JP6368518B2 - Cu-Ti copper alloy sheet, method for producing the same, and energized component - Google Patents

Description

  The present invention relates to a Cu—Ti-based copper alloy plate material suitable for current-carrying parts such as connectors, lead frames, relays, and switches, and more particularly to a plate material with improved variation in bending workability, and a method for manufacturing the same. Moreover, it is related with the electricity supply component which used the copper alloy board | plate material for the material.

  Materials used for current-carrying parts such as connectors, lead frames, relays, and switches that make up electrical and electronic parts must have high strength to withstand the stress applied during assembly and operation of electrical and electronic equipment. Is done. Moreover, since electric / electronic parts are generally formed by bending, excellent “bending workability” is required. Furthermore, in order to ensure contact reliability between electrical and electronic components, it is also required to have excellent durability against a phenomenon (stress relaxation) in which the contact pressure decreases with time, that is, “stress relaxation resistance”.

  The Cu—Ti based copper alloy has the second highest strength in the copper alloy after the Cu—Be based copper alloy, and has a stress relaxation resistance surpassing that of the Cu—Be based copper alloy. Moreover, it is more advantageous than Cu-Be-based copper alloys in terms of cost and environmental load. For this reason, Cu-Ti type | system | group copper alloy (for example, C1990; Cu-3.2 mass% Ti alloy) is used for the connector material etc. as a substitute material of some Cu-Be type | system | group copper alloys.

Japanese Patent Laid-Open No. 2004-52008 JP 2008-308734 A JP 2011-202218 A JP 2012-12431 A

  A Cu—Ti-based copper alloy is an alloy that can improve the strength by utilizing a modulation structure (spinodal structure) of Ti. Although the material hardens significantly due to the modulation structure, it has the advantage of relatively little loss of fatigue resistance and bending workability. On the other hand, this alloy-based plate material has a drawback that coarse crystal grains and coarse second-phase particles are likely to be present partially, resulting in large variations in bending workability. In a Cu—Ni—Si based copper alloy or the like, the crystal grain size can be made uniform by utilizing the pinning effect of the second phase precipitated particles. However, since the formation mechanism of the second phase is different in the Cu—Ti based copper alloy, it is difficult to utilize such a pinning effect.

  Patent Document 1 discloses a technique for making the crystal grain size of a Cu—Ti-based copper alloy uniform by controlling β phase precipitation during solution treatment. Moreover, the hot working process which combined hot forging and hot rolling is disclosed. According to the manufacturing method of this document, a plate material with a small variation in crystal grain size in which the ratio of grain size deviation / average grain size is 0.6 or less is obtained. However, no special consideration has been given to the coarse second phase particles, and the BW bending workability by 90 ° bending is about R / t of about 3.5. Further improvement is desired.

  Patent Documents 2 to 4 disclose techniques for improving the bending workability of Cu—Ti based copper alloys by defining the crystal grain size, crystal orientation, number density of precipitates, and the like. However, the bending workability variation is not considered.

  An object of the present invention is to improve the bending workability and improve the variation in the Cu-Ti-based copper alloy plate material as compared with Patent Document 1.

  As a result of detailed studies, the inventors have controlled the ratio of the maximum side average crystal grain size / average crystal grain size to a certain level or less before the final cold rolling, and the number density of coarse second-phase particles. It has been found that reduction is important for improving the level of bending workability and reducing variation. Moreover, in order to obtain such a structure state, it has been found that it is extremely effective to sufficiently introduce processing strain by performing hot forging in a lower temperature range than usual for the slab.

In order to achieve the above object, in the present invention, in mass%, Ti: 1.0 to 5.0%, Fe: 0 to 0.5%, Co: 0 to 1.0%, Ni: 0 to 1 0.5%, B: 0 to 0.07%, further Sn: 0 to 1.2%, Zn: 0 to 2.0%, Mg: 0 to 1.0%, Zr: 0 as necessary. -1.0%, Al: 0-1.0%, Si: 0-1.0%, P: 0-0.1%, Cr: 0-1.0%, Mn: 0-1.0% V: 0 to 1.0%, and among these elements, the total content of Sn, Zn, Mg, Zr, Al, Si, P, Cr, Mn and V is 3.0% or less, and the balance Cu And a sheet material after hot rolling having a chemical composition composed of inevitable impurities, the rolling direction of the plate being the L direction, the direction perpendicular to the rolling direction and the plate thickness direction being the T direction, and the cross section perpendicular to the L direction being C When called a cross-section, Coarse grains area ratio determined by the method according to (A) is not more than 5.0%, hot after rolling number density of diameter 1μm or more coarse second-phase particles in the C section is 500 / mm ² or less A Cu—Ti based copper alloy sheet is provided.
(A) A 1.25 mm × 1.25 mm square observation area having a T direction on one side is provided on the C cross section, and the observation area is divided into 81 square squares to be the vertices of each square. A total of 100 lattice points are set, and the total number n _{1 of} lattice points located inside coarse crystal grains having a major axis of 100 μm or more (including on the grain boundaries) among the lattice points on the microscope observation image of the observation region. look, determine n ₁ piece / 100 × 100 coarse grains area ratio of the value calculated by the (%). However, twin boundaries are not regarded as grain boundaries. In addition, a crystal grain having a major axis of 100 μm or more in which a part of the crystal grain is out of the observation region is targeted for counting n ₁ in the observation region.
Here, the major axis is the diameter of the smallest circle surrounding the crystal grain in the observed image.

