Composite ribbon brazing material, method for producing the same, and honing tool

Abstract

The present application relates to the technical field of honing tool, in particular to a composite strip filler metal, a preparation method thereof and a honing tool. The composite strip filler metal comprises a core filler metal strip and a spiral coating layer outside the core filler metal strip. The core filler metal strip is flat, comprising a filler metal skin and a brazing agent encapsulated inside. The spiral coating layer is a flat strip metal layer, spirally distributed on the outer surface of the core filler metal strip and extending from one end to the other end of the core filler metal strip. The present application designs the filler metal into a double-layer composite structure composed of the core filler metal strip and the spiral coating layer, and reasonably designs the composition of each layer, so that the structure can be directly used in resistance brazing process, and at the same time, the welding effect can be improved through the hierarchical melting-in-situ reaction mechanism and high-toughness brazing seam can be generated in-situ, realizing low-temperature connection and ensuring the strength of the brazing seam.

Description

Technical Field

[0001] This invention relates to the field of honing tools, and more specifically, to a composite strip brazing filler metal, its preparation method, and a honing tool. Background Technology

[0002] Honing is a method of finishing workpiece surfaces at low cutting speeds, primarily used for the finishing of holes. It features a large contact area, high cutting efficiency, high machining accuracy, good restoration of geometry, and suitable surface roughness. Diamond and cubic boron nitride honing stones with metal bonds have wear rates only 1 / 150 to 1 / 250 that of ordinary honing stones, effectively improving honing efficiency and surface quality. Metal-bonded honing stones are generally connected to a steel base by brazing. The metal bond in honing stones is often bronze powder, hot-pressed at around 600℃. While conventional silver brazing filler metals have high weld strength, their welding temperature is generally between 620 and 850℃, exceeding the hot-pressing temperature of the honing stone. Welding at this temperature poses a risk of localized melting within the hot-pressed honing stone. Furthermore, honing tools are primarily used for finishing, requiring extremely strict control over post-weld deformation; welding at this temperature can lead to severe deformation of the steel base.

[0003] To reduce brazing temperature, existing technologies use tin-lead brazing filler metals with a brazing temperature of 200-250℃, and cadmium-silver and zinc-aluminum brazing filler metals with a brazing temperature of 400-480℃. However, the tensile strength of the brazing joint of tin-lead filler metals is only 20-40 MPa; while the tensile strength of zinc-cadmium and zinc-aluminum brazing filler metals can be increased to 60-85 MPa, their brazing temperatures are still too high, often resulting in the honing stone falling off during use. Furthermore, these filler metals are mostly in sheet or strip form, requiring the addition of flux during welding, which presents problems such as difficulty in precisely controlling the flux dosage and significant flux residue, and also fails to meet the requirements of automated welding.

[0004] Resistance brazing is a joining method that uses the resistance heat generated by the current passing through the filler metal and the contact surface to melt the filler metal and form a brazed joint. It features concentrated heating, a small heat-affected zone, and low overall temperature rise of the base material. Applying resistance brazing to the connection of honing stones and steel bases could potentially avoid the problems of internal melting of the honing stone and deformation of the base caused by high-temperature brazing. However, traditional strip filler metals require a flux coating during brazing, and conventional fluxes are mostly non-conductive materials. Direct application of these fluxes to resistance brazing can affect the stability of the current path and the uniformity of heating, making them generally unsuitable for direct use in resistance brazing.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a composite strip brazing filler metal, its preparation method, and a honing tool, in order to solve the problems that existing honing tools use brazing filler metals that are difficult to balance low brazing temperature and high weld strength, as well as the problems that adding flux alone leads to excessive flux residue and makes it difficult to achieve resistance brazing and automated welding.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A composite strip-shaped solder includes a flux-cored solder strip and a spiral coating layer located outside the flux-cored solder strip; the flux-cored solder strip is flat and includes a solder metal sheet and flux encapsulated therein; the spiral coating layer is a flat strip-shaped metal layer that is spirally distributed on the outer surface of the flux-cored solder strip and extends from one end of the flux-cored solder strip to the other end; By weight percentage, the solder metal foil comprises 22%~28% Zn, 63%~70% Cd, 6%~10% Ag, 1%~5% Cu, 0.2%~1% Ni, and 0.01%~0.2% Si; the spiral coating comprises 8%~9% Zn, 0.5%~1.0% Ge, 0.1%~0.5% Ni, 0.05%~0.5% Mn, and the balance being tin.

