JP4934005B2 - Method for evaluating forging lubricant and mold material, and apparatus for evaluating the same - Google Patents

Description

  The present invention relates to a forging lubricant, a method for evaluating a mold material, and an evaluation apparatus therefor.

The lubricant used for forging is an extremely important factor for reducing the coefficient of friction between the workpiece and the mold and preventing premature seizure due to direct contact between the workpiece and the mold. For this reason, it is necessary to select an optimum lubricant from various lubricants according to molding conditions and workpiece materials.
As a method for evaluating the lubricity of a lubricant assuming an actual forging form, there are a ring compression test method, an evaluation method corresponding to the forward extrusion method, an evaluation method corresponding to the backward extrusion method, etc. Various proposals have been made.

As an evaluation method corresponding to the forward extrusion method, for example, a method of measuring the indentation load when a constant indentation amount is given to a workpiece coated with a lubricant and evaluating the lubricity of the applied lubricant is known. (See Patent Document 1). Further, as an evaluation method corresponding to the backward extrusion method, for example, the indentation load and the pull-out load when a constant indentation amount is given to the workpiece coated with the lubricant are measured, and the lubricity of the applied lubricant is evaluated. A method is known (see Patent Document 2).
However, these methods are suitable for evaluating the lubricity of the lubricant itself, but actual forging is often performed continuously, and it is necessary to evaluate the lubricity of the lubricant in such continuous forging. . In addition, in order to evaluate the mold material used for forging, it is necessary to repeatedly perform forging until the damage to the mold occurs, and it takes time and labor for one forging, and the work becomes disposable. Therefore, there is a problem that it becomes an expensive evaluation method.

  An evaluation method called the Timken test is a method in which the rotating ring-shaped mold material is brought into sliding contact with a heated flat workpiece, the lubricant is continuously sprayed on the mold material, and the lubricity of the lubricant is measured by measuring the friction coefficient. It is evaluated (see Patent Document 3). This evaluation method is suitable for evaluating the pure frictional characteristics of lubricants over a wide temperature range, but it is suitable for lubricant followability and resistance to local impact force due to surface area expansion during actual forging. There is a problem that it cannot be evaluated in consideration of

On the other hand, the mold used for forging has a long life depending on the mold material type, and it is necessary to select a mold material according to the forging conditions. In addition to the wear resistance of simple mold materials, mold life is complicatedly related to factors such as the occurrence of thermal shock due to frictional heat and forging energy, resistance to local impact loads, and compatibility with lubricants. Therefore, it is necessary to evaluate by a method close to the actual forging form.
However, there is a problem in that there is no evaluation method and evaluation apparatus for evaluating the forging die material by a method close to this actual forging mode.
JP 2001-286967 A JP 2004-012296 A JP 2005-343948 A

  The present invention has been made in order to address the above-described problems, and has a highly reproducible lubrication evaluation method and operation of a forging lubricant that is close to an actual forging form and has a wide temperature range from cold to hot. It is an object of the present invention to provide an evaluation device that can evaluate the durability of a forging die material at low cost without taking the labor of a worker.

  The lubrication evaluation method for forging lubricant and the material evaluation method for forging die material according to the present invention include a step of feeding a long prismatic workpiece by intermittent linear motion, and a vertical movement above the workpiece when the workpiece stops linear motion. A step of pushing a punch made of a forging die material coated with the lubricant into the workpiece and forming a recess, and a step of pulling out the punch pressed into the recess; The lubrication evaluation of the lubricant is carried out by measuring at least one of the indentation load in the step of forming the depression and the extraction load in the extraction process, and the two steps of forming the depression and drawing out are repeated. It is characterized by evaluating the material of the die material for forging.

  Before the step of forming the depression, the workpiece is heated to a forging temperature. Further, the means for heating the workpiece is a high-frequency induction heating furnace or an infrared heating furnace.

The forging lubricant is sprayed onto the punch at an arbitrarily set spraying amount, spraying time, and spraying timing after the punch pushing-out process.
Further, the forging die material is evaluated using water as the forging lubricant.

The forging die punch is characterized by having a thermocouple embedded in the tip.
Further, the forging die material punch is characterized in that a tip portion is tapered. In particular, the taper shape has a taper angle of 50 ° to 80 °.

The long prismatic workpiece is characterized in that a lubricant film treatment is performed on a recess forming portion in the step of forming the recess.
Further, in the step of forming the depression, it has means for restraining the prismatic workpiece in a direction perpendicular to the direction of feeding the workpiece.

