CN115595573B - 6000-Series aluminum alloy repairing material for local dry underwater laser repairing and repairing method - Google Patents

Abstract

The present invention discloses a repair material and a repair method for local dry underwater laser repair of 6000 series aluminum alloys. The repair material includes the following components by mass percentage: Mg: 4-10%, Si: 1-2%, Zr: 0.8-1.5%, Sc: 0.2-0.7%, the total amount of impurities does not exceed 0.1%, and the balance is Al. The repair material provided by the present invention has good formability and good comprehensive mechanical properties when used in laser additive manufacturing. The local dry underwater laser repair method for 6000 series aluminum alloys can not only be used for on-site repair of metal parts in underwater environments, but also solve the performance softening problem existing in the laser repair process of heat-treatable aluminum alloys.

Description

A repair material and repair method for local dry underwater laser repair of 6000 series aluminum alloy

Technical Field

The present invention belongs to the technical field of laser repair materials, and in particular relates to a repair material and a repair method for local dry underwater laser repair of 6000 series aluminum alloy.

Background Art

6000 series aluminum alloys mainly use Mg and Si as the main alloying elements to form Mg ₂ Si strengthening phase. They are heat-treatable aluminum alloys with excellent formability, good welding performance and strong corrosion resistance. They are widely used in aircraft, ships, high-speed trains and deep-sea equipment structures. However, due to the harsh service environment, aluminum alloy structural parts are easily damaged. Laser additive manufacturing technology (this patent specifically refers to laser directed energy deposition) is considered to be a potential disruptive technology. It uses a high-energy laser beam to quickly melt the cladding material, and the molten metal powder quickly solidifies and forms a metallurgical bond with the parent material. While having the characteristics of heat concentration and low heat input, it also has the advantages of high efficiency and good mechanical properties. It has been widely used in the repair of amorphous alloys, refractory alloys, iron-based alloys, nickel-based high-temperature alloys and titanium alloys. However, Al-Si series aluminum alloys are currently the only aluminum alloys suitable for laser additive manufacturing, but their mechanical properties are difficult to match the properties of 6000 series aluminum alloy parent materials.

When deep-sea equipment such as deep-sea oil and gas pipelines, deep-sea robots, and submersibles are damaged, underwater in-situ repair becomes the most meaningful and challenging technology. At the same time, laser repair of 6000 aluminum alloy also faces another important challenge. 6000 series aluminum alloy is a heat-treatable aging-strengthening aluminum alloy with a single strengthening phase and high thermal sensitivity. After being subjected to thermal cycles during the laser cladding process, the heat-affected zone of the 6000 aluminum alloy parent material is large, and the strength decreases significantly, which seriously damages the comprehensive mechanical properties of 6000 series aluminum alloy structural parts.

Summary of the invention

The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

In view of the above problems and/or the problems existing in the prior art, the present invention is proposed.

One of the purposes of the present invention is to provide a repair material for local dry underwater laser repair of 6000 series aluminum alloy, so as to solve the problems of poor formability of aluminum alloy manufactured by laser additive manufacturing and softening of heat affected zone of 6000 series aluminum alloy after laser repair.

To solve the above technical problems, the present invention provides the following technical solutions: a repair material for local dry underwater laser repair of 6000 series aluminum alloy, comprising the following components by mass percentage: Mg: 4-10%, Si: 1-2%, Zr: 0.8-1.5%, Sc: 0.2-0.7%, the total amount of impurities does not exceed 0.1%, and the balance is Al.

As a preferred solution of the present invention for local dry underwater laser repair of 6000 series aluminum alloy repair material, wherein: the mass ratio of the Zr to the Sc is Zr/Sc≥2.

As a preferred solution of the present invention for local dry underwater laser repair of 6000 series aluminum alloy repair material, wherein: the mass relationship between the Mg, the Zr and the Sc is Mg/(Zr+Sc)≥4.

