JP2000118224A - Hollow-shaped stabilizer and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow-shaped stabilizer and a method of its manufacture capable of use under a condition of higher preset stress by reinforcing an inner surface of the hollow-shaped stabilizer. SOLUTION: This hollow-shaped stabilizer formed by a steel pipe having a cemented steel layer in an inner surface is obtained by applying an applying type carburizing composition formed by compounding a carburizing compound in water paint and an inactive carburizing promoting agent relating to the water paint to the inner surface of the steel pipe, forming a film by drying, mold working the steel pipe formed with the film, forming the cemented steel layer by heating for a sufficient time at a sufficient temperature for forming the cemented steel layer, and then performing hardening treatment by quenching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow stabilizer using a steel pipe and a method for manufacturing the same. More specifically, the present invention relates to a hollow stabilizer having a carburized hardened layer on the inner surface of a steel pipe and a method for manufacturing the same.

[0002]

2. Description of the Related Art Stabilizers, which are parts that reduce rolling of a vehicle body and maintain running stability in cornering of an automobile, are mainly manufactured from S45C class steel bars. Stabilizers are automotive parts that are required to withstand torsional stress in terms of their application and function.If the outer diameter is increased to increase the torsional stress, the weight will increase significantly. There was a problem of doing. In recent years, interest in global environmental issues has increased, and automobiles have been reduced in weight, particularly from the perspective of energy saving.Stabilizers instead of steel bars, steel pipes with a large degree of freedom in the set stress separately from the weight are also used. A so-called hollow stabilizer made of a material has been developed and its weight has been reduced.

[0003] As such a hollow stabilizer,
After forming a 590 N / mm ² class or 780 N / mm ² class high tensile steel tube into a predetermined shape, a non-heat treated stabilizer or low alloy steel tube with shot peening on the outer surface is formed into a predetermined shape. After forming, direct heating or high-frequency induction heating is performed for a short time, then quenching is performed to quench the entire steel pipe to form a quenched martensite structure, then tempering is performed, and shot peening is applied to the outer surface. There are tempered stabilizers that have been applied, and tempered stabilizers are the mainstream.

[0004] However, these conventional hollow stabilizers have the following problems. In other words, (1) the degree of flatness is large and the strength is reduced as compared with the steel bar for bending, and (2) the outer surface can be strengthened by shot peening or the like. There is no method for strengthening, and when the set stress becomes high, fatigue fracture occurs starting from the inner surface. Therefore, a stabilizer using a steel pipe can be used only in a very limited application range.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to enhance the inner surface, which is a disadvantage of the above-mentioned conventional hollow stabilizer, and to provide a hollow stabilizer which can be used under higher set stress conditions. An object of the present invention is to provide a stabilizer and a manufacturing method thereof.

[0006]

Means for Solving the Problems The present inventors can selectively carburize and quench the inner surface of a steel pipe by using a specific coating type carburizing composition, and use a conventional hollow stabilizer. The present inventors have found that the inner surface can be strengthened without impairing the productivity in the manufacturing process of the present invention, and completed the present invention.

That is, the present invention relates to a hollow stabilizer having a carburized hardened layer on the inner surface. Further, the present invention provides a coating type carburizing composition comprising a water-based paint and a carburizing agent and a carburizing accelerator inert to the water-based paint, applied to the inner surface of the steel pipe, and dried to form a film. The formed and coated steel pipe is formed and processed, and heated at a temperature and for a sufficient time to form a carburized layer to form a carburized layer, then quenched and quenched to form a carburized layer on the inner surface of the steel pipe. And a method for producing a hollow stabilizer including the step of obtaining In the above method, it is preferable from the viewpoint of productivity that the carburized layer is formed by direct electric heating or high-frequency induction heating.

