KR20020016188A - Method of low thermal expansion alloys for precision machine tools - Google Patents

Abstract

PURPOSE: A method for manufacturing a low thermal expansion invar alloy for precision machine tools is provided to manufacture an invar alloy in which mechanical characteristics such as strength, hardness and aging are improved so as to use the invar alloy as a material for the precision machine tools. CONSTITUTION: The method for manufacturing a low thermal expansion invar alloy for precision machine tools comprises the processes of manufacturing an ingot in a vacuum induction melting furnace using a raw material comprising 0.35 wt.% of C having a purity of 99.9 wt.%, 38 wt.% of Ni, 0.5 wt.% of Co, 2 wt.% of Mo, 1 wt.% of Cr, 0.27 wt.% of Mn, 0.48 wt.% of Si, 0.1 wt.% of Ti, maximum 5 wt.% of S and a balance of Fe; hot forging the heated ingot after heating the ingot to 1100 deg.C; manufacturing wire rods of 12 ψ by hot rolling the heated processed material after heating to 1100 deg.C a processed material which is manufacture by grinding the resulting material so as to remove defects formed on the surface of the hot rolled material; performing solution treatment on the wire rods at 1300 deg.C; and carrying out aging treatment on the solution treated wire rods at 800 deg.C for 2 hours.

Description

Method of manufacturing low thermal expansion inva alloy for precision machine tools {Method of low thermal expansion alloys for precision machine tools}

The present invention relates to a low thermal expansion inva alloy for precision machine tools, and more particularly, iron (Fe), carbon (C), nickel (Ni), cobalt (Co), molybdenum having a purity of 99.9% by weight. Ingots are prepared in a vacuum induction furnace using (Mo), (carbon) C, chromium (Cr), manganese (Mn), and titanium (Ti) as raw materials, and heated to 1100 ° C, followed by hot forging. After that, the grinding work is performed to remove the surface defects of the processed material, and the processed material is heated to 1100 ° C., followed by hot rolling to form a wire of 12ψ, followed by solution treatment at 1100, 1200, and 1300 ° C. for 1 hour. By aging at 500, 600, 700, and 800 ° C. for 2 hours, titanium (Ti) carbides are formed to affect grain refinement, thereby increasing the precision of machine tools and improving durability. Localization of invar alloy to improve the industrial technology of enterprises, It provides a low thermal expansion Invar alloy precision machine tools to help equip the force.

Invar alloys generally require precision measuring instruments and low thermal expansion since Guillaume discovered that the Fe-36 wt% Ni alloy exhibited a small coefficient of thermal expansion (α) of about 1.2 × 10 ^-6 / ° C or less near room temperature. Various applications such as electronic components and power transmission lines have been attempted.

In particular, in order to improve the precision of machining in the field of precision machinery, the research on applying Invar alloy with low thermal expansion to machine tool parts is being actively conducted, and the spindle housing and wire cutting M / C of CNC M / C of precision machine tools Invar alloy is applied to parts that directly affect the precision of machining, such as arm, main spindle mounted on CNC machine and head stock body.

However, Fe-Ni-based invar alloy has the disadvantages of low mechanical strength, good machinability, good weldability, while rich in machinability, such as forging, rolling, drawing, etc. Furthermore, the alloy has a low magnetic transformation point and a temperature of about 520 K or more. There is a problem in that the invar effect is lost and is greatly restricted in the application at high temperatures.

The present invention has been made in order to solve the above-mentioned problems, the object of the present invention is to produce an invar alloy with improved mechanical properties such as strength, hardness, deterioration in order to be able to use the invar alloy as a material for precision machine tools to provide.

