JP2007191774A - Energy absorbing rope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an energy absorbing rope maintaining strength and further having extremely high energy absorbing capacity, and having an remarkable effect as a means, e.g., of preventing the overturning and falling of an equipment composition in overturning prevention equipment and stone falling prevention equipment or preventing the collapsing of the structure. <P>SOLUTION: The rope comprises austenite, and the rope is obtained by wire-drawing a steel wire stock having a specified chemical componential composition, subjecting the same to twisting, and thereafter performing austenite formation heat treatment thereto. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an energy absorption rope suitable for, for example, a fall prevention facility or a fall rock prevention facility.

Wire ropes used for fall prevention equipment and rock fall prevention equipment are required to have strength and energy absorption performance. Conventionally, a so-called GC rope (3 × 7 structure) subjected to galvanization or aluminum galvanization has been used as a wire rope for such applications, and it has been installed with the expectation of absorbing the energy of fallen objects due to its elastic elongation.
However, in this method of absorbing energy within the rope elastic range, from the viewpoint of energy absorption efficiency, when the energy of falling objects is large, either a very thick rope or a large number of ropes will be used. In addition, incidental equipment such as anchors as fixing parts had to be large.

As a countermeasure against this, the applicant proposed Prior Document 1. In this prior document, a plurality of wire ropes having relatively different lengths are attached to an object, and the energy is absorbed by breaking the rope with a short length by sequentially breaking the rope with the short length, and then The long rope absorbs the remaining energy absorbed by the short rope.
However, in actuality, a considerable amount of non-uniform force is applied to each of the rope strands, leading to breakage from a wire with a heavy load, and there is a concern that it is difficult to absorb sufficient energy.

JP 2004-278256 A

  The present invention has been made to solve the above-described problems, and the object of the present invention is to have excellent strength characteristics and a very large energy absorption capacity, and to provide a fall prevention facility and a falling rock. An object of the present invention is to provide a practical and effective energy absorption rope as a means for preventing the fall or fall of equipment components in a prevention equipment or the like, or a means for preventing the structure from collapsing.

  In order to achieve the above object, the energy absorption rope of the present invention is C: 0.10 to 0.40% in mass%, Si: 0.5 to 2.0%, Mn: 0.2 to 2.5%, sol. Al: A rope using a steel wire containing 0.10% or less and the balance being Fe and inevitable impurities, and the steel wire contains 10% or more of retained austenite by volume ratio in the structure It is characterized by.

  The rope is made of steel strands containing 10% or more austenite by volume ratio in the structure. When a load is applied to a part of a specific rope while using the rope, the part is induced to work. Strengthened by the formation of martensite and the entire rope is uniformly deformed by dispersing the deformation in other parts, so the energy absorbed until the rope breaks is more than 10 times that of the conventional elastic band absorbing rope, plastic area It can be remarkably increased to more than three times the absorption rope, which enables the rope to be downsized and the generated tension of the applied equipment to be lowered, simplifying equipment components such as terminal structures and intermediate strut structures. Economics that can be ensured.

Preferably, the impact energy absorption amount of rope per meter (Ef) = absorption coefficient (K) · tensile breaking load (Ps) (kN · m), 0.20 ≦ K <1.00. The rope having the above characteristics is preferably manufactured by any one of the following methods.
1) C: 0.10 to 0.40% by mass, Si: 0.5 to 2.0%, Mn = 0.2 to 2.5%, sol. After twisting a steel wire containing Al: 0.10% or less, the balance being Fe and inevitable impurities, the steel wire is heated to a ferrite-austenite two-phase temperature of 730 to 900 ° C. and held for 15 to 180 seconds. Then, it is rapidly cooled to 200 to 500 ° C. at a cooling rate of 10 to 300 ° C./s, held in that temperature range for 15 to 600 seconds, and then cooled to room temperature.
2) By mass%: C: 0.10 to 0.40%, Si: 0.5 to 2.0%, Mn: 0.2 to 2.5%, sol. After twisting a steel wire containing Al: 0.10% or less and the balance being Fe and inevitable impurities, the steel wire is heated to a ferrite-austenite phase region temperature of 730 to 900 ° C. and held for 15 to 180 seconds. Then, gradually cool to 550 to 700 ° C. at 1 to 10 ° C./s, rapidly cool below 10 to 300 ° C./s to 200 to 500 ° C., and hold at that temperature range for 15 to 600 seconds. Allow to cool to room temperature.
According to the above manufacturing method, the rope having the above characteristics can be easily produced industrially, and the rope is drawn after the steel strand having the chemical composition is drawn and burned into the rope, and then the residual Since the special heat treatment for austenite generation is performed, the elongation can be remarkably increased.

