and fatigue performance of the weld metal.

[0005] The invention patent with the announcement number CN103331529B discloses a mixed gas shielded welding wire with a tensile strength ≥1100 MPa and its usage method. The chemical composition is controlled according to the following requirements by mass percentage (wt.%): 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: 0.35 - 0.85, 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. Through the above composition ratio, the welding wire obtains a weld microstructure mainly composed of fine bainite and high-density low-carbon martensite, achieving a relatively high strength. However, the C content, and the B and V contents in the welding wire are relatively high, resulting in a high hardening tendency and a relatively large welding crack sensitivity. Moreover, due to the large addition of V, it is also impossible to ensure excellent weld metallurgical quality, and the welding spatter is relatively large.

[0006] The invention patent with the publication number CN118789164A discloses a 1000MPa grade low-temperature high-toughness gas shielded welding wire for offshore engineering. The chemical composition is controlled according to the following requirements by mass percentage (wt.%): 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%. Through the composition design of Mn, Ni, Cr and high Mo, this welding wire can achieve relatively high strength. However, the deoxidizing elements in this welding wire only include Si and Mn, and the deoxidizing performance is limited, which may cause a relatively high oxygen content in the weld, and thus easily lead to defects such as porosity, slag inclusion and lack of fusion in the weld, and even cracks may occur.

[0007] In addition, when existing high-strength welding wires use a large amount of alloying elements to ensure the strength of the weld, they fail to fully consider the drawing performance of the welding wire and the metallurgical quality of the weld. The addition of elements such as Mn, Mo, and Cr increases the hardness and the degree of composition segregation of the wire rod of the welding wire, and wire breakage is likely to occur during the drawing process. The addition of deoxidizing elements such as Si, Mn, and Ti increases the number of large-size insoluble inclusions in the weld. The gas shielded welding has a small molten pool volume and a fast cooling rate, which easily leads to the retention of large-size inclusions in the steel, thereby increasing the crack sensitivity and reducing the impact toughness of the weld. Summary of the Invention

[0008] In order to solve the problems that the weld of the gas shielded welding wire for high-strength coal mine hydraulic supports is difficult to balance excellent strength and toughness and metallurgical quality, and wire breakage is likely to occur during the preparation process of the welding wire, the present invention provides a gas shielded welding wire for coal mine hydraulic supports with a strength higher than 900MPa and its preparation method, optimizes the component ratio of the welding wire, and develops a stable welding wire preparation process based on the components, thereby achieving the balance of the comprehensive performance of the weld of high-strength coal mine hydraulic supports.

[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, and the chemical composition in the gas shielded welding wire includes by mass percentage: 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, and the balance is Fe and other inevitable impurities. Among them, the five harmful elements Pb + Sn + As + Sb + Bi ≤ 0.008.

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

[0011] Furthermore, the chemical components in the gas shielded welding wire satisfy 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 with a mixed gas in which Ar accounts for 80 - 95% and CO 2 and / or O 2 accounts for 5 - 20%. Under the process conditions of a heat input of 10 - 20 kJ / cm, 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°C is ≥ 75 J.

[0013] Furthermore, in the weld, the proportion of inclusions larger than 1 μm in the 1 mm 2 area is not higher than 6%, and the proportion of acicular ferrite in the weld is not lower than 80%.

[0014] The present invention also provides a preparation method for a gas shielded welding wire for a coal mine hydraulic support with a strength higher than 900 MPa, which is used to prepare the above-mentioned gas shielded welding wire. The preparation method includes the following steps: (1) Prepare the wire rod for the welding wire: smelt the welding wire steel according to the chemical components and ratio of the gas shielded welding wire, and prepare a cast billet with qualified components; forge at 1000 - 1100°C, heat preserve at 1100 - 1200°C for 2 h, desphosphorize at 1020 - 1050°C, finish rolling at 880 - 950°C, and reduce the diameter at 800 - 830°C to prepare a wire rod for the gas shielded welding wire with a diameter φ of 5.5 mm; (2) Prepare the welding wire by drawing the wire rod: anneal and heat preserve the φ5.5 mm wire rod at 700 - 800°C for 2 h, reduce the diameter from φ5.5 mm to φ3.85 mm on the welding wire production line, then anneal and heat preserve at 700 - 800°C for 2 h again, and continue to reduce the diameter to φ1.2 mm to obtain the gas shielded welding wire; (3) Copper plating for the welding wire: uniformly copper plate the surface of the gas shielded welding wire by a chemical method to obtain the finished welding wire.

