JP3387580B2 - Rubber track core metal and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber crawler core bar and a method for manufacturing the same, and particularly to a rubber crawler core bar suitable for use in a site where high mechanical properties are required such as construction machinery, and its manufacture. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, the following is known as a core metal for rubber crawler belts used for construction machines and the like, which is required to have mechanical properties such as wear resistance and strength, and a manufacturing method thereof. (A) After processing bar steel such as carbon steel or low alloy steel into a predetermined size such as by cutting, forming it by hot forging, heating it again to a predetermined temperature and then quenching (reheating quenching), tempering and rubber crawler Use core metal. In this case, the hardened part structure of the core metal is mainly tempered martensite. (B) A steel bar such as a carbon steel or a low alloy steel is processed into a predetermined size such as by cutting, hot forged, directly quenched, and tempered to obtain a rubber crawler core bar. The hardened part structure of the core metal is mainly tempered martensite.

[0003]

However, the above-mentioned prior art has the following problems. That is, the above item (a) requires a large number of steps, requires a lot of energy and time, and is uneconomical. In addition, (B) reduces cost because reheating at the time of quenching is unnecessary as compared with the above (A), but is still uneconomical because of the large number of steps.

The present invention focuses on the above-mentioned problems of the prior art, reduces the number of steps and improves the cost, and the core metal for rubber crawler track whose quality such as mechanical characteristics is equal to or higher than the conventional one, and its manufacturing method. The purpose is to provide.

[0005]

In order to achieve the above object, in a rubber crawler belt core metal according to the present invention, a first aspect of the present invention is a carbon steel in which a hardened portion is formed by quenching from the surface to the inside. In a rubber crawler core made of steel such as low alloy steel, the vertical cross-section thickness of the uncured part formed inside the high load part in the longitudinal center part of the core bar is above and below the high load part. 0.3 to the cross-sectional thickness in the direction
It is 0.65, and the structure of the hardened part in the high load part is mainly composed of martensite.

Further, in the method for producing a rubber crawler core bar according to the present invention, the second invention is: (a) a first step of processing a steel-based material into a predetermined dimension; and (b) heating the processed material to a predetermined temperature. After that, the second step of forming by hot forging, (c) After hot forging, a hardened portion is formed from the surface of the forming material toward the inside without reheating , and the core metal of the forming material is formed .
The vertical cross-sectional thickness of the uncured portion formed inside the high load portion at the longitudinal center is the upper and lower portions of the high load portion.
A third step of directly quenching a molding material having a thickness of 0.3 to 0.65 with respect to the cross-sectional thickness in the opposite direction, and the above-mentioned steps, which is a method for producing a rubber crawler core bar. The rubber crawler belt core metal and the method for manufacturing the same according to the present invention have the above-described configurations.

[0007]

The operation of the present invention having the above construction will be described. The surface of the core metal for rubber crawler belt has a hardened part mainly composed of martensite structure by quenching, so that it has required mechanical properties such as wear resistance and strength. In addition,
The uncured ratio, which is the ratio of the vertical cross-sectional thickness of the uncured portion formed inside the high-load portion at the central portion in the longitudinal direction to the predetermined vertical cross-sectional thickness of the high-load portion, is 0.3 to 0. 6
Since it is 5, high toughness can be obtained by the contribution of the uncured portion. Furthermore, by the appropriate composition ratio of the hardened part and the uncured part, the bending toughness required for the entire rubber crawler core metal,
Flexural rigidity is obtained. The uncured rate is 0.3 to 0.6
By setting it to 5, inexpensive materials such as carbon steel and low alloy steel can be used.

Next, a characteristic of the method for manufacturing a rubber crawler core bar is three steps of a step of processing a steel material to a predetermined size, a hot forging step and a direct quenching step, and the tempering step in the conventional method is omitted. The manufacturing cost and the like are improved. Further, direct quenching with an uncured rate of 0.3 to 0.65 is
Hardening conditions can be set over a wide range, and process control is easy.

[0009]

Embodiments of a rubber crawler belt core metal and a method of manufacturing the same according to the present invention will be described below in detail with reference to the drawings. An outline of a rubber crawler track for a construction machine or the like to which the present invention is applied is shown in FIG. The rubber track 10 includes a sprocket 2 and an idler 3 provided on both ends of the track frame 1.
It is wound around the outer periphery and runs while meshing with the sprocket 2, and a high load such as the weight of the vehicle body is applied through the lower rolling wheels 4 provided in the lower portion of the track frame 1. The structure of the rubber crawler belt 10 is shown in FIG. 3 which is a cross section taken along line XX in FIG. 2, but the inside of the endless rubber shoe 11 has a core.
The longitudinal direction of the gold 12 should be the width direction of the rubber track 10.
In addition, the core metal 1 is equipped with a large number of metal cores 12 embedded therein.
A large number of steel cords 13 continuous in the circumferential direction are embedded in the rubber shoe 11 in the vicinity of 2, for example.