[0008] Preferably, the mass ratio of the brazing filler metal sheet to the spiral coating layer is 10 to 20.

[0009] Preferably, the flux accounts for 8% to 15% of the weight of the flux-cored solder strip.

[0010] Preferably, the ratio of the pitch of the spiral coating layer to the axial width of a single turn of the spiral is ≤2.

[0011] Preferably, the thickness of the composite strip brazing filler metal is 0.15~0.35mm.

[0012] Preferably, the flux is composed of zinc chloride, ammonium chloride, cadmium chloride, and sodium fluoride, and the particle size of the flux is ≤50 mesh.

[0013] The method for preparing the composite strip solder according to any one of the foregoing embodiments includes the following steps: S1. The raw material of the brazing filler metal sheet is melted and cast into an ingot. A hole is drilled in the middle of the ingot along the axial direction. Then, dry flux powder is loaded into the hole of the ingot to form a composite ingot. The flux-cored brazing filler wire is obtained by extrusion and drawing. The raw materials for the spiral coating are melted and cast into ingots, which are then extruded and drawn to obtain alloy wires for winding. S2. The flux-cored solder wire and the winding alloy wire are combined, such that the winding alloy wire is spirally wound around the outer surface of the flux-cored solder wire and extends from one end of the flux-cored solder wire to the other end, to obtain a composite solder wire; S3. The composite brazing wire is rolled into a strip to obtain a composite strip brazing wire.

[0014] Preferably, in step S1, the ratio of the inner diameter of the ingot hole to the diameter of the composite ingot is 0.5 to 0.7.

[0015] Preferably, in step S1, the diameter of the flux-cored solder wire is 2~5mm.

[0016] Preferably, in step S1, the diameter of the alloy wire used for winding is 0.1~1mm.

[0017] A honing tool includes a steel substrate and a honing stone, wherein the steel substrate and the honing stone are brazed together by a composite strip brazing filler metal; The composite strip solder is the composite strip solder as described in any one of the preceding embodiments, or the composite strip solder prepared by any one of the preceding embodiments.

[0018] Preferably, the brazing process for the brazed connection is resistance brazing.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The brazing filler metal of the present invention is a composite strip structure composed of flux-cored brazing filler metal strip and a spiral coating layer on its outside. The spiral coating layer on the surface has a low melting temperature (198~230℃) and melts first in the initial stage of heating. It utilizes its good fluidity to guide the wetting of the surface of the base material to be welded and quickly fill the gap of the brazing joint. When the temperature rises to the melting range of the inner brazing filler metal skin (285~330℃), the brazing filler metal skin melts and releases the flux inside. The molten brazing filler metal skin undergoes an in-situ alloying reaction with the spiral coating layer to form a high-strength and tough brazing joint metal. This achieves both low-temperature connection and ensures the brazing joint strength (≥90MPa). This composite strip brazing filler metal can be directly used in the resistance brazing process and can meet the requirements of automated welding.

