Coal mine hydraulic support submerged arc welding wire giving consideration to high strength and toughness of welding seam and preparation method

Abstract

The invention provides a coal mine hydraulic support submerged arc welding wire considering high strength and toughness of a welding seam and a preparation method. The submerged arc welding wire comprises the following chemical components in percentage by mass: 0.09-0.15% of C, 0.05-0.10% of Si, 1.81-2.30% of Mn, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 0.20-0.45% of Cr, 2.30-2.49% of Ni, 0-0.09% of Cu, 0.51-0.90% of Mo, less than or equal to 0.020% of Ti, less than or equal to 0.015% of Ca, less than or equal to 0.025% of V, less than or equal to 0.015% of Zr, less than or equal to 0.004% of O, less than or equal to 0.006% of N and the balance of Fe and other inevitable impurities The invention has the following beneficial effects: (1) through reasonable design of chemical components, under the heat input process condition of 20-40 kJ / cm, the yield strength of weld metal is greater than or equal to 700 Mpa, the tensile strength is 810-910 MPa, the ductility is greater than or equal to 22%, and the low-temperature impact toughness at-40 DEG C is greater than or equal to 100 J; and (2) the preparation process of the welding wire is simple, annealing treatment is not needed, the welding wire is matched with sintered flux commonly used in engineering, electric arcs are stable in the welding process, weld metal obtained after welding has excellent obdurability, the welding requirement of the Q690M hydraulic support steel is met, and large-scale development and application of the high-strength hydraulic support steel can be promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of high-strength welding materials for coal mine hydraulic supports, and specifically relates to a submerged arc welding wire matched with Q690M coal mine hydraulic support steel and a preparation method thereof, wherein the weld metal has a yield strength of ≥700 MPa, a tensile strength of 810-910 MPa, an elongation of ≥22%, and a low-temperature impact toughness of -40°C of ≥100 J. Background Art

[0002] As coal mining develops towards deeper, higher mining heights and complex geological conditions, steel-structured hydraulic supports for coal mines face more severe challenges such as high ground pressure and strong impact tendency. Traditional low-strength steel (such as Q460) can no longer meet the requirements of high load-bearing, lightweight and long life. Compared with Q460, the strength of Q690M strength grade hydraulic support steel is nearly 50% higher. Under the same load-bearing capacity, the thickness of the structure can be reduced by 20%~30%. It not only reduces the deadweight of the support and facilitates underground transportation and installation, but also reduces the amount of steel by 10%~15%, prolongs the service life, and has both economic and environmental benefits.

[0003] In recent years, many units have explored the application of Q690M in the main load-bearing structural parts such as the top beam, base, and shield beam of coal mine hydraulic support. The main load-bearing components are mainly thick-gauge (≥20 mm) steel plates, and the submerged arc welding method is generally used. In order to ensure the safety of the entire component, the submerged arc welding weld not only needs to match the strength of the parent material, but also should have excellent low-temperature toughness and weld metallurgical quality. However, due to the high strength of Q690M steel, a large number of strengthening elements are added to the existing submerged arc welding wire to ensure strength matching, which leads to a significant reduction in weld toughness, and it is difficult to balance the strength and toughness of the weld metal. In addition, the weld metallurgical quality problems occur frequently, and the flaw detection pass rate of the joint is low. The existing high-strength Q690M steel submerged arc welding wire has poor weld metallurgical quality and mechanical properties, which seriously restricts the development and application of high-strength hydraulic support steel. It is urgent to develop submerged arc welding wires matching Q690M hydraulic support steel to meet the actual application needs of the project.

[0004] There is almost no research report on submerged arc welding wire for hydraulic support of this strength level in China. Other types of submerged arc welding wire with the same strength as the parent material are generally used for welding. The applicant studied the domestically disclosed high-strength submerged arc welding wire patents: Invention patent CN103846571B discloses a high-performance X100 pipeline steel submerged arc welding wire and its application, providing a submerged arc welding wire with a yield strength of 690MPa and a tensile strength higher than 780MPa, and its chemical composition is controlled according to the following requirements by mass percentage (wt.%): C: 0.01-0.05, Mn: 1.4-2.1, Si: 0.1-0.3, Mo: 0.2-0.4, Ti: 0.05-0.1, B: 0.003-0.005, Cr: 0.1-0.4, Cu: 0.2-0.3, Ni: 0.3-0.6, Nb: 0.03-0.08, S<0.005, P<0.005. The welding wire achieves high strength of the weld mainly through the alloying effect of Mn, Mo, B, and Nb, but the high content of B element easily leads to an increase in hardening tendency, and the increase in Nb content will increase the size and number of M / A components. In addition, although the toughness of the welding wire at -20°C is good, the Ni content in the welding wire is low, and as the temperature drops to -40°C, it may not be able to ensure excellent low-temperature toughness.

