JP2017109224A - Manufacturing method of metal product using new forging processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a metal product using a new forging processing method, concerning a forging processing method occupying an important position in plastic processing of a metal material, more precisely, which does not belonging to any of hot forging, warm forging and cold (room temperature) forging which are each conventional forging processing method.SOLUTION: In a manufacturing method of a metal product using a new forging processing method, a preformed piece formed from a metal plate material is molded into a finished article by avoiding blue heat embrittlement by temperature control in a low temperature area of 200°C or lower which is different from a hot/warm/cold forging temperature area, and by heightening plastic fluidity jointly with servo control.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a forging method that occupies an important position in plastic processing of a metal material, and more specifically, any of conventional forging methods such as hot forging, warm forging, and cold (room temperature) forging. The present invention relates to a method for manufacturing a metal product using a new forging method that does not belong to any of the above.

In recent years, in advanced fields such as precision machine parts, electrical / electronic parts, and superconducting particle accelerators, demands for processability, processing accuracy, productivity, and economic efficiency are increasing.
The conventional hot forging method is suitable for heat-resistant materials, the warm forging method is suitable for forging of materials that are difficult in cold forging, and the cold forging method is suitable for good workability and good productivity. Have. However, hot forging requires a great deal of thermal energy, and surface oxidation of the metal material and its removal become a problem. Warm forging involves chemical conversion treatment, and there are concerns about blue heat embrittlement or strain aging. Further, in cold forging, there are many cases where occurrence of defects such as necking (necking) and cracks cannot be avoided.

  Recently, with the discovery of the Higgs boson and the development of the Big Bang and inflation theory, the International Linear Collider (ILC) construction plan, which is a long linear accelerator ranging from 30 to 50 km, has been intensively advanced. The core of the ILC is a superconducting high-frequency accelerating cavity. ILC requires about 17,000 units. As shown in FIG. 1, it consists of a center part 2 composed of nine cells and both end group parts 3. The end group component 3 includes a port (beam pipe 3a, port pipe 3b) for power input and monitoring, and a HOM (harmonic) coupler 3c having a complicated shape.

  As shown in FIG. 2, the HOM coupler 3 c is obtained by integrating a HOM cup 4 and a HOM antenna 5. That is, when the particle beam is electromagnetically accelerated and passes through the cavity, the HOM (harmonic) is excited, and the beam acceleration is hindered. Therefore, the particle beam needs to be sucked out of the cavity and attenuated. The HOM coupler (harmonic attenuator) is responsible for this function.

  The material used for both the 9-cavity center part 2 and the end group part 3 is pure niobium, a rare metal. The main reason is that pure niobium has a high superconducting transition temperature of 9.2K. By using this at 2K, the most important superconducting property, that is, per unit length to improve the easy acceleration of the particle beam. This is because there is a high possibility that a high acceleration voltage can be obtained.

  Pure niobium is extremely expensive and difficult to press / cut. The main reasons are the low plastic strain ratio for press working and the adhesion phenomenon with tools for cutting. Conventionally, the actual state of the HOM antenna 5 is that a shaped product made from a raw material by cutting or water jet machining is commercialized by cutting.

  Further, with respect to the HOM cup 4, the entire cutting process or cutting and heat treatment after backward extrusion, or press work of a plurality of processes, heat treatment between processes, and insertion of heat treatment after work are inserted.

  Accordingly, all of them have serious problems in terms of productivity and economy, and in order to solve these problems, there is a strong expectation that the construction method will be switched to an advanced press working method.

  Therefore, the inventors have studied a technique for converting the method to ultra deep drawing for the HOM cup 4 and have already filed domestic and international patent applications (Patent Documents 1 and 2).

  However, as can be inferred from the external view of FIG. 2D, the HOM antenna 5 is a “difficult-to-process product” in terms of press processing, and the pure niobium material is machine-cut or pressed. In any case, it is a “difficult to process material”. And since the initial plate thickness of the HOM antenna 5 is 10 mm, the target barrier is high.

  In the HOM antenna 5, in particular, the distance dimension of each part is important in order to optimize the superconducting characteristics. At the same time, it is necessary to consider the plate thickness and the R dimension of the edge. Originally, it is necessary to consider “material technology” and “plastic processing technology” at the same time when the end group part 3 is pressed. In addition, a part of the almost square punching hole is narrowed and stress concentration is likely to occur, so necking / cracking, excess / insufficiency, shape formation, residual stress, etc. are expected. Difficulty is high.

  Furthermore, CP (chemical polishing) and EP (electrolytic polishing) are performed in the finishing process. In order to reduce the load as much as possible, attention should be paid to the surface properties and adhesion / intrusion of foreign substances and trace impurity elements on or near the surface. Must.

  Therefore, a processing method other than the water jet processing belonging to the cutting processing and high energy processing of the HOM antenna 5 is not known and has not been established. And, a drastic improvement in mass productivity and a reduction in manufacturing cost are strongly expected by changing the construction method from cutting and water jet machining.

  Here, as a means to meet expectations, in order to convert the conventional method to full press processing, “new full press processing” by “new shear stamping” and subsequent “new forging” is still an attempt. The present invention is the result of research and development for the realization of the idea based on a never-before-seen idea.

Here, the existing conventional shear punching and precision punching methods are excluded. In the former, since the punching clearance is usually 5 to 10% of the plate thickness (t), it is impossible to obtain the required shape accuracy, and in the latter, an expensive dedicated machine and expensive mold costs are generated. This is because the difficulty is high and production efficiency may become a problem.

