JP4191159B2 - Titanium copper with excellent press workability - Google Patents

Description

  The present invention relates to a copper alloy used for a connector material and the like, and provides a technique for producing titanium copper having both high press strength and bending workability while having high strength.

Titanium copper forms a supersaturated solid solution by solution treatment, and when it is aged at low temperature from that state, a modulated structure that is a metastable phase develops and hardens significantly at some stage of its development stage It is used for connector materials and the like because it has strength next to beryllium copper in copper alloys and has stress relaxation properties that surpass beryllium copper. In recent years, the demand for titanium copper has been increasing, but there is a demand for higher strength while having excellent bending workability. In order to meet this need, various researches and developments related to further strengthening of titanium copper have been conducted.
For example, Patent Document 1 proposes a technique of adding Cr, Zr, Ni, and Fe to titanium copper. Patent Document 2 also proposes a technique of adding Zn, Cr, Zr, Fe, Ni, Sn, In, P, and Si to titanium copper.

JP-A-6-248375 JP 2002-356726 A

  However, despite the fact that titanium copper is an alloy that is particularly susceptible to wear of the mold among copper alloys, the third element group (Fe, Co, Ni, Si, Cr, V, Nb, Zr, B or P) is added, and in the prior art aiming at high strength by precipitation of the second phase containing those components, the precipitate itself becomes hard. The drawback is that the mold is more easily worn. That is, if the titanium copper thus strengthened is continuously pressed, the mold is worn quickly, and the processing accuracy is lowered. For this reason, in the processing of precision parts such as narrow pitch connectors, it is necessary to increase the frequency of changing the mold or avoid the use of materials for such applications.

  Therefore, an object of the present invention is to improve the press workability in titanium copper enhanced by adding a third element, and further, excellent press workability by realizing excellent bending workability. It is to provide titanium copper.

The inventors have intensively studied that the stress distribution of the material during shearing is affected by the crystal orientation of the material, and as a result, found that the crystal orientation can be controlled and press punchability can be improved. . In addition, as a result of investigating the appropriate distribution form of the second phase particles, focusing on the presence of coarse second phase particles and the non-uniformity of the structure causing the deterioration of the bending workability, It has been found that in order not to deteriorate the bending workability while contributing to the improvement, the second phase particles need to be distributed as finely and evenly as possible within the grains, not at the grain boundaries.
Furthermore, if the composition is a Cu—Ti—X system containing a third element (where X is a third element), it has been found that the growth is suppressed and the fine dispersion is facilitated.

That is, the present invention is as follows.
(1) In a copper-based alloy containing 2.0 to 4.0% by mass of Ti and 0.05 to 0.50% by mass of Fe with the balance being Cu, the other impurity elements are 0.01% in total. %, And the X-ray diffraction intensity ratio is I (311) / I (111) ≧ 0.5.

(2) A total of 0.05 to 4.0% by mass of Ti and Fe, and one or more of Co, Ni, Si, Cr, V, Nb, Zr, B, and P is 0.05 to In the copper base alloy containing 0.50% by mass and the balance being Cu, the other impurity elements are 0.01% by mass or less in total, and the X-ray diffraction intensity ratio is I (311) / I (111) ≧ A copper alloy characterized by being 0.5.

(3) 2.0 to 4.0% by mass of Ti and 0.05 to 0.50% by mass of one or more of Co, Ni, Si, Cr, V, Nb, Zr, B, and P In the copper-based alloy with the balance being Cu, the other impurity elements are 0.01% by mass or less in total, and the X-ray diffraction intensity ratio is I (311) / I (111) ≧ 0.5 Characteristic copper alloy.

(4) Of the second phase particles having an area of 0.01 μm ² or more observed by a cross-sectional microscope, the proportion of the composition being Cu—Ti—Fe based is 50% or more ( Titanium copper excellent in press workability as described in 1).

(5) Of the second phase particles having an area of 0.01 μm ² or more observed by a cross-sectional microscope, the ratio of the composition being Cu-Ti-X based is 50% or more ( Titanium copper excellent in press workability according to 2) to (3),
Here, X is any element of Fe, Co, Ni, Si, Cr, V, Nb, Zr, B, and P.

