A low-cost and high-strength self-shielded metal cored wire, welding wire, deposited metal, and their preparation methods and applications

Abstract

The present invention discloses a low-cost, high-strength, self-shielded metal powder core, welding wire, deposited metal, and its preparation method and application. The metal powder core comprises the following components by mass: C 0.130% to 0.190%, B 0.69% to 0.76%, Cr 0.015% to 0.038%, Mn 3.80% to 4.05%, Si 1.02% to 1.15%, Al 0.15% to 0.24%, O 0.005% to 0.020%, N 0.032% to 0.085%, with the balance being Fe. The deposited metal of the welding wire of the present invention has a ferrite matrix structure, with Fe2B and Fe3(C,B) boron-carbon compounds present at the grain boundaries, as well as dispersed inclusions primarily consisting of AlN, Al2O3, and MnO. The metal powder core exhibits a tensile strength of 850 to 950 MPa, an elongation of 14 to 18%, and a hardness of HV508-550.

Description

Technical Field

[0001] The present invention belongs to the field of welding in material processing engineering, and specifically relates to a low-cost, high-strength self-shielded metal powder core, welding wire, deposited metal, and a preparation method and application thereof. Background Art

[0002] In recent years, high-strength steel, due to its high strength and ability to withstand heavy loads and high pressure, has been widely used in large welded structures subjected to high loads. With the continuous emergence of new high-strength steel grades, the requirements for weld strength are becoming increasingly stringent, and therefore the performance requirements for supporting welding materials are also increasing. As the material foundation of high-strength steel welding processes, the development and selection of high-strength steel welding consumables have a direct and significant impact on the overall performance of high-strength steel components.

[0003] As the strength level of high-strength steel increases, weldability decreases, welding becomes more difficult, plasticity and toughness deteriorate, and crack sensitivity increases. Therefore, it is urgent to develop special high-strength welding materials that meet the requirements of high-strength steel welding through rational composition design and optimized formulation.

[0004] Metal-powder-cored welding wire facilitates the addition and adjustment of alloying components, creating a wide range of compositional options for increasing strength. Furthermore, because no slag-forming agents are added, the hydrogen content is extremely low, a significant advantage in preventing cold cracking during welding. Metal-powder-cored welding wire offers similar performance to solid wire, resulting in aesthetically pleasing weld beads and the elimination of slag removal for multi-layer welding. However, shielding gas is generally required.

[0005] Compared to gas-shielded metal-cored welding wire, the development of self-shielded metal-cored welding wire is significantly more challenging, primarily due to the lack of a slag-forming agent in the flux core. The high strength of steel requires the strengthening effects of numerous alloying elements. The primary technical challenges currently faced are how to reduce or even eliminate the addition of expensive elements such as Cr, Mo, and Ni in the welding wire formulation to achieve low-cost, high-strength welding wire; and how to achieve self-shielding by controlling metallurgical reactions to suppress the negative effects of inclusions without a slag-forming agent. Summary of the Invention

[0006] Purpose of the invention: The technical problem to be solved by the present invention is to provide a low-cost, high-strength, self-protected metal powder core.

[0007] The technical problem that the present invention also aims to solve is to provide a low-cost, high-strength self-shielded metal powder cored welding wire and a preparation method and application thereof.

[0008] The final technical problem to be solved by the present invention is to provide low-cost, high-strength self-shielded metal powder cored welding wire deposited metal and its preparation method and application.

[0009] Technical solution: In order to solve the above technical problems, the present invention provides a metal powder core, which comprises the following components in mass percentage: C 0.130% to 0.190%, B 0.69% to 0.76%, Cr 0.015% to 0.038%, Mn 3.80% to 4.05%, Si 1.02% to 1.15%, Al 0.15% to 0.24%, O 0.005% to 0.020%, N 0.032% to 0.085%, and the balance is Fe.

[0010] The present invention also includes the use of the metal powder core in preparing low-cost, high-strength self-shielded metal powder cored welding wire or its deposited metal.

[0011] The present invention also includes a low-cost, high-strength, self-shielded metal powder cored welding wire, which includes the metal powder core.

[0012] The present invention also includes a low-cost, high-strength, self-shielded metal powder cored welding wire deposited metal, wherein the metal powder cored welding wire deposited metal is prepared by using the metal powder core or the metal powder cored welding wire.

