A crystallizer and a horizontal continuous casting method for producing tin phosphor bronze bar

Abstract

The application discloses a crystallizer for preparing tin-phosphor bronze rod material and a horizontal continuous casting method, and the horizontal continuous casting method comprises the following steps: step one, feeding according to the composition ratio of the tin-phosphor bronze rod material and melting; and step two, carrying out drawing casting on the qualified molten liquid obtained in the step one, wherein the drawing casting pitch is 2-6 mm, the traction speed is 300-550 mm / s, the pause time is 100-300 ms, the inlet / outlet temperature of the cooling water of the crystallizer is 30-40 DEG C / 50-60 DEG C, the cooling water pressure is 0.04-0.08 MPa, the temperature of the holding furnace is 1140-1200 DEG C, the temperature of the graphite base is 750-900 DEG C, the drawing casting frequency is 100-150 times / min, the casting blank outlet temperature is 300-500 DEG C, and the electromagnetic stirring frequency is 30-50 HZ. The crystallizer and the horizontal continuous casting method have a good refining effect on the tin-phosphor bronze rod material, tin counter segregation is basically eliminated, the wire drawing cracking problem is solved, and the tensile strength of the tin-phosphor bronze rod material is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tin phosphor bronze bar preparation, and particularly relates to a crystallizer for preparing tin phosphor bronze bar and a horizontal continuous casting method. BACKGROUND

[0002] The tin phosphor bronze bar is a kind of material with high strength and high elasticity, has high elasticity, magnetic resistance and wear resistance, has good welding and brazing properties, has good machinability, and has good corrosion resistance in the atmosphere and fresh water, and is currently mainly applied to plug pins, wear-resistant parts and magnetic resistance elements matched with electrical and automobile connectors.

[0003] At present, the main process for producing tin phosphor bronze bar wire includes a continuous casting process and an extrusion process, the extrusion process is: continuous casting ingot-extrusion-stretching-annealing……straightening-sizing-finishing inspection-packing, and the largest market size is still continuous casting bar, that is, the continuous casting process is adopted, and the basic route of most continuous casting bars and other special-shaped materials is: continuous casting bar-stretching-skinning-(stretching-annealing-stretching……)-straightening-sizing-finishing inspection-packing. The main problems existing in the current production of tin phosphor bronze bar are concentrated in that tin severe segregation leads to cracking, the surface segregation is more than 2 mm, and the material strength cannot be stably improved to more than 500 MPa. How to improve the production drawing speed and the material strength by adjusting the casting process and the application of auxiliary casting tooling, and at the same time, how to consider the tin segregation problem are problems that need to be solved by the technical personnel in the field. SUMMARY

[0004] The present application aims at the deficiencies in the prior art, and provides a crystallizer for preparing tin phosphor bronze bar and a horizontal continuous casting method.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0006] The first aspect of the present application is to provide a crystallizer for preparing tin phosphor bronze bar, which comprises a crystallization tube and a cooling jacket, the cooling jacket comprises an inner tube, an intermediate tube, an outer tube and a water distribution ring, wherein the crystallization tube is provided with a liquid pumping mechanism, the cooling jacket is arranged outside the crystallization tube, and the cooling jacket is a three-layer tube structure, the length of the crystallization tube is 1.2-1.8 m, the water inlet cavity is formed between the outer tube and the intermediate tube, the water outlet cavity is formed between the intermediate tube and the inner tube, the radial cross-sectional area of the water outlet cavity is smaller than that of the water inlet cavity; one end of the crystallization tube is connected with a graphite base, and a water cooling jacket is arranged on the outer wall of the graphite base; the crystallization tube between the cooling jacket and the graphite base is provided with an electromagnetic stirrer.

[0007] The second aspect of the present application is to provide a horizontal continuous casting method for preparing tin phosphor bronze bar, using the above-mentioned crystallizer, comprising the following steps:

[0008] Step one, according to the composition of tin phosphor bronze bar, the raw materials are added, and smelting is carried out;

[0009] Step two, the qualified molten liquid obtained in step one is drawn, wherein the drawing pitch is 2-6mm, the drawing speed is 300-550mm / s, the pause time is 100-300ms, the inlet / outlet temperature of the crystallizer cooling water is 30-40℃ / 50-60℃, the cooling water pressure is 0.04-0.08MPa, the temperature of the holding furnace is 1140-1200℃, the temperature of the graphite base is 750-900℃, the drawing frequency is 100-150 times / min, the cast billet outlet temperature is 300-500℃, and the electromagnetic stirring frequency is 30-50HZ.