As the preferred solution for the local dry underwater laser repair of 6000 series aluminum alloys described in the present invention, various factors are taken into consideration, such as solid solution strengthening, stacking fault strengthening, fine grain strengthening, nano-precipitation strengthening, defect suppression, and stable laser processing molten pool. The specific alloy design is based on the following:

The role of Mg element: First, under the rapid solidification preparation conditions of 3D printing, it forms a supersaturated solid solution, which plays a role in solid solution strengthening. Second, it reduces the stacking fault energy of aluminum alloys and forms a long-range ordered phase, which plays a role in stacking fault strengthening. Third, it inhibits the discontinuous precipitation of Al ₃ (Sc, Zr) particles and maintains the coherence of Al ₃ (Sc, Zr) particles and aluminum matrix.

The role of Si element: First, it forms Mg2Si strengthening phase, which plays a role of dispersion strengthening. Second, it reduces the alloy solidification temperature range and cracking sensitivity while reducing the viscosity of the alloy melt and the tendency of pore formation. Third, aluminum alloy materials have good thermal conductivity. The stirring process in the molten pool during laser processing is intense. Under the ultra-fast cooling rate in the water environment, the aluminum alloy molten pool is easy to cool in the churning, thus forming a large number of pores. By adding an appropriate amount of Si, the molten pool can be stabilized and the forming quality of aluminum alloy during laser repair can be improved.

The role of Sc and Zr elements: forming Al ₃ (Sc, Zr) particles with strong thermal stability, playing a role of dispersion strengthening, while refining the grains, blocking the growth of columnar crystals, and inhibiting the generation of cracks.

As a preferred solution of the present invention for local dry underwater laser repair of 6000 series aluminum alloy repair materials, the following components are included in mass percentage: Mg: 6.8%, Si: 1.2%, Zr: 1.1%, Sc: 0.3%, the total amount of impurities does not exceed 0.1%, and the balance is Al.

As a preferred solution of the present invention for local dry underwater laser repair of 6000 series aluminum alloy repair materials, the following components are included in mass percentage: Mg: 7.5%, Si: 1.5%, Zr: 1.0%, Sc: 0.35%, the total amount of impurities does not exceed 0.1%, and the balance is Al.

Another object of the present invention is to provide a local dry underwater laser repair method for 6000 series aluminum alloy, comprising:

Pre-alloyed powder of the repair material configured according to the mass percentage of claim 1;

Cut the damaged part of the parent material into regular shapes;

Use high-pressure gas to drain moisture from the area to be repaired;

Repair was performed using a laser cladding system.

As a preferred solution of the local dry underwater laser repair method of 6000 series aluminum alloy of the present invention, it also includes grinding and cleaning the cut part to remove surface oxides.

As a preferred solution of the local dry underwater laser repair method of 6000 series aluminum alloy of the present invention, the laser cladding system is used for repair, the laser power is 1400-1800W, the scanning speed is 400-800mm/min, the interlayer thickness is 0.5mm, and the overlap rate is 60-80%.

As a preferred solution of the local dry underwater laser repair method of 6000 series aluminum alloy of the present invention, the pre-alloyed powder of the repair material is prepared by weighing each intermediate alloy metal block according to the element ratio of claim 1 and powdering by vacuum gas atomization.

As a preferred solution of the local dry underwater laser repair method of 6000 series aluminum alloy of the present invention, the repaired part has fine and uniform structure in the repaired area, no cracks, high density, tensile strength of more than 100% of the parent material, and elongation of more than 15%.

Compared with the prior art, the present invention has the following beneficial effects:

The 6000 series aluminum alloy powder formula for laser repair provided by the present invention overcomes the defects of traditional grades such as easy cracking, poor mechanical properties, and large anisotropy during 3D printing. The obtained repaired parts have fine and uniform structure, are dense and defect-free, and have excellent comprehensive mechanical properties.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

FIG1 is a schematic diagram of a local dry underwater laser repair method for 6000 series aluminum alloy;

FIG2 is a metallographic image of Example 1 of local dry underwater laser repair of 6000 series aluminum alloy;

FIG3 is a diagram showing the hardness evolution of the transition zone of Example 1 of the local dry underwater laser repair of 6000 series aluminum alloy;

FIG4 is a metallographic image of comparative example 2 of local dry underwater laser repair of 6000 series aluminum alloy;

Figure 5 shows the hardness evolution of the transition zone of the 6000 series aluminum alloy control example 4 repaired by local dry underwater laser.

