JP3769606B2 - Method for producing non-magnetic high-strength material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention of this application relates to a method for producing a nonmagnetic high-strength material. More specifically, the invention of this application performs physical property experiments under pressure required under non-magnetic conditions and material synthesis under pressure, which has good processability, can be stably supplied, and exhibits sufficient mechanical properties. The present invention relates to a nonmagnetic high-strength material manufacturing method for manufacturing nonmagnetic high-strength materials that can be used not only as high-pressure materials, but also as machine parts such as nonmagnetic screws and tools such as nonmagnetic pliers.
[0002]
[Prior art and its problems]
NiCrAl alloy developed by Almov et al. Of the former Soviet Union in 1972 as a high-strength material, also known as Russian Alloy (described in M. Eremets, High Pressure Experimental Methods, Oxford University Press, 1996) is a high-pressure cell material with low magnetic susceptibility. Are known.
[0003]
However, this NiCrAl alloy has a composition similar to the composition described in the above document, and it is not easy to reproduce the same performance even in the current Russia, and it is difficult to obtain.
[0004]
One of the causes is poor workability of NiCrAl alloy.
[0005]
Therefore, the invention of this application has been made in view of the circumstances as described above, has good workability, can be stably supplied, and exhibits sufficient mechanical properties, under the pressure required for nonmagnetic conditions. Non-magnetic high-strength materials that produce non-magnetic high-strength materials that can also be used as mechanical parts such as non-magnetic screws and tools such as non-magnetic pliers, as well as high-pressure materials used in physical property experiments and under pressure synthesis Providing a method for manufacturing a material is a problem to be solved.
[0006]
[Means for Solving the Problems]
The inventors of this application added 20 to 150 ppm by weight of boron (B) to the aforementioned NiCrAl alloy to improve the melting point drop and the grain boundary strength of the NiCrAl alloy. As a result, the technical knowledge that the workability of the NiCrAl alloy was remarkably improved by the addition of B within the above specific range, and stable processing was obtained. In addition, the technical knowledge that the NiCrAl alloy to which B is added in the above specific range also realizes mechanical properties not inferior to the mechanical properties described in the above-mentioned document was obtained.
[0007]
The invention of this application is based on the above technical knowledge, as a method for producing a nonmagnetic high-strength material, by weight ratio, nickel (Ni) 55-58%, chromium (Cr) 38-42%, and Manufactures non-magnetic high-strength material in which boron (B) is added by 20 to 150 ppm by weight to NiCrAl alloy containing 2 to 4% aluminum (Al) through a series of steps of casting-forging-aging treatment In doing so, it is characterized in that an ingot produced by casting is reheated to 1200 ° C. during forging.
[0008]
The nonmagnetic high-strength material manufactured by the manufacturing method of the invention of this application is, as will be described later, a NiCo-based multiphase alloy (MP35N (IRWalker, Rev. Sci. Instrum), which has been recently developed as a material comparable to the Russian Alloy. 70 (1999) 3402), the magnetic susceptibility is about an order of magnitude smaller and the yield stress is larger, and because it does not contain cobalt (Co), it ensures stable resources and costs. It has the advantage that it is advantageous also in terms of surface.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The non-magnetic high-strength material produced by the production method of the invention of this application is 55 to 58% nickel (Ni), 38 to 42% chromium (Cr), and 2 to 2 aluminum (Al) by weight ratio. Boron (B) is added to the NiCrAl alloy containing 4% in a weight ratio of 20 to 150 ppm.
[0010]
NiCrAl alloy has a high melting point, which leads to poor workability. The addition of B lowers the melting point of the NiCrAl alloy and improves the workability. The amount of B added is limited to a range of 20 to 150 ppm by weight. This is because if it is less than 20 ppm, it is not very effective in improving workability, and if it exceeds 150 ppm, the physical properties of non-magnetic high-strength materials tend to be unstable, such as the formation of compounds with other metal elements. Based on.
[0011]
The above non-magnetic high-strength material is manufactured through a series of processes of casting-forging-aging treatment. Ni, Cr, and Al raw materials are blended within the weight ratio, and B is added to the weight ratio and cast. In general, various phases precipitate and disperse in the inside of the ingot gradually cooled in the mold, so that the hardness of the entire ingot tends to increase. In this case, it is essential to perform a homogenization treatment before forging. The temperature of the homogenization treatment is exemplified by about 1200 ° C.
[0012]
Forging is performed in order to once break the structure formed at the time of casting and extract the original characteristics of the material. Various methods such as rolling that are usually performed can be employed for forging. During forging, the ingot is reheated to about 1200 ° C. NiCrAl alloy can be made into a face-centered cubic single phase, and workability is improved. Also, the addition of B can sufficiently lower the working temperature during forging, and the workability of the NiCrAl alloy is greatly improved.
