JP6568425B2 - Deterioration degree determination method and metalworking member manufacturing method - Google Patents

Description

  The present invention relates to a degradation degree determination method and a method of manufacturing a metal workpiece.

  In heat treatment such as quenching of a metal material, a cooling liquid having a cooling rate slower than that of water is generally used to prevent quench cracking. In recent years, an aqueous polymer solution has been put into practical use as a cooling liquid in order to avoid the risk of fire associated with high temperature operation.

  Such a cooling liquid deteriorates and continues to be used, and the cooling relaxation ability is reduced, so that the metal material is easily cracked. In order to prevent the metal material from cracking, it is necessary to replace the coolant with a new coolant before such a state occurs. If the period until the replacement is short, the consumption of the cooling liquid increases and the manufacturing cost of the metal material increases. Therefore, in order to lengthen the replacement period of the coolant, it is required to establish a management index that can appropriately determine whether the coolant can be used continuously.

  In response to such a request, the time for which the test piece is cooled to a predetermined temperature by immersing the heated test piece in the coolant to be managed is measured, and the reference data is obtained in advance from the measured cooling time. A cooling liquid management method has been proposed in which the concentration of the cooling liquid to be managed is estimated using the relationship between the cooling time and the cooling liquid concentration (Japanese Patent Laid-Open No. 2014-167487). In this cooling liquid management method, the concentration is obtained from the cooling time of the cooling liquid, and the concentration is used as a management index for determining whether or not the cooling liquid can be continuously used.

  However, the cooling liquid management method requires a complicated operation of immersing the heated test piece in the cooling liquid to be managed and measuring the cooling time.

  In addition, from the results of previous studies by the inventors, it is known that when an aqueous polymer solution is used as the cooling liquid, the molecular weight of the polymer decreases with use. Therefore, for example, even if the aqueous polymer solution has the same concentration, it is considered that the aqueous polymer solution having a long use time has a small molecular weight of the polymer, and the susceptibility to firing cracks is different. Therefore, for example, when a new polymer aqueous solution is added to the polymer aqueous solution that is being used to suppress deterioration, whether or not the coolant can be continuously used only by the coolant concentration as in the above-mentioned coolant management method. It is considered difficult to judge.

JP 2014-167487 A

  The present invention has been made on the basis of the above-described circumstances, and a degradation degree determination method and a metal workpiece that can easily and accurately determine whether a polymer aqueous solution used for a cooling liquid for heat treatment of a metal material can be continuously used. The purpose is to provide a manufacturing method.

  In order to establish a management index that can determine whether or not the aqueous polymer solution can be used continuously, the present inventors have measured and examined physical property values of a plurality of aqueous polymer solutions having different degrees of deterioration. As a result, the present inventors have found that a combination of polymer concentration and kinematic viscosity can be adopted as the management index. Specifically, the present inventors determined the kinematic viscosity when diluting a polymer aqueous solution that has progressed with water and the kinematic viscosity of a polymer aqueous solution that has not progressed in the same polymer concentration as the diluted polymer aqueous solution. As a result of comparison, it was found that the kinematic viscosity decreases as the deterioration progresses. Thus, the inventors have found that a combination of polymer concentration and kinematic viscosity can be used to determine the degree of deterioration of an aqueous polymer solution. Based on this finding, the present inventors have completed the present invention.

  That is, the invention made in order to solve the above problems is a method for determining the degree of deterioration of an aqueous polymer solution used for a cooling liquid for heat treatment of a metal material, comprising the steps of measuring the kinematic viscosity of the aqueous polymer solution, A step of obtaining the polymer concentration of the aqueous polymer solution at the time of measuring the kinematic viscosity, and a step of determining the degree of deterioration of the aqueous polymer solution based on the kinematic viscosity obtained in the measurement step and the polymer concentration obtained in the acquisition step. This is a characteristic deterioration degree determination method.

  In order to determine the degree of deterioration of the aqueous polymer solution, the degradation degree determination method may be performed by measuring the kinematic viscosity of the aqueous polymer solution and obtaining the polymer concentration of the aqueous polymer solution at the time of measuring the kinematic viscosity. Since it is not necessary to perform a complicated operation such as immersion to measure the cooling temperature, it is possible to easily determine whether the aqueous polymer solution can be used continuously. Further, since the degree of deterioration of the aqueous polymer solution is determined based on the kinematic viscosity and the polymer concentration corresponding to the kinematic viscosity, it is possible to accurately determine whether the polymer aqueous solution can be used continuously.

  In the determination step, a threshold line indicating whether or not the polymer aqueous solution can be used continuously is set in the coordinate system with the kinematic viscosity and the polymer concentration as axes, and the polymer aqueous solution can be used continuously when the kinematic viscosity is larger than the threshold line. It is good to judge. In this way, the degree of deterioration of the aqueous polymer solution can be determined by determining whether the aqueous polymer solution can be used continuously by using a coordinate system with the kinematic viscosity and the polymer concentration as axes, which set a threshold line indicating whether the aqueous polymer solution can be used continuously. Can be determined more easily.

The coordinate system is a biaxial orthogonal coordinate system with kinematic viscosity y and polymer concentration x as axes, and the threshold line is a linear function of y = ax + b (a is a positive constant, b is a constant). In the case of the following formula (1), it may be determined that the aqueous polymer solution can be used continuously, and in the case of the following formula (2), it may be determined that the aqueous polymer solution cannot be used continuously.
y> ax + b (1)
y ≦ ax + b (2)

  Thus, by expressing the threshold line with a linear function of a biaxial orthogonal coordinate system with the kinematic viscosity y and the polymer concentration x as axes, it is possible to more accurately determine whether or not the continuous use can be performed, and the target kinematic viscosity. It is easy to grasp the difference between the polymer aqueous solution and the threshold line.

  In the acquisition step, the polymer concentration of the aqueous polymer solution at the time of measuring the kinematic viscosity in the measurement step may be measured. Thus, by measuring the polymer concentration of the aqueous polymer solution at the time of measuring the kinematic viscosity in the measurement process, the polymer can be measured only by a simple operation of measuring the kinematic viscosity and the polymer concentration without any work such as dilution of the aqueous polymer solution. Whether or not the aqueous solution can be used continuously can be determined.