  Prior to the study of the “new shear punching method”, the inventors examined and evaluated the possibility of forming a shaped part in “water jet machining”, which is a type of high-energy machining method, instead of cutting first. did. Since processing of shaped parts by water jet machining is expected to be relatively fast and highly efficient, it is possible to replace the subsequent cutting with press working by the well-known “cold forging” Various experiments and examinations were conducted while putting them in

  As a result, the existence of several technical problems was recognized. The main problem is that the presence of abrasive grains and their embedding in the substrate were confirmed by surface SEM observation and EDX elemental analysis after CP of the prototype (FIG. 3). From the SEM image (FIG. 3A), white dots of several μ to several tens of μ are clearly scattered, and the surrounding color tone is probably changed by the stress field.

  In the EDX (energy dispersive X-ray analysis) measurement chart (FIG. 3B) of the observation field of view (indicated by white circles) in the SEM image, white points (particle groups) are due to alumina, silica, iron oxide, magnesium oxide, or the like. Identified. The cause of the presence of these particulate foreign matters is regarded as “abrasive grains” used at the time of water jet cutting in the production of a shaped product. At present, as long as this cutting method is applied, residual abrasive grains are inevitable.

  If the abrasive grains are embedded, there is a high possibility of promoting the generation of the high-frequency resonance mode, and the concern of adversely affecting the cavity performance cannot be wiped out. Therefore, the water jet machining of this shaped product must be avoided. Moreover, the water jet machining cannot be denied that it is inferior in productivity and economy as compared with the press shear punching. In the case of the HOM antenna 5, since it takes about 10 minutes to manufacture one cut-shaped product, it is much more efficient than the whole cutting, but tens of thousands (one acceleration cavity) There is a difficulty in mass production of 2 antennas required for the stand.

  On the other hand, conventional cold forging was first considered in the processing of a shaped product into a product shape. However, as a result of the test, for example, problems such as necking, dimensional inconsistency, stress concentration and shape problems (sag, burr, material surplus, insufficient filling, etc.) or adhesion phenomenon were confirmed. It can be said that “plastic flow” between the material and the mold is related to the common cause.

  In particular, it is a serious problem that the necking phenomenon shown in FIG. 4 occurs in a part after the cold forging test. Although experiments were conducted with various cold forging conditions on technical plastic working, the occurrence of necking (in a circle) could not be avoided.

  No matter how small the occurrence of necking is, this is an important problem that impairs the function of the HOM antenna 5 and causes the accelerator not to operate even if it is one of the total used for the accelerator. I can't.

  It is certain that this necking is caused by stress concentration, but it is unknown whether the material is mainly due to insufficient strength, ductility, plastic flow, or insufficient deformation margin in the deformation process.

The remaining or necking of the abrasive grains is a phenomenon caused by the interaction between the material and processing. Naturally, the function of the accelerating cavity such as resonance mode control and superconducting properties is surely deteriorated after combination with the HOM cup 4 or electron beam welding (EBW), so that it is necessary to eliminate the generation. However, as mentioned above, it is certain that there is a problem of plastic fluidity as a main cause. Therefore, it is extremely important to examine a new method for processing the HOM antenna 5 in consideration of both the material and the processing.
In other words, from the viewpoints of workability, mass productivity, economy, initial investment, etc., when manufacturing processed products by cold forging, demands for using difficult-to-process materials in recent years, regardless of whether they are ferrous or non-ferrous, and various difficult-to-process shapes The need for product processing has arisen. In addition, due to strict demands on the accuracy of processed products, problems such as necking, cracking, dimensional defects, shape (such as drooling, flashing, overfilling, insufficient filling), and adhesion phenomena have occurred. Furthermore, with respect to the improvement of defect rate, mass productivity, material yield, and economic efficiency (cost), since demands are severe, development of a new forging method to cope with these is required.

Japanese Patent Application No. 2013-152686 WO2013 / 115401 A1 JP 07-48589 A

  Therefore, the present invention relates to a forging method that occupies an important position in plastic processing of a metal material. More specifically, the present invention relates to a conventional forging method such as hot forging, warm forging, and cold (room temperature) forging. An object of the present invention is to provide a metal product manufacturing method using a new forging method that does not belong to any of the above.

As a result of examining the above tests and problems, the inventors have found a new shear punching method and a new forging method, further forming a shaped product by the new shear punching method, and using a new forging method, the product shape The present invention has been completed by creating a combination technique for forming a processed product.
That is, based on the results of the following consideration and verification for the above-mentioned severe needs including economy and productivity: 1) Material deformation due to processing temperature and various temperature-dependent phenomena occurring on the surface and inside; 2) Forging Basic knowledge of processing, simulation, basic experiments; 3) Consideration of tribology (friction and lubrication engineering); Rotational friction test; 4) Macroscopic / microscopic examination on plastic flow;
Then, in the temperature range that was not seen in the past, the temperature control device and the press equipped with servo function were used to give special consideration to the plastic fluidity of the material for the deformation temperature / distribution effect and deformation speed / motion effect on the forging behavior. I went and found a new forging method.