During operation of the construction machine such as running, the core metal 12 of the rubber crawler track 10 slides while meshing with a plurality of sprocket teeth 2a provided on the outer periphery of the sprocket 2, and the rolling surface 14 ( 14a, 14b) receives intermittent high load from the lower wheel 4. Therefore, since there are two rolling surfaces 14a and 14b, the substantially central portion of the cored bar 12 near the line 15 is the high load part of the cored bar 12,
High stresses, for example high bending stresses, occur.

Next, the core metal for a rubber crawler belt manufactured by the manufacturing method of the present invention will be described based on steps. Material S30 which is a medium carbon low alloy steel used for the core metal in this example.
Table 1 shows the main components of BC.

[0012]

[Table 1]

In the first step, the round bar material of the material S30BC is cut into a predetermined size by shearing to obtain a processed material. Next, in the second step, 1100 to 1100 in an electric furnace or the like.
A processing material heated to 1300 ° C. is formed into a predetermined shape and size by hot forging to obtain a forming material. Then, the third
In the process, the forming material by hot forging is put in a water tank without being reheated and directly quenched. The main conditions for this quenching are a quenching temperature of 965 ° C., a quenching agent of water, and a pulling temperature after cooling of 155 ° C.

The hardness pattern of the cross section of the core metal obtained by the above steps is shown in FIG. In FIG. 1, (a) of FIG.
The longitudinal direction of the cored bar 12 is shown in the left-right direction of FIG.
It has the same cross section as the core metal 12 shown in FIG.
Is the YY cross section in (a), and is the longitudinal direction of the cored bar 12.
The cross section of the central portion is shown. The core metal 12 has a hardened portion 21 and an uncured portion 22 in a schematic configuration based on the cross-sectional hardness distribution. Here, the hardened portion 21 is a portion having a hardness HRC of 45 or more, and the uncured portion 22 is a portion having a hardness HRC of less than 45. FIG. 4 shows a cross-sectional hardness distribution of the cored bar 12 taken along the line 23 in FIG. 1B, which is an example of the high load portion of the cored bar 12.
It is the measurement result between the point P1 and the point P2 of the cored bar 12 (see FIG. 1B). A hardened part 21 is formed by quenching from the surface toward the inside, and an uncured part 22 is formed inside. ing. Here, the longitudinal direction of the cored bar 12 which is a high load part
The vertical cross-sectional thickness of the central portion is t ₀ , and the uncured portion 22
Assuming that the vertical sectional thickness is t ₁ , the uncured rate α = t ₁
/ T ₀ = 0.61. In addition, the observation result of the cross-sectional structure,
The hardened part 21 is mainly composed of martensite, and the uncured part 22
A little martensite was observed in ferrite and pearlite.

Since the rubber crawler belt core metal 12 slides on the lower roller 4 and the sprocket teeth 2a (see FIG. 2), wear resistance is required and the rubber crawler belt 10 has a predetermined strength. In order to obtain rigidity, bending toughness and bending rigidity are required at the same time. Among these mechanical properties, in order to evaluate bending toughness and bending rigidity, which are important, the performance of the cored bar 12 was examined by the three-point bending test method shown in FIG.
The test method is as follows.
1b) and then press the jig 32 to the center of the core 12.
Thus, the predetermined load P is applied downward, and then the load P is removed. The evaluation method and criteria are before the load,
The permanent deformation amount δ, which is the change amount of the lower surface 33 of the cored bar 12 after removing the load P, is equal to or less than the allowable limit deformation amount, and the cored bar 12 is not broken. The core metal 12 of this embodiment is
It was found that the permanent deformation amount δ was 2.9 mm (below the allowable limit deformation amount), there was no breakage, and it passed.

Although one embodiment of the present invention has been described in detail,
Various conditions for direct quenching were selected, and the cored bars 12 having different uncured rates α were evaluated. The uncured rate α was obtained by varying the cooling capacity, for example, adding a commercially available coolant to the cooling water and adjusting the cooling time. Except for changing the conditions of this direct quenching, it is the same as the above embodiment. With respect to the cored bar 12 obtained in the above embodiment and this embodiment, FIG. 6 shows the relationship between the uncured rate α and the permanent deformation amount δ. From FIG. 6, when the uncured ratio α is larger than 0.65, that is, when the uncured portion 22 has an excessively large cross-sectional thickness, the bending rigidity is insufficient and the permanent deformation amount δ exceeds the allowable limit deformation amount. Becomes On the other hand, when the uncured rate α is less than 0.3, that is, when the cross-sectional thickness of the uncured portion 22 is too small, the bending rigidity is large and the permanent deformation amount δ is equal to or less than the allowable limit deformation amount, but the bending toughness is small. Breakage occurs due to lack of As a result, when the uncured rate α falls within the range of 0.3 to 0.65, the permanent deformation amount δ is equal to or less than the allowable limit deformation amount, and the core metal 12
It turned out that there was no breakage. Therefore, the uncured rate α
It was clarified that the range of 0.3 to 0.65 satisfies the required mechanical characteristics even for the core metal for rubber crawler belt, which has a very high load such as construction machinery.