[0005] Invention patent CN103084752B discloses a high-strength and high-toughness submerged arc welding wire for X100 pipeline steel, whose chemical composition (by mass percentage of chemical composition) is C: 0.01-0.06, Si: 0.30-0.50, Mn: 1.20-1.80, Cr: 0.20-0.50, Ni: 1.50-3.00, P < 0.010, S < 0.005, Ti: 0.01-0.10, Mo: 0.30-0.60, B: 0.001-0.008, Al: 0.01-0.03, Nb: 0-0.06. The welding wire optimizes the ratio of alloy elements to control C+Mn / 10 at 0.18-0.20% and Al+Ti+10B at 0.10-0.115%, which can effectively ensure high strength and toughness. However, the welding wire contains a certain amount of Al. Due to its strong deoxidation effect during welding, it will combine with oxygen and may form a large number of irregular inclusions, or compound with silicate inclusions to form large-sized inclusions, which seriously reduce the bonding strength with the matrix. At the same time, 0.3~0.5 Si is added to the welding wire. If the transition of the flux is considered, the Si content in the weld is estimated to be between 0.45~0.65, which will increase the size and number of M / A components in the organization. If Nb is added to the welding wire, the size of the M / A component will increase further. Therefore, the weld after welding with this welding wire may contain a large number of irregular inclusions and hard and brittle phase M / A components.

[0006] Invention patent CN108247234B discloses a submerged arc welding wire for high-strength steel and a preparation method thereof, wherein the composition (by mass percentage of chemical composition) is C: 0.05-0.09, Mn: 0.6-1.0, Si≤0.10, P<0.01, S≤0.005, Cu: 0.5-1.0, Ni: 0.5-1.0, Cr: 0.3-0.5, Mo: 0.1-0.2, Ti: 0.03-0.05, B: 0.0025-0.005. Through the welding wire embodiment, it can be found that the tensile strength of the welding wire is above 700MPa, and the impact value at -20℃ is not less than 120 J. However, the Cu and B contents in the welding wire are relatively high, and although the strength can be guaranteed, the stiffness of the welding wire will be large during the welding process. The problem of high hardening tendency caused by the addition of the above elements will also increase the risk of welding cracks. At the same time, the content of Ni and Mo in the welding wire is relatively low, and it is difficult for the welding wire to ensure low-temperature toughness at -40°C.

[0007] In addition, the welding wire of the above patents, while adding a large amount of alloying elements to improve the strength and toughness of the weld, failed to fully consider the difficulty of preparing the welding wire. The addition of element B will increase the hardening tendency, and its combined addition with elements such as Cu, Cr, and Ni will increase the difficulty of drawing the welding wire and increase the cost of preparing the welding wire. The addition of high alloying elements makes the metallurgical reaction of the molten pool more complicated, which is easy to increase the viscosity of the molten pool and inhibit the removal of gas and inclusions. Therefore, the deoxidation of alloying elements in high-alloy welds and the metallurgical quality of welds are also worthy of attention. Summary of the invention

[0008] The present invention aims to solve the problem that the existing Q690M hydraulic support steel submerged arc welding weld is difficult to achieve both excellent strength and toughness and metallurgical quality, and the welding wire preparation cost is high. A submerged arc welding wire and a preparation method for a coal mine hydraulic support with high strength and toughness of the weld are provided. By optimizing the component ratio and the preparation method, the welding wire preparation process is simple and does not require annealing treatment. When used with a sintered flux commonly used in engineering, the arc is stable during the welding process, and the weld metal has excellent strength and toughness after welding, and can be suitable for the welding of Q690M hydraulic support steel.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is: a submerged arc welding wire for coal mine hydraulic support with high strength and toughness of the weld, the chemical composition of the submerged arc welding wire includes, by mass percentage: C: 0.09~0.15, Si: 0.05~0.10, Mn: 1.81~2.30, P≤0.010, S≤0.005, Cr: 0.20~0.45, Ni: 2.30~2.49, Cu: 0~0.09, Mo: 0.51~0.90, Ti≤0.020, Ca≤0.015, V≤0.025, Zr≤0.015, O≤0.004, N≤0.006, the balance is Fe and other unavoidable impurities, among which the five harmful elements Pb+Sn+As+Sb+Bi≤0.010.