[0010] Further, the drawing frequency is 100-130 times / min.

[0011] Further, the cast billet outlet temperature is 350-470℃.

[0012] Further, the drawing speed is 300-520mm / s.

[0013] Further, the drawing pitch is 3-5mm.

[0014] Further, the specific steps of smelting are as follows:

[0015] 1) Add electrolytic plate, pure iron wire and return material in the melting furnace without covering, after complete melting, the voltage is set to the holding mode, add tin block, phosphor copper and zinc block, take sample for testing after 5 minutes, add deslagging agent for deslagging;

[0016] 2) After the composition is qualified, the converter is turned on, the converter temperature is required to be 1200-1250℃, the graphite scale is used for covering, the temperature of the holding furnace is raised to 1160-1180℃, the composition is sampled and tested, after the composition is qualified, 0.1kg of phosphor copper is added as a deoxidizer.

[0017] Further, the tin phosphor bronze bar comprises the following components in mass percentage: Sn 6.0-7.0%, P 0.1-0.25%, Fe 0.03-0.05%, Zn 0.15-0.2%, Pb<0.01%, Ni<0.2%, and the balance is Cu and unavoidable impurities.

[0018] The present application adopts the above technical scheme, compared with the prior art, has the following technical effects:

[0019] The crystallizer and the horizontal continuous casting method have good refining effect on tin phosphor bronze bar, tin reverse segregation is basically eliminated, wire drawing cracking problem is solved, and the tensile strength of the tin phosphor bronze bar is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A structure diagram of the crystallizer for preparing tin phosphor bronze bar according to the present application;

[0021] Figure 2 A structure diagram of the crystallizer for preparing tin phosphor bronze bar according to the present application; Figure 1 An enlarged view of A in FIG. 1;

[0022] Figure 3 A metallographic diagram of the tin phosphor bronze bar prepared in Example 1 of the present application;

[0023] Figure 4 A metallographic diagram of the tin phosphor bronze bar prepared in Example 2 of the present application;

[0024] Figure 5 A metallographic diagram of the tin phosphor bronze bar prepared in Example 3 of the present application;

[0025] Figure 6 A metallographic diagram of the tin phosphor bronze bar prepared in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0026] The present application will be further described below in conjunction with the drawings and specific examples, but not as a limitation of the present application. It should be noted that the examples in the present application and the features in the examples can be combined with each other without conflict.

[0027] Reference Figures 1-2The application provides a crystallizer for preparing tin phosphor bronze bar material, which comprises a crystallization tube 1 and a cooling jacket, the cooling jacket comprises an inner tube 2, an intermediate tube 3, an outer tube 4 and a water distribution ring 5, wherein the crystallization tube 1 is internally provided with a liquid pumping mechanism, the cooling jacket is arranged outside the crystallization tube 1, and the cooling jacket is a three-layer tube structure, it is to be noted that the above are all prior art and will not be repeated here, the length of the above crystallization tube 1 is 1.2-1.8 m, the application adopts a long crystallizer, the bar material can be cooled from the radial direction and the axial direction, due to the large temperature gradient in the radial direction and the axial direction, uniform nucleation is promoted, more nucleation centers are obtained, thereby the bar material with fine and uniform grains is obtained, tin segregation is avoided, and the strength of the material is improved; the outer tube 4 and the intermediate tube 3 form a water inlet cavity, the intermediate tube 3 and the inner tube 2 form a water outlet cavity, the radial cross-sectional area of the water outlet cavity is smaller than that of the water inlet cavity, cooling water uniformly enters the cooling area through the water distribution ring 5, uniform heat exchange of the bar material is realized, the regional mixed crystal problem is avoided, the consistency of the material performance is improved, the flow rate is rapidly improved in the narrow water gap (the radial cross-sectional area of the water outlet cavity is smaller than that of the water inlet cavity), more heat is taken away to achieve the purpose of intensified cooling, and tin segregation is further weakened; one end of the crystallization tube 1 is connected with a graphite base 6, a water cooling jacket 7 is arranged on the outer wall of the graphite base 6, so that temperature control is realized; the crystallization tube between the cooling jacket and the graphite base 6 is provided with an electromagnetic stirrer 8, the electromagnetic stirring tooling is installed before the crystallizer solidifies, more grain cores are realized, the crystallizer organization is refined, and the tin counter segregation problem is weakened.

[0028] The application also provides a horizontal continuous casting method for preparing tin phosphor bronze bar material, which comprises the following steps.

