JP3264790B2 - Drawing part having irregular cross section 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 drawn part having an irregular cross section used for a track shaft or the like which serves as a guide when a mechanical assembling robot or the like moves. Further, the present invention provides a drawn part having excellent shape accuracy and durability.

[0002]

2. Description of the Related Art The orbital axis for robots is made by rolling medium carbon steel.
It is manufactured by hardening the surface by treatment such as induction hardening in order to form a shape by a combination of the drawing process and improve the wear resistance. However, in each process of manufacturing, deformation of the product in the longitudinal direction such as bending or twisting is unavoidable, and in particular, correction is repeatedly performed after drawing with large deformation. For this reason, the manufacturing process is lengthened, the productivity is significantly reduced, and the cost required for the manufacturing is naturally increased. Originally, it was effective to increase the amount of carbon and obtain a harder surface in order to improve the durability of the raceway shaft, but on the other hand, residual stress at the time of pulling out increased, and after processing At present, the carbon content is generally set to less than 0.6% because the deformation of the product is promoted.

[0003] In addition, since an increase in the amount of carbon increases the load applied to the die at the time of drawing, it is necessary to perform annealing before drawing with a medium carbon material, and the annealing-drawing process is repeated four to five times. The production cost is enormous.
At present, the carbon content has to be less than about 0.6% due to this restriction. Such a situation is not limited to the linear track axis, and is common to drawn parts having irregular cross sections.

As described above, the prior art has complicated processes, low productivity, extremely high production cost, and has to say that the durability is far from the ideal state.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention eliminates the limitation of high carbonization and the occurrence of deformation of a drawn part having a deformed cross section, which was considered to be fatal in the prior art. At the same time, it is intended to drastically eliminate many drawing and annealing steps.

[0006]

According to the present invention, the factor that suppresses the increase in strength is the work hardening of the material, and the factor that increases the drawing deformation and heat treatment deformation is caused by the residual stress of the steel material. With this in mind, while obtaining a product with a sufficiently high strength during heat treatment, the work-hardening is drastically reduced to greatly reduce the resistance when pulling out the orbital shaft, and many annealing processes can be performed. It was clarified that the deformation due to residual stress generated in the product can be suppressed to a minimum.

[0007] The present invention was made based on the above findings, and its gist in mass% C: 0.3
~ 1.0%, Si: 0.6 ~ 1.3%, Mn: 0.2 ~
1.5%, P ≦ 0.02%, S ≦ 0.1%, Al: 0.
From 0.1 to 0.035%, or
i: 0.05 to 5.0%, B: 0.001 to 0.004
%, N: 0.002 to 0.012 %, Mo: 0.05 to
It has containing one or more 0.20%, the balance being iron及<br/> beauty unavoidable impurities, 0.3 as graphite therein
5 to 1.0%, the average particle size of the graphite is 4 μm or less, the number of particles is 3000 particles / mm ² or more, and the surface layer portion has a part or all of an induction hardened structure. Manufacturing a drawn part and a drawn part
A steel material having the above chemical composition,
A method for producing a drawn part having a deformed cross section, characterized in that after forming by appropriately combining cutting and grinding steps, a surface layer is subjected to quenching treatment by high frequency in order to impart surface strength.

[0008]

The present invention will be described below in detail. First, a description will be given of the chemical components of the steel material targeted by the present invention and the reasons for limiting the chemical components. The reason why the carbon content is set to 0.3% or more is that if the carbon content is less than 0.3%, abrasion due to sliding with other components increases,
The reason for setting the content to 1.0% or less is to prevent burning cracks due to heat treatment.

Since Si has a small bonding force with carbon atoms in the steel and is effective for graphitization, at least 0.6% is necessary. If it exceeds 1.3%, the ferrite phase becomes hard and the cold workability deteriorates. Therefore, the upper limit was set to 1.3%. Mn requires an amount obtained by adding an amount necessary for fixing and dispersing sulfur in steel as MnS, and its lower limit is 0.2%. On the other hand, if the amount of Mn is large, it is difficult to graphitize, so the upper limit is set to 1.5%.

Since P impairs hot workability, the upper limit is set to 0.0.
2%. Since S impairs cold workability, S is set to 0.1% or less. Al serves as a deoxidizing material for molten steel and adjusts the crystal grain size, so it needs to be added in an amount of 0.01% or more. If the addition is excessive, the cold workability is impaired, so the upper limit was made 0.035%.

B is preferably added because it forms BN in the steel and promotes graphitization. The lower limit at which the effect is obtained is 0.001%, and the effect is saturated at 0.004%.
%. At least 0.002% of N is required to form BN, but if it is too large, it causes problems such as aging.
012% was made the upper limit.

