JPH01163060A - High bending absorption energy steel pipe - Google Patents

Abstract

PURPOSE:To easily and inexpensively obtain high bending absorption energy by using a material enhanced in buckling strength, high in use frequency and having tensile strength of 60kgf/mm<2>, by filling a steel pipe having ribs provided to the inner surface thereof with a synthetic resin. CONSTITUTION:Ribs 3 enhancing buckling strength are provided to a steel pipe 2. When a steel pipe having no ribs is prepared using a usual hot coil having tensile strength of 60kgf/mm<2>, energy absorption quantity of about 130kgf/m is shown but, by providing the ribs, the energy absorption quantity is drastically increased to reach about 200kgf/m. Next, steel pipe 2 is filled with a lightweight low cost polyurethane resin 4 to enhance energy absorption quantity. Since the polyurethane resin 4 shows high energy absorption rate in the order of high temp. curable type medium temp. curable type low temp. curable type, said resin is properly used according to a use purpose and sufficient effect is obtained by filling under atmospheric pressure and no pressurization is required.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high bending absorption energy steel pipe mainly used as a material for reinforcing materials and cushioning materials.

[Conventional technology]

In the vehicle-related field, since the oil crisis, there has been an increasing trend to reduce the weight of parts and reduce fuel consumption. This weight reduction may weaken some parts of the structure, but
In areas where strength is required, reinforcing materials and the like are installed to compensate for the decrease in strength. Particularly in passenger cars, where weight reduction is progressing, the side structures are weaker than other parts, and if a collision occurs, there is a risk of serious damage.

Therefore, reinforcing materials are installed in the space inside the door to absorb the energy in the event of a collision and protect the driver and passengers from the impact. The higher the energy absorption, the higher the safety, so honeycomb structures made of bent high-tensile steel plates and spot welding are often used, but recently, structures made of assembled steel pipes have also been used. It has become to. In steel pipes, -a
The larger the pipe diameter and the thicker the wall, the greater the amount of energy absorbed.

However, in passenger cars, the pipe diameter is limited due to limited door space, and there is also a strong desire to reduce the weight, so it is not possible to increase the wall thickness. This shape restriction also reduces the amount of energy absorbed, but this reduction is compensated for by increasing the tensile strength. Generally, it is 10.0 to 120 kgf to meet the specified safety standards.
It is said that a tensile strength of 7 mm2 is required. Usually, after quenching a steel pipe containing 0.30% C, it is annealed at a low temperature to obtain the above tensile strength.

[Problem that the invention seeks to solve]

On the other hand, there is also a strong demand for cheaper parts. Although this is aimed at strengthening international competitiveness, conventional steel pipes for reinforcing materials tend to be expensive in terms of cost as they require heat treatment.

Therefore, there is a need for a method for manufacturing high-strength steel pipes that does not require heat treatment, and research is being carried out day and night. - For example, attempts have been made to manufacture electric resistance welded steel pipes using high-strength steel plates as raw materials, but as of now, they have not been put into practical use because the yield is only 80 kgf/mm''.

SUMMARY OF THE INVENTION An object of the present invention is therefore to provide a steel pipe with high bending absorption energy and reduced cost.

[Means for solving problems]

In order to achieve the above object, the present invention is characterized in that the inside of a steel pipe having ribs on the inner surface of the pipe is filled with a synthetic resin.

Synthetic resins are classified into thermoplastic, thermosetting, hard, and soft depending on how they are classified, but in the present invention, synthetic resin is filled to prevent buckling of the steel pipe while increasing the amount of deformation and absorbing energy. Since it needs to be large, it is better to use a slightly soft synthetic resin that can follow the deformation of the steel pipe rather than something hard and brittle. This type of synthetic resin includes polyurethane, soft vinyl chloride resin, silicone resin, nylon, and the like. Although there is a distinction between foamed and non-foamed materials, foamed materials may be used if further weight reduction is desired.

[For production]

ERW steel pipes are manufactured continuously from steel strips by electric resistance welding, and are therefore inexpensive to manufacture. The resistance welded steel pipe has only been obtained with a strength of about 80 kgf/mm2, but in the present invention, even if it is less than that, about 60 kgf/mm2, the buckling strength can be increased by the ribs and synthetic resin, so the tensile strength can be increased. strength 10
Effects comparable to those of 0-120kgf 7mm" can be obtained at low cost.