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

[0016] Further, in step (2), the wire rod with a diameter of φ3.85 mm is reduced in diameter three times to φ1.2 mm, and the diameters after the three times of diameter reduction are φ2.45 mm, φ1.85 mm, and φ1.2 mm respectively.

[0017] Further, the copper plating thickness is 0.20 - 0.22 microns.

[0018] The beneficial effects of the present invention are as follows: (1) By reasonably 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°C is ≥75 J; (2) The inclusions in the weld after welding with the wire are dispersed and refined, and the structure is mainly composed of refined acicular ferrite rather than bainite and martensite, and the weld has excellent strength and toughness; (3) By optimizing the component ratio of the wire and developing a stable wire preparation process based on the components, the comprehensive performance of the high-strength coal mine hydraulic support weld is taken into account.

[0019] The present invention will be described in detail below with reference to the accompanying drawings. Description of the Drawings

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

[0021] Figure 2 It is the observation of typical inclusions in the welds of the gas shielded wire of the present invention and the comparative example. Figure 2 In it, a is the inclusion diagram of the gas shielded weld in Example 3, and b is the inclusion diagram of the gas shielded weld in Comparative Example 2.

[0022] Figure 3 It is a comparison diagram of the original austenite grain size and weld structure of the gas shielded wire of the present invention and the comparative example. Figure 3 In it, a1 is the average width of the original austenite grain boundary of the weld of the gas shielded wire in Example 5, a2 is the weld structure of the gas shielded wire in Example 5, b1 is the average width of the original austenite grain boundary of the weld of the gas shielded wire in Comparative Example 3, and b2 is the weld structure of the gas shielded wire in Comparative Example 3. Detailed Embodiments

[0023] The present invention provides a gas shielded welding wire for coal mine hydraulic supports with a strength higher than 900 MPa. The chemical components in the gas shielded welding wire, by mass percentage, include: 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, and the balance is Fe and other inevitable impurities. Among them, the content of the five harmful elements Pb + Sn + As + Sb + Bi ≤ 0.008.

[0024] The design basis of each chemical component in the present invention is as follows.

[0025] C: The increase of C is beneficial to improving the strength and hardness of steel, and improving the tensile property of the weld through solid solution strengthening. However, excessive carbon significantly increases the crack sensitivity, reduces the drawing property of the welding wire steel, and is prone to introducing hard and brittle second phases. In the present invention, the content of C is 0.03 - 0.06%, preferably 0.04 - 0.05%.

[0026] Si: The addition of Si can be used as a deoxidizer to reduce weld porosity, improve strength and high-temperature oxidation resistance. However, excessive silicon is prone to generating large-size M / A components in the weld, resulting in a decrease in the toughness of the weld metal. Moreover, it will promote the formation of brittle silicate inclusions and increase the risk of welding spatter. In the present invention, the content of Si 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 the weld, and can improve the strength and toughness of the weld, inhibit the hot brittleness of sulfur. However, its excess will cause segregation problems, making the welding wire prone to wire breakage during the drawing process. Moreover, it will lead to local embrittlement and an increase in the tendency of cold cracks. In the present invention, the content of Mn is 1.35 - 1.64%, preferably 1.38 - 1.61%, and more preferably 1.41 - 1.56%.

