CN108161276A - High entropy flux-cored wire for magnesium-steel MIG welding and preparation method thereof - Google Patents

Abstract

The invention discloses a high-entropy flux-cored welding wire for magnesium-steel MIG welding. The powder is prepared by the following components according to atomic percentage, and the total percentage is 100%, wherein Fe is 5-15%, and Mg is 10%- 20%, Cr is 20%~45%, Ni is 21%~39%, Cu is 5%~13%. The sheath material is industrial high-purity copper strip. The preparation steps include: 1. melting and blending the master alloy; 2. applying the vacuum air atomization powder making technology to prepare atomized powder; Using the high-entropy flux-cored welding wire of the present invention to carry out magnesium-steel MIG welding, a high-quality magnesium-steel welded joint is obtained, and the chemical composition of the weld metal is within the principal element range of the high-entropy alloy, realizing the high-entropy weld seam change. The weld has excellent strength and toughness, effectively eliminates the brittle intermetallic compound phase, and has good comprehensive mechanical properties.

Description

High-entropy flux-cored wire for magnesium-steel MIG welding and preparation method thereof

technical field

The invention belongs to the field of welding technology, in particular to a high-entropy flux-cored welding wire for magnesium-steel MIG welding and a preparation method thereof.

Background technique

In recent years, due to the increasingly serious energy and environmental problems, there are urgent requirements for product lightweight in the manufacturing industries of aircraft, automobiles, trains, ships, etc., as well as in the fields of energy, aerospace, and national defense. Magnesium and magnesium alloys play an important role in the process of product lightweight due to their excellent properties of low density and high specific strength. The weight of magnesium-steel composite parts is equivalent to 50~60% of steel, and at the same time it has other excellent characteristics of magnesium and steel. It can improve material utilization, reduce structural weight, improve corrosion resistance of parts, and reduce costs. On the one hand, it has obvious social effects and economic benefits, and has good application and development prospects. However, the replacement of steel parts with magnesium and steel composite parts also imposes strict requirements on the welding of magnesium-steel dissimilar materials.

At present, the main methods for welding magnesium-steel dissimilar materials are resistance welding, brazing and fusion welding. Resistance welding can better control the thickness of the brittle layer between the two materials, and is a good welding method for magnesium-steel dissimilar materials. However, resistance welding has special requirements on the shape and thickness of materials, and the processing efficiency is low, so it cannot be widely used in industrial production; brazing is easy to form weld defects, welding quality is not high, and its wide application is also limited; while fusion welding Not only can realize the high-efficiency connection of magnesium-steel dissimilar materials, but also has the characteristics of high processing efficiency and flexible process. In particular, MIG welding is the most representative. MIG welding can be semi-automatic or fully automatic welding. It has a wide range of applications and has outstanding advantages: 1. Good welding quality: stable welding process, small deformation, and good cathode crushing effect. 2 High welding productivity: large current density welding can be used, the base metal penetration is large, the welding wire melting speed is fast, and the degree of automation is high. 3 Good protection effect: due to the use of inert gas as the shielding gas, it does not react with the metal in the molten pool, effectively avoiding the occurrence of weld defects. However, MIG welding also inevitably has a brittle intermetallic compound layer, which leads to poor joint performance and limits the widespread use of MIG welding.

Contents of the invention

The present invention organically combines flux-cored welding wire technology and high-entropy alloy technology to obtain a high-entropy flux-cored welding wire. The purpose is to solve the problem of brittle intermetallic compounds that are easily formed when MIG welding wire is directly welded to magnesium-steel in the prior art. This leads to the problem that the strength of the welded joint is reduced. Using the high-entropy flux-cored welding wire of the present invention to carry out magnesium-steel MIG welding, the chemical composition of the weld metal is in the range of the principal element of the high-entropy alloy, and the structure at the weld tends to be single bcc or fcc, realizing the welding The high entropy of the joint is easy to obtain high-quality magnesium-steel welded joints.

The present invention is realized by adopting the following technical solutions:

A high-entropy flux-cored wire for magnesium-steel MIG welding, including a powder and a sheath.

The powder is prepared according to the atomic percentage of the following components, the total atomic percentage is 100%, of which Fe 5~15%, Mg10%~20%, Cr 20%~45%, Ni 21%~39%, Cu 5%~13 %;

The sheath material is industrial high-purity copper strip.

The preparation method of the above-mentioned high-entropy flux-cored welding wire for magnesium-steel MIG welding comprises the following steps:

Step 1. Configure master alloy

Composition by atomic percentage, the total atomic percentage is 100%, of which Fe is 5~15%, Mg is 10%~20%, Cr is 20%~45%, Ni is 21%~39%, Cu is 5%~ 13%;

Convert the above-mentioned atomic percentages into mass percentages, and weigh various high-purity metals according to the mass percentages; mix the above-mentioned weighed metal materials in a ball mill, and compact them into billets; put the prepared billets in a vacuum electric arc furnace Melting in the medium to make a master alloy;

Step 2. Apply vacuum air atomization powder making technology to prepare high-entropy atomized powder, and the particle size of the powder is controlled at 80-100 mesh;

Step 3, using flux-cored welding wire forming machine equipment to prepare high-entropy flux-cored welding wire.

