JP4718273B2 - Reinforced α brass and method for producing the same - Google Patents

Description

  The present invention relates to a reinforced α brass material excellent in yield strength and bending workability and balanced in yield strength and bending workability, and a method for producing the same.

  Conventionally, brass materials have a relatively high mechanical strength, a relatively good electrical conductivity, and are inexpensive, and thus are frequently used for electronic parts such as terminals and connectors, and mechanical parts.

  However, the conventional brass material has a drawback that when it is attempted to obtain a material having higher strength by increasing the processing rate, the bending workability is poor and the toughness becomes poor, so that the bending process becomes difficult. That is, when processing into a connector or the like, severe bending is often applied, and the use of one having a proof stress of less than 550 MPa is dominant so that defects are not easily generated by the required bending. . And when high intensity | strength exceeding this level is required, it is normal to selectively use expensive phosphor bronze. In addition, the conventional brass material does not exhibit the characteristics that can be said to be remarkably excellent in the stress relaxation characteristics, but particularly when the crystal grains are made finer, this further deteriorates and becomes a serious problem in practical use. Has been requested.

  On the other hand, the processing method of the sheet made of α brass is generally cold rolling, continuous annealing pickling, cold rolling to a thickness that can be passed through a continuous annealing process after casting, hot rolling, and face cutting. It cut | disconnects through the process of continuous annealing pickling and cold rolling, and is set as a strip. In this step, annealing and rolling may be repeated depending on the thickness, annealing may be performed in a batch manner, and the last rolling may be omitted if dulling is desired, and various manufacturing processes may be considered. Such a conventional manufacturing process is hereinafter simply referred to as “general manufacturing process”.

  In the case of a continuous method, the annealing conditions of the general manufacturing process are performed within a range of 850 to 480 ° C. as disclosed in Patent Document 1. In the case of the batch method, as described in Non-Patent Document 1, it is performed at 425 ° C. to 600 ° C. Furthermore, in order to obtain a sufficient recrystallization structure and lower the rolling pressure in the first and intermediate annealing, the grain size is generally 20 μm to 35 μm. In this case, the Vickers hardness is 60 Hv to 80 Hv. . In the final annealing, the crystal grain size is generally 5 μm to 60 μm depending on the application, and the Vickers hardness is 50 Hv to 120 Hv. As described above, in the general manufacturing process, after the final annealing, it is cut after passing through the final rolling step. In the following, the material that has undergone this final rolling step is referred to as “general material”.

  Considering a general alloy strengthening method, when trying to improve the strength of the α brass strip, it is possible to adopt a strengthening method such as strengthening by refining crystal grains or solid solution strengthening using alloy elements. It is common.

  As disclosed in Japanese Patent Application Laid-Open No. 2004-228620, there is a method for increasing the strength of α brass by adding an alloy element such as Sn, as disclosed in Patent Document 2. However, the use of alloy elements increases the cost depending on the alloy components used, which may impede scrap recyclability and may affect productivity. Therefore, it is preferable to try to refine crystal grains without changing the alloy composition of brass.

  Non-Patent Document 2 and Non-Patent Document 3 have published research results of performing crystal grain refinement without changing the composition. In this case, a high rolling rate such as 92%, 91%, 80%, and 78% is adopted, and the subsequent annealing is 300 ° C. × 1 hour, 270 ° C. × 7 hours, 230 ° C. × 17 hours. Annealing for a long time in the low temperature range. The strength obtained is as follows: after annealing, the yield strength at 300 ° C. × 1 hour is 379 MPa, the yield strength at 270 ° C. × 7 hours is 399 MPa, and the yield strength at 230 ° C. × 17 hours is 534 MPa. Has been reported to have a relatively high strength.

  Patent Document 3 describes a method for obtaining fine particles, and reports high tensile strength and good bendability in Examples. However, there is no mention of stress relaxation properties here, and it is described that recrystallization annealing is performed by a continuous annealing method, but in the corresponding examples, an example of a crystal grain size of 1.8 μm is disclosed.

  Furthermore, regarding α + β brass, Non-Patent Document 4 reports a study result of increasing strength by refining crystal grains. Here, fine crystals with a two-phase mixed structure of α phase and β phase are obtained by strong processing and long-term annealing at a relatively low temperature, and when this is further processed and annealed at low temperature, high strength and bending workability are obtained. It has been reported that relatively good materials can be obtained. In addition, it has been reported that the stress relaxation property deteriorates with the refinement of crystal grains, and a slight improvement is observed by low temperature annealing.

JP-A-53-32819 Japanese Patent Laid-Open No. 11-264039 JP 2004-292875 A Published by Japan Copper and Brass Association Data book of copper products p. 19 Copper and copper alloy 41, 1, 29 Copper and copper alloys 43, 1, 21 Journal of copper technology research 39,1,128 Published by Japan Copper and Brass Association Data book of copper products p. 226

  However, in the inventions disclosed in Non-Patent Document 2 and Non-Patent Document 3, considering the case of annealing at 230 ° C. × 17 hours that showed the most excellent proof stress, from the state of work hardening by cold work, It is brought to a state where it cannot be fully softened by annealing, and the annealing is stopped to improve the bending workability and obtain a relatively high strength. Since the crystal structure obtained at this time has a non-uniform recrystallized state, the yield strength is reduced to about 534 MPa, and it can be determined that it is insufficient.

  On the other hand, Patent Document 3 suggests a preferable example of a method for producing brass having an excellent balance between strength and bendability. However, there is only one example where the balance between concrete strength and bendability can be considered, and the bendability is evaluated under severe bending workability conditions such as adopting a bend direction (Good Way) advantageous for bending. It does not show good bending workability at (Bad Way). There is no mention of stress relaxation.

  In the case of α + β brass, even if it has fine crystal grains consisting of a two-phase mixed structure of α phase and β phase, the balance between the yield strength and bending workability of phosphor bronze is far below. Therefore, it is not possible to correspond to the formula 5 below.

  In view of the above, an object of the present invention is to provide a brass material having yield strength and bending workability comparable to phosphor bronze. Moreover, the brass material according to the present invention is characterized in that the stress relaxation characteristics are not deteriorated even when a proof stress equal to that of phosphor bronze and good bending workability are imparted by forming a fine grain structure. Moreover, in order to provide the brass which concerns on this invention, the suitable process annealing method is provided.

(Α brass according to the present invention)
The α brass according to the present invention provides brass with excellent strength and bending workability by adding ingenuity to the processing method without adding other than copper and zinc.

The α brass according to the present invention is a reinforced α brass composed of 82% to 62% by weight of copper and the balance zinc and inevitable impurities, and 0.2% proof stress is 540 MPa to 800 MPa, and the rolling direction is the bending axis. The minimum bending radius (MBR) at which cracks do not occur in right-angle bending, the plate thickness (t), and the 0.2% proof stress (σ _0.2 ) satisfy the following relationship: It is. However, when the value of MBR / t is 0.3 or less, it is regarded as 0.3.

Next, in reinforced α brass composed of 82 wt% to 62 wt% of copper according to the present invention, the balance zinc and inevitable impurities, the 0.2% proof stress is 590 MPa to 800 MPa, and the right angle with the rolling direction as the bending axis. The minimum bending radius (MBR) at which no crack is generated by bending, the plate thickness (t), and the 0.2% proof stress (σ _0.2 ) satisfy the following relationship: More preferably.