[0020] (2) The brazing filler metal provided by the present invention contains trace elements such as Ge and Ni, which can be evenly distributed in the brazing seam to strengthen the matrix and improve the corrosion resistance of the brazing seam. The Si element in the brazing filler metal can improve the fluidity of the molten brazing filler metal while reducing the oxidation of the brazing filler metal, and further improve the welding reliability. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of the composite strip brazing filler metal provided in an embodiment of the present invention; Figure 2 This is a photograph of the composite strip brazing filler metal prepared in Example 1 of the present invention. Figure 3 This is a photograph of flux residue in the brazing seam after brazing the composite strip brazing filler metal in Embodiment 1 of the present invention; Figure 4 This is a photograph of flux residue in the brazing seam after brazing the brazing filler metal sheet in Comparative Example 1 of the present invention; Figure 5 This is a photograph of the solder sheet prepared in Comparative Example 1 of the present invention, showing edge cracking. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0024] like Figure 1 As shown, a first aspect of the present invention provides a composite strip-shaped solder, comprising a flux-cored solder strip 2 and a spiral coating layer 1 located outside the flux-cored solder strip 2; wherein the flux-cored solder strip 2 is flat and includes a solder metal sheet and flux encapsulated therein; the spiral coating layer 1 is a flat strip-shaped metal layer that is spirally distributed on the outer surface of the flux-cored solder strip 2 and extends from one end of the flux-cored solder strip 2 to the other end; By weight percentage, the solder metal foil comprises Zn 22%~28%, Cd 63%~70%, Ag 6%~10%, Cu 1%~5%, Ni 0.2%~1%, and Si 0.01%~0.2%. By weight percentage, the spiral coating comprises 8%~9% Zn, 0.5%~1.0% Ge, 0.1%~0.5% Ni, 0.05%~0.5% Mn, and the balance tin.

[0025] In this invention, the flux-cored solder strip and the spiral coating layer together form a double-layer composite structure, which is generally flat and strip-shaped. The solder metal in the flux-cored solder strip is based on a zinc-cadmium-silver ternary alloy with trace amounts of Cu and Ni added to improve the wettability and bonding strength between the solder and the substrate; simultaneously, trace amounts of Si are added to improve the solder's oxidation resistance and fluidity. The melting temperature range of this solder metal is 285~330℃, lower than existing zinc-cadmium and zinc-aluminum solders. The spiral coating layer is a tin-zinc based solder with a melting temperature range of 198~230℃, located outside the flux-cored solder strip, mainly serving to conduct electricity and induce wetting through low-temperature melting; the added trace elements such as Ge, Ni, and Mn can be evenly distributed in the solder joint, enhancing the structural stability, environmental resistance (oxidation / corrosion resistance), and creep strength of the solder joint under high-temperature service environments.

[0026] The composite brazing strip provided by this invention can be directly used in the resistance brazing process. When the resistance brazing electrode presses the composite strip brazing material and applies welding current, the continuously distributed spiral coating layer on the outside (with tin-based low melting point alloy as the matrix) forms a good conductive path, realizing efficient and uniform current conduction in the weld area, avoiding uneven heating or spatter caused by excessive local contact resistance, and significantly improving process stability and repeatability.

[0027] In this invention, the spiral coating layer covering the surface has a low melting temperature and melts first in the initial stage of resistance brazing heating. Its excellent fluidity allows it to initially wet the surface of the base material being welded, quickly filling the braze gap. As Joule heating continues, the temperature rises to the melting range of the brazing filler metal. The brazing filler metal melts and releases a fixed amount of flux, which undergoes an in-situ alloying reaction with the melted spiral coating layer, forming a high-strength and tough braze metal. This staged melting-in-situ reaction mechanism perfectly matches the rapid heating and short-term holding characteristics of resistance brazing, achieving both low-temperature joining and ensuring braze strength.

[0028] In addition, designing the brazing seam metal into two parts, the brazing metal skin and the spiral coating layer, allows the high-strength and tough composite brazing metal to be generated in situ during brazing, which can also improve the machinability of the strip brazing metal. If the metal skin coating flux is designed directly according to the final brazing seam metal composition, it will not only fail to achieve the effects of graded melting and pilot wetting, but the metal skin composed of this composition is also brittle and has poor machinability.