  The forging lubricant and die material evaluation apparatus of the present invention is an apparatus for evaluating the lubricity of the forging lubricant and the material of the forging die material, and means for feeding a long prismatic workpiece by intermittent linear motion And a means for forming a recess by pressing a punch made of a forging die material coated with a forging lubricant into the workpiece so that the workpiece can be moved up and down when the linear motion is stopped. And a means for pulling out the punch made of the mold material and a means for repeatedly feeding out the test workpiece and forming the recess.

  The lubrication evaluation method for forging lubricant and the material evaluation method for forging die material of the present invention are made of a forging die material to which a forging lubricant is applied while feeding a long prismatic workpiece in an intermittent linear motion. Since the lubricity of the forging lubricant is evaluated by measuring the indentation load when forming the indentation in the test workpiece using a punch, it is an evaluation form close to the actual forging form, but from cold The lubricity of a forging lubricant can be evaluated in a wide temperature range up to hot. At the same time, it is possible to evaluate the durability of the die material for forging at low cost without taking the labor of the operator.

  The forging lubricant and forging die material evaluation apparatus of the present invention includes a means for feeding a long prismatic workpiece in an intermittent linear motion, and the workpiece is disposed so as to be movable up and down above the workpiece when the linear motion is stopped. A forging die material punch coated with a lubricant for use, and a means for forming a recess; a means for extracting the mold material punch that has been pressed through the recess; and feeding a test workpiece and forming a recess Therefore, the lubricity of the forging lubricant can be evaluated in a wide temperature range from cold to hot in an evaluation form close to the actual forging form. At the same time, it is possible to evaluate the durability of the forging die material at a low cost without taking the labor of the operator.

  Since the means for heating the workpiece is a high-frequency induction heating furnace or an infrared heating furnace, it is possible to heat the workpiece uniformly and rapidly without contact with the workpiece, and to make the device cheaper and more compact than other heating devices. it can.

  Since the forging lubricant is sprayed onto the punch at an arbitrarily set spraying amount, spraying time and spraying timing after the punch pushing-out process, the lubricant supply amount and the supply frequency are optimized. Conditions can be considered. In addition, by evaluating the material of the forging die material using water as the forging lubricant, it is possible to set the lubrication conditions more severely than when using a normal lubricant. The type can be evaluated.

  Since the forging die material punch has a thermocouple embedded in the tip, it is possible to observe a temperature change due to sliding heat generation or cooling of a portion where the punch slides with the highest stress, and this thermocouple. By setting the temperature condition at, a more precise mold material evaluation becomes possible. In addition, since the tip of the punch has a tapered shape, the tip edge portion that is generally used has a higher stress on the tapered surface when sliding compared to a punch having an R shape, and relative to the plastic flow of the workpiece. The effective sliding distance becomes longer (the surface area enlargement ratio becomes larger) and damage such as wear is likely to occur. Therefore, more severe conditions can be set, which is effective as a means for evaluating the mold material in a short period of time. In addition, since the taper angle of the punch is not less than 50 ° and not more than 80 °, it is possible to evaluate the mold material under the condition with the highest load as described above.

An example of an evaluation apparatus used in the evaluation method of the present invention is shown in FIG. FIG. 1A is a schematic diagram of the evaluation apparatus, and FIG. 1B is a work plan view of a punch pushing-in part.
The evaluation device is composed of a workpiece feeding device 10a, a heating device 9, an evaluation device main body, and a workpiece feeding device 10b, which are sequentially arranged on the base 11 in the traveling direction of the long prismatic workpiece 1.
The workpiece feeding devices 10a and 10b are parts for guiding the workpiece 1 and can feed the workpiece by intermittent linear motion by a rack and pinion mechanism by a motor (not shown). Examples of the feed mechanism include a linear motion mechanism that uses a screw such as a hydraulic cylinder, an air cylinder, and a ball screw in addition to the rack and pinion mechanism.

  The heating device 9 is a device for heating the workpiece 1 that moves intermittently linearly. As the heating means, any means such as infrared heating, electric heating, resistance heating, and induction heating can be adopted depending on the type of the work 1. In the present invention, it is preferable to use an infrared heating furnace that is not in contact with the workpiece 1 and that can uniformly and rapidly heat the workpiece 1. The infrared heating furnace is preferably a heating device using an infrared lamp that can collect light by using a reflector or a lens and increase the heating efficiency, and can be a cheaper and more compact device than a high-frequency induction heating device. it can.