[0013]
An aging treatment is performed after forging. Prior to this, a pre-strain treatment can be performed by deforming to about 10% by groove rolling at room temperature or the like. Pre-strain treatment allows the introduction of lattice defects such as dislocations and atomic vacancies in the alloy, and the introduced lattice defects become the core of precipitates generated during the aging treatment, resulting in fine dispersion of the precipitates. As a result, the strength tends to increase.
[0014]
The treatment temperature in the aging treatment is effectively 500 ° C. or higher and lower than 800 ° C. When the aging temperature is less than 500 ° C., precipitates are not sufficiently precipitated, and the hardness varies, and when the temperature is 800 ° C. or more, the hardness sharply decreases. Preferably, the temperature is 700 ° C. or higher and lower than 800 ° C., and the aging treatment within this temperature range sufficiently increases the tensile strength. When the temperature is returned to room temperature after aging treatment, either furnace cooling or rapid cooling after exposure to the atmosphere may be used. There is no tendency for the cooling process to greatly affect the properties.
[0015]
Hereinafter, an Example is shown and the manufacturing method of the nonmagnetic high intensity | strength material of invention of this application is demonstrated in more detail.
[0016]
【Example】
A pressure cell was produced as an example of a nonmagnetic high-strength material according to the following procedure.
[1] Casting of B-added NiCrAl alloy NiCrAl alloy with Ni of 56.5%, Cr of 40%, and Al of 3.5% was added, and B was added at 50 ppm by weight. For the addition of B, a Ni-15.5 wt% B alloy prepared in advance was used. The raw material was melted using a high-frequency melting furnace, and an alumina crucible was used as the container.
[0017]
However, since Al has a lower melting point than other metals and alloys, melting was performed as follows.
[0018]
First, Ni, Cr, and B were dissolved in a vacuum, and then Al was added, and then the atmosphere was changed to argon (Ar) gas (100 to 300 Torr) in order to suppress the evaporation of Al and dissolved again. The liquid alloy thus mixed was cast into a mold (about 80 mm × 80 mm × 200 mm).
[2] Forging of cast ingot As described above, various phases precipitate and disperse in the ingot that is gradually cooled in the mold during the cooling process, so that the hardness of the entire ingot is high. In particular, it becomes impossible to cut the nest formed by hot drawing (heat shrinkage during cooling) at the top of the ingot, that is, the injection port of the liquid alloy.
[0019]
For this reason, the cast ingot was kept at 1200 ° C. for 5 hours, homogenized, and water-quenched, and then the nest portion was cut off.
[0020]
Then, after heating the prismatic ingot to 1200 ° C., initial forging was performed using a 300-ton press. Forging was performed while rotating the ingot by 90 °, and finally it was formed into a prismatic shape of 40 mm × 40 mm. In this forging process, the temperature of the ingot was drastically lowered via the press head of the press device, so that it was reheated to 1200 ° C. every time it was pressed. In addition, the reduction ratio in one press was about 5%.
[0021]
The forged product was further reduced to 40 mm square, 38 mm square, and 36 mm square, and finally rolled to 10 to 20 mm square in order to make it closer to the actual size and use it as a bar. During this rolling, the rolled product was reheated to 1200 ° C. each time it was rolled, as in the press working.
[0022]
The bar thus obtained was heated to 1200 ° C. and then quenched with water. The metal structure of the NiCrAl alloy has a particle size of about 10 μm. The 20 mm square bar had a particle size of 10 μm and a rolling reduction of 93.7%.
[0023]
The obtained bar had an elongation of 40% or more at room temperature, and could be extended to 140% or more.
[3] Pre-strain treatment and / or machining As described above, lattice defects such as dislocations and atomic vacancies introduced into the alloy become the core of precipitates generated during the aging treatment, and as a result, the precipitates are fine. Disperses and increases strength.
[0024]
Therefore, some bars were grooved at room temperature, pre-strained, and deformed to 10%. This was followed by machining to form a rod of a predetermined size for a pressure cell that was actually used.
[0025]
The other bars were machined without pre-straining and formed into rods of a predetermined size.
[4] Aging treatment The molded rod was vacuum sealed in a quartz tube and subjected to aging treatment.
[0026]
FIG. 1 is a graph showing the temperature dependency and time dependency of the hardness (Rockwell hardness C scale (HRC)) during aging treatment of a test piece cut out from a rod.
[0027]
During the aging treatment, the test piece was vacuum-sealed in a quartz tube, held at each aging temperature shown in FIG. 1 for 90 minutes or 120 minutes, and then cooled or rapidly cooled to room temperature. Hardness was measured with a Rockwell hardness tester, and the measurements were taken at three institutions to ensure fairness.
[0028]
As can be seen from FIG. 1, hardening occurs rapidly when the aging temperature is around 500 ° C., and the hardness becomes maximum at 550 ° C. On the other hand, when the aging temperature is 800 ° C. or higher, the hardness rapidly decreases again. Moreover, if it is less than 500 degreeC, dispersion | variation will arise in hardness. From this, it is considered that an aging temperature of 500 ° C. or higher and lower than 800 ° C. is appropriate for obtaining stable performance as a nonmagnetic high-strength material.
