TWI390055B - Alloy and method for producing alloy - Google Patents

Description

Alloy and method of manufacturing alloy

The present invention relates to an alloy having a low coefficient of thermal expansion for use in a structural part of a precision instrument or the like, and a method of manufacturing the same.

In general, there have been reports of temporary deformation of Invar alloys (Fe and 36% Ni), which are low thermal expansion metal materials (refer to Physics and Applications of Invar Alloys, Honda Memorial Series on Material Science No. 3, AGING AND PRECIPITATION 1978, Maruzen). This publication uses the term "gamma expansion" and speculates that the cause of gamma expansion is the carbon contained in the alloy.

In addition, there is also an example of the problem of temporary dimensional change of the metal material used in the structural portion of the precision device after a long time (refer to Japanese Patent Application Laid-Open No. H08-269613). The reason for this is the result of the release process of the internal residual stress imparted during the manufacturing process (e.g., heat treatment and the like). This publication reports that although the cast iron type is a low thermal expansion alloy having a carbon content of 0.3 to 2.5% by weight, low thermal expansion can be achieved by reducing the localization of Ni.

With regard to the release of internal residual stress in the latter publication, this is a known phenomenon in the manufacture of metal parts, and the procedures and processes for suppressing such phenomena have been performed in the manufacturing method of precision parts.

On the other hand, the publication on the previous item is still in the academic stage. Even among those skilled in the art, the fact is: this phenomenon is still not well known. The reason is considered to be that the absolute amount of temporary deformation caused by the gamma expansion phenomenon is smaller than the temporary deformation caused by other general phenomena.

In addition, in recent precision devices that are more and more sophisticated, Super Invar alloys having a coefficient of thermal expansion of less than 1 ppm (= 1 × 10 ^-6 )/degree at a temperature close to room temperature are more preferably used instead of Invar. alloy. Of course, although some inorganic materials have a coefficient of thermal expansion of less than 1 ppm/degree, the manufacturing method of such materials is extremely difficult, such as cutting treatment and the like. Additionally, because such materials are not extremely tough, the materials may be damaged during the manufacturing process. Furthermore, since such a material has a small thermal conductivity, when a localized temperature distribution is generated in the element, partial expansion may occur, and characteristics having a small coefficient of thermal expansion may not be fully utilized. Therefore, it is necessary to skillfully use the Super Invar alloy while taking advantage of its characteristics.

However, regardless of whether the gamma expansion phenomenon occurs in the same manner as in the Invar alloy, the Super Invar alloy has not been understood.

In addition, for highly sophisticated optical instruments, the performance of the instrument can gradually deteriorate over time as temporary deformation of important structural parts results in a change in the length of the optical path. Therefore, in the investigation process for obtaining the present invention, in order to suppress the known individual phenomenon of causing temporary deformation of the metal material, a Super Invar alloy was prepared in which the general treatment was diligently performed. Even so, temporary deformation still exists, and the amount of such deformation (the amount of temporary deformation of 5 ppm per year) is such that it cannot be ignored, and it becomes a cause of deterioration of optical instrument performance which becomes gradually more sophisticated in the future. If a micro-deformation evaluation system that contributes greatly to the present invention is used, the amount of temporary deformation that has generally been neglected becomes apparent.

It is an object of the present invention to provide an alloy which suppresses slight temporary deformation of the Super Invar alloy as much as possible; and a method of making such an alloy.

In view of the above problems, the alloy of the present invention includes iron, nickel and cobalt, which are essential components of the Super Invar alloy, and the present invention is characterized in that the fraction which has not been carbonized in the carbon contained in the alloy is 0.010% by weight or less.

Further, the method for producing the alloy of the present invention is a method for producing an alloy comprising the essential components of the Super Invar alloy - iron, nickel and cobalt, the method comprising the steps of: adding a carbide forming element to the basic And melting and casting the obtained mixture; hot forging at a predetermined temperature; and performing a first heat treatment at a first temperature lower than the predetermined temperature to precipitate an element formed by carbon and carbide contained in the alloy The formed carbide is in the base phase.

The present inventors have found that the slight temporary deformation of the Super Invar alloy is caused by the uncarbonized portion of the carbon contained in the alloy.

Further, if the alloy of the present invention is used, minute temporary deformation of the Super Invar alloy can be suppressed as much as possible (especially 2 ppm (2 × 10 ^-6 ) or less on an annual basis).

Further, according to the method of producing an alloy of the present invention, even if only a trace amount of a carbide forming element is added, the carbide forming element is effectively combined with carbon to form a carbide. Therefore, the portion which has not been carbonized in the carbon contained in the alloy may be 0.010% by weight or less. Therefore, it is possible to manufacture an alloy which suppresses temporary deformation as much as possible while maintaining a low coefficient of thermal expansion.

Further features of the present invention will become apparent from the Detailed Description of the Drawings.

[Best Mode for Carrying Out the Invention]

The invention will be described in more detail with reference to the drawings. In addition, the same structural elements have the same reference numerals in principle, and thus the description thereof is omitted.

(alloy)

The alloy of the present invention includes iron, nickel, and cobalt, which are the basic components of the Super Invar alloy. This alloy is characterized in that the portion of the carbon which is inevitably included in the alloy which has not been carbonized is 0.010% by weight or less.

Super Invar alloy has iron, nickel, and cobalt as essential components, and its thermal expansion coefficient is even lower than that of Invar alloy (Fe 63.5 wt%, Ni 36.5 wt%). The basic composition of the Super Invar alloy is Fe 63.5 wt%, Ni 31.5 wt%, and Co 5.0 wt% by using Co instead of 5% by weight of Ni in the Invar alloy.

In the present specification, "basic component" means a substantial component of a Super Invar alloy.

In the alloy of the present invention, the content range of the above basic components can be explained as follows.

The Co content may be 2.0% by weight or more and 8.0% by weight or less, and may additionally be 3.0% by weight or more and 7.0% by weight or less.

The Ni content may be 30.0% by weight or more and 38.0% by weight or less. Here, when the following carbide forming elements (for example, Ti and Nb) are added in an amount higher than the minimum required amount for fixing the carbon, the excess carbide forming element forms a compound with Ni. Therefore, in this case, if the amount of Ni forming a compound with the excess carbide forming element is considered, it is necessary to include a larger amount of Ni. Therefore, the upper limit is 38.0% by weight. However, when a minimum required amount of carbide forming element is added, the upper limit is about 34.0% by weight.

The Fe content may be 62.0% by weight or more and 68.0% by weight or less, and may additionally be 63.0% by weight or more and 67.0% by weight or less.

The present invention produces a Super Invar alloy which has been subjected to a general treatment to suppress a known phenomenon as a cause of temporary deformation of a metal material such as Invar alloy or the like. Even so, there is still a temporary deformation of about 5 ppm per year. Although described in more detail below, the inventors have discovered that the cause of such temporary deformation is the amount of free carbon. Although described in more detail below, the general treatments described above include, for example, slow cooling (furnace cooling) and sub-zero processing.

Here, in the present invention, the unbound carbon formed by the non-carburization of carbon contained in the alloy is referred to as "free carbon". In particular, "free carbon" means solid solution carbon, such as interstitial carbon. From the results of this experiment, it can be inferred that free carbon is the cause of temporary deformation because free carbon intrudes into the crystal lattice and moves in the crystal lattice.

If the amount of free carbon is 0.010% by weight or less, the temporary deformation can be suppressed to 2 ppm or less on an annual basis. In addition, the amount of free carbon is more desirably 0.005% by weight or less. A lower limit of 0.0005 wt% or less can be achieved.