Preferably, the strength of each steel wire is determined by loosening the rope, and the rate of reduction in the tensile breaking load (twisting rate) of the twisted rope as it is with respect to the total of these is less than 10%.
Preferably, the yield ratio of the rope is 0.7 or less, and the tensile yield ratio of the steel element wire loosened from the rope is 0.3 to 0.7.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows an example in which the energy absorbing rope according to the present invention is applied to a fall prevention means of ancillary equipment such as a sign post in a highway, high-speed railway, bridge, etc., 100 is a road, 101 is a target equipment, A sign main body 103 is fixed to the upper part of the column 102. The support column 102 is fixed to a side wall (rail) 104 having a lower end rising from a side surface of the road by a fixing bracket 105.

  Reference numeral 1 denotes an energy absorption rope for preventing the fall from the side wall, and each end is connected to a support metal fitting 106 attached to an intermediate portion of the support column 102 and the other end is fixed to left and right fixing metal fittings 107 and 107 fixed to the side wall. The energy absorbing rope 1 is connected when a vehicle that is connected and traveling on the road collides with the support column or an earthquake occurs and the support column is about to fall over or fall off the fixed bracket 105 or the fixed bracket 105. This creates tension and absorbs falling and falling energy.

  Although the structure of the rope 1 is not limited, it is usually configured by twisting a plurality of strands obtained by twisting a plurality of steel strands. FIG. 2 shows an example of such a rope, 2 being a strand and 3 being a steel wire. In this example, 7 strands 2 in which 19 steel strands 3 are twisted are used, and a 7 × 19 structure in which these strands are twisted. However, it goes without saying that the present invention is not limited to this.

The steel strand 3 of the rope 1 of the present invention is C: 0.10 to 0.40%, Si: 0.5 to 2.0%, Mn: 0.2 to 2.5%, sol in mass%. . Al: 0.10% or less is included, the balance is made of Fe and unavoidable impurities, and the steel wire contains 10% or more of retained austenite by volume ratio in the structure.
The reason why the structure contains 10% retained austenite is that when a portion of the rope is plastically deformed under load, the retained austenite contained in the rope becomes work-induced martensite and the strength increases. It prevents the deformation from concentrating because at least 10% is necessary for it to work effectively.

On the other hand, as chemical components, C: 0.10 to 0.40% by mass, Si: 0.5 to 2.0%, Mn: 0.2 to 2.5%, sol. Al: 0.10% or less is included, with the balance being Fe and inevitable impurities.
The reason for the limitation will be explained. C is concentrated in the austenite during the heat treatment, so that it is necessary to stably retain the austenite when cooled to room temperature. This retained austenite, when an external force is applied to the rope, produces martensite due to the processing-induced transformation, which prevents the deformation from being localized and contributes to the improvement of the energy absorption capacity of the rope. If it is less than 0.1%, 10% or more of retained austenite cannot be secured by the production method of the present invention. Moreover, when it exceeds 0.40%, ductility will fall.

Si is effective in increasing the C concentration in austenite when bainite transformation occurs in the temperature range of 200 to 500 ° C., but the effect is less at less than 0.5%, and ductility is exceeded at more than 2.0%. Decreases.
Mn is contained in an amount of 0.2% or more to stabilize austenite, while the upper limit is set to 2.5% in order to prevent a decrease in ductility.
Sol. Al is added in a small amount for deoxidation and fine graining, but the upper limit is made 0.10% so as not to impair the ductility.
The above are the basic components of steel targeted by the present invention. In addition to the above elements and Fe, impurities such as P and S inevitably contained in the steel are included.