[0029]
FIG. 2 is a graph showing the results of a tensile test of the test piece after aging treatment.
[0030]
As can be seen from FIG. 2, when the aging temperature is 700 ° C. or higher, 0.2% yield stress is 2 GPa and rupture stress is 2.3 GPa regardless of pre-strained or unstrained material. It shows almost stable characteristics of about% or more.
[0031]
It is empirically known that, for a piston = cylinder type pressure cell used for physical property experiments, the ideal maximum generated pressure is generally about twice the yield stress. Of course, the value is greatly influenced by the design and processing technology of the cylinder, but from the viewpoint of material properties, the above data suggests that the pressure cell can achieve a maximum generated pressure of almost 4 GPa. .
[0032]
FIG. 3 is a graph comparing the results of a tensile test between a nonmagnetic high-strength material manufactured by the manufacturing method of the invention of this application and the aforementioned NiCo-based multiphase alloy (MP35N).
[0033]
As can be seen from FIG. 3, the mechanical properties of MP35N subjected to the optimum aging treatment are approximately 5% compared to the nonmagnetic high-strength material manufactured by the manufacturing method of the invention of this application. It is so low. Moreover, MP35N rapidly undergoes plastic deformation after the yield point. Whether the cause is due to the non-uniformity of the material itself is not certain at this stage, but as can be understood from the result shown in FIG. 3, the non-magnetic high-strength material manufactured by the manufacturing method of the invention of this application Has the characteristics that it has mechanical properties that are superior to those of the above-described Russian Alloy, that is, NiCo-based multiphase alloy (MP35N) that is considered to be comparable to NiCrAl alloy, and is stable.
[0034]
FIG. 4 is a graph comparing the temperature dependence of the magnetic susceptibility between the nonmagnetic high-strength material manufactured by the manufacturing method of the invention of this application and the NiCo-based multiphase alloy (MP35N).
[0035]
The magnetic susceptibility was measured with a SQUID magnetometer. Regarding the temperature dependence of the magnetic susceptibility of MP35N, the above-mentioned literature values are cited.
[0036]
As can be seen from FIG. 4, the non-magnetic high-strength material manufactured by the manufacturing method of the invention of this application shows a magnetic susceptibility that is an order of magnitude smaller at low temperatures than MP35N, and is excellent in non-magnetic conditions. ing.
[0037]
FIG. 4 also shows the temperature dependence of the magnetic susceptibility of a test piece that has not been subjected to aging treatment. Although the magnetic susceptibility is superior at a lower temperature than the test piece that has been subjected to aging treatment, The mechanical properties are far from those of specimens subjected to aging treatment.
[0038]
When actually manufacturing a non-magnetic pressure cell, the rod after aging treatment having the above characteristics is cold-fitted into an outer cylinder made of CuBe alloy, for example, as an inner cylinder, and manufactured into a two-layer cylinder. be able to. Further, final processing such as reamer finishing and screw adjustment can be performed to obtain a product.
[0039]
Of course, the invention of this application is not limited by the above embodiments and examples. Needless to say, various aspects such as operating conditions are possible.
[0040]
【The invention's effect】
As described above in detail, according to the invention of this application, workability is good, stable supply is possible, and sufficient mechanical properties are exhibited, physical properties experiments under pressure required under non-magnetic conditions and material synthesis under pressure Nonmagnetic high-strength materials that can be used not only as high-pressure materials, but also as machine parts such as nonmagnetic screws and tools such as nonmagnetic pliers are provided.
[Brief description of the drawings]
FIG. 1 is a graph showing temperature dependency and time dependency of hardness (Rockwell hardness C scale (HRC)) at the time of aging treatment for a test piece cut out from a rod manufactured in an example.
FIG. 2 is a graph showing the results of a tensile test of a test piece after aging treatment.
FIG. 3 is a graph comparing the results of a tensile test between a nonmagnetic high-strength material manufactured by the manufacturing method of the invention of this application and a NiCo-based multiphase alloy (MP35N).
FIG. 4 is a graph comparing the temperature dependence of magnetic susceptibility between a nonmagnetic high-strength material manufactured by the manufacturing method of the invention of this application and a NiCo-based multiphase alloy (MP35N).

Claims (1)

In a NiCrAl alloy containing 55 to 58% nickel (Ni), 38 to 42% chromium (Cr), and 2 to 4% aluminum (Al) by weight, boron (B) is 20 by weight. A nonmagnetic high-strength material added with ~ 150ppm is manufactured through a series of steps of casting-forging-aging treatment, and the ingot produced by casting is reheated to 1200 ° C. during forging. Manufacturing method of high strength material.

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