[0029] Step one, according to the composition ratio of the tin phosphor bronze bar material, the raw materials are put into the furnace and melted;

[0030] Step two, the qualified molten liquid obtained in step one is drawn, wherein the drawing pitch is 2-6 mm, the drawing speed is 300-550 mm / s, the pause time is 100-300 ms, the inlet / outlet temperature of the cooling water of the crystallizer is 20-40 DEG C / 50-60 DEG C, the cooling water pressure is 0.04-0.08 MPa, the temperature of the holding furnace is 1140-1200 DEG C, the temperature of the graphite base is 750-900 DEG C, the drawing frequency is 100-150 times / min, the outlet temperature of the cast blank is 300-500 DEG C, and the electromagnetic stirring frequency is 30-50 HZ.

[0031] Further preferably, the above drawing frequency is 100-130 times / min.

[0032] The surface reverse segregation of the tin-phosphor bronze is obvious when the drawing frequency is below 100 times / min, and the surface reverse segregation of the tin-phosphor bronze is weakened when the drawing frequency is above 100 times / min, which indicates that the high-frequency drawing can effectively weaken the surface reverse segregation of the tin-phosphor bronze. When the drawing frequency is higher than 150 times / min, the crystallization quality of the casting blank is poor, and the surface quality is deteriorated. Increasing the drawing frequency and the vibration during crystallization can effectively increase the nucleation amount, refine the grains, and weaken the regional segregation of the bronze. When the frequency is higher than a certain value, although the grains are relatively fine, the high frequency will deteriorate the quality of the casting blank and reduce the cold working performance of the casting blank. The main reason is that when the frequency is high to a certain extent, although the grains can be refined, the crystallization condition is affected, such as the high frequency will lead to insufficient crystallization compensation, thereby reducing the density of the casting blank, and the cold working performance of the casting blank is also reduced. When the drawing frequency is stabilized at 100-130 times / min, the elongation of the casting blank can be stabilized at about 40%.

[0033] Further preferably, the casting blank outlet temperature is 350-470℃.

[0034] When the outlet temperature of the horizontal continuous casting casting blank is above 500℃, the surface segregation phase is easy to further gather to form large pieces (such as plum blossom shape), and even the enrichment phase is connected into pieces, thereby further deteriorating the processing performance of the casting blank. When the outlet temperature is below 300℃, the casting process is prone to breakage, mainly because the crystallization line is moved backward, the drawing resistance is increased, and the solidification is insufficient. Considering that the water cooling experiment of the bronze is air cooling to a certain temperature and then water cooling, compared with the horizontal continuous casting crystallizer cooling and then secondary water cooling, the cooling intensity is low during the air cooling stage, and therefore the temperature of the tin-rich phase is likely to be low. When the outlet temperature is about 350-470℃, the elongation of the casting blank is good.

[0035] Further preferably, the drawing speed is 300-520mm / s.

[0036] When the drawing speed of the casting blank is higher than 550mm / s, the segregation of tin is serious, and there is a risk of copper leakage. When the drawing speed is lower than 300mm / s, the casting blank is prone to breakage and cannot be drawn, and the bar is directly frozen in the crystallizer. When the drawing speed is 300-520mm / s, the elongation of the casting blank is relatively stable, and the quality of the casting blank is good.

[0037] Further preferably, the drawing pitch is 3-5mm.

[0038] When the drawing pitch is higher than 7mm, the quality of the casting blank is deteriorated, the crystalline lines penetrate into the casting blank, and the bar is directly scrapped. When the drawing pitch is lower than 2mm, the efficiency is low. In addition, the drawing pitch lower than 2mm or higher than 7mm will cause the reverse segregation of tin. When the drawing pitch is 3-5mm, the elongation of the casting blank can be stabilized at about 40%.

[0039] In the present application, the pause time is 100-300 ms, and a pause time lower than 100 ms will cause poor surface quality of the casting blank and crystallization supplement; a pause time higher than 300 ms will cause the problem of broken wire. The inlet / outlet temperature of the crystallizer cooling water is 30-40℃ / 50-60℃, and the inlet water temperature is set to 30-40℃ mainly because this temperature is in the stable natural air temperature, and will not cause obvious metal ion deposition and the problem of reduced cooling intensity caused by high temperature. The temperature of the holding furnace is 1140-1200℃, and a temperature lower than 1140℃ will cause the problem of being unable to pull the wire, and a temperature higher than 1200℃ will cause tin segregation and the problem of porosity of the rod blank.

