JP2572177B2 - High-strength ultrafine steel wire excellent in stranded wire workability and method for producing the same - Google Patents

Description

[Technical field] The present invention is used as a strand of a steel tire cord, a steel belt cord or the like, and has a brass plating layer having a wire diameter of 0.1 to 0.4 mm and a tensile strength of 400 kgf / The present invention relates to a high-strength ultrafine steel wire excellent in stranded wire workability of not less than mm ² and a method for producing the same.

(Background technology)

The demand for higher strength of ultra-fine steel wire has been further increased in order to reduce weight and improve fatigue strength. Conventionally, ultra-fine steel wire used for reinforcement of automobile tires, industrial belts, etc., after intermediate drawing from hot-rolled high-carbon steel wire, patenting process to a predetermined wire diameter, It is manufactured by performing a final patenting process, performing a plating process for improving wire drawing workability and adhesion to rubber, and performing wet wire drawing to a predetermined wire diameter. For example, a steel tire cord is manufactured by finally twisting a strand manufactured as described above using a twisting machine such as a double twister.

In the manufacturing process as described above, in order to increase the strength of the ultrafine steel wire, it is necessary to increase the wire strength after the final patenting treatment or to increase the final drawing strain. However, if the strength of the wire after final patenting or the strain on wire drawing is increased in order to increase the strength of the ultrafine steel wire, breakage frequently occurs in the stranded wire process after wire drawing, and productivity is reduced. It gets extremely worse. For this reason, for example, SWRS
Diameter using 82A is limit 340kgf / mm ² as a tensile strength capable of strand processing steel wire of 0.3 mm, the production of fine steel wire of no more high strength difficult for industrial there were.

On the other hand, as a conventional finding to improve the workability of the stranded wire of a high carbon steel wire having an increased tensile strength, for example, Japanese Unexamined Patent Publication No.
60-204865, JP-A-63-24046, and Japanese Patent Publication No. 3-23674, each of which regulates chemical components such as C, Si, Mn, Cr, etc. High carbon wires for wires have been proposed. However, as can be seen from the examples, the tensile strength of the steel wire is 350 to 360 kgf / mm ² at the maximum, and there is a limit in increasing the strength of the ultrafine steel wire. In addition, as a conventional finding to improve the fatigue properties of ultrafine steel wire, for example, continuously projecting fine hard particles on the surface of ultrafine wire having a wire diameter of 0.5 mm or less in JP-A-2-179333, There has been proposed a method for continuously producing ultrafine wires having high fatigue resistance by improving residual tensile stress to residual compressive stress. However, since the tensile strength changes the 400 kgf / mm ² or more high-strength fine steel wire the surface layer of the residual tensile stress in the residual compressive stress is requires very high shot peening degree, this result the surface roughness There has been a problem that the brass plating layer on the surface layer of the ultrafine steel wire, which has become thinner by the wire drawing work, is peeled off.

[Disclosure of the Invention]

The present invention has been made in view of the actual situation as described above, and has a wire diameter of 0.1 to 0.4 mm and a tensile strength of 400 k
A steel wire that prevents the increase in the number of breaks in the stranded wire processing process that occurs when manufacturing high-strength extra-fine steel wire of gf / mm ² or more, and realizes a high-strength extra-fine steel wire with excellent stranded wire workability and its It is intended to provide a manufacturing method.

The present inventors first analyzed in detail the fracture surface morphology of broken wires that frequently occurred during the stranded wire processing of a high-strength ultrafine steel wire. In stranded wire processing, torsional stress, tensile stress and bending stress are applied to the steel wire. As a result, as the strength of the steel wire is increased, cracks (delamination) tend to occur along the drawing direction as shown in FIG. 1, and it is apparent that the wire breakage frequently occurs in the stranded wire processing step. It became. Therefore, we analyzed the effects of the chemical composition of the steel wire, the tensile strength after the final patenting process, the wire drawing strain, etc. on the occurrence of delamination, and investigated various means for increasing the strength of ultra-fine steel wires that do not easily cause delamination. investigated.

As means for increasing the strength of ultrafine steel wires, there are selection of a chemical component system having a high tensile strength after patenting treatment, selection of a chemical component system having a high wire drawing work hardening rate, and an increase in drawing strain. High strength means that optimally selects a chemical component system with a high tensile strength and a high wire drawing hardening rate after patenting is the most effective in suppressing delamination, that is, disconnection in the stranded wire processing process It was found that. However, it has been found that there is a limit in increasing the strength of ultrafine steel wires having excellent stranded wire workability by using only chemical components. Second
The figure shows an example of analyzing the relationship between the tensile strength of the ultrafine steel wire and the number of disconnections in the stranded wire processing step. 0.88% C-0.49% Si-0.30% Mn-0.51% Cr system, which is a component system with high tensile strength and high wire hardening rate after patenting treatment (● mark in the figure)
However, if the tensile strength of the ultrafine steel wire exceeds 390 kgf / mm ² , delamination is likely to occur, and the number of disconnections in the stranded wire processing increases rapidly. Note that in the figure, the circles are conventionally used for steel cords.
This shows the case of an alloy of 0.81% C-0.26% Si-0.48% Mn (SWRS82A), and shows that the number of disconnections in the stranded wire processing increases more rapidly.

