JP2012173119A - Friction testing method and friction testing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction testing method that can simulate damage to a tool used to manufacture a seamless steel pipe and evaluate performance of the tool and a lubricant which are actually used.SOLUTION: There is provided a friction testing method of simulating friction between a tool and a rolled material during manufacture of a seamless steel pipe, the friction testing method including rotating a first columnar test piece 1 and a second columnar test piece 2 on axes 1X, 2X respectively in a state in which the first test piece 1 and the second test piece 2 are held so that the axes 1X, 2X do not intersect while the first test piece 1 and the second test piece 2 are pressed against each other with an outer peripheral surface of the second test piece 2 brought into contact with an end surface of the first test piece 1.

Description

  The present invention relates to a friction test method and a friction test apparatus for simulating damages such as wear, seizure, and rough skin that occur between a tool and a material to be rolled during rolling of steel and non-ferrous metals in a state close to actual rolling conditions. In particular, the present invention relates to a friction test method and a friction test apparatus for simulating friction between a tool and a material to be rolled in the production of a seamless steel pipe.

  Tools used for rolling seamless steel pipes, steel plates, section steel, strip steel, wire rods, etc., rub against each other while being in contact with the material to be rolled during rolling. Required. Therefore, it is necessary to conduct a friction test that simulates the friction between the rolling tool and the material to be rolled in a state close to the actual rolling conditions, and to evaluate the performance of the actually used tool and lubricant.

  Conventional techniques relating to such a friction test include the following.

  As a conventional representative friction test, for example, as disclosed in Patent Document 1, there is a so-called rolling friction test.

  FIG. 1 is a perspective view schematically showing an outline of a test apparatus used in a rolling friction test. As shown in the figure, in the rolling friction test, a disk-shaped heating piece 101 corresponding to a material to be rolled and a disk-shaped test piece 102 corresponding to a rolling roll material (tool) are prepared, While holding the shaft centers 101X and 102X in parallel with each other, the heating piece 101 and the test piece 102 are rotated around the respective axis centers 101X and 102X in a state where the outer peripheral surfaces are in contact with each other and pressed. . During the test, the rotational speeds of the heating piece 101 and the test piece 102 are individually adjusted to give an appropriate slip to the contact portion between the heating piece 101 and the test piece 102, thereby generating friction.

  Further, in Patent Document 1 described above, a ring corresponding to the material to be rolled and a ring-shaped test material corresponding to the rolling roll material are prepared, and the inner surface of the ring heated to a high temperature is brought into contact with the outer surface of the ring-shaped test material. Also disclosed is a friction test method for imparting friction and other wear conditions to the contact portion.

  However, any of the friction test methods disclosed in Patent Document 1 can evaluate the performance against wear. For example, damage caused on a roll used in piercing rolling of a seamless steel pipe, It is impossible to accurately simulate damage that occurs at the edge of a roll used in rolling, particularly rough skin.

  Further, in Patent Document 2, when a roll material is subjected to a friction test by rolling the material to be rolled using a pair of rolls, a tension is applied to the material to be rolled toward the front in the rolling direction. A friction test method for performing asymmetric rolling by driving only one of the rolls and following the other roll is disclosed. When this test method is used, the test can be performed under the rolling conditions close to the actual rolling of the steel sheet, so that it is possible to simulate the damage caused to the roll used in the rolling of the steel sheet.

  However, even with the friction test method disclosed in Patent Document 2, it is impossible to accurately simulate damage such as rough skin that occurs in tools used in the manufacture of seamless steel pipes, for example, rolls used in piercing and rolling.

JP-A-56-150326 JP-A-1-210848

The present invention has been made in view of the above problems, and an object thereof is to provide a friction test method and a friction test apparatus having the following characteristics:
It is possible to simulate the damage that occurs in tools used in the production of seamless steel pipes, and to evaluate the performance of tools and lubricants that are actually used.

  The gist of the present invention is as follows.

(I) A friction test method for simulating friction between a tool and a material to be rolled in the production of a seamless steel pipe,
The friction test method is
While the outer peripheral surface of the columnar second test body is brought into contact with the end surface of the columnar first test body and both are pressed against each other, the axes of the first test body and the second test body do not cross each other. Rotating the first test body and the second test body around the respective axis centers in a state of being held in
A friction test method characterized by

  In this test method, it is preferable that at least the first test body of the first test body and the second test body is heated before rotating the first test body and the second test body.

  In the above test method, the first test body and the second test body can be rotated by applying a rotational driving force to at least one of the first test body and the second test body. .