The above object is, according to the present invention, iron (Fe), carbon (C), nickel (Ni), cobalt (Co), molybdenum (Mo), chromium (Cr), manganese having a purity of 99.9% by weight. Ingot is prepared in a vacuum induction furnace using (Mn), silicon (Si), sulfur (S), and titanium (Ti) as raw materials, and heated to 1100 ° C., followed by hot forging. Grinding work is performed to remove the surface defects of the material, and the processed material is heated to 1100 ℃ and hot rolled to make 12ψ wire, and solution treatment is performed at 1100, 1200 and 1300 ℃ for 1 hour, respectively, and 500, 600 It is achieved by producing the invar alloy by aging at 700, 800 ℃ for 2 hours each.

Hereinafter, the configuration of the present invention will be described.

0.35% by weight of carbon (C) with a purity of 99.9% by weight, 38% by weight of nickel (Ni), 0.5% by weight of cobalt (Co), 2% by weight of molybdenum (Mo), 1% by weight of chromium (Cr), manganese (Mn) 0.27% by weight, silicon (Si) 0.48% by weight, titanium (Ti) 0.1% by weight, sulfur (S) up to 5% by weight and residual iron (Fe).

Referring to the production method of the present invention Inba alloy consisting of the above configuration is as follows.

First, 0.35% by weight of carbon (C) having a purity of 99.9% by weight, 38% by weight of nickel (Ni), 0.5% by weight of cobalt (Co), 2% by weight of molybdenum (Mo), and 1% by weight of chromium (Cr) , Raw material composed of 0.27% manganese (Mn), 0.48% silicon (Si), 0.1% titanium (Ti), up to 5% sulfur (S) and residual iron (Fe) in a vacuum induction furnace Ingot).

Then, the ingot is heated to 1100 ° C and hot forging is performed, and the grinding operation for grinding the surface to remove the surface defects of the processing material.

In addition, after heating the processing material to 1100 ℃ and hot wire rolling to make a 12 ψ wire and solution treatment at 1300 ℃, and then aged at 800 ℃ 2 hours.

Referring to the embodiment of the invar alloy of the present invention prepared by the above-described manufacturing method as follows.

First, the above-mentioned carbon (C) 0.35% by weight, nickel (Ni) 38% by weight, cobalt (Co) 0.5% by weight, molybdenum (Mo) 2% by weight, chromium (Cr) 1% by weight, manganese (Mn) Sample 1 composed of 0.27% by weight, 0.48% by weight of silicon (Si), up to 5% by weight of sulfur (S) and residual iron (Fe),

0.35 wt% carbon (C), 38 wt% nickel (Ni), 0.5 wt% cobalt (Co), 2 wt% molybdenum (Mo), 1 wt% chromium (Cr), 0.27 wt% manganese (Mn), Sample 2 composed of 0.48% by weight of silicon (Si), up to 5% by weight of sulfur (S), 0.1% by weight of vanadium (V), and residual iron (Fe),

0.35 wt% carbon (C), 38 wt% nickel (Ni), 0.5 wt% cobalt (Co), 2 wt% molybdenum (Mo), 1 wt% chromium (Cr), 0.27 wt% manganese (Mn), Sample 3 composed of 0.48 wt% of silicon (Si), up to 5 wt% of sulfur (S), 0.1 wt% of niobium (Nb), and residual iron (Fe);

0.35 wt% carbon (C), 38 wt% nickel (Ni), 0.5 wt% cobalt (Co), 2 wt% molybdenum (Mo), 1 wt% chromium (Cr), 0.27 wt% manganese (Mn), 10 kg of ingot in the vacuum induction furnace were prepared by preparing a sample 4 composed of 0.48% by weight of silicon (Si), 5% by weight of sulfur (S), 0.1% by weight of titanium (Ti) and residual iron (Fe). (Ingot) is manufactured.

