JPS6373134A - Method of testing friction lubrication - Google Patents

Abstract

PURPOSE:To evaluate the friction characteristic at an interface between a tool and a material to be machined, by rolling the material to be machined with a roll and a tool, and detecting the working force which acts in the vertical direction with respect to the rolling direction and the working force which acts on the tool in parallel with the rolling direction. CONSTITUTION:A plate-shaped tool 1, which has a lubricating film 6 having the specified surface state owing to the application of a lubricant and the like, is fixed on a bearing and the like under the condition of no friction. A material to be machined 3 in a plate shape is rolled between the tool and a roll 2. Then pressure P, which is vertical to the rolling direction, acts on the roll 2 or the tool 1. At the same time, a force F, which is in parallel with the rolling direction, acts on the tool 1 owing to the friction at the interface between the material to be machined 3 and the tool 1. The forces P and F are detected with a compressing force detector 4 and a frictional force detector 5. Then the friction coefficient mu between the material to be machined 3 and the tool 1 is obtained by mu=F/P using the low of friction. The change in the friction coefficient is followed with time from the start of the rolling. Thus, the persistence and the durability of the lubricating film 6 on the surface of the tool and the seizure property between the material to be machined and the tool 1 can be evaluated.

Description

[Detailed Description of the Invention] "Objective of the Invention" The present invention aims to calculate the true friction coefficient at the interface between a workpiece and a tool during plastic working by determining the force acting perpendicularly to the rolling direction and the force acting parallel to the rolling direction. The aim is to accurately evaluate the friction characteristics in plastic working from the detected values of force and force.

INDUSTRIAL APPLICATION FIELD The present invention relates to a testing machine and a testing method for evaluating the frictional characteristics of the interface between a tool and a workpiece in plastic working.

BACKGROUND OF THE INVENTION In plastic processing such as rolling, extrusion, and forging, lubricants are often used for purposes such as reducing processing force, improving product quality, and preventing damage to tools.

In addition, it is not uncommon for tools to be subjected to special surface treatments, such as by heat treating them or coating them with different materials.

To explain mandrel rolling, which is one of the steady hot plastic working processes in which the wall thickness of a tube is reduced between a slotted roll and a mandrel bar, as an example, in order to reduce the frictional resistance of the mandrel bar, the mandrel bar is Usually, a graphite-based lubricant is applied to the surface. However, if the lubrication condition is poor and the coefficient of friction becomes high, not only will the shape of the rolled tube deteriorate, but the tube material and mandrel bar will seize, causing damage to the inner surface of the tube and the bar surface. Furthermore, it may be difficult to remove the mandrel bar from the rolled tube. Furthermore, in the method that has been widely adopted in recent years, in which the speed of the mandrel bar is held constant during rolling, the success or failure of machining depends on the quality of the lubrication, as if the load on the bar becomes excessive due to poor lubrication, the bar may break. It's no exaggeration to say that.

However, the selection of lubricants and the determination of lubrication conditions currently rely on experience. Therefore, there is a strong desire to establish a method for easily evaluating the friction coefficient and durability of a lubricant for mandrel rolling, as well as the seizure resistance between a tube material and a mandrel bar.

Furthermore, even in unsteady plastic working, such as forging, where working conditions such as reduction rate and load change during one working process, a lubricant is usually applied to the surface of the die or mold. Even in these processes, if the friction coefficient of the lubricant is high, the product value will decrease due to insufficient filling of the material in the mold, and the rolling reduction will be large (this will cause the material to seize in the mold and cause galling). As described above, there is a need to establish a method for easily evaluating the friction coefficient, durability, and seizure resistance of the lubricant between the mold and the material, since this may cause damage to the mold.

The conditions of the contact interface between the tool and the workpiece in plastic working as described above are such that extremely high pressure acts over a large contact surface, and a new surface is exposed as the workpiece undergoes plastic deformation. Furthermore, in hot working, the contact interface is exposed to high temperatures.

Conventionally, basic testing machines such as the four-ball type, Timken, etc., which are published in pages 371 and below of the Lubrication Handbook edited by the Japan Society of Lubricants, and their improved machines have been widely used for lubricant evaluation tests. The ring compression method is sometimes used to evaluate commercial lubricants.

Problems to be Solved by the Invention However, in tests using basic testing machines such as the four-ball type, Timken, and their improved machines, the contact area that applies the load is the contact between elastic bodies, and the contact area is small due to point or line contact. Although the load is small and locally high, there is no large exposure of the newly formed surface due to plastic deformation, and the test results merely elucidate the friction phenomenon, making it difficult to properly evaluate the friction characteristics in actual plastic working. There isn't.

In addition, in the ring compression method, the surface elongation and exposure of new surfaces in simple compression are small compared to actual plastic working, so the ranking of lubricant lubricity based on the friction coefficient measured by this method and the actual The rankings determined based on the processing force and seizure resistance during extrusion processing etc. are often interchanged, and the evaluation of the friction coefficient, durability and seizure resistance of lubricants is not properly performed for actual processing. It's hard to say that there are.

