JPH10286617A - Production of hollow stabilizer bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for a hollow stabilizer bar for an automobile light in weight, resistant to large load and excellent in fatigue strength. SOLUTION: In a method to produce the hollow stabilizer bar, a hollow billet 2 is produced by machining from a billet 1 made of an alloy steel having excellent hardenability and high strength such as a spring steel, the hollow billet 2 is induction heated and then is subjected to a glass lubrication treatment by a glass lubricant of a viscosity η (poise) satisfying an equation of 150<=η<=91.4ρ+330.1 (where, ρ is deforming resistance of material at hot extrusion (kgf/mm<2> )), extrusion forming is conducted with preventing surface decarfurization of the hollow billet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a hollow stabilizer bar mounted on a vehicle in order to suppress a roll of the vehicle body during a turn.

[0002]

2. Description of the Related Art Generally, a so-called stabilizer, which has a function of reducing rolling of a vehicle body during turning of a vehicle and improving running stability and riding comfort, is attached to a suspension arm of a wheel. This stabilizer is
In recent years, hollowing has been promoted to reduce the weight of a vehicle body. At present, an electric resistance welded steel pipe or a hot finished seamless steel pipe is used as a material for the hollow stabilizer. This electric resistance welded steel pipe has a lower fatigue strength at the weld bead portion than at other portions.
As disclosed in Japanese Patent Publication No. 37, it is necessary to arrange along the curve where the curvature of the weld bead portion becomes the maximum or the minimum and obtain the same fatigue strength as that of the general portion.

On the other hand, since a hot-finished seamless steel pipe is hot-rolled and formed by a Mannesmann-type pipe manufacturing method, there is a problem that, among linear flaws and the like, the outer surface properties and decarburization deteriorate fatigue strength. A curved portion as disclosed in JP-A-54-118026 is formed to be thicker than an intermediate portion of a torsion portion to reduce the stress of the curved portion.
As disclosed in Japanese Patent Publication No. 66837, it is necessary to prevent a decrease in fatigue strength by polishing a curved portion to remove surface defects.

[0004]

As described above, the hollowing of the stabilizer bar has been promoted along with the reduction in the weight of automobiles.
In order to compensate for the low fatigue strength of the weld bead portion of the electric resistance welded steel pipe as disclosed in Japanese Patent Publication No. 137, consideration must be given to the product manufacturing process, which is a factor of lowering the stability of the product quality. Also, reducing the weight of the stabilizer bar leads to the need for higher strength of the material, but in order to increase the strength,
For example, a steel type having excellent hardenability such as spring steel is required. However, in the case of a welded steel pipe, a tendency to cause quenching cracks at a joint is increased, and production becomes difficult. Further, in the case of a welded steel pipe, there is a limit to the wall thickness, and it may be difficult to cope with the wall thickness to secure a predetermined strength.

[0005] As described above, in the case of a hot-finished seam-free steel pipe manufactured by the conventional Mannesmann-type pipe manufacturing method, Japanese Patent Laid-Open Publication No.
As disclosed in Japanese Unexamined Patent Publication No. 4-118026 and Japanese Unexamined Patent Publication No. Hei 7-266837, it is necessary to perform predetermined processing and care on the stabilizer bar to prevent a decrease in fatigue strength, and this also requires stability of product quality. Is a factor that reduces Furthermore, since the Mannesmann-type pipe manufacturing method is a method suitable for mass production, it is not suitable for small-scale production of special steel types such as, for example, spring steel. In the case of the stabilizer bar, this causes a cost increase. become. As described above, at present, the stabilizer bar is hollowed out to reduce the weight of the car, but it does not meet the needs of further improving fatigue strength, the need for stabilizing quality, and In fact, there has not been proposed any technology for manufacturing a stabilizer bar having both of them.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a hollow stabilizer bar for automobiles, which solves the above-mentioned problems and has both excellent fatigue strength and quality stability, and is lighter than conventional ones. Another object of the present invention is to provide a hollow stabilizer bar that withstands a large load and has excellent fatigue strength. The gist of the invention is that in a method of manufacturing a hollow stabilizer bar, a hollow billet is manufactured by machining from a billet made of an alloy steel having a high material strength excellent in hardenability such as spring steel. After induction heating of the hollow billet, a glass lubricating treatment is performed with a glass lubricant having a viscosity of the following formula, and a hollow stabilizer bar characterized by using an extruded steel pipe while preventing surface decarburization of the hollow billet. It is in the manufacturing method. 150 ≦ η ≦ 91.4ρ + 330.1 where ρ: deformation resistance of the material during hot extrusion (kgf
/ Mm ² ).