Further, it is a plate material after aging treatment having the above chemical composition, in which the rolling direction of the plate is called the L direction, the direction perpendicular to the rolling direction and the plate thickness direction is the T direction, and the cross section perpendicular to the L direction is called the C cross section. When the average crystal grain size obtained by the method according to the following (B) in the microscopic observation of the C section is 7.0 to 40.0 μm, the ratio of the maximum side average crystal grain size / average crystal grain size is 2.5 or less. An aging-treated Cu—Ti-based copper alloy sheet is provided in which the number density of coarse second-phase particles having a diameter of 1 μm or more in the C cross section is 1000 / mm ² or less. In this case, it may be cold-rolled after the aging treatment, or may be subjected to cold rolling and low-temperature annealing after the aging treatment.
(B) Ten T-direction line segments with a length of 0.125 mm are set in parallel at an interval of 0.0125 mm in the observation field of the C cross section, and each line segment is line segment according to the cutting method specified in JIS H0501-1986. The number of crystal grains (hereinafter referred to as “cut crystal grains”) that are completely cut by the above and the length of each cut (hereinafter referred to as “individual cut crystal grain sizes”) are measured. This measurement was performed on 10 different fields set at random, and the value (μm) obtained by dividing the total value of individual cut crystal grain sizes by 10 lines × 10 fields = total of 100 line segments by the total number of cut crystal grains. The average grain size is defined as “average crystal grain size”, and five pieces are selected in descending order from the maximum value (μm) of the individual cut crystal grain sizes of the 100 line segments. "
In the present specification, the coarse second phase particles having a diameter of 1 μm or more mean second phase particles having a diameter of a minimum circle surrounding the second phase particles of 1 μm or more.

When producing a plate-shaped slab by hot forging the slab having the chemical composition as a method for producing the Cu-Ti-based copper alloy hot-rolled material, all the hot forging reductions are performed at 850 to 700 ° C. The maximum reduction rate per stroke is 20% or less in any direction, and the reduction in the slab thickness direction is a reduction of 15 to 20% per stroke over the entire material. At least one stroke, and a hot forging process in which the total thickness reduction rate in the slab thickness direction is 25% or more,
A hot rolling step in which hot rolling is performed on the slab after forging at a rolling start temperature of 950 ° C. or less and a rolling rate of 55% or more at 950 to 920 ° C.,
A manufacturing method is provided. The number density of coarse second-phase particles having a coarse crystal grain area ratio of 5.0% or less obtained by the method according to (A) in the microscopic observation of the C cross section by the hot rolling and having a diameter of 1 μm or more in the C cross section. Is preferably in a tissue state of 500 pieces / mm ² .

  Multiple times of cold rolling, solution treatment, aging treatment, finish cooling with one cold rolling or intermediate annealing performed on the copper alloy sheet produced through this hot forging process and hot rolling process By performing hot rolling and low-temperature annealing, a Cu—Ti-based copper alloy sheet material in which bending workability and variations thereof are remarkably improved can be obtained. This plate material is suitable as a material for a current-carrying part manufactured by bending.

  According to the present invention, the Cu—Ti-based copper alloy sheet has excellent bending workability, and the variation in bending workability within the material is remarkably improved. Accordingly, the present invention contributes to an increase in the degree of processing of energized parts such as connectors and an improvement in design flexibility.

The metal structure photograph of the C cross section of the hot-rolled material according to the present invention. The metal structure photograph of C section of the hot-rolled material by the conventional method which has not performed hot forging. The metal structure photograph of the C cross section about the board | plate material (what was low-temperature-annealed after finishing cold rolling) according to this invention. The metal structure photograph of the C cross section about the plate material (what was low-temperature-annealed after finishing cold rolling) by the aging treatment by the conventional process which has not performed hot forging.

<Alloy composition>
In the present invention, a Cu—Ti based copper alloy in which Ni, Co, Fe, and other alloy elements are blended as necessary with a binary basic component of Cu—Ti is employed. Hereinafter, “%” regarding the alloy composition means “mass%” unless otherwise specified.

  Ti is an element having a high age hardening effect in the Cu matrix, and contributes to an increase in strength and resistance to stress relaxation. In order to sufficiently bring out these effects, it is advantageous to secure a Ti content of 1.0% or more, and more preferably 2.5% or more. On the other hand, if the Ti content is excessive, cracks are likely to occur during hot working or cold working. Moreover, the temperature range in which solution treatment can be performed becomes narrow. As a result of various studies, the Ti content needs to be 5.0% or less. You may manage in the range of 4.0% or less or 3.5% or less.

  Fe, Co, and Ni are elements that contribute to improvement in strength by forming an intermetallic compound with Ti, and one or more of these can be added as necessary. Since these intermetallic compounds have the effect of suppressing the coarsening of crystal grains by solution treatment, solution treatment at a higher temperature is possible, which is advantageous in sufficiently dissolving Ti. When one or more of Fe, Co, and Ni are added, the content of each element is preferably Fe: 0.05% or more, Co: 0.05% or more, and Ni: 0.05% or more. It is effective, and it is more effective to set Fe: 0.1% or more, Co: 0.1% or more, and Ni: 0.1% or more. However, when Fe, Co, and Ni are contained excessively, the amount of Ti consumed by the production of these intermetallic compounds increases, so the amount of solid solution Ti inevitably decreases. In this case, the strength tends to decrease. Moreover, since Fe, Ni, and Co form a compound with Ti, excessive inclusion causes an increase in coarse particles. Therefore, when adding one or more of Fe, Co, and Ni, the ranges are Fe: 0.5% or less, Co: 1.0% or less, and Ni: 1.5% or less. You may manage in the range of Fe: 0.30% or less, Co: 0.25% or less, Ni: 0.25% or less.

