A HSn62-1 tin brass ingot organization homogenization heat treatment method

Abstract

The present application relates to the technical field of metal heat treatment, in particular to a HSn62-1 tin brass ingot organization homogenization heat treatment method, to solve the current HSn62-1 tin brass semi-continuous casting ingot blank exists dendritic segregation serious, grain coarsening, uneven structure, low plasticity and poor mechanical properties problem. The method is to heat HSn62-1 tin brass ingot to 100-200 ℃ below the solidus and long time holding, using solute atom diffusion at high temperature, fill in the dendritic stem and dendritic interstitial difference, effectively eliminate the dendritic segregation of HSn62-1 tin brass ingot, make the as-cast organization chemical composition homogenization; again through high temperature to promote part of low melting point eutectic solution, thus eliminating the phase hindering grain boundary migration, recrystallization occurs in the subsequent cooling process to form equiaxed crystal, effectively improve the proportion of HSn62-1 tin brass equiaxed crystal, and the organization density significantly improves, alpha and beta phase distribution is uniform, avoid the as-cast organization coarsening and uneven, effectively improve the mechanical and electrical properties of T46300 tin brass ingot.

Description

Technical Field

[0001] This invention relates to the field of metal heat treatment technology, specifically to a heat treatment method for homogenizing the microstructure of HSn62-1 tin brass ingots. Background Technology

[0002] HSn62-1 (T46300) tin brass, also known as naval brass, is a typical special brass alloy. By adding 0.7%-1.1% tin to ordinary brass, it has medium strength, excellent seawater corrosion resistance, weldability, and cold working performance. It is widely used in shipbuilding for parts that come into contact with seawater or gasoline, as well as precision mold parts, electronic contacts, pipe fittings, and other products with high material performance requirements. Currently, the semi-continuous casting process is mainly used in industry to prepare HSn62-1 tin brass ingots. However, during non-equilibrium solidification, due to the difference in solute redistribution at the solidification front, severe dendritic segregation is easily formed inside the ingot. At the same time, there are defects such as coarse grains, uneven distribution of α and β phases, and poor microstructure. This results in low plasticity of the as-cast alloy (elongation of only about 26%), large strength fluctuations, and unstable hardness and conductivity. This seriously restricts the smooth progress of subsequent plastic processing processes such as rolling, extrusion, and stretching, and will reduce the service life and reliability of the final product. Conventional low-temperature annealing can only partially eliminate casting stress and cannot completely eliminate dendritic segregation. If the heat treatment temperature is too high, it is very easy to cause abnormal grain growth or even overheating, which will deteriorate the overall performance of the alloy. Summary of the Invention

[0003] This invention provides a heat treatment method for homogenizing the microstructure of HSn62-1 tin brass ingots to solve the problems mentioned above.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A heat treatment method for homogenizing the microstructure of HSn62-1 tin brass ingots includes the following steps: Step 1: Using electrolytic copper with a purity ≥ 99.95%, pure zinc ingots with a purity ≥ 99.995%, and pure tin ingots with a purity ≥ 99.966% as raw materials, smelting is carried out according to the standard composition ratio of HSn62-1 tin brass. Ingots are prepared using a semi-continuous casting process, and HSn62-1 tin brass ingots are obtained. The chemical composition of HSn62-1 tin brass ingots, by weight percentage, is: Cu: 61.0-63.0%, Sn: 0.7-1.1%, Fe: ≤0.1%, Pb: ≤0.1%, S: 0.002-0.003%, total impurities ≤0.3%, with the balance being Zn. HSn62-1 tin brass ingot samples are prepared using wire cutting equipment.

[0005] Step 2: The prepared HSn62-1 tin brass ingot sample is loaded into a natural gas regenerative heating furnace and heated to 620℃-820℃ at a rate of 3℃ / min-7℃ / min, and kept at that temperature for 3h-5h.

[0006] Step 3: After the heat preservation is completed, the HSn62-1 tin brass ingot sample is air-cooled to room temperature to finally obtain the HSn62-1 tin brass ingot sample with homogenized structure.

[0007] Furthermore, the HSn62-1 tin brass ingot sample produced by the wire cutting equipment in step 1 has a size of 230mm×220mm×20mm.