  The evaluation apparatus main body is composed of a gantry 8 disposed on the base 11, a die 2 provided on the gantry 8, and a punch 3 disposed above the die 2 for forging the workpiece 1. ing. By measuring the load for pushing the punch 3 into the work 1 and the load for pulling it out, the lubricity of the forging lubricant and the durability of the mold material can be evaluated.

  The die 2 has means for restraining the prismatic workpiece in a direction perpendicular to the direction in which the workpiece 1 is fed out. As shown in FIG. 1 (b), the die 2 has an appropriate clearance with respect to both side surfaces of the punch pushing portion for the purpose of preventing the workpiece 1 from spreading laterally by being pushed into the punch 3. It is installed with an angle θ so as to spread in the workpiece feeding direction. The die 2 can stably give a predetermined pushing amount without the pushing force from the punch 3 escaping to the side surface of the workpiece 1. The optimum clearance between the workpiece 1 and the die 2 can be selected from the feeding accuracy of the workpiece feeding device and the dimensional accuracy of the workpiece 1. Moreover, the spreading angle θ of the die 2 may be selected in consideration of factors such as the pushing force of the workpiece feeding device and the contact area between the workpiece 1 and the die 2, and is preferably 0.5 to 5 °.

  The frame 8 on which the die 2 is installed is provided with a heating means 4 such as a heater and a tension / compression load cell 5. A temperature sensor 6 such as a thermocouple is provided near the lower portion of the die 2 to control the temperature of the die 2. It is preferable to monitor the temperature of the die 2 from the outside using a non-contact type radiation thermometer (not shown). The heating means 4 heats the die 2.

  The punch 3 is formed of a die material for forging, and is disposed so as to be movable up and down above the workpiece in the drawing of FIG. The punch 3 can be operated by a crank type press or the like. A heating means 4 and a temperature sensor 6 for controlling the temperature of the punch 3 are provided. The form of the punch 3 can be set according to the die that is actually forged. For example, the cross-sectional shape of the punch 3 can be set to a circle such as a perfect circle or an ellipse, or a polygon such as a rectangle or a triangle.

  Moreover, it is preferable that a thermocouple for observing a temperature change due to sliding heat generation or cooling and for setting a temperature condition is embedded in the tip portion of the punch 3. The thermocouple is preferably installed at a distance of 0.5 mm to 3 mm from the sliding surface. If it is less than 0.5 mm, there is a risk of exposing the thermocouple due to wear, etc. If it exceeds 3 mm, the surface temperature may not be measured accurately. Further, if the thermocouple and the thermocouple hole are fixed with a material having high thermal conductivity (electric heating material), the temperature follow-up property becomes higher.

FIG. 2 shows the shape of the tip of the punch. FIG. 2A shows an example of a punch used in the present invention. FIG. 2B is a diagram showing a punch having an R-shaped tip edge portion that is generally used.
In order to evaluate in a short time, as shown in FIG. 2A, it is more preferable that the tip end is a tapered shape as a shape in which the punch is pushed into the workpiece under more severe conditions. Even when R is provided at the tip end portion of the taper shape, it is most preferable that it is kept at 0.5 mm or less and the R shape is not provided.
In the punch 3a having the tapered tip, a high stress is generated on the tapered surface during sliding, and the relative sliding distance accompanying the plastic flow of the workpiece is longer than that of the punch 3b having the R-shaped tip edge. Thus, since the surface area enlargement ratio is increased, it is possible to set severe conditions that easily cause damage such as wear.
The punch 3a having a tapered tip has a taper angle α (see FIG. 2 (a)) of 50 ° or more and 80 ° or less so that the die material can be evaluated under the conditions with the highest load as described above. Preferably there is. The highest load when the taper angle α is 50 ° or more and 80 ° or less is a result obtained by stress analysis.

  In FIG. 1, an air spray gun 7 for spraying lubricant onto the punch 3 is provided in the vicinity of the punch 3. The air spray gun 7 has means for spraying the lubricant onto the punch at a time other than the time when the punch 3 is pushed into the work 1. It is preferable that the means has a function of arbitrarily setting the spray amount, spray time, and spray timing. By providing this function, optimization of the supply amount and supply frequency of the lubricant can be studied.

The evaluation of the lubricity of the hot forging lubricant and the evaluation of the mold material using the evaluation device is performed as follows.
(1) The long prismatic work 1 is sent out by intermittent linear motion. As the prismatic workpiece 1, standard square steel provided by a steel material manufacturer can be used. A prismatic workpiece 1 of 10 mm × 10 mm × 16 mm × 1000 mm can be exemplified, and in this case, the punch 3 can be exemplified by a diameter of 10 mm. Since standard square steel can be used, in the preparation of the test sample, only cutting is performed and the processing cost is reduced. Further, by subjecting the prismatic workpiece 1 to the lubricating film treatment, it is possible to evaluate the lubricity of the lubricating coating treatment and simultaneously evaluate the durability of the mold material when the workpiece 1 is subjected to the lubricating film treatment.