[0010] Furthermore, the chemical composition of the submerged arc welding wire satisfies 0.01≤Sp≤0.11, Sp is a relationship formula for regulating liquid-solid phase precipitation particles, Sp=(9V+3Ti) / (1.5Si+Mn+2Ti+5Zr+7Ca).

[0011] Furthermore, the chemical composition of the submerged arc welding wire satisfies 810≤Rm≤910, where Rm is a relationship formula for regulating strength, Rm=9.8×(36+61.32[C]+4.8[Si]+6.9[Mn]+5.5[Cr]+5.1[Ni]+11.03[Cu]+19.6[Mo]+41.6[Ti+Ca+V+Zr]).

[0012] Furthermore, the chemical composition of the submerged arc welding wire contains two or three of the trace elements Ti, Ca, V, and Zr.

[0013] Furthermore, the submerged arc welding wire has a basicity of 2.0≤B Ⅱ For sintered flux with W≤2.2, under the process conditions of heat input of 20~40 kJ / cm, the yield strength of weld metal shall be ≥700Mpa, the tensile strength shall be between 810~910 MPa, the elongation shall be ≥22%, and the low temperature impact toughness at -40℃ shall be ≥100J.

[0014] Furthermore, the 1mm thickness of the weld metal 2 The proportion of inclusions larger than 1 micron in the weld zone shall not exceed 10%, and the proportion of acicular ferrite in the columnar crystal zone of the weld shall not be less than 75%.

[0015] The present invention also provides a method for preparing a coal mine hydraulic support submerged arc welding wire with high weld strength and toughness, comprising the following steps: (1) Preparation of wire rod for welding wire: Smelting welding wire steel according to the chemical composition and proportion of submerged arc welding wire to prepare ingots with composition meeting the requirements; then forging at 1000-1100 °C, heat preservation at 1100-1200 °C for 2 h, dephosphorization at 1020-1050 °C, finish rolling at 860-920 °C, and diameter reduction at 780-800 °C to prepare wire rod for submerged arc welding wire with a diameter of φ 6.5 mm; (2) Preparation of welding wire by wire rod drawing: The diameter of the φ6.5 mm wire rod is reduced on the welding wire production line to obtain a φ4.0 mm submerged arc welding wire, without annealing treatment in the intermediate process; (3) Copper plating of welding wire: The surface of the submerged arc welding wire is evenly plated with copper by chemical method to obtain the finished submerged arc welding wire.

[0016] Furthermore, the φ6.5 mm wire rod was reduced three times to obtain the φ4.0 mm submerged arc welding wire, and the diameters after the three reductions were φ5.5 mm, φ4.8 mm and φ4.0 mm respectively.

[0017] Furthermore, the copper plating thickness is 0.15 to 0.18 micrometers.

[0018] The beneficial effects of the present invention are as follows: (1) by rationally designing the chemical composition, under the process conditions of 20-40 kJ / cm heat input, the yield strength of the weld metal is ≥700 MPa, the tensile strength is between 810-910 MPa, the elongation is ≥22%, and the low-temperature impact toughness at -40°C is ≥100 J; (2) the welding wire preparation process is simple, no annealing treatment is required, and when used with the sintered flux commonly used in engineering, the arc is stable during the welding process, and the weld metal has excellent strength and toughness after welding, which meets the welding requirements of Q690M hydraulic support steel and can promote the large-scale development and application of high-strength hydraulic support steel.

[0019] The present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a comparison chart of the weld formation and radiographic flaw detection results of the submerged arc welding wire embodiment of the present invention and the comparative example. Figure 1 In the figure, a1 is the observation diagram of the weld seam formation of the submerged arc welding wire of Example 1, a2 is the radiographic flaw detection result diagram of the submerged arc welding wire of Example 1, b1 is the observation diagram of the weld seam formation of the submerged arc welding wire of Comparative Example 1, and b2 is the radiographic flaw detection result diagram of the submerged arc welding wire of Comparative Example 1.