[0013] The matrix structure of the deposited metal is ferrite, Fe2B and Fe3(C,B) boron-carbon compounds exist at the grain boundaries, and there are also dispersed inclusions, the main types of which are AlN, Al2O3, and MnO.

[0014] The deposited metal has a tensile strength of 850-950 MPa, an elongation of 14-18%, and a hardness of HV508-550.

[0015] The present invention also includes a method for preparing a low-cost, high-strength, self-shielded metal powder cored welding wire, comprising the following steps:

[0016] (1) preparing a low-carbon steel strip and rolling the low-carbon steel strip into a U-shaped strip using a U-shaped die;

[0017] (2) placing the metal powder core into a U-shaped steel strip and closing it with a die to form a thick welding wire;

[0018] (3) The thick welding wire prepared in step (2) is passed through a wire drawing die, and is drawn and reduced in diameter step by step until its diameter reaches one of 1.6 and 1.2 mm, thereby obtaining a final product.

[0019] The present invention also includes a method for preparing the deposited metal of the low-cost, high-strength self-shielded metal powder cored welding wire, which is characterized by comprising the following steps:

[0020] (1) Using the self-shielded metal powder cored welding wire, arc surfacing is performed on a Q235 low carbon steel plate, with the number of surfacing layers being 6-10;

[0021] (2) The welding process parameters used in multi-layer arc welding are: welding current 240-280A, welding voltage 24-28V, and welding speed 0.25m / min;

[0022] (3) Use wire cutting to cut more than 6 layers of weld bead, which is the deposited metal of self-shielded metal cored wire.

[0023] The present invention also includes the application of the self-shielded metal-cored welding wire or the deposited metal of the metal-cored welding wire in mining machinery, petrochemical industry or metallurgical industry.

[0024] Among them, the specific applications include the repair and remanufacturing of equipment wear-resistant parts.

[0025] The main functions of the elements in the above welding wire of the present invention are as follows:

[0026] Boron (B) is one of the main alloying elements in Fe-BC-Cr alloys. Its atomic number is 5, so B shares many similar properties with its neighboring C atom in the periodic table. In the weld overlay, B often forms borides and boron-carbon compounds with other alloying elements, exhibiting high hardness and thermal stability. These borides often serve as a wear-resistant skeleton, enhancing the wear resistance of the weld overlay.

[0027] Because the self-shielded metal-cored wire does not contain any graphite and relies solely on a small amount of carbon in the wire coating, the deposited metal is a hypoeutectic alloy. According to the Fe-B binary phase diagram, as the overlay alloy cools from the high temperature of welding to room temperature, the primary austenite γ-Fe phase first precipitates from the liquid phase and then grows in the form of dendrites.

[0028] L→γ-Fe

[0029] Since the solubility of B in the γ-Fe phase is only 0.02wt.%, and the distribution coefficients of alloying elements such as B, C, and Mn in austenite are less than 1, the γ-Fe phase gradually pushes the excess B and C atoms to the surrounding area during its growth, causing a B-rich region to form in the liquid phase around the γ-Fe phase. As B atoms are continuously expelled, when the concentration of B atoms around the γ-Fe phase reaches 3.8% and the temperature drops to the eutectic temperature (1149°C), a eutectic reaction occurs:

[0030] L→γ-Fe+Fe2B

[0031] At this point, the liquid phase disappears completely, and Fe2B type eutectic borides begin to form in the austenite grain boundaries. At a higher cooling rate, the borides usually grow in the form of fishbone. As the temperature continues to drop to 910℃, the eutectoid reaction begins to occur:

[0032] γ-Fe→α-Fe+Fe2B

[0033] At this point, α-Fe forms near the grain boundaries. As the temperature continues to decrease, the solubility of γ-Fe in elements B and C also decreases, and elements B and C continue to diffuse into the γ-Fe grain boundaries. Due to the low grain boundary energy of γ-Fe, granular or massive boron-carbon compounds Fe3(C,B) begin to form between the γ-Fe and Fe2B phases.

[0034] γ-Fe→α-Fe+Fe3(C, B)

[0035] As the temperature continues to drop, the structure no longer undergoes transformation, and the final solidified structure consists of α-Fe phase, eutectic boride, and boron-carbon compound. Alloying elements such as Mn and Cr will dissolve in the Fe2B phase to form M2B-type boride, which has higher hardness.