DETAILED DESCRIPTION

In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

Example 1

The composition of the repair material for local dry underwater laser repair of 6000 series aluminum alloy in Example 1 is prepared as follows, in percentage by mass: Mg: 6.8%, Si: 1.2%, Zr: 1.1%, Sc: 0.3%, the total amount of impurities does not exceed 0.1%, and the balance is Al.

As shown in FIG1 , it is a schematic diagram of the repair of this embodiment. The entire repair process is performed using LMD8060 laser cladding equipment. The specific repair steps are as follows:

(1) Weigh pure Al, Al-Mg, Al-Si, Al-Sc, and Al-Zr metal blocks according to the above mass element ratios and prepare powders by vacuum gas atomization;

(2) According to the area and depth of the damaged part of the structural part of the parent material (6061-T6 material), the damaged part is cut into a through groove with the following regular shape: the cross section of the barrel groove is an inverted isosceles trapezoid with an upper base of 1 mm, a lower base of 9 mm, a height of 4 mm, and a waist inclination angle of 45°;

(3) Grinding the cut part with an angle grinder and cleaning it with a surfactant to remove surface oxides;

(4) The base material is placed in a water-cooled box assembled in the forming chamber of the LMD8060 laser cladding equipment, and the water in the area to be repaired is drained by using high-pressure and high-purity argon gas through an air curtain nozzle to form a local dry cavity in an underwater environment;

(5) LMD8060 laser cladding equipment was used for repair, and circulating cooling water was introduced into the water cooling box for water cooling; the laser parameters for underwater laser repair of 6000 series aluminum alloy were: laser power 1800W, scanning speed 800mm/min, interlayer thickness 0.5mm, and overlap rate 65%.

After corrosion, the metallographic structure of the cladding area and the transition area of the parent material of the repaired part is shown in Figure 2. There are no cracks in the cladding area, but there are a few pores, and the density reaches 99.4%. The tensile strength of the repaired part is 302MPa, and the elongation at break is 15.4%; the tensile strength of the parent material is 290MPa, and the tensile strength of the repaired part can reach 104% of the parent material.

The hardness evolution of the transition zone was measured using a microhardness tester with a loading force of 100 g and a loading time of 15 s. As shown in Figure 3, the heat-affected zone did not soften.

Example 2

The composition of the repair material for local dry underwater laser repair of 6000 series aluminum alloy of Example 2 is prepared as follows, in percentage by mass: Mg: 7.5%, Si: 1.5%, Zr: 1.0%, Sc: 0.35%, the total amount of impurities does not exceed 0.1%, and the balance is Al.

The repair method is the same as that in Example 1.

By observing the metallographic diagram, it was found that there were no cracks in the cladding area, but there were a few pores, and the density reached 99.6%. The tensile strength of the repaired part was 298MPa, and the elongation at break was 15.2%; the tensile strength of the parent material was 290MPa, and the tensile strength of the repaired part could reach 103% of the parent material. The hardness evolution of the transition area was measured, and it was found that the heat-affected zone was not softened.

Example 3

The composition of the repair material for local dry underwater laser repair of 6000 series aluminum alloy of Example 3 is prepared as follows, in percentage by mass: Mg: 4.5%, Si: 1.0%, Zr: 1.2%, Sc: 0.2%, the total amount of impurities does not exceed 0.1%, and the balance is Al.

The repair method is the same as that in Example 1.

By observing the metallographic diagram, it was found that there were no cracks in the cladding area, but there were a few pores, and the density reached 99.0%. The tensile strength of the repaired part was 291MPa, and the elongation at break was 15.0%; the tensile strength of the parent material was 290MPa, and the tensile strength of the repaired part could reach 100% of the parent material. The hardness evolution of the transition area was measured, and it was found that the heat-affected zone was not softened.

Example 4

The composition of the repair material for local dry underwater laser repair of 6000 series aluminum alloy of Example 4 is prepared as follows, in percentage by mass: Mg: 10%, Si: 1.0%, Zr: 1.2%, Sc: 0.2%, the total amount of impurities does not exceed 0.1%, and the balance is Al.

The repair method is the same as that in Example 1.

By observing the metallographic diagram, it was found that there were no cracks in the cladding area, but there were a few pores and the density was 88.0%. The tensile strength of the repaired part was 290MPa and the elongation at break was 15.0%; the tensile strength of the parent material was 290MPa, and the tensile strength of the repaired part could reach 100% of that of the parent material. The hardness evolution of the transition area was measured and it was found that the heat affected zone was not softened.