More specifically,
In order to solve the above problems, the present invention
(1)
It is characterized in that a shaped product formed from a metal plate material is formed into a processed product by avoiding blue heat embrittlement by low temperature region temperature control at 200 ° C. or less, which is different from the hot, warm and cold forging temperature regions. A metal product manufacturing method using a new forging method.
(2)
The low temperature range temperature control of the forging process is a temperature control that minimizes the formation of a surface oxide film of the shaped article, and manufacturing a metal product using the new forging process described in (1) Method.
(3)
The method for producing a metal product using the new forging method according to (1), wherein the low temperature range temperature control of the forging is temperature control for facilitating plastic fluidity of the shaped product.
(4)
The method for producing a metal product using the new forging method according to (1), wherein the metal plate material has a fine grain structure with a grain size of several tens of μm.
(5)
The die used in the forging is a surface-modified die for preventing seizure, and a solid film lubricant having temperature-independent lubrication performance is used for a workpiece. A method for producing a metal product using the new forging method described in (1).
(6)
The forging process includes measuring a servo of a press machine and includes speed and motion control. The method for producing a metal product using the new forging process described in (1).
(7)
(A) a shear punching process for forming a shaped product from a metal plate material;
(B) In order to form a processed product having the shape of the shaped product, temperature control of the mold and the shaped product for avoiding blue heat embrittlement and facilitating plastic flow of the shaped product. A heating device to perform, a mold whose surface is modified to improve moldability and minimize surface oxidation of the molded product, and a temperature-independent solid coating for preventing seizure between the molded product and the mold It consists of a type of lubricant and a forging process different from any of hot / warm / cold forging, in which the press machine is equipped with a servo mechanism that controls the speed and motion of the new shear stamped shaped product,
A metal product manufacturing method using a new forging method, wherein the metal product cutting or water jet processing is converted into a press method.
It was.

  The present invention can form various metal products by forging, for example, a forging cooperative technology for forming a processed product that does not depend on any of the existing hot / warm / cold forging methods. Enables excellent productivity and economics essential for industrial use. Also, in forming a shaped product, using a metal plate as a starting material, a metal using a new shear press punching process that forms a shaped product without using cutting or water jet processing or using a precision punching method. It is possible to provide a product manufacturing method, solve the technical problem of the current fine blanking method, and eliminate difficult productivity and high cost. Examples of the target metal products include a wide variety of metal products such as precision mechanical parts, precision parts in the electric / electronic field, and deformed precision parts in advanced fields such as elementary particle accelerators.

  As a result, the problem of embedding abrasive grains due to water jet processing and the problem of necking due to cold forging are eliminated, and the amount of use of expensive metal materials such as pure niobium, various steel materials and non-ferrous metal materials can be reduced. , Material costs can be reduced. Furthermore, depending on the required accuracy in press molding, it can be processed before finishing, or the finishing process (finishing cutting) can be greatly reduced, reducing the manufacturing time. As a result, it is possible to significantly reduce manufacturing costs and contribute to stable mass production and parts supply. The technology is not limited to niobium products, and can be applied to various metal materials such as cold-rolled steel plates, stainless steel, steel, iron, and non-ferrous metal materials. Moreover, even if it is an accelerator related part, the operation | movement of the stable accelerator can be ensured.

It is the photograph of the superconducting high frequency 9 cell acceleration cavity which attached the end group made from a pure niobium. It is a schematic diagram of the HOM coupler which comprises the pure niobium end group of a superconducting high frequency acceleration cavity, and the HOM cup and HOM antenna which comprise a HOM coupler. It is explanatory drawing of the water jet processing of the conventional thick pure niobium board | plate material. (A) is an SEM electron micrograph of the surface of a shaped product formed by water jet processing, and (B) is an EDX elemental analysis result of particles in the white circle of (A). It is a photograph of a processed product formed by cold forging of a shaped product formed by conventional water jet processing. (A) Appearance image, (B) is a close-up image in the circle of (A). The occurrence of necking is observed in (B). It is an example of the constraining method of the thick pure niobium material in the shear punching process. (A) is a BB 'cross-sectional schematic diagram of (B) shown with a raw material and a tool, (B) is an A-A' arrow schematic diagram of (A). It is a figure which shows the blue-hot brittle phenomenon of pure niobium. It is the external appearance photograph of the servo press machine and heating / cooling control apparatus which mount various control mechanisms and metal mold | die used for the press work of this invention. It is a photograph of a shear punching shaped article (A) and a forged product (before finishing) (B) according to the present invention. FIG. 3 is a perspective view (photograph) of a shaped product (A) obtained from a stainless steel plate by a new shear punching method, forged products (B) and (B ′) obtained by a new forging method, and a nozzle vane subjected to cutting. .

  Hereinafter, the present invention will be described in detail with reference to FIGS.

  Of the superconducting high-frequency accelerating cavity pure niobium end group part 3 used for acceleration of charged particles according to the present invention, the HOM antenna 5 has a new shear punching method (1) and a new forging method. It is manufactured from (2) and makes it possible to switch from conventional cutting and water jet processing to press processing.

(1) Shear punching process The shear punching process is a process of forming the shaped article 5b from the thick pure niobium plate material 5a, and the gap (clearance) between the die 6a and the punch 6c is reduced. It includes a binding means, a high-speed punching means, a heat removal cooling means, a multi-action die, a servo die cushion, and servo control of a press machine, and consists of an appropriate combination of each method. The means / effects will be described below.