  In addition, the crystal structure of the reinforced α brass described above includes grains in which processing strain remains strongly (high dislocation density grains having a most frequent grain size of 1 to 2 μm) and a structure in which strain reorganization occurs ( It is characterized by taking a mixed microstructure of reorganized dislocation grains (cellular structure) having the most frequent particle size of 0.2 to 1.5 μm.

(Method for producing reinforced α brass according to the present invention)
The manufacturing method of the reinforced alpha brass according to the present invention is such that the final recrystallization annealing is performed on the brass plate material under the conditions of 370 ° C. to 600 ° C., and then the final cold rolling of 7% to 55% is added, and further , the batch method The substrate material is characterized in that it is annealed at a low temperature under conditions of an actual temperature of 170 to 230 ° C. of the plate material or a furnace temperature of 250 to 450 ° C. in a continuous manner .

Moreover, as a manufacturing method of the reinforced alpha brass according to the present invention, a final recrystallization annealing is performed on the brass plate material under the condition of 255 ° C. to 290 ° C., and then a final cold rolling of 7% to 55% is added . Manufacture characterized in that the crystal structure is made into a mixed microstructure by low-temperature annealing in a batch system at a material temperature of 170 ° C to 230 ° C or in a continuous system at a furnace temperature of 250 ° C to 450 ° C. It is also preferable to adopt the method.

  It is preferable to adjust the Vickers hardness after recrystallization annealing in the above-described manufacturing method to be 140 Hv to 160 Hv.

In the said manufacturing method, it is preferable to perform low-temperature annealing by adopting the temperature range of 250 degreeC-450 degreeC of the furnace temperature of a heating furnace by a continuous system .

  The reinforced α brass according to the present invention has a composition composed of 82% to 62% by weight of copper, the balance zinc and inevitable impurities, and does not contain other alloy elements. However, its crystal structure is dense and uniform, and is a mixed structure of high dislocation density grains and reorganized grains. It exhibits mechanical properties comparable to or superior to phosphor bronze, and has an excellent balance between yield strength and bending performance. In addition, the stress relaxation characteristics are superior to those of conventional brass materials. And the manufacturing method of the reinforced alpha brass which concerns on this invention can obtain the above-mentioned outstanding physical property stably, and is suitable for production on an industrial scale.

(Form of reinforced α brass according to the present invention)
The α brass according to the present invention is a reinforced α brass composed of 82% to 62% by weight of copper, the remaining zinc and inevitable impurities as described above. Here, what is referred to as α brass is an α-phase single-phase copper-zinc alloy including a portion referred to as red copper having the lowest copper content. In addition, as a feature of the reinforced α brass according to the present invention, it is possible to exhibit bending workability comparable to that of phosphor bronze and stress relaxation superior to conventional brass materials.

  Here, the reason why the composition of the reinforced α brass according to the present invention is determined as described above will be described. In a copper-zinc alloy, when the amount of the copper component exceeds 82% by weight, the strength level is lowered, and when the strength is forcibly increased, the tendency to deteriorate the bending workability becomes remarkable. Moreover, when the amount of copper component is less than 62% by weight, a β phase appears and an α phase monolayer structure cannot be obtained. Furthermore, with regard to inevitable impurities, it is necessary to consider the scrap raw material used to reduce the cost, as can be said with general copper products. Since Fe as an impurity affects the recrystallization temperature, it is desirable that it be 0.01% by weight or less. Sn as an impurity has no particular adverse effect, but if it exceeds 0.1% by weight, it has a positive effect on strength and corrosion resistance, so it should be handled as a separate alloy. S as an impurity has an adverse effect on hot workability, workability of final product expansion, cutting, and the like, so it is desirable to suppress it to 0.003% by weight or less.

  In the α brass according to the present invention, 0.2% proof stress, which is mainly used as a design standard, was used instead of tensile strength. Therefore, strength is used as an index of strength. In the present invention, the term “bending workability” is based on the premise that, among various bending tests, so-called Bad way bending in which the bending axis of right-angle bending is made parallel to the rolling direction is evaluated. When a bending test is performed with the direction perpendicular to the rolling direction as the bending axis (Good way), in the case of brass, it is normal to always obtain better results than bending with a bending axis parallel to the rolling direction. Yes, it is not suitable for selection of manufacturing methods. Therefore, in this specification, only bad way bending was used for evaluation.

  Here, regarding bending workability, as long as MBR / t is 0.3 or less, no problem is caused even if almost any processing method is adopted. On the other hand, if MBR / t is 1.0 or less, it is often acceptable in material design. Furthermore, if MBR / t exceeds 3, bending becomes difficult, and the application is greatly limited. In conventional brass, there are few products with a yield strength exceeding 550 MPa in which MBR / t exceeds 1.0, and when the yield strength becomes lower than around 500 MPa, there is no problem in bending workability.

  However, even conventional brass has a proof stress of 530 MPa and can clear MBR / t of 0.3 or less. Considering this, if the proof strength of the reinforced α brass according to the present invention is less than 540 MPa, it can be determined that no technical value is produced because the conventional brass can be used. Furthermore, even with conventional brass, it is possible to have a proof stress of 560 MPa or more, but in such a case, MBR / t exceeds 1.0 which is a general material design allowable value, which is not preferable.

  In addition, when the bending workability of the phosphor bronze of the formula (1) is less than 590 MPa, MBR / t is 0.3 or less, so that the usefulness of the product of the present invention for phosphor bronze is lowered. On the other hand, when the yield strength exceeds 800 MPa, MBR / t exceeds 3, which is not practical.

In the present specification, the reinforced α brass according to the present invention is defined in terms of its physical properties and structure. Here, the physical properties of the reinforced α brass according to the present invention will be described in comparison with those of phosphor bronze. Therefore, a description of the bending workability of phosphor bronze will be made so that it can be compared with the reinforced α brass according to the present invention. When the data by the same evaluation method used for the bending workability evaluation of the reinforced α brass according to the present invention is seen in Non-Patent Document 5, the minimum bending radius that does not cause cracking is MBR, the thickness is t, and 0.2% proof stress. When σ is _0.2 , the bending workability of phosphor bronze can be expressed by the following equation (5).

  When Expression 5 is represented in the drawing, the straight line shown as (1) in FIG. 1 is obtained. In the case of phosphor bronze having a thickness t, the relationship between the minimum bending radius (MBR) and the 0.2% proof stress is substantially in line with the equation (1). Accordingly, it is determined that the case of being in the vicinity of the expression (1) has the same physical properties as phosphor bronze. The bending workability of the phosphor bronze of the formula (1) is MBR / t of 0.3 or less when the proof stress is less than 590 MPa. However, when the proof stress exceeds 800 MPa, the MBR / t exceeds 3, and the bending work becomes difficult. Not. When phosphor bronze is actually measured, there is a case where this equation (1) may not be satisfied. For example, on the side where the proof stress is low or the proof strength is high, there is a tendency that MBR / t is higher than the calculation formula. Based on this premise, the reinforced α brass according to the present invention will be described below.

The physical properties of the first reinforced α brass are a 0.2% proof stress of 540 MPa to 800 MPa, a minimum bending radius (MBR) that does not cause cracks in a right angle bending (Bad way bending) with the rolling direction as a bending axis, and a plate The thickness (t) and the 0.2% proof stress (σ _0.2 ) satisfy the following relationship of Equation 6. However, when the value of MBR / t is 0.3 or less, it is regarded as 0.3.

