Tin plating method for drawing bronze surface ornamentation

Abstract

The invention discloses a tin plating method capable of being used for drawing patterns on the surface of bronze, and relates to the technical field of bronze casting processes. Organic acid, tin oxide and tin powder are mixed and then react to prepare the tin paste. And a writing brush is used for dipping the tin paste to draw the patterns on the surface of the bronze ware, and the tin paste is converted into the tin-rich patterns on the surface of bronze by adopting a secondary heating method. The tin paste adopted by the invention can be easily dipped, tin-rich ornamentation can be formed on the surface of the bronze ware through a drawing and heating method, and the thickness of the tin-rich ornamentation is 15-25 microns. According to the tin-rich ornamentation, the abrasive resistance can be improved on the basis that the attractiveness of the ornamentation is guaranteed, meanwhile, the tin paste contains organic acid tin which is high in viscosity and insoluble in water, the organic acid tin cannot be removed only through polishing, and therefore the corrosion resistance of the ornamentation can be improved due to the existence of the organic acid tin in the tin paste.

Description

Technical Field

[0001] The invention relates to the technical field of bronze casting technology, in particular to a tinning method for drawing bronze surface patterns. Background Art

[0002] Some of the bronze weapons unearthed in China have a tin-rich pattern. Some of the patterns on the weapons are black, and some are silver. There are many ways of tin plating in ancient times, including simple immersion or rubbing tin plating, tin ore (SnO2) reduction or cementation tin plating, electrochemical tin plating, electrolytic tin plating, and tin amalgam tin plating. The black tin-rich pattern on the surface of bronze weapons is formed by the paste tin plating method. This tin plating method can form a layer of fine δ phase about 20μm thick on the bronze surface. The specific composition of δ phase is an intermetallic compound Cu 31 Sn8.

[0003] The modern tin-plating processes for preparing tin-rich patterns mainly include: hot-dip tinning process, electroplating tinning process and chemical tinning process. Among them, the electroplating tinning process uses electrochemical reaction to reduce tin ions to the surface of bronze to form a tin layer. Although this method can achieve a thinner tin-plating layer, the electroplating process is more complicated and requires precise control of parameters such as current. The chemical tinning process uses chemical reactions to deposit a tin layer on the surface of bronze without the need for an external current. This method has the advantages of uniform coating and low cost, but the bonding strength and corrosion resistance of the coating are poor; while the hot-dip tinning process is to heat the tin liquid and apply it to the surface of the bronze to form a tin-plating layer. Although the thickness of the tin-plating layer obtained by this method is uniform, the composition of the plating solution during the hot-dip tinning process affects the wear resistance of the tin-plating layer.

[0004] In the prior art, "Research on the Technology of Diamond Patterns on Bronze Weapons of the Eastern Zhou Dynasty" (Tan Derui et al., Journal of Archaeology, No. 1, Jan, 2000) discloses the heating diffusion process of the metal paste coating and the metal paste ratio. Among them, the metal paste is made by grinding a high-tin alloy (60% Sn, 40% Cu) into powder and mixing it with a resin, which is applied to the bronze surface and heated and polished to obtain a silver pattern. The above-mentioned paste has the defects of being difficult to prepare, requiring harsh conditions such as heating temperature and time, and being difficult to control. In addition, the metal paste has a low boiling point and high viscosity, and it is impossible to directly draw patterns on the surface of the bronze sword. It is necessary to first evenly apply the metal paste on the object, and then carve the patterns on the paste until the matrix leaks out. The processing process is relatively complicated, and the hardness of the patterns made by the above-mentioned metal paste is not ideal, and hardness is an important criterion for measuring wear resistance. It can be seen that the wear resistance of the patterns made by the above-mentioned solder paste needs to be improved.