[0029] The composite strip brazing filler metal of this invention provides a quantitative method for brazing flux, eliminating the need for additional flux coating during brazing, facilitating automated welding, and reducing flux residue in the brazing seam. The composite strip brazing filler metal has a uniform thickness and can be cut to any length, making it compatible with the automatic feeding system of resistance brazing equipment. This enables fully automated welding processes, including automatic fixed-length feeding of the filler metal, automatic electrode clamping, and automatic current output, significantly improving the production efficiency and quality consistency of honing tools.

[0030] In some embodiments, typically but not limitingly, for example, the mass percentage of Zn in the solder foil can be any one of 22%, 24%, 26%, 28%, or a range of any two of those values; the mass percentage of Cd can be any one of 63%, 65%, 68%, 70%, or a range of any two of those values; the mass percentage of Ag can be any one of 6%, 7%, 8%, 9%, 10%, or a range of any two of those values; the mass percentage of Cu can be any one of 1%, 2%, 3%, 4%, 5%, or a range of any two of those values; the mass percentage of Ni can be any one of 0.2%, 0.5%, 0.8%, 1%, or a range of any two of those values; and the mass percentage of Si can be any one of 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, or a range of any two of those values. The mass percentage of Zn in the spiral coating can be any one value or a range of any two values ​​from 8%, 8.2%, 8.5%, 8.8%, and 9%; the mass percentage of Ge can be any one value or a range of any two values ​​from 0.5%, 0.6%, 0.8%, and 1.0%; the mass percentage of Ni can be any one value or a range of any two values ​​from 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%; and the mass percentage of Mn can be any one value or a range of any two values ​​from 0.05%, 0.1%, 0.3%, and 0.5%.

[0031] In some specific embodiments of the present invention, the mass ratio of the brazing filler metal to the spiral coating is 10 to 20. For example, it can be any one of 10, 12, 15, 18, or 20, or a range of any two of these values. If the mass ratio is too large, the outer spiral coating content is too low, making it difficult to provide pilot wetting, and the low content of strengthening elements Ge, nickel, and manganese in the in-situ brazing metal will also affect the joint strength. If the mass ratio is too small, the outer spiral coating content is too high, which will affect the composition of the brazing metal after composite bonding, and the increased tin content will affect the joint strength after brazing.

[0032] In some specific embodiments of the present invention, the flux accounts for 8% to 15% of the weight of the flux-cored solder strip. For example, it can be any one value or a range of any two values ​​from 8%, 10%, 12%, to 15%.

[0033] In some specific embodiments of the present invention, the flux-cored solder strip is a seamless flux-cored solder strip, which can reduce problems such as porosity and splashing that are easily generated after the flux absorbs moisture.

[0034] In some specific embodiments of the present invention, the ratio of the pitch of the spiral coating layer to the axial width of a single spiral turn is ≤2, wherein the axial width of a single spiral turn refers to the straight distance occupied by the single spiral strip along the axis of the composite strip brazing filler metal; that is, adjacent spiral turns in the spiral coating layer can be in a close fit or have a gap; however, the gap cannot be too large. If the ratio of the pitch to the axial width of a single spiral turn is >2, the gap is too large, which may affect the pilot wetting effect in the gap area and may also affect the uniformity of the brazing filler metal.

[0035] In some specific embodiments of the present invention, the thickness of the composite strip brazing filler metal is 0.15~0.35mm. For example, it can be any one value or a range of any two values ​​among 0.15mm, 0.2mm, 0.25mm, 0.3mm, and 0.35mm.

[0036] In some specific embodiments of the present invention, the flux is composed of zinc chloride, ammonium chloride, cadmium chloride, and sodium fluoride; the particle size of the flux is ≤50 mesh.