  The method further comprises a step of diluting the aqueous polymer solution to a specific concentration before the measurement step, measuring the kinematic viscosity of the aqueous polymer solution after the dilution step in the measurement step, and obtaining the polymer concentration obtained in the acquisition step after the dilution step. A specific concentration may be employed. In this way, by measuring the kinematic viscosity of the polymer aqueous solution after dilution to a specific concentration and adopting the specific concentration after the dilution step, it is possible to determine whether or not the polymer aqueous solution can be continuously used based on only the kinematic viscosity. The degree of deterioration of the polymer aqueous solution can be easily determined.

  The step of determining the average heat transfer coefficient between 200 ° C. and 400 ° C. between the metal material and the polymer aqueous solution based on the kinematic viscosity obtained in the measurement step and the polymer concentration obtained in the acquisition step; It is preferable to include a step of determining that the aqueous polymer solution can be continuously used when the average heat transfer coefficient obtained in the identification step is smaller than the threshold value. Here, since the temperature range of 200 ° C. or more and 400 ° C. or less is a temperature range in which burning cracks are generated based on an empirical rule, the accuracy of the threshold for the occurrence of burning cracks is high. Therefore, the average heat transfer coefficient in the above temperature range is identified based on the kinematic viscosity and polymer concentration of the polymer aqueous solution in this way, and it is determined whether or not the polymer aqueous solution can be used continuously by comparing this average heat transfer coefficient with the above threshold value. Therefore, it is possible to further improve the accuracy of determining whether or not the aqueous polymer solution can be used continuously.

A cylindrical test piece of the same quality as the metal material is heated and immersed in a polymer aqueous solution for deriving a threshold value, and the time-dependent changes in temperature of the center, top surface, side surface and bottom surface of the test piece and the aqueous polymer solution are measured. The threshold value may be derived by introducing the target temperature into the following formula (3).
In Equation (3), t is the center of gravity of the upper cylindrical region having a predetermined thickness from the top surface of the test piece, b is the center of gravity of the bottom cylindrical region having the predetermined thickness from the bottom surface, and s is the predetermined thickness from the side surface. A position of half the height of the test piece at a position 1/2 of the predetermined thickness from the side surface of the side cylindrical area of the side, c is a central columnar area surrounded by the top, bottom and sides Is the center of gravity. m _i (i is t, s, b) is the mass [kg] of the top, side, and bottom. A _i is a contact area [m ² ] between the upper part, the side part and the bottom part and the central part. C _px (x is c, t, s, b) is the specific heat [J / kg · K] of the center, top, side, and bottom. l _i is the distance [m] from the center of gravity c to the top, side and bottom surfaces. T _x is a temperature [K] measured by c, t, s, and b, and T _bulk is a temperature [K] of the polymer aqueous solution. h _i is the upper surface, a heat transfer coefficient on the side surface and the bottom surface ^{[W / m 2 · K]} .

  Thus, by measuring the time-dependent changes in the center, top surface, side surface and bottom surface of the test piece and the temperature of the aqueous polymer solution, introducing the time-dependent temperature into the above equation (3) and deriving the above threshold, It is possible to increase the accuracy of the threshold value for the occurrence of the occurrence of water and improve the determination accuracy of the degree of deterioration of the aqueous polymer solution.

  Further, another invention made to solve the above problems includes a step of heating the metal material, a step of cooling the metal material by immersion in the polymer aqueous solution, and a degree of deterioration of the polymer aqueous solution by the method of determining the degree of deterioration. It is a manufacturing method of the metal processing member provided with the process of determining.

  Since the method of manufacturing the metal workpiece includes a step of determining the deterioration degree of the aqueous polymer solution by the deterioration degree determination method, it is easily and accurately determined whether or not the aqueous polymer solution used for the cooling liquid of the heat treatment of the metal material can be continuously used. it can. Thereby, since the manufacturing method of the said metal processing member enables continuous use of the polymer aqueous solution until it becomes a state closer to the state where burning cracks occur, and can increase the use time until the polymer aqueous solution is replaced, The amount of the polymer aqueous solution used can be reduced, and the manufacturing cost of the metal workpiece can be reduced.

  As described above, the degradation degree determination method of the present invention can easily and accurately determine whether or not the polymer aqueous solution used for the cooling liquid for the heat treatment of the metal material can be used continuously. In addition, the method for producing a metal workpiece according to the present invention makes it possible to easily and accurately determine whether or not the polymer aqueous solution used for the cooling liquid for heat treatment of the metal material can be continuously used, and thus increases the use time until the polymer aqueous solution is replaced. be able to.

It is a graph which shows the threshold line which determines the propriety of continuous use of the polymer aqueous solution in the degradation degree determination method of 1st embodiment of this invention. It is a graph which shows the measurement result of the kinematic viscosity of the polymer aqueous solution from which a use period differs. It is a graph which shows the measurement result of kinematic viscosity at the time of diluting the polymer aqueous solution from which a use period differs to the same polymer concentration. It is a graph which shows the relationship between the kinematic viscosity in polymer concentration (alpha), and the average heat transfer coefficient of 200 to 400 degreeC between a metal material and polymer aqueous solution. It is a graph which shows the relationship between the kinematic viscosity in polymer concentration 1.2 (alpha), and the average heat transfer coefficient of 200 to 400 degreeC between a metal material and polymer aqueous solution. It is a graph which shows the relationship between kinematic viscosity in polymer concentration 1.4 (alpha), and the average heat transfer coefficient of 200 to 400 degreeC between a metal material and polymer aqueous solution. It is a typical sectional view of a test material used for derivation of an average heat transfer coefficient. It is a graph which shows the relationship between the temperature on the test material upper surface in polymer concentration (alpha), and the heat transfer rate between a metal material and polymer aqueous solution. It is a graph which shows the relationship between the temperature by the side of a test material in polymer concentration (alpha), and the heat transfer rate between a metal material and polymer aqueous solution. It is a graph which shows the relationship between the temperature in the test material bottom face in polymer concentration (alpha), and the heat transfer rate between a metal material and polymer aqueous solution. It is a graph which shows the relationship between the intercept of the approximate line of kinematic viscosity and the average heat transfer coefficient of 200 to 400 degreeC between a metal material and polymer aqueous solution, and a polymer concentration.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a deterioration degree determination method and a metal workpiece manufacturing method according to the present invention will be described.

