A non-destructive repair method for broken and damaged bronze artifacts

Abstract

The present invention provides a non-destructive repair method for broken and damaged bronze artifacts, comprising the following steps: first, mixing spray raw materials to obtain spray powder; second, removing oil stains and rust from the surface of the bronze artifact, enlarging the groove of the part to be repaired, filling the bottom of the groove, and covering the part of the bronze substrate near the groove; third, depositing the spray powder in a solid form on the part to be repaired of the bronze artifact under the carrying effect of a preheated high-speed airflow; finally, polishing, coloring, and aging the surface of the repaired area after treatment. The repair method provided by the present invention is simple to operate, has high repair efficiency, has no obvious thermal impact on the bronze artifact substrate, and the chemical composition and organizational structure of the repair layer can be consistent with the raw materials, which is convenient for subsequent aging and other treatments. The method is basically pollution-free to the environment, and the powder splashed by the spraying can be recycled and reused. It is green and environmentally friendly and has broad prospects for promotion and application.

Description

Technical Field

[0001] The invention belongs to the technical field of bronze restoration, and in particular relates to a method for restoring broken and damaged bronze artifacts without causing any damage. Background Art

[0002] my country, one of the four ancient civilizations, boasts a 5,000-year history and culture. Continuous archaeological excavations have unearthed numerous bronze artifacts. These artifacts, a vital part of my country's cultural heritage, are crafted using traditional metal forging techniques. Their primary alloy components are copper, tin, lead, and other metallic elements. Due to years of deep burial in the soil, most unearthed bronze artifacts suffer varying degrees of damage and require restoration to restore them to their original appearance.

[0003] The restoration of bronze artifacts generally includes steps such as cleaning and rust removal, patching, aging, corrosion inhibition, and sealing. Welding and bonding are generally used to patch broken and damaged parts. Welding mainly uses copper welding and tin soldering, which have the disadvantages of large heat-affected zone, low welding strength, and easy cracking during the repair process. Bonding mainly uses adhesive bonding. As time goes by, the adhesive will age and it is inevitable, which will cause aging and cracking at the repaired broken and damaged parts. Therefore, the above two restoration methods will lead to repeated restoration of bronze artifacts, and repeated repairs will cause damage to the artifacts, which may eventually make the bronze artifacts irreparable or even scrapped, lose their cultural information, and cause irreparable cultural losses.

[0004] Currently, methods for repairing broken and damaged bronze artifacts primarily utilize laser welding, laser cladding, and self-propagating welding. For example, the patent titled "A Method for Repairing Broken Bronze Artifacts" (Publication No.: CN1431078A) proposes the use of heat conduction welding and deep penetration welding. By directly irradiating a laser beam onto the fractured portion of the bronze artifact, the laser interacts with the bronze material, welding both ends of the fracture together. The laser-welded bronze artifact is then subjected to grinding, polishing, aging, and coloring, depending on the repair requirements, to achieve the desired restoration. The patent titled "A Method for Repairing Defective Bronze Artifacts" (Publication No.: CN1451510A) utilizes a high-power laser beam directed at the defective portion of the bronze artifact to be repaired, while simultaneously feeding metal powder into the laser molten pool. The laser energy causes the surface of the bronze artifact's metal substrate to melt slightly, melting the bronze powder in the laser molten pool and filling the defective portion. Upon cooling, a coating repair layer is formed. The patent titled "A Method for Repairing Broken and Defective Bronze Artifacts" (publication number: CN105149862) is mainly aimed at repairing broken and defective cultural relics. This invention method obtains high-temperature molten metal with the same composition as the bronze artifact matrix through the exothermic reaction of self-propagating solder powder. The molten metal solidifies into a specific shape in the packaging mold and forms a strong metallurgical bond with the matrix, thereby realizing the repair of broken and defective bronze artifacts.

