JP2007046101A - HARD alpha-BRASS, AND MANUFACTURING METHOD OF THE HARD alpha-BRASS - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard α-brass material having strength equal to that of H materials regulated in JIS C2600 etc. and also having superior formability and excellent stress corrosion cracking resistance. <P>SOLUTION: As the α-brass by which the above objects can be attained, e.g. hard α-brass having the following characteristics is adopted: 451 to 519 MPa tensile strength; formability of ≥8.5 Erichsen value; stress corrosion cracking resistance of ≥6 hours time to rupture by stress corrosion cracking. As the manufacturing method of the hard α-brass, e.g. a manufacturing method in which an α-brass sheet of arbitrary grain size is cold rolled at ≥83% draft and then subjected to recrystallization annealing is adopted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to hard α brass and a method for producing the hard α brass. More specifically, the H material specified in JIS C2600, JIS C2680, and JIS C2720 is in the same range and has the same tensile strength, but particularly hard with excellent molding processability and stress corrosion cracking resistance. It is related with alpha brass material and its manufacturing method.

  Conventionally, the H material specified in JIS C2600, JIS C2680, and JIS C2720 (hereinafter sometimes simply referred to as “H material”) has relatively high mechanical strength, relatively high electrical conductivity, and Since it is inexpensive, it has been widely used as electronic parts such as terminals and connectors, and mechanical parts.

  However, when the general H material distributed in the above-mentioned market is processed into a part, even if it is going to add strong processing such as 180 degree adhesion bending processing, burring processing, overhang processing, deep fine projection formation by press, Due to the high mechanical strength, crystal characteristics, etc., there is a tendency for the moldability to be insufficient. Therefore, when trying to apply a material with more excellent moldability, a material with a higher elongation rate is selected even if the tensile strength is somewhat lacking. This also means that the mechanical strength is reduced, and reducing the quality leads to design changes such as increasing the thickness of the product from the viewpoint of material mechanics. This may be disadvantageous because it may increase the cost of the material. Moreover, in the case of a brass material, since the fault that it is inferior to stress corrosion cracking resistance is inevitably provided, depending on the use environment, changing a material into a brass is often performed.

  Considering the general manufacturing process of the H material, after casting, hot rolling, chamfering, cold rolling, continuous annealing, cold rolling, continuous annealing with reduced crystal grain size, 15% to 25% Manufactured by temper rolling. Various additional steps such as degreasing, pickling, straightening, cutting, and plating are provided between or after the rolling process and the heat treatment. And, as can be inferred from the content disclosed in Non-Patent Document 1, when trying to obtain the tensile strength at the H material level, a method utilizing work hardening by plastic working means such as a rolling process is adopted, which is desired. Strength.

  Patent Document 1 discloses a method for producing brass having fine crystal grains. However, in the manufacturing method disclosed in Patent Document 1, it is necessary to repeatedly perform rolling with a large processing rate in multiple stages. Therefore, this technique can be applied to obtain a thin product. On the other hand, when trying to obtain a relatively thick product, it may be difficult to apply the rolling process under strong processing conditions multiple times. Further, in the contents disclosed in Patent Document 1, although there is a description regarding the annealing to be finally performed, control of the annealing conditions before that is also important, but there is no disclosure.

  The technical idea of using a hard brass material as an annealed material has hardly been studied. The present situation that the idea of using such an annealed material as it is did not give rise to the fact that an annealed material having fine crystal grains as an intermediate material to be rolled is handled and concealed as a manufacturing know-how among those skilled in the art. The reason is that only information about only a part of the manufacturing method could be obtained from each other, but this is not the only reason. In order to distribute brass materials as equivalent to H materials in the market, it is not enough to pursue only the matching of strength, simply by clearing the mechanical properties described in the JIS standard, molding processability, etc. As long as other characteristics that are not found in conventional brass materials cannot be produced, there was a reason that the product was not marketable enough to be widely accepted in the market as a new product.