[First embodiment]
[Degradation method]
The degradation level determination method is a degradation level determination method for an aqueous polymer solution used as a cooling liquid for heat treatment of a metal material. The degradation degree determination method includes a step of measuring the kinematic viscosity of the polymer aqueous solution (measurement step), a step of acquiring the polymer concentration of the polymer aqueous solution at the time of measuring the kinematic viscosity in the measurement step (acquisition step), and the measurement step. And a step of determining the degree of deterioration of the aqueous polymer solution (determination step) based on the kinematic viscosity obtained in step 1 and the polymer concentration obtained in the acquisition step.

  Examples of the metal material to be subjected to the heat treatment to which the degradation degree determination method is applied include steel, Ni-base alloy, Co-base alloy, aluminum alloy, magnesium alloy, and copper alloy.

  The polymer used in the polymer aqueous solution is not particularly limited as long as it is soluble in water. For example, polyethylene glycol (PEG), polypropylene glycol (PPG), polyalkylene glycol (PAG), and the like can be used.

  The lower limit of the number average molecular weight of the polymer used in the polymer aqueous solution is preferably 4,000, and more preferably 4,500. If the number average molecular weight of the polymer is less than the lower limit, the polymer concentration must be increased in order to obtain the necessary cooling relaxation ability, and the amount of the polymer used increases, which may increase the production cost.

  The lower limit of the polymer concentration of the aqueous polymer solution is preferably 10% by volume, more preferably 15% by volume. On the other hand, the upper limit of the polymer concentration is preferably 60% by volume, more preferably 50% by volume. If the polymer concentration is less than the lower limit, the necessary cooling relaxation ability may not be obtained. Conversely, if the polymer concentration exceeds the upper limit, the required amount of polymer increases, which may increase the manufacturing cost.

  The lower limit of the thermal conductivity of the aqueous polymer solution is preferably 0.40 W / (m · K), more preferably 0.45 W / (m · K). On the other hand, the upper limit of the thermal conductivity of the aqueous polymer solution is preferably 0.65 W / (m · K), more preferably 0.60 W / (m · K). If the thermal conductivity of the aqueous polymer solution is less than the lower limit, the cooling rate of the metal material becomes too slow, and the desired characteristics of the metal material expected by the heat treatment may not be obtained. Conversely, if the thermal conductivity of the polymer aqueous solution exceeds the upper limit, the cooling relaxation effect by the polymer is too small, and the cracking suppression effect may be reduced.

<Measurement process>
In the measurement step, the kinematic viscosity of the aqueous polymer solution is measured using a viscometer. As a viscometer for measuring the kinematic viscosity, for example, an Ubbelohde viscometer or a Cannon Fenceke viscometer can be used.

<Acquisition process>
In the acquisition step, the polymer concentration of the aqueous polymer solution at the time of measuring the kinematic viscosity in the measurement step is measured. This polymer concentration can be easily measured by using, for example, a refractive index densitometer.

<Judgment process>
In the determination step, the degree of deterioration of the aqueous polymer solution is determined based on the kinematic viscosity measured in the measurement step and the polymer concentration measured in the acquisition step.

  Specifically, in the above determination step, a threshold line indicating whether or not the aqueous polymer solution can be used continuously is set in a coordinate system with the kinematic viscosity and the polymer concentration as axes. It is determined that continuous use is possible, and when the kinematic viscosity is below this threshold line, it is determined that the polymer aqueous solution cannot be used continuously.

More specifically, in the determination step, as shown in FIG. 1, for example, the coordinate system is a biaxial orthogonal coordinate system with the kinematic viscosity y and the polymer concentration x as axes, and the threshold line TL is set to y = ax + b (a Is a positive constant and b is a constant). In this determination step, the measured kinematic viscosity and polymer concentration are substituted into this linear function, and in the case of the following formula (1), it is determined that the polymer aqueous solution can be used continuously. In the case of the following formula (2), the polymer aqueous solution Judged that continuous use is not possible.
y> ax + b (1)
y ≦ ax + b (2)

  The threshold line TL can be obtained by using, for example, a polymer aqueous solution that is in a state where burning cracks start to occur due to use deterioration as a polymer aqueous solution for deriving a threshold line. Specifically, after preparing a plurality of polymer aqueous solutions by diluting the polymer aqueous solution for deriving the threshold line so as to have different polymer concentrations and measuring their kinematic viscosities, for example, by the least square method, The threshold line TL can be obtained by first-order approximation of the relationship between the concentration and the kinematic viscosity. Each plot shown in FIG. 1 shows the kinematic viscosity of the polymer aqueous solution for deriving the threshold line, and the kinematic viscosities of the polymer aqueous solution diluted by adding water to a plurality of polymer concentrations. The kinematic viscosity with respect to is shown. From these plots, the threshold line TL can be obtained as described above.

  Here, the reason why the degree of deterioration of the aqueous polymer solution can be determined based on the kinematic viscosity and the polymer concentration will be described, but the inventors adopt the kinematic viscosity and the polymer concentration as a management index for determining whether or not the aqueous polymer solution can be used continuously. Before finding what could be done, we examined whether other physical properties could be adopted as the management index. Specifically, the inventors first examined the molecular weight, and as a result, it was found that it is difficult to use the molecular weight as the management index because of the large variation in each measurement and the variation depending on the measurement location. Next, the present inventors examined each of the thermal conductivity and kinematic viscosity of the aqueous polymer solution, but none of them was correlated with the deterioration of the aqueous polymer solution, and these were also difficult to use as the management index. I found out that Next, the inventors examined the combination of kinematic viscosity and polymer concentration.