[0021] Figure 2 Observation diagram of typical inclusions in the welds of the submerged arc welding wire embodiments of the present invention and the submerged arc welding wire of the comparative example. Figure 2 In the figure, a is the submerged arc welding weld inclusion diagram of Example 2, and b is the submerged arc welding weld inclusion diagram of Comparative Example 2.

[0022] Figure 3 It is a comparison diagram of the microstructure of the columnar crystal zone and the heat affected zone of the weld of the submerged arc welding wire embodiment of the present invention and the comparative example. Figure 3In the figure, a1 is the microstructure diagram of the columnar crystal zone of the submerged arc welding wire weld in Example 4, a2 is the microstructure diagram of the heat affected zone of the submerged arc welding wire weld in Example 4, b1 is the microstructure diagram of the columnar crystal zone of the submerged arc welding wire weld in Comparative Example 3, and b2 is the microstructure diagram of the heat affected zone of the submerged arc welding wire weld in Comparative Example 3. DETAILED DESCRIPTION

[0023] The invention provides a coal mine hydraulic support submerged arc welding wire with high strength and toughness of weld seams. The chemical components in the submerged arc welding wire include, by mass percentage, C: 0.09-0.15, Si: 0.05-0.10, Mn: 1.81-2.30, P≤0.010, S≤0.005, Cr: 0.20-0.45, Ni: 2.30-2.49, Cu: 0-0.09, Mo: 0.51-0.90, Ti≤0.020, Ca≤0.015, V≤0.025, Zr≤0.015, O≤0.004, N≤0.006, and the balance is Fe and other inevitable impurities.

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

[0025] C: C can improve strength, but too high a content will reduce weldability and toughness. The C content of the present invention is relatively low, which can reduce cracks during wire rod rolling and wire drawing, improve drawing stability, and combine with other alloying elements to improve the strength of the weld metal. The C content in the present invention is 0.09-0.15%, preferably 0.10-0.12%.

[0026] Si: Silicon is one of the main deoxidizers in the welding process, but when its content is high, large-sized silicate inclusions and M / A components are easily generated. Considering the transition of Si from the flux to the weld, the amount of Si added to the welding wire is relatively low. In addition, its low content can reduce the risk of wire breakage during wire drawing and reduce the hardness of the wire rod and the welding wire. The content of Si in the present invention is 0.05-0.10%, preferably 0.06-0.09%, and more preferably 0.07-0.08%.

[0027] Mn: Manganese can significantly improve the strength and hardness of the weld metal, promote deoxidation and desulfurization, and improve hot working properties. Increasing the Mn content can reduce hot brittleness during rolling, but it may cause segregation and work hardening during drawing. When excessive, the wire drawing may require appropriate annealing treatment, increasing the cost of wire drawing. In the present invention, the Mn content is 1.81-2.30%, preferably 1.86-2.25%, and more preferably 1.95-2.12%.

[0028] P and S are generally considered to be harmful in welds, so their contents are reduced as much as possible. The present invention controls P≤0.010% and S≤0.005%, which can reduce hot brittleness and cold brittleness, improve rolling and drawing processability, and improve the toughness and metallurgical quality of welds.

[0029] Cr: Chromium can improve the strength of the weld and the stiffness of the welding wire, but its increase will increase the oxidation tendency, and the temperature needs to be more accurately controlled during rolling. Moreover, too high a Cr content will also increase the M / A component and increase the hardness. In the present invention, the Cr content is 0.20-0.45%, preferably 0.28-0.43%, and more preferably 0.35-0.40%.

[0030] Ni: Nickel is the key to ensure that the welding wire has stable low-temperature toughness and can reduce brittleness. However, high nickel will significantly increase the viscosity of the molten pool, deteriorate the metallurgical quality of the weld, and there may also be a risk of segregation during the drawing process. The content of Ni in the present invention is 2.30-2.49%, preferably 2.31-2.48%, and more preferably 2.36-2.45%.

[0031] Cu: The addition of copper to the welding wire can improve the processability, and fine Cu-rich precipitation can also play a precipitation strengthening role. However, when the copper content is high, it may cause hot brittleness of the weld. Considering the copper plating of the welding wire and the effects of other elements, Cu is added in a trace amount in the present invention, and the content is 0-0.09%, preferably 0.03-0.08%, and more preferably 0.05-0.06%.