Referring to FIG. 1, Equation 6 is a state in which Equation (2) is shifted by 0.3 in the + direction of the Y-axis direction (Y-axis is MBR / t) based on Equation (1). It becomes. Therefore, considering that Equation 6 is satisfied and that there is a certain variation in the quality of phosphor bronze, it can be said that the reinforced α brass according to the present invention has the same bending workability as phosphor bronze. . When the relationship between the value of MBR / t and the value of σ _0.2 is outside the range shown in Equation 6, bending workability is deteriorated. Here, when the calculated value of MBR / t is 0.3 or less, it is regarded as 0.3 because, like phosphor bronze, MBR / t is higher than the calculation formula on the side where the proof stress is low. It was considered on the premise that there is a tendency, and that when the calculated value of MBR / t is 0.3 or less, bending workability is less likely to be a problem, and that there is a certain variation in measurement.

The physical properties of the second reinforced α brass are a 0.2% proof stress of 590 MPa to 800 MPa, a minimum bending radius (MBR) that does not cause cracks in a right-angle bending (Bad way bending) with the rolling direction as the bending axis, and a plate The thickness (t) and the 0.2% proof stress (σ _0.2 ) satisfy the following expression (7).

  Looking at FIG. 1 showing the above formula 7, it is the most inferior position in the table of FIG. Therefore, it can be said that it has a particularly excellent quality balance between proof stress and bending performance, which exceeds the bending performance of phosphor bronze. By adopting a manufacturing method to be described later, the yield strength is 590 MPa or more, bending workability superior to phosphor bronze is realized, and Equation 7 is satisfied. If the final cold working rate is low and the yield strength is less than 590 MPa, Equation 7 is not satisfied.

  Here, the reinforced α brass satisfying Equation 6 or Equation 7 is a structure derived from a recrystallized structure having an average crystal grain size of 2 μm or less as a whole. That is, when a recovery structure after low-temperature annealing obtained by the manufacturing method described later is provided, and the average crystal grain size during recrystallization is 2 μm or less, a correlation along Equation 6 or Equation 7 is observed. This is preferable. Further, the reinforced α brass satisfying Equation 7 is a structure derived from a recrystallized structure having a value of [yield strength] / [tensile strength] of 80% or more and an average crystal grain size of 1.5 μm or less. That is, it has a recovery structure after low-temperature annealing obtained by the production method described later, and the value of [proof strength] / [tensile strength] at the time of recrystallization is 80% or more and the average crystal grain size is 1.5 μm or less. Is preferable because the correlation along Equation 7 can be seen.

  The provisions relating to the structure of the crystal structure of the reinforced α brass according to the present invention described above are clarified by confirming the crystal structure with a transmission electron microscope. In the crystal structure of the reinforced α brass satisfying Formula 6 or Formula 7, grains with strong processing strain remained (high dislocation density grains with the most frequent grain size of 1 μm to 2 μm) and strain reorganization occurred. In the case of a mixed microstructure of the structure (reorganized grains (cell-like structure) with the most frequent particle size of 0.2 μm to 1.5 μm), the balance between proof stress and bending workability is in a good range, and phosphorus It has become clear that it exhibits bending performance equivalent to or exceeding phosphor bronze. The crystal structure of the reinforced α brass described above is a microstructure in which grains whose strain is released by low-temperature annealing and grains which are not released are mixed. This microstructure is similar to a fine two-phase mixed structure. It is understood that the inhomogeneous sliding is promoted and the bending workability is improved. In addition, since the stress relaxation property is improved by low-temperature annealing, it is essential to have the above-mentioned structure in terms of ensuring good bending workability and ensuring good stress relaxation property.

(Manufacturing form of reinforced α brass)
Regarding α brass, it is widely known that the strength after annealing increases if the crystal grains are made finer. It is also known that in order to produce a brass having fine crystal grains, after annealing at a high processing rate, annealing may be repeated for a long time at a relatively low temperature. For example, in the manufacturing method disclosed in Patent Document 3, since it is an essential requirement to combine processing with a high processing rate a plurality of times, it may be difficult to manufacture a relatively thick product. Furthermore, in this patent document 3, about the annealing before the last recrystallization annealing, there are only several examples of annealing temperatures, and the annealing conditions are not regarded as important.

  However, even though various proposals regarding the theoretical production method have been made, production condition management is difficult, and production conditions that can be industrially mass-produced have not been found. Thus, as a result of intensive studies by the present inventors, the inventors have come up with conditions for obtaining a fine grain structure that is excellent in industrial productivity and can reduce variations in product quality. The manufacturing method described below is easy for industrial use.

  In order to obtain the reinforced α brass according to the present invention, fine and homogeneous crystal grains are obtained during recrystallization annealing, rolled to obtain a desired strength, and further, some desired strains are removed. The low-temperature annealing is performed to make the structure of this. In order to obtain such fine and uniform crystal grains, it is necessary to control the cold working rate before recrystallization annealing and the crystal grain diameter before that.

  Before explaining this manufacturing method, the annealing temperature and annealing time mentioned here will be specified. In the case of batch annealing, the actual temperature can be measured, the temperature is the actual temperature, and the time is the holding time at the temperature ± 5 ° C. On the other hand, in the case of continuous annealing, it is difficult to measure the actual temperature, and when the plate is passed through a heating furnace having a predetermined temperature, the plate temperature gradually increases and reaches the maximum temperature at the outlet of the heating furnace. The outlet temperature is considered to be several to tens of degrees lower than the heating furnace temperature referred to in the temperature condition of the present invention. Therefore, it is appropriate to express the annealing temperature as the temperature of the heating furnace, and the annealing time as the time passing through the heating furnace. In the present invention, a continuous annealing furnace is assumed to be a continuous annealing furnace. There are a radiant tube type and a plenum chamber type as a method, and a horizontal floating method includes a static pressure method and a jet flow dynamic pressure levitation method, but there is no problem even if either method is adopted. However, most preferably, the plenum chamber type jet-type dynamic pressure levitation method is easy to raise the temperature and easy to control. In any case, a fine limitation on the annealing time is not practical and should be determined according to the characteristics of the apparatus.

1st manufacturing method; The 1st manufacturing method of the reinforcement | strengthening alpha brass which concerns on this invention performs final recrystallization annealing with respect to a brass plate material at 370 degreeC-600 degreeC, and 7%-55% of final cold rolling is carried out after that. In addition, it is characterized by further low-temperature annealing.

  “Brass plate material” as used herein means a plate in a state before one or more rolling steps and recrystallization annealing from the state of the brass ingot, and before final final recrystallization annealing and final cold rolling treatment. is doing. And this brass plate material is a thing after rolling the plate material which adjusted (1) average crystal grain diameter to 1-2 micrometers with arbitrary processing rates. (2) After rolling an annealed material with an average crystal grain size adjusted to 3-6 μm at a processing rate of 70-82%. (3) After rolling an annealed material of an arbitrary particle size at a processing rate of 83% or more. It is preferable to use one in any of the above states.

  Further, by the final recrystallization treatment, a final recrystallization treatment material having a value of [yield strength] / [tensile strength] of 80% or more and an average crystal grain size of 1.5 μm or less is obtained. It can also be used as a product after low-temperature annealing. In this case, the brass plate material was obtained by rolling an annealed material adjusted to an average crystal grain size of 3 μm to 6 μm by a continuous annealing method at a processing rate of 70% to 82%, or an average crystal grain size of 1 μm to 2 μm. It is preferable to use one after rolling an annealed material adjusted by a continuous annealing method at a processing rate of 50% to 82%.