[0036] According to the calculated isothermal cross-section of the Fe-Cr-B alloy at 1373K, Cr accumulates at the grain boundaries and dissolves in borides to form Fe2B-Cr2B (IA / mcm). Cr can also dissolve in carbides to form (Fe,Cr)3(C,B), improving the strength and hardness of the alloy matrix.

[0037] According to the Fe-CB ternary alloy phase diagram, the Fe-CB system exhibits three distinct binary eutectic reactions: L→Fe3C+Fe2B, L→γ-Fe+Fe2B, and L→γ-Fe+Fe3C. A eutectic reaction occurs when crossing the phase region: L+Fe2B→Fe3(B,C). After the peritectic reaction, three equilibrium phase regions exist in the alloy: γ-Fe+Fe2B+Fe3(B,C) and L+γ-Fe+Fe3(B,C). As the temperature continues to decrease, the remaining liquid phase undergoes another eutectic reaction: L→γ-Fe+Fe3(B,C) until 1100°C, when all the liquid phase has transformed into γ-Fe+Fe2B+Fe3(B,C).

[0038] In high-boron iron-based alloys, manganese is the most abundant alloying element, besides iron. In addition to its deoxidizing effect, manganese also acts as an austenite stabilizer, expanding the austenite region and lowering the γ-Fe to α-Fe transformation temperature. The austenite transformation at lower temperatures inhibits the formation of proeutectoid ferrite (PF) and lateral lath ferrite (SF) in the high-temperature transformation region. Studies have shown that at appropriate cooling rates, manganese can inhibit the formation of pearlite in the weld metal. Furthermore, a 1% increase in manganese in the weld deposit increases the weld tensile strength by 100 MPa. However, excessive manganese increases the weld's tendency to harden, leading to the formation of brittle, hard structures such as martensite and bainite after welding, significantly reducing impact toughness.

[0039] Unlike Mn, which is an austenite stabilizing element, Si is a ferrite forming element. The addition of Si is beneficial to the formation of ferrite grain boundaries. Therefore, Mn and Si need to be considered together. The formula for the influence of Mn and Si on weld strength is:

[0040] R m =801+91ω(Mn)+228ω(Si)-10[ω(Si)] 2

[0041] Si can dissolve in ferrite, playing a role in solid solution strengthening and dispersion strengthening in the deposited metal matrix, thereby increasing the strength of the deposited metal. In addition, some Si also plays a deoxidizing role.

[0042] It is particularly noteworthy that some of the products of Al deoxidation and nitrogen fixation and Mn deoxidation are present in the deposited metal, forming fine, dispersed inclusions. These inclusions, regardless of their shape and size, do not appear to reduce the strength of the deposited metal. Instead, they induce the formation of acicular ferrite with large-angle grain boundaries and a high dislocation density, contributing to its strength. These inclusions both offset the oxidation effects of the absence of an external shielding gas and also have a beneficial effect on the strength of the deposited metal, a technical feature of this welding wire.

[0043] In summary, the formation of Fe2B grain boundaries and Fe3(C,B) boron-carbon compounds by a large amount of B is the primary reason for the increased strength of the deposited metal. The mechanical moduli of the hard phases were calculated by fitting the equation of state: Fe2B has a bulk modulus (B) of 224.3 GPa, a shear modulus (G) of 103.5 GPa, and a Young's modulus (E) of 269.2 GPa; Fe3C has a bulk modulus (B) of 175.2 GPa, a shear modulus (G) of 80.8 GPa, and a Young's modulus (E) of 210.1 GPa. Therefore, both Fe2B and Fe3C hard phases possess high strength. In the Fe-BC-Cr self-shielded metal powder cored wire deposited metal, alloying elements such as Cr and Mn dissolve in the Fe2B phase to form M2B borides, while B dissolves in the Fe3C phase to form Fe3(C,B) iron-boron compounds, further enhancing the strength of the deposited metal. Nitrogen is the most effective solid solution strengthening element and low-cost alloying element. Since there is no external protective gas, it penetrates directly from the air. When the N content is too high, nitrogen pores will be generated, and when the N content is too low, the strength will decrease.