Type of composition Fe C Ni Co Mo Cr Mn Si S v Nb Ti Sample 1 bal. 0.35 38 0.5 2 One 0.27 0.48 <5 - - - Sample 2 bal. 0.35 38 0.5 2 One 0.27 0.48 <5 0.1 - - Sample 3 bal. 0.35 38 0.5 2 One 0.27 0.48 <5 - 0.1 - Sample 4 bal. 0.35 38 0.5 2 One 0.27 0.48 <5 - - 0.1

The ingot of each sample manufactured in the vacuum induction furnace is heated to 1100 ° C., and then hot forged, and then processed into a cubic shape of 50 mm or less × 50 mm or less × 750 mm or more, followed by grinding to remove surface defects of the processed material. The material was heated up to 1100 ° C. and then hot rolled to make a wire of 12ψ (hereinafter referred to as a specimen). The specimens thus prepared were subjected to solution treatment for 1 hour at 1100, 1200, and 1300 ° C, respectively, and then aged for 2 hours at 500, 600, 700, and 800 ° C.

The microstructure was etched with an etchant mixed with 100 ml hydrochloric acid, 7 g iron chloride, 2 g copper chloride, 5 ml nitric acid, 200 ml methanol, and 100 ml distilled water, followed by an optical microscope, a scanning electron microscope (Hitachi S-2400), and a field emission runner. Observation with an electron microscope (FEG-SEM, Hitachi S-4200) and transmission electron microscope (JEOL H-9000NAR) to determine the shape and type of carbide.

Hereinafter, the microstructures observed by the optical microscope will be described in Tables 2 to 4.

Sample 1 Sample 2 Sample 3 Sample 4 500 ℃ 600 ℃ 700 ℃ 800 ℃

As can be seen from Table 1, after 1-hour solution solution at 1100 ℃ and aged for 2 hours at 500, 600, 700, 800 ℃, respectively, the microstructure change of each sample is shown in Table 2, It can be seen that the grain size of the specimen 4 (Ti addition) is much finer than that of the specimen 1 (no addition), which is due to the fine precipitation of titanium (Ti) carbide, which causes a pinning effect. It can be seen that it interfered with the grain growth of the knight.

In addition, in the case of specimen 4, it was observed that recrystallization occurred, which is caused by recrystallization as the titanium (Ti) carbide becomes a nucleation site, resulting in grain refinement.

In the case of Specimen 1, there was no change in grain size according to the aging temperature, because Specimen 1 had no carbide forming element added, and therefore, no carbide was produced, thus having no effect of aging treatment.

No.1 No.2 No.3 No.4 500 ℃ 600 ℃ 700 ℃ 800 ℃

In addition, Table 3 shows the results of observing changes in the microstructure of the specimens after aging at 500, 600, 700, and 800 ° C for 2 hours after solution treatment at 1200 ° C for 1 hour, respectively. As can be seen, as the solution temperature increases, the grain size increases compared to the solution solution 1100 ° C. In particular, at 1200 ° C of specimen 4, it can be seen that abnormal grain growth occurs, in which some grains grow enormously. As mentioned above, grain growth is caused by precipitation of titanium carbide. Because it suppressed.

Sample 1 Sample 2 Sample 3 Sample 4 500 ℃ 600 ℃ 700 ℃ 800 ℃

In Table 4, at 1300 ° C. of specimen 4, abnormal grain growth was not observed at 1200 ° C., and the grain size was generally similar, which is due to the increase in solution treatment temperature. This is because the effect of inhibiting grain growth due to the erosion was not affected.

On the other hand, in order to see the overall distribution of carbides that could not be seen because of the small size in the optical microscope observation observed in the scanning electron microscope in Table 5 as follows.

Psalm 1 Psalm 2 Psalm 3 Psalm 4 500 ℃ 600 ℃ 700 ℃ 800 ℃

First, the observation results of the specimens aged at 500, 600, 700, and 800 ° C after the solution treatment at 1100 ° C are shown in Table 5. In the case of specimen 4, it can be seen that the carbides move to the grain boundary as the aging temperature increases. This is because carbides in the mouth moved to unstable grain boundaries as the aging temperature increased. In the case of specimen 1, since no carbide forming element was added, carbides could not be observed as shown in Table 5.