JP 2004-292875 A Copper Products Data Book, Japan Brass Association, page 18

  In view of the current situation as described above, it has the same strength as the H material specified in JIS C2600, JIS C2680, and JIS C2720, and has the 180-degree contact bending process, the burring process, the overhang process, and the deep and fine protrusions by pressing. Naturally, there is a demand for a brass material having good forming workability with high processing reliability in strong processing such as forming.

  Moreover, if it is brass and has the same level of stress corrosion cracking resistance as that of the brass, its use range will be expanded rapidly, and the technical development received by the market will be extremely large.

  Furthermore, unlike the technique disclosed in Patent Document 1, the present invention is not limited to thin parts, but can be easily applied to thick parts, and includes fine crystals in as few steps as possible using conventional manufacturing equipment. If it can be made reinforced brass, it will be possible to supply low-cost, high-quality reinforced brass products to the market.

  From the above, the present invention has the same strength as the H material specified in JIS C2600, JIS C2680, and JIS C2720, and at the same time, good molding processability and good stress corrosion resistance that can withstand the above-mentioned strong processing conditions. It aims at providing the hard alpha brass material provided with a crackability, its manufacturing method, etc.

  Therefore, in order to achieve the above-described object, hard α brass obtained for the first time by employing a manufacturing method described later is employed.

Hard α brass according to the present invention: The hard α brass according to the present invention is an α brass composed of 71.5 wt% to 62.0 wt% of copper and unavoidable impurities and the balance consisting of zinc, and has a tensile strength of 451 MPa. It is characterized by having a stress-corrosion-cracking performance with a stress-corrosion-breaking time of 6 hours or more, and having a forming processability of -519 MPa, an Erichsen value of 8.5 or more.

  And it is preferable that the above-mentioned hard alpha brass has an average crystal grain diameter of 1 micrometer-2 micrometers.

Manufacturing method of hard α brass: The manufacturing method of the hard α brass according to the present invention can be broadly classified into three manufacturing methods. Hereinafter, it classifies as the 1st manufacturing method-the 3rd manufacturing method.

  The first production method is a production method of hard α brass characterized by performing a recrystallization annealing treatment after cold rolling an α brass plate material having an arbitrary particle size at a processing rate of 83% or more.

  The second production method is characterized in that a hard brass is characterized in that an α brass plate material having an average crystal grain size adjusted to 1 μm to 2 μm is cold-rolled at a processing rate of 20% to 82% and then subjected to a recrystallization annealing treatment. It is a manufacturing method of alpha brass.

  The third production method is characterized in that a hard brass is characterized in that an α brass plate whose average crystal grain size is adjusted to 3 μm to 6 μm is cold-rolled at a processing rate of 70% to 82%, and then recrystallized and annealed. It is a manufacturing method of alpha brass.

  The hard α brass according to the present invention has the same strength as the H material specified in JIS C2600, JIS C2680, and JIS C2720, and at the same time has good moldability that can withstand the above-mentioned strong working conditions and is equivalent to the brass. It will have good stress corrosion cracking resistance.

  In addition, the hard α brass according to the present invention can be used in applications where a material equivalent to a 1 / 2H material defined in any one of JIS C2600, JIS C2680, and JIS C2720 is used after being thinned.

  In addition, in the case of any of the first to third manufacturing methods described above, the hard α brass according to the present invention is finally subjected to recrystallization annealing, and the hard according to the present invention as an annealed material. It is characterized in that α brass is produced. According to such a manufacturing method, depending on the crystal grain size before the cold rolling process, the recrystallization is performed so that the cold rolling process is performed at a predetermined processing rate and then the desired crystal grain size is obtained. Only the points to be annealed require strict control, and since there are few control points and the process can be short, the hard α brass according to the present invention can be produced inexpensively and efficiently.

  Hereinafter, the form regarding the hard alpha brass which concerns on this invention, the manufacturing method of the hard alpha brass, and an Example are demonstrated.

Form of hard α brass: The hard α brass according to the present invention is an α brass composed of 71.5 wt% to 62.0 wt% of copper and unavoidable impurities and the balance consisting of zinc, and has a tensile strength of 451 MPa to 519 MPa. It is characterized in that it has molding workability with an Erichsen value of 8.5 or more, and has stress corrosion cracking resistance with a stress corrosion cracking break time of 6 hours or more.