(6) The average particle diameter of the second phase particles having an area of 0.01 μm ² or more observed by a cross-sectional microscope is 2.0 μm or less, as described in (1) to (5) above Titanium copper with excellent press workability.

(7) The coefficient of variation Cv (standard deviation / average value) between the crystal grains of the average number density of the second phase particles having an area of 0.01 μm ² or more observed in each crystal grain by a cross-sectional microscope is 0.3. Titanium copper excellent in press workability according to the above (1) to (6), characterized in that:

  According to the present invention, in titanium copper, by optimizing the content of the third element group and optimizing the crystal orientation, it is possible to achieve excellent press punchability while having high strength, By controlling the two-phase particle distribution, good bending workability can also be realized. Therefore, the titanium copper of the present invention is a copper alloy that has high strength as a copper alloy used for a connector material and the like, and has excellent press workability in which press punchability and bending workability are compatible.

(1) Alloy composition In the present invention, Ti is 2 to 4% by mass. However, if Ti is less than 2% by mass, sufficient strength cannot be obtained. Conversely, if Ti exceeds 4% by mass, precipitates become coarse. Since it is easy, bending workability deteriorates. The most preferable range of Ti is 2.5 to 3.5% by mass.

  In the present invention, the addition of the third element group is specified, but the effect of these elements is that the crystal grains easily become coarse even if solution treatment is performed at a high temperature at which Ti is sufficiently dissolved by addition of a small amount. That is, a fine structure is obtained. In titanium copper, Fe has the highest effect. Co, Ni, Si, Cr, V, Nb, Zr, B, and P can also be expected to have an effect similar to Fe, and some of the added Fe may be Co, Ni, Si, Cr, V, Nb. , Zr, B, P can be substituted. Furthermore, the same effect can be seen by adding these elements alone, or two or more of these elements may be added in combination. When Fe and these elements are contained in a total of 0.01% by mass or more, the effect appears. On the other hand, if it exceeds 0.5% by mass, the solid solubility limit of Ti is narrowed and coarse second phase particles are easily precipitated, and the strength is improved, but the adverse effect that the bending workability is deteriorated becomes remarkable. . A more preferable content range of these third elements is 0.17 to 0.23 mass% in Fe, 0.15 to 0.25 mass% in Co, Ni, Cr, Si, V, and Nb, Zr, B , P is 0.05 to 0.10% by mass.

(2) Crystal orientation Generally, the higher the ductility, the better the bending workability, and the lower the ductility, the better the press punchability. Therefore, it has been considered difficult to achieve both bendability and press punchability.
On the other hand, when cold rolling is performed at a high workability in the copper alloy manufacturing process, a rolling texture develops and I (110) becomes strong. If recrystallization annealing is performed in this state, a recrystallization texture develops and I (100) becomes stronger. The material after cold rolling has poor ductility, and conversely, the material after recrystallization annealing is soft and easy to stretch. From this relationship, in the prior art, there are many examples that pay attention to the relationship between I (100) and I (110), and in order to improve the bending workability, I (100) is strongly defined with respect to I (110). On the other hand, in order to improve the press punchability, one that strongly defines I (110) with respect to I (100) has been proposed.

In the present invention, focusing on the relationship between I (311) and I (111), the following findings have been found. There is no conventional example that focuses on the relationship between I (311) and I (111).
When I (311) develops compared to I (111), as shown in FIG. 1A, the crack generation angle at the time of shearing is close to 90 ° with respect to the material surface, which leads to fracture. The development of cracks up to is smooth. This phenomenon is effective when I (311) / I (111) ≧ 0.5, but does not affect the strength and ductility of the material. On the other hand, as shown in FIG. 1B, when the crack generation angle deviates from 90 °, the plastic strain region of the material is expanded during the development of the crack, and the removal becomes worse. In addition, a secondary shear surface is also formed thereby, and the mold is likely to be worn. The present inventors have found a relationship in which only press punchability is improved without lowering ductility.

In the alloy system of the present invention, I (311) / I (111) ≧ 0.5, more preferably I (311) / I (111) ≧ 1.0, and even more preferably I (311). /I(111)≧1.5.
In addition, about the method of obtaining the predetermined crystal orientation of I (311) / I (111) ≧ 0.5, the (311) plane is finally obtained by cold rolling in a state where solute atoms are completely dissolved. Therefore, the solution treatment in the intermediate process is performed under the heat treatment conditions in which the second phase particles are completely dissolved.