Therefore, further studies were made on means for suppressing the occurrence of delamination in the high-strength ultrafine steel wire. As a result, if the surface layer of the extra-fine steel wire after wire drawing is plastically deformed,
It has been found that even if the tensile strength exceeds 400 kgf / mm ² , the occurrence of delamination is suppressed and the stranded wire workability of a high-strength ultrafine steel wire is greatly improved. That is, it has been found that if uniform fine and plastically deformed indentations are applied to the surface layer of the ultrafine steel wire, the number of disconnections during the stranded wire processing is drastically reduced. In addition, as a result of a detailed analysis of the effects of indentations on stranded wire workability, the area ratio of indentations, the spacing between indentations, and the depth of indentations are important factors in improving the stranded wire workability of high-strength ultrafine steel wires. It has been found that it is important to control these factors optimally.

It is known that when the tensile strength of the ultrafine steel wire increases, the macroscopic residual tensile stress generated on the surface of the ultrafine steel wire significantly increases. It is considered that the non-uniformity of the residual stress also increases. It is presumed that the reason why the occurrence of delamination is suppressed when a plastically deformed indentation is applied to a high-strength ultrafine steel wire is to reduce the non-uniformity of microscopic residual stress distribution.

Therefore, as a result of studying various methods as a means for imparting uniform fine plastically deformed indentations on the surface of the ultrafine steel wire, it was found that after the wire drawing process, the ultrafine steel wire was subjected to shot peening by air injection using compressed air. Found the most effective.

In other words, the strength of the fine steel wire if Hodokose optimal shot peening even exceed 400 kgf / mm ^2, found that it is possible to produce a high-strength fine steel wire having excellent low twisted workability disconnection times It was.

Such an optimum shot peening treatment can be obtained by a shot peening treatment under extremely weak conditions, compared with a shot peening treatment conventionally performed to improve the fatigue strength. Even if the residual stress remains even, the workability of the stranded wire of the high-strength ultrafine wire can be remarkably improved.

The ultrafine wire according to the present invention is subjected to brass plating on the surface thereof in order to improve the adhesion to rubber, but it is necessary to consider shot peening conditions under such conditions that the plating layer does not peel off. is there.

The present invention has been made based on the above findings, and the steel component of the ultrafine wire is expressed by weight%, C: 0.85 to 1.10%, Si: 0.10 to 0.70%, Mn: 0.20 to 0.60%, Cr: 0.10% ~ 0.60%, Al: 0.005% or less, Ni: 0.10 ~ 2.00%, Co: 0.10 if necessary
The steel wire contains a brass plating layer consisting of Fe and inevitable impurities with a wire diameter of 0.1 to 0.4 mm, a tensile strength of 400 kgf / mm ² or more, 2μm depth of indentation plastically deformed on plating surface
Hereinafter, the interval between indentations is 50 μm or less, and the area ratio of indentations is 10
It provides a high-strength ultra-fine steel wire with excellent stranded wire workability of up to 80%, and a tensile strength of 145 to 165 kg by further patenting a steel wire rod consisting of the above components.
performed brass plating after the f / mm ^2, after drawing the wire diameter 0.1~0.4mm under conditions of 3.7 to 4.5 in true strain, shot particle size; 100 [mu] m or less, shot particles of HV hardness; 700 Above, Sp: 5
High-strength ultrafine steel wire that performs shot peening by air injection using compressed air under the condition of ~ 100 kgf / cm ² · s (Sp = air injection pressure (kgf / cm ² ) × shot peening time (seconds)) Is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a scanning electron micrograph showing an example of a fracture surface broken by the occurrence of delamination during stranded wire processing of a high-strength ultrafine steel wire, and FIG. 2 is the tensile strength and twist of the ultrafine steel wire. FIG. 3 is a diagram illustrating an example of an analysis of the relationship between the number of disconnections during wire processing, and FIG. 3 is a diagram illustrating an example of an analysis of the relationship between the area ratio of plastically deformed indentations on the surface layer of the ultrafine steel wire and the number of disconnections during stranded wire processing. Fig. 4 shows an example of the analysis of the relationship between the residual stress of the surface layer of ultrafine steel wire and the parameter Sp during the shot peening process. Fig. 5 shows the relationship between the residual stress of the surface layer of ultrafine steel wire and the number of disconnections during stranded wire processing. FIG. 6 is a diagram showing an example in which the parameters of the shot peening process are analyzed.
FIG. 7 is a diagram illustrating an example of an analysis of the relationship between Sp and the number of disconnections during stranded wire processing. FIG. 7 is a diagram illustrating an example of an analysis of the effect of the parameter Sp during the shot peening process on the adhesion between the steel cord and the rubber. FIG. 8 is a schematic view showing an indentation of the surface layer of the ultrafine steel wire that has been plastically deformed. FIG. 9 is a scanning electron microscope showing an example of the surface condition of the ultrafine steel wire subjected to the shot peening treatment and the conventional method. 10 is a photograph, FIG. 10 is a partial cross-sectional schematic perspective view of the apparatus of the present invention, FIG. 11 is a partial front cross-sectional view of FIG.
FIG. 12 is a partially enlarged front view of FIG.