(II) A friction test apparatus that simulates friction between a tool and a material to be rolled in the production of seamless steel pipes,
The friction test apparatus
A cylindrical first specimen;
A cylindrical second test body,
In a state where the outer peripheral surface of the second test body is brought into contact with the end surface of the first test body and both are pressed against each other, the first test body and the second test body are held so that the respective axis centers do not cross each other. A driving mechanism for rotating the first test body and the second test body around the respective axes;
Friction testing device characterized by

The friction test method and friction test apparatus of the present invention have the following significant effects:
It is possible to simulate the damage that occurs in tools used in the production of seamless steel pipes, and to evaluate the performance of tools and lubricants that are actually used.

It is a perspective view which shows typically the outline | summary of the testing apparatus used by a rolling friction test. It is an external view which expands and shows the outer peripheral surface of the roll used by actual piercing-rolling. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically the outline | summary of the friction test apparatus which can apply the friction test method of this invention, the figure (a) shows a perspective view, and the figure (b) shows a top view, respectively. It is a figure which shows typically the outline | summary of the friction test apparatus used for the comparison in the Example, The figure (a) shows a perspective view, The figure (b) shows a top view, respectively. It is the figure which put together the friction test result in an Example.

  In order to achieve the above object, the present inventors have observed in detail the rolls used in piercing and rolling in the production process of seamless steel pipes, and test pieces that have been subjected to hot rolling friction test. Since each form of damage is different, we have intensively studied the cause. As a result, the following knowledge was obtained.

  (A) In the case of a rolling friction test, the rotation direction of a test piece corresponding to a roll material as a tool matches the rotation direction of a heating piece corresponding to a material to be rolled. Therefore, for example, wrinkles generated on the heated piece (rolled material) due to the seizure generated on the test piece (roll) are repeatedly generated on the same circumference. Thereby, the wrinkles on the heating piece and the test piece are in a form that is connected linearly, or the wrinkles generated in the previous round are scraped off by the wrinkles generated in the next round.

  On the other hand, in the case of piercing and rolling, the rotating direction of the roll and the extending direction of the material to be rolled are different. Therefore, for example, wrinkles are generated on the material to be rolled due to seizures generated on the roll, and the probability that the portions of the wrinkles will rub in the next round becomes extremely low, , Greatly deviate from the rotation direction of the roll. Thereby, in an actual roll, wrinkles occur in an independent form.

  FIG. 2 is an external view showing an enlarged outer peripheral surface of a roll used in actual piercing and rolling. As shown in the drawing, rough skin damage is caused on the outer peripheral surface of the roll used in piercing and rolling due to remarkable contact with the material to be rolled. This damage (rough skin) is a set of streak-like wrinkles that are inclined one by one from the rotation direction of the roll (vertical direction in FIG. 2).

  From these facts, the damage that occurs when the rotation direction of the tool is different from the stretching direction of the material to be rolled, such as the roll used in piercing and rolling, is the rotation direction of each test piece as in the rolling friction test. It will have a different form than the damage that occurs when they match.

  (B) In actual piercing and rolling, since the contact time between the material to be rolled and the roll is long, the surface temperature of the roll becomes high. Therefore, the strength and hardness of the roll surface layer are lowered, and the roll is easily damaged. On the other hand, in the friction test, since the dimension of the test piece to be evaluated is small and the contact time is short, the temperature of the test piece corresponding to the roll does not rise as much as the actual roll. For this reason, the damage generated on the surface of the test piece corresponding to the roll in the friction test tends to be minor compared to the actual case, and it is difficult to say that the damage of the actual roll is simulated.

  The present invention has been completed based on the above findings (A) and (B). That is, the friction test method of the present invention presupposes the production of seamless steel pipes, and simulates damage to tools such as rolls used in piercing rolling, stretching rolling, constant diameter rolling, etc. The first test body and the second test body are brought into contact with the outer peripheral surface of the cylindrical second test body assuming the tool and pressed against each other with the end face of the cylindrical first test body assuming The first test body and the second test body are rotated around the respective axis centers in a state where the axis centers are held so as not to cross each other.

  In addition, the friction test apparatus of the present invention is premised on the production of seamless steel pipes, and in order to simulate the damage of the tool used in the production process, a cylindrical first test body assuming a material to be rolled and a tool An assumed cylindrical second test body, the outer peripheral surface of the second test body is brought into contact with the end face of the first test body and the two are pressed against each other, and the first test body and the second test body are moved to each other. A drive mechanism is provided for rotating the first test body and the second test body around the respective axis centers while holding the axes so as not to cross each other.

  Below, the preferable aspect of the friction test method and friction test apparatus of this invention is demonstrated.