In the alloy of the present invention, the total content of carbon in the alloy, particularly the carbon content inevitably contained in the alloy, may be 0.010% by weight or less. When a Super Invar alloy is obtained by a general industrial process, the total content of carbon is usually from about 0.010% by weight to 0.030% by weight or less. Therefore, it is perceived that even if the total content of carbon is 0.010% by weight or more, temporary deformation can be effectively suppressed as long as the free carbon is 0.010% by weight or less.

To ensure that the carbon that is inevitable in the alloy is not as free as possible, the alloy of the present invention may include a carbide forming element. In the present invention, a "carbide forming element" is an element which can combine with carbon in an alloy to form a carbide. At least a portion of the carbide forming elements combine with the carbon in the alloy to form a carbide, and the formed carbide is dispersed in the base phase. As long as the carbon atoms are fixed as carbides, the amount of free carbon can be reduced.

It is desirable to include a carbide forming element in an amount larger than the total content of carbon based on the atomic % comparison, otherwise the free carbon which is not fixed into a carbide remains.

The content of the carbide forming element is desirably 0.05% by weight or more. This is because this content is such that free carbon having a total content of carbon equivalent to 0.01% by weight is fixed. On the other hand, in order to maintain the coefficient of thermal expansion of less than 1 ppm/° C., the content of the carbide forming element is desirably 0.50% by weight or less. The particular importance of these values will be described below. Further, the lower limit is more desirably 0.10% by weight. The upper limit is more desirably 0.30% by weight. The reason for this is as follows. If the content of the carbide forming element is too low, the carbon in the alloy cannot be fixed to the carbide, so that the temporary deformation cannot be effectively suppressed. On the other hand, if the content of the carbide forming element is too high, some of the carbide forming elements cannot be combined with carbon and remain, and the coefficient of thermal expansion is increased. As a result, the desired characteristics of the Super Invar alloy cannot be achieved.

It is desirable to make the amount of carbide-forming elements that do not form carbides as low as possible. If the amount is 0.50% by weight or less, a low coefficient of thermal expansion can be maintained, which is characteristic of the Super Invar alloy.

In the present invention, it is desirable to form a compound phase between nickel and a carbide forming element. The carbide forming element, as described above, does not form a carbide and remains to bond with the basic component Ni of the alloy. As a result, an increase in the coefficient of thermal expansion can be suppressed, and the strength of the alloy can be increased.

Examples of the carbide forming element include titanium (Ti) and niobium (Nb).

(lens holding element, optical instrument)

The alloy of the present invention can be suitably used for a lens holding member. Figure 11 is a cross-sectional view of a lens barrel using the frame member 8 of the present invention. In Fig. 11, a lens 7 made of quartz having a low thermal expansion (0.6 ppm/degree) is fixed on a frame member 8 having the same thermal expansion coefficient. In addition, the outer casing 9 supports the frame member.

Since the coefficient of thermal expansion is the same as that of the lens, the light passing through the lens (optical path) does not change even if a temperature change occurs.

In addition, since the frame member uses the alloy of the present invention, it hardly undergoes temporary deformation so that the frame member does not participate in the deformation of the lens fixed thereto. Therefore, since optical errors (such as aberrations) do not occur after a long time, the characteristics of the instrument using this barrel do not change.

Desirable examples of optical instruments for identifying the advantageous effects of the present invention and requiring nano-precision include, but are not limited to, exposure instruments used in the manufacture of semiconductor devices, and optical instruments such as those used in space can also be used.

(Alloy manufacturing method)

The alloy of the present invention can be manufactured as follows, for example:

If the total content of carbon can be suppressed to 0.010% by weight or less, it is apparent that the amount of free carbon is also within this range. Although it is possible to suppress the total carbon content to 0.010% by weight or less by performing complicated refining techniques such as VAR (vacuum arc remelting) and ESR (electroslag remelting), it is difficult to achieve by conventional industrial methods. of.

Further, even for a Super Invar alloy having a total content of carbon of 0.010% by weight or more, by casting a carbide-forming element such as Ti, Nb, and the like, the resulting mixture is melt-cast and hot forged at a predetermined temperature, carbon An alloy in which free carbon is suppressed can be obtained by fixing Ti and the like.

However, as described above, it is desirable to avoid adding an excessive amount and a minimum amount of carbide forming elements. In addition, although it is desirable to react all of the carbide-forming elements with carbon at exactly the same ratio, this is difficult in real implementation because the amount of carbon present is inevitably variable. Therefore, it has been found that in order to obtain carbides from the added carbide forming elements as efficiently as possible, the following manufacturing method can be carried out.

First, a carbide forming element was added to the basic component, and the resulting mixture was melt-cast by a 50 kg vacuum induced melting furnace.

The mixture is then hot forged at a predetermined temperature. The predetermined temperature may be 1000 ° C or higher and 1100 ° C or lower.

Further, by performing the first heat treatment at a first temperature lower than the predetermined temperature, carbides formed of carbon and carbide forming elements contained in the alloy may be precipitated in the base phase.

The first temperature is not necessarily a constant temperature, and the first heat treatment can be performed by maintaining a gradually decreasing temperature. However, it is desirable to maintain the temperature within a predetermined range. This is because if the temperature is too high, the formed carbide decomposes; but if the temperature is too low, the carbide forming element and carbon are difficult to bond. Based on this point of view, the first temperature needs to be 825 ° C or higher and 950 ° C or lower.

The importance of the manufacturing method of the present invention is that the method does not reduce the carbon content by using expensive refining techniques; conversely, during a typical melting and casting manufacturing process, even if a small amount of carbon atoms are inevitably present, The method suppresses the undesired effects of carbon atoms and does not increase the coefficient of thermal expansion.

Further, after the first heat treatment, a compound phase of nickel and a carbide forming element may be formed by performing a second heat treatment at a second temperature lower than the first temperature. As a result, an excessive amount of carbide-forming elements which do not contribute to carbide formation can be suppressed as much as possible so as not to cause an increase in the coefficient of thermal expansion, thereby improving the strength of the alloy.

The second temperature may be 700 ° C or higher and 750 ° C or lower.

Further, after the second heat treatment, the third heat treatment is performed at a third temperature equal to or higher than room temperature to a temperature lower than the Curie temperature of the alloy. As a result, free carbon that cannot be converted into carbides can diffuse to the stable position of the Super Invar alloy. Temporary deformation can be further reduced by applying the so-called artificial air drying effect.

The third temperature may be 25 ° C or higher and 150 ° C or lower. This upper limit can be further reduced to 120 °C.

Instance (about the reason for temporary deformation)

First, using the components of the equivalent materials of Super Invar alloy and Super Invar alloy, a procedure was created to recursively infer the cause of temporary deformation that has generally caused problems. In particular, unlike the typical temporary deformation, a hypothesis that a carbon atom has some influence on temporary deformation is created.

The following three procedures are performed to reduce the temporary deformation: (i) reduce the amount of carbon atoms as a cause to the extent that no problem is caused; (ii) fix the carbon atoms by some procedure to prevent inevitable inclusion of carbon atoms And (iii) the stabilization of the metal structure for a period of time (so-called "air drying").

As a result of this investigation, it was found that all of these procedures are effective in reducing temporary deformation. This result is related to the fact that the carbon atom is the cause. In addition, this result indicates that the inclusion of carbon atoms is not a problem in itself, but the problem is in the state of the carbon atoms present in the metal structure. In other words, it is preferred that the carbon atoms do not diffuse into the crystal lattice at a temperature close to room temperature.