[0028] Both P and S are elements that need to be avoided as much as possible in the weld. P will significantly increase the cold brittleness of the weld metal and reduce the low-temperature toughness, while S forms low-melting-point FeS with iron, triggering weld crystallization cracks. Therefore, the content of P is controlled ≤ 0.010%, and the content of S is ≤ 0.005%.

[0029] Cr: Appropriate addition of Cr to the welding wire can increase the stiffness of the welding wire and effectively improve the strength of the weld. However, excessive addition of it will also lead to a decrease in the drawing performance of the welding wire. Moreover, Cr will also cause the precipitation of carbides, increasing the brittle and hard tendency of the weld. In the present invention, the content of Cr is 0.20 - 0.38%, preferably 0.21 - 0.35%, and more preferably 0.25 - 0.29%.

[0030] Ni: Adding Ni to the welding wire can significantly improve the low-temperature toughness and reduce the ductile-brittle transition temperature. However, excessive addition of it increases the viscosity of the molten pool and is prone to generating hot cracks. When adding it, the contents of Mn and Cu need to be controlled. In the present invention, the content of Ni is 2.35 - 2.65%, preferably 2.38 - 2.61%, and more preferably 2.44 - 2.52%.

[0031] Cu: Adding Cu to the weld is beneficial to forming ε-Cu in the weld and improving the strength of the weld. However, in the weld with a high Ni content, the increase of Cu will increase the sensitivity to brittle cracks. Considering that copper plating of the welding wire will increase the Cu content in the subsequent weld, the addition amount of Cu in this series of welding wires is relatively low, and its content is 0 - 0.09%, preferably 0.03 - 0.08%, and more preferably 0.05 - 0.07%.

[0032] Mo: When the Mo element transitions to the weld, it can significantly reduce the phase transformation point and effectively refine the weld microstructure. It is one of the main elements to achieve high strength of the weld in this patent. However, when its content increases, it is prone to cause the aggregation of carbides and increase the crack sensitivity. In the present invention, the content of Mo 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 acts in combination with Si and Mn in the weld to play a deoxidizing role, and its oxide can be used as the nucleation site of acicular ferrite. However, when its content increases, the inclusion size will be larger, prone to aggregation, reducing the bonding ability between the inclusion and the matrix, and becoming the crack initiation site. In the present invention, the content of Ti is 0.015 - 0.030%, preferably 0.018 - 0.026%, and more preferably 0.022 - 0.025%.

[0034] Nb: Nb can play a role in removing N in the weld, and it precipitates in combination with C and N, with a relatively small particle size. On the one hand, it can play a role in precipitation strengthening, and it can also pin the grain boundary and refine the austenite grain. However, excessive addition of Nb will reduce the weldability and the metallurgical quality of the weld is poor. In the present invention, the content of Nb is 0.025 - 0.035%, preferably 0.026 - 0.034%, and more preferably 0.028 - 0.031%.

[0035] Ce: Rare earth can modify inclusions in the weld, reduce the inclusion size, and enhance its heterogeneous nucleation ability. Meanwhile, the segregation of Ce at the grain boundary can reduce the interfacial energy and inhibit the nucleation of grain boundary ferrite, thereby refining the weld microstructure. However, when its content is high, it is easy to form flocculent steel during the casting process of the welding wire steel, and a high content will also coarsen the inclusion size. In the present invention, the content of Ce is 0.002 - 0.006%, preferably 0.003 - 0.006%, and more preferably 0.004 - 0.005%.

[0036] B: During the welding process, B can transition into the weld, segregate at the grain boundary to reduce the interfacial energy, and can also act in combination with Mo to significantly improve hardenability and refine the acicular ferrite structure. However, when its content is high, the crack sensitivity of the weld increases and the risk of weld cracking rises. In the present invention, the content of B is 0.0005 - 0.0012%, preferably 0.0007 - 0.0011%, and more preferably 0.0008 - 0.0009%.

