A brass alloy and a method of manufacturing and use thereof

Abstract

The application discloses a brass alloy which is composed of the following mass percentages: Cu: 61.5-63.0 wt%, X: 0.002-0.02 wt%, Fe+Sn+Al+Pb≤0.035 wt%, and the balance is Zn and inevitable impurities except Fe, Sn and Al, wherein X is one or more of P, S and Mg; the microstructure of the brass alloy is alpha+beta phase, wherein the volume fraction of the beta phase is 9-16%, the twin area fraction is 8-20%, and the total dislocation density is 6.0-8.0*10 7 mm / mm 3 . The brass alloy has small friction with a die in a stamping process, so that the thickness of the prepared brass insert piece meets the tolerance requirement. The application further discloses a preparation method and application of the brass alloy.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of copper alloy materials and processes, and particularly relates to a brass alloy and a preparation method and application thereof. BACKGROUND

[0002] The power plug is used in all walks of life of our life and work, especially in the household appliance and communication industry, and is closely related to people's life and work. The power plug refers to a device for connecting an electrical appliance to a power source, characterized by three flat blades, which are metal components for directly connecting the electrical appliance to the power source, and are mostly made of brass plated with nickel.

[0003] The processing flow of the blade is: brass round bar base material -> cutting -> drilling and turning (one end) -> cleaning -> stamping and flattening (the other end) -> edge cutting -> electroplating -> CCD visual inspection.

[0004] The stamping process refers to plastic deformation of a metal blank under the condition of not breaking to obtain a finished product or semi-finished product with a certain shape and size. The base material of stamping is an important factor affecting the quality of parts and the service life of the die, and the performance requirement of the base material for stamping is good mechanical properties and large deformation capacity.

[0005] Brass is a binary alloy composed of Cu and Zn, and can be divided into single-phase brass and dual-phase brass according to the structure. The two phases of the dual-phase brass are alpha phase and beta phase, the Cu content of the dual-phase brass is between 56.6-62.4wt%, the alpha phase is a solid solution in which Zn is dissolved in Cu and has the same crystal structure as Cu, so the alpha phase is soft and has good plasticity; the beta phase is a solid solution based on the electronic compound CuZn and has a body-centered cubic crystal structure, good high-temperature plasticity, but is hard and brittle at room temperature, and the morphology and distribution ratio of the alpha phase and the beta phase will affect the performance of the brass.

[0006] When the brass round bar is stamped into a blade, the thickness tolerance of the blade is required to fluctuate in the range of δ±0.02mm (δ is the standard thickness of the blade), with the improvement of the automation degree of the stamping equipment and the requirement for the processing precision of the blade, the market generally feedbacks that the thickness tolerance of the blade fluctuates greatly when the brass round bar is stamped into a blade. At the beginning of stamping, the thickness tolerance fluctuation reaches about ±0.015mm, after 0.5 hours of stamping, the thickness tolerance fluctuation becomes about +0.02mm, after 1 hour of stamping, the thickness tolerance fluctuation reaches more than +0.025mm, which exceeds the specified requirement. In order to avoid the thickness tolerance of the blade exceeding the range, the machine has to be stopped for adjustment every half an hour or even dozens of minutes, which greatly reduces the production efficiency of the equipment and increases the auxiliary working time.

[0007] When the material is compressed, if the stamping force is greater than the yield strength of the material, the material will plastically deform to generate an initial deformation amount, after the stamping force is unloaded, the material first recovers along the elastic line and then reverses the deformation to generate a reverse deformation amount, and the initial deformation amount minus the reverse deformation amount is the actual stamping deformation amount. With the continuous stamping, if the actual stamping deformation amount gradually decreases, it means that the thickness of the insert piece will gradually increase.

[0008] The reason for this problem is that the phase morphology and distribution, grain size, crystal structure, and dislocation distribution in the microstructure of the brass bar cannot meet the stamping requirements of the insert piece. When the material is flattened, it is not only subjected to the stamping force, but also subjected to the friction force (adhesion resistance) between the material and the die. Due to the defects in the microstructure of the brass bar prepared by the current method, the adhesion resistance between the blank and the die gradually increases, and the actual stamping force acting on the blank gradually decreases, thereby the thickness tolerance of the insert piece becomes larger. SUMMARY

[0009] The present application provides a brass alloy, which has less stamping resistance and less friction between the die during stamping, so that the thickness of the brass insert piece made of the brass alloy provided by the present application meets the tolerance requirements.

[0010] The specific embodiment of the present application provides a brass alloy, which is composed of the following mass percentages: Cu: 61.5-63.0wt%, X: 0.002-0.02wt%, Fe+Sn+Al+Pb≤0.035wt%, and the balance is Zn and unavoidable impurities other than Fe, Sn, Al, and Pb, wherein X is one or more of P, S, and Mg.

[0011] The microstructure of the brass alloy is α+β phase, wherein the volume fraction of the β phase is 9-16%, the twin crystal area fraction is 8-20%, and the total dislocation density is 6.0-8.0×10 7 mm / mm 3 .

[0012] When the Cu content is less than 61.5wt%, the proportion of brass beta phase is obviously increased, the beta phase is a hard and brittle phase, the appropriate existence of the beta phase can make the brass not easy to stick when stamping and shearing deformation, and reduce the sticking resistance between the stamping die and the blank. When the Cu content is more than 63.0wt%, with the increase of the Cu content, the proportion of the brass normal temperature structure beta phase is gradually reduced, and finally becomes a single alpha phase structure, the alpha phase has excellent plasticity at normal temperature, but the brass is easy to stick when stamping, and the sticking phenomenon is more and more serious with the progress of stamping, the sticking resistance between the stamping die and the blank is gradually increased, the stamping force actually acting on the blank is gradually reduced, and thus the thickness of the insert is gradually reduced, therefore, the Cu content provided by the present application is between 61.5-63.0wt%.