[0044] From the above technical solution and the brief description of the role of each component in the welding wire, it can be understood that C and N increase strength, B is the main element for the in-situ generation of Fe2B and is also the main strengthening element of the matrix, and the relatively small content of Cr promotes the formation of a ferrite matrix and dissolves in the matrix. Mn partially participates in deoxidation and also plays a role in solid solution strengthening, thereby increasing the strength and hardness of the deposited metal. Si deoxidizes and strengthens the deposited metal by alloying. Fe forms a ferrite matrix and reacts with B to form Fe2B. The deoxidation products form fine and dispersed inclusions, which induce ferrite nucleation and increase strength. The synergistic strengthening of multiple alloying elements ultimately results in a low-cost, high-strength, self-shielded metal powder cored welding wire.

[0045] Beneficial Effects: The flux-cored welding wire of the present invention achieves both self-shielding properties and alloy strengthening through the simultaneous addition of multiple alloying elements at low cost. The deposited metal matrix of the wire is ferrite, with Fe2B and Fe3(C,B) boron-carbon compounds present at the grain boundaries, as well as dispersed inclusions primarily composed of AlN, Al2O3, and MnO. The wire achieves a tensile strength of 850-950 MPa, an elongation of 14-18%, and a hardness of HV508-550, achieving both low cost and high strength for a self-shielded metal powder-cored welding wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is the XRD phase analysis result of Example 1;

[0047] Figure 2 is a microstructure diagram of Example 1;

[0048] Figure 3 is the AlN topography of Example 1;

[0049] Figure 4 This is the Al2O3 morphology of Example 1. DETAILED DESCRIPTION

[0050] The present invention can be better understood with reference to the following examples. However, the specific drug core component ratios, process conditions, and results described in the examples are only for illustrating the present invention and should not and will not limit the present invention described in detail in the claims.

[0051] Example 1

[0052] A low-cost, high-strength, self-protective metal powder core comprises the following components by mass percentage: C 0.164%, B 0.71%, Cr 0.033%, Mn 3.93%, Si 1.04%, Al 0.19%, O 0.020%, N 0.054%, and Fe 93.859%.

[0053] The method for preparing a flux-cored welding wire provided in this embodiment includes the following steps: preparing a low-carbon steel strip, rolling the low-carbon steel strip into a U-shaped strip using a U-shaped die; placing a flux core into the U-shaped steel strip, and closing the strip with a die to form a thick welding wire; passing the prepared thick welding wire through a wire drawing die, drawing and reducing the diameter step by step, and finally making the diameter reach 1.6 mm to obtain the final product.

[0054] The self-shielded metal powder cored welding wire deposited metal of this embodiment is prepared by using the aforementioned self-shielded metal powder cored welding wire, and arc surfacing is performed on Q235 low carbon steel plate, with the number of surfacing layers being 6-10 layers, without the need for external shielding gas. The welding process parameters used in multi-layer arc welding are: welding current of 240-280A, welding voltage of 24-28V, and welding speed of 0.25m / min. The portion above 6 layers of the weld is cut by wire cutting, which is the self-shielded metal powder cored welding wire deposited metal. The XRD phase analysis results of the deposited metal are shown in Figure 2. Figure 1 As shown, the microstructure Figure 2 As shown, the AlN morphology is as follows Figure 3 As shown, the morphology of Al2O3 is as follows Figure 4 The pore sensitivity, strength and hardness values are shown in Table 1.

[0055] Example 2

[0056] A low-cost, high-strength, self-protective metal powder core comprises the following components by mass percentage: C 0.13%, B 0.72%, Cr 0.038%, Mn 4.01%, Si 1.09%, Al 0.2%, O 0.01%, N 0.043%, and Fe 93.759%.

[0057] The method for preparing a flux-cored welding wire provided in this embodiment includes the following steps: preparing a low-carbon steel strip, rolling the low-carbon steel strip into a U-shaped strip using a U-shaped die; placing a flux core into the U-shaped steel strip, and closing it with a die to form a thick welding wire; passing the thick welding wire prepared in step 2 through a wire drawing die, drawing and reducing the diameter step by step, and finally making it reach a diameter of 1.6 mm to obtain the final product.