[0037] An increase in the O content in the weld will form large-size inclusions, leading to porosity defects; while an excessive N content will cause age embrittlement problems. When the weld strength is relatively high, it is necessary to minimize the contents of O and N to ensure that the weld obtains excellent strength and toughness, with the O content controlled ≤ 0.004% and the N content controlled ≤ 0.006%.

[0038] In the weld, the five harmful elements will segregate at the grain boundary, causing welding hot cracks and lamellar tearing, significantly reducing strength and plasticity, and when their content is on the high side, the welding spatter is relatively large. Control the five harmful elements Pb + Sn + As + Sb + Bi ≤ 0.008%.

[0039] In addition to reasonably controlling the chemical composition ranges of each element as described above, it is also necessary to set the following innovative technical requirements to accurately regulate the relative addition amounts between 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, B in the welding wire meet the following in terms of chemical composition calculated by weight percentage: 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 the key to obtaining high strength and toughness. Traditional high-strength gas shielded welding wires mainly prepare lath bainite and martensite, but their high hardness leads to high crack sensitivity in the weld. Through the addition of the above alloying elements, the present invention prepares a high-strength weld microstructure mainly composed of high-density acicular ferrite. By regulating the ratio of Ce, B, Si, Mn, and Ti ((25Ce + 68B) / (Si + 3Mn + 85Ce + 36Ti)) to be within 0.019 - 0.036, not only nano-scale and sub-micron-scale liquid-phase precipitation particles are introduced, but also the segregation of B and Ce at the grain boundaries can be effectively achieved. The sub-micron-scale particles act as ferrite nucleation sites, and the nano-scale particles pin the original austenite grain boundaries, refining the grains; while the segregation of elements at the grain boundaries can reduce the interfacial energy and inhibit the formation of grain boundary ferrite. Through the above, it can be ensured that ferrite nucleates inside the small-area austenite grains, and they compete with each other for growth, effectively obtaining fine ferrite laths.

[0041] In addition, by adding elements such as C, Si, Mn, Mo, Ni, Cr, Ti, Nb, and B, the weld strength is ensured through solid solution strengthening, precipitation strengthening, dislocation strengthening, etc. However, large-sized carbides in the weld will significantly increase the crack initiation sensitivity and reduce the weld toughness. Controlling the ratio of elements Si, Cr, Mn that are prone to generating large-sized carbides to the main weld strengthening elements ((21B + 15Nb + 10Ti + 9Mo + Ni + 2Mn) / (3Si + 4Cr + 18C)) to be within 2.30 - 3.71 can reduce the toughness loss while achieving high strength of the weld metal.

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

[0043] (1) Preparation of the welding wire with wire rod: Smelt the welding wire steel according to the composition and alloy ratio of claim 1 to prepare a cast billet with qualified composition; then forge at 1000 - 1100 °C, heat-insulate at 1100 - 1200 °C for 2 h, desphosphorize at 1020 - 1050 °C, finish rolling at 880 - 950 °C, and reduce the diameter at 800 - 830 °C to prepare a wire rod for gas shielded welding wire with a diameter φ of 5.5 mm; (2) Preparation of the welding wire by drawing the wire rod: Anneal and heat-insulate the φ5.5 mm wire rod at 700 - 800 °C for 2 h, reduce the diameter three times on the welding wire production line from φ5.5 mm → φ5.05 mm → φ4.35 mm → φ3.85 mm, then anneal and heat-insulate at 700 - 800 °C for 2 h again, and continue to reduce the diameter three times from φ3.85 mm → φ2.45 mm → φ1.85 mm → φ1.2 mm to obtain the gas shielded welding wire.

[0044] As the strength of the welding wire increases, it is prone to wire breakage without annealing treatment, and is also prone to wire breakage with fewer wire diameter reduction passes, which will reduce efficiency. In the present invention, the welding wire is subjected to three wire diameter reductions after one heat treatment, and then heat treated again and subjected to three wire diameter reductions to finally obtain the diameter of the required finished welding wire, which can ensure no wire breakage and good drawing performance.

