An iron-based brazing filler metal for copper / steel dissimilar metal welding and its preparation method

Abstract

A metal-based brazing filler metal for copper / steel dissimilar metal welding and its preparation method are disclosed, belonging to the field of engineering materials. Its chemical composition and weight percentages are: B 2-5 wt%, P 3-6 wt%, Ni 15-28 wt%, Mo 1-5 wt%, Cu 3-6 wt%, Si 2-8 wt%, Cr 10-20 wt%, Mn 3-8 wt%, Sn 4-7 wt%, with the balance being Fe. The brazing filler metal of this invention, when brazed at a temperature of 960±50℃, produces welded joints with good corrosion resistance and a tensile strength greater than 380 MPa. The preparation method of the brazing filler metal of this invention is simple, has a low melting point, and is inexpensive.

Description

Technical Field

[0001] This invention belongs to the field of engineering materials, specifically relating to an iron-based brazing filler metal for copper / steel dissimilar metal welding and its preparation method. Background Technology

[0002] Copper / steel bimetallic composites combine the performance characteristics of both copper and steel. They possess excellent electrical and thermal conductivity, surface reworkability, and aesthetic appeal, while also retaining the high strength and deformation resistance of steel. Furthermore, they save on significant amounts of precious metals, greatly reducing costs. Their superior comprehensive performance is unmatched by any single material. Commonly used brazing filler metals for copper / steel plates include Cu-based, Ni-based, Ag-based, and Au-based filler metals. The appropriate filler metal is typically selected based on the specific application environment.

[0003] However, the high melting point and insufficient heat resistance of Ni-based solders, and the insufficient high-temperature strength of Cu-based solders, have limited their practical applications. Compared to Cu-based, Ni-based, Ag-based, and Au-based solders, Fe-based solders have a significant cost advantage and have been widely used in copper / steel dissimilar metal welding. Summary of the Invention

[0004] The primary objective of this invention is to provide an iron-based brazing filler metal for copper / steel dissimilar metal welding. This iron-based brazing filler metal has good corrosion resistance and a tensile strength of over 380 MPa. It can serve as an intermediate layer in copper / steel joints, improving joint strength and effectively reducing brazing filler metal costs.

[0005] The technical solution to achieve the purpose of this invention is: an iron-based brazing filler metal, the formulation of which includes the following components by weight percentage: B 2-5wt%, P 3-6wt%, Ni 15-28wt%, Mo 1-5wt%, Cu 3-6wt%, Si 2-8wt%, Cr 10-20wt%, Mn 3-8wt%, Sn 4-7wt%, with the balance being Fe.

[0006] The melting temperature of the iron-based brazing filler metal of the present invention is 960±50℃.

[0007] The preparation method of the above-mentioned iron-based brazing filler metal is as follows: Fe, Ni, Mo, Cu, Si, Cr, Mn, Sn metal powder, FeP powder and FeB powder in a certain proportion are mixed evenly in a ball mill, and then flux and binder are added, stirred evenly and left to stand to solidify at room temperature.

[0008] The purity of the raw materials Fe, B, P, Ni, Mo, Cu, Si, Cr, Mn, and Sn in the above-mentioned iron-based brazing filler metals is above 99.95%.

[0009] The ball mill used has a rotation speed between 200 rpm and 300 rpm, a ball milling time of 10 to 16 hours, and a ball-to-material ratio of 3:1.

[0010] The flux used is prepared according to a mass ratio of boric acid: borax = 7:3.

[0011] The adhesive used was prepared according to a mass ratio of ethylene glycol to alcohol of 3:1.

[0012] Further, stir evenly in a glass container, let stand for 2-5 hours, then fill into the weld seam, and cure at room temperature for 5-8 hours.

[0013] Compared with the prior art, the advantages of the present invention are:

[0014] (1) The brazing filler metal obtained using the above-mentioned composition has a low melting point, high strength, and certain corrosion resistance and good toughness. The brazing joint obtained at a brazing temperature of 960±50℃ has good corrosion resistance.

[0015] (2) The brazing filler metal obtained using the above-mentioned components has good wettability and can form an excellent bonding interface with low alloy steel and copper, and the interface is free from welding defects such as cracks and pores.

[0016] (3) The brazing filler metal prepared using the above-mentioned components has a low cost and is particularly suitable for welding dissimilar metals such as low alloy steel and copper.

[0017] (4) P and B are added in the form of FeP and FeB, instead of pure B powder, which greatly reduces the cost. Attached Figure Description

[0018] Figure 1 The effect of applying the iron-based brazing filler metal prepared in Example 1 to the weld seam of low alloy steel Q345 and T2 copper;

[0019] Figure 2 The effect of applying the iron-based brazing filler metal prepared in Example 11 to low-alloy steel Q345 and low-alloy steel Q345 welds;

[0020] Figure 3 SEM scan image of the interface between low alloy steel Q345 and the iron-based brazing filler metal of the present invention. Detailed Implementation

[0021] To further illustrate the present invention, the following detailed description of the formulation materials, preparation methods and applications provided by the present invention is provided in conjunction with the embodiments.