[0037] In some preferred embodiments of the present invention, the flux comprises, by weight parts, 40-50 parts zinc chloride, 10-15 parts ammonium chloride, 25-30 parts cadmium chloride, and 3-5 parts sodium fluoride. Typically, but not limitingly, for example, the weight parts of zinc chloride in the flux can be any one of 40, 42, 45, 48, or 50 parts, or a range of any two of these values; the weight parts of ammonium chloride can be any one of 10, 12, 14, or 15 parts, or a range of any two of these values; the weight parts of cadmium chloride can be any one of 25, 26, 28, or 30 parts, or a range of any two of these values; and the weight parts of sodium fluoride can be any one of 3, 3.5, 4, 4.5, or 5 parts, or a range of any two of these values.

[0038] A second aspect of the present invention provides a method for preparing the composite strip solder as described in any of the foregoing embodiments, comprising the following steps: S1. Weigh the raw materials according to the composition ratio of the brazing filler metal sheet, melt them and cast them into an ingot. Drill a hole along the axis in the center of the ingot, and then fill the hole with dry flux powder to form a composite ingot. The flux-cored brazing filler wire is obtained by extrusion and drawing. According to the composition ratio of the spiral coating, the raw materials are weighed, melted and cast into ingots, and then extruded and drawn to obtain alloy wire for winding. S2. Combine flux-cored solder wire and winding alloy wire, so that the winding alloy wire is spirally wound on the outer surface of flux-cored solder wire and extends from one end of flux-cored solder wire to the other end to obtain composite solder wire; S3. Roll the composite brazing wire into a strip to obtain a composite strip brazing filler metal.

[0039] The method for preparing the composite strip brazing filler metal of this invention is mature, uses universal equipment, and can be quickly mass-produced industrially, making it highly scalable. If the components of the filler metal sheet and the spiral coating are mixed and melted together, the filler metal becomes brittle, prone to cracking during processing, and has poor machinability. This invention processes the flux-cored filler wire and the winding alloy wire separately before combining them, resulting in good machinability. Furthermore, the melting point of the outer winding alloy wire is lower than that of the inner flux-cored filler wire's metal sheath, allowing the resulting strip brazing filler metal to achieve graded melting and pilot wetting during brazing. Simultaneously, this structure facilitates resistance brazing.

[0040] Furthermore, if the coating layer is wrapped around the outside of the flux-cored brazing wire as a whole sheet, the forming process is relatively difficult. The method of the present invention uses a spiral winding method to combine the winding alloy wire with the outside of the flux-cored brazing wire and then rolls it to form a spiral coating layer, which simplifies the forming process.

[0041] In some specific embodiments of the present invention, in the composite ingot of step S1, the ratio of the inner diameter of the ingot hole to the diameter of the composite ingot is 0.5 to 0.7. For example, it can be any one value or a range of any two values ​​from 0.5, 0.55, 0.6, 0.65, and 0.7. As an example, the diameter of the composite ingot is 50 mm, and the inner diameter of the ingot hole is 25 to 35 mm.

[0042] In some specific embodiments of the present invention, in step S1, the composite ingot is first held at 80~120℃ for 1.5~2h, and then extruded using an extruder. The purpose is to preheat the ingot before extrusion. The holding temperature can be any one value or a range of any two values ​​from 80℃, 90℃, 100℃, 110℃, and 120℃. The holding time can be any one value or a range of any two values ​​from 1.5h, 1.6h, 1.8h, and 2h.

[0043] In some specific embodiments of the present invention, the diameter of the flux-cored solder wire in step S1 is 2~5mm. For example, it can be any one value or a range of any two values ​​among 2mm, 3mm, 4mm, and 5mm.

[0044] Preferably, in step S1, the ingot is first extruded into a wire of 3-3.5mm, and then drawn through multiple passes to finally obtain an alloy wire for winding with a diameter of 0.1~1mm. For example, it can be any one value or a range of any two values ​​among 0.1mm, 0.3mm, 0.5mm, 0.8mm, and 1mm.

[0045] As an example, in step S1, the diameter of the alloy wire used for winding is 1 mm. In step S2, the pitch of the spiral winding of the composite alloy wire is 5-10 mm. For example, it can be any one value or a range of any two values ​​among 5 mm, 6 mm, 8 mm, and 10 mm.