[0005] Currently, laser welding and laser cladding technologies are used to repair thin-walled artifacts with narrow weld gaps. Completely repairing artifacts with large weld gaps and defects is more difficult. Furthermore, this technology requires the bronze artifacts to be transported to a laboratory and uses expensive laser equipment, resulting in low repair efficiency, poor adaptability, and cumbersome operation. While self-propagating welding technology does not require an external power source or heat source and can directly utilize the exothermic reaction of the material to produce a welding solution for welding repair, the rapid exothermic reaction creates a temperature gradient, which can easily lead to uneven microstructure at the weld, and the welding mold is expensive to manufacture. More importantly, due to the extremely high heat involved in the repair process, the repair materials are all in a molten state, which can thermally affect the bronze artifact matrix, causing irreversible damage to the matrix and the repaired material, such as oxidation, sintering, and phase transformation.

[0006] Based on this, a new restoration method suitable for bronze cultural relics is provided to effectively avoid the irreversible damage such as oxidation, sintering, phase change, etc. caused to the bronze cultural relic matrix by traditional restoration methods. This is of great significance for cultural relic preservation and cultural heritage, and is also a technical problem that researchers urgently need to solve. Summary of the Invention

[0007] The purpose of the present invention is to address the deficiencies of the existing technology and provide a repair method that is simple to operate, has high repair efficiency, has no impact on or damages the broken or damaged bronze artifact matrix, and can be implemented in situ.

[0008] To solve the above technical problems, the present invention adopts the following technical solution: providing a method for repairing broken and damaged bronze artifacts without damage, comprising the following steps:

[0009] S1. Prepare spraying raw materials according to the composition of the bronze artifact to be restored, and mix the spraying raw materials to obtain spraying powder;

[0010] S2. Remove oil and rust from the surface of the bronze artifact, enlarge the groove of the part to be restored, fill the bottom of the groove, and cover the part of the bronze substrate near the groove;

[0011] S3, depositing the spray powder in a solid form on the part of the bronze artifact to be repaired under the action of a preheated high-speed airflow; during the deposition, the air pressure of the airflow is 0.3-0.5 MPa, and the preheating temperature of the airflow is 200-400° C.;

[0012] S4. Polishing, coloring and aging the surface of the repaired area of ​​the bronze artifact processed in step S3 to obtain a repaired bronze artifact.

[0013] In the overall technical solution provided by the present invention, first, the spray powder is configured and the bronze artifact to be repaired is pretreated, wherein the groove is enlarged and the bottom of the groove is filled to facilitate the subsequent deposition of the spray powder in the area to be repaired, and the substrate near the groove is covered to prevent the repair process from damaging other non-defective parts; secondly, a suitable way is found to cover the part to be repaired of the bronze artifact with the spray powder. The inventors fully considered the particularity of the bronze artifact and the requirement for non-destructive repair. After extensive research and exploration, they determined a repair method in which the spray powder is carried by a preheated high-speed airflow and deposited in a solid form on the part to be repaired. The airflow pressure and airflow temperature during the deposition process are controlled so that the gas heating temperature is maintained below the melting point of the spray powder ions. The spray powder particles are always in a solid state during the deposition process, which can greatly avoid the oxidation, phase change, residual stress and grain growth problems of oxidation-sensitive metals (such as Cu, Al, Zn, etc.) in traditional thermal surface engineering technologies; finally, the repair area after spraying is post-treated to complete the non-destructive repair of the bronze artifact.

[0014] Furthermore, in step S1, the bronze artifact to be repaired includes a broken and / or damaged bronze artifact. The spraying raw materials are configured according to the composition of the bronze artifact to be repaired, so that the composition of the spraying powder is as close as possible to that of the bronze artifact. This ensures consistency between the weld performance and the parent material properties, and prevents corrosion and fracture in the repaired area.