・ Fine clearance 6e
As shown in FIG. 5 (A), in order to obtain a high precision shear punched product, the minute clearance 6e is a minute gap of 0.5% or less of the workpiece thickness (t) through the gap between the die 6a and the punch 6c. Is set to In conventional punching, 10 to 15% of the plate thickness (t) is normal, and in the existing precision punching (FB) method, t ≦ 0.5%. However, the FB method requires an expensive FB (hydraulic) press machine and special dies that need to form V-shaped projections, the punching speed is slow, and the press machine requires skill. There is.

  On the other hand, the present invention provides a new shear punching method that can be applied to difficult-to-press materials such as the thick-walled pure niobium plate 5a, which does not correspond to the conventional punching or FB method, by the following idea.

-Binding means 6
As shown in FIG. 5, for example, the thick pure niobium plate 5a can be used without adopting the special metal mold of the V-shaped projection method employed in the normal FB method. This suppresses and controls fluctuations in the thickness of the bulge and the shaped product 5b.

  For example, as shown in FIG. 5, a normal plate presser load Pb is applied to the thick pure niobium plate material 5a from above and below (the plate presser 6d and the die 6a). In some cases, a reverse presser (reverse direction) load Pp is applied to the punching load Pf depending on the generation degree of the sagging of the thick pure niobium plate material 5a.

  Further, in the present invention, the binding load F is applied to the thick pure niobium plate material 5a. The binding load F includes a first side surface binding force F1 applied to the long side surface of the thick pure niobium plate 5a, which is a rectangular material, and a second side surface binding force F2 applied to the short side surface. F1 'is a counter load of F1, and F2' is a counter load of F2.

On this occasion,
Pb = F1 + F2 Formula (1)
It is important to control to maintain this relationship. As a result, the thickness variation of the thick pure niobium plate material 5a at the time of shear punching can be suppressed to a necessary and sufficient level.

  Here, since the present invention includes that Pb is dynamically controlled during processing by the servo die cushion, F may be regarded as a factor that fluctuates following the principle.

  The thick pure niobium plate material 5a moves at the time of punching regardless of whether it is a V-shaped projection method adopted in the normal FB method or a normal plate retainer, and the thickness of the shaped product 5b is reduced. Recognizing that this happens, the inventors have devised such an inventive element.

-It has been found that the shear punchability is improved by increasing the punch speed to, for example, 100 mm / sec or more when punching the continuous high-speed punching and the heat-extracted and cooled thick pure niobium plate material 5a. Such a high speed cannot be realized by a hydraulic servo mechanism in the FB method. Therefore, in the present invention, it can be realized by a press machine mounting function of an electric servo control mechanism described later.

  In pure niobium, the mechanism by which punching performance is improved by high-speed punching was unclear, but the inventors, from the viewpoint of materials engineering, affected the microslip and its tangling (tangling) during processing deformation of pure niobium material. However, it was found that this is mainly due to the fact that the strain is reduced by facilitating cross-slip due to a decrease in stacking fault energy.

  On the other hand, when the punching speed is increased and continuous machining is performed, the amount of conversion of the external force into heat energy increases and accumulates, generating a heat generation phenomenon and increasing the mold temperature. Then, the interaction between the atoms increases on the surface of the mold and the thick pure niobium plate material 5a, and a chemical change of the lubricant and the mold surface modification film, mainly an oxidation reaction occurs, resulting in a "seizure phenomenon". Therefore, it is necessary to “heat-extract” the work material and the mold during continuous shear punching. Therefore, the mold must be cooled by the temperature control device, and the workpiece must be cooled by heat conduction.

・ The multi-action die press machine is usually based on the 2-axis external force machining (slide and plate press) type, but it is a multi-action machine that adds a servo function to the conventional press machine without using a complicated mechanism like the FB method. By mounting the die, it is possible to operate a “counterforce” (third axial force) in the opposite direction to the sliding force, which can also be used as a knockout function (three-axis external force machining).

  In order to mold the highly accurate shaped product 5b with the minute clearance 6e, the effect of such a simple double-acting device cannot be ignored (corresponding to Pp in FIG. 5). As a result, it is possible to suppress the initial investment of the shear punching processing apparatus and to reduce the product cost of the shaped product 5b in combination with the productivity improvement.

The servo die cushion is mounted to improve the shear punchability by changing the plate pressing load (surface pressure) during shear punching of the thick pure niobium plate material 5a during the shear punching process. Since the machining time is short, it is difficult to perform such dynamic variable operation, but it has become possible to put it to practical use by improving the response speed of the feedback sensor. This mechanism, when used in combination with other components, exhibits a synergistic effect and enables high-accuracy and high-efficiency shear punching.

-Servo (speed / motion) controlled press working is a known method / apparatus, but is important in the present invention characterized by effective use of high-speed / continuous shear punching, speed control and motion control. There is no such idea in the past in the shear punching process.

(2) Forging process Next, forging process is a process of forming the shaped product 5d into a product-shaped processed product 5c, in which the temperature is controlled at a low temperature range (blue heat embrittlement suppression, surface oxide film minimization, plastic flow facilitation). It consists of an appropriate combination of each method including selection of fine crystal pure niobium material, surface-modified mold, proper lubricating oil, and servo control of press machine. Hereinafter, these means / effects will be described. The shaped product is subjected to conventional post-processing or finishing processing after forging or replacing forging, and a finished product is obtained.