[0008] The present invention has the following beneficial effects: This invention provides a heat treatment method for homogenizing the microstructure of HSn62-1 tin brass ingots. The method involves heating the HSn62-1 tin brass ingot to 100-200°C below the solidus and holding it at that temperature for an extended period. Utilizing the full diffusion of solute atoms at high temperatures, the method fills in the compositional differences between dendrite trunks and interdendrites, effectively eliminating dendrite segregation in the HSn62-1 tin brass ingot and homogenizing the chemical composition of the as-cast microstructure. Furthermore, high temperature promotes the dissolution of some low-melting-point eutectic, thereby eliminating substances that hinder grain boundary migration. During the subsequent cooling process, the α and β phases recrystallize to form equiaxed crystals, which effectively increases the proportion of equiaxed crystals in HSn62-1 tin brass and significantly improves the density of the microstructure. The α and β phases are evenly distributed, avoiding the coarse and uneven microstructure in the as-cast state. This effectively improves the mechanical and electrical properties of T46300 tin brass ingots and solves the problems of severe dendrite segregation, coarse grains, uneven microstructure, low plasticity, and poor mechanical properties in the current semi-continuous casting billet of HSn62-1 tin brass. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the macrostructure of the HSn62-1 tin brass ingot sample after homogenization heat treatment at 820℃ for 5h in Example 3 of the present invention.

[0010] Figure 2 This is a schematic diagram of the macrostructure of the HSn62-1 tin brass ingot sample that has not undergone homogenization heat treatment in this invention.

[0011] Figure 3 This is a schematic diagram showing the equiaxed crystal ratio and triangular region length of the HSn62-1 tin brass ingot samples after homogenization heat treatment in Examples 1-3 of the present invention.

[0012] Figure 4 This is a schematic diagram showing the changes in mechanical properties of HSn62-1 tin brass ingot samples after homogenization heat treatment in Examples 1-4 of the present invention.

[0013] Figure 5 This is a schematic diagram showing the changes in hardness and conductivity of HSn62-1 tin brass ingot samples after homogenization heat treatment in Examples 1-4 of the present invention. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Example 1

[0015] Step 1: Produce HSn62-1 tin brass ingots using a semi-continuous casting process. The chemical composition, by weight percentage, is: Cu: 61.0-63.0%, Sn: 0.7-1.1%, Fe: ≤0.1%, Pb: ≤0.1%, S: 0.002-0.003%, total impurities ≤0.3%, with the balance being Zn. Prepare HSn62-1 tin brass ingot samples of 230mm×220mm×20mm using wire cutting equipment, and number them 1#. Step 2: The HSn62-1 tin brass ingot sample is loaded into a natural gas regenerative heating furnace and heated to 620℃ at a rate of 3℃ / min. The sample is then held at 620℃ for 5 hours to perform homogenization heat treatment. Step 3: After the heat treatment is completed, the sample is air-cooled to room temperature to obtain a homogenized heat-treated sample. Then, the final HSn62-1 tin brass ingot sample is subjected to low-magnification microstructure analysis. The results show that the equiaxed crystal ratio of the HSn62-1 tin brass ingot is 47%, and the length of the triangular region is 110 mm. Example 2

[0016] Step 1: Produce HSn62-1 tin brass ingots using a semi-continuous casting process. The chemical composition, by weight percentage, is: Cu: 61.0-63.0%, Sn: 0.7-1.1%, Fe: ≤0.1%, Pb: ≤0.1%, S: 0.002-0.003%, total impurities ≤0.3%, with the balance being Zn. Prepare HSn62-1 tin brass ingot samples of 230mm×220mm×20mm using wire cutting equipment, and number them as 2#. Step 2: The HSn62-1 tin brass ingot sample is loaded into a natural gas regenerative heating furnace and heated to 720℃ at a rate of 5℃ / min. The sample is then held at 720℃ for 5 hours to perform homogenization heat treatment. Step 3: After the heat treatment is completed, the sample is air-cooled to room temperature to obtain a homogenized heat-treated sample. Then, the final HSn62-1 tin brass ingot sample is subjected to low-magnification microstructure analysis. The results show that the equiaxed crystal ratio of the HSn62-1 tin brass ingot is 51%, and the length of the triangular region is 114 mm. Example 3