  B has an effect of refining the cast structure and can contribute to improvement of hot workability. When adding B, it is more effective to set it as 0.01% or more, and it is still more effective to set it as 0.03% or more. However, excessive addition of B is uneconomical, and usually may be added in a range of 0.07% or less.

  Sn has a solid solution strengthening action and an effect of improving stress relaxation resistance. When Sn is contained, it is more effective to secure a content of 0.1% or more. However, from the viewpoint of ensuring castability and electrical conductivity, the Sn content is limited to 1.2% or less, and may be controlled within a range of 0.5% or less or 0.25% or less.

  Zn has the effect of improving solderability and strength, and also has the effect of improving castability. In order to obtain these functions sufficiently, it is desirable to secure a Zn content of 0.1% or more, and it is particularly effective to set it to 0.3 or more. However, excessive Zn content tends to be a cause of a decrease in conductivity and stress corrosion cracking resistance. For this reason, when it contains Zn, it is necessary to set it as 2.0% or less, and you may manage to 1.0% or less or 0.5% or less.

  Mg has an effect of improving stress relaxation resistance and a de-S action. In order to sufficiently exhibit these functions, it is preferable to secure an Mg content of 0.01% or more, and it is more effective to set the content to 0.05% or more. However, since Mg is easily oxidized, when Mg is contained from the viewpoint of ensuring castability, the content is 1.0% or less. More preferably, it is 0.5% or less. Usually, it may be 0.1% or less.

  As other elements, Zr: 1.0% or less, Al: 1.0% or less, Si: 1.0% or less, P: 0.1% or less, Cr: 1.0% or less, Mn: 1.0 % Or less and V: 1.0% or less can be contained. For example, Zr and Al can form an intermetallic compound with Ti, and Si can produce a precipitate with Ti. Cr, Zr, Mn, and V easily form a high melting point compound with S, Pb, etc. present as unavoidable impurities, and Cr, P, and Zr have a refinement effect on the cast structure and have hot workability. Can contribute to improvement. When one or more of Zr, Al, Si, P, Cr, Mn, and V are contained, in order to sufficiently obtain the action of each element, the total content of these elements may be 0.01% or more. It is effective.

  However, if a large amount of Zr, Al, Si, P, Cr, Mn, and V is contained, it becomes a factor that adversely affects hot or cold workability. The total content of Sn, Zn, Mg and Zr, Al, Si, P, Cr, Mn, V is preferably 3.0% or less, and is preferably 2.0% or less or 1.0% or less. The range can be regulated and may be managed within a range of 0.5% or less. More reasonable upper limit regulations considering economics are, for example, Zr: 0.2% or less, Al: 0.15% or less, Si: 0.2% or less, P: 0.05% or less, B: 0 Restrictions of 0.03% or less, Cr: 0.2% or less, Mn: 0.1% or less, and V: 0.2% or less can be provided.

<Metallic structure of hot-rolled material>
When the presence of coarse crystal grains and coarse second-phase particles is sufficiently suppressed at the stage after hot rolling, non-uniformity of crystal grain size and coarseness in the final plate produced through the subsequent steps It was found that the variation in bending workability due to the presence of the two-phase particles was significantly suppressed. As such a highly useful sheet material intermediate product, the present invention discloses a hot rolled material having the following structure.

When the rolling direction of the plate is referred to as the L direction, the direction perpendicular to the rolling direction and the thickness direction is referred to as the T direction, and the cross section perpendicular to the L direction is referred to as the C cross section, the C cross section is obtained by the method according to (A) below under the microscope observation. A Cu—Ti-based copper alloy hot-rolled material having a coarse crystal grain area ratio of 5.0% or less and a number density of coarse second-phase particles having a diameter of 1 μm or more in the C cross section of 500 particles / mm ² or less. The number density of coarse second phase particles having a diameter of 1 μm or more is more preferably 300 particles / mm ² or less.
(A) A 1.25 mm × 1.25 mm square observation area having a T direction on one side is provided on the C cross section, and the observation area is divided into 81 square squares to be the vertices of each square. A total of 100 lattice points are set, and the total number n _{1 of} lattice points located inside coarse crystal grains having a major axis of 100 μm or more (including on the grain boundaries) among the lattice points on the microscope observation image of the observation region. look, determine n ₁ piece / 100 × 100 coarse grains area ratio of the value calculated by the (%). However, twin boundaries are not regarded as grain boundaries. In addition, a crystal grain having a major axis of 100 μm or more in which a part of the crystal grain is out of the observation region is targeted for counting n ₁ in the observation region.

《Metallic structure of aging treatment material》
In addition, in the plate material after aging treatment (aging treatment material), when the grain size distribution of the crystal grain size and the abundance of coarse second phase particles satisfy specific conditions, the aging treatment material and the plate material obtained by processing it are: Further, the variation in bending workability due to the nonuniformity of the crystal grain size is remarkably suppressed. As such a highly useful plate material, the present invention discloses a plate material having the following textured state.
The following structure state is maintained also in the product plate material which has been subjected to finish cold rolling and further low temperature annealing after the aging treatment.