[0005] Therefore, it is very important to develop a simpler and easier method for tin plating bronze surface patterns, which can not only ensure the formation of nano-scale patterns on the bronze surface, but also ensure the wear resistance and corrosion resistance of the patterns. Summary of the invention

[0006] In view of the above-mentioned prior art, the purpose of the present invention is to provide a tin-plating method for drawing bronze surface decorations. The present invention adopts a mixture of organic acid, tin oxide and tin powder to prepare a tin paste, and uses a brush to dip the tin paste to draw the bronze surface decorations, and uses a secondary heating method to convert the tin paste into a tin-rich decoration on the bronze surface. The tin paste used in the present invention can be easily dipped and applied, and it can form tin-rich decorations on the surface of the bronze, and the thickness of the tin-rich decorations is 15-25μm. This tin-rich decoration can ensure the wear resistance on the basis of ensuring the aesthetics of the decoration. At the same time, the above-mentioned tin paste contains organic acid tin, and the organic acid salt has a high viscosity and is insoluble in water. It cannot be removed by grinding alone, which can improve the corrosion resistance of the decoration.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] The present invention provides a tinning method for drawing bronze surface patterns, comprising the following steps:

[0009] (1) mixing liquid organic acid, tin oxide and tin powder to obtain solder paste;

[0010] (2) After the solder paste is heated to a molten state, the molten solder paste is used to draw patterns on the bronze ware, and then the bronze ware with the drawn patterns is heated. After the heating is completed, the bronze ware is taken out and post-processed to form tin-rich patterns on the surface of the bronze ware, thus forming tin-rich patterns.

[0011] Preferably, in step (1), the organic acid is one or more of rosin, stearic acid or palmitic acid.

[0012] Preferably, in step (1), the liquid organic acid is obtained by heating the organic acid to 65-120°C.

[0013] Preferably, in step (1), the mass ratio of liquid organic acid, tin oxide and tin powder is (1-1.5):(0.5-1):1.

[0014] Preferably, in step (2), the heating temperature is 150-220° C., and the heating time is ≥15 min.

[0015] Preferably, in step (2), the heating temperature of the bronze ware with the pattern drawn is 430-450° C., and the heating time is 1-2 h.

[0016] Preferably, in step (2), the post-treatment is grinding or polishing.

[0017] Further preferably, the polishing treatment is: after taking out the bronze ware, cooling it to room temperature, polishing its surface with 2500-grit sandpaper to remove the black oxide on the surface, and the bronze surface can present a silvery white tin-rich texture.

[0018] Further preferably, the polishing treatment is: after taking out the bronze ware, cool it to room temperature, and use a flannel cloth dipped in metallographic polishing paste and an appropriate amount of clean water to wipe its surface for polishing treatment. The black oxide layer on the surface of the bronze decoration will be retained, and a black tin-rich texture will be presented.

[0019] Further preferably, the main component of the metallographic polishing paste is 0.25 μm corundum.

[0020] Preferably, in step (2), the thickness of the tin-rich pattern is 15-25 μm.

[0021] Beneficial effects of the present invention:

[0022] The present invention mixes an organic acid with tin oxide and tin powder and heats them to a liquid state to obtain a solder paste. The solder paste is heated to a molten state, and a brush or other tool can be used to dip the molten solder paste and draw patterns on a bronze ware. After heating, the metal tin in the solder paste sinks into the bronze matrix due to the Kendall effect, and a micron-thick tin-rich decoration can be formed on the bronze ware. The thickness of the tin-rich decoration is 15-25 μm and is flush with the bronze surface. On the basis of ensuring the aesthetics of the decoration, the wear resistance is improved. At the same time, the organic acid salt in the solder paste has a high viscosity, is insoluble in water, and cannot be removed by grinding alone, which can improve the corrosion resistance of the decoration.