[0017] Step 1: Produce HSn62-1 tin brass ingots using a semi-continuous casting process. The chemical composition, by weight percentage, is: Cu: 61.0-63.0%, Sn: 0.7-1.1%, Fe: ≤0.1%, Pb: ≤0.1%, S: 0.002-0.003%, total impurities ≤0.3%, with the balance being Zn. HSn62-1 tin brass ingot samples of 230mm×220mm×20mm are prepared using wire cutting equipment and numbered 3#. Step 2: The HSn62-1 tin brass ingot sample is loaded into a natural gas regenerative heating furnace and heated to 820℃ at a rate of 7℃ / min. The sample is then held at 820℃ for 5 hours to perform homogenization heat treatment. Step 3: After the heat treatment, the sample was air-cooled to room temperature to obtain a homogenized heat-treated sample. Then, low-magnification microstructure analysis was performed on the final HSn62-1 tin brass ingot sample. The results showed that the equiaxed grain ratio of the HSn62-1 tin brass ingot was 53%, and the length of the triangular region was 121 mm. Figure 1 and Figure 3 As shown, the macrostructure of the HSn62-1 tin brass ingot sample without homogenization heat treatment is as follows: Figure 2 As shown. Example 4

[0018] The HSn62-1 tin brass ingot sample prepared in step one of Example 1 was tested directly without undergoing heat treatment to homogenize it, and was numbered 4#.

[0019] The mechanical and electrical properties of the HSn62-1 tin brass ingot samples obtained in Examples 1-4 were tested respectively. The performance comparison results of the HSn62-1 tin brass ingot samples under different homogenization heat treatment processes are shown in Table 1.

[0020] Table 1. Comparison of performance tests of HSN62-1 tin brass samples under different homogenization heat treatment processes

[0021] The performance comparison of HSn62-1 tin brass ingot samples under different homogenization heat treatment processes is shown in Table 1. Based on the binary phase diagram of copper-zinc alloys, it can be seen that during high-temperature annealing, the β phase in the HSn62-1 tin brass ingot samples initially decreases and then increases. During homogenization heat treatment at 620℃, the matrix structure is dominated by the α phase, with the β phase having the lowest mass fraction, resulting in the best alloy plasticity. The recrystallization temperature of copper-zinc alloys is 300℃-330℃. Using a high-temperature homogenization heat treatment range of 620-820℃, the HSn62-1 tin brass ingot samples underwent complete recrystallization. With increasing homogenization temperature, grain growth and coarsening occurred. The recrystallized grains continued to grow, and the α and β phases continuously transformed into equiaxed grains. The grain boundary area and dislocation pile-up density continuously increased, hindering dislocation slip. The alloy's strength gradually increased, while its plasticity slightly decreased, resulting in optimal overall mechanical properties. In addition, the conductivity of cast alloys is usually at its lowest level. After homogenization heat treatment, the non-equilibrium phase at the grain boundaries of the alloy gradually dissolves, the point defects inside the crystal are reduced, the lattice electric field distribution becomes more uniform, the resistivity decreases, and the conductivity is significantly improved.

Claims

1. A heat treatment method for homogenizing the microstructure of HSn62-1 tin brass ingots, characterized in that, Includes the following steps: Step 1: Using electrolytic copper with a purity ≥ 99.95%, pure zinc ingots with a purity ≥ 99.995%, and pure tin ingots with a purity ≥ 99.966% as raw materials, smelting is carried out according to the standard composition ratio of HSn62-1 tin brass. Ingots are prepared using a semi-continuous casting process, and HSn62-1 tin brass ingots are obtained. The chemical composition of HSn62-1 tin brass ingots, by weight percentage, is: Cu: 61.0-63.0%, Sn: 0.7-1.1%, Fe: ≤0.1%, Pb: ≤0.1%, S: 0.002-0.003%, total impurities ≤0.3%, with the balance being Zn. HSn62-1 tin brass ingot samples are prepared using wire cutting equipment. Step 2: The prepared HSn62-1 tin brass ingot sample is loaded into a natural gas regenerative heating furnace and heated to 620℃-820℃ at a rate of 3℃ / min-7℃ / min, and kept at that temperature for 3h-5h. Step 3: After the heat preservation is completed, the HSn62-1 tin brass ingot sample is air-cooled to room temperature to finally obtain the HSn62-1 tin brass ingot sample with homogenized structure.

2. The heat treatment method for homogenizing the microstructure of HSn62-1 tin brass ingots according to claim 1, characterized in that: The HSn62-1 tin brass ingot sample obtained by the wire cutting equipment in step 1 has a size of 230mm×220mm×20mm.

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