The average crystal grain size determined by the method according to the following (B) in the microscopic observation of the C cross section is 7.0 to 40.0 μm, and the ratio of the maximum side average crystal grain size / average crystal grain size is 2.5 or less. A Cu—Ti-based copper alloy plate material in which the number density of coarse second-phase particles having a diameter of 1 μm or more in a cross section is 1000 / mm ² or less. The number density of the coarse second phase particles having a diameter of 1 μm or more is more preferably 700 particles / mm ² or less.
(B) Ten T-direction line segments with a length of 0.125 mm are set in parallel at an interval of 0.0125 mm in the observation field of the C cross section, and each line segment is line segment according to the cutting method specified in JIS H0501-1986. The number of crystal grains (hereinafter referred to as “cut crystal grains”) that are completely cut by the above and the length of each cut (hereinafter referred to as “individual cut crystal grain sizes”) are measured. This measurement was performed on 10 different fields set at random, and the value (μm) obtained by dividing the total value of individual cut crystal grain sizes by 10 lines × 10 fields = total of 100 line segments by the total number of cut crystal grains. The average grain size is defined as “average crystal grain size”, and five pieces are selected in descending order from the maximum value (μm) of the individual cut crystal grain sizes of the 100 line segments. "

  The board | plate material which has these structure | tissue states can be obtained according to the following processes.

"Production method"
A Cu-Ti-based copper alloy sheet material with small bending workability variation can be manufactured, for example, by the following manufacturing process.
"Melting / Casting-> Hot Forging-> Hot Rolling-> Cold Rolling-> (Intermediate Annealing-> Cold Rolling)-> Solution Treatment->Aging-> Finish Cold Rolling-> Low Temperature Annealing"
Here, it is important to perform hot forging under a specific condition before hot rolling to give a working strain. Prior to hot rolling, the slab surface is cut as necessary. In hot rolling, it is important to obtain sufficient reduction in a high temperature range and promote dynamic recrystallization. After hot rolling, chamfering is performed as necessary, and after each heat treatment, pickling, polishing, or further degreasing is performed as necessary. Depending on the application, “finish cold rolling” and “low temperature annealing” after aging treatment may be omitted. Hereinafter, each step will be described.

[Melting / Casting]
The slab may be manufactured by continuous casting, semi-continuous casting, or the like. In order to prevent oxidation of Ti, it is preferable to carry out in an inert gas atmosphere or a vacuum melting furnace.

[Hot forging]
In the present invention, it is important to perform hot forging and apply processing strain before subjecting to hot rolling. Hot forging in the production of a copper alloy is generally performed in a temperature range of about 900 to 850 ° C. However, in the case of a Cu—Ti based copper alloy, it has been found that the strain energy cannot be sufficiently accumulated in such a temperature range. As a result of various studies, it is effective to perform hot forging in a temperature range of 850 ° C. or lower. However, since the cast structure is fragile, cracking tends to occur when the hot forging temperature is low. Therefore, it is necessary to perform hot forging at 700 ° C. or higher.

According to the study by the inventors, it has been found that it is effective to follow the following conditions in hot forging in order to sufficiently accumulate strain energy in the hot forging process.
(A) The hot forging temperature is set to a relatively low temperature range of 850 ° C. or lower.
(B) Regarding the reduction in the slab thickness direction, at least one or more reductions with a reduction rate of 15 to 20% per application are applied over the entire material.
(C) The total thickness reduction rate in the plate thickness direction of the slab is set to 25% or more.
In order to prevent cracking during hot forging, it is necessary to follow the following conditions.
(D) The hot forging temperature is set to 700 ° C. or higher.
(E) The maximum rolling reduction per shot is 20% or less.
The forging temperature is the material surface temperature during forging.

The rolling reduction per shot (%) is determined by the following equation (1).
Rolling rate per stroke (%) = (t ₀ −t ₁ ) / t ₀ × 100 (1)
Here, t ₀ is the thickness in the hammer traveling direction of the portion where the hammer hits in the material before applying the one-stroke reduction (average thickness when the thickness of the portion is not uniform) (mm), t ₁ means the thickness in the hammering direction of the portion hit by the hammer in the material after applying the one-stroke reduction (average thickness when the thickness of the portion is not uniform) (mm) .
For example, in the case of applying a reduction of 3 strokes continuously at the same position of the material, by applying a reduction with a reduction ratio of 15 to 20% in at least one of the 3 strokes, a position where the hammer hitting surface is hit “ The requirement that at least one or more rolling reductions with a rolling reduction rate of 15 to 20% per stroke is given. In obtaining the plate-like slab, in order to satisfy the above condition (b), for example, an impact with a rolling reduction of 15 to 20% per shot is applied to the surface of the material that becomes the plate surface (wide surface) of the plate-like slab. For all the parts, it is possible to adopt a method of sequentially applying the material while changing the position of the material. However, in order to prevent the occurrence of cracks during hot forging, the maximum rolling reduction per shot is set to 20% or less (above (e)).

In hot forging to obtain a plate-like slab from a slab, there is usually a method of alternately deforming the two axes of the plate-like slab thickness direction (ND) and the plate-like slab width direction (TD) perpendicular thereto. It is done. In order to accumulate sufficient strain energy, it is necessary to secure a total amount of deformation applied to the material above a certain level. As a result of various studies, it is extremely effective to add deformation so that at least the thickness reduction rate of the ND axis is 25% or more, that is, to comply with the above condition (c). In this case, the width of the plate-shaped slab (the thickness of TD) can be maintained equivalent to that of the original slab, for example.
The total thickness reduction rate in the plate thickness direction of the slab (c) is determined by the following equation (2).
Total thickness reduction rate in slab thickness direction (%) = (t ₂ −t ₃ ) / t ₂ × 100 (2)
Here, t ₂ is the thickness of the slab corresponding to the thickness direction of the plate slab (average thickness if the thickness is not constant depending on the location) (mm), and t ₃ is the plate slab obtained. Thickness (mean thickness if the thickness is not constant depending on location) (mm).

