JPS6140029B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to age hardenable alloys, and particularly to age hardenable alloys suitable for use as precision wear-resistant parts, tool steels, and the like. In general, quench-hardened steel, which is hardened by quenching, is known as a steel material that is hard and has excellent wear resistance and is used in various precision parts. Since this quench-hardened steel undergoes significant deformation during quenching, a member that has been rough-machined in advance into the shape of a part is quench-hardened, and then finished to predetermined dimensions. Of course, after quenching and hardening, due to its high hardness, normal cutting processing cannot be performed, and it is necessary to use extremely slow processing such as polishing, so finishing processing takes a lot of time. It has the following drawback. On the other hand, as a solution to the drawbacks of the conventional quench-hardened steel, a steel with less deformation during hardening treatment is proposed.
Age hardenable alloys have already been proposed. This age hardenable alloy has low hardness in the liquefied state, but becomes highly hard when subjected to aging treatment. This deformation during age hardening is significantly smaller than the deformation accompanying quenching of hardened steel. Therefore, when manufacturing wear-resistant parts that require high hardness, if this age-hardenable alloy is used, finishing processing can be performed by cutting etc. in a soft and easy-to-process state after liquefaction treatment. I can do it. If the steel is then subjected to age hardening treatment, there is an advantage that processing costs can be significantly reduced compared to when conventional quench-hardened steel is used. However, conventional age hardenable alloys undergo considerable deformation during hardening. For example, maraging steel containing 18% by weight of nickel is known to have minimal age hardening deformation, but even in this maraging steel, shrinkage deformation of 0.06 to 0.1% occurs during age hardening. Therefore, when conventional age hardenable alloys are used as precision wear-resistant parts, the machining accuracy of the part is limited to within the deformation rate of the age hardenable alloy, and high machining accuracy is required. There has been a problem in that it cannot be used in required parts, such as precision gears or various pressure valves, because it is difficult to adjust dimensional deformation after aging treatment. Particularly when the parts are large, conventional age hardenable alloys are currently hardly used for parts other than parts that do not require much dimensional accuracy. The present invention was made in order to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide an age-hardenable alloy with extremely low age-hardening deformation. The present invention is made by weight of 11-16% nickel, 2-4.5% manganese, 0.5-7.5% panadium, and 5-5% cobalt.
12% carbon, 0.2% or less carbon, 8% molybdenum or less, the balance being substantially iron, and relates to an age hardenable alloy mainly having a martensitic structure. If the amount of retained austenite in the above alloy increases, age hardenability deteriorates, so the amount of retained austenite is preferably 10% or less. In addition, the weight percent of molybdenum contained in the age hardenable alloy is {6-0.65V (%) Mo (%) 8-
0.65V (%)} The aging hardness, aging strength, or ductility is significantly improved by adding in proportion to the panadium content so as to satisfy the following relational expression. The present inventors conducted various experiments in order to obtain an age-hardenable alloy with less deformation due to aging, and found that an alloy with the above-mentioned composition among iron-nickel-manganese-panadium-cobalt-molybdenum alloys exhibits remarkable deformation with age. It was discovered that it is small and yet has high strength. It has been known for a long time that iron-nickel-manganese alloys have age hardening properties. However, as age hardening progresses, this alloy becomes significantly more brittle, so although it can achieve high hardness, it cannot be used as a material for various parts due to lack of strength due to brittleness. The present inventor has found that by adding vanadium and molybdenum depending on the application to this iron-nickel-manganese alloy system, not only the toughness is significantly improved and a high-strength member is obtained, but also the deformation during aging is extremely small. I found it. This alloy was published in Japanese Patent Application Publication No. 53-
It is known from No. 149809. This is Nickel 13-15.5
wt%, manganese 2.6-3.5 wt%, vanadium 8