[Best mode for carrying out the invention]

 Hereinafter, the present invention will be described in detail.

First, in the present invention, a high-strength ultrafine steel wire having excellent stranded wire workability is defined as a wire that has been cut five times per 1000 kg of weight in the stranded wire processing step of an ultrafine steel wire having a tensile strength of 400 kgf / mm ² or more. It means that: Number of disconnections is 5
If the number of turns exceeds this, the productivity will be reduced, and it cannot be said that the wire is a high-strength ultrafine steel wire having excellent stranded wire workability.

Then and has good drawability as a target of the present invention the tensile strength after patenting treatment in 145~165kgf / mm ^2,
400kgf / m with good stranded wire processing finally by wire drawing
The reasons for limiting the composition of steel to obtain a high-strength ultrafine steel wire of m ² or more will be described.

C: C has an effect of increasing the tensile strength after the patenting treatment and increasing the drawing hardening rate, and can increase the tensile strength of the ultrafine steel wire with less drawing strain. As a result, it is possible to manufacture a high-strength ultra-fine steel wire of 400 kgf / mm ² or more with favorable stranded wire processing. If it is less than 0.85%, the tensile strength after patenting treatment is 145 kgf even if alloying elements are added.
400kgf of interest / mm ² or more that finally because also small difficult drawing rate of work hardening is obtained as a tensile strength of fine steel wire
/ mm ² or higher strength cannot be obtained, and even if the drawing strain is increased to 400 kgf / mm ² or more, the workability of the stranded wire deteriorates. On the other hand, if it exceeds 1.1%, proeutectoid cementite precipitates at the austenite grain boundaries during the patenting process and the wire drawing processability is deteriorated, and wire breakage occurs frequently in the wire drawing process or the stranded wire process, so that the range is 0.85 to 1.10%. Limited.

Si: Si is effective for strengthening ferrite in pearlite and deoxidizing steel. However, if it is less than 0.1%, the above effects cannot be expected, and if it exceeds 0.7%, it is harmful to drawability. Since hard hard SiO ₂ -based inclusions are easily generated, the content is limited to the range of 0.1 to 0.7%.

Mn: Mn is not only necessary for deoxidation and desulfurization, but is also an effective element for improving the hardenability of steel and increasing the tensile strength after patenting treatment. On the other hand, if the content exceeds 0.6%, the above effect is saturated, and the processing time for completing the pearlite transformation during the patenting process becomes too long, and the productivity is reduced. Limited to the range.

Cr: Cr is an effective element that refines the pearlite cementite spacing, increases the tensile strength after patenting, and particularly improves the wire work hardening rate, and improves the stranded workability of high-strength ultrafine steel wire. It is an indispensable element for. If it is less than 0.1%, the effect of the above effect is small, while
%, The ending time of the pearlite transformation during the patenting process is prolonged and the productivity is reduced. Therefore, the range is limited to the range of 0.1 to 0.6%.

Al: If the content of Al exceeds 0.005%, the hardest Al ₂ O ₃ inclusions among the inclusions in the steel are likely to be generated, which may cause disconnection during wire drawing or stranded wire processing. %.

The high-strength ultrafine steel wire excellent in stranded wire workability according to the present invention further contains one or two types of Ni: 0.1 to 2.0% and Co: 0.1 to 3.0% in addition to the above elements. be able to.

Ni: Ni has the effect of improving the drawability of the pearlite generated during transformation during the patenting process and further improving the workability of the stranded wire of high-strength ultrafine steel wire. The effect was not obtained, and even if it exceeds 2.0%, the effect just enough for the added amount is small, so this was made the upper limit.

Like Ni, Co: Co enhances the pearlite that is transformed during the patenting process during wire drawing, improves the stranded wire processability, further increases the pearlite transformation speed, and increases the productivity of the patenting process. There is an effect of enhancing the effect, but if it is less than 0.1%, the effect of the above-mentioned action is insufficient, while if it exceeds 3.0%, the effect is saturated, so the range is limited to 0.1 to 3.0%.

Other elements are not particularly limited, but P: 0.015% or less, S: 0.0
A desirable range is 15% or less and N: 0.005% or less.

Next, the reasons for limiting the tensile strength after the patenting treatment will be described.

When the tensile strength after the patenting treatment is as high as possible, a high-strength ultrafine steel wire can be manufactured under the condition that the wire drawing distortion is small, and as a result, the stranded wire workability is improved. However, when the low-temperature patenting treatment was performed in the above-mentioned component range, the tensile strength was reduced.
If it exceeds 165 kgf / mm ² , pearlite having deteriorated wire drawing property or bainite harmful to wire drawing property is likely to be generated, and breakage frequently occurs in wire drawing and stranded wire processing. Meanwhile patenting or fine steel wire of 400 kgf / mm ² or more high strength for the purpose when the perform tensile strength be less than 145kgf / mm ² at a high temperature is not obtained, or a tensile strength of 400 kgf / mm ² or more In this case, very high wire drawing deformation strain is required in order to reduce the stranded wire workability. Therefore limiting the tensile strength after patenting treatment in 145~165kgf / mm ^2. Within the component range of the present invention, the patenting temperature after the austenitizing treatment is in the range of 560 to 600 ° C.
A tensile strength of 145 to 165 kgf / mm ² can be obtained.