(3) Composition composition and distribution form of second phase particles In the present invention, as a necessary condition for obtaining good bending workability, composition composition of second phase particles, average grain size, and number density between crystal grains Define variation.
In general, the second-phase particles include foreign inclusions such as furnace materials, reaction products generated during melting, crystallized products generated during solidification, and precipitates formed during annealing. However, in the alloy system targeted by the present invention, the second phase particles are mostly precipitates formed during the heat treatment.

  If the second phase particles are finely and evenly dispersed in the crystal grains, the second phase particles contribute to the improvement of the strength and the bending workability is also improved. If it becomes coarse or has a locally biased distribution, bending workability will be impaired. Specifically, the average particle size of the second phase particles exceeds 2 μm, or the coefficient of variation (standard deviation / average value) between crystal grains in the average number density of the second phase particles exceeds 0.3. If it is distributed, the bending workability will be significantly impaired. Here, the “particle diameter” refers to the equivalent circle diameter when the cross section is observed. “Circular equivalent diameter” is the diameter of a perfect circle having the same area.

  Therefore, in order to obtain a state in which fine second phase particles are uniformly dispersed in the crystal grains, heating is performed in a state where solute atoms are completely dissolved, and the solid solubility limit of the second phase particle composition is obtained. It is effective to perform the final solution treatment at a temperature immediately above. In general, when the homogeneous α phase is heated to the temperature of the boundary line with the second phase, the actual space fluctuates even in the equilibrium state, so the nucleation and annihilation of the second phase frequently occurs everywhere. Occur. At a temperature at which this phenomenon occurs, crystal grains are difficult to grow even if recrystallization occurs. Therefore, if the Cu-Ti-X phase (X is the third element) is just above the solid solubility limit, a Cu-Ti-X-based second phase particle is finely dispersed, whereby recrystallized grains are obtained. Also refines.

  Further, since the Cu-Ti-X second phase particles themselves are less likely to be coarser than the Cu-Ti second phase particles, among the second phase particles, the Cu-Ti-X type If the number of the second phase particles is 50% or more of the total number of the second phase particles, the above-mentioned desired state can be obtained in the second phase particle size and its distribution form, and fine recrystallized grains can get. The Cu-Ti-X second phase particles are less likely to be coarser than the Cu-Ti second phase particles, whereas the latter occurs only in the diffusion of Ti in the growth of the second phase particles. The former is due to the need for diffusion of both Ti and X. This property is effective even at a low temperature, and the Cu—Ti—X-based second phase particles are not easily coarsened even in the aging treatment in the final step. For this reason as well, it is preferable to make the second phase particle composition as much as possible in the Cu—Ti—X system in the final solution treatment.

However, in the state where the second phase particles are already precipitated, no matter what the final solution treatment is performed, the existing second phase only grows and only fine ones are uniformly dispersed. A state cannot be obtained.
Therefore, in the heat treatment step before the final solution treatment, all solute atoms must be dissolved. At this point, the crystal grains may be coarsened and do not affect the final crystal grain size. After cold rolling in a state where solute atoms are completely in solid solution, a fine and homogeneous crystal structure can be obtained by simultaneously proceeding with recrystallization and precipitation of second phase particles in the final solution treatment. is there.

(4) The basic process for making the alloy of the present invention from the above manufacturing method is as follows:
“Sufficient solution treatment (primary solution treatment) → cold rolling (intermediate rolling) → solution treatment immediately above the solid solution limit of the second phase particle component to be precipitated (final (secondary) solution treatment Processing) → temper rolling (final rolling) → aging ”
It is.
“Primary solution treatment” refers to a solution treatment before intermediate rolling before final rolling. After melting to the specified components, casting, hot rolling, and cold rolling and annealing are appropriately repeated until the thickness reaches a predetermined thickness, and the first solution treatment is performed. A primary solution treatment may be performed.
Further, “secondary solution treatment” refers to a solution treatment before the final rolling, and corresponds to the above-mentioned final solution treatment, and is hereinafter also expressed as a final solution treatment.