  The method for obtaining the rope of the present invention will be described. A steel wire obtained by drawing a rolled wire having the above-described configuration is twisted into a strand by a twisting machine. The twist pitch at this time is preferably about 9 to 11 times the strand diameter. Then, a plurality of the obtained strands are arranged on a twisting machine and twisted to obtain an elemental rope having a target diameter. The twist pitch at this time is preferably about 6.0 to 7.5 times the rope diameter. These are necessary for reducing the twist rate to less than 1% and improving the strength. The “twisting reduction rate” means the rate of decrease in the tensile breaking load of the rope as it is after twisting the rope and obtaining the strength of each steel wire.

The raw rope is then heat-treated for residual austenite. For this, the raw rope may be continuously heat-treated in-line, or may be wound around a coil having a required length and loaded into a heat treatment apparatus.
The conditions for this heat treatment are heating to a ferrite-austenite phase region temperature of 730 to 900 ° C., holding for 15 to 180 seconds, and then gradually cooling to 550 to 700 ° C. at 1 to 10 ° C./s or removing. Without cooling, it is rapidly cooled to 10 to 300 ° C./s to 200 to 500 ° C., held in that temperature range for 15 to 600 seconds, and then cooled to room temperature.
The reason for this condition is that a necessary phase is formed in the structure. Under these conditions, a characteristic that exhibits a large energy absorption ability when subjected to a tensile load is obtained, and the yield ratio of the rope is 0.7. In the following, the tensile yield ratio of the steel wire loosened from the rope is 0.3 to 0.7.

The reason for limiting the production conditions will be described in detail. As shown in FIG. 4, in the state of a rope, it is heated to a ferrite-austenite phase region temperature of 730 to 900 ° C. and held for 15 to 180 seconds. This treatment increases the concentration of C and Mn in the austenite phase. If it is less than 730 degreeC, a carbide | carbonized_material may remain to melt | dissolve and it will become difficult to make a retained austenite 10% or more. When the temperature exceeds 900 ° C., almost the whole is in an austenite state, so the alloy elements in the austenite phase are thinned, and residual austenite is also insufficient. If the heating time is less than 15 seconds, the carbide remains undissolved, and conversely, if it exceeds 180 seconds, a decrease in ductility becomes an issue.

From there, it is gradually cooled to a temperature range of 550 to 700 ° C. at 1 to 10 ° C./s, and further rapidly cooled to 10 to 300 ° C./s to 200 to 500 ° C. is because alloy elements such as C are further austenite. This is because the phase is concentrated and the bainite is transformed to ensure ductility.
When the cooling rate to 550 to 700 ° C. is less than 1 ° C./s, the retained austenite is insufficient due to pearlite transformation, and conversely, when it exceeds 10 ° C./s, ductility is lowered. And if the temperature after slow cooling becomes less than 550 degreeC, ductility will fall by pearlite transformation and conversely when it exceeds 700 degreeC, since there is little ferrite, carbon concentration to an austenite phase will become inadequate. However, this slow cooling is not so effective in securing the amount of retained austenite as compared with other heat histories, and can be omitted depending on the situation.

When the cooling rate from 550 to 700 ° C. is lower than 10 ° C./s, ductility is lowered due to pearlite transformation, and conversely, even if it exceeds 300 ° C./s, the quality is saturated, so there is no operational advantage. . Furthermore, if the temperature after this rapid cooling is less than 200 ° C., austenite becomes unstable due to precipitation of carbides.
Furthermore, the reason why the temperature is maintained in the temperature range of 200 to 500 ° C. is that the bainite transformation is partially performed, C is concentrated in the austenite phase, and a stable state is obtained even at room temperature. If the holding time at that temperature is less than 15 seconds, the bainite transformation becomes insufficient. On the other hand, if the holding time exceeds 600 seconds, carbides are precipitated and ductility is lowered.
These heat treatments can be realized in a batch furnace or a continuous furnace. The constant temperature can be maintained in a furnace, or a continuous system such as salt or fluidized bed can be used. In the case where rope oxidation is an issue, a vacuum or a non-oxidizing atmosphere may be used.