Ni is effective in securing the strength, and is preferably added at 0.05% or more. However, if the strength at the time of cold working is too high, working becomes difficult. Therefore, the upper limit is set to 5.0%. Mo is effective for precipitating graphite in the ferrite grains, and is desirably added at 0.05% or more. If the amount of addition is large, the hardness of ferrite and the like increases, so the upper limit was set to 0.20%.

Next, the graphite content and the graphitization rate will be described. Inside to the graphite mass content of 0.35% or more, and the drawing die life is decreased in the processing of pre-heat treatment is less than this, the machining accuracy is lowered,
Furthermore, the strain after heat treatment is increased. On the other hand, the upper limit of the internal graphite content is equal to that of carbon. Further, when graphite having an average particle size of 4 μm or less and 3000 particles / mm ² or more is contained, not only is the internal toughness high, which is effective for preventing breakage, but also such a material rapidly diffuses carbon during heat treatment. High quenching properties do not cause defects such as incomplete quenching.

On the other hand, in the production of the above-mentioned parts, it is effective to use a rod-shaped material having a graphitization ratio of carbon of 35% or more in a suitable combination of cold drawing and grinding. To graphitization ratio 35% or more, and is this less than the material does not soften sufficiently, due to the machinability is not high. Next, in the present invention, the bar-shaped steel material is drawn, cut, and formed by appropriately combining the grinding processes.After that, in order to impart surface strength, a part or all of the surface layer portion is quenched by high frequency to obtain a high frequency quenched structure. Give. Induction hardening process conditions may secure the surface strength required for the product is of course, pulling property, machinability, it shall also considered the conditions and cost of heat treatment. For the induction hardening treatment conditions satisfying the above various conditions, the frequency to be used is optimally 3 KHz which is usually adopted, and the quenching temperature range is 8 KHz.
00-900 degreeC is desirable. If the temperature is lower than 800 ° C., an incompletely quenched state occurs, and a sufficient quenched structure cannot be obtained. on the other hand,
If the temperature exceeds 900 ° C., excessive quenching occurs and the hardness becomes too high, resulting in brittleness. On the other hand, drawing, cutting time and cost increase, and it is not economical. It is desirable that the induction hardening temperature range be between 820 and 880 ° C. The range of application of the induction hardened structure varies depending on the desired product shape, but it is a part or the whole of the outer surface.

For applications where the strength of the non-quenched portion is insufficient if the carbon remains in the graphite state, normalizing may be performed before induction hardening to convert the carbon into carbide. Further, conditions for imparting the desired shape accuracy and durability in the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a track shaft which is one embodiment of the present invention. A part of the surface layer has an induction hardened portion 1 hatched, and is constituted by a non-quenched portion 2. The hardened portion 1 has a martensitic structure and has a non-quenched portion 2.
Is at least partially in the graphite state.

A ball sliding groove 3 is arranged on a part of the surface, and a hatched portion 1 is hardened. The quenching of No. 1 is for suppressing the deformation, and is naturally omitted when the quenching is small. After the quenching, tempering can be performed as needed. The feature of the present invention is that carbon is in a graphite state before quenching, so that it is extremely soft as compared with a case in a normal carbide state, and has very little work hardening by drawing. Without a complicated cross-section, it is possible to draw out a complicated cross section, and since no large residual stress is generated at the time of drawing, bending and torsion are remarkably reduced.

According to the present invention, even during the heat treatment of the track shaft, the generation of residual stress is small, which is advantageous. Furthermore, from the above, if the same degree of bending and torsion is tolerated, the surface strength can be increased more easily by adding high carbon than before, and a track shaft with improved durability can also be obtained. You can. The orbital shaft having the above-described configuration has much less bending and torsion than any conventional one through any process of the heat treatment for drawing, so that a high-precision one at a level that was difficult to reach conventionally can be extremely reduced. Can be easily obtained.

Such an orbital shaft can be manufactured by preliminarily graphitizing carbon in a raw material stage, drawing the carbon into a required cross-sectional shape, and subjecting the ball sliding portion to high-frequency heat treatment. Although the example of the linear track axis has been described here, the present invention is not limited to a mechanical part having a deformed cross section processed by drawing, in which a sliding portion with another part such as a ball is induction hardened. The same applies.

[0019]

Next, the effects of the present invention will be described with reference to examples. The raw material provided for the present invention contains the chemical components shown in Table 1, and was rapidly cooled at a cooling rate of 10 ° C./s immediately after being formed into φ35 mm by hot rolling. This was further annealed at 650 ° C. for 3 hours to graphitize carbon.