(2) When the linear motion of the prismatic workpiece 1 is stopped, the punch 3 made of a forging die material is pushed in from a direction perpendicular to the linear motion of the workpiece 1 to form a recess. The mold material punch 3 is sprayed with lubricant on the tip surface using an air spray gun 7 at a time other than the time when it is pushed into the workpiece 1. For this reason, it is possible to supply a stable lubricant, and it is possible to evaluate the durability of the mold material when the lubricant is stably supplied together with the lubricity of the lubricant.
By providing a function capable of arbitrarily setting the spray amount, spray time, and spray timing of the lubricant sprayed onto the air spray gun 7, at least the pushing load of the punch 3 and the pulling load in the pulling step are set for each of these condition settings. By measuring one load, optimization of the lubricant spraying condition can be studied.
In addition, when only water is used as the lubricant, the lubrication conditions become severe, so that the forging die can be evaluated in an extremely short period of time compared to the case where a normal lubricant is used.

(3) The mold material punch 3 pushed out from the depression is pulled out. Since it has this extraction procedure, when evaluating the durability of the mold material, it is possible to grasp the relationship between the damage state such as wear of the mold and the punch indentation load or the extraction load.
Here, by using the punch 3 in which the thermocouple is embedded in the tip, the temperature change of the die material due to sliding heat generation and cooling, and the correlation with the punch indentation load and the extraction load under the set temperature condition, etc. It can be grasped in association with the type of lubricant and spraying conditions, and it becomes possible to evaluate mold materials and lubricants more precisely.
Moreover, by using the punch 3a having a tapered tip, it is possible to set severe conditions that easily cause damage such as wear as described above, and it is possible to evaluate the lubricant and the mold material in a short period of time. it can.

(4) The two procedures of sending out and forming the dent and extracting are repeated, and both the indentation load at the time of forming the dent and the extraction load at the time of extraction, or any one of the loads is measured. By moving the punch 3 in the downward direction of the up / down arrow shown in FIG. 1, the indentation load is measured by pushing the punch 3 into the work 1, and the extraction load can be measured by pulling out. The load can be measured by the load cell 5. When the indentation load is large, the lubricity is poor, and when the indentation load is small, the lubricity is excellent. Further, the die material can be evaluated by investigating the damage state of the punch 3 after performing the forging process for a predetermined number of shots. That is, it can be said that a mold material that can perform many shots without damage is superior. Thus, the lubricity of the hot forging lubricant can be evaluated by continuously measuring the indentation load and pull-out load during forging, and the die material can be evaluated.

In the forging process using the punch, the workpiece 1 is heated to a predetermined forging temperature by the heating device 9 immediately before the die material punch 3 is pushed into the long prismatic workpiece 1. Therefore, it is possible to evaluate a hot forging lubricant and die material that are practical.
The forging temperature in this evaluation method can be set by simulating forging in an on-site factory. For example, in the actual continuous hot forging process, even if the initial punching temperature is normal temperature, if hot forging is repeated continuously, the punching temperature is generated by frictional heat and forging energy, and the temperature becomes several hundred degrees Celsius. Such actual forging conditions can be reproduced by controlling the punch temperature in the evaluation method of the present invention.

Example 1
Made by Hitachi Metals, Ltd. Using a mold material obtained by subjecting the mold material YXR7 to standard heat treatment and a mold material obtained by performing gas soft nitriding after the standard heat treatment of the mold material YXR7, the tip shown in Table 1 has a tapered shape. A standard heat-treated metal mold punch test piece and a gas soft nitriding metal mold punch test piece were prepared. Using these mold material punch test pieces, the following forging test is performed, the number of shots in which the punch test pieces are worn is measured, and the number of wear observation shots is also shown in Table 1.

Comparative Example 1
Made by Hitachi Metals: The die edge material shown in Table 1 has an R shape using a die material obtained by subjecting the die material YXR7 to a standard heat treatment and a die material obtained by subjecting the die material YXR7 to a gas soft nitriding treatment. A punch test piece made of a standard heat-treated mold material and a gas soft nitriding-treated mold material punch test piece having the above were prepared. Using these mold material punch test pieces, the following forging test is performed, the number of shots in which the punch test pieces are worn is measured, and the number of wear observation shots is also shown in Table 1.