The low thermal expansion alloy of this specific example and its method of manufacture utilize what is considered to be the best method today. In particular, care must be taken during the melt casting step to prevent intrusion of impurities. The inevitable carbon content is suppressed, and a trace amount of an element is added to form a carbide by strong bonding with carbon atoms. In addition, a suitable heat treatment is performed to effectively precipitate the carbides, so that the amount of free carbon (meaning carbon of the solid solution carbon or voids) is lowered.

The various constituent materials formed by the addition of carbide forming elements to the original Super Invar alloy are referred to herein as "Super Invar Alloy Equivalent Materials."

(Investigation of various phenomena as a cause of temporary deformation)

Super Invar alloy for precision optical instrument parts consists of 31.5% Ni (nickel), 5% Co (cobalt) and the rest of Fe (iron).

If the dimensional change of the material is measured at a high precision controlled constant temperature (23 ± 0.01 ° C), it is found that at the initial stage after the part is manufactured, the extension is about 0.5 ppm on a monthly basis. However, depending on the manufacturing batch of the alloy, this stretch is not uniform and there is greater stretch in certain batches. If it is assumed that the cause is due to heat activation treatment phenomena (such as diffusion and the like), the rate of change should decrease over time. Even so, from the measurement results of the size change of several alloys on tens of days, it is known that the deformation after about one month from the end of the last processing can be obtained as a linear change versus time elapsed relationship; Measurements up to the 10th can also be used to estimate the extension based on the month.

However, it is often difficult to change based on the metal structure to indicate the reason for the dimensional change in the metal structure. If the conditional processing method can be used to obtain the improvement, it is reflected that the processor is generally assumed to be the cause. Even with the development of high-resolution electron microscopes, even a slight change in atomicity can be said to be impossible to detect directly in its original state even for metal structure changes. Therefore, the reasons must be inferred based on the data from other inspections, experiments, and analyses, and similar understandings. And in the present invention, the following individual phenomena are first checked as the cause of this temporary deformation, and then the reason is reduced by the deletion method.

(1 - About the reduction of spontaneous magnetization)

In the Super Invar alloy, as with the Invar alloy, the normal atomic distance depending on the thermal shock of the atom is amplified because of the spontaneous magnetization characteristic of these alloys. As the temperature increases, this degree of spontaneous magnetization is reduced. Therefore, this spontaneous magnetization is to reduce the normal amplification of the atomic distance caused by the increase in temperature. As a result, the Super Invar alloy exhibits a very small coefficient of thermal expansion at a Curie temperature or lower, and the coefficient of thermal expansion returns to normal above the Curie temperature. Therefore, if the spontaneous magnetization does not decrease with time, the volume moves in the decreasing direction, which is contrary to the stretching (expansion) phenomenon that occurs today. Therefore, this phenomenon is not considered.

(2-about precipitation phenomenon)

At approximately room temperature, all of the constituent elements of the Super Invar alloy, Fe, Ni, and Co, have very small self-diffusion coefficients, and thus diffusion of these atoms is difficult to consider.

However, although an atom having a small atomic radius (for example, carbon) does exhibit void diffusion due to diffusion at room temperature, it cannot be confirmed whether or not a certain stable phase is generated (for example, graphite, cementite, and the like). .

In addition, with regard to temporary dimensional changes in the range of room temperature (which is Curie temperature or lower) to 210 ° C, reversible expansion (this abnormal thermal expansion) and shrinkage are found, as this is a key point and will be More detailed description. It cannot be denied that there is still the possibility of precipitation even in this low temperature range. However, it is difficult to believe that the precipitated material will redissolve and form a solid solution again. Therefore, since this phenomenon is not reversible in the above temperature range, it is excluded from the cause of temporary deformation.

(3-About the release of internal residual stress)

This phenomenon is a process in which internal stress is used as a driving force, and the dislocation density is lowered as a result of the movement and disappearance of dislocation (this is a lattice defect). Therefore, the volume can be considered to move in the decreasing direction. However, for this reason, the use of this material was carried out to compare the temporary deformation between the material obtained by air cooling from 315 ° C and the material obtained by the furnace cooling, but no difference was found. Therefore, this phenomenon is also excluded.

(4-about martensitic conversion)

This phenomenon involves an increase in volume. However, the unique and high-precision dimensional change measurement performed in the present invention is carried out at a position controlled at 23 ° C ± 0.01 ° C. However, for this alloy, it can be considered that this conversion does not occur at a constant temperature. This is because, unlike typical tool steels and the like, for the nickel-containing iron-based low heat coefficient alloy, the stability phase at room temperature is initially an austenite phase.

In addition, the stress applied to the alloy did not change during the dimensional change measurement. Therefore, the stress-induced transition will not develop. However, in spite of this, materials which are treated at a low temperature of -10 ° C (sub-zero treatment) and materials which are not subjected to such treatment are used. As a result, no difference in the amount of temporary deformation was found. Therefore, this phenomenon is also excluded.

(5-about creep)

Considering the amount of temporary deformation causing the problem, creep deformation caused by the weight of the sample itself may also be the cause. For a typical steel (which is usually a body-centered cubic lattice), the diffusion of void elements is apt to occur even at room temperature, so that strain aging is performed dynamically, and creep deformation is difficult to occur. In this regard, for such a face-centered cubic lattice alloy, the rate of diffusion of carbon is less than that for steel, so that strain aging is said to be not easily performed at temperatures near room temperature, and creep is more likely to occur.

Therefore, the strength in the range of the micro strain of various alloys was measured (at a permanent strain of 2 ppm = about 0.0002%). It can be said that the dislocation is less likely to spread and the creep resistance is larger because the strength of the alloy under this strain is larger. In the sample temporarily measured to be deformed, as expected, the high carbon material (C: 0.118% by weight) had a stronger strength than the low carbon material (C: 0.002% by weight). Therefore, if creep is the cause, the high carbon material should have a small amount of temporary deformation. Here, in the sample to be measured, the components contained in addition to carbon are indeed the same. It is also produced by melting both electrolytic iron and electrolytic nickel, and then additionally adding carbon for high carbon materials to prepare various samples. The temporary deformation measurement results will be described below.

(6-About gamma expansion)

The gap in the face-centered cubic (fcc) lattice of the austenite phase (gamma phase) is the center of the octahedron and the center of the tetrahedron, which even has a geometrically smaller gap. For example, if carbon atoms in the gap between the octahedral center positions spread at the center of the tetrahedron, the volume may expand. Due to the existence of spontaneous magnetization, carbon atoms can even settle in the position of small geometric gaps. If the gamma expansion is based on the diffusion between the adjacent gaps between the carbon atom lattices as described above, the amount of temporary deformation can be expected to be reduced for low carbon materials having little free carbon. In addition, since the deformation is not caused by the manufacture of a compound or the like, it is expected that the machine revolution is reversible with respect to temperature changes in the above temperature range. Although the reason for the temporary deformation will be described in more detail below, based on a series of investigations of the present invention, the cause of the temporary deformation can explain this phenomenon.

(by example alloy)

Table 1 is a list of various Super Invar alloys and Super Invar alloy equivalent materials prepared for measuring temporary deformation.

Table 1 also shows that in the case where the cause of the temporary deformation is creep, it is not easy to temporarily deform as predicted from a plurality of materials, or it is easier to temporarily deform than a general material. Table 1 also similarly illustrates the case when γ expansion is the cause.

Although the Super Invar alloy equivalent material (high-strength material, Examples 2 to 5) containing Ti and Nb completely contains the same carbon content as the general material, it is expected that the carbon will be a carbide, as expected for TiC and NbC. (The results of the analysis will be described below). Therefore, since the number of carbon atoms that are indeed movable should be small, it is expected that the temporary deformation may be lowered in either case where the cause is creep or the cause is γ expansion.