  In the final recrystallization annealing before the final cold rolling, as the processing rate of the plate material before the recrystallization annealing is increased or the crystal grain size is reduced by the annealing before the final recrystallization annealing, the fine crystal grains become smaller. It is known to be obtained. However, the desired industrially required thickness is determined to some extent, and the processing rate that is advantageous in terms of cost is naturally determined, and as the crystal grain size is reduced by annealing further before the final recrystallization annealing, Subsequent problems such as high rolling pressure in cold rolling and an increase in the number of passes occur. Therefore, in the method for producing reinforced α brass according to the present invention, if a strong rolling process can be performed before the final recrystallization annealing before the final cold rolling, the crystal grains can be refined even if the crystal grain size is large. The brass plate material of (3) above can be used, and when a moderate rolling process can be applied, the brass plate material of (2) above, when trying to set the rolling reduction rate during rolling, A brass plate material having a crystal grain size as in (1) is used. Further, when manufacturing a thin product, the step (1) or (2) is further repeated, which is preferable in terms of characteristics.

  As a brass plate material, (1) a case where a plate material having an average crystal grain size adjusted to 1 μm to 2 μm after being rolled at an arbitrary processing rate will be described. When the crystal grain size is 1 μm to 2 μm, a processing rate of 20% to 82% is adopted in the following cold rolling, and fine grains can be easily obtained by subsequent recrystallization annealing even at a low processing rate. I can do it. And even if it passes through a subsequent process, it becomes possible to obtain a high yield strength and favorable bending workability. From an industrial viewpoint, it is difficult to produce crystal grains having an average crystal grain size of less than 1 μm. In order to obtain the level of the average crystal grain size mentioned here, it is necessary to satisfy the condition (3) or (2) in the previous step. In addition, when the processing rate at the time of subsequent rolling of the plate material whose average crystal grain size is adjusted to 1 μm to 2 μm is less than 50%, a large crystal grain size may be mixed when recrystallization is performed. It is not preferable when 7 is satisfied.

  As the brass plate material, (2) a case where an annealed material whose average crystal grain size is adjusted to 3 μm to 6 μm after being rolled at a processing rate of 70% to 82% will be described. If the crystal grain size before processing exceeds 6 μm, even if 82% processing is added, sufficient crystal grains cannot be made fine and bending workability deteriorates. Moreover, when the crystal grain size is an average crystal grain size of less than 3 μm, the subsequent rolling pressure becomes high, which is disadvantageous. Further, in the case where the average crystal grain size before processing is 3 μm to 6 μm, if the processing rate is less than 70%, appropriate crystal grains cannot be refined and bending workability deteriorates.

  As a brass plate material, (3) a case where an annealed material having an arbitrary particle diameter is rolled at a processing rate of 83% or more will be described. This is because when the processing rate before annealing is 83% or more, even if the previous crystal grain size is large, the strong processing results in a subgrain structure of around 1 μm. This is because good proof stress and bending workability, which are the objects of the invention, can be obtained. In addition, the annealing material of the said arbitrary particle diameter includes the case of a hot-rolled finishing material. Note that the grain size of the crystal structure of the plate after hot rolling is 100 μm to 200 μm when a small test rolling mill is used, but in the case of an industrial hot rolling mill, dynamic recrystallization occurs and becomes about 25 μm. . The inventor has confirmed that there is no difference in performance when adding 83% or more of processing, regardless of which hot rolled material is used.

  In the manufacturing method of the reinforced alpha brass according to the present invention, the final recrystallization annealing is performed at a temperature of 370 ° C. to 600 ° C. with respect to the brass plate material described above. The final recrystallization annealing before the final cold rolling is mainly assumed to be performed by continuously passing through a furnace. At this time, when the furnace temperature is lower than 370 ° C., the bending workability of the product obtained is deteriorated even if recrystallization is carried out at a lower plate passing speed. On the other hand, if the furnace temperature exceeds 600 ° C., the crystal grain size increases as it exceeds 2.0 μm, and bending workability deteriorates even if low-temperature annealing described later is further added. The final recrystallization annealing time at this time is determined by the capacity of the furnace, the plate thickness, and the desired strength, but in the case of ordinary industrial equipment, it is in the range of 10 seconds to 120 seconds. If a practically appropriate time is to be determined, it is simply managed by the hardness and determined so that the Vickers hardness is 140Hv to 160Hv. If the Vickers hardness is not within this range, the bending workability of the reinforced α brass as the final product is deteriorated. In the plate material at the stage where the final recrystallization annealing has been completed, when only bending workability is seen, even if the bending radius is 0, bending can be performed without any problem.

  As described above, the advantage of continuous recrystallization annealing is that it is easy to reduce costs and ensure quality stability. In the batch method, the uneven distribution of temperature tends to occur depending on the position in the furnace. In addition, when batch-type annealing is performed, the [yield strength] / [tensile strength] value after final recrystallization annealing is less than 80%, whereas after continuous recrystallization annealing when the continuous heating method is adopted. The value of [yield strength] / [tensile strength] is as high as 80% or more. Therefore, even when the continuous heating method is more effective than the batch heating method in the case where the proof strength of the reinforced α brass obtained through the following final cold working and low temperature annealing is set to a range of 590 MPa or more, the processing rate is relatively low. It can be processed and is advantageous for obtaining good bending workability exceeding phosphor bronze. And, such an effect is caused by the difference in the residual form of dislocation because the annealing temperature in the continuous method is higher and the heating time is shorter than in the batch method, and the grain size distribution becomes narrower. It is thought that.

  And the processing rate of the last cold working after the last recrystallization annealing employs a range of 7% to 55%. In the case where the processing rate is less than 7%, the yield strength is lowered even if low-temperature annealing described later is performed. On the other hand, if the processing rate of the final cold working exceeds 55%, the bending workability exceeds 3 in MBR / t even though work hardening progresses and the yield strength is improved, and mechanical properties are increased. It cannot be said to be a well-balanced reinforced alpha brass. Furthermore, when a bending test is performed using the plate material after about 30% processing as the final cold working, bending workability similar to phosphor bronze can be obtained depending on the final recrystallization annealing conditions. There is. Therefore, in applications where stress relaxation does not become a problem without performing low-temperature annealing, it may be possible to use reinforced α brass at this stage as a product.

  The low-temperature annealing finally performed does not refer to the strain relief annealing performed at a low temperature, but refers to a process involving a so-called low-temperature annealing hardening phenomenon. In this low-temperature annealing, as a condition for low-temperature annealing hardening, in the case of batch-type annealing, it is preferable to adopt a condition of 170 ° C. to 230 ° C. × 0.5 hours to 5 hours at the substantial temperature. When the solid temperature is lower than 170 ° C., there are few grains whose strain is released and bending workability is deteriorated. On the other hand, when the substantial temperature exceeds 230 ° C., crystal grain growth occurs, and the bending workability deteriorates again. By performing this low-temperature annealing, it is possible to obtain bending workability that is even better than that of cold rolling work, and it becomes reinforced α brass having proof stress and bending workability equal to or higher than phosphor bronze.