[0015] Furthermore, in step S1, the spraying raw materials include, by mass percentage, 80-95 wt.% Cu powder, 2-15 wt.% Sn powder, 1-3 wt.% Pb powder, 0.5-3.5 wt.% low-carbon ferromanganese FeMn powder, and 0.5-2 wt.% S70 cast steel powder. The above-mentioned spraying raw materials are mixed in a mechanical mixer to obtain the spraying powder. In the present invention, adding 0.5-3.5 wt.% low-carbon ferromanganese FeMn powder to the spraying raw materials can ensure the strength and corrosion resistance of the repair layer, and adding 0.5-2 wt.% S70 cast steel powder can exert the shot peening effect, facilitate improving deposition efficiency, and increase the bonding strength between interfaces.

[0016] Furthermore, in the spraying raw materials, Cu powder, Sn powder, Pb powder, low carbon ferromanganese FeMn powder and S70 cast steel powder are all spherical and have a purity of 99.9%.

[0017] Furthermore, in the spraying raw material, the particle size of the S70 cast steel powder is 120-250 μm, and the particle size of the other powders is 15-25 μm. Preferably, in the spraying raw material, the particle size of the S70 cast steel powder is 180 μm, and the particle size of the other powders is 20 μm.

[0018] Furthermore, in step S2, sandblasting is used to remove oil and rust from the surface of the bronze artifact. The sandblasting pressure is 0.4-0.6 MPa, the sandblasting time is 5-20 seconds, and the sand shot size is 50-200 mesh. This setting is mainly due to the fact that the bronze alloy is relatively soft, and the sandblasting pressure should not be too high or the time should not be too long, otherwise it will easily damage the substrate to be repaired.

[0019] Furthermore, in the step S2, the groove shape of the groove treatment is selected from one of a V-shaped groove and an X-shaped groove, and the groove treatment can be performed by mechanical equipment such as a grinding wheel. Generally speaking, the groove shape can be V-shaped, X-shaped, I-shaped, Y-shaped, single U-shaped or double U-shaped. In the present invention, a V-shaped groove is used for repairing damaged bronzes, and an X-shaped groove is used for repairing broken bronzes. Different groove shapes are used for different types of damage, which can minimize the damage to the bronzes during the repair process, and also facilitate the deposition process of the spray powder in the area to be repaired in the later stage. During the deposition process, the more vertical the angle between the spray gun and the side wall of the groove, the better the effect, while the I-shaped groove causes greater damage to the bronzes, the lower part of the Y-shaped groove cannot be repaired, and the angle between the side wall of the single U-shaped or double U-shaped groove and the spray gun cannot be guaranteed. In the present invention, after many tests, it was determined that the bottom angle of the V-shaped and X-shaped grooves is preferably 30 to 60 degrees. If it is too small, the angle between the side wall of the groove and the spray gun is difficult to ensure. If it is too large, the damage to the bronze ware is greater, the repair volume is large, and the repair time is prolonged.

[0020] Furthermore, in step S2, the filling treatment method includes: filling the bottom of the groove with cement slurry. In the present invention, the use of cement slurry has the following advantages: (1) facilitating the repair operation; (2) saving precious metal powder repair materials; and (3) subsequent spraying powder can be directly deposited on the cement, forming an interface with sufficient bonding strength, which is not possible with conventional welding or laser repair technologies.

[0021] Preferably, in step S2, the upper surface of the bottom of the groove after being filled with cement slurry is 2 to 8 mm away from the surface of the bronze object.

[0022] Furthermore, in step S2, the masking method includes brushing a mixture of silicone oil and graphite powder onto the bronze substrate near the groove. Preferably, the mass ratio of silicone oil to graphite powder in the mixture is 1:1. The masking mixture protects the bronze substrate during deposition and automatically falls off after the spray powder is deposited.