[0045] (3)Copper plating of the welding wire: The surface of the commercial welding wire is evenly copper plated by a chemical method with a thickness of 0.20 - 0.22 μm to obtain the finished welding wire.

[0046] The above-mentioned gas shielded welding wire uses a mixed gas with Ar accounting for 80 - 95% and CO 2 and / or O 2 accounting for 5 - 20% for welding. Under the process conditions of a heat input of 10 - 20 kJ / cm, the yield strength of the weld metal ≥ 820 Mpa, the tensile strength ≥ 900 MPa, the elongation ≥ 21%, and the low-temperature impact toughness at -40°C ≥ 75 J. The proportion of inclusions larger than 1 μm in the 1 mm 2 area in the weld is not higher than 6%, and the proportion of acicular ferrite in the weld is not less than 80%.

[0047] The following further explains and illustrates the gas shielded welding wire of the present invention with specific embodiments.

[0048] Seven furnaces of the welding wire steel of the embodiment of the present invention and three furnaces of the welding wire steel of the comparative example are smelted in a 100 kg vacuum induction furnace, wherein the element ratio of the welding wire steel of the embodiment of the present invention meets the limiting requirements of the present invention. The welding wire steels of the embodiment and the comparative example are melted and cast in sequence according to a certain element group ratio to obtain as-cast alloy billets. The compositions of the welding wire steels of the embodiment and the comparative example are detected according to GB / T 4336 "Spark source atomic emission spectrometric analysis method for carbon and low alloy steels (conventional method)", and the specific chemical compositions are shown in Table 1.

[0049] Table 1 Chemical compositions of the welding wire steels of Examples 1 - 7 and Comparative Examples 1 - 3 (wt.%, the balance is Fe) 。

[0050] The wire rod rolling, wire drawing and copper plating of the welding wire steels of the above Examples 1 - 7 and Comparative Examples 1 - 3 are carried out. Table 2 statistically shows the comparison data of the key process parameters in the preparation process of different welding wire steels. The results show that by using the wire rod rolling, wire drawing and copper plating processes provided by the present invention, no wire breakage problem occurs, the copper plating thickness on the surface of the welding wire is uniform, and the color is bright, significantly improving the wire breakage problem of the comparative example.

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

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

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

[0054] During the welding process of the welding consumables in the examples and comparative examples, the welding quality was observed. The weld appearance morphologies of Example 1 and Comparative Example 1 are shown in Figure 1 (a1)and Figure 1 (b1). The weld bead distribution of the welds welded with the welding wire of this example is uniform, with good continuity and low welding spatter. After welding with the welding wire of the comparative example, the welds are intermittent, with edge biting phenomena, and the welds are non-linear, indicating poor droplet fluidity. Moreover, compared with the welding wire of this patent, the welding spatter is larger. After welding, the welds of the examples and comparative examples were subjected to radiographic inspection, and the results are shown in Figure 1 (a2)and Figure 1 (b2). The radiographic inspection results show that compared with the welding wire of the comparative example, there are no defects such as pores in the welding wire of the example, and the weld metallurgical quality is higher. In addition, in the defect-free areas of the joints in the examples and comparative examples, the macroscopic cross-sections of the joints were intercepted and the weld compositions were detected. The results are shown in Table 4.

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

[0056] After the composition detection was completed, the macroscopic cross-sections of the joints were polished with 100x - 1500x sandpaper, and the inclusions were observed and photographed under a metallurgical microscope. The inclusion morphologies of Example 3 and Comparative Example 2 are shown in Figure 2 (a)and Figure 2 (b). Compared with the comparative example, the inclusions in the example are small in size and mostly round. In addition, the inclusions in the 1 mm 2 area in the metallographic photos of the examples and comparative examples were counted. The results are shown in Table 5. The inclusions with a size higher than 1 μm in the examples are no higher than 6%. The inclusions are relatively small, which can effectively reduce the stress concentration problem and is beneficial to improving the bonding force with the matrix.