In the above method, the water-based paint obtained by dispersing an olefin polymer resin as an application type carburizing composition in an aqueous medium may contain 10 to 100 parts by weight of charcoal powder per 100 parts by weight of the resin as a carburizing agent. It is preferable to apply a composition comprising 5 to 80 parts by weight of sodium carbonate per 100 parts by weight of the resin as a carburizing accelerator so that the dry film amount is 10 to 100 g / m ² . When using the above-mentioned coating type carburizing composition, it is preferable to heat and dry at 100 to 150 ° C to form a film, and to heat and quench at 900 to 1200 ° C to form a carburized layer. The method of manufacturing the hollow stabilizer may include a step of tempering the steel pipe and a step of shot peening the outer surface of the steel pipe after the step of quenching and quenching to obtain a carburized hardened layer on the inner surface of the steel pipe.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The steel pipe used in the present invention is used as a material of the hollow stabilizer, and is not particularly limited as long as a martensite structure can be obtained in the treatment of the present invention. In addition, the outer diameter of the steel pipe is not particularly limited as long as the object of the present invention can be achieved, and is appropriately selected according to the type of the applicable vehicle. The steel pipe has a thickness of 1 μm by a method described later.
It is preferable to provide a carburized hardened layer having a Vickers hardness of 600 or more.

In the present invention, the coating type carburizing composition is first applied to the inner surface of the steel pipe. At this time, it is preferable to wash the inner surface in advance in order to obtain a uniform carburized hardened layer. The washing method is not particularly limited as long as an appropriate film is formed after the coating type carburizing composition is applied and dried, and then a uniform carburized layer can be formed when carburizing is performed. Degreasing with an organic solvent and the like can be mentioned. In addition, this washing step may be performed in a step in which the steel strip is continuously formed with a forming roll, or may be performed after forming the steel pipe. The coating type carburizing composition is applied to the inner surface of the pre-cleaned steel pipe. The coating-type carburizing composition used in the present invention is a coating-type carburizing composition in which a carburizing agent and a carburizing accelerator which is inert to the above-mentioned water-based coating are mixed in the water-based coating.

Here, as the water-based paint in the coating type carburizing composition, a film can be easily formed in a short time by heating at a relatively low temperature, and the formed film is in close contact with the inner surface of the steel material. It is preferable to use an aqueous paint in which an olefin-based polymer resin is dispersed in an aqueous medium, from the viewpoints of being excellent in properties and processability, and not releasing a harmful substance even when heated when forming a carburized layer. . Examples of such olefin-based polymer resins include resins composed of olefin-based polymers such as polyethylene and polypropylene, resins composed of olefin-based copolymers such as ethylene-propylene copolymer, and blended polymers thereof. They can be used alone or as a mixture of two or more. In addition, these resins should be used in the form of powder having an average particle size of about 0.1 to 3.0 μm in consideration of the properties as a water-based paint, the formation of a film on an object to be treated, and the workability. preferable. In addition, these resins are used in an amount of 10 wt.
It is preferred to mix in an amount of about 40 parts by weight. Further, a small amount of an organic solvent, an antifoaming agent or the like for improving wettability may be added.

Examples of the carburizing agent to be blended in the coating type carburizing composition include graphite powder, carbon black powder, charcoal powder and the like, and these can be used alone or as a mixture of two or more kinds. The present inventors have conducted a thermal analysis on these carburizing agents in the atmosphere. As a result, graphite powder rapidly oxidized and burned at around 750 ° C.
Even after the temperature was raised to 000 ° C. or higher, it remained without burning. In contrast, carbon black rapidly oxidized and burned at 650 ° C, and charcoal powder rapidly oxidized and burned at around 500 ° C. Further, with carbon black and charcoal powder, no residual weight was observed after the temperature was raised to 1000 ° C. or higher. From these experimental results, as a carburizing agent for forming a uniform carburized layer in a short heat treatment, carbon black and charcoal powder capable of rapidly oxidizing and burning at a low temperature to increase carburizing gas pressure are preferable, and more preferably charcoal is used. Powder.

