JP6015002B2 - Method for producing nitrogen-containing cobalt alloy - Google Patents

Description

  The present invention relates to a method for producing a nitrogen-containing cobalt alloy that dissolves nitrogen and improves mechanical strength.

  In the cobalt alloy, mechanical strength such as tensile strength and proof stress can be improved by changing the nitrogen content. Further, since the mechanical strength changes depending on the nitrogen content, it is necessary to control the nitrogen content (nitrogen concentration) to a predetermined value in order to produce a stable quality cobalt alloy.

  Patent Document 1 discloses a method of melting high nitrogen and high chromium steel in which N2 gas is blown from the bottom of the furnace into the molten metal in the arc furnace to dissolve nitrogen. A method for producing high nitrogen steel is disclosed in which nitrogen gas is filled and the steel is simultaneously melted and nitrogen is added in a pressurized nitrogen gas atmosphere.

JP-A-7-90345 JP2003-221615A

  In view of such circumstances, the present invention provides a method for producing a nitrogen-containing cobalt alloy in which an appropriate amount of nitrogen is dissolved in the cobalt alloy.

  The present invention provides a nitrogen-containing cobalt alloy in which a molten cobalt alloy is held for a period of time in which the nitrogen concentration in the cobalt alloy reaches a target value in a nitrogen gas atmosphere at a pressure selected in the range of 2.5 kPa to 62.5 kPa. It concerns the method.

  The present invention also provides a nitrogen-containing cobalt alloy that obtains in advance the pressure, holding time, and nitrogen concentration data of the nitrogen gas atmosphere at the melting temperature of the cobalt alloy to determine the pressure and holding time of the nitrogen gas atmosphere with respect to the target nitrogen concentration. This relates to the manufacturing method.

  According to the present invention, the melted cobalt alloy is held for a period of time during which the nitrogen concentration in the cobalt alloy becomes a target value in a nitrogen gas atmosphere at a pressure selected in the range of 2.5 kPa to 62.5 kPa. An excellent effect that a nitrogen-containing cobalt alloy having a nitrogen concentration can be easily produced is exhibited.

It is a graph which shows the relationship of the pressure of nitrogen gas atmosphere, holding time, and nitrogen concentration in the melting temperature of the cobalt alloy in the Example of this invention. It is a graph which shows the relationship between the temperature in a fixed nitrogen gas pressure, holding time, and nitrogen concentration. It is a schematic block diagram of the melting stock melting furnace where this invention is implemented. It is a schematic block diagram of the melting casting furnace where this invention is implemented.

  Embodiments of the present invention will be described below with reference to the drawings.

  The present inventor has a composition of Co of 63.65 to 64.48% wt, Cr of 27.69 to 28.16% wt, Mo of 5.91 to 6.08% wt, other C, Si, Mn For various cobalt alloys containing Ni, Ni, Al, etc., the relationship between the concentration of nitrogen dissolved in the cobalt alloy was investigated using temperature, nitrogen gas (N2) environment, and time as parameters.

  FIG. 1 shows that a cobalt alloy was melted in a vacuum vessel and maintained at 1480 ° C., and further dissolved in a cobalt alloy when the atmosphere of the cobalt alloy was changed to nitrogen gas and the pressure of the nitrogen gas was changed from normal pressure to 90 kPa. It shows a change in the concentration of nitrogen (N). In FIG. 1, the horizontal axis represents √Pa, and the vertical axis represents the nitrogen concentration (wtppm).

  For example, curve A shows the concentration of nitrogen dissolved in the cobalt alloy when the pressure of nitrogen gas in the test atmosphere is increased when held at 1480 ° C. for 10 minutes.

  Similarly, a plurality of curves B to F are respectively held for 30 minutes, 60 minutes, 120 minutes, 180 minutes, and 240 minutes in the test atmosphere of the molten cobalt alloy, and the nitrogen gas pressure is increased. In this case, the concentration of nitrogen dissolved in the cobalt alloy is shown.

  The nitrogen concentration dissolved in the cobalt alloy was measured by combustion analysis of the solidified cobalt alloy using a nitrogen analyzer manufactured by LECO.

  As shown in FIG. 1, when the holding time is constant, increasing the nitrogen gas pressure increases the nitrogen concentration in the cobalt alloy, and when the nitrogen gas pressure is constant, the holding time is increased. By increasing the concentration, the nitrogen concentration in the cobalt alloy increases.

  FIG. 2 is a graph showing the relationship between nitrogen concentration, temperature and holding time at a nitrogen gas pressure of 20 kPa. In FIG. 2, curve A is holding time 10 minutes, curve B is holding time 30 minutes, curve C represents a retention time of 60 minutes, and curve D represents a retention time of 120 minutes.