[0058] The self-shielded metal-cored welding wire deposit of this example was prepared using the aforementioned self-shielded metal-cored welding wire. Arc cladding was performed on Q235 mild steel plates, with 6-10 layers, without the need for external shielding gas. The welding process parameters used for multi-layer arc welding were: welding current of 240-280A, welding voltage of 24-28V, and welding speed of 0.25m / min. The weld bead with more than 6 layers was cut using wire cutting to obtain the self-shielded metal-cored welding wire deposit. Porosity sensitivity, strength, and hardness values are shown in Table 1.

[0059] Example 3

[0060] A low-cost, high-strength, self-protective metal powder core comprises the following components by mass percentage: C 0.181%, B 0.75%, Cr 0.027%, Mn 3.8%, Si 1.11%, Al 0.21%, O 0.005%, N 0.064%, and Fe 93.853%.

[0061] The method for preparing a flux-cored welding wire provided in this embodiment includes the following steps: preparing a low-carbon steel strip and rolling the low-carbon steel strip into a U-shaped strip using a U-shaped die; placing a flux core into the U-shaped steel strip and closing it with a die to form a thick welding wire; passing the thick welding wire prepared in step 2 through a wire drawing die, drawing and reducing the diameter step by step, and finally making the diameter reach 1.2 mm to obtain the final product.

[0062] The self-shielded metal-cored welding wire deposit of this example was prepared using the aforementioned self-shielded metal-cored welding wire. Arc cladding was performed on Q235 mild steel plates, with 6-10 layers, without the need for external shielding gas. The welding process parameters used for multi-layer arc welding were: welding current of 240-280A, welding voltage of 24-28V, and welding speed of 0.25m / min. The weld bead with more than 6 layers was cut using wire cutting to obtain the self-shielded metal-cored welding wire deposit. Porosity sensitivity, strength, and hardness values are shown in Table 1.

[0063] Example 4

[0064] A low-cost, high-strength, self-protective metal powder core comprises the following components by mass percentage: C 0.19%, B 0.69%, Cr 0.015%, Mn 3.98%, Si 1.02%, Al 0.22%, O 0.02%, N 0.032%, and Fe 93.833%.

[0065] The method for preparing a flux-cored welding wire provided in this embodiment includes the following steps: preparing a low-carbon steel strip, rolling the low-carbon steel strip into a U-shaped strip using a U-shaped die; placing a flux core into the U-shaped steel strip, and closing the strip with a die to form a thick welding wire; passing the prepared thick welding wire through a wire drawing die, drawing and reducing the diameter step by step, and finally making the diameter reach 1.2 mm to obtain the final product.

[0066] The self-shielded metal-cored welding wire deposit of this example was prepared using the aforementioned self-shielded metal-cored welding wire. Arc cladding was performed on Q235 mild steel plates, with 6-10 layers, without the need for external shielding gas. The welding process parameters used for multi-layer arc welding were: welding current of 240-280A, welding voltage of 24-28V, and welding speed of 0.25m / min. The weld bead with more than 6 layers was cut using wire cutting to obtain the self-shielded metal-cored welding wire deposit. Porosity sensitivity, strength, and hardness values are shown in Table 1.

[0067] Example 5

[0068] A low-cost, high-strength, self-protective metal powder core comprises the following components by mass percentage: C 0.175%, B 0.76%, Cr 0.026%, Mn 4.05%, Si 1.15%, Al 0.24%, O 0.006%, N 0.085%, and Fe 93.508%.

[0069] The method for preparing a flux-cored welding wire provided in this embodiment includes the following steps: preparing a low-carbon steel strip, rolling the low-carbon steel strip into a U-shaped strip using a U-shaped die; placing a flux core into the U-shaped steel strip, and closing it with a die to form a thick welding wire; passing the thick welding wire prepared in step 2 through a wire drawing die, drawing and reducing the diameter step by step, and finally making it reach a diameter of 1.6 mm to obtain the final product.

[0070] The self-shielded metal-cored welding wire deposit of this example was prepared using the aforementioned self-shielded metal-cored welding wire. Arc cladding was performed on Q235 mild steel plates, with 6-10 layers, without the need for external shielding gas. The welding process parameters used for multi-layer arc welding were: welding current of 240-280A, welding voltage of 24-28V, and welding speed of 0.25m / min. The weld bead with more than 6 layers was cut using wire cutting to obtain the self-shielded metal-cored welding wire deposit. Porosity sensitivity, strength, and hardness values are shown in Table 1.