[0013] The X element provided by the present application is one or a combination of P, S and Mg, by adding an appropriate amount of X element, a dispersed hard phase is formed in the brass structure, the sticking resistance between the die and the blank is reduced, but the mass percentage of the X element should not be more than 0.02wt%, otherwise the cold deformation of the material is adversely affected.

[0014] The solubility of P in brass at room temperature provided by the present application is almost zero, when the P content is more than 0.004wt%, a small amount of brittle phase Cu3P appears in the structure, which slightly reduces the plasticity of the brass, but the existence of the Cu3P phase can improve the die sticking problem of the brass during stamping processing, and reduce the sticking resistance between the die and the blank. When the P content continues to increase, the number of Cu3P brittle phase distribution increases, and the material is easy to crack during processing, therefore, further, the mass percentage of P in the brass provided by the present application is 0.005-0.01wt%.

[0015] The solubility of S in copper at room temperature provided by the present application is almost zero, S exists in the form of dispersed particles of Cu2S in copper, which can improve the die sticking problem of the brass during stamping processing, and reduce the sticking resistance between the die and the blank. When the S content continues to increase, the number of Cu2S brittle phase distribution increases, and the material is easy to crack during processing, therefore, further, the mass percentage of S in the brass provided by the present application is 0.002-0.005wt%.

[0016] The Mg provided by the present application has a deoxidizing effect in copper, Mg and harmful impurity elements in the brass form high melting point compounds, which are distributed in the grain in a refined and dispersed state, can improve the die sticking problem of the brass during stamping processing, and reduce the sticking resistance between the die and the blank, when Mg and S are added together, the compound MgS is formed, and the improvement effect is more significant. When the Mg content is more than 0.01wt%, the fluidity of the copper liquid is poor, which affects the casting performance of the brass, therefore, further, the mass percentage of Mg in the brass provided by the present application is 0.005-0.01wt%.

[0017] The Fe, Sn, Al and Pb elements provided by the present application are impurity elements in common binary brasses, and have a great influence on the performance of the brass. The solid solubility of Fe element in the brass at normal temperature is extremely low, and the Fe particles will hinder the formation of twin crystals when the brass is annealed and recrystallized; Sn and Al affect the casting performance of the brass and the crystallization of the cast blank, and are easy to form loose cast blanks; the solubility of Pb in copper is extremely low, and Pb is distributed in the form of particles in the crystal and on the grain boundary, so that the cold deformation performance of the brass is deteriorated. Therefore, in the present application, the total of the mass percentages of the above four elements is limited to less than 0.035wt%.

[0018] Strength, hardness and elongation are macroscopic indexes for judging whether a material is suitable for stamping processing. The lower the yield strength, the higher the elongation, and the lower the hardness, the easier the material is to be deformed by stamping. However, as a power plug, it is necessary to maintain a high yield strength and hardness to prevent deformation caused by impact force during use. Therefore, further, the tensile strength of the brass alloy provided by the present application is 380-440 MPa, the yield strength is 270-330 MPa, the elongation A50 is 26-35%, and the Vickers hardness HV5 is 125-140.

[0019] However, simply adjusting the mechanical properties of the brass base material cannot solve the problem that the thickness of the plug gradually increases after the current material is stamped for a period of time. It is also necessary to regulate the microstructure of the base material.

[0020] The phase composition of the brass provided by the present application is α+β phase, wherein the volume fraction of the β phase is 9-16%, and the β phase has a fine spherical shape with an average diameter of ≤3 μm. Because the α phase has good plasticity, and the β phase is hard and brittle, if the brass structure is single α phase, copper scraps are easy to stick to the working surface of the stamping die during stamping and shearing, increasing the sticking resistance between the stamping die and the blank cutting surface. As the stamping proceeds, the actual stamping force acting on the blank gradually decreases, thereby causing the actual thickness tolerance of the plug to exceed the lower limit. The existence of the β phase improves the problem of copper scraps sticking to the die to some extent. The β phase is spheroidized, and the smaller the size, the more the number of the β phase distributed between the α phases, the more uniform the distribution, and the better the improvement effect. When the volume fraction of the β phase exceeds 16%, the hard and brittle nature of the β phase has a gradually increasing negative impact on the stamping performance of the material, such as cracking during stamping.

[0021] The proportion of twin crystals in the microstructure of the brass provided by the present application is 8-20%. Although the plastic deformation amount generated by the twin crystals is smaller than that generated by slip, the existence of the twin crystals is significant in forming a recrystallization direction. The twin crystals can determine a new slip system direction. Due to the existence of the slip system direction, the crystal is easy to slip during stamping processing, the stamping deformation resistance is reduced, and the actual stamping force acting on the material is prevented from decreasing to cause the actual thickness of the plug to exceed the tolerance range.

[0022] The total dislocation density in the brass microstructure is 6.0-8.0*10 7 mm / mm 3 The ability of metal plastic deformation depends on the dislocation density and the ability of dislocation movement in the metal, and when the dislocation density is too large, the material is difficult to be deformed by stamping, and when the dislocation density is too small, the strength of the insert is low and cannot meet the use requirement.