  In FIG. 2, the holding temperature is changed from 1480 ° C. to 1540 ° C., but it can be seen that the nitrogen concentration has not changed significantly. Therefore, it can be seen that the nitrogen gas pressure and the holding time are preferably used as parameters for controlling the nitrogen concentration.

  As described above, in a molten state of the cobalt alloy, that is, at a temperature selected between 1480 ° C. and 1540 ° C., the relationship between the nitrogen gas pressure, the holding time, and the nitrogen concentration is acquired in advance, so that a desired value can be obtained. It is possible to easily set the conditions of the nitrogen dissolution treatment for the nitrogen concentration (see X zone, Y zone, and Z zone in FIG. 1).

  The nitrogen concentration is selected between 100 ppm and 1600 ppm. Further, the nitrogen concentration corresponds to 100 ppm to 1600 ppm, and the pressure of the selected nitrogen gas is practically between 2.5 kPa and 62.5 kPa.

  For example, in FIG. 1, when the nitrogen concentration is 1000 ppm, the conditions for the nitrogen dissolution treatment are obtained in the Y zone. For example, when the holding time is set to 60 minutes, the point at which the nitrogen concentration is 1000 ppm is the α point on the curve C, and the nitrogen gas pressure is 160 × 160 Pa = 25.6 kPa. Alternatively, if the nitrogen gas pressure is set to 40 kPa, the holding time is the β point between 30 minutes and 60 minutes when the nitrogen concentration is 1000 ppm. If the time between 30 minutes and 60 minutes is divided at the position of the β point, the holding time is about 40 minutes.

  Further, the width (size in the vertical direction) of each zone is determined by the allowable error of the nitrogen concentration to be set. If the allowable error of the nitrogen concentration is set strictly, the width of the zone is set narrow. For example, in FIG. 1, when the nitrogen concentration is set to 1000 ppm and an error is set as the Y zone, if the holding time is 60 minutes (curve C), the pressure of the nitrogen gas is 19.6 kPa to 28 Controlled for .9 kPa.

  Thus, by obtaining in advance the relationship between the nitrogen gas pressure, the holding time and the nitrogen concentration at the melting temperature of the predetermined cobalt alloy, it is possible to easily determine the conditions of the nitrogen dissolution treatment with the target nitrogen concentration. In addition, the control conditions for controlling the target nitrogen concentration can be easily obtained.

  Next, with reference to FIG. 3, the case where the melting stock of a nitrogen-containing cobalt alloy is manufactured is demonstrated.

  FIG. 3 shows a melting stock melting furnace 1 for carrying out this embodiment. In the figure, 2 indicates a melting furnace chamber, and the melting furnace chamber 2 is a vacuum vessel. A required number of ingot cases 3 are accommodated in predetermined positions in the melting furnace chamber 2, and a melting furnace 4 is disposed above the ingot case 3.

  The melting furnace 4 includes a melting furnace body 5, a high-frequency heater 6, a tilting mechanism (not shown), and the like, and the melting furnace 5 is supported by the tilting mechanism so as to be tiltable.

  A vacuum pump 7 is connected to the melting furnace chamber 2 and is evacuated by the vacuum pump 7 so that the inside becomes a predetermined vacuum pressure. Further, a nitrogen gas supply source 8 is connected to the melting furnace chamber 2, and a nitrogen gas having a required pressure can be supplied to the melting furnace chamber 2 by the nitrogen gas supply source 8. A heating power source 9 is connected to the high-frequency heater 6, and the heating power source 9 can supply high-frequency power to the high-frequency heater 6.

  Further, a pressure detector 11 for detecting the pressure in the melting furnace chamber 2 is provided, and a temperature detector 12 for detecting the temperature of the molten cobalt alloy 13 in the melting furnace chamber 2 or the melting furnace body 5. Is provided. As a method for detecting the temperature of the molten cobalt alloy 13, for example, there is a method of detecting by inserting a thermocouple housed in a protective tube such as ceramics into the molten cobalt alloy.

  Further, the melting stock melting furnace 1 includes a control device 15, to which detection signals from the pressure detector 11 and the temperature detector 12 are input, and the control device 15 Based on the detection signals from the pressure detector 11 and the temperature detector 12, the nitrogen gas supply source 8, the heating power source 9, and the moving mechanism (not shown) are controlled to a required state at a required timing.

  Hereinafter, the operation of the melting stock melting furnace 1 will be described.