〔Example〕

Examples will be described below with reference to the drawings.

A high bending energy absorption steel pipe 1 shown in FIG. 1 is produced as a reinforcing steel pipe to be placed inside the door of a passenger car. This type of reinforcing steel pipe 2 has an outer diameter of 31.8 mmφ and a wall thickness of 2.4 mm due to demands for door space and weight reduction.
A diameter of about mm is often used. The manufacturing method of the steel pipe 2 is not particularly limited, but there is a strong demand for low cost, and the present invention does not require a material with particularly high tensile strength, so it is preferable to manufacture the steel pipe 2 by electric resistance welding, which is highly productive. is desirable. In this method, the electric resistance welded tube is manufactured continuously, so the cost is also low.

Normally, reinforcing steel pipes placed inside the doors of passenger cars contain 20
It is said that an energy absorption of 0 to 246 kgf/rnm is required.If this is to be achieved with an ERW steel pipe, a tensile strength of 100 to 120 kgf/mn+2 is required.ERW welded pipe As mentioned above, the tensile strength is 8
0 kgf/mm", and therefore a normal circular cross section cannot obtain high bending absorption energy. In addition, conventionally, after quenching, low-temperature annealing is performed to achieve a bending strength of 100 to 120 kgf/mm". I tried to keep it within the range of , but since heat treatment would also be added,
It was also expensive.

The present invention aims to reduce costs by eliminating the need for the heat treatment described above, and as can be seen in the figure, ribs 3 are provided in the steel pipe 2 to increase buckling strength. In the figure, the ribs 3 are oriented in a direction that bisects the 20-yen circular surface of the steel pipe, but this is done to increase the energy absorption rate in only one direction, taking into account the direction of deformation in a side impact. Therefore, 2
When it is necessary to increase the energy absorption rate in more than one direction, it is desirable to change the lip shape according to that direction. For example, an inscribed polygonal rib can be provided within the steel pipe to accommodate this.

By the way, when steel pipes without ribs and with ribs are manufactured using a hot coil with a tensile strength of 60 kg f 7 mm2, which is often used and is inexpensive,
In the former case, the energy absorption amount is only about 130 kgf/m, but in the latter case, it increases dramatically, and 2
It reaches about 00kgf/m.

This value is close to the standard value, but if human life is to be respected, it is desirable that the energy absorption amount be even higher. The quickest way is to make the wall thicker, but if it is too thick, it goes against the desire for weight reduction, and in some cases may even prevent the use of electric resistance welding, which has high production efficiency. .

Therefore, in the present invention, the steel pipe 2 is filled with a synthetic resin, such as a polyurethane resin 4 that is lightweight and inexpensive, to further increase the amount of energy absorption. There are three types of polyurethane resin 4: high temperature curing type, medium temperature curing type, and room temperature curing type, and any of them may be used in the present invention. However, since the energy absorption rate is higher in the order of high temperature curing type, medium temperature curing type and low temperature curing type, it is desirable to use them properly depending on the purpose. There is no need to pressurize the filling, as sufficient effects can be obtained even at atmospheric pressure.

Next, a method of manufacturing the steel pipe 2 with ribs 3 will be explained with reference to FIGS. 2 to 6. Ribbed steel pipes can be manufactured continuously at low cost using hot coil HC as a raw material by simply adding a rib forming process to the forming process of a normal electric resistance welded steel pipe manufacturing line. First, the hot coil HC shown in FIG. 2 is bent using an upper roll and a lower roll for forming ribs from the end of the hot coil HC at a position corresponding to the inner diameter of the pipe to form the rib 3 (see FIG. 3). Subsequently, in the process of forming the steel pipe 2, the body is formed into a circular shape. Although FIG. 4 shows the process of molding by the edge bending method, the process is not limited to this, and for example, the center bending method or the circular bending method may be used.