-Low temperature range Temperature control Temperature exceeding room temperature (RT) (temperature not including room temperature) to 200 ° C for low temperature range pure niobium blue heat embrittlement, surface oxide film minimization, plastic flow facilitation Control the temperature with. More preferably, it is higher than 20 ° C. and not higher than 200 ° C., more preferably 50 to 150 ° C.
Conventionally, in forging, in relation to temperature conditions,
Hot forging (above recrystallization temperature, roughly> 800 ° C)
Warm forging (300-800 ° C)
Cold forging (RT (room temperature)) is known.
The temperature range of this low temperature range control of the present invention is a temperature control means in a new temperature range that does not apply to any conventionally known temperature control range, and a new forging process suitable for processing difficult-to-press materials It provides the law.

・ As a result of investigating the temperature dependence of static and dynamic mechanical properties of blue-hot brittle pure niobium in a wide range (Fig. 6), valuable information on the means and effects of pressing the thick pure niobium plate 5a As a result, the inventors have come up with an important element for a new forging method related to the present invention.

  FIG. 6 shows the results of static uniaxial tension of pure niobium at 0 to 400 ° C. The horizontal axis is temperature, the first vertical axis (left) is elongation (ductility), and the second vertical axis (right) is tensile strength (strength characteristics). The results for different charges are plotted for EL (total elongation).

  From this, it can be seen that the static mechanical properties of pure niobium do not change uniformly (increase, decrease, or remain unchanged) with respect to temperature changes. In particular, it has been known that both ductility and strength characteristics of pure niobium rapidly decrease in a temperature range of 200 to 300 ° C. This is called “blue heat embrittlement” of pure niobium following conventional metal engineering.

  When the blue heat embrittlement phenomenon occurs, it will lead to a decrease in plastic deformability due to a decrease in ductility and a decrease in deformation resistance to the external force of the material due to a deterioration in strength characteristics. The risk of necking in concentrated areas increases rapidly. Therefore, blue heat embrittlement must be avoided in the forging process.

  The cause of blue heat embrittlement is considered as follows. This is related to “selective use of fine-grained pure niobium” described later. As can be seen from the change in the flow stress of the stress-strain line in the hatched circle in the inset in FIG. 6, blue heat embrittlement is intrusion at grain boundaries and microslip (strain) generation sites in pure niobium material. This is due to sticking / blocking by solid diffusion of type atoms (carbon and nitrogen).

The diffusion phenomenon (diffusion coefficient D) in ferrite (body-centered cubic crystal (BCC)) such as pure niobium depends on the temperature T.
D = D _O exp (−Q / kT) Formula (2)
It is represented by
D _O : Frequency term, Q: Activation energy, k: Boltzmann constant

The atomic diffusion distance x at time t is
x = (Dt) ^1/2 formula (3)
It becomes.

  However, since D of carbon and nitrogen in the ferrite at 200 to 300 ° C. is about 100 to 1000 mm / sec, it matches with the micro-slip speed, so that the fixing action occurs and blue heat embrittlement occurs.

  As described later, the “selective use of fine-grained pure niobium” must be considered simultaneously with the “ease of plastic flow”.

-Minimized surface oxide film Pure niobium has a small standard formation free energy ΔG of oxide (mostly Nb ₂ O ₅ ) and is easily oxidized. As the removal of scale (oxide film), finish cutting (mechanical / chemical (Cp) / electrochemical (Ep)) or the like is performed after manufacturing a press forged product (in some cases, finish cutting). In particular, it is necessary to carry out Ep for every “9-spindle cavity” that is planned to produce less than 20,000 units. Therefore, reducing the oxide film generation as much as possible contributes to the improvement of the EP processing capability, leading to cost reduction.

  Therefore, the forging temperature never exceeded the lowest possible value between the temperature exceeding room temperature (temperature not including room temperature) and 200 ° C., but at the same time avoiding blue brittleness and the stress inserted in FIG. 6 as described above. -Including the response to changes in flow stress near the elastoplastic limit shown in the strain diagram). The cause of this is the same as blue heat embrittlement, and as mentioned above, is due to the fixation of microslip strain of interstitial atoms, which is also called aging phenomenon and can occur even in the high temperature range below the blue heat embrittlement lower limit temperature There is sex. At the same time, considering the ease of plastic fluidity, which will be described later, it is preferable to control the temperature range from 100 to 150 ° C. around 130 ° C.

・ Plastic flow facilitating forging process is progressed mainly by material deformation due to compressive force, so how to cause macro plastic flow of pure niobium material appropriately, uniformly and appropriately along the required product geometry. It is important.

  To that end, it has excellent ductility (particularly uniform elongation) indicated by the total elongation (sum of uniform elongation and local elongation) of the macro mechanical properties, and lowers strength and flow stress to reduce deformation resistance. It is desirable to keep Then, it is desired to avoid the fixing action against the micro deformation strains of the carbon and nitrogen interstitial atoms described above.

  From this point of view, referring to FIG. 6, it can be understood that it is essential to control the temperature in a low temperature range between a temperature exceeding room temperature (a temperature not including room temperature) to 200 ° C., but preferably the surface oxide film is minimal. It can be said that it is preferable to select temperature range control around 130 ° C., which is consistent with the viewpoint described for the conversion temperature. This suitable temperature varies slightly depending on the type of metal material.