  Moreover, when performing the low temperature annealing finally performed with a continuous furnace, it is preferable to pass through the furnace at a temperature of 250 ° C. to 450 ° C. and a passing time of 1 second to 60 seconds. When the furnace temperature is lower than 250 ° C., the number of grains whose strain is released is reduced even when the heat treatment is performed at a lower plate passing speed, and the bending workability is deteriorated. On the other hand, even if the furnace temperature exceeds 450 ° C., even if the speed is increased, the bendability is poor due to grain growth and the proof stress is lowered.

  The low-temperature annealing described above is also preferably performed by adopting a continuous method rather than a batch method. The merit of performing low-temperature annealing continuously is the same as that in the case of final recrystallization annealing in that it is easy to reduce costs and secure quality stability. In addition, this low-temperature annealing is final annealing, and is usually in a strip state after the low-temperature annealing is completed. In the batch-type annealing, it is placed in a heating furnace in the state of strips and heated as it is. Therefore, the curl is attached to the strip, and correction is required up to curl in addition to distortion due to rolling in the correction process before use as a product, but effective correction becomes difficult. On the other hand, in the continuous method, the plate material is heated while traveling in the heating zone, and is wound into a strip state after completion of the low-temperature annealing. Is easier to obtain

Second production method: The second production method of the reinforced α brass according to the present invention is the final recrystallization annealing performed on the brass plate material under the condition of 255 ° C. to 290 ° C., and then the final cold of 7% to 55%. It is also preferable to employ a production method characterized by adding rolling and further annealing at a low temperature. The final recrystallization conditions are determined so that the Vickers hardness becomes 140 Hv to 160 Hv after the final recrystallization annealing. Here, only a different part from the 1st manufacturing method of the reinforced alpha brass which concerns on the above-mentioned this invention is demonstrated. The concept of “brass plate material” is the same as described above.

  When the final recrystallization annealing before the final cold rolling is performed by a batch method, the conditions of 255 ° C. to 290 ° C. are adopted. Here, when the furnace temperature is less than 255 ° C., recrystallization to match the desired strength results in irregular grain sizes (in the grain size distribution diagram with the horizontal axis as the logarithm of the grain size). When viewed, the distribution has two or more peaks), and the bending workability is extremely deteriorated even if the annealing is performed at a low temperature. On the other hand, even if the furnace temperature exceeds 290 ° C., the crystal grains are not uniform in size and the average grain size becomes large. Even if this is annealed at low temperature, only products with poor bending workability can be obtained.

  As for the final recrystallization annealing time, when the holding time in the above-mentioned actual temperature range is less than 0.5 hours, the recrystallization becomes insufficient. On the other hand, when the holding time exceeds 5 hours, the crystal grains become large, and the bending workability is deteriorated even if the annealing is performed at a low temperature.

  And the processing rate of the final cold working after the last recrystallization annealing adopts the range of 7% to 55%. In the case where the processing rate is less than 7%, the yield strength is lowered even if low-temperature annealing described later is performed. On the other hand, if the processing rate of the final cold working exceeds 55%, the bending workability exceeds 3 in MBR / t even though work hardening progresses and the yield strength is improved, and mechanical properties are increased. It cannot be said to be a well-balanced reinforced alpha brass. Hereinafter, the low-temperature annealing finally performed is the same as in the case of the first manufacturing method.

  As described above, in order to obtain the reinforced α brass of the present invention, fine and homogeneous crystal grains are obtained at the time of final recrystallization annealing, and rolled to obtain a desired strength. It can be said that low-temperature annealing is performed to obtain a desired crystal structure with a strain removed. In order to obtain fine and uniform crystal grains, it is necessary to control the cold working rate before the final recrystallization annealing and the crystal grain diameter before that at a certain level.

  Hereinafter, although this invention is demonstrated in detail through an Example, suppose that the chemical composition of the brass ingot manufactured and evaluated by the following Examples and Comparative Examples is shown in Table 1. Here, the ingot 1, the ingot 5, and the ingot 6 are samples obtained by a semi-continuous casting method at a manufacturing site casting factory. The ingot 2, the ingot 3, and the ingot 4 were obtained by melting in a laboratory melting furnace and casting in a mold of 30 mm × 100 mm × 200 mm.

  As can be seen from Table 1, all of the ingots 1 to 6 are 82% to 62% by weight of copper and satisfy the condition that the balance is composed of the remaining zinc and inevitable impurities. Furthermore, in the following Examples and Comparative Examples, Table 2 shows the production conditions for reinforced brass using any of the ingots shown in Table 1 above.

  The ingot 1 was subjected to continuous annealing with a crystal grain size of 4 μm through hot rolling, chamfering, and cold rolling, and 78% cold working as a brass plate, and further subjected to continuous annealing under the conditions shown in Table 2. The final recrystallization annealing was performed on the pickling line (in Table 2, simply described as “recrystallization annealing”). Thereafter, cold rolling was performed at the final cold rolling rate shown in Table 2. Samples 1 to 3 are coils classified according to conditions such as final recrystallization annealing in the same casting lot, but were classified as the following samples. Sample 1 and Sample 2 were rolled at the final cold rolling rate shown in Table 2, then degreased, and low-temperature annealed in a batch type furnace. Sample 3 is obtained by degreasing after cold rolling at the final cold rolling rate shown in Table 2 and low-temperature annealing in a continuous annealing line. The thickness at the time of final recrystallization annealing was 0.40 mm. These mechanical properties, stress relaxation properties, and crystal grain size were evaluated and are shown in Table 4. The calculated values in Table 4 are calculated values on the right side of the equation shown in Equation 6. The measured MBR means the minimum bending radius without cracking when the sample with a thickness of 0.1 mm to 1.0 mm is observed with a magnifying glass and the sample with a thickness of less than 0.1 mm is 50 times the microscope. Is more than 1.0 mm, it means the lowest bend radius without wide cracks with the naked eye. Furthermore, the stress relaxation value is a stress relaxation value obtained under the condition of 120 ° C. × 100 hours based on the Japan Copper and Brass Association Technical Standard JCBA T309. The average crystal grain size was determined by a line segment method or a photographic comparison method.

As can be seen from Table 4, Sample 1 and Sample 2 also have a relationship of the minimum bending radius (MBR), the plate thickness (t), and the 0.2% proof stress (σ _0.2 ) that satisfies the above equation (7). Therefore, it can be judged that bending workability superior to that of phosphor bronze is obtained. In addition, the stress relaxation property is lower and superior as compared with Reference Example 1 used as a contrast material as a conventional material.

  Further, with respect to Sample 1 and Sample 2, the stress relaxation values were determined at 120 ° C. × 100 hours based on Japan Copper and Brass Association Technical Standard JCBA T309, and the results were 48% for Sample 1 and 41% for Sample 2. Further, for sample 1 and sample 2, the bending deflection coefficient was determined based on JCBA T312. As a result, Sample 1 was 103000 and Sample 2 was 100,000 MPa. Then, a sample was prepared in the form of a tensile test piece, a static load of 50 MPa was applied, and the parallel portion was exposed to steam from a liquid composed of ammonia water and water 1: 1, and a stress corrosion cracking test was performed. As a result, the time to break was 27 hours for sample 1 and 22 hours for sample 2. The spring limit values were 547 MPa for sample 1 and 648 MPa for sample 2, which was comparable to phosphor bronze. Furthermore, with respect to Sample 1, when the fatigue fatigue limit of 1,000,000 cycles was measured, it was 220 MPa and was comparable to general phosphor bronze.