  Here, the composition of the hard α brass is composed of zinc except for 71.5 wt% to 62.0 wt% of copper and unavoidable impurities. That is, those skilled in the art can easily understand, but it is within the range of the composition of JIS C2600, JIS C2680, and JIS C2720. Therefore, as long as attention is paid only to this composition, it cannot have any technical characteristics.

  That is, the physical characteristics of the hard α brass according to the present invention are that the properties of tensile strength, molding processability, and stress corrosion cracking resistance are simultaneously in a favorable range. First, the “tensile strength” will be described. The tensile strength in the range of 451 MPa to 519 MPa has the same strength as the tensile strength range of the H material specified in JIS C2600, JIS C2680, and JIS C2720. I mean. This is because if the tensile strength is less than 450 MPa, it is a level equivalent to a 1 / 2H material defined in the JIS standard, and the strength is insufficient. On the other hand, when the tensile strength exceeds 520 MPa, the material has physical properties equivalent to the EH material defined in JIS standards, and the deterioration of the molding processability becomes remarkable.

  And, regarding the moldability of the hard α brass according to the present invention, “Ericsen value” is mainly adopted. And this Erichsen value is 8.5 or more is a standard with good moldability. Regarding the measurement of Erichsen value, the influence (plate thickness dependence) due to the thickness of the sample is small, and it can be said that the evaluation is highly reliable. In the evaluation of the formability using the Eriksen value, if the Eriksen value is 10 or more, it is determined that light deep drawing can be performed. And if it is 9 or more, it will be judged that 180 degree | times contact | adherence bending is possible. In the present invention, strong processing (severe processing) means that the material partially having a thick portion is subjected to 180-degree adhesion bending processing, burring processing or overhang processing is performed regardless of the material thickness, and the press is deeply fine. For example, it is possible to determine that an Erichsen value of at least 8.5 or more is necessary in order to determine that the moldability required for such strong processing is provided.

  Furthermore, it is possible to simply adopt the “180-degree adhesion bending test” as one criterion for forming processability. Here, in order to determine that the moldability is good, a quality that does not cause any cracks is required even when the 180-degree contact bending test is performed. Therefore, the criterion for forming processability is whether or not cracking occurs when a 180-degree contact bending test is performed. The 180-degree close contact bending test mentioned here is a test that can be easily understood by those skilled in the art, and therefore detailed description thereof will be omitted, and only the method used for the experiment in the examples will be described. .

  Furthermore, stress corrosion cracking resistance will be described. In the present invention, in the stress corrosion cracking resistance evaluation test, the sample 1 processed into a small tensile test piece shape as shown in FIG. Then, as can be understood from FIG. 2, a plastic bag 2 of an appropriate size such as vinyl is prepared, and an insertion opening 3 through which the sample 1 can be passed is provided at the bottom of the plastic bag 2. Then, as shown in FIG. 2, the sample 1 is passed through the insertion opening 3 at the bottom of the plastic bag 2. In this state, the upper opening portion and the insertion opening portion 3 of the plastic bag 2 are fixed to the body portion 4 of the sample 1 by using a detachable member 7 (such as a rubber band). At this time, a certain amount of slack is given to the lower part of the plastic bag 2, and an appropriate amount of 18 wt% ammonia water 5 is put into the slack part of the plastic bag 2 as shown in FIG. Make sure that ammonia water is not in direct contact. Next, a predetermined weight 6 is hung on the lower part of the sample 1, and the time until breakage is measured with a time-lapse counter. The rupture time obtained by the measurement at this time is obtained as an appropriate numerical value by performing measurement a plurality of times or changing the load within a certain range. In this method, when the applied static stress is set to 50 MPa, the rupture time as a criterion for the stress corrosion cracking resistance is 1 hour for a general kind of brass, 6 to 20 hours for 85/15 brass, 90/10 It is about 60 hours with a red lead. Therefore, when expressing that the stress corrosion cracking property is excellent, the fracture time is 6 hours or more.