Thus, the formation and high accuracy of all curved surfaces during forging and the surface properties are improved. The present invention derived from the development research experiment and the theoretical teaching principle, that is, the technology that realizes all press working of pure niobium material has not been known so far.

-Selection of fine crystalline pure niobium material There are two points to consider. The first point is the viewpoint of avoiding the seizure (adhesion) phenomenon that occurs between the thick pure niobium plate material 5a and the mold. Pure niobium usually has a large crystal grain growth rate by recrystallization heat treatment, and generally exhibits coarse grains of about several hundred μm.

  This is because pure niobium used for the present application has a high purity of 300 RRR or more (the content of interstitial impurity elements such as carbon and nitrogen is about several ppm), so that the action of preventing grain boundary movement is small, This is probably due to the fact that body diffusion is easy.

  When the crystal structure of the material to be processed is composed of coarse grains, the interaction of atoms by random walk between the surface and the mold surface increases more stochastically than in the case of fine-grained materials, and chemical reactions also occur. The seizure (adhesion) phenomenon is reduced by using a pure niobium material having a fine crystal of several tens of μm on the presumption principle that seizure and wear phenomenon are facilitated.

  It has not been known so far that the crystal grain size of pure niobium is one of the causes of seizure and adhesion. Further, a technique for adjusting the crystal grain size to the order of several tens of μm is not disclosed.

  The other point is that, as can be understood from the above-mentioned fact about the blue heat embrittlement and aging phenomenon in FIG. 6, by using a fine material having a crystal grain size of about 1/10 as above, The grain boundary area increases significantly, so that many of the interstitial elements such as carbon and nitrogen are diffused and fixed (trapped) at the grain boundaries even at the same temperature, reducing the extent to which the microslip is hindered. That is. That is, in the forging process under the same temperature condition, the fine-grained material is less susceptible to blue heat embrittlement and aging than the coarse-grained material, the forging process is facilitated, and the forgeability is improved.

・ To prevent seizure (adhesion) between the surface-modified mold and the thick pure niobium plate 5a and to prevent friction and wear of the mold, the surface of the mold is subjected to DLC, low-temperature nitridation or chemical conversion treatment, etc. Reform with. Considering that the material to be processed is soft pure niobium, consideration is given to the thickness of the modified layer and the surface treatment, and at the same time, the selection of the mold material is considered.

-Use a solid film lubricant with proper lubricant temperature-independent lubrication performance. For example, a lubricant that does not change the lubrication performance of a solid coating from room temperature to 800 ° C., which is one of the inventors of the present application, is known (Patent Document 3). Alleviated. The lubricant described in Patent Document 3 is a solid lubricant that avoids the burden on the human body / environment of the chlorine-added lubricant that has been used in the past to prevent seizure and adhesion, and contributes to the improvement of workability. To do.

・ Servo (speed / motion) control This function is installed in a conventional press machine to control the speed and / or motion of the slide (stroke) of the press machine, and to change the usage requirements of external force. It is intended to improve the plastic workability by improving the affinity of the micro pure and macro deformation modes of the meat pure niobium plate material 5a.

  Since the present invention has been described in detail, specific examples based on these will be described below with reference to FIGS. The present invention is not limited to the following examples.

  FIG. 7 shows a photograph of the appearance of facilities and apparatuses for carrying out the invention. The main device was a press machine, and an electric (AC) servo mechanism was mounted on a conventional press machine, and a servo die cushion and a multi-action die were attached. Basically, from the viewpoint of cost performance, single-shot machining was used in the examples. That is, the new shear punching process for processing the shaped article 5b and the new forging process for processing the product before the finishing process were performed for each appropriate number. (Needless to say, during mass production, continuous processing is performed with two press machines).

  Therefore, the shear punching die and the forging die were exchanged on the way. QDC was used for exchanging heavy metal molds. The mold material for the example is SKD11, the surface modification is DLC, and the thickness of the modified layer is about 2 μm. A solid lubricant G2578T (manufactured by Nippon Tool Oil Co., Ltd.) was used as the lubricant. These mold material, surface modification, and lubricant were used for both shear punching and forging.

  The temperature control device 7 shown in FIG. 7 was used for cooling control of the new shear punching process and heating control for the new forging process. The temperature control range was −20 to + 300 ° C., cooling was a non-fluorocarbon refrigerant, and heating was an electric heater embedded in the mold 7a. Although there was a slight time difference in temperature control between the thick pure niobium plate 5a and the mold, there was no particular problem.

  As the pure niobium workpiece, a thick pure niobium plate having a thickness of 10 mm was used. This is obtained by performing EBM (electron beam melting) several times, performing ingot lump rolling and thick plate rolling, and vacuum annealing after descaling. According to the material mill sheet (inspection table), carbon, nitrogen, oxygen, etc. of impurity solid solution atoms are all at the level of several ppm, and RRR (an index related to electrical resistance. Was 341. The tantalum content of the same group (Group 5 of the periodic table) was 280 ppm. The metal crystal grain size is approximately 100-300 μm and is approximately equiaxed. The crystal orientation texture has not been measured. When the hardness was measured, it was about 90 in terms of Vickers hardness.