  Next, sample 3 is an example in which the final cold rolling reduction is low, but in consideration of the balance between proof stress and bending, it is tensile compared to an example adopting the same processing rate (Example 6 described later). Strength and proof strength are much higher. This is considered to have the effect of performing the final recrystallization annealing in a continuous manner. Considering the balance between proof stress and bending, the examples included in the present specification do not show particularly excellent bending workability. However, it seems that the bending workability tends to be somewhat worse in the region where the proof stress is lower than the formula (6), and as shown in Table 4, it shows bending workability that is practically no problem. The stress relaxation rate of Sample 3 was 45% after 120 ° C. × 100 hours. Although low-temperature annealing is performed by a continuous method, there was no difference in mechanical characteristics as compared with a batch method. Incidentally, when the stress relaxation rate was measured with the sample before low-temperature annealing, it was 53%. The effect of performing the low-temperature annealing in a continuous manner is a great advantage in that there is no curl when it is striped as will be described later.

  In this example, Sample 4 and Sample 5 were prepared as follows. Sample 4 was obtained by subjecting the ingot 6 to the processes after the final recrystallization annealing shown in Table 2 after hot rolling, chamfering, and cold rolling of 84%. However, in the final cold rolling and low temperature annealing, samples obtained from on-site continuous annealing materials were processed in the laboratory. Low temperature annealing was performed in a salt bath. The rising thickness is 1.27 mm. When the evaluation results are seen from Table 4, it can be judged that the characteristics of Sample 4 are slightly inferior to those of other samples, probably because recrystallization annealing is performed only once.

  In Sample 5, the final recrystallized annealed material of Sample 4 was made into a brass plate that was further cold worked at a processing rate of 56%, and then the treatment shown in Table 2 (final recrystallized anneal, low temperature anneal uses a continuous annealing furnace. ) Was performed using the on-site line. The rising thickness is 0.52 mm. When the evaluation result is seen from Table 4, it can be judged that the balance between the yield strength and the bending satisfies Equation 7 and is excellent. And it can be judged that the stress relaxation property is also superior to the conventional material.

  In this example, the ingot 6 was subjected to hot rolling, chamfering, 84% cold rolling, followed by continuous annealing with a crystal grain size of 4 μm, 78% cold rolling, 420 ° C. × 12 seconds continuous annealing. (The obtained crystal grain size was 1.4 μm) Further, after 70% cold-rolled brass plate material was obtained, the treatments listed in Table 2 were performed. The final recrystallization treatment is continuous annealing, and the low temperature annealing is batch annealing. All processes were performed on site and the final thickness was 0.08 mm. When the evaluation results are seen from Table 4, it can be determined that the balance between the yield strength and the bending satisfies Expression 7 and is very excellent. Moreover, it can be judged that the stress relaxation property is also superior to the conventional material.

  Last but not least, let me reiterate the product rolls. Sample 1, Sample 2, Sample 3, Sample 5, and Sample 6 are each subjected to low-temperature annealing using an on-site line. These samples were subjected to a correction operation with a tension leveler after low-temperature annealing. As a result, in Sample 1 and Sample 2, curl due to low-temperature annealing before correction was accompanied by rolling distortion, and satisfactory correction was not possible after correction, and the distortion remained at one end in the plate width direction. On the other hand, in Sample 3 and Sample 5, distortion due to low-temperature annealing did not occur, and a flat product plate could be obtained by correction. In addition, a product with a non-flat shape cannot be subjected to high-speed pressing and cannot be used in a practical sense. Furthermore, in the case of Sample 6, since the thickness was small, no curl was found even after batch annealing.

  The ingot 2 was used, and after hot rolling and cold rolling in a laboratory, recrystallization annealing was performed to obtain a crystal grain size of 5 μm, and a plate material that had been cold rolled by 78% was obtained. Thereafter, the plate material was subjected to recrystallization annealing at 270 ° C., final cold rolling at 25%, and low temperature annealing at a temperature of 205 ° C. to prepare a reinforced α brass sample under the conditions shown in Table 2. The final thickness is 0.3 mm. Low-temperature annealing was performed while measuring the actual temperature in a laboratory muffle furnace. The results of mechanical property evaluation are shown in Table 4 below.

  The ingot 3 was used, and after hot rolling and cold rolling in a laboratory, recrystallization annealing was performed to obtain a crystal grain size of 5 μm to obtain 78% cold rolled sheet material. Thereafter, the plate material was subjected to recrystallization annealing at 270 ° C., final cold rolling at 25%, and low temperature annealing at a temperature of 205 ° C. to prepare a reinforced α brass sample under the conditions shown in Table 2. The final thickness is 0.3 mm. Low-temperature annealing was performed while measuring the actual temperature in a laboratory muffle furnace. The results of mechanical property evaluation are shown in Table 4 below.

  Using ingot 4, a brass plate material having 78% cold rolling was obtained by performing recrystallization annealing to a crystal grain size of 5 μm after hot rolling and cold rolling in a laboratory. Thereafter, the brass sheet was subjected to final recrystallization annealing at 270 ° C. under the conditions shown in Table 2, rolling at a final cold rolling rate of 25%, and low temperature annealing at a temperature of 205 ° C. to strengthen α brass sample. It was created. Low-temperature annealing was performed while measuring the actual temperature in a laboratory muffle furnace. The final thickness is 0.3 mm. The results of mechanical property evaluation are shown in Table 4 together with the above examples.

  It can be seen from Table 4 that even if the amount of the copper component is varied in the composition of the reinforced α brass according to the present invention, no significant difference is produced, and mechanical properties similar to phosphor bronze can be obtained.

  In this example, the final recrystallization annealed material of Sample 4 of Example 2 was subjected to a cold rolling process with a processing rate of 20% in the laboratory to obtain a brass plate material, and this brass plate material was annealed at 440 ° C. by a salt bath. Final recrystallization annealing was performed under the condition of 10 seconds, and a final cold rolling process with a processing rate of 30% and low temperature annealing at 280 ° C. × 10 seconds were added to prepare a sample. The average crystal grain size at this time was 2.6 μm, and the mechanical properties are listed in Table 3. And this Example 7 is an Example for verifying an appropriate processing rate together with the result of Example 8.

  In this example, the final recrystallization annealed material of Sample 4 of Example 2 was subjected to a cold rolling process with a processing rate of 40% in a laboratory to obtain a brass plate material, and this brass plate material was annealed by a salt bath at 420 ° C. × A final recrystallization annealing was performed under the condition of 10 seconds, and a rolling process with a processing rate of 30% and a low temperature annealing of 280 ° C. × 10 seconds were added to prepare a sample. The average crystal grain size at this time was 2.3 μm, and the mechanical properties are listed in Table 3. And this Example 8 is an Example for verifying an appropriate processing rate together with the result of Example 7.

  As can be seen from Table 3, it can be seen that characteristics within a desired range can be obtained even if a rolling process with a processing rate of 20% is applied to a plate material having an average crystal grain size of 1.9 μm. However, since the strength is relatively low and the crystal grain size remains large, it can be determined that it is desirable to employ a processing rate of 40% or more.