  In the case of a metal material, the mechanical properties and the like as described above are mostly determined by their crystal characteristics. In particular, in order to improve the moldability, the crystal grain size is generally increased by increasing the annealing temperature to obtain a high Erichsen value, or the temper rolling ratio for an annealed material having the same crystal grain size is increased. A method of obtaining a high Erichsen value by lowering is adopted. In contrast, the inventors of the present invention have been studying various physical properties of brass materials having fine crystal grains, and brass having fine crystal grains has a high formability without increasing the crystal grain size. I came up with the idea. Of course, it is known that a material with fine crystal grains has high strength. However, a method for simultaneously achieving high strength and good moldability has not been clarified. That is, in order to obtain a hard α brass that simultaneously establishes high strength and good moldability, the above-described tensile strength is provided in order to achieve both predetermined tensile strength and moldability. Therefore, it is desirable that the average crystal grain size is 3 μm or less. In addition, most of the hard α brass according to the present invention can be stably provided with an average crystal grain size in the range of 1 μm to 2 μm by employing the manufacturing method described later.

  The hard α brass according to the present invention described above is suitably used for electronic parts and mechanical parts.

Form of Manufacturing Method of Hard α Brass: As described above, the manufacturing method of the hard α brass according to the present invention can be classified as a first manufacturing method to a third manufacturing method. Therefore, it classify | categorizes into these and demonstrates below. First, it should be clearly noted that if a plate material other than those obtained by cold rolling is used in the conditions described as the first to third manufacturing methods described below, the subsequent recrystallization conditions can be adjusted. However, it becomes a mixed grain, and a desired crystal grain size cannot be obtained. On the other hand, if the conditions specified in the first manufacturing method to the third manufacturing method are satisfied, the high forming workability and the stress corrosion cracking resistance that are not conventionally obtained in the rolling annealing process once or twice. Hard α brass with the same strength as H material can be manufactured.

  The first production method is a production method of hard α brass characterized by performing a recrystallization annealing treatment after cold rolling an α brass plate material having an arbitrary particle size at a processing rate of 83% or more. Here, "alpha brass plate material of any particle size" is described as a concept including the case of a hot rolled material after continuous casting and hot rolling that are generally performed, and special crystal grains It is stated that it is not necessary to limit the diameter.

  And in the case of the board | plate material of arbitrary particle sizes, it cold-rolls with the process rate of 83% or more. That is, for any grain size, if cold rolling is performed at a processing rate of 83% or more, subgrains of about 1 μm can be introduced into the crystal by strong processing, and a uniform structure can be obtained. can get. And the presence of this subgrain makes it possible to obtain a fine recrystallized state. For example, a plate material having an average crystal grain size of 0.1 mm to 0.2 mm that has been subjected to hot rolling in a laboratory, or a plate material having an average crystal grain size of 25 μm that has been dynamically recrystallized at the production site, When strong processing is performed at a processing rate of 83% or more and recrystallization is performed under a predetermined condition, mixed grains are not generated, and crystal grains having an average crystal grain size of 3 μm or less are obtained. Therefore, if a processing rate of less than 83% is adopted for a plate material having a relatively large crystal grain size, the introduction of subgrains into the crystal becomes non-uniform, and the recrystallized structure is subject to recrystallization conditions. Even if it adjusts, generation | occurrence | production of a mixed grain becomes remarkable and a crystal grain of 3 micrometers or less as an average crystal grain diameter cannot be obtained. In addition, although the upper limit of the processing rate used for cold rolling is not prescribed | regulated, it can be judged that about 92% of a processing rate is an upper limit, considering the defect incidence, production efficiency, etc. of a crack.