[0023] Furthermore, the deposition process in step S3 involves the following key equipment: a spray gun, a powder feeder, a gas heating device, a high-pressure gas source, and other auxiliary equipment. During the deposition process, the spray powder is first fed into the spray gun via the powder feeder. The heated high-pressure gas carries the spray powder ions through the Laval tube, accelerating the spray powder particles from composonic to supersonic speeds during this process, thereby forming a two-phase flow of gas-powder particle mixing. Accelerated by the preheated high-speed gas flow, the spray powder particles impact the workpiece surface at supersonic speeds and in a completely solid state. During this impact, both the particles and the substrate surface undergo intense plastic deformation, bonding together to form a coating. To further minimize damage to the bronze artifact substrate during the spray powder deposition process and improve the coating's bonding properties, the present invention optimizes the parameters of the above-mentioned deposition process, preferably using argon as the working gas, with a gas pressure of 0.3-0.5 MPa, a gas preheating temperature of 200-400°C, a controlled distance between the cold nozzle and the substrate of 8-10 mm, and a travel speed of 4-6 mm / s.

[0024] Furthermore, in the repair method provided by the present invention, the filling depth of the cement slurry in step S2 and the deposition thickness of the spraying powder in step S3 are adjusted according to the surface thickness of the fracture and damage of the bronze artifact.

[0025] In existing repair technologies, laser welding has a maximum weld thickness of 10mm due to heat limitations, while laser cladding has a maximum thickness of only 3-5mm. Exceeding this thickness easily leads to secondary cracking. The repair method provided by the present invention deposits the spray powder in a solid form on the area to be repaired, enabling the repair of fractures or damaged areas with a thickness of 20-30mm. The repair process has no significant thermal impact on the repaired substrate, thus avoiding irreversible damage to the bronze artifact substrate, such as oxidation, sintering, and phase transformation.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention provides a non-destructive repair method for broken and damaged bronze artifacts, which utilizes high-temperature and high-pressure gas to carry spray powder and deposits the spray powder in a solid form on the part to be repaired. The repair area formed has the advantages of dense tissue and high bonding strength. In particular, the repair method effectively avoids the problems of oxidation-sensitive metals (such as Cu, Al, Zn, etc.) in traditional thermal surface engineering technology, such as oxidation, component burning, phase change, residual stress, and grain growth, and has no obvious thermal impact on the repair substrate, ensuring that the bronze substrate is not damaged during the repair process.

[0028] (2) The present invention provides a method for repairing damaged, broken, and non-destructive bronze artifacts. The cast steel powder added to the spray powder can play a shot peening role, thereby improving deposition efficiency and enhancing interface bonding. During the spraying process, the undamaged areas on the bronze artifact surface are covered to prevent damage to other undefective areas during the repair process. The chemical composition and microstructure of the repair layer on the bronze artifact repaired by the repair method provided by the present invention can be consistent with the original material, facilitating subsequent treatments such as aging.

[0029] (3) The present invention provides a method for repairing broken and damaged bronze artifacts without damage. The operation is simple and safe. Museum staff can master it with a little training. No special requirements such as welder certificates are required. The repair process does not require the preparation of various molds, etc., and the repair efficiency is high. The repair method can be performed in situ, and there is no need to transport the bronze artifacts that are inconvenient to move to a fixed workshop location for repair. In addition, the repair method has basically no pollution to the environment, and the powder splashed by the spraying can be recycled and reused. As a green and environmentally friendly repair method, it has broad prospects for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic flow chart of a method for repairing broken and damaged bronze artifacts without causing damage provided by the present invention;

[0031] Figure 2 This is a schematic structural diagram of the V-shaped groove used in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0034] The present invention will be further described below with reference to specific examples, but they are not intended to limit the present invention.

[0035] The main parameters involved in the repair methods used in Examples 1-3 are shown in Table 1 below.

[0036] Table 1

[0037]

[0038] Example 1

[0039] The bronze artifact to be restored is a complex-shaped knife handle with local surface defects but no breakage.