[0013] A carburized layer may be added to the coating type carburizing composition.
CO2 when heated to form_TwoImmersion with increased pressure
For the purpose of promoting charcoal, a carburizing accelerator is added. Steel pipe
Oxidation combustion of carburizing agent on the inner surface under oxygen-lean conditions
As it does, carburizing accelerators play an important role. this
As such a carburizing accelerator, the base water-based paint
Addition, storage of coating type carburizing composition and formation of film
During heating for CO2 _TwoSuch as carburizing temperature
If it generates gas for the first time when heated
It is not limited to. These carburizing accelerators are used
Determined depending on the type of aqueous medium used and the method of film formation
However, sodium carbonate and its equivalents are preferred. Soak
For example, charcoal accelerators are based on olefin-based heavyweight paints.
Based on an aqueous paint made by dispersing a coalescing resin in an aqueous medium
When used as barium carbonate (BaCO_Three)
If used, CO_TwoAnd also over-manga
Potassium acid (K_TwoMnO_Four) When dispersed
O_TwoIs not preferred.

In the coating type carburizing composition used in the present invention, a carburizing agent and a carburizing accelerator inert to the above-mentioned water-based paint are blended in the water-based paint. Is appropriately selected in consideration of the physical properties of the paint, the viscosity of the paint, the generation time of the carburizing gas and the like.

For example, a coating type carburizing composition using an aqueous paint prepared by dispersing an olefin polymer in an aqueous medium, using charcoal powder as a carburizing agent, and sodium carbonate as a carburizing accelerator is used for the inner surface of a steel pipe. The hardness of the carburized hardened layer to be formed was set to be 600 or more in Vickers hardness, and the thickness of the carburized layer was set to be 1 μm or more, and the appropriate composition was examined.
It is preferably in the range of 10 to 100 parts by weight, particularly preferably 30 to 80 parts by weight, based on 100 parts by weight of the resin, and the addition amount of sodium carbonate as a carburizing accelerator is 100 parts by weight of the resin. The amount is preferably 5 to 80 parts by weight, particularly preferably 15 to 50 parts by weight. If the compounding amount of the charcoal powder exceeds 100 parts by weight, the adhesion and workability of the film formed due to the lack of the resin component with the object to be treated are reduced,
In addition, the viscosity of the paint when applying becomes significantly higher,
It is not preferable because it becomes difficult to apply by brush coating, roll coating or the like. Conversely, if the compounding amount is less than 10 parts by weight, it takes a long time to generate carburizing gas, and a long time is required for the carburizing heat treatment, which is not preferable. If the compounding amount of the carburizing accelerator is less than 5 parts by weight based on 100 parts by weight of the resin, the effect as the carburizing accelerator is undesirably reduced. Conversely, if the amount exceeds 80 parts by weight, the liquid properties of the composition are undesirably reduced.

The coating type carburizing composition is applied to the inner surface of a steel pipe, and the coating method at this time is appropriately selected from coating methods used in the field of conventional water-based coatings. Examples of such a coating method include brush coating, roll coating, spray coating, dipping, and the like. The coating amount of the coating type carburizing composition at this time is appropriately selected in consideration of the material of the steel pipe to be carburized, the inner diameter of the steel pipe, the thickness of the carburized layer, etc., for example, the outer diameter is 40 mm or less, and the plate thickness is 5 mm or less. When using steel pipe of
It is preferable to apply so that the dry film amount is 10 to 100 g / m ² . If the dry film amount is less than 10 g / m ² , the carburizing source is insufficient, and it is difficult to secure a carburized hardened layer of 1 μm or more, which is not preferable. Exceeds 100 g / m ² in dry film weight Conversely, worsened adhesiveness and workability of the film, it is not preferable because it becomes difficult to process into a desired shape, is applied beyond 100 g / m ² However, an effect commensurate with increased application cannot be obtained.

The coating type carburizing composition according to the present invention coated as described above is dried to form a film. A dispersion obtained by dispersing a thermoplastic resin such as an olefin polymer resin in an aqueous medium is used as an aqueous coating material. When used as a base, it is heated to a temperature higher than the boiling point of water and higher than the melting point of the resin used. For example, when an olefin polymer resin is used, 10
A film is formed by heating to 0 to 150 ° C.
When a film is formed in this way, the adhesion strength is improved,
No peeling-off of the film occurs even after bending of the steel pipe.