[0023] Specifically, the present invention uses a solder paste obtained by mixing organic acid, tin oxide and tin powder, wherein the organic acid in the solder paste has a low melting and boiling point and poor thermal stability, and is easily vaporized and boiled when the temperature rises. After adding tin oxide, the tin oxide reacts with part of the organic acid to obtain organic acid tin, which can improve its thermal stability. The solder paste is heated to a molten state, so that the metal tin particles can be evenly distributed in the organic acid salt, which is easier to form a δ phase to ensure the hardness of the pattern, thereby ensuring its wear resistance. At the same time, the heating temperature of 430-450°C is not enough to completely vaporize and evaporate the organic acid tin in the paste, and some of it must remain on the metal surface or enter the tin-rich pattern, which can ensure the corrosion resistance of bronze. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 : Scanning electron microscope backscattering imaging of the upper surface of the solder paste prepared in Example 1;

[0025] Figure 2 : Ultra-depth-of-field microscopic imaging of the tin-rich patterns on the bronze surface obtained in Example 1;

[0026] Figure 3 : Metallographic microscopic images of the edge of the tin-rich decoration of the bronze cross section obtained in Example 1, wherein (a) is a metallographic microscopic image of the cross section of the left edge of the tin-rich decoration, and (b) is a metallographic microscopic image of the cross section of the right edge of the tin-rich decoration;

[0027] Figure 4 : Scanning electron microscope backscattered imaging of the edge of the tin-rich decoration on the bronze surface obtained in Example 1. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0029] In the prior art, a mixture of copper-tin alloy and resin is used as a paste for tin plating on the surface of bronze ware. The preparation of the paste is complex and has a low boiling point and high viscosity. It is not possible to directly decorate the surface of the bronze ware. It is necessary to first evenly apply the metal paste on the object and then carve patterns on the paste until the patterns leak out of the substrate. The processing process is relatively complicated.

[0030] The present invention provides a tin-plating method for directly drawing patterns on the surface of bronze. The present invention adopts a method of mixing organic acid, tin oxide and tin powder to prepare a tin paste, drawing the tin paste on the surface of bronze, and converting the tin paste into a tin-rich pattern on the surface of bronze by a secondary heating method. The tin paste used in the present invention can form a micron-thick tin-rich pattern on the surface of bronze, and the thickness of the tin-rich pattern is 15-25 μm. The tin paste used in the present invention can not only produce a micron-level tin-rich pattern to ensure the aesthetics of the pattern, but also improve the wear resistance and corrosion resistance of the pattern.

[0031] Specifically, the solder paste prepared by the present invention is essentially a suspension composed of tin powder, organic acid tin, and organic acid. Among them, the tin powder is evenly distributed in the organic acid tin and the organic acid, and the pattern is drawn to ensure that the tin powder is evenly distributed in the decoration, so that it is easier to form a δ phase to ensure the aesthetics and wear resistance of the decoration. Among them, the main function of the organic acid tin is to increase the boiling point and thermal stability of the solution, and the main function of the organic acid is to remove the oxide layer on the surface of bronze. In addition, the organic acid tin also contained in the solder paste has high viscosity, is insoluble in water, and cannot be removed by grinding alone. Therefore, the organic acid tin in the tin-rich decoration can improve the corrosion resistance of the decoration.

[0032] In the process of drawing patterns, the metallic tin will sink into the bronze matrix due to the Kirkendall effect and form a tin-rich layer. It is known that after tin-plated bronze is heated at low temperature, copper and tin atoms will diffuse into each other due to the Kirkendall effect. Among them, the solid diffusion rate is related to the melting point of the material. The lower the melting point, the faster the diffusion rate. Because the diffusion rate of tin atoms is much higher than that of copper atoms, the tin-plated interface moves toward the edge of the bronze matrix, and the tin-plated layer will slowly sink into the bronze matrix, thus forming a micron-thick tin-rich pattern on the bronze ware. This tin-rich pattern is flush with the bronze surface, ensuring the beauty of the pattern.

[0033] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific examples.

[0034] The experimental materials used in the embodiments of the present invention are all conventional experimental materials in the art and can be purchased through commercial channels.