The conditions of the example are as follows.
(1) Shear punching: (Fine) Clearance 40 μm; Plate presser load (Pb) 20 tons; Plate presser surface pressure 140 kg / cm ^ 2; Binding load (F) is the same as surface pressure; Punch load (Pf) 90 tons Reverse presser load (Pp) 13 tons; speed 200 mm / sec; cooling temperature 0 ° C .; servo motion is straight;

(2) Forging: Forging load 160 tons; Forging speed 0.5 mm / sec; Forging die shaped part 5b Workpiece offset 0.2 mm; Processing temperature 130 ° C .;

  Under the above conditions, typical examples of the processed products 5b and 5c performed by the new shear punching method of a large number of HOM antennas 5 from the thick pure niobium plate material 5a and the subsequent new forging method according to the present invention. Is shown in FIG.

  FIG. 8A shows the shear punching shaped product 5b, but the shear punching of the soft thick pure niobium plate material 5a having a high processing difficulty reaching a plate thickness of 10 mm could be performed without any particular problems. . Of course, there was no embedding of abrasive grains in the water jet shaped article processing, and this problem could be solved completely.

  FIG. 8B shows a product (processed product 5c) after forging (before finishing (cutting) processing) by the new forging method, which is the continuous processing from (A). It was shown that a processed product having a required shape and dimension can be manufactured with reproducibility by applying means and conditions.

  A considerable number of pieces were forged, but no “necking” occurred in the conventional cold forging. FIG. 8 shows the length and thickness of each of (A) and (B), and it has been confirmed that there is no problem in the subsequent finishing process.

  In particular, the plate thickness is reduced by 1 mm due to forging, and the length dimension is also reduced. However, these are within the assumption, and as described above, the offset amount with respect to the design drawing is properly considered in the mold.

  As can be judged from the above embodiments, the application of the present invention presses all the manufacturing processes except for the finishing process, which avoids conventional cutting and water jet, from the thick pure niobium plate material 5a to the processed product of the HOM antenna 5. The result that it was possible to change to the processing method was obtained. Accordingly, it has become possible to realize a reduction in material yield, cost reduction, and improvement in mass productivity of acceleration cavity parts, which has been a major bottleneck.

  Next, as an example of the present invention, manufacturing (molding) of the nozzle vane 10 (FIG. 9C), which is an important part of a variable wing turbocharger for a diesel engine, using a new shear punching method and a new forging method A method will be described.

  The shaped product 8 shown in FIG. 9A is obtained by applying a new shear punching method to a rolled material of a stainless steel plate (SUS310S = 25Cr-20Ni-0.06C) having a thickness of 10 mm. At this point, the shaped product 8 is a punched flat T-shaped plate. This is the next step, and the present invention is a product comprising a blade portion 8a forged and formed on the blade 9a, and a shaft portion 8a forged and formed on the cap 9b and the shaft 9c.

  Conventional nozzle vane shaped products are often formed by fine blanking (FB) or rolling, but the cost of introducing the FB device is high, and high operation techniques are required, making it an expensive product. Yes. At the same time, problems such as high forming difficulty, yield, and cost are unavoidable in the next process (cold forging and rolling).

  In general, a “precision casting” method using SCS21 (25Ni-20Cr-0.3C) of stainless steel for casting is employed as a manufacturing means of this product. However, in this case, for example, the production amount of this product is said to be several hundred thousand pieces / month, and difficult problems such as mass productivity, cost, delivery date, and distribution are piled up in production by precision casting. In addition, SCS21 contains a large amount of C, and generates Cr carbide, σ phase non-metallic inclusions or Laves phase with temperature change during use, lowering oxidation resistance and causing poor operation and deterioration of durability. In addition, there is a risk of sensitization (intergranular corrosion) and embrittlement (cleavage fracture / intergranular fracture).

  The forged product 9 shown in FIGS. 9B and 9B was obtained by applying a new forging method using plastic flow to the shaped product 8. FIG. 9B 'is a photograph from the wing 9a side of FIG. 9B. Here, the forging temperature is set to 150 ° C., the servo control is performed, and the cap 9b is forged by a combination technique of partially punching, and the blade 9a having a special shape is forged. Depending on the parts, the final product will be produced by new forging. In the nozzle vane, the following cutting process is performed to obtain a finished product.

The nozzle vane 10 shown in FIG. 9C was completed by subjecting the forged product 9 to necessary cutting to form the cutting portions 10a and 10b. Through the above steps, it is possible to manufacture a nozzle vane having productivity and economy. Depending on the parts, finishing is performed by various kinds of polishing that are optimum and necessary, and a finished product is obtained.
For example, according to conventional cold forging methods such as special gears, cams, levers and split rings belonging to the category of precision machine parts, as the severity of shape and dimensional accuracy increases, the dimensions of necking, cracks and R part Although an increase in the occurrence rate of defects such as defects, drool, burrs, and excess meat is inevitable, the method of the present invention solves these technical problems. This is mainly due to the improvement of the plastic fluidity and deformation margin of the material. At the same time, mass productivity and economic efficiency are almost the same as those of the conventional cold forging method.
The harmonic coupler (HOM Coupler) of the superconducting accelerating cavity terminal component of the cutting-edge project ILC (International Linear Collision Accelerator) was implemented with high-purity Nb material. Is obtained. As a unique effect based on the embodiment, the new forging of the present invention can be applied to a shaped product obtained by using a new shear punching method for a metal material, such as the above HOM Coupler part (antenna). It can be commercialized by applying processing methods.
It is impossible to process such complicated shapes and high precision products without using cutting, high energy processing methods, casting methods, fine blanking or rolling by multiple processes. However, the fact that processing is possible by the new forging method together with the new punching method means that the production time and efficiency are greatly increased by 1 to 1/100, and therefore, it has an excellent and favorable effect.