Therefore, in order to simulate actual plastic working, processing is performed using special equipment that is the same size or a fraction of the operating equipment, and the friction coefficient due to processing force is evaluated and the relationship between the tool and the workpiece is evaluated. Although burn-in properties are sometimes evaluated, these facilities have the drawbacks of being usually large, expensive to produce, and complicated to operate.

"Structure of the Invention" Means for Solving the Problem A plate-shaped workpiece is rolled between a rotating rolling roll and a fixed plate-shaped tool, and an acting force acting perpendicular to the rolling direction,
Detects both the force acting on the tool parallel to the rolling direction,
A friction lubrication test method characterized by evaluating the friction characteristics at the interface between a tool and a workpiece during plastic working.

By detecting the rolling blade (P) perpendicular to the active rolling direction and the rolling blade (F) parallel to the rolling direction, the friction coefficient μ can be determined from the law of friction as μ=F/P.

From the change in the friction coefficient μ over time, it is possible to evaluate and determine the durability, durability, and seizure resistance of a lubricant film on the tool surface.

We can test and evaluate both steady plastic working and unsteady plastic working.

EXAMPLE To further explain the present invention as described above, the testing machine according to the present invention rolls a plate-shaped workpiece between a rotating rolling roll and a fixed plate-shaped tool. Firstly, a large plastic deformation is applied to the workpiece, and secondly,
A high pressure is generated at the contact interface between the newly exposed surface of the workpiece and the tool surface, and relative slip is applied to the workpiece and the tool to determine the contact state between the tool and the workpiece during actual plastic working. In this state, a detection mechanism is used to simultaneously detect the force acting perpendicularly to the rolling direction and the force acting parallel to the rolling direction on the tool, and from the detected values of both, it is possible to determine the By calculating the true coefficient of friction at the interface with the tool, it is possible to accurately evaluate the friction characteristics in plastic working.

If such the present invention is explained using the accompanying drawings, the first
The figure shows one example of the principle relationship of the present invention. A plate-shaped tool 1 having a film 6 with a predetermined surface condition by applying lubricant or the like is placed on a bearing or the like under a frictionless condition. When a plate-shaped workpiece 3 is rolled between the tool 1 and the rolling roll 2, the rolling blade P perpendicular to the rolling direction acts on the roll 2 or the tool 1, and at the same time the workpiece 3 A force F parallel to the rolling direction acts on the tool 1 due to friction at the interface between the tool 1 and the tool 1. When such respective forces P and F are detected by load detectors 4 and 5,
According to the law of friction, the friction coefficient μ at the interface between the workpiece 3 and the tool 1 is determined by μ=F/P. By tracking the change in the friction coefficient determined in this way over time from the start of rolling, the sustainability and durability of the lubricant film 6 on the tool surface and the seizure resistance between the workpiece 3 and the tool 1 can also be evaluated. If a cylindrical roll for plate rolling is used as the roll 2, the rolling reduction conditions during roll rotation are constant, making it possible to perform tests in steady plastic working. Using rolls with varying rolling reduction conditions allows testing in unsteady plastic working.

Additionally, hot testing is possible by heating the material to a predetermined temperature in a heating furnace in advance. By changing the distance between the roll 2 and the tool 1, it is possible to change the magnitude of plastic deformation, the pressure acting on the contact area between the tool 1 and the workpiece 3, and the contact area, and also change the rotation speed of the roll 2. By doing so, the relative sliding speed between the tool 1 and the workpiece 3 can be changed.

Furthermore, by making the tool 1 shape simpler, lubricant 6
coating, surface treatment of the tool 10, changing the tool material, and replacing the tool 1 are also facilitated, and tests under various lubrication conditions can be easily performed.

Note that in order to evaluate the friction characteristics over a longer period of time, a long workpiece 3 may be used, or a short workpiece 3 may be rolled in multiple passes. Furthermore, although the rolling blade P is designed to detect the force acting on the roll 2 in FIG. 1, it may also detect the force acting on the tool 1.

Next, the present invention will be explained in more detail using specific examples.
FIGS. 2 to 4 show the configuration of a test machine manufactured by the present inventors, and as shown in FIG. Replace the roll set with the fixed block 11 and install the bearing 18
A tool 13 machined into a plate shape is fixed in the tool holding portion 12 of the fixed block II, and the tool 13 is
A plate workpiece is rolled between the upper roll 14 and the roll housing 1 as shown in FIG.
A compression type load cell 16 is attached to the exit side of the roll 16, and the fixing block 11 as described above is pressed against the load cell 16 to fix the fixing block 11 in the rolling direction. The frictional force acting between the workpiece and the tool 13 located at is detected. The force perpendicular to the rolling direction is detected by a roll reduction blade detection load cell 17 attached to the upper part of the roll housing 15.