Comparative example

(Comparative Example 1)
In Comparative Example 1, the low temperature annealing of Sample 1 is omitted. Even if low-temperature annealing is omitted, it can be proved that a balance between good yield strength and bending workability can be secured. Therefore, there is a possibility that it can be provided at an inexpensive price with reduced production costs for uses that do not require low-temperature annealing. Thus, after recrystallization annealing, cold working is applied, and the brass crystal structure that exhibits bending workability similar to phosphor bronze even without low temperature annealing has an average crystal grain size of 1.0-1 during recrystallization annealing. In this case, the size of the crystal grains is uniform, and in order to obtain such a structure stably, annealing by a continuous method is suitable. In addition, although it becomes clear if the sample 1 of Example 1 of Table 4 and the comparative example 1 are contrasted, since the low temperature annealing is abbreviate | omitted in the comparative example 1, intensity | strength is low and the balance of proof stress and bending workability is. , Worse than sample 1.

(Comparative Example 2)
When preparing the sample of Example 4, it is the sample extract | collected before low-temperature annealing. Therefore, the final recrystallization annealing is performed by a batch method, and the sample has no low temperature annealing. The processing conditions of the sample of Comparative Example 2 are listed in Table 2, and the mechanical property evaluation results are listed in Table 4 together with other Examples and Comparative Examples. The final recrystallization annealing is a batch method, and it is considered that the crystal structure varies (broadening of the particle size distribution). As a result, there is no problem in yield strength and hardness, but the product has poor bending workability. ing.

(Comparative Example 3)
Using the ingot 2, a sample having a proof stress equivalent to that of Example 4 was made in the laboratory to resemble the conventional process. That is, the sample here was subjected to cold working at a working rate of 53% after hot rolling and cold rolling, after annealing to a crystal grain size of 35 μm. Thereafter, the sample was processed under the conditions shown in Table 2. In addition, recrystallization annealing was performed using the salt bath so that it might resemble the continuous annealing of a conventional process. The crystal grain size after final recrystallization annealing was 15 μm. The results after final rolling with a processing rate of 65% are shown in Table 4. As can be seen from Table 4, it can be said that when the final rolling rate is increased to increase the yield strength, the bending workability is greatly deteriorated. The final thickness is 0.3 mm.

(Comparative Example 4)
An attempt was made to make a sample having the same proof strength as the sample of Example 5 in the laboratory using the ingot 3 to resemble the conventional process. The sample here was subjected to cold working at a working rate of 53% after hot rolling and cold rolling, after annealing so that the crystal grain size was 45 μm. Thereafter, final recrystallization annealing and final cold rolling were performed under the conditions shown in Table 2. The final recrystallization annealing at this time was performed using a salt bath so as to resemble the continuous annealing of the conventional process. The crystal grain size after recrystallization annealing was 25 μm. Table 4 shows the evaluation results of mechanical properties after the final cold rolling with a processing rate of 65%. As can be seen from Table 4, it can be said that when the final cold rolling rate is increased to increase the yield strength, the bending workability is greatly deteriorated. The final thickness is 0.3 mm.

(Comparative Example 5)
Attempts were made to use the ingot 4 in the laboratory to make a sample having the same strength as the sample of Example 6 in a manner similar to the conventional process. The sample here was subjected to cold working at a working rate of 53% after hot rolling and cold rolling, after annealing so that the crystal grain size was 45 μm. Thereafter, final recrystallization annealing and final cold rolling were performed under the conditions shown in Table 2. The final recrystallization annealing at this time was performed using a salt bath so as to resemble the continuous annealing of the conventional process. The crystal grain size after final recrystallization annealing was 20 μm. Table 4 shows the evaluation results of mechanical properties after the final cold rolling with a processing rate of 65%. As can be seen from Table 4, it can be said that bending workability is greatly deteriorated when the final cold rolling rate is increased to increase the yield strength. The final thickness is 0.3 mm.

(Comparative Example 6)
A sample was collected at the stage when the annealing of the sample 1 to a crystal grain size of 4 μm was completed, and after 78% cold working, final recrystallization annealing was performed under the low temperature conditions shown in Table 2, and further cold working was performed. The final recrystallization annealing was performed in a laboratory muffle furnace so as to have a yield strength equivalent to that of Example 5. The evaluation results of the mechanical properties of this sample are shown in Table 4. When the final recrystallization temperature is thus too low as compared with Example 5, it can be said that there is no problem with the yield strength and hardness, but the bending workability is adversely affected. The final thickness is 0.26 mm.

(Comparative Example 7)
A sample was collected at the stage when the annealing of sample 1 to a crystal grain size of 4 μm was completed. After cold working of 78%, final recrystallization annealing was performed under the high temperature conditions shown in Table 2, and further, final cold rolling was performed. Annealing was performed in a laboratory muffle furnace so as to have the same yield strength as in Example 5. The evaluation results of the mechanical properties of this sample are shown in Table 4. As can be seen from Table 4, when the final recrystallization temperature is too high as compared with Example 5, there is no problem in yield strength and hardness, but it can be said that bending workability deteriorates. The final thickness is 0.26 mm.

(Reference example)
A sample was taken from the product manufactured from the ingot 5 on the production line. The crystal grain size of this sample was 5 μm. The evaluation results of the mechanical properties of this sample are shown in Table 4 together with other examples and comparative examples. Using this sample, the stress relaxation test, the bending deflection coefficient measurement, the stress corrosion test, and the fatigue limit measurement were performed in the same manner as in Example 1. As a result, the stress relaxation was 52%, the bending deflection coefficient was 102000 MPa, the stress corrosion cracking rupture time was 4 hours, and the fatigue limit was 160 MPa. Sample 1 and Sample 2 are superior to Reference Example 1 in terms of stress relaxation rate, stress corrosion cracking resistance, fatigue limit, and high bending strength even though they are high in strength. .

<Contrast between Example and Comparative Example>
Focusing on “MBR / t (measured value)” indicated simply as “MBR / t” in Table 4 and “MBR / t” indicated as “MBR / t (calculated value)”, Example In all cases, the relationship “MBR / t (actual value)” ≦ “MBR / t (calculated value)” is established. In contrast, in the comparative example, except for the comparative example 1 (example in which the stress relaxation property is poor), the relationship “MBR / t (actual value)”> “MBR / t (calculated value)” is established. Therefore, it can be said that the reinforced α brass of the above example has better bending workability than the calculated value and is superior to most comparative examples in bending workability.

  Next, paying attention to 0.2% proof stress, the reinforced α brass of the example shows a value of 556 MPa to 743 MPa. On the other hand, the 0.2% proof stress of the brass of the comparative example is 576 MPa to 610 MPa, a large difference is observed in the upper limit value, and the reinforced α brass according to the present invention is superior in terms of proof stress. I understand that.

  When attention is paid to the hardness (Vickers hardness), the reinforced α brass of the example shows a hardness in the range of 190 Hv to 214 Hv. On the other hand, the hardness of the brass of the comparative example is in the range of 184Hv to 197Hv. This distribution of hardness also suggests that the reinforced α brass according to the present invention has excellent mechanical strength and hardness that improves wear resistance.

  Further, looking at the tensile strength, the reinforced α brass of the example shows a value of 606 MPa to 776 MPa. On the other hand, the brass of the comparative example shows a value of 633 MPa to 700 MPa. Therefore, a large difference is observed in the upper limit value, and it can be seen that the reinforced α brass according to the present invention can obtain a higher tensile strength.