Comparative Example 1

The Mg content in Example 1 was adjusted to 2%, and the other conditions were the same as in Example 1. By observing the metallographic diagram, it was found that there were no cracks in the cladding area, there was a certain amount of pores, the density was 98.2%, the tensile strength of the repaired part was 263MPa, which was lower than the tensile strength of the parent material of 290MPa, and the elongation at break was 9.8%. The hardness evolution of the transition area was measured, and it was found that the heat-affected zone was not softened.

Comparative Example 2

The Zr content in Example 1 was adjusted to 3%, and the other conditions were the same as in Example 1. By observing the metallographic diagram, it was found that the cladding area had no cracks, a large number of pores, and a density of 96.4%. The metallographic structure of the cladding area is shown in Figure 4. The tensile strength of the repaired part is 235MPa, which is lower than the tensile strength of the parent material of 290MPa, and the elongation at break is 7.2%. The hardness evolution of the transition area was measured, and it was found that the heat-affected zone was not softened.

Comparative Example 3

The Si content in Example 1 was adjusted to 0%, and the other conditions were the same as in Example 1. By observing the metallographic diagram, it was found that there were no cracks in the cladding area, there was a certain amount of pores, the density was 97.8%, the tensile strength of the repaired part was 251MPa, which was lower than the tensile strength of the parent material of 290MPa, and the elongation at break was 8.2%. The hardness evolution of the transition area was measured, and it was found that the heat-affected zone was not softened.

Comparative Example 4

The local dry underwater repair process in Example 1 is changed to protective atmosphere air cooling repair, and the steps are as follows:

(1) Weighing each master alloy metal block according to a certain mass element ratio and preparing powder by vacuum gas atomization;

(2) According to the area and depth of the damaged part of the parent material structure, the damaged part is cut into a through groove with the following regular shape: the cross section of the barrel groove is an inverted isosceles trapezoid with an upper base of 1 mm, a lower base of 9 mm, a height of 4 mm, and a waist inclination angle of 45°;

(3) Grinding the cut part with an angle grinder and cleaning it with a surfactant to remove surface oxides;

(4) The base material is placed in a water-cooled box assembled in the forming chamber of the LMD8060 laser cladding equipment, the water in the water-cooled box is drained, and a protective atmosphere is formed on the surface of the damaged part of the base material structure using high-pressure and high-purity argon gas through an air curtain nozzle;

(5) LMD8060 laser cladding equipment was used for repair, and the repaired structural parts were allowed to cool naturally. The other conditions were the same as those in Example 1.

By observing the metallographic image, it was found that there were no cracks in the cladding area, but there were a few pores, the density was 99.2%, the tensile strength of the repaired part was 205MPa, which was lower than the tensile strength of the parent material of 290MPa, and the elongation at break was 7.2%. The hardness evolution of the transition area was measured, as shown in Figure 5, and the heat-affected zone was softened in a large range.

Comparative Example 5

The laser parameters of the local dry underwater repair process in Example 1 were changed to: laser power 1000 W, scanning speed 1000 mm/min, and the other conditions were the same as in Example 1. By observing the metallographic phase diagram, it was found that there were a large number of unfused defects in the transition zone and the cladding zone, the interface bonding was poor, the tensile strength of the repaired part was 175 MPa, and the elongation at break was 3.2%.

The present invention utilizes the extremely rapid non-equilibrium solidification characteristics of 3D printing to create new materials and develops a repair material for laser repair of 6000 series aluminum alloys. The present invention utilizes the rapid solidification effect of 3D printing and high Mg content to obtain a supersaturated solid solution Al-Mg alloy, while the high Mg content reduces the stacking fault energy of the aluminum alloy, obtains a long-range ordered phase to further strengthen the aluminum alloy and inhibit the formation of cracks; the added Si element reduces the viscosity of the melt, helps the nucleated pores to escape quickly, and forms a Mg ₂ Si strengthening phase with Mg; in addition, the formed nano Al ₃ (Sc, Zr) realizes the transformation from columnar crystal to equiaxed crystal, further inhibiting the formation of cracks.