An example of a test method and test results for simulating steady plastic working using a cylindrical roll using the test machine of the present invention as described above will be described. Carbon M (0.2%
C) was heated to 1000° C. in an electric furnace. The shape is 15 mm thick, 40 mm wide, and 150 mm long, and the tip has a taper of about 10 degrees to improve the biting property. For the tool 3, alloy steel (5% Cr-1% MO) with a thickness of 2511, a width of 60 m, and a length of 150 n was used, and the distance between the roll 14 and the tool 13 was set to 7 n* (rolling reduction rate of 53%). The test was carried out by driving a roll having a diameter of 130 mm with a DC motor at a rotation speed of 2 Orpm.

Figures 5 and 6 show the test results when water-soluble graphite-based lubricants A and B were applied to the tool surface in advance to a thickness of about 50 μm, and the load cell 17 as a function of the rolling time.
The rolling blade P, which is the output from the load cell 16, the friction force F, which is the output from the load cell 16, and the friction coefficient μ are shown as the calculation results of μ=F/P. That is, in Figure 5,
It can be seen that the friction coefficient during rolling is almost constant and its value is extremely low, indicating that a stable lubrication state is obtained. On the other hand, in FIG. 6, the friction coefficient increases to 0.2 immediately after rolling starts, and the friction coefficient fluctuates little by little during rolling, and the plate material actually seizes on the tool 13 at this point.

As described above, it has been found that the test method according to the present invention using a cylindrical roll can accurately evaluate the friction coefficient and durability of a lubricant, and the seizability of tools and workpieces.

Next, we will describe an example of the test method and test results for simulating unsteady plastic working using eccentric rolls whose rolling reduction rate changes as the rolls rotate.The rolls have a diameter of 130 mm and an eccentricity of 6
．． 5 Dragon was used, and the setting was such that the distance between the roll and the tool could be changed from 211 to 15+u (rolling reduction ratio O to 80%) in half a rotation of the roll. The above A was used as the lubricant, and the other conditions were the same as above. FIG. 7 shows the change in the friction coefficient with respect to the rolling reduction ratio as a result of the test. This figure shows that as the rolling reduction rate increases, the friction coefficient also increases, and the rolling reduction rate is approximately 5.
It can be seen that seizure occurs between the workpiece and the tool at 8%.

As described above, the present invention can evaluate the friction coefficient and durability of the lubricant and the seizure resistance between the tool and the workpiece when the rolling reduction rate changes sequentially in the test method using eccentric rolls. It's obvious. Evaluation under conditions similar to thermal theory can also be achieved by using the cylindrical roll material whose plate thickness changes successively in the longitudinal direction.

The test method has been described above using the test method of the present invention as an example for evaluating lubricants. However, if the test is performed without lubricant, the friction characteristics of the tool material can be evaluated, or the tool can be subjected to surface treatment such as heat treatment or coating with a different material. It is clear that the lubricity of each surface layer can be evaluated individually by testing.

According to the present invention as described in detail, a plate-shaped workpiece is rolled between a rotating rolling roll and a fixed plate-shaped tool, thereby causing large plastic deformation to the workpiece. At the same time, a high pressure is generated at the contact interface between the newly exposed surface of the workpiece and the tool surface, and a relative slip is applied to the workpiece and the tool to prevent the tool and the workpiece during actual plastic working. It is possible to simultaneously detect the force acting perpendicular to the rolling direction and the force acting on the tool parallel to the rolling direction, and from the detected values of both, the true state at the interface between the workpiece and the tool can be determined. By calculating the coefficient of friction of This is a highly effective invention.

[Brief explanation of the drawing]

The drawings show the technical contents of the present invention, and FIG. 1 is an explanatory diagram of the principle relationship of test and measurement in the present invention,
The figure is a front view of the test machine manufactured according to the present invention, FIG. 3 is a side view thereof, FIG. 4 is an elevation view thereof, and FIGS. 5, 6, and 7 are graphs showing the test results. In these drawings, 1 is a tool, 2 is a roll, 3 is a workpiece, 4 is a rolling force detector, 5 is a friction force detector, 6 is a lubricating film, 11 is a fixed block, and 12 is a tool support part. , 13 is a tool, 14 is a roll, 15 is a roll housing, 16 is a load cell for detecting friction, 17 is a load cell for detecting rolling force, and 18 is a bearing. Patent applicant Nippon Kokan Co., Ltd. Inventor Yasushi Soya
Satoshi Hirakawa No. 7
National water rate - (phantom procedural amendment (0 error) Showa &1.10.1ilOs

Claims (1)

[Claims] A plate-shaped workpiece is rolled between a rotating rolling roll and a fixed plate-shaped tool, and an acting force that acts perpendicular to the rolling direction,
Detects both the force acting on the tool parallel to the rolling direction,
A friction lubrication test method characterized by evaluating the friction characteristics at the interface between a tool and a workpiece during plastic working.