  Next, although described as “recrystallization annealing treatment”, it is described as a concept including the case where one or more intermediate recrystallization annealing is performed before the final recrystallization annealing. . When such an intermediate recrystallization annealing is performed a plurality of times, it is usual to provide a rolling process step or other plastic deformation step between the recrystallization annealing and the recrystallization annealing. In consideration of the plate thickness and processing rate during the intermediate annealing, the crystal grain size formed by the intermediate recrystallization annealing is controlled. And the final recrystallization annealing is a required characteristic for the hard α brass obtained as a result of the final recrystallization annealing. (I) The tensile strength is in the range of 451 MPa to 519 MPa, (ii) The average crystal grain size is 1 μm to 2 μm. Recrystallization temperature and recrystallization so as to satisfy the following conditions: (iii) molding processability with an Erichsen value of 8.5 or more, and (iv) stress corrosion cracking resistance with a stress corrosion cracking rupture time of 6 hours or more. Recrystallization conditions such as time, recrystallization atmosphere, rolling treatment between the recrystallization annealing treatment and the recrystallization annealing treatment may be determined. However, if the limitation is possible, it is preferable to employ the continuous annealing method because a more uniform recrystallized structure can be obtained. And although the furnace temperature at this time is influenced by the capability of a furnace, it is preferable to employ | adopt the recrystallization temperature of the range of about 350 to 650 degreeC. In addition, the concept regarding this recrystallization annealing is the same also in the following 2nd manufacturing methods and 3rd manufacturing methods. As described above, the hard α brass according to the present invention can be manufactured.

  The second production method is characterized in that a hard brass is characterized in that an α brass plate material having an average crystal grain size adjusted to 1 μm to 2 μm is cold-rolled at a processing rate of 20% to 82% and then subjected to a recrystallization annealing treatment. It is a manufacturing method of alpha brass. This second production method was “alpha brass plate material having an arbitrary particle size” in the first production method, whereas “α brass plate material having an average crystal grain size adjusted to 1 μm to 2 μm” as the original plate material. When the average crystal grain size is found to be in the range of 1 μm to 2 μm, it has been clarified that a processing rate of less than 83% can be employed in cold rolling. This is because if it is known that the crystal grain size of the original plate material has already been refined, excessive strong processing is unnecessary and the production cost can be reduced. Further, even if the average crystal grain size of the plate material is in the range of fine grain size of 1 μm to 2 μm from the beginning, the cold rolling process is performed once by adopting a processing rate of 20% or more, more preferably 40% or more. It is preferable from the viewpoint of uniformly introducing subgrains of about 1 μm into the crystal. As a result, a uniform and fine recrystallized state can be obtained by recrystallization annealing of this structure. Therefore, in the second manufacturing method, if the processing rate during cold rolling is less than 20%, it is difficult to uniformly introduce subgrains of about 1 μm into the crystal structure of the α brass sheet. On the other hand, if the processing rate in the cold rolling process exceeds 82%, the processing rate is the same as that in the first manufacturing method and lacks rationality. In this manner, the hard α brass according to the present invention can be manufactured.

  The third production method is characterized in that a hard brass is characterized in that an α brass plate whose average crystal grain size is adjusted to 3 μm to 6 μm is cold-rolled at a processing rate of 70% to 82%, and then recrystallized and annealed. It is a manufacturing method of alpha brass. This third manufacturing method is “α brass plate material having an average crystal grain size adjusted to 3 μm to 6 μm”, whereas “α brass plate material having an arbitrary particle size” was used in the first manufacturing method. That is, when the average crystal grain size of the original plate material is found to be in the range of 3 μm to 6 μm, it is clarified that a processing rate of less than 83% can be adopted in cold rolling. This is the same as in the case of the second manufacturing method. If it is known that the crystal grain size of the original plate is at a certain level, excessive strong processing is unnecessary and the production cost can be reduced. is there. In the case of the third production method, since the initial average crystal grain size is in the range of 3 μm to 6 μm, subgrains of about 1 μm must be uniformly introduced into the crystal structure by cold rolling. Otherwise, a uniform and fine recrystallization state cannot be obtained by post-recrystallization annealing. Therefore, in the third manufacturing method, if the processing rate during cold rolling is less than 70%, it is difficult to uniformly introduce subgrains of about 1 μm into the crystal structure of the α brass sheet. On the other hand, if the processing rate in the cold rolling process exceeds 82%, the processing rate is the same as that in the first manufacturing method and lacks rationality. In this manner, the hard α brass according to the present invention can be manufactured.