[0035] Example 1: A tinning method for drawing patterns on the surface of bronze imitations

[0036] (1) heating rosin to 100° C. to obtain liquid rosin, and mixing the liquid rosin, tin oxide, and tin powder in a mass ratio of 1.2:0.5:1 to obtain solder paste;

[0037] (2) Heat the solder paste to 220°C to make it molten, and use a pen to dip the molten solder paste to draw patterns on the bronze. During this process, slightly heat the bronze to a temperature equal to the melting point of the solder paste to prevent the solder paste at the tip of the pen from solidifying due to a sudden drop in temperature. Heat the bronze with the patterns drawn at 450°C for 1.5 hours. After the heating is completed, take out the object and cool it to room temperature. Use a flannel cloth dipped in metallographic polishing paste and an appropriate amount of clean water to wipe its surface for polishing. The black oxide layer on the surface of the bronze decoration will be retained, and a black tin-rich pattern will be presented, thus obtaining a tin-rich pattern.

[0038] Example 2: A tinning method for drawing patterns on the surface of bronze imitations

[0039] (1) heating stearic acid to 90° C. to obtain liquid stearic acid, and mixing the liquid stearic acid, tin oxide, and tin powder in a mass ratio of 1:0.8:1 to obtain solder paste;

[0040] (2) Heat the solder paste to 150°C to make it molten, and use a pen to dip the molten solder paste to draw patterns on the bronze. During this process, slightly heat the bronze to a temperature equal to the melting point of the solder paste to prevent the solder paste on the tip of the pen from solidifying due to a sudden drop in temperature. Heat the bronze with the drawn patterns at 430°C for 1 hour. After the heating is completed, take out the object, cool it to room temperature, and use 2500-grit sandpaper to polish its surface to remove the black oxide on the surface. The bronze surface can then present a silvery-white tin-rich pattern, resulting in a tin-rich pattern.

[0041] Example 3: A tinning method for drawing patterns on the surface of bronze imitations

[0042] (1) heating palmitic acid to 90° C. to obtain liquid palmitic acid, and mixing the liquid palmitic acid, tin oxide, and tin powder in a mass ratio of 1.1:0.8:1 to obtain solder paste;

[0043] (2) Heat the solder paste to 150°C to make it molten, and use a pen to dip the molten solder paste to draw patterns on the bronze. During this process, the bronze is slightly heated to a temperature equal to the melting point of the solder paste to prevent the solder paste on the tip of the pen from solidifying due to a sudden drop in temperature. The bronze with the drawn patterns is placed in a furnace and heated at 420°C for 2 hours. After the heating is completed, the object is taken out and cooled to room temperature. The surface is polished with 2500-grit sandpaper to remove the black oxide on the surface. The bronze surface can present a silvery-white tin-rich pattern, resulting in a tin-rich pattern.

[0044] Test Example 1:

[0045] The solder paste prepared in Example 1 was subjected to scanning electron microscope backscatter imaging analysis, and the results are as follows: Figure 1 As shown, the backscattered electron image mainly reflects the distribution of elements on the sample surface. The brighter the area, the higher the atomic coefficient, that is, the tin particles are the bright spots in the electron microscope backscattered imaging image. At the same time, the whole is selected as area 1, and areas 2-5 are selected according to whether there are bright spots in the scanning electron microscope backscattered imaging image, and energy spectrum analysis is performed on areas 1-5. The results are shown in Table 1.

[0046] Table 1 Figure 1 Energy spectrum analysis results corresponding to each region (wt%)

[0047]

[0048] Depend on Figure 1 It can be seen that there are obvious bright spots in area 2 and area 3, while area 4 and area 5 are dark homogeneous areas with no bright spots. The atomic coefficient of pure tin is very high, and it appears as a clear bright spot in the electron microscope backscattering imaging image, while the atomic coefficient of organic acid tin is low, and it does not appear as a bright spot in the electron microscope backscattering imaging image. It can be seen that the components of area 2 and area 3 are micron-sized tin powder, and the components of area 4 and area 5 are organic acid tin. At the same time, the micron-sized metal tin particles are evenly distributed in the organic acid tin.