  The heating of the slab prior to hot forging is preferably to ensure the in-furnace time until the temperature difference between the thickness center of the slab and the surface is 20 ° C. or less. The heating temperature is set to 800 to 850 ° C., and the in-furnace time may be set to 8 to 16 h for a cast piece having a thickness of about 200 mm, for example. The hot forging temperature is 850 ° C. or less (above (a)). It is more effective to limit the range to 840 ° C. or lower. However, if the temperature is too low, cracking is likely to occur, so the end temperature of hot forging is set to 700 ° C. or higher ((d) above). When hot forging is performed under the conditions according to the above (b) and (c) in a relatively low temperature range of 850 to 700 ° C., more preferably 840 to 700 ° C., strain energy is sufficiently introduced, In the rolling process, the effect of preventing coarsening of recrystallized grains and the effect of reducing the number density of coarse second phase particles are exhibited.

(Hot rolling)
According to the study by the inventors, in the case of a Cu-Ti-based copper alloy, coarse crystal grains and coarse second-phase particles are easily generated during hot rolling due to Ti segregation after melting and casting. It turned out that it becomes a factor which reduces the bending workability of the board | plate material final product obtained through a subsequent process. Therefore, it is necessary to devise manufacturing conditions so as to alleviate Ti segregation formed by melt casting and prevent generation of coarse crystal grains and coarse second phase particles during hot rolling. One of the ideas is the introduction of strain energy in the hot forging process described above. Furthermore, in the hot rolling process, increase the rolling reduction in the highest possible temperature range, promote homogenization by diffusion in the heating stage before hot rolling and promote dynamic recrystallization during hot rolling. is important.

The slab heating temperature during hot rolling is preferably 930 to 950 ° C. The hot rolling start temperature (material temperature in the first rolling pass) is 950 ° C. or lower. If it is higher than that, cracks may occur at a location where the melting point is lowered, such as a segregation location of the alloy component. The rolling rate at 950 to 920 ° C. is 55% or more. If the rolling rate in this high temperature range is reduced, the effect of refining by dynamic recrystallization is reduced, and coarse recrystallized grains may be present. In addition, the relaxation of Ti segregation is insufficient and a large number of coarse second-phase particles are formed. The hot rolling end temperature (material temperature in the final rolling pass) is preferably 700 ° C. or higher. It is desirable to cool rapidly after hot rolling by water cooling or the like.
The rolling rate from a certain sheet thickness t ₄ (mm) to a certain sheet thickness t ₅ (mm) is determined by the following equation (3). The same applies to the rolling rate in each step described later.
Rolling ratio (%) = (t ₄ −t ₅ ) / t ₄ × 100 (3)
The hot rolling temperature is the material surface temperature during hot rolling.

(Cold rolling)
In the cold rolling performed before the solution treatment, the rolling rate is desirably 80% or more. The strain introduced by rolling functions as a nucleus for recrystallization, and is effective in making the crystal grain size uniform. Although the upper limit of the cold rolling rate is limited by mill power or the like, it is usually set within a range of 99% or less. If necessary, a plurality of cold rolling processes with intermediate annealing interposed therebetween may be performed. In that case, the cold rolling process performed after the final intermediate annealing corresponds to the above “cold rolling performed before the solution treatment”.

[Solution treatment]
The solution treatment temperature can be 700 to 950 ° C. It is more preferable to set it as 750-900 degreeC. The heating time may be set in the range of 5 sec to 5 min. Cooling may be performed rapidly by water cooling or the like, as in a normal solution treatment. For example, it is desirable that the average cooling rate from 700 ° C. to 200 ° C. be 100 ° C./sec or more.

[Aging treatment]
The aging treatment temperature may be set in the range of 300 to 550 ° C., and the aging time may be set in the range of 60 to 600 min.

[Finish cold rolling]
Depending on the application, finish cold rolling can be performed to improve the strength level. The finish cold rolling rate is desirably 70% or less. The final plate thickness can be set to, for example, 0.05 to 1.0 mm. Particularly, a thin plate material having a thickness of 0.05 to 0.3 mm is useful for reducing the size of the current-carrying component.

[Low temperature annealing]
After finish cold rolling, low-temperature annealing can be performed for the purpose of reducing the residual stress of the plate material, improving the bending workability, and improving the stress relaxation resistance by reducing the dislocations on the pores and the sliding surface. What is necessary is just to set conditions in the range of heating temperature 150-600 degreeC and heating time 5-3600 sec. When the finish cold rolling is omitted, this low temperature annealing is usually also omitted.

<Characteristics of plate>
[Bending workability]
According to the present invention, in the 90 ° W bending test according to JIS H3110, it is possible to realize an excellent bending workability in which MBR / t of BW (Bad Way) is stably 0.60 or less. The BW bending test is performed under the condition that the longitudinal direction of the bending test piece is the rolling perpendicular direction (T direction) and the bending axis is the rolling direction (L direction).
〔Tensile strength〕
According to the present invention, in the tensile test in the rolling direction (L direction) of the plate material according to JIS Z2241, a tensile strength of 880 MPa or more, preferably 900 MPa or more, and further 920 MPa or more is obtained. Can be achieved.