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

[0058] The macro cross-sections of the examples and comparative examples were etched with 4% nitric acid alcohol and observed at low magnification and high magnification under a metallographic microscope. The results are shown in Figure 3 . It can be found through low-magnification observation ( Figure 3 a1 and b1 in Figure 3 ) that the average width of the original austenite grains of the welding wire in this example is significantly reduced compared with that of the comparative example; further high-magnification observation reveals (

[0059] a2 and b2 in

[0060] ) that the structure inside the columnar crystals of the example is mainly composed of fine acicular ferrite, while the columnar crystal structure of the comparative example contains a large amount of massive ferrite and side plate ferrite. 。

[0061] Finally, it should be noted that the above examples 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 the preferred embodiments, those of ordinary skill in the art should understand that it is still possible to modify the specific implementation manners of the present invention or perform equivalent replacements for some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered by the scope of the technical solutions claimed in the present invention.

Claims

1. A coal mine hydraulic support gas shielded welding wire with a strength higher than 900MPa, characterized in that: The chemical components in the gas shielded welding wire include by mass percentage: 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, the balance is Fe and other unavoidable impurities, Among them, the five harmful elements Pb+Sn+As+Sb+Bi≤0.

008.

2. The gas shielded welding wire according to claim 1, characterized in that: The chemical composition of the gas shielded welding wire satisfies 0.019≤Ω≤0.036, Ω=(25Ce+68B) / (Si+3Mn+85Ce+36Ti).

3. The gas shielded welding wire according to claim 1, characterized in that: The chemical composition of the gas shielded welding wire satisfies 2.30≤Φ≤3.71, Φ=(21B+15Nb+10Ti+9Mo+Ni+2Mn) / (3Si+4Cr+18C).

4. The gas shielded welding wire according to claim 1, characterized in that: The gas shielded welding wire is welded by a mixed gas of 80-95% Ar and 5-20% CO2 and / or O2. Under the process condition of 10-20 kJ / cm heat input, the weld metal yield strength is ≥820Mpa, the tensile strength is ≥900 MPa, the elongation is ≥21%, and the low-temperature impact toughness of -40°C is ≥75 J.

5. The gas shielded welding wire according to claim 4, characterized in that: 1mm in the weld 2 The proportion of inclusions larger than 1 micron in the area is not higher than 6%, and the proportion of acicular ferrite in the weld is not less than 80%.

6. A method for preparing a gas shielded welding wire for a coal mine hydraulic support with a strength higher than 900 MPa, based on the gas shielded welding wire according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) Preparation of wire rod for welding wire: smelting welding wire steel according to the chemical composition and proportion of gas shielded welding wire, preparing ingots with composition meeting the requirements; forging at 1000-1100℃, heat preservation at 1100-1200℃ for 2 h, treatment at 1020-1050℃, finish rolling at 880-950℃, and reducing at 800-830℃ to prepare wire rod for gas shielded welding wire with a diameter of φ5.5 mm; (2) Preparation of welding wire by wire rod drawing: φ5.5 mm wire rod is annealed and kept at 700-800℃ for 2 hours, and the diameter is reduced from φ5.5 mm to φ3.85 mm on the welding wire production line, and then annealed and kept at 700-800℃ for 2 hours, and the diameter is further reduced to φ1.2 mm to obtain gas shielded welding wire; (3) Copper plating of welding wire: The surface of the gas shielded welding wire is evenly plated with copper by chemical method to obtain the finished welding wire.

7. The preparation method according to claim 6, characterized in that: In step (2), the φ5.5 mm wire rod is reduced to φ3.85 mm three times, and the diameters after the three reductions are φ5.05 mm, φ4.35 mm and φ3.85 mm respectively.

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

9. The preparation method according to claim 6, characterized in that: The copper plating thickness is 0.20 to 0.22 microns.

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