[0040] Step 1: Prepare spraying raw materials (85 wt.% of Cu powder, 10 wt.% of Sn powder, 2 wt.% of Pb powder, 2 wt.% of low-carbon ferromanganese FeMn powder, and 1 wt.% of S70 cast steel powder) according to the composition of the bronze artifact to be restored, and mix them in a mechanical mixer to obtain spraying powder;

[0041] Step 2: Pre-treat the area of ​​the bronze artifact to be repaired, remove surface oil and rust, and perform shot blasting. The parameters for the shot blasting are: 0.5 MPa sandblasting pressure, 10 s sandblasting time, and 100 mesh sandblasting. Enlarge the groove of the part of the bronze artifact to be repaired (using a V-shaped groove with a bottom angle of 45 degrees), fill the bottom of the groove with cement slurry, and the upper surface after filling is 6 mm away from the surface of the bronze artifact; apply a mixture of silicone oil and graphite powder in a mass ratio of 1:1 to the part of the bronze substrate near the groove to cover the part of the bronze substrate near the groove;

[0042] Step 3: Fix the bronze artifact to be repaired on a fixture, load the spray powder into a powder feeder, and allow the spray powder to be deposited in a solid form on the part to be repaired of the bronze artifact under the carrying action of a preheated high-speed airflow; during the deposition, an argon airflow is used, the air pressure of the airflow is 0.4 MPa, and the preheating temperature of the airflow is 300°C; the distance between the nozzle and the substrate to be repaired is 9 mm, and the moving speed is 5 mm / s.

[0043] Step 4: Post-process the bronze artifact processed in step 3 by polishing, coloring and aging the surface of the repaired area to obtain the repaired bronze artifact.

[0044] After repair in this embodiment, the damaged parts of the bronze cultural relics are effectively filled, and there are no defects such as pores and cracks in the filled parts, and the repair effect is good.

[0045] Example 2

[0046] The bronze artifact to be restored is a round coin with a break in the middle.

[0047] Step 1: Prepare spraying raw materials (93 wt.% of Cu powder, 2 wt.% of Sn powder, 1 wt.% of Pb powder, 3.5 wt.% of low-carbon ferromanganese FeMn powder, and 0.5 wt.% of S70 cast steel powder) according to the composition of the bronze artifact to be restored, and mix them in a mechanical mixer to obtain spraying powder;

[0048] Step 2: Pre-treat the area of ​​the bronze artifact to be repaired, remove surface oil and rust, and perform shot blasting. The parameters for the shot blasting are: blasting pressure 0.4MPa, blasting time 20s, and sand shot size 100. Enlarge the groove of the part of the bronze artifact to be repaired (using a V-shaped groove with a bottom angle of 60 degrees), fill the bottom of the groove with cement slurry, and the upper surface after filling is 4mm away from the surface of the bronze artifact; apply a mixture of silicone oil and graphite powder in a mass ratio of 1:1 to the part of the bronze substrate near the groove to cover the part of the bronze substrate near the groove;

[0049] Step 3: Fix the bronze artifact to be repaired on a fixture, load the spray powder into a powder feeder, and allow the spray powder to be deposited in a solid form on the part to be repaired of the bronze artifact under the carrying action of a preheated high-speed airflow; during the deposition, an argon airflow is used, the air pressure of the airflow is 0.5 MPa, and the preheating temperature of the airflow is 300°C; the distance between the nozzle and the substrate to be repaired is 10 mm, and the moving speed is 6 mm / s.

[0050] Step 4: Post-process the bronze artifact processed in step 3 by polishing, coloring and aging the surface of the repaired area to obtain the repaired bronze artifact.

[0051] After repair in this embodiment, the damaged parts of the bronze cultural relics are effectively filled, and there are no defects such as pores and cracks in the filled parts, and the repair effect is good.

[0052] Example 3

[0053] The bronze artifact to be restored is a complex-shaped vessel with a partially cracked bottom.