[0023] Further, the ratio of the movable dislocation length to the total dislocation length in the brass microstructure is not less than 90%, because the dislocations in the metal are divided into movable dislocations and fixed dislocations, the movable dislocations are naturally formed and have not interacted with other defects (such as dislocations, crystal planes and phase interfaces), the movable dislocations have good mobility and are easy to slide along the slip plane during stamping deformation, and the fixed dislocations are locked dislocations, and the fixed dislocations are formed in two ways, i.e., interaction of two dislocations or interaction of dislocations and interfaces, so that the fixed dislocations are difficult to slide along the slip plane.

[0024] The grain size of the brass is 25-40 mu m, because the grain boundary has a hindering effect on the slip movement, reducing the grain boundary area is beneficial to stamping deformation, and the smaller the grain size, the smaller the grain boundary area in unit volume, but the grain size is too small, the grain is coarse, and the surface of the material after stamping forming can appear orange peel phenomenon, therefore, the appropriate grain size is helpful to improve the problem of stamping size out-of-tolerance of the brass.

[0025] The application further provides a preparation method of the brass alloy, and the process flow of the preparation method is as follows: smelting, up-drawing continuous casting, stretching, annealing, combined drawing, surface degreasing, stress relief annealing and precision straightening.

[0026] The preparation method of the brass alloy comprises the following steps:

[0027] (1) ingredients, smelting and up-drawing continuous casting are performed according to the mass percentage of each component of the brass alloy to obtain a rod blank;

[0028] (2) the rod blank is subjected to multi-pass stretching, and in the multi-pass stretching process, medium processing rate stretching and high-temperature annealing are first performed, and then large processing rate stretching and medium-temperature annealing are performed, and skinning is performed in the multi-pass stretching process to remove surface casting defects to obtain a soft state wire blank;

[0029] In the method, the processing rate of the medium processing rate stretching is 20-35%, and the processing rate of the large processing rate stretching is 60-70%.

[0030] (3) the soft state wire blank is subjected to combined drawing, surface degreasing, stress relief annealing and precision straightening in sequence to obtain a brass alloy rod.

[0031] The present application firstly carries out 20-35% medium processing rate stretching, since the microstructure of the up-drawing continuous casting rod blank is composed of developed dendrites, the arrangement of each dendrite is irregular, there are low melting point eutectic structure, inclusions, pores, shrinkage and hot cracks between the dendrites, the combination between the dendrites is not strong, if more than 50% large processing rate stretching is adopted, micro cracks are easily generated at the weak position between the dendrites, the micro cracks cannot be healed in the subsequent processing, and cracks are generated in the stamping deformation. If the processing rate is too small, the deformation is concentrated on the surface layer, the center layer is not deformed or is deformed small, the center part of the rod blank retains part of the as-cast structure after annealing, leading to uneven grain size of the annealing recrystallization; subsequently, 60-70% large processing rate stretching is adopted, the purpose is to fully break the original grains, the number of recrystallization nucleation is significantly increased, the recrystallization grain size formed through the medium temperature annealing is uniform, and the annealing after the large processing rate deformation can form twin crystals, if the processing rate of the large processing rate stretching is less than 60%, the original grains are not enough to be destroyed, the new grains and the original grains coexist after annealing, the uniformity of the structure is poor, and the twin crystals are not easy to form.

[0032] The annealing temperature of the high temperature annealing after the medium processing rate stretching provided by the present application is 560-620℃, the purpose is to form completely distortion-free equiaxed grains through high temperature, the fixed dislocation generated in the medium processing rate stretching deformation is completely eliminated, clear grain boundaries are obtained, further, the heating time of the high temperature annealing is 0.5-2h, the holding time is 2-5h, and the cooling time is 2-4h; the medium temperature annealing (bottom leaving annealing) after the large processing rate stretching adopts the temperature annealing which is beneficial to improve the structure, the annealing temperature is 480-520℃, the purpose of controlling the large processing rate stretching and the medium temperature annealing is to obtain the required grain size and the volume fraction of the beta phase, further, the heating time of the medium temperature annealing is 0.5-1.5h, the holding time is 2-5h, and the cooling time is 2-4h.

[0033] Further, in step (1), the raw material after batching is subjected to smelting, and the process parameters of the smelting are as follows: the smelting temperature is 950-1100℃, and the holding time is 1030-1070℃.

[0034] The specific steps of smelting the raw material after batching are as follows: smelting is carried out in a power frequency continuous furnace, after the raw material is melted, the copper liquid flows into the holding furnace through the dark ladle, the smelting temperature is 950-1100℃, the temperature of the holding furnace is 1030-1070℃, and the temperature is also the casting temperature.

[0035] Further, in step (1), the process parameters of the up-drawing continuous casting are as follows: the rod blank specification is Φ8-16mm, the drawing speed is 0.8-2.0m / min, the drawing pitch is 2-8mm, the reverse retreat pitch is 0.1-2mm, and the take-up mode is disc winding.

[0036] Further, in step (2), the amount of skinning of the rod blank in the multi-pass stretching process is 0.010-0.30 mm. If the amount of skinning is too large, the rod blank surface is prone to metal spalling; if the amount of skinning is too small, the rod blank surface defects cannot be eliminated. Further preferably, the skinning is performed after the intermediate processing rate stretching or high-temperature annealing, or after the high processing rate stretching or medium-temperature annealing.

[0037] Further, in step (2), the multi-pass stretching is two-pass stretching, the processing rate of the first-pass stretching is 20-35%, the high-temperature annealing parameters after the first-pass stretching are: the annealing temperature is 560-620°C, the heating time is 0.5-2 h, the holding time is 2-5 h, and the cooling time is 2-4 h, the processing rate of the second-pass stretching is 60-70%, and the medium-temperature annealing parameters after the second-pass stretching are: the annealing temperature is 480-520°C, the heating time is 0.5-1.5 h, the holding time is 2-5 h, and the cooling time is 2-4 h.