The hardness is recorded as an average value because the hardness of "about 120 HV" is in accordance with the hardness test position. In addition, "equal to 372HV" is actually a value obtained by converting the value of the result of the Rockwell hardness tester test into Vickers hardness.

Further, the DA material of a plurality of composition materials means a material obtained by hot forging, then air cooling, and then subjected to aging treatment. Further, the STA material means a material obtained by hot forging, followed by solution treatment, then water cooling, and then subjected to aging treatment.

(Method of manufacturing alloys according to the example)

The mixture was melt-cast by a vacuum induction melting furnace, air-cooled at 1000 ° C, and cooled by water after being treated at 830 ° C for 2 hours, and maintained at 315 ° C for 3 hours, and was subjected to stress release treatment for 3 hours. Stabilization treatment at 98 ° C for 48 hours (so-called artificial air drying, third heat treatment), and the manufacture of general materials, low carbon materials, high carbon materials and materials added with Nb (Examples 1, 6, Comparative Examples 1 and 2) .

In addition, melt casting was carried out by a 50 kg vacuum induction melting furnace, hot forging at 1000 ° C, aging treatment at 720 ° C for 6 hours (second heat treatment), and then stress release treatment at 315 ° C, and at 98 The stabilization treatment was carried out at ° C for 48 hours to produce high strength materials (Examples 2 to 5).

In addition, by hot forging at 1000 ° C, it was maintained at 900 ° C for 2 hours (first heat treatment), then gradually cooled to 830 ° C, air cooled from this temperature to room temperature, and then aged at 720 ° C. After the hour (second heat treatment), the stress release treatment was performed at 315 ° C, and the stabilization treatment was carried out at 98 ° C for 48 hours (third heat treatment), and a material to which a very small amount of Ti was added (Example 7) was produced.

(Ingredients contained in the alloy according to the examples of the present invention)

Table 2 shows the ingredients contained in various constituent materials.

(general materials, low carbon materials, high carbon materials)

A low-carbon material and a high-carbon material are separately produced by using a high-purity material manufactured by electrolysis as a raw material by changing only the carbon content and having the same amount of other elements.

(about high-strength materials)

Each high strength material has the same carbon content as a typical material and is manufactured to completely contain Ti and/or Nb.

The hardness test results are: after hot forging, materials 8-1 and 9-1 have a hardness of 36.6HRC (equal to 360HV) and 25.7HRC (equal to 270HV); and after solution treatment, materials 8-2 and 9-2 They have a hardness of 33.3 HRC (equal to 330 HV) and 18.9 HRC (equal to 234 HV), respectively. Since the hardness described in Table 1 is the value after the aging treatment (720 ° C × 6 hours), all the hardness values are increased by performing the aging treatment for the formation of the precipitate phase.

In addition, Ti addition has a more influence on increasing hardness than Nb addition. Ni forms a precipitate phase which is an aging treatment with a compound phase formed by Ti and Nb. Therefore, the Ni content is increased based on the content of the carbide-forming element, so that the matrix portion becomes a composition which exhibits the maximum Invar effect (effect of lowering the coefficient of thermal expansion).

(About the material to add Nb)

The material to which Nb is added is a material obtained by adding a small amount (0.24%) of Nb to a general material. The purpose of this material is to reduce the gamma expansion by combining the inevitable inclusion of carbon with Nb to fix the carbon to a carbide which is said to be the cause of the above carbon diffusion.

The atomic weights of niobium and carbon are 92.9 and 12, respectively. As described below, the niobium carbide confirmed in the present invention is NbC, and the atoms are bonded in a ratio of 1:1. Therefore, compared to carbon, there is still free carbon unless a helium of 7.74 times or more (=92.9/12) is added. In addition, since it is difficult to combine all of Nb with carbon atoms, it is desirable to add more than 7.74 times more than carbon. However, the addition of more Nb should be avoided as much as possible compared to the amount required to form the carbide. This is because Nb remaining without forming carbide remains, and if such residual ruthenium forms a solid solution in the matrix, the coefficient of thermal expansion increases. The same can occur with carbide forming elements other than Nb.

In the present example, since the carbon content is 0.017% by weight, it is desirable to add 0.13 wt% or more of Nb. Therefore, the Nb content was adjusted to 0.24% by weight.

Even in this case, it is desirable to subject the crucible formed in the solid solution to an aging heat treatment (second heat treatment) similarly to the use of the above-described high-strength material. This is because the hardness increases due to the formation of the precipitate phase of Nb and Ni. This aging heat treatment is performed to increase the strength value at the micro strain (micro yield point). This is because the present invention is concerned with solving the problem of minimal temporary deformation. The strength value under micro-strain is a residual permanent strain stress of 0.0001% (1 ppm). If this micro yield point can be increased, the creep resistance also increases. Under the above manufacturing conditions, this aging heat treatment was equal to 720 °C. Although the measurement here is to measure the temporary deformation when the low thermal expansion alloy is placed on a flat surface; in a real instrument, a stress greater than this state can be applied to the component formed by the low thermal expansion alloy. on. Therefore, it is even more desirable to improve creep resistance. In addition, even a small amount of alloy hardness is added to achieve the desired results in the cutting and grinding process. This is because it is easier to remove the swarf and the blockage of the grindstone is lowered.

Obviously, not only is the gamma expansion of individual high strength materials lowered, but the effect of suppressing creep deformation can also be expected. This is because the strength value under micro-strain is gradually increased by precipitation hardening and solid solution hardening by carbide-forming elements.

(About the addition of trace Ti material)

In consideration of the ideal case where all of the carbon in the alloy is inevitably used for the formation of titanium carbide, a minimum amount of Ti is added to the material.

Since titanium in a solid solution reduces spontaneous magnetization and effectively increases the coefficient of thermal expansion, a minimum amount of Ti is used to maintain a low coefficient of thermal expansion.

However, although the results can significantly reduce the temporary deformation, the component blend cannot be adjusted to just enough Ti value. That is, since the carbon content is 0.023% by weight, even if all of the added 0.08 wt% of Ti is ideally formed into a carbide, Ti is still insufficient. In particular, since the atomic weight of titanium is 47.9, at least 0.003 wt% (=0.23-0.08 x 12/47.9) of free carbon remains, which is considered to be extremely small.

By performing a suitable carbide formation heat treatment (first heat treatment; in the experimental results, 825 ° C or higher and 950 ° C), a significant proportion of 74% of the contained Ti becomes carbonized at an optimum temperature of 900 ° C. So that 0.008 wt% of free carbon remains. If there is about this amount of free carbon, the true temporary deformation can be reduced as follows.

In addition, the coefficient of thermal expansion hardly showed a difference depending on the cutting direction of the test piece. This value is from 0.42 to 0.47 ppm/degree in the range of 18 to 28 °C. This measurement was carried out using a TMA 8310 manufactured by Ulvac Riko, Inc. at a temperature increase rate of 5 ° C / min.

In addition, about 0.03% by weight of carbon is inevitably contained using the dissolution and casting methods generally employed. It is actually difficult to reduce this content to 0.008% by weight. By adding a very small amount of Ti, the amount of carbon which affects temporary deformation can be reduced to 0.008% by weight; however, it is difficult to change the coefficient of thermal expansion and have the same degree of manufacturing cost.

