JP3227721B2 - Method and apparatus for evaluating the performance of a forging lubricant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating the performance of a lubricant used for forging metals, particularly steel, and an apparatus used for carrying out the evaluation.

[0002]

2. Description of the Related Art Various lubricants have been used in hot, warm or cold forging and working of metals such as steel. Various methods for evaluating lubrication performance have been devised to determine the optimal lubricant for each case. Among them, the ring compression test method, forward extrusion method, backward extrusion method, etc. It is widely used because it can be evaluated under conditions close to. The advantage of the ring compression test method is that the absolute value of the performance of the lubricant between the material and the mold can be evaluated, but the expansion ratio of the surface area on the lubricated surface (the surface area of the surface added with the new surface generated by forging, The ratio to the old surface area) is at most about 3 and forging such as backward extrusion where the surface area expansion ratio reaches 10 in practical working is not an appropriate evaluation method.

[0003] The forward extrusion method is a method of judging from the magnitude of the load at the time of forward extrusion and the degree of damage to the material surface after molding, and there is a dissatisfaction that the latter can only be qualitatively evaluated.

[0004] The backward extrusion method itself is a kind of molding method rather than a test method, and can be said to be an optimal test method for evaluating a lubricant when molded by this method. However, on the other hand, in order to obtain reliable results, tools to be used for actual machining should be used, which is an easy-to-use evaluation method in terms of increased tool manufacturing costs and reproducibility in repeated tests. Not really.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the evaluation technology of a lubricant used in forging, to make it easy to repeat a test, to obtain high reproducibility, and to make the surface area expansion ratio close to practical conditions. And a technique for quantitatively evaluating lubricant performance.

[0006]

The method for evaluating the performance of a lubricant used for forging a metal according to the present invention is shown in FIGS.
As shown in the figure, a cylindrical metal piece is placed on a die having a funnel-shaped inner surface shape in which an upper funnel part slightly inclined with respect to the horizontal plane and a lower funnel part greatly inclined are connected by a transition part with a radius. After applying a load under application of a lubricant, pressing the metal piece into the die to form a spike according to the die shape, and then performing an operation of projecting the formed metal piece from a direction opposite to the pressing direction, It consists in determining the performance of the lubricant based on the values of the load required to achieve a certain indentation, the height of the formed spikes and the load required for protrusion.

An apparatus for evaluating the performance of a forging lubricant according to the present invention comprises a die (1) having a funnel-shaped inner surface, and a pressing head for pressing a metal piece (7A) into the die to form a spike (71). (2) and an ejector pin (3) for projecting the molded article (7B) having the formed spike from the tip of the spike is incorporated in the mechanism of the compression testing machine, and the inner surface shape of the die is slightly inclined upward with respect to the horizontal plane. The funnel part (11) and the greatly inclined lower funnel part (12) are connected by a rounded transition part (13), and the pushing head (2) has a concentric groove on the surface in contact with the metal piece. And a load cell (5) for measuring a projecting load of an ejector pin in addition to a load cell (4) for measuring a processing load of a pressing head.

In the shape of the die shown in FIG. 2, the inclination of the funnel portion inclined at a small angle with respect to the horizontal plane is represented by an angle θ ₂ , the inclination of the funnel portion having a large inclination is represented by an angle of inclination θ ₁ with respect to the vertical plane, and the transition portion is formed. When the value of R is represented by R, the following ranges are preferable. θ ₂ = 1 to 15 °, especially 10 ° θ ₁ = 1 to 5 °, especially 3 ° R = 0.5 to 10 mm

[0009]

When the indentation test is performed according to the present invention as shown in the upper part of FIG. 3, when the lubricant (8) works effectively,
Since the metal piece (7A) is deformed while sliding on the funnel-shaped surface of the die (1) with a small friction, a high spike (71) is formed as shown in the lower left of FIG. As shown in the lower right part of the figure, the metal piece is simply crushed into a shape protruding laterally, and the spike (71)
Is relatively low. Therefore, the lubrication performance can also be evaluated by the height of the formed spike. Next, the load required when ejecting with the ejector is also one of the properties of the lubricant.

It is easily understood that the shape of the die is important for the evaluation of the lubricating performance according to the above principle. In particular, the angle θ ₁ defines how the spikes grow. Therefore, it must be determined appropriately. This will be described later with reference to the embodiment.

The concentric grooves on the surface of the pushing head are
It helps prevent the metal pieces from spreading laterally and helps to form spikes, which is also readily apparent.

[0012]

Respect decisions EXAMPLES die shape and country theta ₁ described above was carried out by numerical analysis the experiment following conditions.

Θ ₁ = 1 °, 3 °, 5 °, θ ₂ = 10 ° (constant), R = 5 mm Shear friction coefficient = 0.0, 0.15, 0.30, 0.6
0,0.90 Metal to be processed: SUS304 and DSK2U (Stainless steel for cold plastic working equivalent to SUSXM7 of AISI, steel symbol of Daido Specialty Steel) Test piece: diameter 25 mm x height 30 mm Pressing amount: mold gap (Lg) up to 3.4 mm As the data for the numerical analysis, the data of the stress-strain curve of the compression test conducted at 200 ° C. and 400 ° C. for the above two metals was used.