  The inventors first measured the kinematic viscosity of the polymer aqueous solutions having different use times shown in Table 1, and the results as shown in FIG. 2 were obtained. The new liquid A in Table 1 is a polymer aqueous solution before being used for heat treatment, and the operating liquids B to E are a plurality of polymer aqueous solutions in use. Each operation liquid B to E has a long use time in this order. In Table 1, the polymer concentration of the polymer aqueous solution is shown as a concentration ratio. This concentration ratio is the ratio of the polymer concentration of each of the operating liquids B to E to the polymer concentration of the new liquid A (the polymer concentration of the operating liquid [volume%] / the polymer concentration of the new liquid A [volume%]). Since the polymer aqueous solution in use is used while adding the new solution A in order to suppress deterioration, the polymer concentration increases as the period of use increases.

  FIG. 2 shows that the kinematic viscosity is higher as the polymer aqueous solution is considered to have a longer period of use and the deterioration is progressing. “High kinematic viscosity” is usually predicted to be “low heat transfer coefficient”, and is considered to be “hard to cause cracking”. However, FIG. 2 shows the opposite result. Accordingly, the kinematic viscosity cannot be used as a management index for the degree of deterioration of the aqueous polymer solution.

  Therefore, the inventors diluted each operating liquid B to E with water so that the polymer concentration was the same as the polymer concentration α of the new liquid A, and measured the kinematic viscosity of each operating liquid B to E with the same polymer concentration α. did. The measurement results are shown in FIG. FIG. 3 shows that the kinematic viscosity is lower as the polymer aqueous solution is considered to be more deteriorated. This is thought to be because the molecular weight of the polymer aqueous solution that has been deteriorated is lowered. From this, it can be seen that the kinematic viscosity at a predetermined concentration can be used as a management index for determining whether or not the polymer aqueous solution can be used continuously. Accordingly, the kinematic viscosity that becomes the threshold for determining whether or not the aqueous polymer solution can be used continuously is determined for each polymer concentration. Therefore, by using the polymer aqueous solution for deriving the threshold line as described above, the kinematic viscosity corresponding to the polymer concentration is determined. The threshold line TL indicating the threshold is obtained. Thereby, it is possible to determine whether or not the polymer aqueous solution can be continuously used from the kinematic viscosity and the polymer concentration using the threshold line TL.

  The degradation level is determined by the simple use of measuring the polymer concentration and kinematic viscosity of the aqueous polymer solution without immersing the test material in the aqueous polymer solution and measuring the cooling temperature. Whether it is possible can be determined. Moreover, since the degradation degree determination method can determine whether or not the aqueous polymer solution can be used continuously by comparing the measured polymer concentration and kinematic viscosity with the threshold line TL, it is easy to determine the degradation level of the aqueous polymer solution.

[Method of manufacturing metal-worked member]
The manufacturing method of the metal workpiece includes a step of heating a metal material (heating step), a step of cooling the metal material by immersion in a polymer aqueous solution (cooling step), and a deterioration of the polymer aqueous solution by the deterioration degree determination method. And a step of determining the degree (degradation degree determination step).

  The heating step and the cooling step are steps for heating and cooling in a heat treatment such as a quenching treatment and a tempering treatment for the metal material. For example, when manufacturing high-strength steel for forged steel used for a crankshaft or the like as a metal processed member, in addition to the above steps, a melting step, a casting step, a forging step, and the like are provided. Furthermore, by processing the high-strength steel for forged steel manufactured in this way by a machining process, for example, an intermediate shaft, a propulsion shaft, a connecting rod, a ladder stock, a ladder horn, used as a transmission member for a marine drive source, Crankshafts etc. are manufactured.

<Heating process>
In the heating step, the metal material is heated at a predetermined temperature for a predetermined time. For example, in the heating process in the quenching process of high-strength steel for forged steel products, the steel material cooled in the pre-quenching process is heated to about 800 ° C. or higher and about 950 ° C. or lower and held for 1 hour or longer.

<Cooling process>
In the cooling step, the metal material heated in the heating step is cooled to a predetermined temperature by immersing it in the polymer aqueous solution. For example, in the cooling process in the quenching treatment of high strength steel for forged steel products, the steel material heated in the heating process is immersed in an aqueous polymer solution, and is cooled to, for example, about 450 ° C. or more and 530 ° C. or less at an average cooling rate of about 50 ° C./min.

<Deterioration degree determination process>
In the deterioration degree determination step, the polymer concentration and kinematic viscosity of the aqueous polymer solution are measured, and whether or not the aqueous polymer solution can be continuously used is determined by the above deterioration degree determination method. For example, when the coordinate system of FIG. 1 is used as the deterioration degree determination method, in the deterioration degree determination step, when the measured polymer concentration x and kinematic viscosity y satisfy the above formula (1), the polymer aqueous solution is continuously used. When the formula (2) is satisfied, it is determined that the polymer aqueous solution cannot be used continuously, and is replaced with a new polymer aqueous solution.

  Note that the deterioration degree determination step may be performed every time the metal material is cooled, or when it is expected that the metal material can be cooled a predetermined number of times without burning cracks, the cooling process is performed a predetermined number of times. It may be performed only later.

  Thus, since the manufacturing method of the said metal processing member is equipped with the process of determining the deterioration degree of polymer aqueous solution by the said deterioration degree determination method, it is easy to determine the continuation use of the polymer aqueous solution used for the cooling liquid of the heat processing of a metal material, and The polymer aqueous solution can be used continuously until it can be judged with high accuracy and becomes closer to a state where burning cracks are generated. Thereby, since the use time until replacement | exchange of polymer aqueous solution can be lengthened, the usage-amount of polymer aqueous solution can be reduced and the manufacturing cost of a metal material can be reduced.

[Second Embodiment]
[Degradation method]
The degradation degree determination method includes a step of diluting the polymer aqueous solution to a specific concentration (dilution step), a step of measuring the kinematic viscosity of the polymer aqueous solution after the dilution step (measurement step), and a kinematic viscosity measurement in the measurement step. A step of acquiring the polymer concentration of the aqueous polymer solution (acquisition step), and a step of determining the degree of deterioration of the aqueous polymer solution based on the kinematic viscosity obtained in the measurement step and the polymer concentration obtained in the acquisition step (determination step). Prepare. Specifically, the acquisition step employs a specific concentration after the dilution step as the polymer concentration of the aqueous polymer solution.