[0038] Further, in step (2), the gas atmosphere during the high-temperature annealing or medium-temperature annealing is N2 or a mixture of N2 and H2.

[0039] Further, in step (2), the rod blank is subjected to pickling after the high-temperature annealing or medium-temperature annealing, and the pickling method comprises: the pickling solution is a mixture of H2SO4 and H2O2, the mass concentration of H2SO4 is 20-30%, the rod blank is rinsed with water after pickling, and the residual acid on the surface of the soft rod blank is neutralized with a saponification solution. After neutral gas protection annealing, there is still slight oxidation on the surface of the soft rod blank, and the surface oxidation scale needs to be removed by pickling.

[0040] Further, in step (3), the soft rod blank is subjected to combined drawing, which comprises: the soft rod blank is drawn, straightened, polished, flattened, and cut to a length of 2-3 m long on a combined drawing machine set, and the straightness is not more than 0.2 mm / m.

[0041] Further, in step (3), the total processing rate of the combined drawing is 7-15%. If the total processing rate of the combined drawing is less than 7%, the dislocation density is difficult to reach 6.0×10 7 mm / mm 3 , the material strength and hardness are low, the chip breaking effect is poor, and the processed parts are prone to deformation under stress; if the total processing rate of the combined drawing exceeds 15%, the dislocation density is very likely to exceed 8.0×10 7 mm / mm 3 , and the parts are prone to cracking during cold deformation processing.

[0042] Further, in step (3), the rod after combined drawing is subjected to surface degreasing, and the process parameters of the surface degreasing are as follows: the degreasing solution is NaOH solution, the concentration is 2-6wt%, and 0.2-0.6wt% antioxidant C6H5N3 is added, the degreasing solution temperature is 30-50℃, and the ultrasonic frequency is 25-110KHZ. The rod after combined drawing is attached with a layer of lubricating oil, and needs to be subjected to degreasing treatment, otherwise the surface lubricating oil is carbonized under heating during stress relieving in the next process, and black spots appear on the surface of the rod.

[0043] Further, in step (3), the rod after surface degreasing is subjected to stress relieving annealing, and the process parameters of the stress relieving annealing are as follows: the annealing temperature is 230-300℃, the time for increasing from room temperature to the temperature is controlled to be 0.5-2h, and the holding time is 2-6h. The purpose of the stress relieving annealing is to further eliminate the residual stress unevenly distributed in the rod, because straightening only changes the surface tensile stress of the rod into compressive stress, and cannot eliminate the residual stress. The stress relieving annealing must be protected by a reducing gas to avoid oxidation of the surface of the rod.

[0044] Further, a protective gas is input during the stress relieving annealing, the protective gas is a mixed gas of H2 and N2, the volume percentage of H2 is ≥75%, and the volume percentage of O2 is ≤1ppm. The surface of the wire is prevented from being oxidized by the reduction effect of the high-hydrogen atmosphere. The temperature range of the stress relieving annealing is 230-300℃, the temperature increasing time is 0.5-2h, the holding time is 2-4h, the protective gas flow in the temperature increasing section is 11-16m 3 / h, the protective gas flow in the holding section is 12-15m 3 / h, and the protective gas pressure is 65-80mbar.

[0045] After the rod subjected to combined drawing is subjected to stress relieving annealing, the internal stress is completely released, the straightness of the rod changes, and the rod after stress relieving annealing needs to be subjected to fine straightening. The fine straightening is performed on a polishing straightening machine of a combined drawing unit, and the straightness of the rod after polishing straightening should be not more than 0.2mm / m.

[0046] The preparation method of the brass alloy also includes finished product inspection and packaging.

[0047] The application also provides application of the brass alloy to stamping power supply plug pieces.

[0048] Compared with the prior art, the application has the following beneficial effects:

[0049] The present application forms a dispersed brittle phase by adding P, S, Mg trace elements into brass, and forms a proper amount of beta phase by controlling the content of Cu, so that the brass alloy reduces the adhesion resistance between the die during stamping process; the present application controls the twin area fraction and total dislocation density in the brass structure, so as to reduce the stamping deformation resistance during stamping of the brass alloy, and solves the problem that the size of the brass bar produced by the current process method is easy to be out of tolerance during stamping of the power plug, so that the thickness deviation of the plug is kept within ±0.015mm after stamping of the brass bar for 1h. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 The microstructure photo of the brass bar prepared in Example 1 of the present application;

[0051] Figure 2 The microstructure photo of the brass bar provided in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0052] The present application is further described in detail below with reference to the embodiments and the accompanying drawings.

[0053] The present application provides five examples and six comparative examples, and the specific components are shown in Table 1.

[0054] Example 1

[0055] A specification of The preparation method of the brass bar for stamping power plug is as follows:

[0056] 1) Melting: according to the required composition of the alloy, the alloy is melted in a frequency-connected furnace, the melting temperature is 980-1070℃, the holding temperature is 1040-1050℃, and this temperature is also the casting temperature.

[0057] 2) Up-drawing continuous casting: the bar blank specification is Φ10mm, the drawing speed is 1.65m / min, the drawing pitch is 4mm, and the reverse retreat pitch is 0.5mm.

[0058] 3) Stretching: the Φ10mm bar blank is first stretched to Φ8.2mm through skinning, and the skinning amount is 0.022mm, and the processing rate is 32.8%; the Φ8.2mm after annealing is stretched to Φ4.8mm through the second stretching, and the processing rate is 65.7%.