Next is a drawing strain, tensile strength after patenting process is wire diameter by using a steel wire 145~165kgf / mm ² 0.1~0.
The tensile strength of 4mm of fine steel wire to the 400 kgf / mm ² or more is the true strain (true strain = 2 × ln (D / d ), D: patenting treatment during wire diameter, d: final wire diameter ) Requires a wire drawing strain of 3.7 or more, while wire drawing exceeding 4.5 in true strain reduces ductility and leads to frequent wire breakage in the wire drawing or twisting process. Was limited to the true distortion range of 3.7 to 4.5.

Next, the distribution and depth of the plastically deformed indentation of the surface layer of the ultrafine steel wire which is an important point for the improvement of the stranded wire workability of the ultrafine steel wire having a tensile strength of 400 kgf / mm ² or more, which is the object of the present invention The reason for limiting the area ratio and the reason for limiting the shot peening condition for achieving this will be described.

First, the reason for limiting the plastically dented indentation of the surface layer of the ultrafine steel wire will be described. As schematically shown in FIG. 8, the depth (H) of the indentation in the present invention means the depth from the surface of the steel wire, and the interval (L) between the indentations is one between the indentation and the adjacent indentation. Means the distance. Further, the area ratio of the indentation means a value obtained by the area ratio of the indentation = B / A × 100% from the test piece area A and the sum B of the indentation areas included in the test piece area A.
These measurements can be easily performed using a scanning electron microscope.

Indentation depth: When the depth of the indentation exceeds 2 μm, stress concentrates on the indentation and not only frequent wire breakage during stranded wire processing, but also the fatigue strength decreases. On the other hand, when the thickness exceeds 2 μm, the brass plating layer on the surface of the steel wire is easily peeled off, and the adhesion to rubber is also reduced.

Indentation interval: If the indentation is not uniform over the entire length and circumferential direction of the ultrafine steel wire, the effect of improving the workability of the stranded wire is small. For this reason, the interval between the indentations was limited to 50 μm or less.

Indentation area ratio; indentation area percentage is 10% as shown in FIG.
If it is less than 10%, the effect of improving the stranded wire processability is small, while if it exceeds 80%, the effect of improving the stranded wire processability is saturated, the brass plating layer is easily peeled off, and the adhesion to rubber is reduced. Limited to ~ 80%.

FIG. 3 shows the relationship between the area ratio of the indentation of the steel wire manufactured under the conditions of Test No. 16 in Example 2 and the number of disconnections at the time of stranded wire processing.

FIG. 9 shows an example of the high-strength ultrafine steel wire having the above-described indentation. In Figure 9 fine steel wire having a plastically deformed indentation as (a), the number of wire breakage tensile strength at even twisted processing beyond the 400 kgf / mm ² is very low very efficient steel Code production becomes possible. FIG. 2B shows the state of the surface of the ultrafine steel wire when the conventional method, that is, the shot peening treatment is not performed.

Next, the reasons for limiting the conditions of the shot peening treatment for giving the plastically deformed indentation on the surface layer of the high-strength ultrafine steel wire will be described. As a result of various studies on shot peening methods, it became clear that the best way to spray shot particles with an air injection type injection nozzle using compressed air was the best way to perform shot peening processing of ultrafine steel wire efficiently. In the present invention, the above shot peening method is used. In addition, since the purpose of the shot peening process in the present invention is different from that of the shot peening process performed to improve the fatigue strength of gears, shafts, and the like, the shot peening process is very weak compared to the conventional shot peening process. There is a feature. For example, when an attempt was made to measure the arc height using a test piece N of the Japan Spring Association Standard (shot peening work standard),
The arc height under suitable shot peening conditions of the present invention was 0.1 mmN or less. Therefore, the conventional measurement of arc height and coverage indicating the degree of shot peening processing,
In particular, accurate measurement of arc height is difficult. Therefore, in the present invention, as a limiting condition of the shot peening process, a parameter Sp indicating the shot grain size, the HV hardness of the shot grain, and the degree of shot peening are newly introduced. That is, the parameter Sp indicates the degree of shot peening processing, and the air injection pressure of the injection nozzle (kgf / c
m ² ) multiplied by the shot peening processing time (seconds).

Hereinafter, the parameter Sp in the shot peening process
The relationship between and the number of disconnections during stranded wire processing will be described in detail.

FIG. 4 shows the relationship between the parameter Sp (kgf / cm ² · second) and the residual stress (kgf / mm ² ) on the surface layer of the ultrafine steel wire for the steel wire manufactured under the conditions of Test No. 19 in Example 2. This is a case where the parameter Sp is zero, that is, the residual stress is 107 kgf / mm ² when the shot peening according to the present invention is not performed. The residual stress indicates a macroscopic stress of the ultrafine steel wire, and is a value measured by arranging a large number of ultrafine steel wires without gaps by an X-ray stress measurement method.

In this figure, when gradually increasing the parameter Sp is subjected to shot peening of the present invention, the residual stress also drops, the brass plating of the steel wire surface parameter Sp is 100 kgf / cm ² · sec peeling 200kgf / cm ²
・ The residual stress becomes zero in seconds, and the residual stress shifts from the tension side to the compression side thereafter.