  FIG. 3 is a diagram schematically showing an outline of a friction test apparatus to which the friction test method of the present invention can be applied. FIG. 3A is a perspective view and FIG. 3B is a plan view. As shown in the figure, the friction test apparatus uses a first test body 1 and a second test body 2 that are formed in a cylindrical shape as evaluation targets. The first test body 1 assumes a material to be rolled that is rolled in the manufacture of a seamless steel pipe, for example, a billet that is rolled by piercing rolling. The 2nd test body 2 assumes the tool used by manufacture of a seamless steel pipe, for example, the roll which restrains the outer peripheral surface of a billet by piercing rolling.

  The friction test device holds the outer peripheral surface of the second test body 2 in contact with the end surface of the first test body 1, and further the axial center 1X of the first test body 1 and the axial center of the second test body 2. The axial center 2X of the second test body 2 is held at a predetermined angle θ with respect to the radial direction of the first test body 1 so that the 2X do not cross each other. Here, the axial centers 1X and 2X are concepts including not only the existence regions of the respective test bodies 1 and 2 but also the extended lines from the test bodies 1 and 2. Then, the friction test apparatus presses the first test body 1 and the second test body 2 in the direction in which they are in contact with each other, and in this state, the first test body 1 is rotated around its own axis 1X, and the second test body is rotated. The body 2 is rotated about its own axis 2X. Thereby, the 1st test body 1 and the 2nd test body 2 slide at a mutual contact part, and friction generate | occur | produces. At this time, in the contact portion between the first test body 1 and the second test body 2, the axis 2X of the second test body 2 is arranged to be inclined with respect to the radial direction of the first test body 1. Along with this, the first test body 1 and the second test body 2 slide in a state where the respective rotation directions are deviated.

  According to the friction test method using such a friction test apparatus, each rotation direction is shifted at the contact portion between the first test body 1 (rolled material) and the second test body 2 (tool). As in the case of piercing and rolling in which the rotation direction of the roll as the tool and the drawing direction of the material to be rolled are different, wrinkles generated in the contact portion are generated in an independent form one by one. For this reason, it is possible to simulate the damage that occurs in tools used in the production of seamless steel pipes, and as a result, it is possible to evaluate the performance of tools and lubricants that are actually used under conditions close to actual rolling conditions. become.

  In the present invention, the inclination angle θ of the axis 2X of the second test body 2 with respect to the radial direction of the first test body 1 can be freely set in consideration of actual rolling conditions. However, when the inclination angle θ is 0 °, the axis 1X of the first test body 1 and the axis 2X of the second test body 2 cross each other, and the first test body 1 and the second test body 2 are in contact with each other. Since the respective rotation directions coincide with each other in the portion, wrinkles generated in the contact portion are generated in the same form as in the conventional rolling friction test. For this reason, it is not appropriate to set the inclination angle θ to 0 °, and is preferably set within a range of 5 to 90 °. This is because when the inclination angle is set to less than 5 °, the shape of the ridge may not be independent as in the case of setting to 0 °. On the other hand, there is no reason to specify the upper limit, but even if it is set at an inclination angle exceeding 90 °, the sliding direction will only change, so the same result will be obtained if the roll rotation direction is changed. Meaningless.

  Further, in the friction test, in order to press the first test body 1 and the second test body 2 together, an external force may be applied to either one, or an external force may be applied to both. This pressing load can also be set freely in consideration of actual rolling conditions, and can be increased or decreased during the test. Further, in order to rotate the first test body 1 and the second test body 2 during the friction test, a rotational driving force may be applied to one of the two and the other driven, or both may be driven. May be given.

  Further, in the present invention, in consideration of actual rolling conditions, the first test body 1 (rolled material) is brought to a predetermined temperature before the test for rotating the first test body 1 and the second test body 2 is performed. It is preferable to heat. This is because it approaches the actual rolling conditions. In addition to this, it is preferable that the second specimen 2 (tool) is also heated. This is because the actual rolling conditions are further approached.

  In addition, in the above embodiment, the first test body is assumed to be a material to be rolled and the second test body is assumed to be a tool, but conversely the first test body is assumed to be a tool, The specimen may be a material that assumes a material to be rolled.

  In order to confirm the effect of the present invention, a friction test was performed using the friction test apparatus shown in FIG. For comparison, a friction test was performed using a friction test apparatus shown in FIG.