  In addition, for example, applied to automotive turbocharger (supercharger) parts such as nozzle vanes, link plates and slide joints made of stable high-grade stainless steel (SUS310S or SUS316L, etc.) currently manufactured by the fine blanking method. Thus, it can contribute to the effective use and purification function of output, torque, and exhaust gas at high temperature and long time use.

  From the above, the technology of the present invention has found a new technology that combines temperature, speed, external force, etc. from the viewpoint of utilization and integration of material engineering and plastic processing, and has led to the creation of specific new means for that purpose. It is.

  The most unique effect is that they have found the possibility of replacing the existing fine blanking precision punching method. Specifically, compared to investing in fine blanking dedicated machines, it is much cheaper to deal with and means, that is, the modification of general-purpose presses already owned by each manufacturer and the preparation of temperature control mechanism Metal products using a new high-precision new shear punching method without the need for complicated work techniques and the need to prepare expensive special molds for fine blanking Realized the manufacturing method. Even when compared to a processing manufacturer that already owns a fine blanking machine and has already depreciated, the new shear punching process is superior over the medium term.

  As described above, the techniques of macroscopic plastic mechanics, heat treatment and servomechanism related to shear processing in micro-clearance, especially material deformation engineering, separation shear processing in plastic processing, and their interaction with material processing deformation. Through various examinations and experiments, various metal materials, including steel materials, have various shapes up to a thickness of about 10 mm. They have good shape, good surface properties, and punched side surfaces with minimal required dimensional accuracy, sag and burr. It is possible to manufacture a punched product under appropriate shear punching conditions in consideration of the plastic flow of the material, such as securing a 100% shear surface, plate thickness change and distribution, and local small R out of the loop.

  As a result, the present invention provides precision punched parts and products that require high profile and high precision, and does not rely on the fine blanking method that requires expensive dedicated press machines, but includes cooling jigs and equipment on conventional press machines and dies. It is also provided with a servo function for 3-axis external force control including stroke, automatic surface pressure control and back pressure to enable precision shear separation processing.

Even without using the expensive and difficult-to-use fine blanking method, high-speed heat removal, surface pressure control, material movement and compression resistance of the material at the time of shear punching are taken into consideration, and parts with high shape and dimensional accuracy・ Manufacturing of products and shaped products is possible under conditions of minute width and good material yield.
In addition, by adopting a new forging method, as described above, good plastic flow is produced, so that blue heat embrittlement, aging effect, oxidation, necking, shape defect, excess / insufficiency, sagging, burr (burr) It is possible to commercialize a molded body that avoids the above-mentioned by a finish cutting unnecessary or a minimum finish cutting.

DESCRIPTION OF SYMBOLS 1 Superconducting high frequency acceleration cavity 2 Center part 3 End group part 3a Beam pipe 3b Port pipe 3c HOM coupler 4 HOM cup 5 HOM antenna 5a Thick-pure niobium plate material 5b Shaped product 5c Work product 6 Binding means 6a Die 6b Plate retainer 6c Punch 6d reverse presser 6e minute clearance 6f binding jig 6g binding jig 6h binding jig Pf punching load Pb plate presser load Pp reverse presser load F binding load F1 first side binding force F1 'counter load F2 second side binding force F2 ′ Counter load 7 Servo press machine 7a Mold 7b Temperature control device 8 Shaped product 8a Blade 8b Shaft 9 Forged product 9a Blade 9b Shaft 9c Shaft 10 Nozzle vane 10a Cutting part 10b Cutting part

Claims (7)

It is characterized in that a shaped product formed from a metal plate material is formed into a processed product by avoiding blue heat embrittlement by low temperature region temperature control at 200 ° C. or less, which is different from the hot, warm and cold forging temperature regions. A metal product manufacturing method using a new forging method. 2. The production of a metal product using the new forging method according to claim 1, wherein the low-temperature temperature control of the forging is temperature control that minimizes generation of a surface oxide film of the shaped product. Method. The method for producing a metal product using the new forging method according to claim 1, wherein the low temperature range temperature control of the forging is temperature control for facilitating plastic fluidity of the shaped product. The method for producing a metal product using the new forging method according to claim 1, wherein the metal plate material has a fine grain structure with a grain size of several tens of μm. The die used in the forging is a surface-modified die for preventing seizure, and a solid film lubricant having temperature-independent lubrication performance is used for a workpiece. A method for producing a metal product using the new forging method according to claim 1. The method of manufacturing a metal product using the new forging method according to claim 1, wherein the forging includes servo control of a press and includes speed and motion control. (A) a shear punching process for forming a shaped product from a metal plate material;
(B) In order to form a processed product having the shape of the shaped product, temperature control of the mold and the shaped product for avoiding blue heat embrittlement and facilitating plastic flow of the shaped product. A heating device to perform, a mold whose surface is modified to improve moldability and minimize surface oxidation of the molded product, and a temperature-independent solid coating for preventing seizure between the molded product and the mold It consists of a type of lubricant and a forging process different from any of hot / warm / cold forging, in which the press machine is equipped with a servo mechanism that controls the speed and motion of the new shear stamped shaped product,
A metal product manufacturing method using a new forging method, wherein the metal product cutting or water jet processing is converted into a press method.