The rib side ends of the body are butted together in the above molding process (see FIG. 5), and a high frequency current i is applied to the butt 1111 through the contact tip 5°5 as shown in FIG. Butt welding is performed in the same way as general electric resistance welded steel pipes. A part of the welding current i also flows to the rib 3 side,
It is utilized for welding rib ends and steel pipes. Although this welding is only temporary welding, it is considered to be sufficient for usability. Further, although the illustrated example uses a resistance method, an induction method may also be used. External bead B is removed in the same way as for general electric resistance welded steel pipes.

Next, the electric resistance welded steel pipe 2 is cut into a length of 800 mm, and the hollow part thereof is filled with polyurethane resin or foamed polyurethane resin 4. Polyurethane resin 4 is a high temperature curing type with the trade name Tachinate L-2705, a medium temperature curing type with the trade name Hypren Q-588, and a room temperature curing type with the trade name Tachinate XL-M30A. , polyurethane foams are sold under the trade names of Toyo Tire & Rubber Industries (Yokono Soflan-R), so they can be used.The curing agents include MOCA and Hyblen MC-, respectively.
623 and Tatinate XL-1130B are used because they are sold under the trade names.

Among the above polyurethane resins, the high temperature curing type has a temperature of 120°C.
The medium-temperature curing type requires heating at 60°C, and the filling method is carried out according to the processing steps shown in FIG. In the figure, the steps indicated by the two-dot chain line frame are necessary steps to be taken when filling the high-temperature heating type resin. The polyurethane resin is injected under atmospheric pressure, and there is no need to apply any particular pressure.

In order to confirm the performance of the high bending energy absorption steel pipe for door reinforcement according to the present invention manufactured as described above, the amount of energy absorbed was measured using the test device 6 shown in FIG. 8, and the results are shown in Table 1. Obtained. Also, for comparison,
Measurements were also carried out on pipes without polyurethane resin, without ribs, and in general steel pipes. The test materials were 20 each, and the test material M was bent by H=150 mm using a pushing tool 7 with a radius of 305 mm.
The energy required at that time was measured. Since the high bending energy absorption steel pipe according to the present invention has directionality, the welded portion was placed outside or inside the bend. Measurement span L is 6
00mm.

As a result, when filling with high-temperature type polyurethane resin, an average of 255 kgf-m was used, and 246 kgf-m was used when filling with medium-temperature type polyurethane resin.
The room temperature type required 226 kgf-m of energy, and the polyurethane foam required 221 kgf-m of energy. On the other hand, the average strength of ribbed steel pipes is 196 kgf-m, and the average strength of regular steel pipes without ribs is 129 kgf-m.
It has been found that filling with polyurethane resin is lightweight and inexpensive, and has a sufficient effect against breakage. Note that the average strength of conventional steel pipes subjected to heat treatment is 194 kgf-m.

Note that the high bending energy absorption steel pipe according to the present invention can be used for purposes other than door reinforcing materials for passenger cars.

〔Effect of the invention〕

As explained above, according to the present invention, a steel pipe with a tensile strength of 60 kgf/mm, which is frequently used as a steel pipe for reinforcing doors.
The required high bending absorption energy can be obtained with light weight and low cost. Conventionally, this high bending absorption energy was obtained by heat treatment, but this is not necessary in the present invention.

In manufacturing, only slight modifications to the conventional electric resistance welded steel pipe manufacturing line are required, making mass production possible and reducing costs. In addition, simply filling with synthetic resin such as polyurethane resin can further improve the bending absorption energy, contributing to weight reduction.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the present invention, Figs. 2 to 6 show the manufacturing process of the steel pipe, Fig. 2 is a perspective view of a real coil, and Fig. 3 is a rib formation. FIG. 4 is an explanatory view showing the forming process, FIG. 5 is an explanatory view showing the butt state, FIG. 6 is a perspective view showing the welding state,
FIG. 7 is a block diagram showing the polyurethane resin filling process, and FIG. 8 is a front view of a test device used for measuring bending energy. ■...High bending absorption energy steel pipe, 2...Steel pipe, 3
...Rib, 4...Synthetic resin. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) A steel pipe with high bending absorption energy, which is made by filling a synthetic resin inside a steel pipe having ribs on the inner surface of the pipe.