<Forging test>
A punch test piece made of a mold material is attached to the punch 3 of the evaluation apparatus shown in FIG. 1, and the workpiece 1 made of material S50C is heated and controlled to 800 ° C. by the heating device 9 and the temperature sensor 6, and then the prismatic workpiece 1 is intermittently straightened. The punch test piece made of a die material is continuously pushed into the work 1 to perform forging, and the number of shots in which wear occurs on the punch test piece is measured. This test was performed under non-lubricated conditions in order to obtain test results in a short period of time. However, cooling water was sprayed by the air spray gun 7 in order to adjust the amplitude of the punch test piece temperature to be constant.

表１に示すように標準熱処理金型材の摩耗の観測においても、また耐摩耗性の高いガス軟窒化処理金型材の摩耗の観測においてもテーパ形状パンチは、Ｒ形状パンチに比べて少ないショット数で金型材の評価が可能である。

As shown in Table 1, the taper-shaped punch has a smaller number of shots than the R-shaped punch in both the observation of the wear of the standard heat-treated mold material and the observation of the wear of the gas soft nitriding mold material having high wear resistance. Evaluation of mold material is possible.

  The lubrication evaluation method for forging lubricant and the material evaluation method for forging die material of the present invention are forging lubricants in a wide temperature range from cold to hot while being an evaluation form close to an actual forging form. It is possible to evaluate the lubricity of the mold material, and it can be applied to the durability evaluation of the mold material at a low cost without taking the labor of the operator.

It is a schematic diagram of an evaluation apparatus. It is a figure which shows the front-end | tip part shape of a punch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Work 2 Die 3 Punch 4 Heating means 5 Tension / compression load cell 6 Temperature sensor 7 Air spray gun 8 Mounting base 9 Heating device 10 Work feeding device 11 Base

Claims (11)

  In the method for evaluating the lubricity of a forging lubricant and the method for evaluating the material of a forging die material, a step of feeding a long prismatic workpiece in an intermittent linear motion, and the workpiece can be moved up and down upward when the linear motion is stopped. A step of pushing a forging die material punch, to which a forging lubricant is applied, into the workpiece and forming a recess, and a step of extracting the die material punch that has been pushed into the recess, and sending out the punch And the step of forming the recess and the drawing step are repeatedly performed, and the lubricity evaluation of the lubricant is performed by measuring at least one of the indentation load in the step of forming the recess and the pull-out load in the drawing step. And a forging lubricant and a method for evaluating a mold material, characterized by performing material evaluation of the mold material for forging.   2. The forging lubricant and mold material evaluation method according to claim 1, wherein the workpiece is heated to a forging temperature before the step of forming the depression.   3. The forging lubricant and mold material evaluation method according to claim 2, wherein the means for heating the workpiece is a high frequency induction heating furnace or an infrared heating furnace.   The forging lubricant is sprayed onto the punch at an arbitrarily set spraying amount, spraying time, and spraying timing after the punch pushing-out process. The forging lubricant and the die material evaluation method according to claim 3.   5. The forging lubricant and die material evaluation method according to claim 1, wherein the forging die material is evaluated using water as the forging lubricant.   6. The forging lubricant and die material evaluation method according to claim 1, wherein the forging die material punch has a thermocouple embedded in a tip portion thereof.   The forging lubricant and mold material evaluation method according to any one of claims 1 to 6, wherein a tip of the forging mold material punch has a tapered shape.   8. The forging lubricant and die material evaluation method according to claim 7, wherein the forging die material punch has a taper angle of 50 ° or more and 80 ° or less.   The forging according to any one of claims 1 to 8, wherein the elongated prismatic workpiece is obtained by applying a lubricant film treatment to a recess forming portion in the step of forming the recess. Evaluation method for lubricants and mold materials.   The forging lubricant according to any one of claims 1 to 9, further comprising means for constraining the prismatic workpiece in a direction perpendicular to a feeding direction of the workpiece in the step of forming the recess. And evaluation method of mold material.   An apparatus for evaluating the lubricity of a forging lubricant and the material of a forging die material, a means for feeding a long prismatic workpiece in an intermittent linear motion, and a vertical movement back and forth above the workpiece when the linear motion stops A means for freely forming and forging a forging die material punch coated with a forging lubricant into the workpiece to form a recess, a means for extracting the mold material punch that has been pressed from the recess, A forging lubricant and a mold material evaluation apparatus, comprising: means for repeatedly feeding and forming the recess.

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