As is apparent from the above-mentioned embodiments, in the method of manufacturing a rubber crawler core metal, a hardened layer is formed on the surface of the high load portion and an uncured portion is formed inside, and the uncured rate α Is 0.3 to 0.65, it is possible to omit the tempering step after direct quenching.

Although the core metal for a rubber crawler belt and the method for manufacturing the core metal have been described in detail as the embodiments according to the present invention, the present invention is not limited to these embodiments. That is, the material may be carbon steel or the like which is normally used in addition to low alloy steel, and the means for processing to a predetermined size may be various types of machining, electric discharge machining or the like. The material to be processed may be heated by equipment other than the electric furnace, for example, a gas furnace, a high frequency heating furnace, or the like, and cooling may be performed by a cooling water spray method or the like. The heating temperature or the direct quenching temperature is not limited to 1100 to 1300 ° C. or 965 ° C., and an appropriate temperature may be selected depending on the type of material, heat loss during hot forging and the like. Furthermore, as a high load part,
The evaluation was made at the substantially central portion of the core metal, but if the high load portion is different from the substantially central portion due to an unbalanced load or the like, the different portion is the high load portion. After direct quenching, the core metal will be finished,
If necessary, the scale attached to the core metal may be removed by shot blasting or the like.

[0019]

Since the present invention is constructed as described above, it has the following effects. Processing of the material to the specified size, hot forging and direct quenching 3
Since the core metal can be manufactured in the process, the tempering process is omitted, the tempering furnace is not required, and the total manufacturing time is shortened, so that the manufacturing cost is improved. The material used here may be low alloy steel such as carbon steel or boron steel, that is, low cost material. Next, the uncured rate in the high load portion of the core metal is in a wide range of 0.3 to 0.65, various direct quenching conditions can be set, the process according to the equipment can be selected, and the process control can be performed. Is also easy. Further, since the uncured ratio of the high load portion of the core metal is 0.3 to 0.65, high toughness is obtained due to the contribution of the uncured portion, and by an appropriate composition ratio of the cured portion and the uncured portion, The required bending toughness and bending rigidity can be obtained as the core metal as a whole.

[Brief description of drawings]

FIG. 1 is a diagram showing a hardness pattern of a cross section of a cored bar according to the present embodiment.

FIG. 2 is a schematic view of a rubber crawler belt according to the present invention.

FIG. 3 is a sectional view taken along line XX in FIG.

FIG. 4 is a sectional hardness distribution diagram of a cored bar according to the present embodiment.

FIG. 5 is a diagram showing a three-point bending test method according to this example.

FIG. 6 is a diagram showing a relationship between an uncured rate α and a permanent deformation amount δ according to the present embodiment.

[Explanation of symbols]

10 rubber tracks 12 core metal 21 Curing part 22 Unhardened part α uncured rate δ Permanent deformation

Claims (2)

(57) [Claims] 1. A rubber crawler metal core bar (12) made of steel such as carbon steel or low alloy steel, in which a hardened part is formed by quenching from the surface toward the inside, wherein the core bar (12)
On the uncured portion is formed in the high-load portion of the longitudinal center vertical cross-sectional thickness of the (22) (t ₁₎ is the high-load portion
Downward cross-sectional thickness (t ₀₎ with respect to a 0.3 to 0.65, and the rubber crawler belt tissue hardened part of the high load part (21) is characterized in that it is a martensite mainly Core metal. 2. (a) a first step of processing a steel-based material to a predetermined size; (b) a second step of heating the processed material to a predetermined temperature and then forming it by hot forging; (c) after hot forging , Uncured, which forms a hardened part from the surface of the molding material to the inside without reheating , and which is formed inside the high load part in the longitudinal central part of the core metal (12) of the molding material Part (22) vertical cross-sectional thickness (t
_1), a third step of performing direct quenching of the molding material to be 0.3 to 0.65 with respect to the vertical direction of the cross-sectional thickness of the high-load portion (t _0), and characterized by having the above step A method for manufacturing a rubber crawler core metal.