(Specific explanation of the main reasons for temporary deformation)

Figure 1A is a diagram illustrating the stress-strain curve obtained by a three-point bending test. In FIG. 1A, the vertical axis represents the load (kN) of the center concentration, and the horizontal axis represents the maximum strain (ppm). In addition, in FIG. 1A, the circle represents the measurement point when the load is applied; and the measurement point of the triangle when the load is removed. Figure 1B illustrates a schematic representation of a three point bend test. Since the micro strain portion is the result of creep deformation, the portion having a large strain amount is not explained. In Fig. 1A, as an example of a general material, it is explained that when the maximum center load is gradually increased, the residual permanent strain is also increased.

As the test piece, various composition materials listed in Table 1 were made into a size of 30 × 30 × 339 mm. The test piece is supported at a distance of 250 mm from either end. The concentrated load is applied at the point of the central portion, and the output of the strain gauge attached to the central portion of the opposite surface determines the dependent variable. The test temperature is room temperature, and the subsequent temperatures when measuring temporary deformation are roughly the same. The load speed is set to a small extent of 0.5 mm/min so that the effect of the post-rebound effect can be ignored.

First, the maximum load is set to a small extent, and the load is repeatedly added and removed. Then, while gradually increasing the maximum load, the maximum load when the permanent strain of the residual can be detected is 12 kN. The residual permanent strain (a) at this stage was 3 ppm. However, in this test, since the strain gauge is attached to the portion of the test piece where the maximum strain is generated, and the strain is measured at the portion, the average strain amount of the entire test piece will even be a smaller value.

Subsequently, when the maximum load is set to 15 kN, the load is applied, and then the load is removed, the residual permanent strain (b) is 10 ppm. In this case, if the maximum load of 15 kN is applied at the beginning, a permanent strain of 13 ppm should be left.

Figure 2 is a graph illustrating the maximum surface strain of the various constituent materials of Table 1 and the residual strains remaining at that stage at that stage. In Fig. 2, the maximum load determined from the three-point bending test of Fig. 1A and the permanent strain remaining at this stage convert the maximum load to the maximum surface strain; and the permanent strain is used until the strain is generated. The cumulative value of the dependent variable.

Typically, the permanent strain used to display the intensity value is 0.2% (200 ppm). However, in this survey, the intensity values for very few permanent dependent variables are determined. In high-precision instruments, the amount of deformation affecting the performance of the instrument is about 10 ppm for the beginning year, considering the period of use and the warranty period as the service life of the instrument. Therefore, a resolution measurement of 1 ppm smaller than the one-digit number is performed.

From these results, if the cause of the temporary deformation is a phenomenon of creep deformation, the high-strength material (Examples 2 to 5) should have a significantly smaller temporary deformation. In addition, for the three test pieces on the left side of Fig. 2, only the carbon content is different (low carbon material: Example 1; general material: comparative example 1; and high carbon material: comparative example 2), the intensity value As the carbon content increases, it increases. As a result, similarly, assuming that the temporary deformation is caused by creep deformation, the amount of temporary deformation for the high carbon strong material should be reduced.

Figure 3 illustrates the actual measured amount of temporary deformation of various composition materials. In Fig. 3, the amount of temporary deformation per month is explained, and it is assumed that the various nickel-containing iron-based low thermal expansion alloys of Table 1 are linearly deformed for one month. From the statement of the general material (Comparative Example 1) as a result of the standard, the high carbon material (Comparative Example 2) showed a very large amount of temporary deformation. Therefore, a comparison between materials having different carbon contents shows that the amount of temporary deformation increases for high carbon materials. As long as the high carbon material is manufactured in a conventional manner, the alloy composition contains a large amount of carbon, which is unlikely to be an inevitable carbon content. In order to further find the cause of the temporary deformation, an alloy having a very low and extremely high carbon content and a low carbon material are particularly manufactured. When materials having different carbon contents (Example 1 and Comparative Examples 1 and 2) were compared, the amount of temporary deformation was increased for the high carbon material.

In addition, as described below, it has been found that when measuring thermal expansion, the size hypothesis appears in the high carbon material during heating and cooling.

On the other hand, individual high strength materials (Examples 2 through 5) have minimal temporary deformation. The high strength material contains a carbide forming element in an amount of about 3.0% by weight, which is significantly greater than the minimum required amount to form a carbide. Therefore, the strength value should be increased. For the reason that the creep system is temporarily deformed, the reduction of the temporary deformation should be significantly affected; for the reason that the carbon-related γ expansion system is temporarily deformed, the temporary deformation The reduction should also have a significant impact.

Therefore, although it is not possible to specify whether the cause is creep deformation or γ expansion in the comparison of the results of the temporary deformation of the general material and the high-strength material, if the result of the comparison between the materials which only change the carbon content is considered, the temporary deformation is considered. The main reason can be assumed to be γ expansion.

The material to which Nb is added and the material to which a very small amount of Ti is added are also significantly improved as compared with general materials. Even so, since the amount of free carbon is slightly larger than that of the high-strength material, the temporary deformation is slightly larger than that of the high-strength material. For the general materials (Comparative Example 1) and Examples 2 to 7, even if the total content of carbon is about the same, the free carbon content of the latter is lowered. In addition, the temporary deformations in Examples 2 to 7 were extremely suppressed. It is understood from these results that the amount of temporary deformation is closely related to the amount of free carbon, but not to the total content of carbon.

Quartz hardly produces any temporary deformation between the materials used for comparison. In addition, stainless steel (SUS 316, 615 ° C × 2 hours, then furnace cooling) and carbon steel (S45C, 800 ° C × 2 hours, then furnace cooling) have negative values, and thus it can be considered that the internal residual stress is slightly left. Gamma expansion is not considered to occur in any of these materials.

Figure 4 is a schematic illustration of a measurement system used in measuring the amount of temporary deformation. In this measurement system, the test piece 1 has the same dimensions as those previously used in the three-point bending test. Mirrors 4 and 5 are attached to either end of the test piece 1. These mirrors 4 and 5 are provided to reflect laser light from two laser interferometers (end measuring machines) 2 and 3. Based on the change in optical path length, the laser interferometers 2 and 3 read the size of the test piece and use the so-called "Michelson Interferometer" principle.

The expansion and contraction of the test piece depend on the difference in positional change at either end of the test piece measured by the two laser interferometers. The resolution of this measurement system is 0.2 nm. Since the length of the test piece is 339 mm, the conversion shows that a resolution of 0.0006 ppm can be obtained. If there is such a resolution, even if there is a change of about 1 ppm per year, such precision makes the measurement effective.

This measuring system is constructed on a quartz platform 6. The measurement system is fixed in an indoor environment where the temperature is controlled at room temperature (23 ° C) ± 0.01 ° C. In a real implementation, the temperature of the test piece changes even smaller. As a result, the amount of expansion and contraction due to thermal expansion can be ignored.

(method of measuring the amount of free carbon)

5A to 5C are photographs illustrating the metal structure of the high-strength material 8-2 as an example and a graph illustrating the results of the elution extraction analysis. Each surface can be distinguished by smoothing the surface to become a mirror surface and then performing a suitable etching treatment to match the purpose. In the metal structure, the other phases different from the basic phase are clearly dispersed. Figure 5A is a photograph of one of these phases observed by a scanning electron microscope. A phase of approximately 5 μm in size can be confirmed at the photo center. This phase was analyzed by electron probe microanalysis (EPMA) and titanium and carbon were detected.

Next, a method for performing the elution extraction analysis performed herein will be described. First, using 0.5 g of an alloy material as an anode and platinum as an opposite electrode, electrolysis was carried out in an electrolytic solution of 10 v/v% acetamidine acetone and 1 w/v% tetramethylammonium chloride at a voltage of 0.2 V. Then, the resulting residue was subjected to suction filtration, wherein the residue was passed through a polycarbonate type (PC) filter paper (0.2 μm filter paper) to intercept the residue. Fig. 5B is a photograph obtained by observing the product taken on the filter paper in the same manner by a scanning electron microscope. When the product was analyzed by EPMA in the same manner as described above, it was found from the results of Fig. 5C that the product was TiC.