  An ingot (a lump of cobalt alloy before nitrogen is melted) is charged into the melting furnace body 5. The melting furnace chamber 2 is evacuated and the internal pressure is detected by the pressure detector 11. When the melting furnace chamber 2 reaches a predetermined vacuum pressure (first vacuum pressure), high frequency power is supplied to the high frequency heater 6 to heat the ingot at high frequency.

  When the ingot is melted, the melting temperature is detected by the temperature detector 12, and the power supplied to the high-frequency heater 6 is controlled so that the molten metal is held at a predetermined temperature.

  Further, when the melting furnace chamber 2 reaches a predetermined vacuum pressure (second vacuum pressure), evacuation is stopped, the nitrogen gas supply source 8 is controlled, and nitrogen gas is supplied to the melting furnace chamber 2. Is introduced. The introduced nitrogen gas pressure is detected by the pressure detector 11, and when the target pressure is reached, the supply of nitrogen gas is stopped, and the nitrogen gas pressure is maintained at the same temperature and the same nitrogen gas pressure for a predetermined time. By maintaining at a predetermined temperature and a predetermined nitrogen gas pressure for a predetermined time, a cobalt alloy in which nitrogen is dissolved at a target concentration is obtained. The predetermined time, the predetermined temperature, and the predetermined nitrogen gas pressure are set based on previously acquired data, for example, based on FIG. 1, corresponding to the target nitrogen concentration. Further, the nitrogen gas supply source 8 and the heating power source 9 are controlled by the control device 15 so that the set temperature and nitrogen gas pressure are obtained.

  When a predetermined time has elapsed, the melting furnace 4 is tilted by a tilting mechanism (not shown), and the molten cobalt alloy 13 is poured into the ingot case 3. The ingot case 3 poured with a cobalt alloy is cooled in the melting furnace chamber 2 and solidified. After cooling to a predetermined temperature, the melting furnace chamber 2 is returned to atmospheric pressure, the ingot case 3 is taken out from the melting furnace chamber 2, and the solidified melting stock is taken out from the ingot case 3.

  When a casting is manufactured using a cobalt alloy in which nitrogen is dissolved, the melting stock is melted again and poured into a mold to manufacture a desired part.

  In the melting stock melting furnace 1, a melting stock in which nitrogen is dissolved is manufactured and a part is cast using the melting stock. However, the present invention may be implemented in the process of casting the part.

  FIG. 4 shows a melting and casting furnace 16 in which the present invention is implemented. 4 that are the same as those shown in FIG. 3 are given the same reference numerals, and descriptions thereof are omitted.

  In the melting and casting furnace 16, a mold 17 is provided instead of the ingot case 3.

  The ingot is charged into the melting furnace body 5, and the casting furnace chamber 18 which is a vacuum vessel is evacuated. The ingot is melted in the melting furnace body 5, nitrogen gas is supplied at a predetermined pressure, and held at a predetermined pressure, temperature, and predetermined time, and nitrogen is dissolved in the molten cobalt alloy.

  The molten cobalt alloy 13 in which nitrogen is dissolved at a predetermined concentration is poured into the mold 17 from the gate 19.

  Also in the melting and casting furnace 16, in order to obtain a target nitrogen concentration, a predetermined time, a predetermined temperature, and a predetermined nitrogen gas pressure are set based on previously acquired data and controlled by the control device 15.

DESCRIPTION OF SYMBOLS 1 Melting stock melting furnace 2 Melting furnace chamber 3 Ingot case 4 Melting furnace 5 Melting furnace body 6 High frequency heater 7 Vacuum pump 8 Nitrogen gas supply source 9 Heating power supply 11 Pressure detector 12 Temperature detector 13 Molten cobalt alloy 15 Control device 16 Melting and casting furnace 17 Mold 18 Casting furnace chamber 19 Gate

Claims (2)

The melting temperature is kept at a temperature selected from the range of 1480 ° C. to 1540 ° C., the molten Co is 63.65 to 64.48% wt, Cr is 27.69 to 28.16% wt, Mo is 5.91 to The nitrogen concentration in the cobalt alloy is 100 ppm in a nitrogen gas atmosphere at a pressure selected from a cobalt alloy containing 6.08% wt and other C, Si, Mn, Ni, and Al in the range of 2.5 kPa to 62.5 kPa. A method for producing a nitrogen-containing cobalt alloy, characterized by holding for a time that is a target value selected between ˜1200 ppm .   The pressure, holding time, and nitrogen concentration data of the nitrogen gas atmosphere at the melting temperature of the cobalt alloy are acquired in advance, and the pressure and holding time of the nitrogen gas atmosphere with respect to the target nitrogen concentration are obtained based on the data. A method for producing a nitrogen-containing cobalt alloy.

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