[0040] In the present application, the temperature of the graphite base is 750-900℃, and when lower than 750℃, the drawing and casting process cannot be smoothly carried out, directly leading to the problem of broken wire. Higher than 900℃ will directly cause copper leakage, and the melt alloy elements will also be seriously oxidized and burned, and the development of the organization grain dendrite is serious, and the solidification liquid cavity is too deep, which will cause more serious tin counter segregation, and the temperature needs to be controlled by installing a water cooling jacket at the base of the crystallizer.

[0041] In the present application, the electromagnetic stirring frequency is 30-50 HZ, and the electromagnetic stirring tool is installed at the solidification front of the crystallizer to realize more grain cores and refine the crystallizer organization, thereby weakening the problem of tin counter segregation. Lower than 30 HZ will cause insufficient stirring force, and greater than 50 HZ will cause the problems of surface cracking and scarring of the rod and disrupt the sequential crystallization process.

[0042] As a preferred example, the specific steps of the above melting are as follows:

[0043] 1) Add electrolytic plate, pure iron wire and return material in the melting furnace without covering, and after complete melting, the voltage is set to the holding mode, tin blocks, phosphor copper and zinc blocks are added, and after 5 minutes, sampling and testing are performed, and deslagging agent is added for deslagging;

[0044] 2) After the composition is qualified, the converter is converted, the converter temperature is required to be 1200-1250℃, the graphite scale is used for covering, the temperature of the holding furnace is increased to 1160-1180℃, the composition is sampled and tested, and after the composition is qualified, 0.1 kg of phosphor copper is added as a deoxidizer.

[0045] Embodiment

[0046] The present application provides seven examples and one comparative example, wherein the tin phosphor bronze rod material comprises the following components by mass percentage: Sn 6.5%, P 0.12%, Fe 0.031%, Zn 0.15%, Pb <0.01%, Ni <0.2%, and the balance of Cu and inevitable impurities. The process parameters of the continuous casting method used in Examples 1-7 and Comparative Example 1 are shown in Table 1, wherein the mold cooling water inlet temperature is 35°C and the electromagnetic stirring frequency is 30HZ, which are not repeated in Table 1:

[0047] Table 1

[0048]

[0049] The tin phosphor bronze rod material prepared in Examples 1-7 and Comparative Example 1 was tested for performance, and the tensile extension test standard was GB / T 228-2002 Metal Material Tensile Test Method at Room Temperature; the hardness test standard was GB / T 4340.1-1999 Metal Vickers Hardness Test Part 1: Test Method; the grain size test standard was GB / T 36165-2018 Metal Average Grain Size Determination; and the metallographic segregation test standard was GB / T 224-2008, and the results are shown in Table 2. Figures 3-6

[0050] Figure 3 The metallographic phase diagram of the tin phosphor bronze rod material prepared in Example 1 (left: transverse-edge grain size 0.015mm; right: transverse-center grain size 0.015mm), from the above results, the tin phosphor bronze rod material has fine and uniform grains, the alpha phase is the matrix phase, and there are a small amount of Pb phase, CuSn phase, no local phase organization growth anomaly is seen, the second phase Pb phase + CuSn phase is uniformly distributed, and no regional segregation problem occurs.

[0051] Figure 4 The metallographic phase diagram of the tin phosphor bronze rod material prepared in Example 2 (left: transverse-edge grain size 0.015mm; right: transverse-center grain size 0.015mm), from the above results, the tin phosphor bronze rod material has fine and uniform grains, the alpha phase is the matrix phase, and there are a small amount of Pb phase, CuSn phase, no local phase organization growth anomaly is seen, the second phase Pb phase + CuSn phase is uniformly distributed, and no regional segregation problem occurs, there is weak dendrite, the insufficient refining process during smelting and insufficient undercooling during casting cooling lead to insufficient number of heterogeneous nucleation and spontaneous nucleation, and the overheat leads to small number of grains and developed dendrites.

[0052] Figure 5 ​The metallograph of the tin phosphor bronze rod prepared for the example 3 (left: horizontal grain size 0.015mm; right: vertical grain size 0.015mm), from the above results, the tin phosphor bronze rod has fine and uniform grain, the alpha phase is the matrix phase, and a small amount of Pb phase, CuSn phase exists, no local phase organization growth anomaly is found, the second phase Pb phase+CuSn phase is uniformly distributed, and no regional segregation problem occurs.