  The present inventor has already used austenite-containing stainless steel wire in Japanese Patent Application No. 2005-314211, drawn it into a strand, further twisted it to make a strand, and twisted a plurality of the strands. In combination with the objective stainless steel rope, a solution heat treated rope was proposed.

When the standard breaking load is Ps (kN), the rope has an absorption coefficient K: 0.25 or more at a shock energy absorption amount Ef = KPs (kN · m) per 1 meter, Exhibits an extremely excellent performance that an average strength of 400 to 900 MPa can be obtained, but its use is limited because a specially expensive material such as austenitic stainless steel is used. In addition, more expensive alloy addition is required to impart strength.
The present invention can provide a high energy absorption rope containing austenite by simple heat treatment without using such expensive alloy elements.

  As described above, the rope of the present invention is heat treated to obtain a product, which is used as shown in FIGS. As shown in FIGS. 1 and 2, the rope has many steel strands twisted together, so when an external force is applied to the rope, the stress applied to the steel strands is not uniform. The steel wire with the highest stress undergoes plastic deformation and plastic elongation, but with normal steel ropes, the steel wire is not hardened by work, so this wire breaks with little deformation being shared by other steel wires. The other lines are also broken one after another, and the energy absorption becomes small.

In order to prevent this, the steel wire that is initially plastically deformed needs to be greatly hardened by work hardening, but in the present invention, as described above, a steel wire containing austenite is used as the steel wire. It is work hardened when twisted into the strand and work hardened again with a rope. Although elongation decreases by them, since it heat-processes in the state used as a rope, elongation becomes very large by this process.
And when it puts in the above-mentioned use state and a tensile load is added to a rope, a steel strand will raise | generate a plastic deformation and, thereby, a big work hardening will be obtained by generating a process induction martensite. By doing so, it is possible to distribute the deformation to other lines without concentrating the deformation only on a certain line. As a result, the entire rope steel wire bears a uniform force, and since the local breakage does not occur, the entire rope steel wire can be subjected to a very large deformation.

FIG. 5 shows the relationship of load elongation when a tensile load is applied to the rope.
In the figure, line A is a rope of a type that absorbs energy in the elastic region (hard steel wire type), and an area SA that integrates one load displacement under line A is energy.
Line B is a rope of a type that absorbs energy in a plastic region (ordinary stainless steel wire rope), and area SB obtained by integrating a load displacement under line B is energy.
The line C is a rope of the type that absorbs energy in the plastic region of the present invention, and the area SC obtained by integrating one load displacement under the line C is energy. Compared to “elasticity”, “plasticity” has a large energy absorption, but the elongation is not so large, so the effect is less. In contrast, in the present invention, the martensitic transformation during tensile deformation causes the wire diameter to be thinner in each part of the rope. Since the effect | action which strengthens a certain part is remarkable, a fracture | rupture is suppressed and a remarkable deformability is shown.

Unlike structures that are united like a thin plate structure, the structure of a rope is composed of many composites, that is, many steel strands. It cannot prevent the deformation from concentrating on the line. In the process of elongation and deformation, a great increase in strength must be accompanied. Residual austenite expresses these characteristics. In general, when the material is steel, a large reduction in ductility is inevitable because a large number of steel strands are twisted. In the present invention, such a significant decrease in ductility can be almost completely prevented by performing heat treatment in the rope state.

〔Concrete example〕
Next, specific examples are shown in Table 1. Table 1 shows a prototype of the rope of the present invention, a normal stainless steel rope, and a hard steel wire rope, and the breaking strength, elongation, absorbed energy per lm, and energy absorption coefficient are obtained for each. The results are shown.
The manufacturing conditions of the rope of the present invention and the manufacturing conditions of the conventional rope are as follows.