Figure 5 is the residual stress of the surface layer fine steel wire in the steel wire of FIG. 4 (kgf / mm ²⁾ and the strand count breakage during processing (times / 1000 kg)
In the example in which the shot peening process according to the present invention was performed (indicated by ● in the figure), the number of disconnections was 5 or less. On the other hand, in the case where the shot peening was not performed (indicated by a circle), the number of disconnections was 15 or more.

In other words, taking into account brass plating peeling, even if a very weak shot peening process with a parameter Sp of 100 kgf / cm ² · sec (about residual stress of about 45 kgf / mm ² ) or less is performed, the processing conditions of the shot peening of the present invention If (shot particle size, shot particle HV hardness) is satisfied, stranded wire workability can be significantly improved.

The lower limit of the parameter Sp is described in the embodiment of FIG.
The figure shows test Nos. 16 (indicated by a circle in the figure) and 28 (indicated by a circle in the figure) in Example 2.
This shows the relationship between the parameter Sp in the case of ()) and the number of disconnections during stranded wire processing. When Sp is less than 5 kgf / cm ² · sec, the number of disconnections sharply increases.

Therefore, in the present invention, the parameter Sp is 5 kgf / cm ²
In less than a second, the area ratio of indentations on the surface of the steel wire is small and uniform indentations cannot be given, so the effect of improving the stranded wire processing of high-strength ultra-fine steel wires is small, while exceeding 100 kgf / cm ² Even when the effect of improving the stranded wire processing is saturated, the peeling of the plating layer on the surface of the steel wire further progresses, and finally the adhesion to rubber deteriorates.
It is limited to 0kgf / cm ² seconds. Air injection pressure is 3 ~
The range is preferably 8 kgf / cm ² , and within this range, it is preferable to adjust the shot peening time so that the Sp parameter is 5 to 100 kgf / cm ² seconds.

In the shot peening treatment of the present invention, the shot particle size and the HV hardness of the shot particles are specified as follows.
If the particle size of the shot exceeds 100 μm, it becomes difficult to uniformly hit the shot particles on the surface of the ultrafine steel wire having a wire diameter of 0.1 to 0.4 mm, and the indentation depth easily exceeds 2 μm, so that the twist is increased. Since the effect of improving the wire workability is small and there is a problem that the brass plating is easily peeled off, the shot particle size is limited to 100 μm or less. The preferred range of the shot particle size is 20 to 80 μm.

It is difficult to give an impression of plastically deformed efficiently and in a short time in the surface layer of high-strength fine steel wire tensile strength is at 400 kgf / mm ² or more is less than shot particles of HV hardness 700; shot particles of HV hardness For this reason, the HV hardness of shot grains was limited to 700 or more.

If the drawing of the ultrafine steel wire after the drawing is less than 30%, the effect of improving the workability of the stranded wire cannot be expected even if the above shot peening is performed.

In the present invention, the brass plating layer on the surface of the steel wire is a plating in which Cu: 50 to 75% and Zn: 25 to 50% by weight%, and the balance consists of unavoidable impurities. In the brass plating, a plating treatment is performed after a patenting treatment in order to improve wire drawing workability and improve adhesion to rubber. The preferred range of the plating thickness is 1 to 3 μm. Although the present invention is directed to a high-strength ultrafine steel wire having a brass plating layer, the effect of improving the stranded wire workability is Cu, S
Even an ultrafine steel wire having a plating layer of n, Ni, Zn or the like or an alloy plating layer of these can exert the effect, and is not limited at all.

FIG. 7 shows the effect of the parameter Sp on the adhesion between the steel cord and the rubber by performing shot peening on the ultrafine steel wire having the brass plating layer. The above adhesiveness is expressed by the pulling load (kgf) when the steel cord is pulled out of the rubber. When the parameter Sp becomes 100 kgf / cm ² sec or more, the adhesiveness with the rubber sharply drops due to the peeling of the brass plating layer. .

As described above, based on the present invention, if the steel material composition, the tensile strength after the patenting process, the optimal selection of the drawing strain, and if the appropriate shot peening process is performed on the ultrafine steel wire after the drawing process , The occurrence of delamination can be suppressed, and the wire diameter 0.1
It is possible to produce high-strength ultrafine steel wire with a strength of 400 kgf / mm ² or more at 0.4 mm.

Next, a shot peening apparatus embodying the present invention will be described. FIG. 10 is a schematic view showing a shot peening treatment apparatus for a fine steel wire, in which 1 is an exhaust hole, 2, 3 are opposed side walls, 4 is a steel wire inlet, 5 is a steel wire outlet, and 6 is Inclined bottom, 7 is shot particle discharge pipe, 8 is ultrasonic vibration generator, 9 is cabinet, 10 and 11 are side walls
Side walls orthogonal to 2, 3; 12 is an axis for rotating the roller; 13 is a roller; 14 _{1 to} 14 ₃ are steel wire winding rollers;
15 is a compressed air supply hose, 16 is a shot grain supply hose,
17 is a nozzle, 18 ₁ to 18 ₃ are shot nozzles, 19 is an inclined wall, 20 is a shot grain collection pipe, 21 is a shot grain sieve, 22 is an uncoiler, 23 is a tension control brake, 24 is a supply side guide roller, 25 Is a winding side guide roller, 26 is a load measuring device, 27 is a winding coiler, 28 is a shot peening treatment device, 29 is a fine steel wire, 30 is a shot grain, 31
Indicates cracked shot grains and uncoiler extra fine steel wire 29
After a desired shot peening process is performed in the shot peening device 28 through the tension control brake 23 and the guide roller 24 from 22, the film is wound up by the winding coiler 27 through the guide roller 25. FIG. 11 shows an ultrasonic vibration generator 8
FIG. 11 is an enlarged front cross-sectional view showing the vicinity of the shot grain discharge pipe 7 of FIG. The shot grain sieve 21 is for selectively collecting broken shot grains, and the ultrasonic vibration generator 8 is for preventing clogging of the sieve 21. FIG. 12 is an enlarged front view of the tension control brake 23.