[0022] The brazing filler metal formulation for copper / steel dissimilar metal welding described in this invention comprises: B 2-5wt%, P 3-6wt%, Ni 15-28wt%, Mo 1-5wt%, Cu 3-6wt%, Si 2-8wt%, Cr 10-20wt%, Mn 3-8wt%, Sn 4-7wt%, with the balance being Fe.

[0023] The formulation materials provided in this invention include non-metallic elements Si, B, and P. Si, B, and P can effectively reduce the melting point of the solder and help improve the amorphous alloy forming ability. The content of Si is 2-8 wt%, preferably 3.5-7.6 wt%; the content of B is 2-5 wt%, preferably 2.2-4.75 wt%; and the content of P is 3-6 wt%, preferably 3.5-5.7 wt%.

[0024] The formulation materials provided in this invention include Mo, which can increase the melting point of the alloy matrix, increase the bonding force between atoms, and improve high-temperature strength. In addition, Mo forms a solid solution with the matrix, which has a solid solution strengthening effect, and the formed Mo2C has a dispersion strengthening effect. The Mo content is 1-5 wt%, preferably 1.5-4.5 wt%.

[0025] The formulation provided in this invention includes Ni and Cr. The melting temperature of the solder alloy is reduced through the solid solution of FeCrNi and the eutectic reaction of these elements with intermetallic compounds of Si, P, and B. Cr also provides certain corrosion resistance. The Ni content is 15–28 wt%, preferably 16–26 wt%; the Cr content is 10–20 wt%, preferably 12–17 wt%.

[0026] The formulation provided in this invention includes Cu, which can reduce the diffusion of Si and P into the base material, prevent P precipitation between the grains of the base material, avoid embrittlement of the base material, and improve the corrosion resistance of the brazed joint. The Cu content is 3-6 wt%, preferably 3.73-5.25 wt%.

[0027] The formulation provided in this invention includes Mn and Sn. Mn and Sn can reduce the melting temperature of the solder and improve its wettability; at the same time, Mn can increase the microhardness and high-temperature strength of the solder. The content of Mn is 3-8 wt%, preferably 3.5-7 wt%; the content of Sn is 4-7 wt%, preferably 4.2-6.8 wt%.

[0028] The Fe, FeP, FeB, Ni, Mo, Cu, Si, Cr, Mn, and Sn powders used in this invention all have a purity greater than 99.95%.

[0029] This invention uses Fe, FeP, FeB, Ni, Mo, Cu, Si, Cr, Mn, and Sn raw materials, which are mixed by ball milling, and then flux and binder are added. After curing at room temperature, a new type of low-cost brazing flux is prepared. After welding, the weld has good strength and certain corrosion resistance.

[0030] The brazing flux provided by this invention, prepared from a formula of Fe, B, P, Ni, Mo, Cu, Si, Cr, Mn, and Sn, is initially in paste form and can be molded into any shape after room temperature curing. Its welding interface with steel or copper is smooth and even, with no welding defects such as porosity or cracks. Its tensile strength can reach over 380 MPa. SEM observation of the brazing flux microstructure reveals a uniform structure without obvious coarse grains. Figure 3 ).

[0031] The low-cost preparation method provided by this invention includes: mechanically mixing Fe, FeP, FeB, Ni, Mo, Cu, Si, Cr, Mn, and Sn raw materials in a ball mill; to prevent excessive oxidation of the powder, a certain amount of alcohol can be added for wet milling. Then, the mixed flux and soldering agent are mixed at a mass ratio of 1:2, and a binder is added at a mass ratio of 1:1. The mixture is stirred continuously at room temperature to remove internal air bubbles, then allowed to stand for 2–5 hours. The mixture is then added to a mold or directly filled into the weld seam, and cured for another 5–8 hours to obtain the soldering flux described in this invention.

[0032] During brazing, the obtained flux is placed between copper and steel plates, or the copper and steel plates with the flux are placed in a vacuum resistance furnace, the temperature is raised at 15℃ / min to 30-50℃ above the melting point of the brazing filler metal, and held for 15-30 minutes.

[0033] Example 1

[0034] Metal powders of Fe, Ni, Mo, Cu, Si, Cr, Mn, and Sn with a purity of 99.95% or higher, as well as FeP and FeB powders, were mixed in a ball mill jar at the following ratios: 4.75 wt% B, 4.05 wt% P, 22.35 wt% Ni, 5.83 wt% Si, 3.62 wt% Mo, 4.13 wt% Cu, 13.66 wt% Cr, 3.88 wt% Mn, 4.22 wt% Sn, and 33.51 wt% Fe. 200 ml of alcohol was added, and the mixture was ball-milled for 30 minutes followed by a 10-minute pause at a speed of 300 r / min for 16 hours. The ball-to-material ratio was 3:1. After drying, the powder was removed and placed in a glass beaker. Flux and binder were added in ratios of 1:2 and 1:1 respectively, stirred for 1 minute, and allowed to stand for 3 hours. The mixture was then used to fill the weld seam (Q345 steel for steel, T2 copper for copper) and allowed to stand for 6 hours. To ensure no excess gas remained in the flux, the mixture was stirred at least 5-6 times during the 3-hour standing period, with each stirring lasting at least 1 minute. The flux was prepared according to a boric acid:borax mass ratio of 7:3, and the binder was prepared according to an ethylene glycol:alcohol mass ratio of 3:1.