The steps will be sequentially described as embodiments of the present invention.
1) Ingot production process 0.01 to 0.50 mass% of one or more of Fe, Co, Ni, Si, Cr, V, Nb, Zr, B, and P as a third element group in an appropriate amount of Cu After adding and maintaining sufficiently, 2-4 mass% of Ti is added.
In order to eliminate the undissolved residue in order for the third element group to act effectively, it is necessary to keep it sufficiently, and since Ti is more easily dissolved in Cu than the third element group, it may be added after the third element group is dissolved. .
Oxide inclusions generated here adversely affect the strength and bending workability of the material. Therefore, in order to prevent this, melting and casting are preferably performed in a vacuum or in an inert gas atmosphere.

2) Process after the ingot manufacturing process After this ingot manufacturing process, it is desirable to perform homogenization annealing for 3 hours or more at 900 degreeC or more. At this time, it is desirable to completely eliminate solidification segregation and crystallized substances generated during casting, in order to finely and uniformly disperse the precipitation of the second phase particles in the solution treatment described later. It is also effective in preventing grain. Thereafter, hot rolling is performed, and cold rolling and annealing are repeated to perform a solution treatment. Since the second phase particles are formed when the temperature is low even during annealing, the second phase particles are formed at a temperature at which they are completely dissolved. If it is normal titanium copper to which the third element group is not added, the temperature may be 800 ° C., but the titanium copper to which the third element group is added preferably has a temperature of 900 ° C. or higher. At that time, the heating rate and the cooling rate are increased as much as possible so that the second phase particles are not precipitated. By cold rolling in a state where the solute atoms are completely dissolved, the (311) plane is finally developed. Furthermore, in cold rolling immediately before the solution treatment, the higher the degree of processing, the more uniform and fine the precipitation of the second phase particles in the solution treatment.

3) Final solution treatment If the solution is rapidly heated to the temperature of the solid solution limit of the second phase particle composition and the cooling rate is increased, the generation of coarse second phase particles is suppressed. Further, the shorter the heating time at the solid solution temperature, the finer the crystal grains can be made. Since the second phase particles generated at the grain boundary at this point grow with the final aging, the second phase particles at this point are as small as possible and preferably smaller.

4) Final cold rolling / final aging treatment After the solution treatment, cold rolling and aging treatment are performed. For cold rolling, a working degree of 25% or less is desirable. This is because the higher the degree of processing, the easier the grain boundary precipitation occurs in the next aging treatment.
About aging treatment, precipitation to a grain boundary can be suppressed, so that it is low temperature. Even under conditions where the same strength can be obtained, grain boundary precipitation can be suppressed on the low temperature long time side than on the high temperature short time side. At 420 to 450 ° C., which is an appropriate range in the prior art, the strength is improved as aging progresses, but grain boundary precipitation is likely to occur, and bending workability is reduced even by slight overaging. Although the appropriate aging conditions vary depending on the additive element, the heating time may be as long as 360 ° C. × 24 h at a temperature as low as 380 ° C. × 3 h.

Next, examples will be described.
When manufacturing the copper alloy of the present invention example, Ti, which is an active metal, is added as the second component, so a vacuum melting furnace was used for melting. In addition, in order to prevent unexpected side effects due to mixing of impurity elements other than the elements defined in the present invention, raw materials having a relatively high purity were carefully selected and used.

  First, for Examples 1 to 7 and Comparative Examples 8 to 12, the main raw materials Cu and Ti and additive elements (Fe, Co, Ni, Cr, Si, V, Nb, Zr, B and P) were blended and dissolved. In order to eliminate the undissolved residue in order for the third element group to act effectively, Ti was added sufficiently. These were poured into a mold in an Ar atmosphere to produce about 2 kg of ingots.