Second, the filter paper and the cut product are turned into ash in a platinum crucible. The obtained product was then charged together with a mixture (solvent) of sodium borate and sodium carbonate, and the resulting mixture was dissolved at 900 °C. This mixture was then filled with 10 ml of hydrochloric acid and several milliliters of perchloric acid. The dissolved solution was diluted to a fixed volume and then subjected to IPC analysis. The ratio of the carbide in the dissolved alloy to the total amount of the alloy is thus determined, and the mass of carbon is calculated from the individual atomic weights of Ti and C. In addition, the amount of free carbon is determined by subtracting the carbon formed into a carbide from the total amount of carbon previously analyzed.

Here, since the carbon in the alloy can also form TiN, analysis of separation is performed, but no TiN is detected in the alloy. Further, although the high-strength materials (9-1 and 9-2, Examples 4 and 5) contain both Ti and Nb, the carbon content of the carbides is determined by the individual content and the atomic weight. This can be determined in the same manner even if the carbide forming elements are Ta, Zr and the like.

The total amount of carbon is determined by the combustion infrared absorption method. This analysis is a method in which a sample is heated to a high temperature in an oxygen stream to oxidize the carbon contained therein to carbon dioxide and the like, and the carbon content is determined by measuring infrared absorption.

(The relationship between the amount of free carbon and temporary deformation)

Fig. 6 is a graph showing the relationship between the amount of free carbon and the amount of temporary deformation of various constituent materials determined by the above-described elution extraction analysis. In this drawing, the composition materials having temporary deformation concentrated near the origin are five constituent materials - low carbon material (Example 1) and various high strength materials (Examples 2 to 5). Other drawings are also related to Table 1 and Figure 3.

Under the low-volume free carbon plot, there is a direct relationship between the amount of temporary deformation and the amount of free carbon.

In addition, a large proportion of the carbon contained in various high-strength materials has been fixed into carbides. For all of these materials, the ratio of the amount of free carbon to the total content of carbon is 0.0031% by weight or less. Some materials have a smaller ratio than the low carbon material (Example 1, C: 0.002% by weight), which are manufactured from special materials such as electrolytic iron, electrolytic nickel or the like to have a very low carbon content. As illustrated in Figure 7, the amount of free carbon in the high strength material 8-1 (Example 2), 8-2 (Example 3), 9-1 (Example 4), 9-2 (Example 5) is 0.0008, respectively. % by weight (= 0.013-0.0122, hereinafter the same), 0.0005 wt% (=0.013-0.0125), 0.0031 wt% (=0.012-0.0089), and 0.0025 wt% (=0.012-0.0095). In addition, similarly, the free carbon content in the material to which a very small amount of Ti was added (Example 6) and the material to which Nb was added (Example 7) were 0.0080% by weight (=0.023-0.015) and 0.0069% by weight (=0.017-0.0101), respectively. .

These materials also have a very small amount of temporary deformation. It is understood that if the amount of free carbon is 0.010% by weight or less, temporary deformation can be suppressed to a lower degree. More desirably, in order to suppress the amount of temporary deformation to 1 ppm or less (calculated on an annual basis), the amount of free carbon is desired to be 0.0050% by weight or less.

Since carbon exists in the form of free carbon in a general material, the unevenness of the amount of temporary deformation also occurs due to the inhomogeneity of the carbon content which is included during the production. Even for relatively good manufacturing lots, there is a 0.4 ppm expansion (calculated on a monthly basis). In the present invention, by forming carbides, temporary deformation can be reliably reduced to less than that of ordinary materials.

Figure 7 is a graph showing the ratio of the fixed carbon content (% by weight) to the total content (% by weight) of carbon, which is calculated using the fixed carbon content (% by weight) determined by the results of the elution extraction analysis of Figure 5C. . From this plot, Ti (Examples 7, 2, 3) is more efficiently bonded to carbon atoms than Nb (Examples 6, 4, 5), so that only a small amount of carbide forming elements are required.

Since excessive carbide forming elements increase the coefficient of thermal expansion, in view of this, Nb is better than Ti. Further, in the comparison between the composition materials in which Nb was similarly added, Examples 4 and 5 in which the intermediate heat treatment (second heat treatment) was carried out at 720 ° C for 6 hours were compared with Example 6 in which the intermediate heat treatment was not performed, resulting in a slightly larger ratio. Carbide. Therefore, in order to make the amount of temporary deformation smaller and to suppress the coefficient of thermal expansion to a low degree, it is desirable to add a minimum required amount of carbide-forming elements, and to perform a suitable heat treatment at the time of carbide formation.

As described above, in the present experiment, in the Super Invar alloy, it is understood that the carbide forming element having the highest carbide forming efficiency is Ti. However, other elements conventionally referred to as carbide forming elements in steel materials, such as Ta, Zr, W, V, Mo, and the like, are also considered to provide the effects of the present experiment.

In addition, although the intermediate heat treatment conditions in this experiment were 720 ° C × 6 hours, these intermediate heat treatment conditions together with the aging treatment conditions were carried out only for the four high strength materials. The original purpose of this intermediate treatment was to harden the material by precipitating the phase of the compound of Ni and the carbide forming element.

(The method of manufacturing the alloy)

In order to reliably reduce the amount of free carbon, a large amount of carbide forming elements can be added similarly to the four high strength materials. However, if such a carbide forming element is excessively retained, the coefficient of thermal expansion increases. Therefore, it is desirable to reduce the amount of free carbon by effectively combining only a small amount of carbide forming elements with free carbon. To achieve this, it is desired to perform melt casting, hot forging, and then perform a predetermined heat treatment (first heat treatment).

Figure 8 is a graph illustrating the relationship between the heat treatment temperature and the amount of free carbon. This drawing was prepared to determine the temperature at which carbides were easily formed in the first heat treatment. Using an alloy with a very small amount of Ti (Example 7), all 6 samples were measured (which had been melt cast by vacuum melting furnace, hot forged at 1000 ° C, and then maintained at a predetermined temperature (first temperature) for 2 hours) The amount of free carbon in the heat treatment) and one sample which has been subjected to solution treatment at 1100 ° C. As the first temperature, the measurement was performed at a temperature of 825 ° C to 950 ° C at intervals of 25 ° C .

From the results of this experiment, it is understood that the first temperature at which the carbide is most easily formed and the amount of free carbon is lowered is 900 °C. For example, the sample heat-treated at 900 ° C has a total content of carbon of 0.023 wt%, wherein the content of the fixed carbon is 0.0148 wt%. In particular, 74% of the total content of carbon is formed as a carbide.

In addition, since the material to which a very small amount of Ti is added has a Ti content of 0.08% by weight and a carbon content of 0.023% by weight, even if all of Ti is ideally bonded to carbon, the fact that 0.0030% by weight of free carbon remains remains should be considered.

It is understood from this experiment that the first heat treatment is performed at a temperature of at least 825 ° C or higher and 950 ° C or lower, and it is more desirable to perform the first heat treatment at a temperature of 875 ° C or higher and 925 ° C or lower. Carbides are easier to form.