It is an iron alloy containing ~12% by weight and 0.5~3.5% by weight of molybdenum, and the sum of the contents of vanadium and molybdenum is 14.5% by weight or less. This alloy has high strength and high ductility in the high vanadium-low molybdenum composition range. However, due to the high vanadium content of this alloy, oxidation is significant, so a special melting method such as vacuum melting must be used. The vacuum melting method requires a vacuum suction device and is less workable than the atmospheric melting method, and has the disadvantage that the amount of dissolved material is smaller than the atmospheric melting method. On the other hand, this alloy system has a low vanadium content.
It was found that atmospheric dissolution is possible if the concentration is 7.5% or less. In addition, the present inventors set the vanadium content to be dissolvable in the atmosphere, and have high strength, high ductility, and high aging hardness.
Moreover, in order to obtain an age hardenable alloy with little deformation, as a result of various experiments, it was discovered that by incorporating cobalt into this alloy system, the age deformation is significantly reduced, and it also has high strength and high ductility. The reasons for limiting the composition of each element will be explained below. Carbon is mixed in as an impurity from the alloy raw material, and it is preferable to have less carbon, but even if it is contained, it is 0.2% by weight or less. If it exceeds 0.2%, the hardness of the solution treatment will increase and the machinability during solution treatment will deteriorate, so the content should be 0.1% by weight or less. Silicon added as a deoxidizing agent is also mixed in as an impurity, but even if silicon is included, if it exceeds 1% by weight, it will impair the toughness of the alloy, so it should be kept at 1% by weight or less. Nickel is necessary to obtain a martensitic structure through solution treatment and to impart age hardening properties by solid solution with manganese; less than 11% by weight is ineffective, and more than 16% by weight Since it produces an austenite structure and impairs age hardenability, the content should be in the range of 11 to 16% by weight.
Manganese is necessary to provide age hardenability with little deformation by solid solution with nickel, and if it is less than 2% by weight it is ineffective, and if it exceeds 4.5% by weight it will impair the toughness of the alloy, so it is necessary to It should be in the range of ~4.5% by weight. Vanadium is necessary to promote age hardenability and increase strength of iron-nickel-manganese alloys and to prevent age-hardening deformation.
If it is less than 0.5% by weight, the aging strength is low and there is no effect, and if it exceeds 7.5% by weight, it cannot be dissolved in the atmosphere, so it should be in the range of 0.5 to 7.5% by weight. However, in order to obtain high strength after aging, it is desirable that the vanadium content be 2% by weight or more, and if it is 6% by weight or more, shrinkage deformation during aging tends to be accelerated. Further, when considering ease of melting the alloy, strength after aging, or deformation due to aging, a range of 2 to 6% by weight is preferable. Molybdenum contributes to age hardening by precipitating intermetallic compounds through aging treatment, and further increases aging strength through a combined action with vanadium. Furthermore, if molybdenum exceeds 8% by weight, a ferrite structure will be formed and age hardenability will be impaired, so the content should be 8% by weight or less. In particular, since molybdenum depends on the vanadium content, it is preferable that the molybdenum content satisfies the following formula. 6-0.65V (%) Mo (%) 8-0.65V
(%) According to the above relational expression, high aging hardness and strength can be obtained by containing vanadium and molybdenum. That is, in order to obtain high strength with small deformation, it is necessary to reduce the molybdenum content when a large amount of vanadium is contained, and it is necessary to reduce the molybdenum content when the vanadium content is low. Cobalt promotes age hardening of iron-nickel-manganese aged alloy systems, and is necessary to increase strength and prevent deformation, especially when the vanadium content is low. Great effect. Cobalt has no effect if it is less than 5% by weight, and if it exceeds 12% by weight, it impairs ductility and tends to form a ferrite structure during solution treatment, so 12% by weight is a high composition range.
Should be: When considering aging strength,
8-11% by weight is preferred. Solution treatment at 900~1000℃, aging treatment at 400~
500°C is preferred. Hereinafter, the present invention will be explained in detail using experimental results. Table 1 shows the chemical composition (% by weight) of the test materials used in the experiment. Trial numbers A to X are age hardenable alloys having compositions according to the present invention, and are
The basic composition is 15.0% by weight, 3.0% by weight of manganese, and 9.0% by weight of cobalt. Trial number Y is a known maraging steel. Each alloy was melted and forged in the atmosphere.