  4A and 4B are diagrams schematically showing an outline of a friction test apparatus used for comparison in the examples. FIG. 4A is a perspective view and FIG. 4B is a plan view. The friction test apparatus used in the comparative example shown in the figure is in contact with the outer peripheral surface of the second test body 2 on the end face of the first test body 1 as compared with the friction test apparatus used in the example of the present invention shown in FIG. The first test body 1 and the second test body 2 are rotated around the respective axis centers 1X and 2X while pressing the two against each other, but the axis 1X and the second center of the first test body 1 are the same. The difference is that the axis 2X of the test body 2 intersects with each other, that is, the inclination angle of the axis 2X of the second test body 2 with respect to the radial direction of the first test body 1 is 0 °.

[Specimen]
The material and dimensions of the first test specimen are as follows.
・ Material: SUS304
・ Dimensions: Diameter 100mm, thickness 30mm
The material and dimensions of the second specimen are as follows.
-Material: High carbon alloy for forging rolls described in JP-A-10-81937-Dimensions: 70 mm diameter, 20 mm thickness

[Test conditions]
The test conditions are shown in Table 1 below.

  As shown in the same table, the first specimen was preliminarily heated to 1000 ° C. by high-frequency heating and used for the test. The second specimen was preliminarily heated to 800 ° C. by high-frequency heating and subjected to the test, or was subjected to the test while being kept at room temperature without being heated. In addition, the pressing load between the first test body and the second test body is increased by 200N every 30 seconds starting from 200N, and finally increased to 3000N at the maximum, and 3000N is constantly applied from the initial stage. Two conditions were used. The inclination angle of the axis of the second test body with respect to the radial direction of the first test body was 30 ° in Examples 1-4 of the present invention, and 0 ° as described above in Comparative Examples 1 and 2.

  And after the friction test in each conditions of this invention examples 1-4 and comparative examples 1 and 2, the contact part of each 1st test body and a 2nd test body was observed, and the condition of damage was investigated from the appearance. .

[Test results]
FIG. 5 is a table summarizing the friction test results in the examples. In the same figure, the test conditions of Invention Examples 1 to 4 and Comparative Examples 1 and 2 are classified, and the appearance of the contact portion between the first test body and the second test body after the test is shown enlarged. In the figure, the meanings of the symbols in the “evaluation” column are as follows.
A: Excellent. It shows that large damage similar to that actually caused by rolling seamless steel pipes was observed.
○: Good. This shows that minor damage similar to that actually caused by rolling seamless steel pipes was observed.
×: Impossible. This shows that no damage similar to that actually caused by rolling seamless steel pipes was found.

  The following is shown from the results shown in FIG. In the case of Comparative Example 1, during the test, the respective rotation directions coincide at the contact portion between the first test body and the second test body, and the relative speed difference between the first test body and the second test body is small. In addition, no seizure occurred and no damage occurred.

  In the case of Comparative Example 2, since the relative speed difference between the first test body and the second test body was larger than that in Comparative Example 1, seizure occurred and the contact portion of the first test body was worn. Two specimens had only material adhered to the contact area and no damage occurred.

  On the other hand, in the case of each of the inventive examples 1 to 4, damage similar to rough skin occurring in the actual roll occurred in the contact portion of the second test body. In particular, among Examples 1 to 4 of the present invention, in the case of Examples 2 and 4 in which the second test body was heated, the second test body was compared to the cases of Inventive Examples 1 and 3 in which it was not heated. The damage that occurred in the contact area was large, and the damage state was closer to that of actual rolling.

  The present invention can be effectively used for evaluating the performance of tools and lubricants actually used in the production of seamless steel pipes.

1: the first specimen, 1X: the axis of the first specimen,
2: Second specimen, 2X: Axis of second specimen

Claims (4)

A friction test method for simulating friction between a tool and a material to be rolled in the production of a seamless steel pipe,
The friction test method is
While the outer peripheral surface of the columnar second test body is brought into contact with the end surface of the columnar first test body and both are pressed against each other, the axes of the first test body and the second test body do not cross each other. Rotating the first test body and the second test body around the respective axis centers in a state of being held in
A friction test method characterized by Heating at least the first specimen of the first specimen and the second specimen before rotating the first specimen and the second specimen;
The friction test method according to claim 1, wherein: Rotating the first test body and the second test body by applying a rotational driving force to at least one of the first test body and the second test body;
The friction test method according to claim 1 or 2. A friction test apparatus for simulating friction between a tool and a material to be rolled in the production of a seamless steel pipe,
The friction test apparatus
A cylindrical first specimen;
A cylindrical second test body,
In a state where the outer peripheral surface of the second test body is brought into contact with the end surface of the first test body and both are pressed against each other, the first test body and the second test body are held so that the respective axis centers do not cross each other. A driving mechanism for rotating the first test body and the second test body around the respective axes;
Friction testing device characterized by

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