<Dilution process>
In the dilution step, water is added to the polymer aqueous solution to dilute to a specific concentration. Specifically, in the dilution step, for example, the polymer concentration of the aqueous polymer solution is measured, the amount of water added to dilute from the polymer concentration to a specific concentration is calculated, and the calculated amount of water is added to the aqueous polymer solution. Added.

  Here, since the polymer aqueous solution is used by appropriately adding a new solution of the polymer aqueous solution in order to suppress deterioration, the polymer concentration of the polymer aqueous solution in use increases with time. Therefore, the specific concentration may be a polymer concentration lower than that of the polymer aqueous solution in use, and can be, for example, the polymer concentration of a new solution of the polymer aqueous solution.

<Measurement process>
In the measurement step, the kinematic viscosity of the aqueous polymer solution diluted to a specific concentration after the dilution step is measured using a viscometer.

<Acquisition process>
In the acquisition step, the specific concentration after the dilution step is adopted as the polymer concentration of the aqueous polymer solution. That is, in the acquisition step, the specific concentration is acquired as the polymer concentration of the aqueous polymer solution.

<Judgment process>
In the determination step, the degree of deterioration of the aqueous polymer solution is determined based on the kinematic viscosity at the specific concentration acquired in the acquisition step, that is, the kinematic viscosity measured in the measurement step. Specifically, in the determination step, the measured kinematic viscosity is compared with a threshold value, and when the measured kinematic viscosity is larger than the threshold value, it is determined that the polymer aqueous solution can be continuously used.

The threshold value of the kinematic viscosity is obtained as follows. That is, as shown in FIG. 1, the threshold line TL is expressed as a linear function in a biaxial orthogonal coordinate system with the kinematic viscosity y and the polymer concentration x as axes. Therefore, the threshold value of the kinematic viscosity for the specific concentration is obtained from the threshold line TL. For example, in FIG. 1, when the specific concentration is 25% by volume, the threshold value of kinematic viscosity is obtained as 6 mm ² / s.

  As described above, since the degradation degree determination method can determine whether or not the aqueous polymer solution can be used continuously based on only the kinematic viscosity by diluting the aqueous polymer solution to a specific concentration, the degradation level of the aqueous polymer solution can be more easily determined. .

[Third embodiment]
[Degradation method]
The degradation degree determination method includes a step of diluting the polymer aqueous solution to a specific concentration (dilution step), a step of measuring the kinematic viscosity of the polymer aqueous solution after the dilution step (measurement step), and a kinematic viscosity measurement in the measurement step. A step of acquiring the polymer concentration of the aqueous polymer solution (acquisition step), and a step of determining the degree of deterioration of the aqueous polymer solution based on the kinematic viscosity obtained in the measurement step and the polymer concentration obtained in the acquisition step (determination step). Prepare. The determination step is a step of identifying an average heat transfer coefficient between 200 ° C. and 400 ° C. between the metal material and the polymer aqueous solution based on the kinematic viscosity obtained in the measurement step and the polymer concentration obtained in the acquisition step (identification step), A step (determination step) for determining that the aqueous polymer solution can be continuously used when the average heat transfer coefficient obtained in the identification step is smaller than the threshold value.

  The deterioration degree determination method is different from the deterioration degree determination method of the second embodiment in that the determination step includes an identification step and a determination step, and whether or not the aqueous polymer solution can be continuously used is determined based on the average heat transfer coefficient. Below, the determination process different from said 2nd embodiment is demonstrated.

<Judgment process>
As described above, the determination process includes an identification process and a determination process. Here, the specific concentration is defined as a polymer concentration α. Therefore, in the determination step, the kinematic viscosity of the polymer aqueous solution diluted to the polymer concentration α is acquired from the measurement step, and information on the polymer concentration α is acquired from the acquisition step.

(Identification process)
In the identification step, an average heat transfer coefficient between 200 ° C. and 400 ° C. between the metal material and the polymer aqueous solution is identified based on the kinematic viscosity of the polymer aqueous solution diluted to the polymer concentration α and the polymer concentration α. This identification method will be specifically described below.

As will be described later, the inventors have found that there is a correlation between the kinematic viscosity and the average heat transfer coefficient between 200 ° C. and 400 ° C. between the metal material and the polymer aqueous solution with respect to the polymer concentration of the polymer aqueous solution. It was. Here, FIG. 4 shows the relationship between the kinematic viscosity and the average heat transfer coefficient in a polymer aqueous solution having a polymer concentration α. FIG. 4 shows the measured value of the kinematic viscosity of the polymer aqueous solution after dilution with water so that each of a plurality of polymer aqueous solutions has a polymer concentration α and the calculated value of the average heat transfer coefficient. It is. First correlation line CL ₁ of FIG. 4 is a straight line first approximation the relation kinematic viscosity and the average heat transfer coefficient. In the identification step, using the first correlation line CL ₁ indicating the correlation between the kinematic viscosity and the average heat transfer coefficient, the kinematic viscosity obtained in the measurement step is between 200 ° C. and 400 ° C. between the metal material and the polymer aqueous solution. Identify the average heat transfer coefficient.

FIG. 5 shows the relationship between the kinematic viscosity and the average heat transfer coefficient in a polymer aqueous solution having a polymer concentration of 1.2α that is 1.2 times the polymer concentration α obtained based on the diluted polymer aqueous solution in the same manner as in FIG. It is shown. Similarly, FIG. 6 shows the relationship between the kinematic viscosity and the average heat transfer coefficient in a polymer aqueous solution having a polymer concentration of 1.4α that is 1.4 times the polymer concentration α. FIG third correlation line CL ₃ of the second correlation line CL ₂ and 6 5, the relationship between the kinematic viscosity and the average heat transfer coefficient in each polymer concentration 1.2α and polymer concentration 1.4α in straight lines first approximation is there. As shown in FIGS. 4 to 6, it can be seen that the average heat transfer coefficient correlates with kinematic viscosity at any polymer concentration.