[0059] 4) Annealing: The first annealing process after the first drawing: annealing temperature is 580°C, heating time is 1 h, holding time is 3.5 h, cooling time is 2.5 h; the second annealing process after the second drawing: annealing temperature is 510°C, heating time is 1 h, holding time is 3 h, cooling time is 2.5 h. Both of the annealing processes are under N2 protection. The wire blanks after annealing are pickled in a mixed solution of H2SO4 and H2O2, the mass concentration of H2SO4 is 23.7%, and the soft wire blanks are rinsed with clean water after pickling, and the residual acid on the surface of the soft wire blanks is neutralized in a saponification solution.

[0060] 5) Combined drawing: the Φ4.8 soft wire blanks after pickling are drawn, straightened, polished, flattened, and cut to size on a combined drawing machine set to produce Φ4.55 mm x 2500 mm rods, the straightness is 0.12 mm / m, and the total drawing processing rate is 10.1%.

[0061] 6) Surface degreasing: the rods are degreased on an ultrasonic cleaning machine set, the degreasing solution concentration is 3.8 wt%, the antioxidant C6H5N3 concentration is 0.31 wt%, the degreasing solution temperature is 42°C, and the ultrasonic frequency is 55 KHZ.

[0062] 7) Stress relief annealing: annealing temperature is 270°C, heating time is 0.5 h, holding time is 4 h, H2 and N2 mixed gas is used as protective gas, the volume ratio of H2 is 75%, the volume ratio of O2 is 0.22 ppm, the protective gas flow rate in the heating section is 13 m 3 / h, the protective gas flow rate in the holding section is 14 m 3 / h, and the protective gas pressure is 70 mbar.

[0063] 8) Precision straightening: precision straightening is performed on a combined drawing machine, and the straightness of the rods after straightening is 0.10 mm / m.

[0064] 9) Finished product inspection and packaging. As shown in Figure 1 the β phase morphology is fine spherical, the average diameter is 2.5 μm, which is less than 3 μm, and the volume fraction of β phase is 11.57%, which is within the range of 9-16%.

[0065] Example 2

[0066] A specification for a brass rod for stamping power plug is as follows: The preparation method of the brass rod is as follows:

[0067] 1) Melting: according to the required alloy composition, melting is carried out in a power frequency connected furnace, the melting temperature is 990-1060°C, and the holding temperature is 1045-1060°C, which is also the casting temperature.

[0068] 2) Up-drawing continuous casting: the billet specification is Φ16 mm, the drawing speed is 1.30 m / min, the drawing pitch is 3.5 mm, and the reverse pitch is 1.2 mm.

[0069] 3) Stretching: the Φ16 mm billet is first stretched to Φ13 mm with a processing rate of 34%; the Φ13 mm after annealing is secondly stretched to Φ8 mm with a processing rate of 62.1% after skinning.

[0070] 4) Annealing: the annealing process after the first stretching is as follows: the annealing temperature is 620 ℃, the heating time is 1.5 h, the holding time is 3 h, and the cooling time is 3 h; the annealing process after the second stretching is as follows: the annealing temperature is 520 ℃, the heating time is 1.5 h, the holding time is 3.5 h, and the cooling time is 3 h. Both of the two annealings are N2+H2 protective annealing, and the wire billet after annealing does not need to be pickled to obtain Φ8 soft wire billet.

[0071] 5) Combined drawing: the Φ8 soft wire billet is drawn, straightened, polished, flattened, and cut to size on a combined drawing machine set to obtain a rod with a size of Φ7.42 mm x 2500 mm, a straightness of 0.18 mm / m, and a total drawing processing rate of 14%.

[0072] 6) Surface degreasing: the rod is degreased on an ultrasonic cleaning machine set, the degreasing solution concentration is 2.9 wt%, the antioxidant C6H5N3 concentration is 0.27 wt%, the degreasing solution temperature is 45 ℃, and the ultrasonic frequency is 70 KHZ.

[0073] 7) Stress relief annealing: the annealing temperature is 300 ℃, the heating time is 1 h, the holding time is 3 h, H2 and N2 mixed gas is used as the protective gas, the H2 volume ratio is 85%, the O2 volume ratio is 0.45 ppm, the protective gas flow rate in the heating section is 12 m 3 / h, the protective gas flow rate in the holding section is 15 m 3 / h, and the protective gas pressure is 64 mbar.

[0074] 8) Precision straightening: the precision straightening is performed on a combined drawing machine, and the straightness of the rod after straightening is 0.15 mm / m.

[0075] 9) Finished product inspection and packaging.

[0076] Example 3

[0077] A kind of specification is The preparation method of the brass rod for stamping power plug is as follows:

[0078] 1) Melting: The alloy was charged according to the required composition and melted in a frequency-continuous furnace. The melting temperature was 1000-1060 °C, and the holding temperature was 1050-1060 °C, which was also the casting temperature.

[0079] 2) Up-drawing continuous casting: The rod blank had a specification of Φ8.5 mm, the drawing speed was 1.7 m / min, the drawing pitch was 4 mm, and the reverse pitch was 0.5 mm.

[0080] 3) Stretching: The Φ8 mm rod blank was first stretched to Φ6.9 mm after skinning, with a skinning amount of 0.012 mm and a processing rate of 25.6%; the Φ6.8 mm after annealing was then stretched to Φ4.3 mm after the second skinning, with a processing rate of 61.1%.