FIG. 4 is a plot of the relationship between the obtained spike height (Hs) and the indentation load with respect to each shear friction coefficient. From these results, it was concluded that θ ₂ = 3 ° is the most suitable die shape for which the magnitude of the shear friction coefficient reflects the change in spike height and is convenient for evaluating the lubrication performance.

Therefore, a die of θ ₂ = 3 ° was manufactured, and the test apparatus shown in FIG. 1 was assembled. Using the above DSK2U as a metal to be processed, it was processed into a test piece having a diameter of 25 mm and a height of 30 mm. On their lower surfaces, the lubricating coatings of Table 1 were applied and dried or not applied, and used in combination with the auxiliary lubricating oils of Table 2.

Table 1 Lubricating coating composition A MoS ₂ (paste of alcohol dispersion of powder) BK ₂ SO ₄ (aqueous solution) The indentation test was performed using the combinations of the lubricating film and the auxiliary lubricant shown in Table 3 at 200 ° C, 400 ° C and 50 ° C.
Performed at 0 ° C. The mold gap Lg is 2.7
3 mm.

[0017] Table 3 lubricating coating auxiliary lubricant No. teeth A B None I II III 1 ○ ○ 2 ○ ○ 3 ○ ○ 4 ○ ○ 5 ○ ○ 6 ○ ○ 7 ○ ○ 8 ○ ○ 400 indentation load at ℃ Fig. 5 shows the relationship between
FIG. 6 shows the relationship between the indentation load and the ejector load. From these results, it was concluded that MoS ₂ -based lubricant is appropriate for warm forging of DSK2U, and that it is better to use it alone without an auxiliary lubricant. A high spike can be formed even with a low load, so good slippage occurs during processing between the material and the forging die. Also, since the ejector load is low, there is no seizure between the die and the molded product after molding, leaving a residual coating. This is because the amount is large.

In fact, when this lubricant was used for backward extrusion of DSK2U, a molded article having a more beautiful appearance was obtained than when other lubricants were used.

[Comparative Example] When the lubricant performance was tested for each of the combinations 1 to 8 by the ring compression test method (55% upsetting), the results shown in FIG. 7 were obtained. According to the data in the figure, the test method of the present invention and the No. 1 which achieved a good result in the practical application were obtained. No. 7 has a high coefficient of shear friction and cannot be evaluated as being superior to other lubricants.

[0020]

According to the lubricant performance evaluation method of the present invention,
Performance can be evaluated by forging under conditions close to practical working conditions, so that more accurate conclusions can be made than conventional methods. The apparatus to be used does not have a complicated structure, and a single tool can be used commonly for a wide range of metals and lubricants, so that the cost does not increase.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a main part of a performance evaluation device for a forging lubricant of the present invention.

FIG. 2 is a longitudinal sectional view showing details of a die portion of the apparatus of FIG. 1;

FIG. 3 is a cross-sectional view showing a state of spike formation due to a difference in a shear friction coefficient of a metal piece when forging (injection molding) is performed using the apparatus of FIG.

FIG. 4 is a graph plotting the relationship between spike height and indentation load by numerical analysis performed to determine a die shape.

FIG. 5 is a graph showing the relationship between spike height and indentation load, which is data of the example of the present invention.

FIG. 6 is a graph showing the relationship between the protruding load and the indentation load, which is also data of the example.

FIG. 7 is a graph showing the relationship between the shear friction coefficient and the temperature when various lubricants were evaluated by the ring compression test method, which is data of a comparative example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Die 11 Upper funnel part 12 Lower funnel part 13
Transition part 2 Push head 3 Ejector pin 4 Load cell (for measuring push load) 5 Load cell (for measuring protrusion load) 7A Metal test piece 7B Molded product 71 Spike 8 Lubricant Lg Mold gap Hs Spike height

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B21J 3/00, 13/02 G01N 3/40

Claims (2)

(57) [Claims] 1. A method for evaluating the performance of a lubricant used for forging a metal, wherein an upper funnel portion slightly inclined with respect to a horizontal plane and a lower funnel portion greatly inclined with respect to a horizontal plane are connected by a curved transition portion. After placing a cylindrical metal piece on a die having a funnel-shaped inner surface shape, applying a load under the application of a lubricant, pressing the metal piece into the die, forming a spike according to the die shape,
Perform the operation of pushing out the formed metal piece from the direction opposite to the pushing direction, and lubricate based on the value required to achieve a constant pushing amount, the height of the formed spike, and the load required for projecting A method comprising determining the performance of an agent. 2. An apparatus for evaluating the performance of a lubricant used for metal forging, comprising: a die (1) having a funnel-shaped inner surface shape; and a metal piece (7A) pushed into the die to spike (71). A press head (2) for forming a spike, and an ejector pin (3) for projecting a molded product (7B) having the formed spike from the tip of the spike are incorporated in a mechanism of a compression tester, and the inner surface shape of the die with respect to a horizontal plane The upper and lower funnels (11) and (12) are connected by a rounded transition (13), and the pushing head is concentric with the surface in contact with the metal piece. Device equipped with a load cell (5) for measuring the projecting load of the ejector pin in addition to the load cell (4) for measuring the processing load of the pushing head. .