[0032] Mo: Mo can play a significant role in grain refinement and improve strength and toughness at the same time, but when its content increases, it may increase the deformation resistance during rolling and make drawing difficult. If its content is too high, it will also cause the size and number of M / A components to increase. In the present invention, the content of Mo is 0.51-0.90%, preferably 0.59-0.87%, and more preferably 0.65-0.74%.

[0033] Ti: Titanium is a strong deoxidizer in the weld, which can protect Si and Mn from oxidation. The micron-sized Ti oxide inclusions formed by its oxidation reaction can promote the nucleation of acicular ferrite, refine the weld metal, and the nano-sized oxides pin the original austenite grain boundaries. However, when its content is high, it will increase the size of the inclusions and reduce the bonding ability between the matrix and the inclusions in the weld. In the present invention, the content of Ti is ≤0.020%, preferably 0.008~0.017%, and more preferably 0.010~0.012%.

[0034] Ca: A trace amount of Ca is added to the welding wire to reduce the effect of residual floating rust on the steel surface on the quality of the weld, and can be combined with Ti for deoxidation to reduce the oxygen content of the weld. However, when its content increases, the metallurgical reaction of the weld will be intense, reducing the metallurgical quality of the weld, so it needs to be added in a trace amount. In the present invention, the content of Ca is ≤0.015%, preferably 0.008-0.014%, and more preferably 0.010-0.013%.

[0035] V: During the solidification process of the weld metal, vanadium can combine with C and N to form nano-scale fine particles, play a role in second phase strengthening, and can pin grain boundaries and refine austenite grains. However, when its content increases, it may also increase the risk of weld cracking, especially for high strength, so its content must be strictly controlled. In the present invention, the content of V is ≤0.025%, preferably 0.017-0.023%, and more preferably 0.019-0.020%.

[0036] Zr: In the weld, Zr can also act in combination with Ti and the like to exert deoxidation and denitrification effects, and its submicron / micron oxide inclusions also have high heterogeneous nucleation ability, and nano-level inclusions can also pin grain boundaries, but its high content may also lead to the appearance of large-sized inclusions. In the present invention, the content of Zr is ≤0.015%, preferably 0.009-0.013%, and more preferably 0.011-0.013%.

[0037] High-strength weld metal is more sensitive to pores and inclusions. To ensure the metallurgical quality and density of the weld, the contents of O and N must be strictly controlled. The content of O is ≤0.004%, and the content of N is ≤0.006%.

[0038] The five harmful elements mainly affect the embrittlement and hot cracking of grain boundaries. In high-strength welds, the content of the above five elements should be strictly limited. The five harmful elements Pb+Sn+As+Sb+Bi≤0.010%.

[0039] In addition, although Ti, Ca, V, Zr and trace elements such as O, N, C in steel can generate particles that pin the original grain boundaries and promote the heterogeneous nucleation of ferrite, when there are too many types, various inclusions or precipitated particles will compound in the liquid phase or solid phase to form large-sized inclusions or precipitated particles, which will reduce the bonding ability with the matrix and increase the risk of cracking. Therefore, two or three of Ti, Ca, V, and Zr are added to the welding wire of the present invention.

[0040] In addition to the need to reasonably control the chemical composition range of each element as mentioned above, the following innovative technical requirements must also be set to accurately control the relative addition amounts of some key elements. In order to ensure that the welding wire has both good metallurgical quality and high strength and toughness, the composition must also meet the chemical composition matching in the relationship Sp and Rm.

[0041] Sp is the relationship formula for regulating the liquid-solid phase precipitation particles, Sp = (9V + 3Ti) / (1.5Si + Mn + 2Ti + 5Zr + 7Ca) and 0.01 ≤ Sp ≤ 0.11. High-strength welds require sufficiently refined structures, but due to high strength, they are more sensitive to inclusions and precipitated particles. The increase in the size of inclusions and precipitated particles will reduce their ability to bind to the matrix. By regulating the ratio of V, Ti, Si, Mn, Ti, Zr, and Ca to meet Sp between 0.01 and 0.11, the modification of inclusions can be achieved, and the precipitated particles of the liquid-solid phase can be effectively refined. The modified inclusions become effective heterogeneous nucleation sites, which can provide a high proportion of acicular ferrite, and the refined precipitated particles can not only play a second phase strengthening role, but also pin the original austenite grain boundaries, limiting the competitive growth of acicular ferrite in a small area, and achieving a weld structure dominated by refined acicular ferrite.