【table】

[Table] Figure 1 shows the relationship between the deformation rate due to aging and the aging time when each sample was aged in argon gas using a block of 30 x 15 x 60 mm. Numbers C, K, and Q were aged at 450°C, and sample Y maraging steel was aged at 480°C. As is clear from the figure, the conventional maraging steel of trial number Y shows only shrinkage deformation during aging treatment, and the shrinkage deformation increases as the aging time increases. Therefore, in the case of long-term aging with large age hardening, the deformation rate becomes particularly large. On the other hand, the alloy of the present invention exhibits slight expansion deformation at the initial stage of aging, but changes to contraction deformation as aging progresses, so the final aging deformation is extremely small. In particular, trial number Q was aged for 10 hours and the deformation rate was almost zero. In this way, the alloy of the present invention undergoes expansion deformation once in the early stage of aging, and then slowly undergoes contraction deformation as age hardening progresses, so if an appropriate aging time is selected, the deformation rate can always be reduced to zero. It is. Tables 2 and 3 show the hardness of each sample as it was solution treated, the hardness when it was then aged, and the deformation rate when it was aged for 10 hours. The solution treatment temperature for samples A to X is 900 to 1000°C, and the solution treatment temperature for sample Y is 830°C. Further, the aging temperature of trial numbers A to X is 450°C, and the aging temperature of trial number Y is 480°C. As is clear from Table 2, the hardness of the alloy of the present invention after solution treatment is 350 or less on the Vickers hardness, which is a hardness that allows easy machining. In addition, even after aging, the Bitkers hardness is 500 to 650, which means that it can be used as a wear-resistant member.
Sufficient hardness. Moreover, the dimensional change rates due to age hardening are all sufficiently small values compared to Sample Y. Thus, the alloy of the present invention exhibits a significantly smaller deformation rate than conventionally known age hardenable alloys.

【table】

【table】

[Table] Figure 2 shows the tensile strength (Kgf/mm ² ) of each of the above samples after aging at 450°C. In the figure, the horizontal axis is molybdenum content, the vertical axis is vanadium content, and the numbers in the figure are tensile strength. As is clear from the figure, the tensile strength of all samples is 130Kg
f/ ^mm2 or more. In particular, in the composition range indicated by diagonal lines, the tensile strength was 200 Kg/mm ² or more, and an age-hardenable alloy with the highest strength after aging in this composition range and little deformation due to aging was obtained. In the figure, solid line 5 is 6.0 - (0.65 x vanadium weight%), solid line 6
is 8.0-(0.65×vanadium weight %), solid line 7 shows the upper limit of vanadium content of 6 weight %, and solid line 8 shows the lower limit of vanadium content of 2 weight %. Furthermore, the age hardenable alloy of the present invention had excellent corrosion resistance against the corrosion that is a problem with aqueous valve materials. As explained above, the age hardenable alloy of the present invention has a weight of 11 to 16% nickel and 2 to 4.5% manganese.
%, cobalt 5-12%, vanadium 0.5-7.5%,
It contains 8% or less of molybdenum, and even if mixed as impurities, it may contain 0.1% or less of carbon, 1% or less of silicon, and the balance is substantially iron.
It has an excellent effect in that the dimensional deformation due to age hardening, which is mainly composed of a martensitic structure, is significantly smaller than that of conventionally known age hardenable alloys. Therefore, the age hardenable alloy of the present invention is suitable for precision wear-resistant parts such as servo valves, for which conventional age hardenable alloys could not be used.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between aging time and deformation rate of the conventional and present age hardenable alloys, and FIG. 2 is a diagram showing the relationship between the tensile strength and the amounts of molybdenum and vanadium of the age hardenable alloy according to the present invention. It is a line diagram showing a relationship.

Claims (1)

[Claims] 1. Nickel 11-16%, manganese 2-2% by weight
4.5%, panadium 0.5-7.5%, molybdenum 8% or less, cobalt 5-12%, carbon 0.2% or less, the balance being essentially iron, and having an alloy structure mainly consisting of martensitic structure. Hardenable alloy. 2. Nickel 13-15.5%, manganese 2.6% by weight
~3.5%, Panadium 2~6%, Panadium 2~
6%, cobalt 8-11%, carbon 0.2% or less, and the amount of molybdenum and the amount of panadium satisfy the following formula: 6-0.65VMo8-0.65V. .