(Judgment process)
In the determination step, it is determined that the polymer aqueous solution can be used continuously when the average heat transfer coefficient obtained in the identification step is smaller than the threshold value. This determination method will be specifically described below.

The first threshold value P ₁ in FIG. 4 shows the kinematic viscosity and 200 ° C. or higher 400 ° C. or less of the average heat transfer coefficient in the polymer aqueous solution obtained by diluting the polymer solution for the threshold derived polymer concentration alpha. In the determination step, the average heat transfer coefficient (first threshold value P ₁ ) of the aqueous polymer solution for deriving the threshold is used as a threshold for determining whether or not the aqueous polymer solution can be used continuously, and the average heat transfer coefficient obtained in the identification step is If the first threshold value P ₁ is smaller than, determines that sustainable use of aqueous polymer solution. Here, since the temperature range of 200 ° C. or more and 400 ° C. or less is a temperature range where burning cracks are generated based on an empirical rule, the first threshold value P ₁ indicating the average heat transfer coefficient of 200 ° C. or more and 400 ° C. or less is the occurrence of burning cracks. High accuracy. Since the determination step uses this highly accurate threshold value, the determination accuracy of whether or not the polymer aqueous solution can be continuously used is high.

The third threshold value P ₃ of the second threshold value P ₂ and 6 in FIG. 5, and kinematic viscosity respectively aqueous polymer solution for the threshold derivation in the polymer solution was diluted to a polymer concentration 1.2α and polymer concentration 1.4α The average heat transfer coefficient of 200 ° C. or higher and 400 ° C. or lower is shown. When the kinematic viscosity of the polymer aqueous solution diluted to the polymer concentration of 1.2α or the polymer concentration of 1.4α is measured in the measurement step, the determination step uses the second threshold value P ₂ or the third threshold value P ₃ to determine the polymer. Determine whether the aqueous solution can be used continuously.

(Derivation method of threshold value for average heat transfer coefficient)
The threshold value of the average heat transfer coefficient is obtained by, for example, heating a test piece of the same quality as the above metal material and immersing it in a polymer aqueous solution for deriving the threshold value, and changing the temperature of the center, top, side and bottom surfaces of the test piece and the temperature of the aqueous polymer solution Can be derived by measuring the time course temperature and introducing the temperature over time into the following equation (3).
In Equation (3), t is the center of gravity of the upper cylindrical region having a predetermined thickness from the top surface of the test piece, b is the center of gravity of the bottom cylindrical region having the predetermined thickness from the bottom surface, and s is the predetermined thickness from the side surface. A position of half the height of the test piece at a position 1/2 of the predetermined thickness from the side surface of the side cylindrical area of the side, c is a central columnar area surrounded by the top, bottom and sides Is the center of gravity. m _i (i is t, s, b) is the mass [kg] of the top, side, and bottom. A _i is a contact area [m ² ] between the upper part, the side part and the bottom part and the central part. C _px (x is c, t, s, b) is the specific heat [J / kg · K] of the center, top, side, and bottom. l _i is the distance [m] from the center of gravity c to the top, side and bottom surfaces. T _x is a temperature [K] measured by c, t, s, and b, and T _bulk is a temperature [K] of the polymer aqueous solution. h _i is the upper surface, a heat transfer coefficient on the side surface and the bottom surface ^{[W / m 2 · K]} .

  As a minimum of the diameter of the above-mentioned specimen, 10 mm is preferred and 15 mm is more preferred. On the other hand, as an upper limit of the diameter of a test piece, 40 mm is preferable and 30 mm is more preferable. If the diameter of the test piece is less than the above lower limit, the temperature difference between the center and the outer periphery of the test material becomes too small, and the accuracy of the derived average heat transfer coefficient may be lowered. Conversely, if the diameter of the test piece exceeds the above upper limit, the facility for deriving the average heat transfer coefficient may be unnecessarily large.

  As a minimum of the height of the above-mentioned test piece, 30 mm is preferred and 40 mm is more preferred. On the other hand, as an upper limit of the height of a test piece, 120 mm is preferable and 100 mm is more preferable. When the height of the test piece is less than the above lower limit, the temperature difference between the center of the test material and the upper surface and the lower surface becomes too small, and the accuracy of the derived average heat transfer coefficient may be lowered. On the other hand, if the height of the test piece exceeds the above upper limit, the amount of movement for immersing the test piece in the polymer aqueous solution increases, which may increase the cost of the derivation equipment.

  The lower limit of the predetermined thickness from the surface of the test material for dividing into virtual regions is preferably 1 mm, and more preferably 2 mm. On the other hand, the upper limit of the predetermined thickness from the surface of the test material is preferably 5 mm, and more preferably 4 mm. If the predetermined thickness from the surface of the test material is less than the lower limit, it is difficult to set the thermocouple at an accurate position, and the accuracy of the calculated heat transfer coefficient may be reduced. On the other hand, if the predetermined thickness from the surface of the test material exceeds the upper limit, the difference between the calculated heat transfer coefficient and the heat transfer coefficient at the surface increases, and the accuracy of the calculated heat transfer coefficient decreases. There is a risk.

  Note that the derivation of the threshold value does not need to be performed every time the metal material is cooled, and may be performed once for each type of metal material.

  Next, a derivation method performed by the inventors will be described as a specific example of the threshold derivation method.

  The threshold value is derived by immersing a heated cylindrical test material in a polymer aqueous solution, measuring the temperature change of the test material over time, and calculating the heat transfer coefficient between the metal material and the polymer aqueous solution from the temperature change. went. Specifically, a round bar having a diameter of 20 mm and a height of 60 mm (“Inconel 600” manufactured by Special Metals) was used. Moreover, each polymer aqueous solution shown in Table 1 was used as polymer aqueous solution.