[0042] Rm is a relationship formula for regulating strength, Rm=9.8×(36+61.32[C]+4.8[Si]+6.9[Mn]+5.5[Cr]+5.1[Ni]+11.03[Cu]+19.6[Mo]+41.6[Ti+Ca+V+Zr]) and 810≤Rm≤910. Since coal mine hydraulic supports may be subjected to dynamic loads during application, they are required to have good fatigue resistance. Ensuring strong or super strong matching between weld metal and parent material is the key to achieving good fatigue performance of joints. However, excessive weld strength will increase the sensitivity of fatigue crack initiation and the risk of cracking at the weld toe of the joint. By considering the alloy element transition of the flux and the burning of alloy elements during welding, it is stipulated that the element ratio Rm for controlling strength in the welding wire meets 810~910, which can effectively reduce the risk of fatigue fracture of weld metal and improve the fatigue performance of the joint.

[0043] In order to achieve the control of the entire welding process of the welding wire composition design, preparation, and welding, the present invention also provides a method for preparing the above-mentioned submerged arc welding wire.

[0044] The preparation method of submerged arc welding wire comprises the following steps: (1) Preparation of wire rod for welding wire: Smelt welding wire steel according to the chemical composition and proportion of submerged arc welding wire to prepare ingots with composition meeting the requirements; then forge at 1000-1100 ℃, keep at 1100-1200 ℃ for 2 h, dephosphorize at 1020-1050 ℃, finish roll at 860-920 ℃, and reduce at 780-800 ℃ to prepare wire rod for submerged arc welding wire with a diameter of φ6.5 mm; (2) Preparation of welding wire by wire rod drawing: Reduce the diameter of φ6.5 mm wire rod three times on the welding wire production line from φ6.5 mm to φ5.5 mm to φ4.8 mm to φ4.0 mm to prepare submerged arc welding wire. No annealing treatment is performed in the intermediate process, which can not only effectively ensure the high strength of the welding wire, but also effectively reduce the cost of the welding wire drawing process; (3) Copper plating of welding wire: The surface of the submerged arc welding wire is evenly copper plated by chemical method to obtain the finished submerged arc welding wire. The thickness of the copper plating in step (3) is 0.15 to 0.18 microns.

[0045] During welding, the submerged arc welding wire should have a basicity of 2.0 ≤ B ⅡW Sintered flux with a temperature of ≤2.2 can produce weld metal with high strength, toughness and excellent metallurgical quality under the process conditions of 20~40 kJ / cm heat input. The weld metal yield strength is ≥700Mpa, the tensile strength is between 810~910 MPa, the elongation is ≥22%, and the low temperature impact toughness at -40℃ is ≥100J. 2 The proportion of inclusions larger than 1 micron in the region is no more than 10%, and the proportion of acicular ferrite in the columnar crystal area of ​​the weld is no less than 75%. This not only improves the bonding ability between the particles and the matrix and reduces the tendency to crack, but also the high proportion of acicular ferrite in the columnar crystal provides a high-density, high-angle grain boundary, which can effectively hinder the expansion of cracks. In addition, during the secondary heating process, the high proportion of acicular ferrite can inhibit each other's growth, avoiding the formation of large-sized polygonal ferrite in the heat-affected zone of the weld, and reducing the embrittlement and softening problems of the weld.

[0046] The submerged arc welding wire of the present invention is further explained and illustrated below in conjunction with specific embodiments.

[0047] Seven furnaces of welding wire steel of the embodiment of the present invention and three furnaces of welding wire steel of the comparative example were refined 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 requirements of the present invention. The welding wire steel of the embodiment and the comparative example were melted and cast in sequence according to a certain element composition ratio to obtain a cast alloy billet, and the composition of the welding wire steel of the embodiment and the comparative example was detected according to GB / T 4336 "Spark Source Atomic Emission Spectroscopy Analysis Method for Carbon Steel and Medium and Low Alloy Steel (Conventional Method)", and the specific chemical composition is shown in Table 1.