In the medicated powder configuration process of the present invention, the composition and content limitation reason of each chemical element are respectively described as follows:

In order to improve the comprehensive mechanical properties of the welded joint between magnesium metal and steel, it is necessary to keep the chemical composition of the weld metal within the range of the principal element forming the high-entropy alloy. According to the composition characteristics of Mg and Fe of the base metal to be welded, the five principal element high-entropy alloy of Mg-Cr-Fe-Ni-Cu is selected as the welding wire. The main reasons are as follows:

1. During the welding process, the melting of the base metal and the dissolution of the base metal into the molten pool near the seam are inevitable. In order to prevent the formation of brittle intermetallic compounds at the weld, the target composition of the weld must contain Mg and Fe principal components, and Mg must be present in the welding seam. The solubility in the welding seam is strong, so the content of these two elements in the welding wire is lower than that of other principal elements. In addition, due to the use of high-purity copper strips and the better solubility of copper in the welding seam, the welding wire Cu Content should also be kept at a low level.

2. Cr has good compatibility with metals Fe and Mg, which can effectively avoid the generation of brittle intermetallic compounds.

3. By adding Ni element into the intermediate layer alloy, it can not only have unlimited solid solution with Fe, but also can dissolve with Mg, Cr, etc. The addition of Ni can improve the compatibility between the weld and the base metal, and inhibit the intermetallic compound. produce. When the high-entropy flux-cored welding wire is used for welding, the weld metal is still a high-entropy alloy, which realizes the high-entropy of the weld, effectively eliminates brittle intermetallic compounds, and has high weld joint strength.

The beneficial effect of the present invention is that the present invention innovatively combines the flux-cored welding wire technology and the high-entropy alloy technology to obtain a high-entropy flux-cored welding wire, and uses the high-entropy flux-cored welding wire of the present invention to carry out magnesium-steel MIG welding , to obtain high-quality magnesium-steel welded joints, the chemical composition of the weld metal is within the range of the principal element of the high-entropy alloy, and the structure of the weld tends to be single bcc or fcc, realizing the high-entropy of the weld . The weld has excellent strength and toughness, effectively eliminates the brittle intermetallic compound phase, and has good comprehensive mechanical properties.

The invention has reasonable design, the high-entropy flux-cored welding wire is easy to process and form, and the cost is low. The operation process of the high-entropy flux-cored welding wire is simple, convenient, efficient, good in adaptability, easy to popularize, and has good market application value.

Description of drawings

Fig. 1 shows the schematic diagram of MIG welding of Q235b/AZ91D magnesium alloy by using the high-entropy alloy welding wire prepared by the present invention.

In the figure: 1-high-entropy flux-cored welding wire, 2-high-entropy atomized powder, 3-high-entropy weld seam.

Detailed ways

Specific embodiments of the present invention will be described in detail below.

A high-entropy flux-cored wire for magnesium-steel MIG welding, including a powder and a sheath.

The powder is prepared according to the atomic percentage of the following components, the total atomic percentage is 100%, of which Fe 5~15%, Mg10%~20%, Cr 20%~45%, Ni 21%~39%, Cu 5%~13 %;

The sheath material is industrial high-purity copper strip (99.99%) with a width of 10±0.1mm and a thickness of 0.5±0.03mm.

The preparation method of the above-mentioned high-entropy flux-cored welding wire is implemented according to the following steps:

Step 1. Melting master alloy

Composition by atomic percentage (see Table 1), the total atomic percentage is 100%. Convert the atomic percentage into mass percentage, and weigh various high-purity metals (99.99%) according to the mass percentage; mix the above metal materials in a ball mill (five kilograms of powder, the ball milling time is about 15 minutes), and compact them into blanks to be Use; the billet made is melted in a vacuum electric arc furnace to make a master alloy.

Step 2. Using the vacuum air atomization powder making technology, the master alloy is melted and refined in the induction furnace, and the molten metal liquid is poured into the heat preservation crucible, and enters the guide tube and the nozzle. The stream is atomized. The atomized metal powder falls into the powder collecting tank. The atomized metal powder is screened according to the particle size of the powder. The particle size of the powder is controlled at 80-100 mesh, and the preferred particle size range is 85-95 mesh.

Step 3: Using the equipment of the flux-cored welding wire forming unit, high-entropy flux-cored welding wires with diameters of φ1.4mm, φ1.6mm, φ2.4mm and φ3.2mm are prepared.