[0071] Example 6

[0072] A low-cost, high-strength, self-protective metal powder core comprises the following components by mass percentage: C 0.186%, B 0.76%, Cr 0.032%, Mn 3.92%, Si 1.02%, Al 0.15%, O 0.016%, N 0.071%, and Fe 93.845%.

[0073] The method for preparing a flux-cored welding wire provided in this embodiment includes the following steps: preparing a low-carbon steel strip and rolling the low-carbon steel strip into a U-shaped strip using a U-shaped die; placing a flux core into the U-shaped steel strip and closing it with a die to form a thick welding wire; passing the thick welding wire prepared in step 2 through a wire drawing die, drawing and reducing the diameter step by step, and finally making the diameter reach 1.2 mm to obtain the final product.

[0074] The self-shielded metal-cored welding wire deposit of this example was prepared using the aforementioned self-shielded metal-cored welding wire. Arc cladding was performed on Q235 mild steel plates, with 6-10 layers, without the need for external shielding gas. The welding process parameters used for multi-layer arc welding were: welding current of 240-280A, welding voltage of 24-28V, and welding speed of 0.25m / min. The weld bead with more than 6 layers was cut using wire cutting to obtain the self-shielded metal-cored welding wire deposit. Porosity sensitivity, strength, and hardness values are shown in Table 1.

[0075] Comparative Example 1

[0076] A low-cost, high-strength, self-protective metal powder core comprises the following components by mass percentage: C 0.155%, B 0.75%, Cr 0.023%, Mn 3.85%, Si 1.15%, Al 0.15%, O 0.008%, N 0.106%, and Fe 93.808%.

[0077] The method for preparing the flux-cored welding wire provided in this comparative example comprises the following steps: preparing a low-carbon steel strip, and rolling the low-carbon steel strip into a U-shaped strip using a U-shaped die; placing the flux core into the U-shaped steel strip, and closing the strip with the die to form a thick welding wire; and passing the thick welding wire prepared in step 2 through a wire drawing die, drawing and reducing the diameter step by step, and finally making the diameter reach 1.2 mm to obtain the final product.

[0078] The self-shielded metal-cored welding wire deposit of this comparative example was prepared using the aforementioned self-shielded metal-cored welding wire. Arc cladding was performed on Q235 mild steel plates, with 6-10 layers, without the need for external shielding gas. The welding process parameters used for the multi-layer arc welding were: welding current of 240-280A, welding voltage of 24-28V, and welding speed of 0.25m / min. The weld bead with more than 6 layers was cut using wire cutting to obtain the self-shielded metal-cored welding wire deposit. Porosity sensitivity, strength, and hardness values are shown in Table 1.

[0079] Comparative Example 2

[0080] A low-cost, high-strength, self-protective metal powder core comprises the following components by mass percentage: C 0.183%, B 0.7%, Cr 0.037%, Mn 4.02%, Si 1.13%, Al 0.23%, O 0.019%, N 0.026%, and Fe 93.655%.

[0081] The method for preparing the flux-cored welding wire provided in this comparative example comprises the following steps: preparing a low-carbon steel strip, and rolling the low-carbon steel strip into a U-shaped strip using a U-shaped die; placing the flux core into the U-shaped steel strip, and closing the strip with the die to form a thick welding wire; and passing the thick welding wire prepared in step 2 through a wire drawing die, drawing and reducing the diameter step by step, and finally making the diameter reach 1.6 mm to obtain the final product.

[0082] The self-shielded metal-cored welding wire deposit of this comparative example was prepared using the aforementioned self-shielded metal-cored welding wire. Arc cladding was performed on Q235 mild steel plates, with 6-10 layers, without the need for external shielding gas. The welding process parameters used for the multi-layer arc welding were: welding current of 240-280A, welding voltage of 24-28V, and welding speed of 0.25m / min. The weld bead with more than 6 layers was cut using wire cutting to obtain the self-shielded metal-cored welding wire deposit. Porosity sensitivity, strength, and hardness values are shown in Table 1.