[0046] A third aspect of the present invention provides a honing tool, comprising a steel substrate and a honing stone, wherein the steel substrate and the honing stone are brazed together by a composite strip brazing filler metal; Wherein, the composite strip solder is the composite strip solder as described in any of the preceding embodiments, or the composite strip solder prepared by any of the preceding embodiments.

[0047] In some specific embodiments of the present invention, the brazing process for the brazing connection is resistance brazing. This brazing process has the characteristics of concentrated heating, small heat-affected zone, and low overall temperature rise of the base material. Combined with the composite strip brazing filler metal in this application, it can avoid the problems of internal melting of the whetstone and deformation of the base caused by high-temperature brazing, while also obtaining high brazing seam strength.

[0048] In some specific embodiments of the present invention, the joint strength of the honing tool is ≥90 MPa, and the deformation of the steel substrate is ≤0.10 mm.

[0049] The following detailed description of some embodiments of the present invention is provided in conjunction with specific application examples. Unless otherwise specified, all raw materials used in the embodiments can be obtained commercially available.

[0050] Example 1 The composition of the composite strip solder, including the solder metal skin, spiral coating layer, and flux, is as follows: The solder metal foil composition, by mass percentage, is: Zn 25.9%, Cd 64.8%, Ag 8%, Cu 1%, Ni 0.2%, and Si 0.1%. The composition of the spiral coating layer by mass percentage is: Zn 8.8%, Ge 0.5%, Ni 0.1%, Mn 0.1%, Sn 0.5%; The flux powder, by mass, consists of: 50 parts zinc chloride, 15 parts ammonium chloride, 30 parts cadmium chloride, and 5 parts sodium fluoride, with a particle size of 50 mesh or finer.

[0051] The preparation steps are as follows: S1. Weigh the raw materials according to the composition ratio of the brazing filler metal, melt them using medium-frequency induction heating, and then cast them into ingots with a diameter of 50mm and a height of 100mm. Drill a hole in the center of the ingot with a diameter of 35mm and a depth of 80mm (the hole in the ingot is concentric with the composite ingot). Mix the flux powder evenly in a V-shaped mixing tank, and then dry it in an 80℃ drying oven. Fill the dried flux powder into the hole in the ingot and compact it to form a composite ingot. Place the composite ingot in a 120℃ drying oven and keep it at that temperature for 2 hours. Then, extrude it using an extruder and finally draw it into wire with a diameter of 3mm. Cut off the brazing filler metal wire without flux filling at the ends to obtain a seamless flux-cored brazing filler wire. The flux powder accounts for 15% of the weight percentage of the flux-cored brazing filler wire. The raw materials were weighed according to the composition ratio of the spiral coating layer, melted by medium frequency induction heating, and then cast into an ingot with a diameter of 50mm. The ingot was then directly extruded into a wire with a diameter of 3mm. After multiple drawing passes, an alloy wire with a diameter of 1mm for winding was finally obtained. S2. The flux-cored brazing wire and the winding alloy wire are fed into a composite device for composite bonding. The mass ratio of the brazing metal sheet to the winding alloy wire in the flux-cored brazing wire is 10. The flux-cored brazing wire is in the core, and the winding alloy wire is spirally wound on the surface of the flux-cored brazing wire with a pitch of 8 mm to obtain a composite brazing wire. S3. The composite brazing wire obtained in step S2 is fed into a rolling mill for rolling. After multiple rolling passes, a composite strip brazing wire with a thickness of 0.2 mm is finally obtained. The ratio of the pitch of the spiral coating layer to the axial width of a single turn of the spiral after rolling is approximately 2. A physical image of the composite strip brazing wire is shown below. Figure 2 As shown.

[0052] Comparative Example 1 Raw material A was weighed according to the component ratio of the brazing filler metal sheet in Example 1, and raw material B was weighed according to the component ratio of the spiral coating layer in Example 1. Raw material A and raw material B were mixed at a mass ratio of 10, smelted, and cast into an ingot, which was then rolled into a brazing filler sheet. Figure 5 As shown, the brazing filler metal is brittle and prone to rolling cracks, resulting in poor machinability.