  An antioxidant was applied to the ingot, dried at room temperature for 24 hours, heated at 950 ° C. for 12 hours and hot-rolled to obtain a plate having a thickness of 10 mm. Next, in order to suppress segregation, after applying an antioxidant again, it was heated at 950 ° C. for 2 hours and cooled with water. The reason for water cooling here is to make the solution as much as possible, and the reason why the antioxidant is applied is that the grain boundary oxidation and the internal oxidation in which the oxygen entering from the surface reacts with the additive element component to become inclusions are performed. This is to prevent as much as possible. Each hot-rolled sheet was cold-rolled to a thickness of 0.2 mm after being descaled by mechanical polishing and pickling. Thereafter, it is inserted into an annealing furnace capable of rapid heating, and the temperature of the second phase particle composition at the rate of temperature rise of 50 ° C./second (for example, the addition amount of Ti and Fe is 3% by mass, 0.00%, respectively). It was heated to 800 ° C. at 2% by mass, held for 2 minutes and then cooled with water. Then, pickling, descaling, and cold rolling to a plate thickness of 0.15 mm, aging in an inert gas atmosphere, to obtain a test piece of the invention example. For the test piece of the comparative example, no. 8-11 are component adjustment, No.8. Nos. 12 to 14 are obtained by adjusting the conditions of the intermediate solution treatment step which is an important step in the present invention.

First, for each test piece, the diffraction intensities of (111) and (311) were determined by XRD, and I (311) / I (111) was determined.
Further, the distribution form of the second phase particles was evaluated using a field emission Auger electron spectroscopy analyzer (FE-AES) and an image processing apparatus linked thereto. That is, the number of all second phase particles having an area of 0.01 μm2 or more existing in the unit scanning field is measured, and the total number (S) and the composition of the second phase are Cu—Ti—Fe system or Cu—Ti—X system. The A value (Sx ÷ S × 100) was determined from the total of the particles (Sx). Similarly, the area of 5000 arbitrary second phase particles was averaged, and the equivalent circle diameter was defined as the average particle diameter D of the second phase particles. Further, for any 100 crystal grains from the population of crystal grains, a value (average number density) obtained by dividing the number of second phase grains present in each grain by the area of each crystal grain is obtained, and the variation The coefficient Cv (standard deviation ÷ average value) was determined. Table 2 shows I (311) / I (111), A value, D, and Cv of each test piece.

Next, a tensile test was performed to measure a 0.2% proof stress, and a W bending test was performed to measure an MBR / t value, which is a ratio of the minimum radius (MBR) at which cracks do not occur to the plate thickness (t).
The die wearability was evaluated by actually punching a fixed number of times with a continuous press and measuring the burr height and fracture surface ratio of the cut part, which varies depending on the wear state of the die. Here, the burr height is the height of the protrusion shown in FIG. 2, and the burr becomes higher as the mold is worn. Further, as the mold wears, the ratio of the shear plane shown in FIG. 2 increases, that is, the fracture surface ratio h ₂ / (h ₁ + h ₂ ) decreases.
Other press conditions were as follows.
Mold tool material: SKD11, clearance: 10 μm, stroke: 200 rpm FIG. 2 shows a mold set shape used for evaluation. The curvature of four corners is different in a square of about 5 mm on a side, and the curvature radii are 0.05 mm, 0.1 mm, 0.2 mm, and 0.3 mm, respectively. The smaller the radius of curvature, the easier it is to wear because stress concentration occurs during shearing. However, the smaller the radius of curvature is, the more difficult it is to observe because the cut surface shape varies. In addition, it is easier to observe the punched-out side and the punched-out side of the punched-out side. Considering the above, in this evaluation, the corner having a radius of curvature of 0.1 mm on the removal side was observed. In order to avoid factors other than the material affecting the press punchability, the difference between the materials became remarkable when punched without lubrication and punched 100,000 times, and the value at that time was adopted as the evaluation value. The burr height was measured with a laser displacement meter, and the fracture surface ratio was measured by cross-sectional observation with an optical microscope.

As is apparent from Table 3, in each of the inventive examples, the 0.2% yield strength is 850 MPa or more, the MBR / t value is 2.0 or less, and the fracture surface ratio after punching 100,000 times without lubrication is 0. 10 or more and the burr height is 40 μm or less, and it can be seen that high strength, excellent bending workability and press punchability are realized at the same time. Invention Example No. In 3-7, when the addition amount of Ti was within a particularly preferable range (2.5-3.5 mass%), the 0.2% proof stress was remarkably improved and became 900 MPa or more. Invention Example No. Other than 5, in the distribution form of the second phase particles, the A value representing the abundance ratio of the Cu—Ti—X-based particles, the average particle diameter D, and Cv representing the uniformity of the distribution position are preferable values. Bending workability is improved. In Invention Examples 1-2 and 5-7, since I (311) / I (111) is in a more preferable range, press workability is further improved.
Invention Example No. No. 5, since the addition amount of the third element is small in the distribution form of the second phase particles, the abundance ratio of the Cu—Ti—X-based particles is 50% or less, which is more than the bending workability than the other invention examples. Inferior.