The steel pipe with the coating formed on the inner surface in this way is processed into a stabilizer shape by a usual method, for example, a bender, and then subjected to a carburizing and quenching treatment.
The heating means at this time is not particularly limited as long as a desired carburized hardened layer can be obtained, but is a general surface hardening means in the technical field, and the martensitic structure is easily formed by heating and quenching for a short time. Direct current heating or high-frequency induction heating is preferred from the viewpoint of obtaining.

The baking temperature depends on the coating type carburizing composition to be used, in particular, the type of carburizing agent contained in the composition, and is obtained, for example, by dispersing an olefin polymer resin in an aqueous medium. When a composition comprising 10 to 100 parts by weight of charcoal powder per 100 parts by weight of the resin as a carburizing agent and 5 to 80 parts by weight of sodium carbonate per 100 parts by weight of the resin as a carburizing accelerator is used in an aqueous paint. Is preferably in a temperature range of 900 to 1200 ° C. If the heating temperature is lower than 900 ° C., a desired carburized hardened layer cannot be formed. If the heating temperature exceeds 1200 ° C., the crystal grain size becomes coarse and not only the toughness of the steel pipe decreases, but also the carburizing concentration decreases. It is not preferable because control becomes difficult, and it often becomes over-carburized to form a residual austenite phase in the quenched structure, which hinders effective generation of compressive residual stress.

If the heating time is not controlled when heating in the above temperature range, carburization becomes insufficient or conversely, carburization occurs. Therefore, the water-based paint obtained by dispersing the olefin-based polymer resin in an aqueous medium is used as a carburizing agent as a carburizing agent in an amount of 10 to 10 charcoal powder per 100 parts by weight of the resin.
Using a composition obtained by mixing 5 parts to 80 parts by weight of sodium carbonate per 100 parts by weight of the resin as a carburizing accelerator as a coating-type carburizing composition, the heating temperature and the heating time within the above temperature range As a result of the experiment, FIG.
It has been found that a desired carburized hardened layer can be obtained by performing carburizing and quenching under the conditions surrounded by the four points A, B, C, and D shown in FIG.

The hollow stabilizer according to the present invention in which the carburized hardened layer is formed on the inner surface of the steel pipe as described above,
The outer surface may be treated in a conventional manner. In particular, in the present invention, the coating type carburizing composition is applied to the inner surface of the steel pipe,
After drying to form a film, it is molded into a hollow of a predetermined shape by a bender, etc., heat-hardened to form a carburized hardened layer on the inner surface, tempered, and reinforced by shot peening on the outer surface. By performing body painting, it is possible to produce a product through a series of steps.

[0022]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples. (Examples 1 to 7 and Comparative Examples 1 to 5) In these Examples and Comparative Examples, a carburizing agent was added to an aqueous paint obtained by dispersing an olefin polymer resin in an aqueous medium as a coating type carburizing composition. The composition of carburized powder and sodium carbonate as a carburizing accelerator was mixed in various amounts, and the coating amount, heating time, and heating temperature were varied to investigate the formation of the carburized hardened layer on the inner surface of the steel pipe. . C 0.23
%, Si 0.23%, Mn 0.44%, Cr 0.
30%, P 0.008%, S 0.008%, B
Using a steel pipe having an outer diameter of 26.5 mm and a wall thickness of 4.0 mm made of 0.004% with the balance being Fe, the inner surface was previously cleaned by alkali degreasing, and then carburized and quenched under the conditions shown in Table 1. The steel pipe has a completely martensitic structure after the treatment, and has a hardness of about 480 in Vickers hardness. Table 1 shows the results. In Table 1, the coating amount of the carburizing composition was calculated from the difference between the weight of the steel pipe before and after coating and drying, and the area of the inner surface of the steel pipe obtained by calculation. Further, in Examples 1 and 5, a polypropylene resin was used as a resin component, and a polyethylene resin was used for the other components. The quenching heating was performed by a direct current heating method.