In addition, both specimens 1 and 4 could observe undissolved segregates during the solution treatment of about 2 to 4 μm in the grain size and grain boundaries, as the solution treatment temperature increased to 1200 and 1300 ° C. As segregates dissolved in the matrix, their amount was reduced but not completely removed (see Tables 6 and 7).

Psalm 1 Psalm 2 Psalm 3 Psalm 4 500 ℃ 600 ℃ 700 ℃ 800 ℃

Psalm 1 Psalm 2 Psalm 3 Psalm 4 500 ℃ 600 ℃ 700 ℃ 800 ℃

In addition, in the case of specimens 2 and 3, the amount of carbides in the grain boundary and in the mouth is smaller than in specimen 1, which is because the relatively small amount of carbides compared to specimen 4 may cause the pinning ( It does not cause pinning effect.

The general distribution of carbides could be seen by normal scanning electron microscopy, but since the shape and size of each carbide could not be observed in detail, the field emission scanning electron microscopy (FEG-SEM) with excellent resolution 1100. After observing the specimens aged at 600 ° C. and 800 ° C. for 2 hours after the solution treatment at 1 ° C. for 1 hour, the photographs are shown in Table 8.

Psalm 1 Psalm 2 Psalm 3 Psalm 4 600 ℃ 800 ℃

And, in the case of specimen 4, the carbides can be seen that 50 ~ 90nm spherical carbides are separated independently from each other when the aging temperature is 600 ℃, but the carbides are bonded to each other as the temperature increases to 800 ℃ It can be seen that the phenomenon of overaging, which is increased to about 200 nm, appears. This is consistent with the increase in the amount of carbides as the aging temperature in Table 5 above increases the size of carbides at 800 ° C.

In addition, in the case of specimen 1, only the sites where the precipitates are estimated to be left remain, because the binding strength between the inva alloy-specific austenite base and the precipitates is weak, and the precipitates are removed during etching.

In specimens 2 and 3, carbides of 200-400 nm in size were observed, which was about 3 to 4 times larger than the carbides in specimen 4, and the amount of carbides was small as seen in the scanning electron microscope. As a result, it was observed that the distribution was concentrated around the grain boundary. The shape of the carbide is generally disc-shaped, and the picture shows holes without carbides, which are removed by mechanical and chemical action during polishing and etching.

On the other hand, according to Zener, the grain growth suppression mechanism can be expressed as Equation 1 when considering the balance between the pinnig force and the grain growth driving force of the dispersed particles.

D: austenite grain size

d: precipitate particle diameter

f _V : volume fraction of precipitate

ξ ″: 2/3

Therefore, according to the Zener equation, the grain growth inhibitory effect increases as the size of carbide decreases and the volume fraction of carbide increases, and the carbides of specimens 2 and 3 are observed in the scanning electron microscope and the field emission scanning electron microscope. The size of is 3 to 4 times larger than that of specimen 4, and the volume fraction of carbide is small. When these conditions are applied to Zener equation, abnormal grain growth observed in specimen 4 is observed in specimen 2 and specimen 3. The reason for the loss is explained. That is, since the force for inhibiting grain growth in the specimens 2 and 3 is smaller than that of the specimen 4, abnormal grain growth does not appear.

On the other hand, in order to analyze the types of spherical carbides of about 50 to 90 nm observed in the field emission scanning electron microscope of Specimen 4, permeation of the specimens aged at 600 and 800 ° C for 2 hours after solution treatment at 1100 ° C for 1 hour Electron microscopy (TEM) images and EDS analysis results are shown in Table 9.

600 ℃ 600 ℃ 600 ℃ 800 ℃ 800 ℃ Image EDS

As a result of transmission electron microscopy analysis, various carbides were found according to the temperature of the aging treatment. When the aging temperature was 600 ° C, three kinds of carbides, spherical and plate-shaped, were observed. (Mo, Ti) carbides having different ratios of Mo) and titanium (Ti).