[0035] like Figure 1 As shown, after the flux has completely cured, it is placed in a vacuum resistance furnace, and the temperature is increased to 980℃ at a rate of 15℃ / min and held for 15min. The strength of the welded joint obtained in the experiment is 380MPa.

[0036] Examples 2-10 were prepared using the preparation method of Example 1. The alloy composition and weld joint strength of each example are shown in Tables 1 and 2.

[0037] Table 1 Alloy composition

[0038]

[0039] Table 2 Strength of Welded Joints

[0040] 1 380 2 389 3 397 4 411 5 418 6 408 7 402 8 392 9 381 10 374

[0041] Example 11

[0042] Metal powders of Fe, Ni, Mo, Cu, Si, Cr, Mn, and Sn with a purity of 99.95% or higher, along with FeP and FeB powders, were mixed in the following proportions: 4.25 wt% B, 4.65 wt% P, 21.35 wt% Ni, 5.63 wt% Si, 3.12 wt% Mo, 4.73 wt% Cu, 13.22 wt% Cr, 3.18 wt% Mn, 4.62 wt% Sn, and 35.25 wt% Fe. The mixture was placed in a ball mill jar, and 200 ml of alcohol was added. The milling process was carried out at a speed of 300 r / min for 16 hours, followed by a 30-minute pause. After drying, the powder was removed and placed in a glass beaker. Flux and binder were added in ratios of 1:2 and 1:1, respectively, and stirred for 1 minute. The mixture was then allowed to stand for 3 hours before being used to fill the weld seam and allowed to stand for 6 hours. To ensure that no excess gas remains in the brazing flux, the flux should be stirred at least 5-6 times during the 3-hour settling period, with each stirring session lasting at least 1 minute. The steel used in the experiment was Q345.

[0043] like Figure 2 As shown, after the flux has completely cured, it is placed in a vacuum resistance furnace, and the temperature is increased to 980℃ at a rate of 15℃ / min and held for 15min. The strength of the welded joint obtained in the experiment is 412MPa.

[0044] Examples 1-11 and above Figure 1-3 The iron-based brazing filler metal provided by this invention has good wettability and is suitable for joining dissimilar metals such as low alloy steel and copper. It is also suitable for joining low alloy steel with low alloy steel, stainless steel with stainless steel, and low alloy steel with stainless steel, forming an excellent bonding interface without welding defects such as cracks or pores.

[0045] This invention is not limited to the above-described embodiments. Other component designs obtained by using the same or similar processes and components as those in the above embodiments of this invention are all within the protection scope of this invention.

Claims

1. A ferro-based brazing filler metal for welding dissimilar metals such as copper and steel, characterized in that, The steel is Q345, and the copper is T2 copper. The Fe, Ni, Mo, Cu, Si, Cr, Mn, Sn metal powders, FeP powder, and FeB powder are mixed evenly using a ball mill according to the following proportions: B 2~5wt%, P 3~4.05wt%, Ni 15~28wt%, Mo 1~5wt%, Cu 3~6wt%, Si 2~6wt%, Cr 10~20wt%, Mn 3~8wt%, Sn 4~7wt%, with the balance being Fe. The mixed powders are then mixed with flux at a mass ratio of 1:2, and a binder is added. The mixture is stirred evenly at room temperature and allowed to stand to solidify at room temperature. The flux is prepared according to a boric acid:borax mass ratio of 7:

3. The binder is prepared according to a ethylene glycol:alcohol mass ratio of 3:

1. The melting point of the iron-based brazing filler metal is 960±50℃.

2. The iron-based brazing filler metal as described in claim 1, characterized in that, The B content is 2.2~4.75wt%; the Ni content is 16~26wt%.

3. The iron-based brazing filler metal as described in claim 1, characterized in that, The Mo content is 1.5~4.5 wt%; the Cu content is 3.73~5.25 wt%; and the Si content is 3.5~6 wt%.

4. The iron-based brazing filler metal as described in claim 1, characterized in that, The Cr content is 12~17wt%; the Mn content is 3.5~7wt%; and the Sn content is 4.2~6.8wt%.

5. The iron-based brazing filler metal as described in claim 1, characterized in that, The ball mill speed is between 200 rpm and 300 rpm, the ball milling time is 10 to 16 hours, and the ball-to-material ratio is 3:

1.

6. The iron-based brazing filler metal as described in claim 1, characterized in that, The Fe, FeP, FeB, Ni, Mo, Cu, Si, Cr, Mn, and Sn powders used all have a purity greater than 99.95%.

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