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a process diagram for manufacturing a hollow steel pipe for a hollow stabilizer bar according to the present invention. As shown in FIG. 1, the extruding material is an alloy steel having high material strength such as spring steel having excellent hardenability, that is, spring steel, bearing steel, manganese steel having C of 0.30% or more, manganese chrome steel, chromium. Steel, chromium molybdenum steel, nickel steel, nickel chrome steel, nickel chromium molybdenum steel, non-heat treated steel and the like. For example, C: 0.43%, Mn: 0.10
% Steel (JIS SMn443), C: 0.60%,
Si: 0.25%, Mn: 0.90%, Cr steel (JIS
SUP9A) or the like. Further, when corrosion resistance is particularly required, stainless steel, heat-resistant steel, etc. in which the amounts of Cr, Ni, Mo and the like are further increased can be used.

In order to form the billet 1 made of an alloy steel or the like into a tube by extrusion, a central portion of the billet 1 is punched in a predetermined dimension, cut, and a round bar-shaped hollow billet 2 finished in a predetermined shape is formed. use. The drilling of the billet is finished smoothly by machining such as drilling.
In some cases, the outer diameter of the billet can be smoothly finished by machining such as peeling and turning. The heating is performed by the induction heating device 3 in a short time, and thereafter, the glass is lubricated immediately and extruded.

In the glass lubrication treatment, the powdered glass is applied and sprayed on the inside and outside of the hollow billet 2 after heating to adhere the glass lubricating film 4, and the powdered glass is hardened in an extruder. A series of processes for lubrication, such as setting a pad 5 having a predetermined shape, are performed. With the glass lubricating film 4 formed on the hollow billet 2 in this manner, the hollow billet 2 is inserted into the container 6 and the stem 8 with the mandrel 7 is inserted.
To produce an extruded tube 9. The outer diameter of the extrusion tube is determined by the inner diameter of the die 10, and the inner diameter is determined by the outer diameter of the mandrel 7. Reference numeral 11 denotes a die carriage, and reference numeral 12 denotes a cutting saw.

[0010] As described above, it is important to prevent decarburization. However, in the above-described process, the hollow billet 2 is finished smoothly, and extruded from heating to heating in a short time. After extruding with the glass lubricant used at the time of extrusion, since the outer diameter surface of the steel pipe is uniformly covered with the glass lubricating film 4, the depth of decarburization can be extremely reduced. Further, by protecting the glass lubricating film, it is possible to prevent the occurrence of linear scratches on the inner and outer surfaces of the steel pipe during pipe production.

At this time, it is important to use a glass lubricant having an appropriate viscosity according to the deformation resistance of the material during hot extrusion. FIG. 2 shows the relationship between the hot deformation resistance of the material and the viscosity of the glass lubricant used in relation to the decarburization and surface properties of the extruded product. According to FIG. 2, if the viscosity of the glass lubricant used is too low than the proper viscosity, lubrication failure occurs, and burning and decarburization of the portion where the lubrication failure occurs progresses, and linear scratches also occur. Become. On the other hand, if the viscosity is too high, the lubrication may run out, or a portion of the lubricating material may be partially thick, resulting in a poor product shape.