[0081] 4) Annealing: The annealing process after the first stretching had an annealing temperature of 560 °C, a heating time of 1 h, a holding time of 3.5 h, and a cooling time of 3 h; the annealing process after the second stretching had an annealing temperature of 480 °C, a heating time of 1 h, a holding time of 4 h, and a cooling time of 3 h. Both annealings were carried out under N2 protection, and the wire blank after annealing was pickled in a mixed solution of H2SO4 and H2O2, with a mass concentration of H2SO4 being 25.5%. After pickling, the soft wire blank was rinsed with clean water, and the residual acid on the surface of the soft wire blank was neutralized in a saponification solution.

[0082] 5) Combined drawing: The Φ4.3 soft wire blank after pickling was drawn, straightened, polished, flattened, and cut to size on a combined drawing machine to form a rod with a size of Φ4 mm x 2500 mm, a straightness of 0.1 mm / m, and a total drawing processing rate of 13.5%.

[0083] 6) Surface degreasing: The rod was degreased on an ultrasonic cleaning machine, with a degreasing solution concentration of 2.2 wt%, an antioxidant C6H5N3 concentration of 0.21 wt%, a degreasing solution temperature of 35 °C, and an ultrasonic frequency of 80 KHZ.

[0084] 7) Stress relief annealing: The annealing temperature was 250 °C, the heating time was 0.5 h, the holding time was 3.5 h, a mixed gas of H2 and N2 was used as the protective gas, the volume ratio of H2 was 75%, the volume ratio of O2 was 0.6 ppm, the protective gas flow rate at the heating stage was 13.6 m 3 / h, the protective gas flow rate at the holding stage was 12.9 m 3 / h, and the protective gas pressure was 60 mbar.

[0085] 8) Precision straightening: The precision straightening was carried out on a combined drawing machine, and the straightness of the rod after straightening was 0.10 mm / m.

[0086] 9) Finished product inspection and packaging.

[0087] Example 4

[0088] A specification is The preparation method of the brass bar for stamping power plug is as follows:

[0089] 1) Melting: according to the required composition of the alloy, the alloy is melted in a power frequency connected furnace, the melting temperature is 1010-1060℃, the holding temperature is 1045-1060℃, which is also the casting temperature.

[0090] 2) Up-drawing continuous casting: the bar blank specification is Φ12mm, the drawing speed is 1.55m / min, the drawing pitch is 3.8mm, and the reverse retreat pitch is 0.8mm.

[0091] 3) Stretching: the Φ12mm bar blank is stretched to Φ10mm in the first stretching, and the processing rate is 30.5%; the Φ10mm after annealing is stretched to Φ5.9mm in the second stretching, the skinning amount is 0.020mm, and the processing rate is 65.2%.

[0092] 4) Annealing: the annealing process after the first stretching is that the annealing temperature is 600℃, the heating time is 1.5h, the holding time is 2.5h, and the cooling time is 3h; the annealing process after the second stretching is that the annealing temperature is 490℃, the heating time is 1h, the holding time is 4h, and the cooling time is 3h. Both of the two annealings are N2 protection annealing, the wire blank after annealing is pickled in a mixed solution of H2SO4 and H2O2, the mass concentration of H2SO4 is 28%, after pickling, the soft wire blank is washed with clean water, and the residual acid on the surface of the soft wire blank is neutralized in the saponification solution.

[0093] 5) Combined drawing: the Φ5.9 soft wire blank after pickling is drawn, straightened, polished, flat-headed, and sawed to a size of Φ5.64mm×2500mm long on the combined drawing machine set, the straightness is 0.14mm / m, and the total drawing processing rate is 8.6%.

[0094] 6) Surface degreasing: the bar is degreased on the ultrasonic cleaning machine set, the degreasing solution concentration is 4.3wt%, the antioxidant C6H5N3 concentration is 0.27wt%, the degreasing solution temperature is 33℃, and the ultrasonic frequency is 60KHZ.

[0095] 7) Stress relief annealing: the annealing temperature is 280℃, the heating time is 0.5h, the holding time is 3h, the mixed gas of H2 and N2 is used as the protective gas, the volume ratio of H2 is 95%, the volume ratio of O2 is 0.44ppm, the protective gas flow rate in the heating section is 13m 3 / h, the protective gas flow rate in the holding section is 16m 3 / h, and the protective gas pressure is 60mbar.

[0096] 8) Straightening: Straightening is carried out on the combined drawing machine, and the straightness of the straightened bar is 0.12 mm / m.

[0097] 9) Product inspection and packaging.

[0098] Example 5

[0099] The specification of the brass bar for stamping power tabs is The preparation method of the brass bar for stamping power tabs is as follows:

[0100] 1) Melting: The alloy is charged according to the required composition, and the melting is carried out in a power frequency connected furnace. The melting temperature of the melting furnace is 980-1060℃, and the holding temperature of the holding furnace is 1045-1055℃, which is also the casting temperature.

[0101] 2) Up-drawing continuous casting: The rod blank specification is Φ14mm, the drawing speed is 1.40m / min, the drawing pitch is 3mm, and the reverse retreat pitch is 1mm.

[0102] 3) Stretching: The Φ14mm rod blank is first stretched to Φ12mm through skinning and stretching, and the skinning amount is 0.025mm, and the processing rate is 26.5%; the Φ12mm after annealing is stretched to Φ7mm through the second stretching, and the processing rate is 66%.

[0103] 4) Annealing: The annealing process after the first stretching: the annealing temperature is 610℃, the heating time is 2h, the holding time is 2.5h, and the cooling time is 2h; the annealing process after the second stretching: the annealing temperature is 500℃, the heating time is 1h, the holding time is 3h, and the cooling time is 3.5h. Both of the two annealings are N2+H2 protective annealing, and the wire blank after annealing does not need to be pickled.