[About the rope of the present invention]
Structure: 7 × 19, Z twist, diameter 18.0 mm.
Chemical composition: 17% retained austenite.
C: 0.21%, Si: 1.1%, Mn: 1.4%, P: 0.015%, S: 0.004%, sol. Al: 0.032%
Process:
1) A raw material wire having a diameter of 5.5 mm was extracted 13 times until a wire diameter of 1.19 mm was obtained to obtain a steel strand.
2) The 19 steel strands obtained in the above process were twisted and included in the Z direction to produce a core strand, and the 19 steel strands were twisted in the S direction to produce a side strand.
3) Six side strands were twisted in the Z direction on the core strand to produce a rope.
4) Put the wound rope in an annealing furnace, heat to 820 ° C, hold for 60 seconds, gradually cool to 630 ° C at 5 ° C / s, and then rapidly cool to 370 ° C at 50 ° C / s. Then, a heat treatment was performed in which the temperature was maintained for 100 seconds and then cooled to room temperature. (Invention 2)
5) In addition, a rope having a diameter of 28.0 mm was prepared in the same process as described above, and 15% of retained austenite was contained. (Invention 3)
6) On the other hand, a rope having a diameter of 6.3 mm was subjected to the same heat treatment as described above except that the slow cooling from 820 ° C. to 630 ° C. was omitted during the heat treatment. Residual austenite was 13%. (Invention 1)

[Regarding conventional rope 1]
Structure: 7x19, Z twist, diameter 18.0mm.
Chemical composition: Austenitic stainless steel Same as the rope of the present invention.
Process:
After 9 times of extraction in 1), solution heat treatment is performed, then 4 times of extraction is performed, and the same applies to 2) and 3). No step 4).

[Regarding conventional rope 2]
Structure: 7x19, Z twist, diameter 18.0mm.
High carbon steel rope: structure 7 × 19, Z twist, diameter 18.0 mm.
Chemical component composition: hard steel C: 0.62%, Si: 0.20%, Mn: 0.48%, P: 0.016%, S: 0.014%
Process:
1) A raw material wire having a diameter of 5.5 mm is drawn four times to 3.5 mm in the cold, and after 980 ° C. × 1.5 minutes, heat-treated in a lead bath under cooling conditions, and then the wire diameter becomes 1.19 mm. The steel strand was obtained by drawing up to 9 times.
2) The 19 steel strands obtained in the above process were twisted in the Z direction to produce core strands, and the 19 steel strands were twisted in the S direction to produce side strands.
3) Six side strands were twisted in the Z direction on the core strand to produce a rope.

A comparison rope was also produced.
[Comparison rope]
1) Manufacturing process of a rope having the same structure as that of the invention product 2, that is, heated to 820 ° C., held for 60 seconds, gradually cooled to 630 ° C. at 5 ° C./s, and below that at 370 ° C. at 50 ° C./s In the heat treatment in which the sample was rapidly cooled to 100 ° C. and kept at that temperature range for 100 seconds and then cooled to room temperature, the slow cooling step was omitted and the rapid cooling rate to 370 ° C. was 7 ° C./s. (Comparative product 1)
2) In the manufacturing process of the rope having the same configuration as that of Invention Product 2, the slow cooling step was omitted and the holding temperature of 370 ° C was set to 160 ° C. (Comparative product 2)
3) In the manufacturing process of the rope having the same configuration as that of Invention Product 2, the slow cooling step was omitted and the holding temperature was not 370 ° C but 530 ° C. (Comparative product 3)
4) In the manufacturing process of the rope having the same configuration as that of Invention 2, the slow cooling step was omitted and the holding time at 370 ° C. was set to 5 s. (Comparative product 4)
5) In the manufacturing process of the rope having the same configuration as that of Invention 2, the slow cooling step was omitted and the holding time at 370 ° C. was set to 710 s. (Comparative product 5)