That is, FIG. 3 is an explanatory diagram showing the relationship between the decarburization depth and the rotational bending fatigue limit. As shown in FIG.
As the decarburization depth increases, the fatigue strength decreases, but in particular, sharply decreases in the region where the decarburization depth is 0.2 mm or more. Therefore, in order to ensure high fatigue strength, it is necessary to reduce the decarburization depth.
It can be seen that high fatigue strength can be ensured by ensuring the thickness is not more than mm. By the above-mentioned glass lubrication of proper viscosity, a smooth seamless steel pipe having a surface property with very little decarburization can be obtained.

As described above, the depth of the decarburized layer is reduced as much as possible by using a glass-lubricating material having an appropriate viscosity and applying a pipe-forming method subjected to a glass lubrication treatment. A hollow stabilizer bar with a uniform hot-finished seam-free steel tube and excellent fatigue strength and quality stability can be manufactured.A hollow stabilizer bar with a lighter weight and superior fatigue strength to withstand large loads than before can be manufactured. Can be manufactured.

[0014]

EXAMPLE A hollow stabilizer bar (outer diameter 42.7 mm, wall thickness 7.0) manufactured from a seamless steel pipe made of spring steel (JIS SUP9A) by the method according to the present invention as a material.
mm) at the maximum principal stress amplitude on the vertical axis shown in FIG. 4, and as a result of repeating the durability test, as shown in FIG. 4, the solid line is a manganese steel (Japanese Patent Application Laid-Open No. 56-90137). It shows the fatigue strength level of a hollow stabilizer bar (outer diameter 17.3 mm, wall thickness 2.3 mm) of a seamless steel pipe made of JIS SMn443). In contrast, the stabilizer bar of the present invention illustrated in FIG. 4 has a fatigue strength of twice or more at the same main stress level despite having a larger outer diameter and a larger wall thickness as compared with the conventional product, as shown by the mark ○. It can be seen that it has. Table 1 shows the relationship between the viscosity of the lubricating glass, the decarburization depth of the product, the fatigue strength of the stabilizer product, and a comparison with the conventional product. From Table 1, it can be seen that in the examples of the present invention, the decarburization of the product is small by using a glass lubricant having an appropriate viscosity, and the fatigue strength of the stabilizer product is at least twice as high as that of the conventional example and the comparative example.

[0015]

[Table 1]

[0016]

As described above, the hollow stabilizer bar of the present invention has twice or more the fatigue strength as compared with the conventional method. Even when the present invention is applied to a stabilizer bar of a bus, the required fatigue strength can be provided, and the weight of the vehicle can be further reduced. Furthermore, according to the present invention, a steel pipe having a smooth surface, stable quality with little decarburization can be obtained, and it can sufficiently cope with small-quantity production, so that an inexpensive product can be manufactured. It is effective.

[Brief description of the drawings]

FIG. 1 is a process diagram for manufacturing a hollow steel tube for a hollow stabilizer bar according to the present invention;

FIG. 2 is a diagram showing a relationship between hot deformation resistance of a material and viscosity of a glass lubricant;

FIG. 3 is an explanatory diagram showing the relationship between the decarburization depth and the rotational bending fatigue limit,

FIG. 4 is a view showing a comparison between the fatigue strength of a stabilizer bar using an extruded steel pipe of the present invention and a stabilizer bar using a conventional seamless steel pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Billet 2 Hollow billet 3 Induction heating device 4 Glass lubrication film 5 Glass pad 6 Container 7 Mandrel 8 Stem 9 Extruded tube 10 Dies 11 Die carriage 12 Cutting saw

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Tomita 1827-4 Kamitakano 4 Yachiyo-shi, Chiba Pref.

Claims (1)

[Claims] In a method of manufacturing a hollow stabilizer bar, a hollow billet is manufactured by machining from a billet made of an alloy steel having high material strength and excellent in hardenability such as spring steel, and the hollow billet is guided. After the heating, a glass lubrication treatment is performed with a glass lubricant having a viscosity η (Poise) of the following formula, and a steel tube extruded while preventing surface decarburization of the hollow billet is used. Manufacturing method. 150 ≦ η ≦ 91.4ρ + 330.1 where ρ: deformation resistance of the material during hot extrusion (kgf
/ Mm ² ).