[0104] 5) Combined drawing: The Φ7 soft state wire blank is drawn, straightened, polished, flat headed, and sawed to a size of Φ6.60mm×2500mm on the combined drawing machine, the straightness is 0.16mm / m, and the total drawing processing rate is 11.1%.

[0105] 6) Surface degreasing: The bar is degreased on the ultrasonic cleaning machine, the degreasing solution concentration is 2.4wt%, the antioxidant C6H5N3 concentration is 0.52wt%, the degreasing solution temperature is 47℃, and the ultrasonic frequency is 30KHZ.

[0106] 7) Stress relief annealing: The annealing temperature is 230℃, the heating time is 0.5h, the holding time is 6h, and the mixed gas of H2 and N2 is used as the protective gas, the volume ratio of H2 is 75%, the volume ratio of O2 is 0.16ppm, the protective gas flow at the heating stage is 11m 3 / h, the protective gas flow at the holding stage is 12m 3 / h, and the protective gas pressure is 70mbar.

[0107] 8) Straightening: Straightening is carried out on a combined drawing machine, and the straightness of the straightened bar is 0.15 mm / m.

[0108] 9) Product inspection and packaging.

[0109] Comparative Example 1

[0110] Commercially available H62 brass Φ4.55 mm x 2500 mm bar was used to compare the effect of the thickness change of the punched power plug on the bar of Example 1 during the punching process, as shown in Table 1. Figure 2 As shown in Table 1, although the β phase morphology is also fine spherical with an average diameter of 2.2 μm, which is less than 3 μm, the β phase volume fraction is only 4.32%, which is lower than 9%, which is not conducive to improving the problem of copper scrap sticking to the mold.

[0111] Comparative Example 2

[0112] No Mg, P and S elements were added, and the rest was the same as Example 1, which was to compare the effect of the thickness change of the punched power plug on the bar of Example 1 during the punching process after adding trace amounts of Mg, P and S elements.

[0113] Comparative Example 3

[0114] When the content of Fe+Sn+Al+Pb in the brass is greater than 0.035wt%, the rest is the same as Example 1, which is to compare the effect of the thickness change of the punched power plug on the bar of Example 1 during the punching process after the total content of Fe, Sn, Al and Pb exceeds the limit.

[0115] Comparative Example 4

[0116] The first pass was stretched with a large processing rate of 60%, and the second pass was stretched with a medium processing rate of 30%, and the rest was the same as Example 1, which was to compare the effect of the thickness change of the punched power plug on the bar of Example 1 during the punching process after the distribution of the processing rate of the second pass.

[0117] Comparative Example 5

[0118] The annealing temperature after the first pass was 490°C, and the annealing temperature after the second pass was 580°C, and the rest was the same as Example 1, which was to compare the effect of the thickness change of the punched power plug on the bar of Example 1 during the punching process after the recrystallization annealing temperature.

[0119] Comparative Example 6

[0120] The bar of the combined drawing was not stress relieved, and the rest was the same as Example 1, which was to compare the effect of the thickness change of the punched power plug on the bar of Example 1 during the punching process after the stress relief annealing treatment of the finished product.

[0121] Performance analysis:

[0122] The microstructure of the five examples and six comparative examples was detected, and the results are recorded in Table 2.

[0123] Phase and twin area ratio, size, number: observed using an electron microscope (SEM).

[0124] Grain size: The metallographic sample was prepared according to GB / T 13298, and the grain size was measured according to the comparison method specified in GB / T6394-2017 (Metal Average Grain Size Determination Method), i.e., by comparing with the standard rating chart to evaluate the grain size.

[0125] Dislocation density: observed using an X-ray diffractometer.

[0126] The following performance tests were conducted on the five examples and six comparative examples, and the results are recorded in Table 3.

[0127] Tensile strength, yield strength Rp0.2 and elongation: detected according to GB / T228.1-2021 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method".

[0128] Hardness HV5: detected according to GB / T4340.1-2009 "Metallic Materials Vickers Hardness Test Part 1: Test Method".

[0129] Insert thickness: measured by digital micrometer, and the results are recorded in Table 4.

[0130] From Table 4, it can be seen that:

[0131] 1) Comparative Example 1 is a commercially available H62 Φ4.55mm x 2500mm bar, although the mechanical properties also meet the requirements, but after stamping for 5min, the insert thickness deviation value reaches +0.017mm, and after stamping for 30min, the insert thickness deviation value has reached +0.028mm, exceeding the specified range of ±0.015mm, indicating that even if the mechanical properties of the bar meet the requirements, it cannot guarantee that the insert thickness change value meets the specified requirements during stamping.

[0132] 2) Comparative Example 2 does not add Mg, P and S elements, from Table 2, the β phase volume fraction is in the range of 9-16%, the β phase size is ≤3μm, the grain size is in the range of 25-40μm, the twin area fraction is in the range of 8-20%, the dislocation density is lower than the lower limit 6.0x10 7 mm / mm 3 , and the mobile dislocation length ratio is less than 90%, after stamping for 5min, the insert thickness deviation value is +0.009mm, which meets the specified requirements, but after stamping for 30min, the insert thickness deviation value reaches +0.018mm, exceeding the specified range of ±0.015mm, indicating that Mg, P and S elements have an impact on the change of the insert thickness during stamping.

[0133] 3) Comparative Example 3 The sum of Fe+Sn+Al+Pb content in the brass reaches 0.1212%, which exceeds 0.035wt%, the volume fraction of β phase exceeds the upper limit of 16%, the size of β phase exceeds 3μm, the grain size is lower than 25μm, the twin area fraction is lower than 8%, the dislocation density exceeds the upper limit of 8.0×1010mm / mm 7 mm / mm 3 The ratio of mobile dislocation length is lower than 90%, after stamping for 5min, the thickness deviation of the plug is +0.014mm, which meets the requirement, but after stamping for 30min, the thickness deviation of the plug reaches +0.025mm, which exceeds the range of ±0.015mm, which shows that the Fe+Sn+Al+Pb content has an effect on the microstructure, and further has an effect on the thickness change of the plug during stamping.