(multiple measurement results)

Figure 9 is a graph illustrating the coefficient of thermal expansion of individual Super Invar alloy composition materials used in this investigation. The thermal expansion coefficient of the Super Invar alloy composition material is obtained simultaneously with the result of the dimensional change measurement by means of a thermal expansion measuring device (Laser Thermal Expansion Meter LIX, by Ulvac- for checking the relationship between temperature and dislocation). Riko, Inc.)). The test piece has a size of 6 mm in diameter and 12 mm in length. The heating and cooling rates were set to 1 ° C / min. Since there is a slight difference between the temperature of the actual test piece and the temperature of the thermometer arranged near the test piece, heating and cooling are performed in such a slow manner. The measurement range is between 30 ° C and 50 ° C.

As a result, as the amount of solid solution carbon increases, the coefficient of thermal expansion also increases; and as the content of carbide forming elements increases, the coefficient of thermal expansion also increases.

In addition, no difference was found in the coefficient of thermal expansion between the DA material and the STA material. After the solution treatment, the STA material having a uniform metal structure was produced by rapid cooling. These STA materials were fabricated to minimize the separation of Ni in the metal structure as a Super Invar alloy. This is because if a portion having a low Ni content or a high Ni content is present in the metal structure, these portions are excluded from the composition which originally has the lowest coefficient of thermal expansion, so that the coefficient of thermal expansion of the entire material is increased. The effect of individual elements on the coefficient of thermal expansion depends on the state of existence of these elements. Although this is the same even for other carbide forming elements such as Nb, even if Ti is added, it is desired that the added Ti binds to an inevitable carbon atom, and thus exists in the metal structure in the form of TiC. . This is because the strength is increased, and since the TiC itself has a small coefficient of thermal expansion, the agglomeration with the base phase is small, which means that the effect of increasing the coefficient of thermal expansion of the entire material is small.

However, if the original lattice point of the Super Invar alloy is substituted for the Ti atoms not bonded to the carbon atoms, the Invar effect is lowered. In any event, since the carbon and carbide forming elements are formed in the solid solution, the intensity of the spontaneous magnetization is lowered. Ti atoms that do not contribute to the bonding of carbon atoms and the like become superfluous atoms for a Super Invar alloy to have low thermal expansion.

Therefore, in order to achieve a low coefficient of thermal expansion, the excess element may be subjected to a suitable aging heat treatment to increase the strength, so that a precipitate phase such as a γ' phase and a γ" phase is produced. This is because the creep resistance can be improved and simultaneously cut. Sex can also be improved due to reduced adhesiveness.

In Super Invar alloys, carbon is inevitable in the form of free carbon (solid solution carbon or voided carbon) unless special elements are added and appropriate treatment is applied. These carbon atoms promote temporary deformation and also increase the coefficient of thermal expansion.

Regarding the increase in the coefficient of thermal expansion of the carbide forming element, in the present investigation, when 0.24% by weight of Nb was added, the coefficient was increased by 0.25 ppm/° C., and when 3.9 % by weight of Nb was added, the coefficient was increased by 3.0 ppm/ °C. For 36% Ni Invar, the coefficient of thermal expansion is often 1 ppm/degree. Because this is too high, I originally chose Super Invars. In order to maintain a low coefficient of thermal expansion (less than 1 ppm/degree, which is the maximum characteristic of Super Invars), the above value of 0.50% by weight or less depends on the approximate curve obtained during the course of the survey, which is in the formula (2). It is stated as a condition that the coefficient of thermal expansion is less than 1 ppm/degree.

y=0.76x+0.63 (2)

Here, y indicates the coefficient of thermal expansion (ppm/degree), and x indicates the Nb content (% by weight).

For Ti, the coefficient of thermal expansion may depend on the approximate curve illustrated in equation (3). Here, x is the same value as for Nb.

y=0.71x+0.60 (3)

Although Ti has a slightly larger ratio and the coefficient of thermal expansion increases, the value is roughly the same.

Fig. 10 is a graph showing the results of measurement of temperature and dislocation by the above-described thermal expansion meter when a high carbon material (Comparative Example 2, C: 0.118%) was heated and cooled at a rate of 1 ° C / minute.

In the measurement results of the first cycle, one characteristic is that the slope of the thermal expansion curve of the test piece is reduced at about 150 °C. This is considered to be because the diffusion of carbon atoms becomes active at this temperature. If the temperature is heated to 210 ° C (205 ° C in the third and fourth cycles) and then cooled to room temperature, a significantly different trajectory is followed during heating and during cooling. When compared at the same temperature close to room temperature, the test piece which had been heated and cooled was contracted by its original size by 25 ppm (hereinafter referred to as "amount due to the air drying effect"). The test piece was heat treated at 98 ° C for 48 hours before this measurement. Subsequently, this measurement was performed again at room temperature after 570 hours have elapsed. As a result, between the carbon atoms formed in the solid solution, certain proportions of carbon atoms can be considered to have moved to a stable position at room temperature (hereinafter referred to as "room temperature stable position". Similar to the fcc lattice The tetrahedral void address). If heated to 205 ° C, the spontaneous magnetization almost completely disappears, so that at this temperature, the carbon atoms can be considered to be moved to another position (hereinafter referred to as "high temperature side stable position". Similar to the eight sides in the fcc lattice Body gap address). In addition, it was determined that during the cooling period, the diffusion of carbon could not be maintained, whereby the material returned to room temperature, and most of the high temperature side stable position (the carbon atom was stabilized at 205 ° C instead of room temperature) remained intact. status.

Therefore, it can be assumed that due to the heating and cooling of the first cycle, the volume (expanded state) of the test piece when a certain proportion of carbon atoms are moved to the room temperature stable position is changed to the carbon atom is moved to room temperature. The volume (contracted state) in the state of the stable position, and the shrinkage of 25 ppm occurs.

The temperature of 98 ° C has apparently been determined to increase the void diffusion rate of carbon atoms and to complete the treatment at a time practical for industrial manufacturing processes. It may be considered that at this temperature, since the reduction in spontaneous magnetization is still small, most of the carbon atoms will be in the same position, and these positions are stable positions at room temperature. For this point, as described below, in this investigation, carbon diffuses from a room temperature stable position to a high temperature side stable position, which is apparently started at a temperature of 80 ° C or higher. The temperature of 80 ° C is therefore considered to be more suitable than the artificial air drying temperature of 98 ° C described above.

Although the best treatment for temporary deformation is to have a component at the temperature of use for decades and then mount the component in the product, this is not practical. However, in the present investigation, there were also materials in which the third cycle was measured after 1349 hours at room temperature and no heat treatment at 98 °C between the second and third cycles. In this case, the amount due to the air drying effect was 19 ppm. In other words, during this time, a temporary deformation of 19 ppm expansion occurred. Since 1349 hours is not a reasonable time for industrial processing, the temperature range described below is preferred for stabilization. When the second cycle measurement is performed immediately after the end of the first cycle, the size of the test piece does not change even after heating and cooling. This can be assumed to be because at the first cycle heating temperature (210 ° C), all carbon atoms have diffused to the high temperature side stable position.

In the second cycle, the reason why the curves do not match exactly during heating and cooling is that the temperature change of the test piece is slower than the temperature change of the controlled thermometer. As a result, the dimensional difference is large in a range in which the coefficient of thermal expansion is large (high temperature side). In order to confirm this, in the plotting of the measurement results for the undescribed low-carbon material (C: 0.002% by weight), the two curves are matched, and when the heating curve shows a +4 ° C offset and cooling When the curve shows a -4 °C offset. In the measurement shown here, the stabilization treatment was then carried out at 98 ° C for 48 hours, and then the material was allowed to stand at room temperature for 816 hours until the measurement and the third cycle measurement were carried out.

Similar to the measurement result of the first cycle, a large amount is again displayed in the third cycle due to the air drying effect. It is 30 ppm in the third cycle compared to 25 ppm in the first cycle. This is believed to be due to the long standing time at room temperature.