  The copper alloys shown in Table 1 were melted and cast using a vertical semi-continuous casting machine. The obtained slab was cut into a slab for forging experiments having a length of about 3000 mm, a thickness of 150 mm, and a width of 270 mm. The slab for forging experiment has a uniform cross-sectional shape over the entire length in the length direction. Hereinafter, unless otherwise specified, the term “slab” means the slab for forging experiment. Except for some examples, the slab was heated in a furnace for 4 hours and then extracted and hot forged to obtain a plate slab. The forging start temperature and forging end temperature are shown in Table 2. Since the thickness direction of the slab coincides with the plate thickness direction of the obtained plate-shaped slab, these directions are hereinafter collectively referred to as ND. Similarly, since the width direction of the slab and the width direction of the obtained plate-shaped slab coincide with each other, these are collectively referred to as TD hereinafter.

  In hot forging, reduction was applied in the biaxial directions of ND and TD. Here, TD and ND were forged alternately by a method in which TD (side surface of the slab) was reduced over the entire slab, and then ND (plate surface of the slab) was reduced over the entire slab. At that time, forging was performed so that the first stroke of ND had the maximum reduction ratio. For both ND and TD, a total of 3 to 4 reductions were applied to each location, and the thickness in each direction was adjusted to a predetermined thickness. The “maximum rolling reduction per strike” and the “total thickness reduction rate in the thickness direction of the slab” were uniform for any part of the plate surface of the material. These numbers are shown in Table 2. The width of the obtained plate-shaped slab is about 270 mm, and the slab width in the longitudinal direction is uniform in each slab. After hot forging, the irregularities on the slab surface were smoothed by grinding.

  Except for the case where cracking occurred during hot forging, each of the hot forging slabs was heated in a furnace for 4 h, and then hot rolled to obtain a hot rolled material having a plate thickness of 15 mm. In either case, the hot rolling was finished in a temperature range of 700 ° C. or higher and immediately water-cooled. In some examples, hot forging was omitted and the slab was cut to a thickness of about 115 mm and then directly subjected to hot rolling. Table 2 shows the hot rolling start temperature and the rolling rate from 950 ° C to 920 ° C. In addition, except for the case where cracks occurred during hot rolling and the process could not proceed to the next process, a sample was cut out from the hot rolled material, and the coarse crystal grain area ratio of the C cross section was measured by the method according to (A) above. did. In order to confirm the reproducibility of the measured values, 10 fields of view randomly selected for each hot-rolled material were observed, and all of the measured values of the coarse grain area ratio (%) (numerical values in% display) The fluctuation range was within 1.5. In Table 3, the average value of the numerical values obtained in 10 fields of view is displayed as the coarse crystal grain area ratio (%). Further, the C cross section of the hot rolled material was electropolished and subjected to SEM observation to determine the number density of coarse second phase particles having a diameter of 1 μm or more. For electropolishing, ElectroMet4 (manufactured by BUEHLER) was used, and electropolishing was performed in a region of φ10 mm at a voltage of 15 V for 20 seconds. The electropolishing liquid was a mixed solution of distilled water: 10, phosphoric acid: 5, ethanol: 5, 2-propanol: 1 by volume ratio. SEM observation was performed in 10 fields of view at a magnification of 3000 times.

  Except for the case where cracking occurred during hot rolling, the hot-rolled material was subjected to cold rolling of about 92.8% to a thickness of 1 mm or less, and then subjected to solution treatment in a hydrogen, nitrogen or argon atmosphere. did. In the solution treatment, conditions were adjusted at a holding temperature of 700 to 900 ° C. and a holding time of 1 min to control the average crystal grain size after the solution treatment. The holding temperature of the solution treatment in each example is shown in Table 2.

  As a preliminary experiment to set the aging conditions by taking a sample from the solution-treated material obtained, an aging treatment test is conducted at 300 to 500 ° C. for a maximum of 10 hours, and the aging is the maximum hardness according to the alloy composition. The temperature Tm (° C.) and the maximum hardness Hm (Hv) were determined. The solution treatment material was subjected to an aging treatment with an aging temperature of Tm ± 10 ° C. and an aging time set to a time at which the hardness after aging was 0.08 Hm to 1.0 Hm. Here, the conditions were 450 ° C. × 6 h in each example.

  After the aging treatment, finish cold rolling was performed at a rolling rate of 70% or less, and the final plate thickness was adjusted to 0.1 mm. Then, low temperature annealing was performed in the range of 300-600 degreeC in hydrogen, nitrogen, or argon atmosphere.

With respect to the plate material (test material) having a thickness of 0.1 mm obtained in this way, the ratio of average crystal grain size and maximum side average crystal grain size / average crystal grain size was determined by the method according to (B) above. In addition, the ratio of standard deviation / average crystal grain size with respect to the crystal grain size was calculated using the data. SEM observation was performed on the C cross section of the test material in the same manner as described above, and the number density of coarse second phase particles having a diameter of 1 μm or more was determined.
Moreover, the tensile test of the L direction was done according to JISZ2241, and the tensile strength was calculated | required by the average value of the test number n = 3. Further, in accordance with JIS H3110: 2012, a 90 ° W bending test of BW was performed at a test number n = 10 under a fixed condition where the ratio R / t of the bending radius R to the sheet thickness t was 0.6, and the bending after the test was performed. The surface of the processed part was observed with an optical microscope at a magnification of 100 times to examine whether or not cracking occurred. In this bending test, the ratio of the specimens where cracks occurred among the ten specimens was displayed as “crack occurrence rate (%)”, and no cracks were observed in all cases (that is, crack occurrence rate) = 0%) was accepted and the others were rejected. It can be judged that the plate material which has passed the strict evaluation method by this strict evaluation method has excellent bending workability and extremely small variation in bending workability. Table 3 shows the results of these tests.