[0048] Table 1 Chemical composition of welding wire steel of Examples 1 to 7 and Comparative Examples 1 to 3 (wt.%, balance Fe) .

[0049] The welding wire steel used in the embodiment and the comparative example was subjected to wire rod rolling, wire drawing and copper plating. Table 2 summarizes the comparative data of key process parameters in the preparation process of different welding wire steels. The results show that by adopting the welding wire preparation process provided by the present invention, the welding wire preparation of the embodiment has high stability, no wire breakage phenomenon, and the copper plating on the surface of the welding wire is stable, which improves the wire breakage problem of the comparative example welding wire during drawing.

[0050] Table 2 Main process parameters for preparing submerged arc welding wires of Examples 1 to 7 and Comparative Examples 1 to 3 .

[0051] The prepared embodiment and comparative example welding wires were subjected to welding tests of typical butt joints. The specific welding process parameters are shown in Table 3. The thickness of the welding test plate was 24 mm Q690M coal mine hydraulic support steel, with a yield strength of 736 MPa, a tensile strength of 895 MPa, an elongation of 22.5%, and an average low-temperature impact value of 234 J at -40 °C.

[0052] Table 3 Submerged arc welding process parameters of Examples 1 to 7 and Comparative Examples 1 to 3 .

[0053] During the welding process, the surface quality of the welding wires of the embodiment and the comparative example was observed, wherein the surface quality of the welds of the embodiment 1 and the comparative example 1 is shown in FIG. Figure 1 (a1) and Figure 1 (b1). The weld bead of the weld welded by the welding wire of this embodiment is straight and has a smooth surface, while the weld bead of the welding wire of the comparative example has obvious deep lines, curved weld bead and rough surface, indicating that the fluidity of the molten pool is poor, it is not fully spread, and there is an obvious slag inclusion problem. After welding, the welds of the embodiment and the comparative example were inspected by X-ray, and the results are shown respectively. Figure 1 (a2) and Figure 1 (b2). The radiographic inspection results show that the welds welded by the comparative welding wire have cracks along the weld direction and large-sized pores, while the welds of the embodiment have no obvious defects. In addition, macroscopic cross-sections of the joints were taken in the defect-free areas of the joints of the embodiment and the comparative example, and the weld composition was tested. The results are shown in Table 4.

[0054] Table 4 Chemical composition of weld metal after welding of submerged arc welding wire of Examples 1 to 7 and Comparative Examples 1 to 3 (wt.%, balance Fe) .

[0055] After the component detection is completed, the macroscopic cross section of the joint is polished with 100x~1500x sandpaper, and the inclusions are observed and photographed under a metallographic microscope. The morphology of the inclusions in Example 2 and Comparative Example 2 is shown in FIG. Figure 2 (a) and Figure 2 (b) The inclusions in the embodiment are dispersed and refined, while the inclusions in the comparative example are coarse in size, and there are also large irregular inclusions, which have weak bonding ability with the matrix. The inclusions in the 1mm2 area in the metallographic photographs of the embodiment and the comparative example were counted, and the results are shown in Table 5. In the embodiment, the inclusion size in the 1mm2 area is greater than 1μm, which is less than 7.5%. The small inclusions can effectively reduce the stress concentration problem near the inclusions and help improve the bonding strength with the matrix, while the inclusion size in the 1mm2 area of ​​the comparative example is greater than 1μm, which is more than 17%.

[0056] Table 5 Size distribution ratio of inclusions in submerged arc welding seams of Examples 1 to 7 and Comparative Examples 1 to 3 .

[0057] The macroscopic cross-sections of Examples 1 to 7 and Comparative Examples 1 to 3 were corroded with 4% nitric acid alcohol, and the microstructures of the columnar crystal area and the heat-affected zone of the submerged arc welding weld were observed under a metallographic microscope. The test results are shown in FIG. Figure 3 . The results show that: in the columnar crystal area of ​​the weld, there is no large-sized block ferrite precipitated along the grain boundary in the weld of this embodiment, and the structure is relatively uniform, mainly composed of acicular ferrite and granular bainite, while the columnar crystal area of ​​the weld of the comparative example has large-sized block ferrite, and the acicular ferrite and granular bainite in the structure are coarse. The heat affected zone of the weld refers to the area where the next weld is in the heat affected zone of the previous weld when the weld is filled, which has undergone a reheating and cooling process. Compared with the embodiment, the heat affected zone of the weld of the comparative example is mainly composed of equiaxed block ferrite, while there is still a large amount of acicular ferrite in the embodiment, and the formed block ferrite is also relatively small.