The stabilization temperature must be above room temperature and must be below the Curie temperature. However, since the true Curie temperature should be substantially at a high temperature stable position, a temperature of 150 ° C or lower (which is where the heating and cooling curves intersect) is practical. In this measurement, since it takes 2 hours to heat from room temperature to 150 ° C, it can be said that there is an artificial air drying effect even if the treatment at 150 ° C is used for 2 hours or less.

In addition, although it can be understood from the heating curve that the heating curve and the cooling curve (the straight portion of the temperature of 100 ° C or lower) are no longer parallel, the temperature is 80 ° C. At temperatures higher than this temperature, these curves are no longer parallel. From this result, it can be estimated that the carbon atoms present in the room temperature stable position start to diffuse to the high temperature stable position at a temperature of 80 ° C or higher. Therefore, in order to keep most of the carbon atoms in a stable position at room temperature, it is more desirable to have a temperature above room temperature to 80 ° C or below.

The fourth cycle follows the same trajectory as the second cycle. Since the measurement is performed immediately after the third cycle and the stabilization process is not performed, this is the planned result.

From the above, while the temperature is gradually lowered from 205 ° C to 210 ° C, the components which have completed the second to fourth cycles have been subjected to the same treatment. However, the alloy being processed should not be assembled in the product. This is because for high-carbon materials, temporary deformation occurs in the future, which is only 25 to 30 ppm larger than a component that has been stabilized.

In addition, the above description: The high carbon material is calculated on the basis of the year, and has a fact that the temporary expansion deformation is 18 ppm. However, this material is subjected to such temporary deformation measurements after the material has been subjected to stabilization. Therefore, this does not conflict with the fact that even if the material is left at room temperature for only 1359 hours (about 2 months), the same amount is produced due to the air drying effect.

Although the dimensional change of the low carbon material test piece is measured in the same manner as for the high carbon material, regardless of whether the test piece is allowed to stand at room temperature before the measurement, the sample length returns to the original size even after heating and cooling. In particular, the shrinkage seen for high carbon materials cannot be confirmed. Therefore, as described above, the reason why the slope becomes small at 80 ° C in the heating curve of the high carbon material and the size is shrunk at the point where the cooling proceeds to room temperature can be assumed to be due to the diffusion of carbon atoms.

While the invention has been described with respect to the specific embodiments illustrated, the invention The scope of the following claims is intended to cover the broadest scope and

1. . . Test piece

2. . . Laser interferometer

3. . . Laser interferometer

4. . . mirror

5. . . mirror

6‧‧‧Quartz platform

7‧‧‧ lenses

8‧‧‧ frame components

9‧‧‧ Appearance

Figure 1A is a graph illustrating the stress-strain curve obtained as a result of a three-point bending test.

Figure 1B illustrates a schematic representation of the three point bend test of Figure 1A.

Figure 2 is a graph illustrating the maximum surface stress of various constituent materials and the permanent strain residuals at that time.

Figure 3 illustrates the actual measured amount of temporary deformation of various composition materials.

Figure 4 is a schematic illustration of a measurement system used in the measurement of the amount of temporary deformation.

5A, 5B and 5C are photographs illustrating the metal structure of the high-strength material 8-2 and a graph illustrating the results of the elution extraction analysis.

Fig. 6 is a graph showing the relationship between the amount of free carbon of various constituent materials determined by the results of the elution extraction analysis and the amount of temporary deformation.

Figure 7 is a graph illustrating the ratio of the fixed carbon content (% by weight) to the total content (% by weight) of carbon, which is determined using the fixed carbon content (% by weight) determined by the results of the elution extraction analysis of Figure 5C. ) and calculated.

Figure 8 is a graph illustrating the relationship between the heat treatment temperature and the amount of free carbon.

Figure 9 is a graph showing the coefficient of thermal expansion of individual Super Invar alloy composition materials used in the present invention.

Fig. 10 is a graph showing the results of measuring the displacement of the temperature and the high-strength material (C: 0.118%) by the thermal dilatometer (change in the size of the test piece).

Figure 11 is a cross-sectional view of a lens barrel using the frame member 8 of the alloy of the present invention.

Claims (22)

An alloy comprising an essential component of a Super Invar alloy, iron, nickel, and cobalt, wherein a ratio of carbon to alloy other than carbon contained in the carbide is 0.010% by weight or less in the alloy. The alloy of claim 1 further comprising a carbide forming element, wherein the carbide containing at least a portion of the carbide forming element is dispersed in the base phase. An alloy as claimed in claim 2, wherein the total carbon content of the alloy is 0.010% by weight or more. For example, in the alloy of claim 3, wherein the content of the carbide forming element is higher than the total carbon content in terms of atomic percentage. The alloy of any one of claims 2 to 4, wherein the content of the carbide-forming element in the alloy is 0.05% by weight or more and 0.50% by weight or less. The alloy of any one of claims 2 to 4, wherein the amount of the carbide-forming element that has not been carbonized is 0.50% by weight or less. An alloy according to any one of claims 2 to 4, wherein a compound phase of nickel and a carbide forming element is formed. The alloy of any one of claims 2 to 4, wherein the carbide forming element is titanium or tantalum. A lens holding member comprising the first patent application scope An alloy of any of the four items. An optical device comprising the lens holding member of claim 9 of the patent application. A method of producing an alloy as claimed in claim 1, the method comprising: adding a carbide forming element to the base component and melting the cast mixture; hot forging at a predetermined temperature; and by lowering the predetermined temperature At the first temperature, the first heat treatment is performed, and the carbide formed by the carbon contained in the alloy and the carbide forming element in the base phase is precipitated in the base phase. A method of producing an alloy according to claim 11, wherein the first temperature is 825 ° C or higher and 950 ° C or lower. A method of producing an alloy according to claim 11 or 12, wherein the content of the carbide-forming element added is 0.05% by weight or more and 0.50% by weight or less. The method of producing an alloy according to claim 11 or 12, further comprising forming a compound phase of nickel and a carbide forming element by performing a second heat treatment at a second temperature lower than the first temperature. A method of producing an alloy according to claim 11 or 12, further comprising the step of performing a third heat treatment at a third temperature lower than a Curie temperature of the alloy. A method of producing an alloy according to claim 15 wherein the third temperature is 80 ° C or lower. An alloy according to claim 1, wherein the alloy comprises from 30.0 to 38.0% by weight of nickel, from 3.0 to 7.0% by weight of cobalt, from 0.05 to 0.5% by weight of titanium or ruthenium, more than 0.1% by weight of carbon and from 62.0 to 68.0 Composition by weight of iron. A method of producing an alloy, wherein the alloy comprises an essential component of a Super Invar alloy - iron, nickel, and cobalt, the method comprising: adding a carbide forming element to the base component and melting the resulting mixture; hot forging at a predetermined temperature; And performing the first heat treatment at a temperature of 80 ° C or lower. The method for producing an alloy according to claim 18, further comprising: performing a second heat treatment at a second temperature lower than the predetermined temperature before the first heat treatment, and depositing is contained in the alloy The carbon and the carbide formed in the base phase form a carbide formed by the element. A method of producing an alloy according to claim 19, wherein the second temperature is 825 ° C or higher and 950 ° C or lower. A method of producing an alloy according to claim 18 or 19, wherein the content of the carbide-forming element added is 0.05% by weight or more and 0.50% by weight or less. The method for producing an alloy according to claim 18 or 19, further comprising forming nickel and carbonization by performing a third heat treatment at a third temperature lower than the first temperature before performing the first heat treatment. The compound forms the compound phase of the element.