[0053] Comparative Example 2 Comparative Example 2 is similar to Example 1, except that in step S2, the mass ratio of the solder metal sheet to the winding alloy wire in the flux-cored solder wire is 1, and all other conditions are the same as in Example 1.

[0054] Comparative Example 3 Comparative Example 3 is similar to Example 1, except that in step S2, the mass ratio of the solder metal sheet to the winding alloy wire in the flux-cored solder wire is 25, and all other conditions are the same as in Example 1.

[0055] Experimental Example 1 Welding tests were conducted on the composite strip brazing filler metal prepared in Example 1 and the brazing filler metal sheet prepared in Comparative Example 1 (welding diamond honing stone and No. 45 steel). In Comparative Example 1, a resistance wire heating plate was used for welding the brazing filler metal sheet, the heating temperature was controlled at 350°C, and the holding time was 5s. Before welding, flux was applied to the substrate and the brazing filler metal sheet. In Example 1, the welding test of the composite strip brazing filler metal was conducted using resistance brazing, and the welding temperature was also controlled at 350°C with a holding time of 5s.

[0056] According to GB / T 11363-2008, the brazed seam strength of the samples was tested three times, and the results are shown in Table 1. The flux residue in the brazed seam after brazing is as follows: Figure 3 and Figure 4 As shown.

[0057] Table 1

[0058] As shown in Table 1, the composite strip brazing fillet obtained using the method of this invention exhibits higher average brazing strength. Figure 3 and Figure 4 It can be seen that the composite strip brazing filler metal prepared by the method of the present invention significantly reduces the brazing residue (the dark gray in the figure represents flux residue).

[0059] Experimental Example 2 The composite strip brazing filler metal prepared in Example 1 and the brazing filler metal sheet prepared in Comparative Example 1 were used as brazing sheets (the surface of the brazing filler metal sheet in Comparative Example 1 was coated with flux). They were brazed under the same resistance brazing process. The range of heat-affected zone, adhesion to the electrode, spatter, and sensitivity to current during the brazing process were compared. The brazing seam strength after brazing was also tested (3 parallel tests). The results are shown in Table 2.

[0060] Table 2

[0061] As can be seen from the results in Table 2, compared with Example 1, the brazing filler metal sheet in Comparative Example 1 requires flux to be coated on the surface during brazing. During resistance brazing, this affects the stability of the current path and the uniformity of heating. Local overheating leads to a deeper and wider heat-affected zone. Furthermore, local overheating easily causes the electrodes to melt and stick together. Due to the poor current conduction effect, there is severe sparking and spattering during brazing. It is also highly sensitive to current, has a narrow process window, and is difficult to control. The brazed seam strength is low, making it unsuitable for resistance brazing.

[0062] Experimental Example 3 Resistance brazing tests were conducted on the composite strip brazing filler metals prepared in Example 1, Comparative Example 2, and Comparative Example 3, respectively. The resistance brazing conditions were the same as those in Example 1, and the test results are shown in Table 3.

[0063] Table 3

[0064] As shown in Table 3, an excessively large or small mass ratio of brazing filler metal and spiral cladding will cause the final in-situ brazing metal composition to deviate from the optimal composition, resulting in a decrease in brazing strength.

[0065] Test Example 4 Several common traditional brazing filler metals and the composite strip brazing filler metal prepared in Example 1 were used to braze diamond honing oilstones with dimensions of 150mm×4mm×6mm onto 45 steel with dimensions of 150mm×10mm×10mm. For the traditional brazing filler metal, the filler metal sheet was made into a sheet for brazing, and flux was applied to the surface during welding. A resistance wire heating plate was used for welding, and the welding temperature was set to 20°C above the liquidus temperature of the filler metal, with a holding time of 5s. The example used resistance brazing, with a welding temperature of 350°C and a holding time of 5s. Then, the deformation of the steel substrate along a length of 150mm (the change in the length dimension of the steel substrate before and after heating) and the average strength of the welded joint (the average of three sets of data) were measured. The results are shown in Table 4.