  As can be seen from Tables 2 and 3, the copper alloy sheets according to the present invention each have a small area ratio of coarse crystal grains in the hot-rolled material, and the maximum side average crystal grain size / average crystal grain size in the aging-treated material. The ratio was kept small. As a result, the bending workability was good and the variation was remarkably improved.

  On the other hand, Comparative Example No. 31 had a small maximum rolling reduction per shot in hot forging, and No. 32 had a small total thickness reduction rate in the slab plate thickness direction in hot forging. In each case, accumulation of strain energy became insufficient, and the obtained plate material became a mixed grain structure in which coarse crystal grains existed, and the number density of coarse second-phase particles also increased. As a result, the variation in bending workability was large. No. 33 was a hot-rolled and the rolling rate in a high temperature range was insufficient, so that it became a mixed grain structure in which coarse crystal grains existed, and the bending workability varied greatly. In No. 34, since the hot rolling temperature was too high, the hot rolled material was cracked, and the subsequent steps were stopped. No. 35 has a maximum maximum reduction rate per one shot in hot forging, No. 36 has a hot forging temperature too high, and No. 37 has a hot forging temperature too low. Occasionally, the material cracked, and all subsequent processes were discontinued. Nos. 38 to 41 were not subjected to hot forging, so that the obtained plate material had a mixed grain structure in which coarse crystal grains existed, the number density of coarse second-phase particles was increased, and variation in bending workability was observed. Was not improved.

  For reference, FIG. 1 illustrates a metallographic photograph of the C cross section of a hot-rolled material according to the present invention (Invention Example No. 2). FIG. 2 illustrates a metallographic photograph of the C cross section of a hot-rolled material (Comparative Example No. 38) by a conventional method not subjected to hot forging. In FIG. 3, the metal structure photograph of the C cross section of the board | plate material (No.2 low-temperature annealing material) age-treated according to this invention is illustrated. FIG. 4 illustrates a metallographic photograph of the C cross-section of a plate material (No. 38 low-temperature annealed material) that has been aged by a conventional process that has not been hot forged.

Claims (9)