On the other hand, Comparative Example No. In No. 8, since the addition amount of Ti is less than 2.0% by mass, sufficient 0.2% yield strength is not obtained. Conversely, Comparative Example No. In No. 9, since the addition amount of Ti exceeds 4.0% by mass or more, bending workability is deteriorated. Comparative Example No. No. 10 is inferior in strength and bending workability because the third element group defined in the present invention is not added. Conversely, Comparative Example No. In No. 11, since the total value of the added amount of the third element group exceeds 0.5 mass%, the second phase particles are precipitated more than necessary, and the bending workability is deteriorated. And in the solution treatment performed before intermediate cold rolling, comparative example No. No. 12 lowers the soaking temperature. No. 13 slows the heating rate. No. 14 is a slow cooling rate. Specifically, no. No. 12 has a soaking temperature of 800 ° C. The heating rate of No. 13 is 5 ° C./sec. The cooling rate of 14 was 30 ° C./sec. In any case, intermediate cold rolling is performed with Cu-Ti-X-based precipitates remaining, and finally, I (311) / I (111) is less than 0.5, and press punchability is improved. It is falling.

It is a conceptual diagram of the method of entering the crack which generate | occur | produces in press punching. It is explanatory drawing of the burr | flash which generate | occur | produces in press punching. The mold set shape used for evaluation is shown.

Claims (6)

In a copper-based alloy containing 2.0 to 4.0% by mass of Ti and 0.05 to 0.50% by mass of Fe with the balance being Cu, the other impurity elements are 0.01% by mass or less in total. Yes, X-ray diffraction intensity ratio is I (311) / I (111) ≧ 0.5 , and the ratio (MBR / t value) of the minimum radius (MBR) at which cracks do not occur in the W bending test to the thickness (t) Titanium copper excellent in mold wear resistance , characterized in that is 2 or less . 0.05-0.50 mass in total with 2.0-4.0 mass% of Ti and Fe, and also 1 or more types out of Co, Ni, Si, Cr, V, Nb, Zr, B, P In the copper-based alloy containing Cu and the balance being Cu, the other impurity elements are 0.01% by mass or less in total, and the X-ray diffraction intensity ratio is I (311) / I (111) ≧ 0.5 , Titanium copper excellent in mold wear resistance , characterized in that the ratio (MBR / t value) of the minimum radius (MBR) at which cracks do not occur in the W bending test to the plate thickness (t) is 2 or less . Of the second phase particles area 0.01 [mu] m ² or more is observed in cross-section speculum, according to claim 1 or 2 percentage the composition is Cu-Ti-Fe system is characterized in that 50% or more Titanium copper excellent in mold wear resistance described in 1 . The gold resistance according to any one of claims 1 to 3, wherein an average particle diameter of the second phase particles having an area of 0.01 µm ² or more observed by a cross-sectional microscope is 2.0 µm or less. Titanium copper with excellent mold wear . The coefficient of variation Cv (standard deviation / average value) between crystal grains is 0.3 or less with respect to the average number density of second phase particles having an area of 0.01 μm ² or more observed in each crystal grain by a cross-sectional microscope. 5. Titanium copper excellent in mold wear resistance according to any one of items 1 to 4 . Copper-based alloy containing 2.0 to 4.0% by mass of Ti and 0.05 to 0.50% by mass of Fe, the balance being Cu, and other impurity elements being 0.01% by mass or less in total Solution treatment (primary solution treatment), cold rolling, solution treatment (final solution treatment) immediately above the solid solution limit of the precipitated second phase particle component, processing A method for producing titanium copper having excellent mold wear resistance according to claim 1 or 2 by performing final rolling and aging treatment at a degree of 25% or less .

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