[0020]

[Table 1]

These materials were drawn out to produce a linear orbit shaft. The outline of the cross section after drawing is almost 25mm x 25mm
It has a square shape and is partially carved with a ball groove. Table 2 shows the relationship between the manufacturing process and the heat treatment process when the linear orbital shaft was manufactured using the materials shown in Table 1 and the drawability, the carbon form inside the product, and the amount of bending.

[0022]

[Table 2]

According to the method of the present invention, the present inventions 1 to 6 shown in Table 2
In any of the combinations shown in (1), molding into the final shape was possible by a single drawing. In all of the inventions 1 to 6, at least a part of the carbon in the material was graphite. Next, the linear orbital axes of the methods 1 to 6 of the present invention, which were formed by drawing, were immediately subjected to a frequency of 3 kHz and a quenching temperature of 820 to 880 ° C.
Induction temperature hardening treatment was performed in order to impart an induction hardened structure to the outer surface of the sliding portion of the raceway shaft in the temperature range described above. Invention 1
Nos. 3 to 3 were subjected to induction hardening treatment as they were after the drawing, so that the graphite remained except for the quenched part. However, in the present inventions 4 to 6, carbon was cementitized by normalizing after the drawing, and almost no graphite was formed. Does not remain.

In Comparative Example 1, if the combination of spheroidizing annealing and drawing was performed three times using steel type 4, the same shapes as those of Inventions 1 to 6 could be obtained. However, Comparative Example 2
In the case where the material having a cementite structure was directly omitted into the final shape using steel type 1 without annealing, the work hardening was large and the die was severely seizure, so that production was impossible. Comparative Example 3 is steel type 2 having a carbon content of 0.65%.
Was used to perform spheroidizing annealing, and thereafter, an attempt was made to obtain the final shape by a single drawing. However, die drawing occurred at the time of drawing, making processing impossible. Comparative Example 4 has a carbon content of 0.9.
When 8% steel type 3 was used, spheroidizing annealing and drawing were repeated three times to obtain the final shape. However, since the material was hard, die seizure occurred during the third drawing,
After all it became impossible to process.

On the other hand, one of the orbital axes after induction hardening
Table 2 also shows the amount of bending per m. The bending in Comparative Example 1 is particularly large, and greatly exceeds the management target bending amount of 0.40 mm per 1 m, and correction is inevitable. Comparative Examples 2 to 4 were not able to be processed by drawing, and the experiment was stopped at that time. On the other hand, in the present inventions 1 to 3, which were processed using a material containing graphite and were induction hardened in a state containing graphite inside, the bending was 0.22 to 0.2.
In the present invention 4 to 6 in which only a small bend of 5 mm / m and cementing of carbon by normalizing before induction hardening, the bend is within 0.27 to 0.34 mm,
No correction is required and the effect is clear.

As a result, in the method of the present invention, the drawing cost is about 7%.
A reduction of 0% and a total processing cost of about 50% were achieved.

[0027]

According to the present invention, a part having a deformed section such as a track axis used for a robot for machining and assembling and processing a lot of man-hours centering on drawing is reduced to a much shorter time. The present invention provides a part which can be manufactured in a process with high accuracy and has excellent wear resistance, and is obviously of great industrial value.

[Brief description of the drawings]

FIG. 1 is a perspective view including a cross section of an orbital shaft according to an embodiment of the present invention.

[Explanation of symbols]

 1: Hardened part 2: Non-hardened part 3: Ball sliding groove

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C21D 9/04 C21D 9/04 A C22C 38/06 C22C 38/06 (56) References JP-A-6-323399 (JP, A JP-A-4-311546 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00 301 C22C 38/06

Claims (3)

(57) [Claims] In 1. A mass% C: 0.3~1.0%, Si:
0.6-1.3%, Mn: 0.2-1.5%, P ≦ 0.
02%, S ≦ 0.1%, Al: 0.01 to 0.035%
Wherein the balance of iron and unavoidable impurities, containing from 0.35 to 1.0% as graphite inside, the graphite
When the average particle size is 4 μm or less and the number of particles is 3000 particles / mm ² or more
A drawn part having an irregular cross section , wherein at least a part of the surface layer has an induction hardened structure. In 2. A mass%, further, Ni: 0.05 to
5.0%, B: 0.001 to 0.004%, N: 0.0
02 to 0.012 %, Mo: 0.05 to 0.20% 1
2. The composition according to claim 1, wherein said composition contains at least one species.
A drawn part having the described irregular cross section. 3. A drawn part according to claim 1 or 2 is manufactured.
A method of forming a rod-shaped steel material comprising the component according to claim 1 or 2 and having a graphitization ratio of carbon of 35% or more by appropriately combining drawing, cutting and grinding, and then forming at least the surface layer A method for producing a drawn part having an irregular cross-section, characterized by imparting surface strength by quenching.