In mass%, Ti: 1.0 to 5.0%, Fe: 0 to 0.5%, Co: 0 to 1.0%, Ni: 0 to 1.5%, B: 0 to 0.07% A sheet material after hot rolling having a chemical composition consisting of the balance Cu and inevitable impurities, the rolling direction of the sheet being the L direction, the direction perpendicular to the rolling direction and the sheet thickness direction being the T direction, and perpendicular to the L direction When the cross section is referred to as the C cross section, the coarse crystal grain area ratio determined by the method according to the following (A) in the microscopic observation of the C cross section is 5.0% or less, and the coarse second phase particles having a diameter of 1 μm or more in the C cross section A Cu—Ti-based copper alloy sheet after hot rolling having a number density of 500 pieces / mm ² or less.
(A) A 1.25 mm × 1.25 mm square observation area having a T direction on one side is provided on the C cross section, and the observation area is divided into 81 square squares to be the vertices of each square. A total of 100 lattice points are set, and the total number n _{1 of} lattice points located inside coarse crystal grains having a major axis of 100 μm or more (including on the grain boundaries) among the lattice points on the microscope observation image of the observation region. look, determine n ₁ piece / 100 × 100 coarse grains area ratio of the value calculated by the (%). However, twin boundaries are not regarded as grain boundaries. In addition, a crystal grain having a major axis of 100 μm or more in which a part of the crystal grain is out of the observation region is targeted for counting n ₁ in the observation region.   Chemical composition is mass%, Ti: 1.0 to 5.0%, Fe: 0 to 0.5%, Co: 0 to 1.0%, Ni: 0 to 1.5%, B: 0 0.07%, Sn: 0 to 1.2%, Zn: 0 to 2.0%, Mg: 0 to 1.0%, Zr: 0 to 1.0%, Al: 0 to 1.0%, Si: 0 to 1.0%, P: 0 to 0.1%, Cr: 0 to 1.0%, Mn: 0 to 1.0%, V: 0 to 1.0%. The total content of Sn, Zn, Mg, Zr, Al, Si, P, B, Cr, Mn, and V is 3.0% or less, and the balance is composed of the balance Cu and inevitable impurities. The Cu-Ti-based copper alloy sheet according to the description. In mass%, Ti: 1.0 to 5.0%, Fe: 0 to 0.5%, Co: 0 to 1.0%, Ni: 0 to 1.5%, B: 0 to 0.07% An aging-treated plate material having a chemical composition consisting of the remainder Cu and inevitable impurities, the rolling direction of the plate being the L direction, the direction perpendicular to the rolling direction and the plate thickness direction being the T direction, and a cross section perpendicular to the L direction Is referred to as the C cross section, the average crystal grain size determined by the method according to the following (B) in the microscopic observation of the C cross section is 7.0 to 40.0 μm, and the ratio of the maximum side average crystal grain size / average crystal grain size is 2 An aging-treated Cu—Ti-based copper alloy sheet in which the number density of coarse second-phase particles having a diameter of 1 μm or more in the C cross section is 1000 / mm ² or less.
(B) Ten T-direction line segments with a length of 0.125 mm are set in parallel at an interval of 0.0125 mm in the observation field of the C cross section, and each line segment is line segment according to the cutting method specified in JIS H0501-1986. The number of crystal grains (hereinafter referred to as “cut crystal grains”) that are completely cut by the above and the length of each cut (hereinafter referred to as “individual cut crystal grain sizes”) are measured. This measurement was performed on 10 different fields set at random, and the value (μm) obtained by dividing the total value of individual cut crystal grain sizes by 10 lines × 10 fields = total of 100 line segments by the total number of cut crystal grains. The average grain size is defined as “average crystal grain size”, and five pieces are selected in descending order from the maximum value (μm) of the individual cut crystal grain sizes of the 100 line segments. "   Chemical composition is mass%, Ti: 1.0 to 5.0%, Fe: 0 to 0.5%, Co: 0 to 1.0%, Ni: 0 to 1.5%, B: 0 0.07%, Sn: 0 to 1.2%, Zn: 0 to 2.0%, Mg: 0 to 1.0%, Zr: 0 to 1.0%, Al: 0 to 1.0%, Si: 0 to 1.0%, P: 0 to 0.1%, Cr: 0 to 1.0%, Mn: 0 to 1.0%, V: 0 to 1.0%. 4. The total content of Sn, Zn, Mg, Zr, Al, Si, P, B, Cr, Mn and V is 3.0% or less, and the balance is composed of the balance Cu and inevitable impurities. The Cu-Ti type | system | group copper alloy plate material by which the aging treatment of description was carried out.   The Cu-Ti-based copper alloy sheet according to claim 3 or 4, which has been cold-rolled after aging treatment. In mass%, Ti: 1.0 to 5.0%, Fe: 0 to 0.5%, Co: 0 to 1.0%, Ni: 0 to 1.5%, B: 0 to 0.07% When a plate-shaped slab is obtained by hot forging a slab having a chemical composition composed of the remaining Cu and inevitable impurities, all the hot forging is reduced in a temperature range of 850 to 700 ° C. The maximum reduction rate per hit is 20% or less in any direction of reduction, and for reduction in the slab thickness direction, a reduction with a reduction rate of 15 to 20% per shot is applied over the entire material. A hot forging process in which the total thickness reduction rate in the slab thickness direction is 25% or more,
A method according to the following (A) in the microscopic observation of the C section by subjecting the slab after forging to hot rolling at a rolling start temperature of 950 ° C. or lower and a rolling rate of 55% or higher at 950 to 920 ° C. A hot rolling step of obtaining a plate material having a coarse crystal grain area ratio of 5.0% or less determined in step 1 and a number density of coarse second-phase particles having a diameter of 1 μm or more in the C cross section of 500 particles / mm ² or less ;
The manufacturing method of the Cu-Ti type copper alloy board | plate material which has this.
(A) A 1.25 mm × 1.25 mm square observation area having a T direction on one side is provided on the C cross section, and the observation area is divided into 81 square squares to be the vertices of each square. A total of 100 lattice points are set, and the total number n _{1 of} lattice points located inside coarse crystal grains having a major axis of 100 μm or more (including on the grain boundaries) among the lattice points on the microscope observation image of the observation region. look, determine n ₁ piece / 100 × 100 coarse grains area ratio of the value calculated by the (%). However, twin boundaries are not regarded as grain boundaries. In addition, a crystal grain having a major axis of 100 μm or more in which a part of the crystal grain is out of the observation region is targeted for counting n ₁ in the observation region .
Here, the C cross section means a cross section perpendicular to the rolling direction of the plate, and the T direction means a direction perpendicular to the rolling direction of the plate and the thickness direction. The chemical composition of the slab is, by mass, Ti: 1.0 to 5.0%, Fe: 0 to 0.5%, Co: 0 to 1.0%, Ni: 0 to 1.5%, B : 0 to 0.07%, Sn: 0 to 1.2%, Zn: 0 to 2.0%, Mg: 0 to 1.0%, Zr: 0 to 1.0%, Al: 0 to 1. 0%, Si: 0 to 1.0%, P: 0 to 0.1%, Cr: 0 to 1.0%, Mn: 0 to 1.0%, V: 0 to 1.0%, Sn of the elements, Zn, Mg, Zr, Al , Si, P, Cr, the total content of Mn and V are 3.0% or less, claim in which the balance Cu and unavoidable impurities 6 The manufacturing method of Cu-Ti type | system | group copper alloy board | plate material of description. A plurality of cold rolling and solution forming with one cold rolling or intermediate annealing between the copper alloy sheet material produced through the hot forging step and the hot rolling step according to claim 6 or 7 . The average crystal grain size determined by the method according to the following (B) in the microscopic observation of the C cross section by performing treatment, aging treatment, finish cold rolling, and low temperature annealing at a heating temperature of 150 to 600 ° C. is 7.0 to 40. A plate material is obtained in which the ratio of the maximum side average crystal grain size / average crystal grain size is 2.5 μm or less and the number density of coarse second-phase particles having a diameter of 1 μm or more in the C cross section is 1000 particles / mm ² or less. The manufacturing method of a Cu-Ti type copper alloy board | plate material.
(B) Ten T-direction line segments with a length of 0.125 mm are set in parallel at an interval of 0.0125 mm in the observation field of the C cross section, and each line segment is line segment according to the cutting method specified in JIS H0501-1986. The number of crystal grains (hereinafter referred to as “cut crystal grains”) that are completely cut by the above and the length of each cut (hereinafter referred to as “individual cut crystal grain sizes”) are measured. This measurement was performed on 10 different fields set at random, and the value (μm) obtained by dividing the total value of individual cut crystal grain sizes by 10 lines × 10 fields = total of 100 line segments by the total number of cut crystal grains. The average grain size is defined as “average crystal grain size”, and five pieces are selected in descending order from the maximum value (μm) of the individual cut crystal grain sizes of the 100 line segments. "
Here, the C cross section means a cross section perpendicular to the rolling direction of the plate. The electricity supply component formed by processing the Cu-Ti type | system | group copper alloy board | plate material of any one of Claims 3-5 .