This test material was divided into virtual regions with a thickness of 3 mm from the surface, and the heat transfer coefficient was calculated for each divided region. Specifically, in the schematic cross-sectional view passing through the axis of the test material of FIG. 7, a cylindrical region having a thickness of 3 mm from the top surface is an upper portion R _t , a cylindrical region having a thickness of 3 mm from the bottom surface is a bottom portion R _b , and an outer peripheral side surface. A cylindrical region having a thickness of 3 mm was defined as a central region R _c and a cylindrical region surrounded by the side portion R _s , the upper portion R _t , the bottom portion R _b, and R _s . The center of gravity of the upper _{R t} t, the center of gravity of the bottom _{R b} b, the center of gravity of the central portion _{R c} c, the position of height 30mm at a position 1.5mm from the outer peripheral surface of the side portion _{R s} and s, these Thermocouples were installed at positions t, b, s, and c.

  Next, the test material was heated to 900 ° C. and immersed in a beaker containing a polymer aqueous solution, and the temperature change of each part of the test material and the temperature change of the polymer aqueous solution were measured. Here, the temperature of the polymer aqueous solution when the test material was immersed was set to 50 ° C. by hot water bath.

Since the change in the amount of heat of the side portion R _s , the upper portion R _t and the bottom portion R _b is determined by the amount of heat released to the polymer aqueous solution and the amount of heat input from the central portion R _c , The temperature change with time of each part measured above was introduced, and each heat transfer coefficient h _i between the polymer aqueous solution and the side part R _s , the upper part R _t and the bottom part R _b was calculated.

Although a temperature range from heuristics quenching crack occurs at 200 ° C. or higher 400 ° C. or less, a result of calculating each of the above heat transfer coefficient h _i, significant difference in the cooling characteristics of each polymer solution at this temperature range is not observed It was.

Next, each of the operating liquids B to E is diluted by adding water so that the same polymer concentration α as that of the new liquid A is obtained. By the same method as described above, the aqueous polymer solution, the side portions R _s , the upper portion R _t and it was calculated each heat transfer coefficient h _i between the bottom R _b. As a result, as shown in FIG. 8 to FIG. 10, it was confirmed that in the temperature range of 200 ° C. or more and 400 ° C. or less, the heat transfer rate increases as the use time increases and the deterioration progresses.

Next, with respect to the polymer concentration α of the new solution A, each of the operation liquids B to E is diluted so that the polymer concentration becomes α, 1.2α, and 1.4α, and a polymer aqueous solution is obtained by the same method as described above. the side _{R s,} were calculated the heat transfer coefficient _{h i} between the top _{R t} and bottom _{R b.} 4 to 6 are graphs showing the relationship between the kinematic viscosity for each polymer concentration and the average heat transfer coefficient of 200 ° C. or higher and 400 ° C. or lower using this calculation result. 4 to 6, it can be seen that there is a correlation between the kinematic viscosity and the average heat transfer coefficient of 200 ° C. or more and 400 ° C. or less at a predetermined concentration. Therefore, if the kinematic viscosity and the polymer concentration are known, an average heat transfer coefficient of 200 ° C. or higher and 400 ° C. or lower can be identified.

  4 to 6, it can be seen that the slopes when the correlation between the kinematic viscosity and the average heat transfer coefficient of 200 ° C. or more and 400 ° C. or less is approximated by a linear expression are substantially equal. FIG. 11 shows the relationship between the intercept of these linear equations and the polymer concentration, and it can be seen that the value of the intercept correlates with the polymer concentration. Therefore, from FIG. 11, a linear equation showing the correlation between the kinematic viscosity at an arbitrary polymer concentration and the average heat transfer coefficient of 200 ° C. or more and 400 ° C. or less can be obtained. Thereby, about the polymer aqueous solution of arbitrary polymer density | concentrations, an average heat transfer rate of 200 to 400 degreeC can be identified by measuring kinematic viscosity.

  In the above determination step, it was determined whether or not the polymer aqueous solution could be used continuously based on the kinematic viscosity and polymer concentration of the polymer aqueous solution after dilution to the polymer concentration α, but the kinematic viscosity and polymer concentration of the polymer aqueous solution before dilution were determined. Based on this, it may be determined whether the polymer aqueous solution can be used continuously. In this case, the dilution step can be omitted in the deterioration degree determination method.

[Other Embodiments]
The degradation degree determination method and the metal workpiece manufacturing method are not limited to the above embodiment.

  That is, in the first embodiment, a biaxial orthogonal coordinate system with kinematic viscosity and polymer concentration as axes is used as a coordinate system for setting a threshold line indicating whether or not the aqueous polymer solution can be used continuously. A coordinate system other than the orthogonal coordinate system may be used. For example, a coordinate system having three or more axes may be used by adding other parameters.

  In the second embodiment, in order to dilute the polymer aqueous solution, the polymer concentration of the polymer aqueous solution is first measured, and the amount of water calculated to dilute from the polymer concentration to a specific concentration is added. For example, dilution may be performed without measuring the polymer concentration of the aqueous polymer solution before dilution. That is, the polymer concentration may be measured while adding water to the polymer aqueous solution, and the addition of water may be stopped when the polymer concentration is reduced to a specific concentration.

  In the first embodiment, whether or not the aqueous polymer solution can be continuously used is determined based on the kinematic viscosity with respect to the polymer concentration using a threshold line set in a coordinate system with the kinematic viscosity and the polymer concentration as axes. On the other hand, in the third embodiment, the average heat transfer coefficient between 200 ° C. and 400 ° C. between the metal material and the polymer aqueous solution is identified, and it is determined whether or not the polymer aqueous solution can be continuously used based on the average heat transfer coefficient. It is also possible to determine whether or not the aqueous polymer solution can be used continuously by combining both of these determinations. That is, whether or not the polymer aqueous solution can be continuously used may be determined based on both the kinematic viscosity and the average heat transfer coefficient. By doing in this way, it can be judged more accurately whether the polymer aqueous solution can be used continuously.