The tension control brake 23 is a cylinder 32, a compressed air 35
It is composed of a brake 33 and a solenoid valve 34 that move by
It is disposed between the uncoiler 22 and the supply-side guide roller 24 so as to face each other. The solenoid valve 34 is a load measuring device with an electric wiring 36.
The load measuring device 26 is connected to the load measuring device 26 to control the flow rate of air. This flow rate adjustment is activated when the tension of the steel wire 29 falls below the lower limit load preset in the load measuring device 26. Minimum load is 0.5kgf
If it is less than 0.5 mm, the ultrafine steel wire is relaxed, so that an efficient shot peening treatment cannot be performed. The upper limit load is 5 kgf at which the uniform processing effect of shot peening is saturated.

Hereinafter, the shot peening method of the present invention will be specifically described.

(Example 1) Table 1 shows the chemical composition of the test material. These test materials were hot-rolled to a wire diameter of 5.5 mm, subjected to primary drawing, primary patenting, and secondary drawing to a wire diameter of 1.24 to 2.
00 mm. Thereafter, final patenting treatment (austenitizing temperature 950 ° C, lead bath temperature 560 to 600 ° C), followed by brass plating treatment, and wet drawing at a drawing speed of 600 m / min.

Next, shot peening treatment was performed on ultrafine steel wires having wire diameters of 0.15 and 0.2 mm in the following step.

As shown in FIG. 10, it is sent out from the uncoiler bobbin 22 having a diameter of 150 mm at a processing speed of 600 m / min, and the size is 1000 ×
After performing a shot peening process in a 1000 × 1000 mm shot cabinet 9, a 150 mm diameter winding bobbin 2
The shot peening treatment of the present invention was carried out while winding up at 7. The load measuring device 26 measures the tension of the ultrafine steel wire 29 and sends a signal to the control brake 23 when the tension falls below the set lower limit load value.In this test, the lower limit load value is set to 0.5 kg and applied to the steel wire. The applied tension was 0.7 kg on average. The weight of the uncoiler is 7kg. This tension control brake 2
The contact surface with the microfine steel wire 29 is made of hard rubber, and the tension is controlled by pinching or releasing the microfine steel wire 29 by the electric signal of the load measuring device 26 as shown in FIG. The shot grains 30 used are spherical steel beads, and the sieves 21 are used.
Can be replaced at any time according to the test. At this time, in order to eliminate clogging of the sieve 21, the oscillation frequency is 50 kHz.
z, the ultrasonic vibration generator 8 having a high-frequency output of 60 W is arranged at a position closest to the sieve 21 and outside the cabinet 9 among the inclined walls 19, and the degree of sieving of the shot grains 30 is substantially reduced.
100%. Shot nozzle 18 _{1-18 3} nozzles 17 in those air suction type is made of ceramic. Further, the rollers 13 of the roller 14 ₁ to 14 ₃ wound steel wire is ceramic is higher hardness than the shot particles 30 at a diameter 100 mm, axial
Up to three can be deployed at equal intervals with a center-to-center distance of 12 and a groove of 1 mm depth and 1 mm pitch is provided on the surface of the roller 13 so that the ultrafine steel wire 29 can be wound, and the ultrafine steel wire 29 is wound 30 times. Was. However, the roller 14 ₁ to 14 ₃ wrapped steel wire so as to removably freely by the test conditions, and configured by further engaged between the shaft 12 and the roller 13 bearings, so that it can be sufficient to cover the high-speed rotation of the test conditions did. Also,
The shot particles 30 that are not cracked after the shot peening process are collected by the shot particle collection pipe 20 and repeatedly supplied to the shot particle supply hose 16, and the ceramic nozzle 17
More and more continuous projection. The compressed air used dehumidifies and dehumidifies air in the air so that the shot particles 30 do not condense.
The pressure was set to 20% or less, and the pressure was continuously supplied from a compressed air supply hose 15 at a constant pressure of 5 kgf / cm ² by a compressor.

The steel wire thus obtained was sent to a double twister type stranded wire machine, and two wires (pitch: 5 mm) were processed at a rotation speed of 16,000 rpm to process 1000 kg of the steel wire.