In addition, even when the aging temperature was 800 ° C, two types of carbides, spherical and plate-shaped, were observed. In the case of spherical carbides, the EDS analysis showed that the same (Mo, Ti) -based carbides as the 600 ° C-aging specimens were used. In the case of carbides, molybdenum (Mo) -based carbides were identified, unlike the above-mentioned EDS analysis.

Therefore, it can be seen that the major carbides that suppress the grain growth of the specimen 4 to exhibit abnormal grain growth are (Mo, Ti) carbide and molybdenum (Mo) carbide as shown in the transmission electron microscope analysis results.

The transmission electron microscope observation results of the No. 2 specimen are shown in Table 10.

600 ℃ 600 ℃ 800 ℃ Image EDS

When the aging treatment temperature of Specimen 2 was 600 ° C., two types of carbides, spherical and plate-shaped, were observed. As a result of the EDS analysis, molybdenum (Mo) carbides made of molybdenum (Mo) were observed.

However, the results of EDS analysis of the two types of carbides observed in Specimen 2 were almost identical, and the size of these carbides was found to be within the average size range of 200-400 nm of carbides observed in the field emission scanning microscope. These results were observed from the front and side of the ribtene (Mo) carbide.

Also, when the aging treatment temperature of Specimen 2 was 800 ° C, one kind of carbides could be observed, and molybdenum (Mo) having a smaller amount of molybdenum (Mo) than the carbides shown at 600 ° C by EDS analysis thereof. ) Carbides.

The transmission electron microscope observation results of the specimen 3 are shown in Table 11.

800 ℃ Image EDS

When the aging temperature of Specimen 3 was 600 ° C, as observed in the field emission scanning electron microscope, the amount of carbides was not observed. At 800 ° C, one type of carbide was observed. Analysis results are molybdenum (Mo) carbide consisting of molybdenum (Mo).

As described above, in the case of specimen 4, the growth of grain due to the pinning effect of titanium (Ti) carbide and the titanium (Ti) carbide act as recrystallization sites. It can be seen that the grain size becomes fine, the amount of carbide increases as the aging temperature increases after solution treatment of specimen 4, and titanium (Ti), (Ti, Mo) based carbides are formed to reduce grain size. Influence allows the invar alloy to have high mechanical properties.

As described above, the present invention develops a low thermal expansion alloy capable of maintaining thermal stability and high strength during high speed operation of a precision machine tool, thereby enabling the application of a new material technology to a machine tool component, thereby increasing the precision of a machine tool. It is an excellent invention that can improve the industrial technology of the enterprise by improving the durability and strengthening the durability, and further enhance the international competitiveness by the localization of Invar alloy.

Claims (2)

0.35% by weight of carbon (C) with a purity of 99.9% by weight, 38% by weight of nickel (Ni), 0.5% by weight of cobalt (Co), 2% by weight of molybdenum (Mo), 1% by weight of chromium (Cr), manganese (Mn) 0.27% by weight, silicon (Si) 0.48% by weight, titanium (Ti) 0.1% by weight, sulfur (S) up to 5% by weight and low thermal expansion for precision machine tools, characterized in that the composition is composed of iron (Fe) Invar alloy. 0.35% by weight of carbon (C) with a purity of 99.9% by weight, 38% by weight of nickel (Ni), 0.5% by weight of cobalt (Co), 2% by weight of molybdenum (Mo), 1% by weight of chromium (Cr), manganese (Mn) 0.27% by weight, silicon (Si) 0.48% by weight, titanium (Ti) 0.1% by weight, sulfur (S) up to 5% by weight, and raw materials composed of residual iron (Fe) ingot in a vacuum induction furnace After manufacturing, and heated to 1100 ℃ hot forging processing, performing a grinding operation for removing the surface defects of the processing material, heating the processing material to 1100 ℃ and made a wire of 12ψ through hot rolling 1300 A process for producing a low thermal expansion inva alloy for precision machine tools, wherein the solution is subjected to a solution treatment at 캜, and aged at 800 캜 for 2 hours.