[0066] Table 4

[0067] As can be seen from the data in Table 4, the brazing filler metal prepared by the present invention has high joint strength after brazing, a melting temperature lower than that of existing zinc-cadmium and zinc-aluminum brazing filler metals, and a deformation after welding that is close to that of tin-lead brazing filler metals, which is significantly lower than that of zinc-cadmium and zinc-aluminum brazing filler metals, resulting in superior overall performance.

[0068] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A composite strip brazing filler metal, characterized in that, It includes a flux-cored solder strip and a spiral coating layer located outside the flux-cored solder strip; the flux-cored solder strip is flat and includes a solder metal sheet and flux encapsulated inside it; the spiral coating layer is a flat strip-shaped metal layer that is spirally distributed on the outer surface of the flux-cored solder strip and extends from one end of the flux-cored solder strip to the other end; By weight percentage, the solder metal foil comprises 22%~28% Zn, 63%~70% Cd, 6%~10% Ag, 1%~5% Cu, 0.2%~1% Ni, and 0.01%~0.2% Si; the spiral coating comprises 8%~9% Zn, 0.5%~1.0% Ge, 0.1%~0.5% Ni, 0.05%~0.5% Mn, and the balance tin.

2. The composite strip brazing filler metal according to claim 1, characterized in that, The mass ratio of the brazing filler metal sheet to the spiral coating layer is 10~20.

3. The composite strip brazing filler metal according to claim 1, characterized in that, The flux accounts for 8% to 15% of the weight of the flux-cored solder strip.

4. The composite strip brazing filler metal according to claim 1, characterized in that, The ratio of the pitch of the spiral coating layer to the axial width of a single turn of the spiral is ≤2.

5. The composite strip brazing filler metal according to claim 1, characterized in that, The thickness of the composite strip brazing filler metal is 0.15~0.35mm.

6. The composite strip brazing filler metal according to claim 1, characterized in that, The flux is composed of zinc chloride, ammonium chloride, cadmium chloride, and sodium fluoride; the particle size of the flux is ≤50 mesh.

7. The method for preparing the composite strip solder according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. The raw material of the brazing filler metal sheet is melted and cast into an ingot. A hole is drilled in the middle of the ingot along the axial direction. Then, dry flux powder is loaded into the hole of the ingot to form a composite ingot. The flux-cored brazing filler wire is obtained by extrusion and drawing. The raw materials for the spiral coating are melted and cast into ingots, which are then extruded and drawn to obtain alloy wires for winding. S2. The flux-cored solder wire and the winding alloy wire are combined, such that the winding alloy wire is spirally wound around the outer surface of the flux-cored solder wire and extends from one end of the flux-cored solder wire to the other end, to obtain a composite solder wire; S3. The composite brazing wire is rolled into a strip to obtain a composite strip brazing wire.

8. The method for preparing the composite strip solder according to claim 7, characterized in that, In step S1, at least one of the following characteristics is satisfied: (1) In the composite ingot, the ratio of the inner diameter of the ingot hole to the diameter of the composite ingot is 0.5 to 0.7; (2) The diameter of the flux-cored solder wire is 2~5mm; (3) The diameter of the alloy wire used for winding is 0.1~1mm.

9. A honing tool, characterized in that, It includes a steel substrate and a honing stone, wherein the steel substrate and the honing stone are brazed together by a composite strip brazing filler metal; The composite strip brazing filler metal is the composite strip brazing filler metal according to any one of claims 1 to 6, or the composite strip brazing filler metal prepared by the preparation method according to claim 7 or 8.

10. The honing tool according to claim 9, characterized in that, The brazing process for the brazed connection is resistance brazing.

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