[0049] From the energy spectrum analysis in Table 1, the content of Sn atoms in Region 2 and Region 3 is 92.4wt%-95.8wt%, and the tin content is extremely high. It can be seen that the components of Region 2 and Region 3 are micron-grade tin powder. Regions 4 and 5 contain Sn and C elements, with Sn content of 43.7wt%-49.0wt% and C content of 50.1wt%-55.4wt%. The content of tin and carbon elements is relatively high, which shows that the composition of Region 3 and Region 4 is organic acid tin. This is consistent with the conclusion obtained from the electron microscope backscattering imaging diagram.

[0050] Test Example 2:

[0051] The ultra-depth microscopic imaging analysis of the tin-plated decoration obtained in Example 1 shows the following results: Figure 2 The metallographic microscopic imaging analysis and scanning electron microscope backscatter imaging analysis of the tinned decorative edges are shown in the following figure. Figure 3-Figure 4 As shown in the figure, organic matter appears black under backscatter imaging, and if it forms a film, it will appear gray under backscatter imaging. Figure 4 Regions 1-5 are selected and energy spectrum analysis is performed on regions 1-5. The results are shown in Table 2.

[0052] Table 2 Figure 4 The energy spectrum analysis results of each region in

[0053]

[0054] Depend on Figure 2 It can be seen that there is no obvious interface between the tin-plated decorations and the bronze substrate obtained by the tin-plating method for drawing decorations on the bronze surface adopted by the present invention, and Figure 3 It can be seen that the thickness of the tin-plated decoration on the surface of the bronze substrate is 15-25 μm, the thickness of the tin-rich decoration at the edge gradually becomes thinner until it disappears, and the transition between the tin-rich decoration area and the dendrite structure on the bronze surface is smooth, without any height difference. It can be seen that the decoration drawn by the tin-plating method of the present invention still has no height difference with the bronze substrate, ensuring the aesthetics of the decoration.

[0055] Depend on Figure 4 It can be seen that regions 2 and 3 are gray areas, while regions 4 and 5 are black areas. The organic matter is black under backscatter imaging, and if it forms a film, it will appear gray under backscattering. It can be seen from Table 2 that the tin content in region 1 is 31.1wt%, and it can be seen that a tin-rich decorative layer composed of δ phase is generated. The C content in region 2 is 2.2wt%, and there is a small amount of film-forming organic matter on the surface of this region. Region 3 presents the surface element content of the exposed bronze matrix. The carbon content of the black area in regions 4 and 5 is 18.1wt%-23.8wt%, indicating that a large amount of high-grade organic acid tin remains in this area, and the organic acid tin is enriched in this area. It can be seen that since the solder paste prepared by the present invention contains organic acid tin with high viscosity and insoluble in water, it cannot be removed during the polishing process, so that the organic acid tin can be retained in the decoration and the surrounding area of ​​the decoration, which can improve the corrosion resistance of the area.

[0056] The organic acid salt prepared by the invention has high viscosity and is insoluble in water. The organic acid salt on the bronze surface cannot be completely removed by polishing, but the organic acid salt remaining on the bronze surface can improve the corrosion resistance.

[0057] Test Example 3:

[0058] In this test, the Rockwell hardness tester was used to measure the hardness of the patterns drawn on the bronze surface by different solder paste components. The results are shown in Table 3. Among them, this test example has four treatment groups, and the details of each treatment group are as follows:

[0059] Treatment Group 1: Untreated bronze block with 22% tin content

[0060] Treatment group 2: pure tin was directly plated on the bronze surface by hot-dip plating;

[0061] Treatment group 3: A metal paste was prepared by mixing rosin and pure tin powder in a mass ratio of 1.2:1, which was applied to the bronze surface and heated and polished to obtain silver patterns;

[0062] Treatment group 4: A mixture of rosin, tin oxide and pure tin powder in a mass ratio of 1.2:0.5:1 was used as solder paste.