[0058] Sampling was performed on the qualified parts of the weld metal in the embodiment and the comparative example, and the mechanical properties of the weld metal were tested. The tensile properties of the weld metal were sampled and tested in accordance with GB / T 228.1, and the impact sampling and performance testing were performed in accordance with GB / T 2650. Three impact samples were taken for each sample to reduce the error. The statistical results of the mechanical properties test are shown in Table 6. The results show that the weld metal of the welding wire in this embodiment can have good strength and toughness. However, the weld of the welding wire in the comparative example has the problem of insufficient strength or insufficient toughness.

[0059] Table 6 Mechanical properties test results of weld metal after submerged arc welding of Examples 1 to 7 and Comparative Examples 1 to 3 .

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A submerged arc welding wire for coal mine hydraulic support with high weld strength and toughness, characterized in that: The chemical composition of the submerged arc welding wire includes, by mass percentage: C: 0.09~0.15, Si: 0.05~0.10, Mn: 1.81~2.30, P≤0.010, S≤0.005, Cr: 0.20~0.45, Ni: 2.30~2.49, Cu: 0~0.09, Mo: 0.51~0.90, Ti≤0.020, Ca≤0.015, V≤0.025, Zr≤0.015, 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.

010.

2. The submerged arc welding wire according to claim 1, characterized in that: The chemical composition of the submerged arc welding wire satisfies 0.01≤Sp≤0.11, wherein: Sp=(9V+3Ti) / (1.5Si+Mn+2Ti+5Zr+7Ca).

3. The submerged arc welding wire according to claim 1, characterized in that: The chemical composition of the submerged arc welding wire satisfies 810≤Rm≤910, wherein: Rm=9.8×(36+61.32[C]+4.8[Si]+6.9[Mn]+5.5[Cr]+5.1[Ni]+11.03[Cu]+19.6[Mo]+41.6[Ti+Ca+V+Zr]).

4. The submerged arc welding wire according to claim 1, characterized in that: The chemical composition of the submerged arc welding wire contains two or three of the trace elements Ti, Ca, V and Zr.

5. The submerged arc welding wire according to claim 1, characterized in that: The submerged arc welding wire has a basicity of 2.0 ≤ B ⅡW For sintered flux with a temperature range of ≤2.2, under the process conditions of heat input of 20~40 kJ / cm, the yield strength of the weld metal shall be ≥700Mpa, the tensile strength shall be between 810~910 MPa, the elongation shall be ≥22%, and the low-temperature impact toughness at -40℃ shall be ≥100J.

6. The submerged arc welding wire according to claim 5, characterized in that: 1mm in weld metal 2 The proportion of inclusions larger than 1 micron in the weld zone shall not exceed 10%, and the proportion of acicular ferrite in the columnar crystal zone of the weld shall not be less than 75%.

7. A method for preparing a submerged arc welding wire for a coal mine hydraulic support with high weld strength and toughness, based on the submerged arc welding wire according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Preparation of wire rod for welding wire: Smelting welding wire steel according to the chemical composition and proportion of submerged arc welding wire to prepare ingots with composition meeting the requirements; then forging at 1000-1100 °C, heat preservation at 1100-1200 °C for 2 h, dephosphorization at 1020-1050 °C, finish rolling at 860-920 °C, and diameter reduction at 780-800 °C to prepare wire rod for submerged arc welding wire with a diameter of φ 6.5 mm; (2) Preparation of welding wire by wire rod drawing: The diameter of the φ6.5 mm wire rod is reduced on the welding wire production line to obtain a φ4.0 mm submerged arc welding wire, without annealing treatment in the intermediate process; (3) Copper plating of welding wire: The surface of the submerged arc welding wire is evenly plated with copper by chemical method to obtain the finished submerged arc welding wire.

8. The preparation method according to claim 7, characterized in that: The φ6.5 mm wire rod is reduced three times to obtain φ4.0 mm submerged arc welding wire. The diameters after three reductions are φ5.5 mm, φ4.8 mm and φ4.0 mm respectively.

9. The preparation method according to claim 7, characterized in that: The thickness of the copper plating is 0.15 to 0.18 microns.

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