[0054] Step 1: Prepare spraying raw materials (90 wt.% of Cu powder, 5 wt.% of Sn powder, 3 wt.% of Pb powder, 0.5 wt.% of low-carbon ferromanganese FeMn powder, and 1.5 wt.% of S70 cast steel powder) according to the composition of the bronze artifact to be restored, and mix them in a mechanical mixer to obtain spraying powder;

[0055] Step 2: Pre-treat the area of ​​the bronze artifact to be repaired, remove surface oil and rust, and perform shot blasting. The parameters for the shot blasting are: 0.6MPa sandblasting pressure, 5s sandblasting time, and 100-mesh sandblasting. Enlarge the groove of the part of the bronze artifact to be repaired (using an X-shaped groove with a bottom angle of 30 degrees), fill the bottom of the groove with cement slurry, and the upper surface after filling is 8mm away from the surface of the bronze artifact; apply a mixture of silicone oil and graphite powder in a mass ratio of 1:1 to the part of the bronze substrate near the groove to cover the part of the bronze substrate near the groove;

[0056] Step 3: Fix the bronze artifact to be repaired on a fixture, load the spray powder into a powder feeder, and allow the spray powder to be deposited in a solid form on the part to be repaired of the bronze artifact under the carrying action of a preheated high-speed airflow; during the deposition, an argon airflow is used, the air pressure of the airflow is 0.3 MPa, and the preheating temperature of the airflow is 400°C; the distance between the nozzle and the substrate to be repaired is 8 mm, and the moving speed is 4 mm / s.

[0057] Step 4: Post-process the bronze artifact processed in step 3 by polishing, coloring and aging the surface of the repaired area to obtain the repaired bronze artifact.

[0058] After repair in this embodiment, the damaged parts of the bronze cultural relics are effectively filled, and there are no defects such as pores and cracks in the filled parts, and the repair effect is good.

[0059] The above are only preferred embodiments of the present invention and do not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the present invention specification should be included in the protection scope of the present invention.

Claims

1. A method for repairing broken or damaged bronze artifacts without causing damage, comprising the following steps: S1. Prepare spraying raw materials according to the composition of the bronze artifact to be restored, and mix the spraying raw materials to obtain spraying powder; the spraying raw materials include, by mass percentage, 80 wt.% to 95 wt.% of Cu powder, 2 wt.% to 15 wt.% of Sn powder, 1 wt.% to 3 wt.% of Pb powder, 0.5 wt.% to 3.5 wt.% of low-carbon ferromanganese FeMn powder, and 0.5 wt.% to 2 wt.% of S70 cast steel powder; the particle size of the S70 cast steel powder is 120 to 250 μm, and the particle size of the other powders is 15 to 25 μm; S2. Remove oil and rust from the surface of the bronze artifact, enlarge the groove of the part to be restored, and fill the bottom of the groove; apply a mixture of silicone oil and graphite powder to the part of the bronze substrate near the groove, and cover the part of the bronze substrate near the groove; S3, depositing the spray powder in a solid form on the part of the bronze artifact to be repaired under the action of a preheated high-speed airflow; during the deposition, the air pressure of the airflow is 0.3-0.5 MPa, and the preheating temperature of the airflow is 200-400° C.; S4. Polishing, coloring and aging the surface of the repaired area of ​​the bronze artifact processed in step S3 to obtain a repaired bronze artifact.

2. The repair method according to claim 1, characterized in that: In step S1, the bronze artifacts to be repaired include broken and / or damaged bronze artifacts.

3. The repair method according to claim 1, characterized in that: Among the spraying raw materials, various powders are spherical and have a purity of 99.9%.

4. The repair method according to claim 1, wherein: In step S2, sandblasting is used to remove oil stains and rust on the surface of the bronze artifact. The sandblasting pressure is 0.4-0.6 MPa, the sandblasting time is 5-20 seconds, and the sand shot mesh size is 50-200 mesh.

5. The repair method according to claim 1, characterized in that: In step S2, the groove shape of the groove processing is selected from one of a V-shaped groove and an X-shaped groove.

6. The repair method according to claim 1, characterized in that: In step S2, the filling treatment method includes: filling the bottom of the groove with cement slurry.

7. The repair method according to claim 1, characterized in that: In the step S3, during the deposition, the gas flow is argon gas flow, the distance between the nozzle and the substrate is 8-10 mm, and the moving speed is 4-6 mm / s.

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