[0063] Heat the solder paste to 200℃ to make it molten, and use a pen to dip the molten solder paste to draw patterns on the bronze. During this process, heat the bronze slightly to a temperature equal to the melting point of the solder paste to prevent the solder paste at the tip of the pen from solidifying due to a sudden drop in temperature. Heat the bronze with the drawn patterns at 450℃ for 1.5h. After the heating is completed, take out the object, cool it to room temperature, and use a flannel cloth dipped in metallographic polishing liquid to wipe its surface for polishing. The black oxide layer on the surface of the bronze decoration will be retained, presenting a black tin-rich pattern.

[0064] Table 3 Hardness of the corresponding patterns in each treatment group

[0065] Group Test area Metallographic structure of the test area Hardness(HRC) Treatment Group 1 Bronze base α+(α+δ) 62 Treatment Group 2 Tin coating Pure Tin 20 Treatment Group 3 Tin coating ε phase 55 Treatment Group 4 Tin coating Delta phase 75

[0066] Hardness is an important criterion for measuring wear resistance. Specifically, the higher the hardness of the test area, the better its wear resistance. As can be seen from Table 3, the base hardness of the bronze block with a tin content of 22% without tin plating is 62HRC; the hardness of the tin-plated layer on the surface of the bronze is only 20HRC after the common tin plating technology is adopted, that is, the bronze block is immersed in liquid tin and directly tinned; the metal paste prepared by mixing only rosin and pure tin, the main component of the silver tin-plated layer obtained after heating and polishing is ε phase, and the hardness is 55HRC; compared with conventional tin plating, the present invention uses pure tin powder, tin oxide and rosin to make tin paste for drawing patterns, and the hardness of the obtained patterns is 75HRC, which is 55HRC higher than the patterns made of pure tin, and the hardness can even be higher than the bronze base. It can be seen that the present invention adds tin oxide and rosin as tin paste on the basis of pure tin powder, which can significantly improve the hardness of the patterns, thereby improving the wear resistance of the patterns.

[0067] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A tinning method for drawing bronze surface decoration, characterized in that: The following steps are involved: (1) mixing liquid organic acid, tin oxide and tin powder to obtain solder paste; (2) After the solder paste is heated to a molten state, the molten solder paste is used to draw patterns on the bronze ware, and then the bronze ware with the drawn patterns is heated. After the heating is completed, the bronze ware is taken out and post-processed to form tin-rich patterns on the surface of the bronze ware, thus forming tin-rich patterns.

2. The tinning method according to claim 1, characterized in that: In step (1), the organic acid is one or more of rosin, stearic acid or palmitic acid.

3. The tinning method according to claim 1, characterized in that: In step (1), the liquid organic acid is obtained by heating the organic acid to 65-120°C.

4. The tinning method according to claim 1, characterized in that: In step (1), the mass ratio of liquid organic acid, tin oxide and tin powder is (1-1.5):(0.5-1):

1.

5. The tinning method according to claim 1, characterized in that: In step (2), the heating temperature is 150-220° C., and the heating time is ≥15 min.

6. The tinning method according to claim 1, characterized in that: In step (2), the heating temperature of the bronze ware with the pattern drawn is 430-450° C., and the heating time is 1-2 hours.

7. The tinning method according to claim 1, characterized in that: In step (2), the post-processing is grinding or polishing.

8. The tinning method according to claim 7, characterized in that: The polishing process is as follows: after taking out the bronze ware, cool it to room temperature, and use 2500-grit sandpaper to polish its surface to remove the black oxide on the surface. The bronze surface can then present a silvery-white tin-rich texture.

9. The tinning method according to claim 7, characterized in that: The polishing process is as follows: after taking out the bronze ware, cool it to room temperature, and use a flannel cloth dipped in a metallographic polishing paste to wipe its surface for polishing. The black oxide layer on the surface of the bronze decoration will be retained, and a black tin-rich texture will appear; the main component of the metallographic polishing paste is 0.25μm corundum.

10. The tinning method according to claim 1, characterized in that: The thickness of the tin-rich decoration is 15-25 μm.

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