[0083] Tensile strength test method: First, take a sample on the basis of the metallographic specimen cladding, and take a tensile specimen on the top layer of the deposited metal. Since it is difficult to obtain a standard sample for cladding, a non-standard specimen is used. The specimen length is 52mm, the width is 10mm, the thickness is 3mm, the gauge length is 23.3mm, the center width of the specimen is 5mm, and the cross-sectional area is 15mm. 2 Tensile tests were conducted on a universal electronic testing machine to determine tensile strength and elongation in accordance with GB / T2652-2008, "Tensile Test Methods for Welds and Deposited Metals." The loading speed was 1 mm / s. The maximum tensile force of the universal electronic testing machine is 100 kN.

[0084] Elongation, also known as elongation after fracture, is the percentage between the elongation of the tensile specimen after fracture and the original gauge length. It is a major indicator of material plasticity. Elongation is usually expressed as δ:

[0085]

[0086] Where: L0——original gauge length of the sample;

[0087] L1 - the gauge length of the specimen after fracture.

[0088] Microhardness testing of the deposited metal samples was performed using an automatic Vickers hardness tester, with a test load of 0.5 kgf and a hold time of 15 seconds. To more accurately determine the hardness of the deposited metal, hardness values were measured at 25 points on each surface of the overlay metal, using a 5×5 matrix. The average value was then taken.

[0089] Table 1 Deposited metal properties

[0090]

Claims

1. A metal powder core, characterized in that: The metal powder core comprises the following components by mass percentage: C 0.130% to 0.190%, B 0.69% to 0.76%, Cr 0.015% to 0.038%, Mn 3.80% to 4.05%, Si 1.02% to 1.15%, Al 0.15% to 0.24%, O 0.005% to 0.020%, N 0.032% to 0.085%, and the balance is Fe.

2. Use of the metal powder core according to claim 1 in preparing low-cost, high-strength self-shielded metal powder cored welding wire or its deposited metal.

3. A low-cost, high-strength, self-shielded metal powder cored welding wire, characterized in that: The metal powder cored welding wire comprises the metal powder core according to claim 1.

4. A low-cost, high-strength, self-shielded metal powder cored welding wire deposited metal, characterized in that: The metal powder cored welding wire deposited metal is prepared by using the metal powder core according to claim 1 or the metal powder cored welding wire according to claim 2.

5. The low-cost, high-strength, self-shielded metal powder cored welding wire deposited metal according to claim 4, characterized in that: The matrix structure of the deposited metal is ferrite, with Fe2B and Fe3(C,B) boron-carbon compounds existing at the grain boundaries, and also with dispersed inclusions, the main types of which are AlN, Al2O3, and MnO.

6. The low-cost, high-strength, self-shielded metal powder cored welding wire deposited metal according to claim 4, characterized in that: The deposited metal has a tensile strength of 850-950 MPa, an elongation of 14-18%, and a hardness of HV508-550.

7. The method for preparing a low-cost, high-strength, self-shielded metal powder cored welding wire according to claim 3, characterized in that: The steps include: (1) Prepare a low-carbon steel strip and roll it into a U-shaped strip using a U-shaped die; (2) placing the metal powder core described in claim 1 into a U-shaped steel strip and closing it with a die to form a thick welding wire; (3) The thick welding wire prepared in step (2) is passed through a wire drawing die, and is drawn and reduced in diameter step by step until its diameter reaches one of 1.6 and 1.2 mm, thereby obtaining the final product.

8. The method for preparing the deposited metal of the low-cost, high-strength self-shielded metal cored welding wire according to claim 4, characterized in that: The steps include: (1) Using the self-shielded metal powder cored welding wire according to claim 2, arc surfacing welding is performed on Q235 low carbon steel plate, with the number of surfacing layers being 6-10 layers; (2) The welding process parameters used in multi-layer arc welding are: welding current 240-280 A, welding voltage 24-28 V, and welding speed 0.25 m / min; (3) Use wire cutting to cut more than 6 layers of weld bead, which is the deposited metal of self-shielded metal powder cored wire.

9. Use of the self-shielded metal-cored welding wire according to claim 3 or the deposited metal of the metal-cored welding wire according to claim 4 in mining machinery, petrochemical industry or metallurgical industry.

10. The use according to claim 9, characterized in that The application specifically includes the repair and remanufacturing of equipment wear-resistant parts.

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