  The hard α brass obtained as described above is applied to a part or a part using the 1 / 2H material in consideration of physical properties equivalent to the 1 / 2H material defined in any of JIS C2600, JIS C2680, and JIS C2720. Application to this is also possible. The hard α brass having the physical properties equivalent to the H material according to the present invention is used in the range where the conventional 1 / 2H material is used. That is, the hard α brass having the physical properties equivalent to the H material according to the present invention includes (i) a tensile strength of 451 MPa to 519 MPa, (ii) an average crystal grain size of 1 μm to 2 μm, and (iii) an Erichsen value of 8. It has a formability of 5 or more, and (iv) has stress corrosion cracking resistance with a stress corrosion cracking break time of 6 hours or more. By using this hard α brass, 1 / 2H material is used. It is possible to reduce the thickness of the parts or parts that have been used, and even if the thickness is reduced, the part strength equivalent to 1 / 2H material specified in any of JIS C2600, JIS C2680, and JIS C2720 can be obtained. Can be reduced.

  Hereinafter, the present invention will be described in more detail through examples. All brass ingots used in the examples were cast by a semi-continuous casting method at a foundry. Table 1 lists the composition of each ingot.

  Ingots 1 to 3 were hot-rolled, and after chamfering, they were cold-rolled at a processing rate of 85% to obtain a 1.8 mm base plate. The process so far is a general processing process conventionally performed. Thereafter, only the recrystallization annealing (indicated as “recrystallization annealing 1” in the table) was performed on the base plate obtained from the ingot 1 to obtain a sample 1. The other samples 2 to 5 were manufactured by subjecting the base plate to recrystallization annealing 1, performing cold rolling according to the processing rate according to the present invention, and performing recrystallization annealing 2. Table 2 shows the manufacturing conditions for each sample so that the manufacturing conditions at this time can be seen at a glance. All production was carried out on-site, and the annealing was performed using a continuous annealing method. Among Sample 1 to Sample 5, Sample 3 and Sample 4 are different in plate passing speed when performing continuous annealing at a temperature of 420 ° C. That is, the sample 4 is passed about 33% faster with reference to the passing speed of the sample 3.

  Characteristics of hard α brass of Sample 1 to Sample 5 obtained under the manufacturing conditions shown in Table 2 and characteristics of commercially available products (H material described as Comparative Examples 1 to 3 and tempering of 1 / 2H material) The rolling rate is in the range of 1% to 25%).

Comparison of Examples and Comparative Examples Based on Table 3: First, the tensile strength is compared. From Table 3, it can be seen that the tensile strength of each sample of Examples (Sample 1 to Sample 5) according to the present invention is in the range of 451 MPa to 519 MPa. On the other hand, the tensile strengths of Comparative Examples 1 to 3 are in the range of 410 MPa to 499 MPa. Therefore, it can be understood that the tensile strength of each sample which is the hard α brass according to the present invention has a tensile strength equivalent to the H material specified in any of JIS C2600, JIS C2680, and JIS C2720.

  Next, the contrast between hardness and crystal grain size will be described. In general, when processing is performed by a physical method such as forging, work hardening occurs, and crystal grains are deformed to increase hardness. However, the crystal grain sizes of Comparative Examples 1 to 3 are 6 μm to 17 μm, and the hardness (Vickers hardness) is 106 Hv to 155 Hv. On the other hand, the crystal grain sizes of Sample 1 to Sample 5 are 1.2 μm to 2.3 μm, and the hardness (Vickers hardness) is 138 Hv to 159 Hv. FIG. 1 shows a metallographic micrograph of Sample 1. In this case, the average crystal grain size is 1.9 μm. That is, although the crystal grain sizes of Samples 1 to 5 are smaller than those of Comparative Examples 1 to 3, the hardness (Vickers hardness) is approximately the same. That is, the hard α brass according to the present invention has many crystal grain boundaries that block the sliding surface when plastically deformed, and the strength becomes high. In addition, the excellent formability of the hard α brass according to the present invention is not simply due to the presence of recrystallized grains having a low dislocation density, but because there are many fine crystal grains having various orientations. This is thought to be caused by inhomogeneous deformation.