FIG. 6 shows the relationship between the absorbed energy per meter of the present invention products 1, 2, 3 and the conventional product 1.2 and the rope breaking load. Table 1 shows the retained austenite volume fraction, breaking load, elongation, absorbed energy per 1 m, and energy absorption coefficient of the present invention products 1, 2, 3, conventional product 1.2 and comparative products 1-5.
As apparent from Table 1 and FIG. 6, the rope of the conventional product 2 has remarkably inferior energy absorption performance, and the rope of the conventional product 1 has somewhat higher energy absorption performance than the conventional product 2, but is still considerably low. On the other hand, it can be seen that the rope of the present invention has extremely high energy absorption performance. This is because the austenite generation heat treatment in the state of the rope increases the ductility, and the austenite contained in the steel strand is transformed into martensite by plastic deformation and strengthened during use. This is because the energy absorption capacity is remarkably enhanced by dispersing and suppressing breakage.
Moreover, it turns out that the comparative products 1-5 which remove | deviated from the heat processing conditions prescribed | regulated by this invention have a low retained austenite volume fraction, and are inferior in energy absorption performance.

  The rope of the present invention is a sacrificial means for preventing the fall or fall of equipment components in a fall prevention equipment or a fall rock prevention equipment (for example, a fall rock prevention fence, a fall rock prevention net), or preventing the structure from collapsing, or It can be used for ropes in fields where energy absorption performance is required, such as impact mitigation means during collision.

(A) is a side view which shows the usage example of the energy absorption rope concerning this invention, (b) is a front view similarly. It is a fragmentary perspective view which shows an example of this invention rope. It is typical sectional drawing which shows an example of this invention rope. It is a diagram which shows the heat processing method of this invention rope. It is a load elongation diagram of this invention rope and a conventional rope. It is a diagram which shows the relationship between the absorbed energy per 1m of this invention rope, and a conventional rope, and a rope breaking load.

Explanation of symbols

1 present rope 2 strand 3 steel strand

Claims (7)

  C: 0.10 to 0.40%, Si: 0.5 to 2.0%, Mn: 0.2 to 2.5%, sol. Al: A rope using a steel wire containing 0.10% or less and the balance being Fe and inevitable impurities, and the steel wire contains 10% or more of retained austenite by volume ratio in the structure Energy absorption rope characterized by.   The energy according to claim 1, wherein 0.20 ≦ K <1.00 when the impact energy absorption amount (Ef) of the rope per meter = absorption coefficient (K) · tensile breaking load (Ps) (kN · m). Absorption rope.   C: 0.10 to 0.40% by mass, Si: 0.5 to 2.0%, Mn = 0.2 to 2.5%, sol. After twisting a steel wire containing Al: 0.10% or less, the balance being Fe and inevitable impurities, the steel wire is heated to a ferrite-austenite two-phase temperature of 730 to 900 ° C. and held for 15 to 180 seconds. And then cooled to 200 to 500 ° C. at a cooling rate of 10 to 300 ° C./s, held in that temperature range for 15 to 600 seconds, and then cooled to room temperature. The energy absorption rope described in 1.   C: 0.10 to 0.40%, Si: 0.5 to 2.0%, Mn: 0.2 to 2.5%, sol. After twisting a steel wire containing Al: 0.10% or less and the balance being Fe and inevitable impurities, the steel wire is heated to a ferrite-austenite phase region temperature of 730 to 900 ° C. and held for 15 to 180 seconds. Then, gradually cool to 550 to 700 ° C. at 1 to 10 ° C./s, rapidly cool below 10 to 300 ° C./s to 200 to 500 ° C., and hold at that temperature range for 15 to 600 seconds. The energy absorption rope according to claim 1 or 2, wherein the energy absorption rope is manufactured by cooling from 1 to room temperature.   The strength of each steel strand is determined by loosening the rope, and the rate of reduction (twisting rate) of the tensile breaking load of the rope as it is twisted with respect to the total thereof is less than 15%. The energy absorption rope described in 1.   The energy absorption rope according to claim 1 or 2, wherein a yield ratio of the rope is 0.7 or less.   The energy absorption rope according to claim 1 or 2, wherein a tensile yield ratio of the steel wire loosened from the rope is 0.3 to 0.7.

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