  As described above, the degradation degree determination method and the metal workpiece manufacturing method of the present invention can easily and accurately determine whether or not the aqueous polymer solution used for the cooling liquid for the heat treatment of the metal material can be used. It can be suitably used for the production of metal materials using a polymer aqueous solution as the liquid.

b Center of gravity of the bottom cylindrical region of the test piece c Center of gravity of the central cylindrical region surrounded by the top, bottom and sides of the test piece t Center of gravity of the cylindrical region of the test piece s Side of the cylindrical region of the side of the test piece predetermined thickness test piece at the position of half the height of the half position R _b bottom R _c central R _t top R _s side TL threshold line CL ₁ first correlation line CL ₂ second correlation from Line CL ₃ 3rd correlation line P ₁ 1st threshold value P ₂ 2nd threshold value P ₃ 3rd threshold value

Claims (9)

A method for determining the degree of deterioration of an aqueous polymer solution used as a cooling liquid for heat treatment of a metal material,
Measuring the kinematic viscosity of the aqueous polymer solution;
A step of obtaining the polymer concentration of the aqueous polymer solution at the time of measuring the kinematic viscosity in the measurement step;
A step of determining the degree of deterioration of the aqueous polymer solution based on the kinematic viscosity obtained in the measurement step and the polymer concentration obtained in the acquisition step, and
In the determination step, a threshold line indicating whether or not the polymer aqueous solution can be used continuously is set in the coordinate system with the kinematic viscosity and the polymer concentration as axes, and the polymer aqueous solution can be used continuously when the kinematic viscosity is larger than the threshold line. deterioration degree determination method characterized by determining the. The coordinate system is a biaxial orthogonal coordinate system with kinematic viscosity y [mm ² / s] and polymer concentration x [volume%] as axes, and the threshold line is y = ax + b (a is a positive constant, b is a constant) And a linear function
The deterioration determination method according to claim 1 , wherein in the determination step, it is determined that the aqueous polymer solution can be used continuously in the case of the following formula (1), and the continuous use of the aqueous polymer solution is determined in the case of the following formula (2). .
y> ax + b (1)
y ≦ ax + b (2) The degradation determination method according to claim 1 or 2 , wherein in the acquisition step, the polymer concentration of the aqueous polymer solution at the time of measuring the kinematic viscosity in the measurement step is measured. A method for determining the degree of deterioration of an aqueous polymer solution used as a cooling liquid for heat treatment of a metal material,
Measuring the kinematic viscosity of the aqueous polymer solution;
A step of obtaining the polymer concentration of the aqueous polymer solution at the time of measuring the kinematic viscosity in the measurement step;
Determining the degree of deterioration of the aqueous polymer solution based on the kinematic viscosity obtained in the measurement step and the polymer concentration obtained in the acquisition step;
With
Further comprising a step of diluting the aqueous polymer solution to a specific concentration before the measurement step,
Measure the kinematic viscosity of the aqueous polymer solution after the dilution step in the measurement step,
A deterioration degree determination method, wherein a specific concentration after the dilution step is adopted as the polymer concentration acquired in the acquisition step. In the determination step, a threshold line indicating whether or not the polymer aqueous solution can be used continuously is set in the coordinate system with the kinematic viscosity and the polymer concentration as axes, and the polymer aqueous solution can be used continuously when the kinematic viscosity is larger than the threshold line. The deterioration degree determination method according to claim 4, wherein the deterioration degree determination method is determined. The above coordinate system is kinematic viscosity y [mm ² / S] and polymer concentration x [volume%] as axes, and the threshold line is a linear function of y = ax + b (a is a positive constant, b is a constant),
6. The deterioration degree determination method according to claim 5, wherein in the determination step, it is determined that the aqueous polymer solution can be used continuously in the case of the following formula (1), and the continuous use of the aqueous polymer solution is determined in the case of the following formula (2). .
y> ax + b (1)
y ≦ ax + b (2) A method for determining the degree of deterioration of an aqueous polymer solution used as a cooling liquid for heat treatment of a metal material,
Measuring the kinematic viscosity of the aqueous polymer solution;
A step of obtaining the polymer concentration of the aqueous polymer solution at the time of measuring the kinematic viscosity in the measurement step;
Determining the degree of deterioration of the aqueous polymer solution based on the kinematic viscosity obtained in the measurement step and the polymer concentration obtained in the acquisition step;
With
The determination step is
Identifying the average heat transfer coefficient between 200 ° C. and 400 ° C. between the metal material and the aqueous polymer solution based on the kinematic viscosity obtained in the measurement step and the polymer concentration obtained in the acquisition step;
A step of determining that the aqueous polymer solution can be used continuously when the average heat transfer coefficient obtained in the identification step is smaller than a threshold;
A degradation degree determination method characterized by comprising: A cylindrical test piece of the same quality as the metal material is heated and immersed in a polymer aqueous solution for deriving a threshold value, and the time-dependent changes in temperature of the center, top surface, side surface and bottom surface of the test piece and the aqueous polymer solution are measured. The method for determining the degree of deterioration of an aqueous polymer solution according to claim 7 , wherein the threshold value is derived by introducing a target temperature into the following formula (3).
In Equation (3), t is the center of gravity of the upper cylindrical region having a predetermined thickness from the top surface of the test piece, b is the center of gravity of the bottom cylindrical region having the predetermined thickness from the bottom surface, and s is the predetermined thickness from the side surface. A position of half the height of the test piece at a position 1/2 of the predetermined thickness from the side surface of the side cylindrical area of the side, c is a central columnar area surrounded by the top, bottom and sides Is the center of gravity. m _i (i is t, s, b) is the mass [kg] of the top, side, and bottom. A _i is a contact area [m ² ] between the upper part, the side part and the bottom part and the central part. C _px (x is c, t, s, b) is the specific heat [J / kg · K] of the center, top, side, and bottom. l _i is the distance [m] from the center of gravity c to the top, side and bottom surfaces. T _x is a temperature [K] measured by c, t, s, and b, and T _bulk is a temperature [K] of the polymer aqueous solution. h _i is the upper surface, a heat transfer coefficient on the side surface and the bottom surface ^{[W / m 2 · K]} . Heating the metal material;
Cooling the metal material by immersion in an aqueous polymer solution;
A method for producing a metal workpiece, comprising: a step of determining a degree of deterioration of an aqueous polymer solution by the method for determining a degree of deterioration according to any one of claims 1 to 8 .