When welding, it is necessary to adjust the melting amount of the base metal and adjust the dry extension length of the welding wire to control the melting speed of the welding wire and control the weld composition within the effective composition range of the high-entropy alloy. Through the above steps 1, 2, and 3, four different specifications of the high-entropy flux-cored welding wire were prepared, and the specific powder formulations are shown in Table 1.

Table 1. Specific powder formulations of four high-entropy flux-cored wires with different specifications (atomic percentage\at%)

Utilize four high-entropy flux-cored wires of different specifications obtained in the present invention to weld the Q235b/AZ91D magnesium alloy, and refer to Table 2 for the contents of each principal component of the final alloy in the weld seam obtained after welding.

Table 2. The content of each principal component of the weld metal finally obtained by implementing four types of welding wires with different diameters (atomic percentage\at%)

As shown in Figure 1, the welding wire with a specification of φ2.4mm is used for welding, and the high-entropy alloy welding wire of φ2.4mm is obtained according to the component content in the above table 1, and Q235b/AZ91D is MIG welded, and the welding current is limited to 170A-230A , the welding speed is 15min/cm, the preheating temperature is kept at room temperature, and the final high-entropy alloy weld composition with the implementation specification of φ2.4 type in the above table 2 is obtained, there is no crack in the weld transition zone, and the resistance of Q235b/AZ91D welding joint The tensile strength reaches 462±2MPa, and the impact energy reaches 35±2J.

It can be seen from the implementation results of the high-entropy flux-cored welding wire of the above example that the high-entropy flux-cored welding wire of the present invention is used to carry out magnesium-steel MIG welding, and a high-quality magnesium-steel welded joint is obtained, and the chemical composition of the weld metal is in the high-entropy alloy Within the range of the pivot element, the high entropy of the weld is realized. The weld has excellent strength and toughness, effectively eliminates the brittle intermetallic compound phase, and has good comprehensive mechanical properties.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit them. Although detailed descriptions have been made with reference to the embodiments of the present invention, those of ordinary skill in the art should understand that the technical solutions of the present invention are modified Or equivalent replacements do not deviate from the spirit and scope of the technical solutions of the present invention, and all of them should be included in the protection scope of the claims of the present invention.

Claims (4)

1. a kind of high entropy flux-cored wire for magnesium-steel MIG welding, including medicinal powder and crust, it is characterised in that：Medicinal powder by with Lower component is prepared by atomic percent, and total atomic percent is 100%, wherein Fe 5 ~ 15%, and Mg 10% ~ 20%, Cr 20% ~ 45%, Ni 21% ~ 39%, Cu 5% ~ 13%；

Skin material uses industrial high purity copper band.

2. a kind of preparation method of high entropy flux-cored wire for magnesium-steel MIG welding, it is characterised in that：Include the following steps：

Step 1: configuration master alloy

Formed by atomic percent, total atomic percent is 100%, wherein Fe be 5 ~ 15%, Mg be 10% ~ 20%, Cr be 20% ~ 45%, Ni are that 21% ~ 39%, Cu is 5% ~ 13%；

Above-mentioned atomic percent is converted into mass percent, various high pure metals have been weighed according to mass percent；It will be upper Load weighted metal material mixing in the ball mill is stated, is compacted into blank；Manufactured blank is melted in vacuum arc furnace ignition Match, master alloy is made；

Step 2: using vacuum gas-atomized powder technology, high entropy atomized powder is prepared, powder particle size is controlled in 80 ~ 100 mesh；

Step 3: using flux-cored wire forming machine group equipment, it is prepared into high entropy flux-cored wire.

3. the preparation method of the high entropy flux-cored wire according to claim 2 for magnesium-steel MIG welding, it is characterised in that： In step 2, powder particle size ranging from 85 ~ 95 mesh.

4. the preparation method of the high entropy flux-cored wire according to claim 2 for magnesium-steel MIG welding, it is characterised in that： The high entropy flux-cored wire of following four kinds of different sizes is prepared, specific medicinal powder formula is as follows：

（1）, welding wire φ 1.4, medicinal powder formula：Fe 10.6%、Mg 15.1%、Cr 30.0%、Ni 33.2%、Cu 11.1%；

（2）, welding wire φ 1.6, medicinal powder formula：Fe 11.4%、Mg 14.3%、Cr 34.6%、Ni 30.5%、Cu 9.2%；

（3）, welding wire φ 2.4, medicinal powder formula：Fe 8.2%、Mg 16.8%、Cr 32.1%、Ni 34.6%、Cu 8.3%；

（4）, welding wire φ 3.2, medicinal powder formula：Fe 5.0%、Mg 18.6%、Cr 31.0%、Ni 38.2%、Cu 7.2%.