  In Table 4, the characteristics after the final recrystallization annealing are listed for reference, but the yield strength of the samples of each example is generally higher than the yield strength of the samples of the comparative examples. And the same tendency is shown also in tensile strength. Furthermore, when the value of [proof stress] / [tensile strength] is seen as a characteristic after the final recrystallization annealing, the example shows a range of 74% to 83%, and a value of 80% or more is also obtained. On the other hand, in a comparative example, it is 35%-76% except the comparative example 1 which abbreviate | omitted the low temperature annealing performed to the sample 1 of Example 1. FIG. Therefore, it can be understood that the structural properties formed by recrystallization annealing are important in order to increase the mechanical properties of the reinforced α brass according to the present invention and to improve the bending workability.

  As described above, the mechanical properties after the final recrystallization annealing are considered important for the following reasons. In order to improve the bending workability of the reinforced α brass, it is considered necessary to reduce the anisotropy of the bending workability depending on the bending direction (Bad Way, Good Way). Such anisotropy tends to become more prominent as strong processing by rolling is performed. Therefore, it was considered necessary to lower the processing rate after the final recrystallization annealing. Therefore, even if the processing rate after the final recrystallization annealing is low, in order to achieve good strength and bending workability at the same time in the reinforced α brass stage of the final product, the strength after recrystallization annealing is already high. This is because it is necessary to be in

  Further, when the examples, comparative examples and reference examples are compared with respect to the stress relaxation properties, the stress relaxation properties of the reinforced α brass according to the above examples are as follows. It is equivalent to or slightly inferior to 52% of the level commercial brass. However, by applying low temperature annealing, the stress relaxation property of 40 to 48%, which is superior to commercially available brass (conventional material, reference example), is exhibited.

  As described above, the examples and comparative examples have been compared with respect to strength and bending workability, but when used for electronic parts such as connectors, they are also excellent in stress corrosion cracking resistance, fatigue characteristics, spring limit values, etc. Is often required. The stress corrosion cracking resistance of the reinforced α brass according to the above example is superior to that of commercially available brass. Furthermore, the fatigue properties are superior to conventional commercial brass and are comparable to general phosphor bronze. Also, the spring limit value becomes equivalent to that of phosphor bronze by performing low temperature annealing.

  FIG. 2 shows a transmission electron micrograph of Sample 5 (low-temperature annealed product) obtained in Example 2. FIG. 3 schematically shows the confirmation positions (represented by hatching in the drawing) of the reorganized dislocation grains generated by the low temperature annealing observed in FIG. Therefore, the state of the rearranged dislocation grains in the transmission electron microscope can be grasped by superimposing FIG. 2 and FIG. This reorganized dislocation grain is also called a cell structure, and the dislocation is reorganized and can be observed in a net shape. And the part in which the network is not formed has dislocations entangled by processing, and is observed in black. Thus, as in the manufacturing method according to the present invention, the structure obtained by employing the low temperature annealing is composed of a mixed structure. Furthermore, as can be understood by referring to the 1000 nm scale in the lower right of FIG. 2, this mixed structure is a high dislocation density grain with a most frequent grain size of 1-2 μm that remains with strong processing strain. In other words, it can be seen that the most frequent grain size of the structure in which strain reorganization occurs is a reorganized dislocation grain having a size of 0.2 to 1.5 μm.

  The reinforced α brass according to the present invention has a general α brass composition in terms of composition. However, by applying an appropriate rolling process and heat treatment, the balance between strength and bending workability equivalent to or exceeding phosphor bronze, which was not found in conventional α brass, is exhibited. Such reinforced α brass is suitable for electronic parts such as connectors and mechanical parts, and can be supplied as an inexpensive material.

  In addition, the manufacturing method of the reinforced α brass according to the present invention can be used as it is without adding any improvement to the rolling production line that has been used conventionally, and does not require special capital investment, Enables efficient production of high-quality reinforced alpha brass on an industrial production scale.

It is the conceptual diagram which showed correlation with the minimum bending radius (MBR / t) and yield strength. 2 is a transmission electron microscope observation image of Sample 5 prepared in Example 2. FIG. It is the figure which showed the distribution area | region of the rearrangement dislocation grain in the transmission electron microscope observation image of FIG.

Claims (8)

In reinforced α brass composed of 82% to 62% by weight of copper and the balance zinc and inevitable impurities,
0.2% proof stress is 540 MPa to 800 MPa,
The minimum bending radius (MBR) at which cracks do not occur in right-angle bending with the rolling direction as the bending axis, the plate thickness (t), and the 0.2% proof stress (σ _0.2 ) satisfy the relationship of Equation 1,
In addition, the crystal grains constituting the crystal structure are grains that remain with strong processing strain (high dislocation density grains with the most frequent grain size of 1 to 2 μm) and structures with strain reorganization (the most frequent grains). Reinforced α brass having a mixed microstructure of reorganized dislocation grains having a diameter of 0.2 to 1.5 μm.
In reinforced α brass composed of 82% to 62% by weight of copper and the balance zinc and inevitable impurities,
0.2% proof stress is 590 MPa to 800 MPa,
The minimum bending radius (MBR) at which cracks do not occur in right-angle bending with the rolling direction as the bending axis, the plate thickness (t), and the 0.2% proof stress (σ _0.2 ) satisfy the relationship of Equation 2,
In addition, the crystal grains constituting the crystal structure are grains that remain with strong processing strain (high dislocation density grains with the most frequent grain size of 1 to 2 μm) and structures with strain reorganization (the most frequent grains). Reinforced α brass having a mixed microstructure of reorganized dislocation grains having a diameter of 0.2 to 1.5 μm.
A method for producing reinforced alpha brass comprising copper 82 wt% to 62 wt%, the remainder zinc and inevitable impurities,
The brass sheet is subjected to final recrystallization annealing at 370 ° C. to 600 ° C., then 7% to 55% of final cold rolling is added, and further the batch material is used at a material temperature of 170 ° C. to 230 ° C. Or the manufacturing method of the reinforced alpha brass characterized by performing low temperature annealing on the conditions of the furnace temperature of 250 to 450 degreeC of a heating furnace by a continuous system . A method for producing α brass comprising copper 82 wt% to 62 wt%, the remainder zinc and inevitable impurities,
The final recrystallization annealing is performed on the brass plate material under the condition of 255 ° C. to 290 ° C., and then the final cold rolling of 7% to 55% is added. Furthermore , the material temperature of the plate material is 170 ° C. to 230 ° C. in a batch system. Or the manufacturing method of the reinforced alpha brass characterized by low-temperature annealing on the conditions of the furnace temperature of 250 to 450 degreeC of a heating furnace by a continuous system, and making a crystal structure into a mixed fine structure. The manufacturing method of the reinforced alpha brass of Claim 3 or Claim 4 adjusted so that the Vickers hardness after recrystallization annealing might be set to 140Hv-160Hv. The plate material before the final cold rolling is obtained by rolling a plate material having an average crystal grain size adjusted to 1 to 2 µm at a processing rate of 20 to 82%. The manufacturing method of reinforced alpha brass. The plate material before the final cold rolling is obtained by rolling a plate material having an average crystal grain size adjusted to 3 to 6 µm at a processing rate of 70 to 82%. The manufacturing method of reinforced alpha brass. The plate material before final cold rolling is obtained by rolling a plate material having an arbitrary average grain size at a processing rate of 83% or more. Production method.