  The evaluation test of molding processability supports the understanding from the comparison between the hardness and the crystal grain size. Here, the 180-degree close contact bending test and the Eriksen test were used for formability evaluation. First, the results of the 180-degree contact bending test are compared. In this 180-degree contact bending test, the bending axis is taken in parallel with the rolling direction (Bad way bending), 180-degree contact bending is performed, the outer surface is observed, and the findings are described as inspection results. Regarding this test, the thicker the brass plate, the more severe the test conditions. Regarding the plate thickness, none of the samples and the comparative example have the same thickness, but the thicknesses of the sample 1 and the sample 2 are thicker than those of the comparative example 1, and the other samples 3 to 5 are compared. The thickness is the same as in Example 2 and Comparative Example 3. However, as can be seen from Table 3, in the case of the H material products of Comparative Example 1 and Comparative Example 2, all occurrences of microcracks are observed when the 180 ° adhesion bending test is performed. On the other hand, even if wrinkles were observed in Samples 1 to 5 according to the present invention, it was not possible to confirm until the occurrence of cracks. And this shows the performance equivalent to the comparative example 3 which is a 1 / 2H material. Therefore, it can be judged that Sample 1 to Sample 5 according to the example are superior in molding processability to Comparative Examples 1 and 2 which are H materials and have the same molding processability as 1/2 H materials.

  In addition, in order to determine the moldability, an Erichsen value that is an index of the stretchability was measured. The Eriksen test uses the A method which is usually performed manually, but the sample 1 was performed by the B method using hydraulic pressure because the plate 1 is thick. The original Erichsen test is used for evaluation by measuring the height at which cracks start to occur. In the case of Sample 1, since it is thick, the Eriksen value shows a high value of 9.2. Due to the law, the occurrence of cracks is not clearly recognized. If this Erichsen value exceeds 10, it is determined that the moldability is capable of drawing. When other Erichsen values are judged from Table 3, Sample 2, Sample 4, and Sample 5 according to the examples exceed Erichsen values of 10.0. Sample 3 also shows a high value of 9.6, even if the Erichsen value does not exceed 10.0. On the other hand, the Erichsen value of Comparative Example 1 and Comparative Example 2 which are H materials is in the range of 7.4 to 8.2, which is lower than the Erichsen value of each sample according to the example, and is inferior in molding processability. it can. In addition, the comparative example 3 is a 1 / 2H material, this Erichsen value is 10.4, and it can be understood that the molding processability of the hard α brass according to the present invention according to the example is at an equivalent level. . Specifically, when the sample 4 having the same Erichsen value was compared with the comparative example 3, the tensile strengths were 499 MPa (sample 4) and 410 MPa (comparative example 3). Indicates about 1.2 times the strength of Comparative Example 3. And the Erichsen value of the sample 4 and the comparative example 3 is equivalent. This is because the hard moldability according to the present invention, which shows equivalent molding processability when a 1 / 2H material had to be used in the prior art, is required because of its excellent molding processability characteristics. It becomes possible to select brass. In such a case, since the hard α brass according to the present invention has higher strength than the 1 / 2H material, it is possible to simultaneously achieve a reduction in material thickness and cost reduction as long as the same strength is required.

  Then, the results of an evaluation test for stress corrosion cracking resistance will be compared and described. As described above, the stress corrosion cracking resistance can be evaluated as being excellent when the rupture time exceeds 6 hours. As can be seen from Table 3, the break times of Comparative Example 2 and Comparative Example 3 are 1.1 hours and 1.3 hours. On the other hand, the rupture time of Sample 1 to Sample 5 according to the present invention is 6 hours to 17 hours, and it can be seen that extremely good stress corrosion cracking resistance is exhibited.