Table 2 shows the effects of the indentation depth, indentation interval, and indentation area ratio of the ultrafine steel wire surface layer on the mechanical properties of the ultrafine steel wire, the number of disconnections during stranded wire processing, and rotational bending fatigue. In the stranded wire processing test, the stranded wire workability was evaluated by the number of disconnections per 1000 kg in the stranded wire machine. In this evaluation, the number of disconnections was 5 or less, and if it exceeded this, the productivity was reduced, and the test was rejected. Further, the fatigue characteristics are the results of a rotational bending fatigue test, in which the test was conducted under the conditions of a stress of 100 kgf / mm ² and the number of times until fracture was evaluated. Test Nos. 2, 7, 9 and 10 in Table 2 are examples of the present invention, and others are comparative examples. As can be seen from the table, each of the examples of the present invention has an extremely small number of breaks in the twisting of ultrafine steel wires having a tensile strength of 400 kgf / mm ² or more, and has excellent twistability. It can also be seen that the fatigue characteristics have also been improved. On the other hand, the comparative example N
o. 1, 6, and 8 are all ultrafine steel wires manufactured by a conventional method, and have no indentation on the surface layer. As a result,
The number of disconnections during stranded wire processing is extremely large. Further, in Comparative Examples Nos. 3 to 5, the depth, spacing, and area ratio of the plastically deformed indentations on the surface layer of the ultrafine steel wire were not improved, and the workability of the stranded wire was not significantly improved or the fatigue was low. This is an example in which characteristics have deteriorated. That is, in No. 3, the interval between the indentations was too large, and in No. 4, the area ratio of the indentations was too small, so that the number of disconnections during the stranded wire processing exceeded 5 times in all cases. No. 5 has an indentation depth of more than 2 μm,
The number of disconnections exceeds five, and the fatigue characteristics are also deteriorated.

(Example-2) Table 3 shows the effects of the mechanical properties after the patenting treatment and the drawing conditions on the mechanical properties of the ultrafine steel wire using the test materials shown in Table 1. Table 3 also shows the conditions of the shot peening treatment for improving the workability of the stranded wire of the high-strength ultrafine steel wire and the results of the number of disconnections during the stranded wire processing. The heat treatment conditions for patenting, the drawing conditions, and the method for evaluating the stranded wire workability are the same as the methods described in (Example-1).

Test Nos. 16, 19 to 21, and 25 to 28 in Table 3 are examples of the present invention, and others are comparative examples. As can be seen from the table, in all of the examples of the present invention, the tensile strength of the ultrafine steel wire is 400 kgf / mm ² or more, which is the target, and the depth of the indentation because the shot peening condition is within an appropriate range. In addition, the gap, the area ratio, and the like are optimal, and as a result, the number of disconnections at the time of stranded wire processing is small, and the production of a high-strength ultrafine steel wire excellent in stranded wire workability is realized.

On the other hand, the comparative examples Nos.
82A, Nos. 13 and 14 are the results using SWRS92A. No. 11 has a low tensile strength after patenting due to low C content, and No. 13 has a high tensile strength after patenting but does not contain Cr, so the wire drawing hardening rate is low. , And none of them reached the intended tensile strength of 400 kgf / mm ² or more. Nos. 12 and 14 are examples in which the drawing strain was increased in order to increase the tensile strength of the ultrafine steel wire. No.12
Is frequently broken during wire drawing due to high wire drawing distortion, and N
In o.14, the drawability of the ultrafine steel wire is too low, so even if shot peening is performed on the ultrafine steel wire, the stranded wire workability is not improved.

Further, in Comparative Example No. 15, although Cr was added, the C content was too low, so that a tensile strength of 145 kgf / mm ² or more was not obtained as a tensile strength after the patenting treatment. The tensile strength has not reached 400 kgf / mm ² or more.

No.17 has a tensile strength after patenting of 150kgf / mm
^Although it is as high as ² , the tensile strength of the ultrafine steel wire is less than 400 kgf / mm ² because the drawing strain is too low.

Nos. 18, 22, and 23, which are comparative examples, have an ultrafine steel wire with a tensile strength of 400.
Although kgf / mm ² or more was obtained, this is an example in which stranded wire workability was not improved due to improper shot peening conditions. That is, in No. 18, since the shot peening process was not performed, the number of disconnections during the stranded wire processing is large. No.12 has too large shot particle size, No.23 has parameter Sp
This is an example in which the number of breaks in the stranded wire processing is reduced, but does not reach the target of 5 or less, because the wire is too low. Furthermore, in Comparative Example No. 24, the tensile strength of ultrafine steel wire and the workability of stranded wire also reached the target levels, but the brass plating layer peeled off because the parameter Sp during shot peening was too large. However, this is an example in which the adhesiveness to rubber is reduced.

(Example-3) Table 4 shows the influence of the Sp parameter at the time of shot peening on the number of disconnections at the time of stranded wire processing, the adhesion between rubber and a steel cord, and the rotational bending fatigue characteristics. The shot peening treatment is performed after wire drawing, and the shot particle size is 50 μm.
The test was performed under the conditions of 850 hardness of shot grains. Steel cord is 1x7x0.2 twist cord, rubber is 5th
The compounded rubber shown in the table was used. After embedding a steel cord in unvulcanized rubber at a cord length of 12.5 mm and vulcanizing at 150 ° C for 30 minutes, the adhesiveness between the rubber and the cord was evaluated by measuring the load of pulling out the steel cord from the vulcanized rubber . Rotating bending fatigue characteristics were measured using a steel cord with rubber, and the number of repetitions was 5 using the 15 test staircase method.
The fatigue strength of the cord with rubber at × 10 ⁶ times was determined.