[0023]

[Table 1]

As is clear from Table 1, all of the examples in which the carburizing and quenching treatment according to the present invention was carried out formed the target carburized hardened layer. On the other hand, Comparative Example 1 in which sodium carbonate as a carburizing accelerator was not added, Comparative Example 2 in which the film was insufficiently formed, and Comparative Example in which the compounding ratio of the charcoal powder as the carburizing agent was out of the range of the present invention. In Comparative Example 3, a carburized layer was locally obtained, but a stable and uniform carburized layer was not obtained. Further, in Comparative Example 4 in which the carburizing temperature was lower than the range of the present invention, a sufficient carburized layer could not be secured, and the carburizing time was short. In Comparative Example 5 which was longer than the range of the present invention, the crystal grain size of the carburized layer was coarsened, and the hardness of the carburized hardened layer was reduced and the hardness was uneven due to the formation of the retained austenite.

From the above results, it can be seen that a desired carburized layer can be formed on the inner surface of a steel pipe by applying the coating-type carburizing composition according to the present invention under predetermined conditions, performing carburizing and quenching treatment under specific heating conditions after drying. I understood.

[0026]

According to the present invention, the inner surface of the hollow stabilizer can be selectively carburized and quenched to strengthen the inner surface. Further, according to the method of the present invention, it has become possible to strengthen the inner surface without impairing the productivity in the conventional stabilizer manufacturing process.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of quenching conditions of the present invention.

Continuation of the front page (72) Inventor Masahiro Murakami 1 at 7-Takaya-Shinmachi, Ichikawa-shi, Chiba In-house Nippon Steel Research Institute (72) Inventor Kenji Okishi 1-Nisshin at 7-Takaya-Shimmachi, Ichikawa-shi, Chiba Inside Steel Technology Co., Ltd. (72) Inventor Kenichi Shinoda 34 Hamacho, Gamagori-shi, Aichi Prefecture Nissin Kokan Co., Ltd.In-house (72) Inventor Toshifumi Kamachi 34 Hamacho, Gamagori-shi, Aichi Prefecture Nissin Kokan Co., Ltd.F-term ( Reference) 3D001 AA00 AA17 DA06

Claims (6)

[Claims] 1. A hollow stabilizer made of a steel pipe having a carburized hardened layer on an inner surface. 2. A coating type carburizing composition comprising a water-based coating composition containing a carburizing agent and a carburizing accelerator inert to the water-based coating composition is applied to the inner surface of a steel pipe and dried to form a film. Then, the steel pipe with the film formed is formed and processed, and the carburized layer is formed by heating at a temperature and for a sufficient time to form a carburized layer, then quenching and quenching to form a carburized layer on the inner surface of the steel pipe. A method for producing a hollow stabilizer, comprising the step of: 3. The method for producing a hollow stabilizer according to claim 2, wherein the carburized layer is formed by direct current heating or high-frequency induction heating. 4. A coating type carburizing composition to be used is obtained by dispersing an olefin-based polymer resin in an aqueous medium and adding 10 to 100 parts by weight of charcoal powder per 100 parts by weight of the resin as a carburizing agent. And a composition comprising 5 to 80 parts by weight of sodium carbonate per 100 parts by weight of the resin as a carburizing accelerator, and applying the composition so as to have a dry film amount of 10 to 100 g / m ^2. The method for producing a hollow stabilizer according to claim 2 or 3. 5. 100-150 ° C. for forming a film
To dryness and 90 to form a carburized layer.
The method for producing a hollow stabilizer according to claim 4, wherein the method is heat-quenched to 0 to 1200 ° C. 6. The steel pipe according to claim 2, further comprising a step of tempering the steel pipe and a step of shot peening the outer surface of the steel pipe after the step of quenching and quenching to obtain a carburized hardened layer on the inner surface of the steel pipe. The method for producing a hollow stabilizer according to any one of the above.