[0053] Figure 6 The metallograph of the tin phosphor bronze rod prepared for the example 3 (left: horizontal grain size 0.015mm; right: vertical grain size 0.015mm), from the above results, the tin phosphor bronze rod has fine and uniform grain, the alpha phase is the matrix phase, and a small amount of Pb phase, CuSn phase exists, no local phase organization growth anomaly is found, the second phase Pb phase+CuSn phase is uniformly distributed, and no regional segregation problem occurs.

[0054] Table 2

[0055] Tensile strength MPa Hardness Hv Elongation % Grain size um Thickness of counter-dead layer Example 1 500 150 / 139 / 142 30 0.025 0.1 Example 2 520 150 / 141 / 142 35 0.015 0.12 Example 3 525 140 / 150 / 145 36 0.02 0.15 Example 4 515 140 / 146 / 143 40 0.015 0.11 Example 5 510 151 / 147 / 139 35 0.02 0.14 Example 6 520 147 / 145 / 147 42 0.03 0.13 Example 7 524 146 / 148 / 146 38 0.02 0.17 Comparative Example 1 465 130 / 148 / 155 18 0.06 0.5

[0056] The above only describes the preferred embodiments of the present application, and does not limit the implementation and protection scope of the present application. It should be realized by those skilled in the art that any equivalent replacement and obvious change made according to the content of the present application and the drawings should be included in the protection scope of the present application.

Claims

1. A horizontal continuous casting method for preparing tin-phosphor bronze rods, comprising a crystallizer for preparing tin-phosphor bronze rods, characterized in that, The crystallizer includes a crystallization tube and a cooling jacket. The cooling jacket includes an inner tube, a middle tube, an outer tube, and a water distribution ring. The crystallization tube contains a liquid extraction mechanism. The cooling jacket is located outside the crystallization tube and has a three-layer tube structure. The crystallization tube has a length of 1.2-1.8 m. A water inlet cavity is formed between the outer tube and the middle tube, and a water outlet cavity is formed between the middle tube and the inner tube. The radial cross-sectional area of ​​the water outlet cavity is smaller than that of the water inlet cavity. One end of the crystallization tube is connected to a graphite base, and a water-cooling jacket is provided on the outer wall of the graphite base. An electromagnetic stirrer is provided on the section of the crystallization tube without the cooling jacket between the cooling jacket and the graphite base. The horizontal continuous casting method includes the following steps: Step 1: Add materials according to the composition ratio of tin-phosphor bronze rods and smelt them; Step 2: Cast the qualified molten liquid obtained in Step 1 by pull casting. The pull casting pitch is 2-6mm, the traction speed is 300-550mm / s, the pause time is 100-300ms, the inlet / outlet temperature of the crystallizer cooling water is 30-40℃ / 50-60℃, the cooling water pressure is 0.04-0.08MPa, the holding furnace temperature is 1140-1200℃, the graphite base temperature is 750-900℃, the pull casting frequency is 100-150 times / min, the billet outlet temperature is 300-500℃, and the electromagnetic stirring frequency is 30-50HZ.

2. The horizontal continuous casting method according to claim 1, characterized by, The casting frequency is 100-130 times / min.

3. The horizontal continuous casting method according to claim 1, characterized by, The outlet temperature of the billet is 350-470℃.

4. The horizontal continuous casting method according to claim 1, characterized by, The traction speed is 300-520 mm / s.

5. The horizontal continuous casting method according to claim 1, characterized by, The casting pitch is 3-5 mm.

6. The horizontal continuous casting method according to claim 1, characterized by The specific steps of the smelting process are as follows: 1) Add electrolytic plates, pure iron wire and recycled material to the melting furnace without covering it. After all the material has melted, turn the voltage to the heat preservation setting, add tin blocks, phosphor bronze and zinc blocks. Take a sample for testing after 5 minutes, add slag remover and remove slag. 2) After the composition is qualified, the converter is used. The converter temperature is required to be 1200-1250℃. Graphite flakes are used to cover the furnace and the temperature of the holding furnace is increased to 1160-1180℃. Samples are taken to test the composition. After the composition is qualified, 0.1kg of phosphorus copper is added as a deoxidizer.

7. The horizontal continuous casting method according to claim 1, characterized by The tin-phosphorus bronze rod comprises the following components by mass percentage: Sn 6.0-7.0%, P 0.1-0.25%, Fe 0.03-0.05%, Zn 0.15-0.2%, Pb < 0.01%, Ni < 0.2%, with the balance being Cu and unavoidable impurities.

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