  Further, as apparent from Table 2, with respect to Sample 2, with respect to an α brass sheet having an initial crystal grain size of 1.9 μm before cold working, the cold rolling working rate was set to 56%, and recrystallization annealing was performed at 550. Done at ℃. In contrast, (1) for the same initial crystal grain size of 1.9 μm α brass plate material, the processing rate of cold rolling was laboratory set to 20% and the plate thickness of 1.4 mm, and using a salt bath. When the crystal annealing temperature is set to 440 ° C. (sample 6), and (2) the same initial crystal grain size of 1.9 μm α brass plate, the thickness is 1.1 mm, and the cold rolling processing rate is 40%. A sample was prepared for the case where the recrystallization annealing temperature using a salt bath was 420 ° C. (sample 7), and a more appropriate processing rate was determined. The crystal grain sizes and mechanical properties of Sample 6 and Sample 7 at this time are listed in Table 4.

  According to Table 4, it can be understood that characteristics within a desired range can be obtained even when 20% of the processing is applied to an α brass plate material having an initial crystal grain size of 1.9 μm. However, the strength of sample 6 from the viewpoint of tensile strength and hardness is relatively lower than that of sample 7, and the crystal grain size is also large. Therefore, it can be understood that it is more preferable to apply a processing rate of 40% or more.

  The hard α brass according to the present invention has the same strength as the H material specified in JIS C2600, JIS C2680, and JIS C2720, and at the same time has good moldability that can withstand the above-mentioned strong working conditions and is equivalent to the brass. Has good stress corrosion cracking resistance. Therefore, it can be used even in an environment where the conventional H material cannot be used, and the range of use of brass products is expanded. Further, the hard α brass according to the present invention can be used for applications requiring molding workability equivalent to 1 / 2H material defined in any of JIS C2600, JIS C2680, and JIS C2720, and is comparable to H material. Because of its strength, it is possible to reduce the thickness and cost by reducing the thickness of parts and the like that have conventionally used 1 / 2H materials.

  In addition, the production of the hard α brass according to the present invention is characterized in that it is an annealed material that is finally subjected to recrystallization annealing to control the crystal grain size. This crystal structure is excellent in moldability because the crystal grain size is fine and the crystal grain orientations are varied. The manufacturing method according to the present invention only performs cold rolling at a predetermined processing rate according to the crystal grain size before cold rolling, and then performs recrystallization annealing so as to obtain a desired crystal grain size. Therefore, it is possible to produce a hard α brass according to the present invention at a low cost and efficiently because the crystal can be controlled strictly and the number of control points is small.

2 is a photograph of a crystal structure of a hard α brass of sample 1 taken with a metallographic microscope. It is a conceptual diagram which shows the measuring method at the time of measuring the fracture | rupture time used as a parameter | index of stress corrosion cracking resistance.

Explanation of symbols

1 Sample 2 Plastic bag 3 Insertion opening 4 Body 5 Ammonia water 6 Weight 7 Detachable member

Claims (5)

In α brass composed of 71.5 wt% to 62.0 wt% of copper and unavoidable impurities and the balance consisting of zinc,
Hardness characterized by having a tensile strength of 451 MPa to 519 MPa, an Erichsen value of 8.5 or more, and a stress corrosion cracking resistance performance of 6 hours or more. α brass. The hard α brass according to claim 1, wherein the average crystal grain size is 1 μm to 2 μm. 3. The production of hard α brass according to claim 1, wherein the α brass plate material having an arbitrary particle size is cold-rolled at a processing rate of 83% or more, and then recrystallized and annealed. Method. The α-brass plate material having an average crystal grain size adjusted to 1 μm to 2 μm is cold-rolled at a processing rate of 20% to 82%, and then subjected to a recrystallization annealing process. The manufacturing method of the hard alpha brass of description. The α-brass plate material having an average crystal grain size adjusted to 3 μm to 6 μm is cold-rolled at a processing rate of 70% to 82%, and then subjected to a recrystallization annealing process. The manufacturing method of the hard alpha brass of description.