Test Nos. 31, 32, 36 to 38 in Table 4 are examples of the present invention, and others are comparative examples. As can be seen from the table, each of the examples of the present invention has a small number of breaks during the twisting process in an ultrafine steel wire having a tensile strength of 400 kgf / mm ² or more, and has excellent adhesion to rubber. Further, the fatigue strength of the cord is improved as compared with the cord without peening.

On the other hand, Nos. 29 and 35, which are comparative examples, are not subjected to the shot peening treatment, and the wire breakage during the stranded wire processing frequently occurs. In Comparative Example No. 30, the effect of shot peening was small because the parameter Sp during the shot peening process was too small, and the number of disconnections was set at a target value of 5.
Not less than times. Nos. 33, 34, and 39 are comparative examples.
Although the stranded wire workability and the fatigue strength of the cord are excellent, the parameter Sp is too large, so that the brass plating layer on the surface layer of the ultrafine steel wire is peeled off, and as a result, the adhesion to rubber is deteriorated.

In this example, the steel wire was wound around the grooved roller 14 and shot peening was performed while applying tension.However, in the case where the tension was not applied and the tension was increased using a grooveless roller. Table 6 shows the number of disconnections at the time of stranded wire processing as compared with the case where the wire was provided.

In Comparative Example 1, the tension of the ultrafine steel wire was less than the set lower limit load value, and the tension control device was not operated, so that the ultrafine steel wire was loosened, deviated from the proper projection range from the shot nozzle, and was uniformly formed on the surface of the ultrafine steel wire. The shot particles did not collide, and a sufficient effect was not obtained.

In Comparative 2, since the steel wire winding roller having no groove was used, the ultrafine steel wires overlapped on the winding roller and were not uniformly shot-peened in the circumferential direction of the ultrafine steel wire. No improvement effect was obtained.

In contrast, the examples of the present invention all show good results. This means that the processing method suitable for ultra-fine steel wire was completed by having a groove on the surface of the steel wire winding roller in the conventional shot peening processing device capable of winding the ultra-fine steel wire, and that productivity was improved. This is because a device for controlling the tension of the ultrafine steel wire during the shot peening process is attached to prevent the slackening, and the shot peening process can be performed under certain conditions. From these, it is understood that the present invention is an effective shot peening apparatus for ultra-fine steel wire.

[Industrial applicability]

As described in detail above, the present invention selects a chemical composition, a tensile strength after a patenting process, a wire drawing strain optimally, and performs an appropriate shot peening process, thereby producing a fine steel having a wire diameter of 0.1 to 0.4 mm. the tensile strength of the line is 400kgf / mm ²
As described above, it enables the production of high-strength ultra-fine steel wire with excellent stranded wire workability, and can be used for strands such as steel tire cords and steel belt cords. Some are very prominent.

 ──────────────────────────────────────────────────の Continuation of the front page (72) Inventor Hiroshi Sato 23-15 Suzukocho, Kamaishi City, Iwate Prefecture Nippon Steel Corporation Kamaishi Works (56) References JP-A-63-24046 (JP, A) 60-204865 (JP, A) JP-A-2-179333 (JP, A)

Claims (5)

(57) [Claims] (1) C: 0.85 to 1.10%, Si: 0.10 to 0.70% Mn: 0.20 to 0.60%, Cr: 0.10 to 0.60% Al: 0.005% or less, and the balance consists of Fe and inevitable impurities. Steel wire with brass plating layer with wire diameter 0.1-0.4mm and tensile strength 400kgf
A is / mm ² or more, further brass-plated surface plastically deformed indentation depth 2μm below, excellent twisted workability and having an area ratio 10% to 80% of the spacing 50μm or less and the indentation of the indentation High strength extra fine steel wire. 2. The ultrafine steel wire according to claim 1, which contains one or two of Ni: 0.10 to 2.00% and Co: 0.10 to 3.00% by weight. 3. Steel by weight: C: 0.85 to 1.10%, Si: 0.10 to 0.70% Mn: 0.20 to 0.60%, Cr: 0.10 to 0.60% Al: 0.005% or less, the balance being Fe and unavoidable impurities Tensile strength of 145 to 165kgf / mm by patenting wire
After performing the brass plating to ² and drawing the wire with a true strain of 3.7 to 4.5 to a wire diameter of 0.1 to 0.4 mm, shot particle size: 100 μm or less, HV hardness of shot particles: 700 or more Sp; 5~100kgf / cm ² tensile characterized in · sec conditions to perform the shot peening of the air injection system using compressed air strength 400 kgf / mm ²
A method for producing a high-strength ultrafine steel wire excellent in stranded wire workability having the above. Sp = Air injection pressure (kgf / cm ² ) × shot peening processing time (seconds) 4. The method according to claim 3, wherein one or two of Ni: 0.10 to 2.00% and Co: 0.10 to 3.00% by weight are contained. 5. The shot peening process according to claim 3, wherein a tension of 0.5 to 5.0 kgf is applied to the ultrafine steel wire.
The manufacturing method described in the item.