[0134] 4) Comparative Example 4 The stretching process provided in Comparative Example 4 is opposite to that of Example 1, the first pass adopts 60% large processing rate stretching, and the second pass adopts 30% medium processing rate stretching, the grain size exceeds the upper limit of 40μm, the twin area fraction is reduced to only 0.9%, which is lower than the lower limit of 8%, and the dislocation density is lower than the lower limit of 6.0×1010mm / mm 7 mm / mm 3 The ratio of mobile dislocation length is far lower than 90%, after stamping for 5min, the thickness deviation of the plug is +0.013mm, which meets the requirement, but after stamping for 30min, the thickness deviation of the plug reaches +0.028mm, which exceeds the range of ±0.015mm, which shows that the distribution of the processing rate of the second pass stretching has a significant effect on the thickness change of the plug during stamping of the brass bar into the power plug.

[0135] 5) Comparative Example 5 The annealing process after stretching provided in Comparative Example 5 is opposite to that of Example 1, the annealing temperature after the first pass stretching is 490℃, and the annealing temperature after the second pass stretching is 580℃, the volume fraction of β phase exceeds the upper limit of 16%, the size of β phase exceeds 3μm, the grain size is coarse, which exceeds the upper limit of 40μm and reaches 60μm, the twin area fraction is out of the range of 8-20%, and the dislocation density is lower than the lower limit of 6.0×1010mm / mm 7 mm / mm 3 The ratio of mobile dislocation length is lower than 90%, after stamping for 5min, the thickness deviation of the plug is +0.015mm, which meets the requirement, but after stamping for 30min, the thickness deviation of the plug reaches +0.030mm, which exceeds the range of ±0.015mm, which shows that the recrystallization annealing temperature has a significant effect on the thickness change of the plug during stamping of the brass bar into the power plug.

[0136] 6) Comparative Example 6 bar was not stress relieved, the volume fraction of beta phase was in the range of 9-16%, the size of beta phase was <3 μm, the grain size was in the range of 25-40 μm, the area fraction of twin was in the range of 8-20%, but the dislocation density was slightly beyond the upper limit 8.0 x 10 7 mm / mm 3 , the movable dislocation length accounted for less than 90%, after stamping for 5 min, the thickness deviation of the insert was +0.012 mm, which met the specified requirements, but after stamping for 30 min, the thickness deviation of the insert reached the upper limit +0.015 mm, but after stamping for 60 min, the thickness deviation of the insert was +0.017 mm, which exceeded the specified range of ±0.015 mm, indicating that the stress relief annealing treatment of the finished product had an impact on the thickness change of the stamped insert.

[0137] Table 1 Chemical composition of Example 1-5 and Comparative Example 1-6

[0138]

[0139] Table 2 Microstructure test data of Example 1-5 and Comparative Example 1-6

[0140]

[0141] Table 3 Mechanical properties and thickness deviation of stamped insert of Example 1-5 and Comparative Example 1-6

[0142]

[0143] Table 4 Thickness deviation of stamped insert of Example 1-5 and Comparative Example 1-6

[0144]

Claims

1. A brass alloy characterized in that, The brass alloy consists of the following mass percentages, Cu: 61.5-63.0wt%, X: 0.002-0.02wt%, Fe+Sn+Al+Pb≤0.035wt%, the balance being Zn and inevitable impurities other than Fe, Sn, Al, Pb, wherein X is one or more of P, S, Mg; The brass alloy has an α+β phase structure, wherein the volume fraction of the β phase is 9-16%, the twin area fraction is 8-20%, and the total dislocation density is 6.0-8.0×10 7 mm / mm 3 ; The mass percentage of Mg is 0.005-0.01wt%.

2. The brass alloy according to claim 1, characterized in that, The mass percentage of P is 0.005-0.01wt%.

3. The brass alloy of claim 1, wherein The mass percentage of S is 0.002-0.005wt%.

4. The brass alloy of claim 1, wherein The proportion of the mobile dislocation length to the total dislocation length in the brass alloy structure is not less than 90%.

5. The brass alloy of claim 1, wherein The grain size of the brass alloy is 25-40μm.

6. A method of producing the brass alloy according to any one of claims 1 to 5, characterized by, Comprising: (1) ingredient, smelting and up-casting according to the mass percentages of each component of the brass alloy as claimed in any one of claims 1-5 to obtain a rod blank; (2) multi-pass stretching of the rod blank, in which moderate processing rate stretching and high temperature annealing are performed first, followed by high processing rate stretching and medium temperature annealing, and skinning is performed during the multi-pass stretching to remove surface casting defects to obtain a soft wire blank; wherein the processing rate of the moderate processing rate stretching is 20-35%, and the processing rate of the high processing rate stretching is 60-70%; (3) joint drawing, surface degreasing, stress relief annealing and precision straightening of the soft wire blank in sequence to obtain a brass alloy rod; In step (2), the annealing temperature of the high temperature annealing is 560-620℃, and the annealing temperature of the medium temperature annealing is 480-520℃.

7. The method of producing a brass alloy according to claim 6, characterized by, In step (3), the total processing rate of the joint drawing is 7-15%.

8. Application of the brass alloy as claimed in any one of claims 1-5 to a stamped power plug.

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