The mass fraction of Mg in the alloy is 4-10%, and its purpose is to improve the solid solution strengthening effect; the second is to reduce the stacking fault energy of Al alloy and form a long-range ordered phase. The mass fraction of Si in the alloy is 1-2%, and its purpose is to form a eutectic strengthening phase with Mg, reduce the alloy solidification temperature range and cracking sensitivity, and reduce the viscosity and pore formation tendency of the alloy melt. The mass fraction of Zr in the alloy is 0.8-1.5%, and the mass fraction of Sc is 0.2-0.7%, and its purpose is to form Al ₃ (Sc, Zr) phase, which has the effect of dispersion strengthening and grain refinement, and at the same time realizes the transformation from columnar crystal to equiaxed crystal and inhibits crack formation. The quantitative relationship between Zr and Sc is Zr/Sc≥2, and its purpose is to make the formed Al ₃ (Sc, Zr) particles have strong thermal stability and inhibit the coarsening of the structure of the formed part during internal heat treatment. The quantitative relationship among Mg, Zr and Sc is Mg/(Zr+Sc)≥4, and its purpose is to prevent the discontinuous precipitation of Al ₃ (Sc, Zr) phase and maintain the coherence between Al ₃ (Sc, Zr) phase and α-Al matrix.

The local dry underwater laser repair method for 6000 series aluminum alloy proposed in the present invention not only solves the difficult problem of deep-sea in-situ repair of damaged aluminum alloy, but also improves the heat diffusion efficiency, reduces the thermal effect of laser energy on the 6000 aluminum alloy base material, and inhibits the formation of heat-affected zone.

It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims (7)

1. A repairing method for repairing 6000-series aluminum alloy by using local dry underwater laser is characterized by comprising the following steps of: comprising the steps of (a) a step of,

Preparing prealloyed powder of the repair material;

cutting the damaged part of the parent material into a regular shape;

Water in the area to be repaired is discharged by high-pressure gas;

Repairing by adopting a laser cladding system;

Wherein the prealloyed powder comprises the following components in percentage by mass: mg: 4-10%, si: 1-2%, zr:0.8 to 1.5 percent of Sc:0.2 to 0.7 percent, the total impurity amount is not more than 0.1 percent, and the balance is Al; repairing by adopting a laser cladding system, wherein the laser power is 1800W, the scanning speed is 800mm/min, the interlayer thickness is 0.5mm, and the lap joint rate is 65%; the repairing piece has the advantages of small and uniform repairing area, no cracks, high density, high tensile strength reaching more than 100% of the base material and high elongation reaching more than 15%.

2. The repair method for repairing 6000-series aluminum alloy by using local dry underwater laser according to claim 1, which is characterized by comprising the following steps: the mass ratio of Zr to Sc in the prealloyed powder is Zr/Sc is more than or equal to 2.

3. A repair method for repairing 6000-series aluminum alloy by using local dry underwater laser according to claim 1 or 2, which is characterized in that: the mass relation of Mg, zr and Sc of the prealloyed powder is Mg/(Zr+Sc) is more than or equal to 4.

4. A repair method for repairing 6000-series aluminum alloy by local dry underwater laser according to claim 3, which is characterized in that: the prealloyed powder comprises the following components in percentage by mass: mg:6.8%, si:1.2%, zr:1.1%, sc:0.3%, the total amount of impurities is not more than 0.1%, and the balance is Al.

5. A repair method for repairing 6000-series aluminum alloy by local dry underwater laser according to claim 3, which is characterized in that: the prealloyed powder comprises the following components in percentage by mass: mg:7.5%, si:1.5%, zr:1.0%, sc:0.35%, the total amount of impurities is not more than 0.1%, and the balance is Al.

6. The repair method for repairing 6000-series aluminum alloy by using local dry underwater laser according to claim 1, which is characterized by comprising the following steps: also included is polishing and cleaning the cut site to remove surface oxides.

7. The repair method for repairing 6000-series aluminum alloy by using local dry underwater laser according to claim 1, which is characterized by comprising the following steps: the prealloy powder for preparing the repairing material is prepared by weighing each intermediate alloy metal block according to the element ratio of claim 1 and pulverizing by adopting a vacuum gas atomization mode.