JPH0674483B2 - ▲ High ▼ Strength ▲ High ▼ Tough ductility Corrosion resistance Extra fine wire - Google Patents

Description

The present invention relates to a high-strength, high-toughness ductile corrosion-resistant high-carbon steel for ultrafine wires, which is suitable for producing ultrafine wires for steel cords, for example. Regarding wire rods.

(Prior Art) Conventionally, wire rods for ultrafine wires have generally been hot-rolled and then adjusted and cooled to a primary wire drawing, patenting, secondary wire drawing, re-patenting, and brass plating. After that, it is manufactured by the final wet drawing process,
The steel cord is manufactured by twisting the extra fine wire. Here, the diameter of the extra fine wire is generally 0.5 to 0.175 mm, and in the twisting process, several to several tens of the extra fine wires are twisted together to form a steel cord. . In the manufacturing process of such a steel cord, the ultrafine wire after brushing is subjected to 90-98% strong working in the wet drawing process, and further, in the twisting process, it is stronger than the wet drawing process. Subject to torsion, tension and bending stress.

Therefore, it is generally required for wire rods for ultrafine wires not to be broken in the subsequent wire drawing and processing steps, but in particular, it is required not to be broken in the wet wire drawing step and the subsequent twisted wire step for the reason described above. It Such disconnection not only brings about a decrease in productivity and yield in the wet drawing process and the twisting process, but also includes a joint part in the steel cord as a final product, which deteriorates the quality of the steel cord.

In addition, extra fine wires and steel cords have high tensile strength, excellent toughness, ductility and fatigue resistance, and
In order for various products incorporating steel cords to have sufficient durability under various usage environments, in particular,
It is required to have excellent corrosion resistance.

(Object of the Invention) The present invention provides a high-quality wire material for ultrafine wires that can meet the above-mentioned various requirements, and in particular, has improved corrosion resistance, and at the time of wire drawing and stranded wire. To provide a high-strength, high-toughness ductile, high-carbon steel wire for corrosion-resistant extra-fine wires, which can reduce disconnection at the time, improve productivity during production of extra-fine wires and steel cords, and reduce manufacturing costs. With the goal.

(Structure of the Invention) The high-strength, high-toughness ductile corrosion-resistant ultrafine wire according to the present invention comprises:
% By weight C 0.60 to 0.90%, Si 0.05% to less than 0.5%, Mn 0.30 to 0.90%, P 0.04% or less, S 0.04% or less, Al 0.002% or less, Zr 0.05 to 0.30%, and V 0.10 to 0.50. %, The balance iron and unavoidable impurities.

The wire rod according to the present invention has a wire diameter of 0.5 mm or less and a tensile strength by performing wire drawing with a total area reduction rate of 95% or more while subjecting the wire rod to the above-described intermediate heat treatment. It is possible to give ultrafine wires of 230 kgf / mm ² or more.

The reason for limiting the chemical components in the wire according to the present invention will be described.

In order for the ultrafine wire having a diameter of 0.5 mm or less to have a strength of 230 kgf / mm ² or more, according to the present invention, the wire has a C addition amount of 0.60.
% Or more is required. The higher the amount of C in the wire rod, the easier it is to obtain a high-strength wire rod. However, at the time of final wet drawing of the wire rod and during twisting of the obtained ultrafine wire, disconnection occurs at the welded portion and the C segregation portion. In addition, proeutectoid cementite occurs in the wire rod after hot rolling and adjustment cooling, and in the wire rod after heat treatment during wire drawing to extra fine wires and its twisting, and the wire drawability after that is significantly deteriorated. However, the upper limit of the amount of C added is 0.90% because it causes wire breakage during wire drawing and working.

Si is an element necessary for deoxidation of steel, so at least 0.05% is added. If the addition amount is less than 0.05%, deoxidation is not sufficiently performed. On the other hand, in order to perform sufficient deoxidation, it is necessary to add the amount specified in JIS hard steel material or piano wire or more, but when adding 0.5% or more, ultrafine wire and steel cord Not only deteriorates the toughness and ductility of
The weldability of the wire in the welding operation performed during the production of the steel cord deteriorates, and the frequency of wire breakage during wire drawing and twisting increases. On the other hand, it is generally known that Si increases the activity of C in steel and accelerates the decarburization reaction, thus deteriorating the surface properties of wire products. Here, generally, in the steel grade of the present invention, as a method of removing the scale generated on the surface of the wire rod after rolling, mechanical descaling (rollback is applied to the surface of the wire rod to break the scale and remove the scale). MD) method is used, but Si is
It is known as an element that significantly deteriorates MD properties. Therefore, in the present invention, the amount of Si is set to 0.05% or more and less than 0.5%.

Mn is also added for deoxidation similarly to Si, but at the same time, it has the effect of improving hardenability and increasing tensile strength. To effectively develop this effect, it is necessary to add 0.30% or more, but when it is added in excess of 0.90%, the segregation tendency of the components becomes strong, and the toughness and ductility are reduced. . Therefore, the amount of Mn added is 0.30-0.90%
The range is.

In order to prevent wire breakage in the stranded wire process, it is important to reduce the pull-out stress during wire drawing, which is the cause of the wire breakage, and suppress the development of microcracks during wire drawing. It is also important to reduce the content of Al and improve the toughness and ductility of the wire. Therefore, in the steel of the present invention, the S and P contents in the wire material steel are each 0.04% or less, preferably 0.02% or less.

Al is an element for generating a non-ductile inclusions mainly composed of _{Al 2 O 3, MnO-Al} 2 O 3 Al 2 O 3 , such that an important cause of breakage occurring during the production of steel cord. These non-ductile inclusions have a detrimental effect not only on the final wet drawing process but also on the die life, and also deteriorate the fatigue properties of the steel cord and the ultrafine wire for it. Therefore, in the present invention, the amount of Al is set to 0.002% or less so as to avoid disconnection due to the inclusions and not to cause the above-mentioned harmful effects.

V disperses as fine carbonitrides, does not coarsen the austenite grain size and nodule size, and has the effect of narrowing the pearlite lamella spacing, and is therefore effective in improving wire drawability. At the same time, refining the austenite grain size and nodule size prevents microcracks that tend to occur during wire drawing, and also suppresses the development of the generated microcracks, which also has the effect of reducing the rate of wire breakage. Further, V improves the corrosiveness of the wire and steel cord.

In the present invention, V must be added at 0.10% or more in order to effectively exhibit the above-mentioned various effects.
However, even if added in excess of 0.5%, not only the improvement in corrosion resistance saturates, but also the toughness and ductility deteriorate. Therefore, according to the present invention, the addition amount of V is 0.10 to 0.5.
In the range of%, high strength, high toughness, and high ductility are provided, and there are few breakages, and ultrafine wires and steel cord wire rods excellent in corrosion resistance can be obtained.

Zr suppresses the coarsening of the crystal grains, and is also effective in making the nodule size finer, and by such an effect, the wire drawing workability of the wire can be further enhanced, and at the same time,
As with V, by reducing the austenite grain size and nodule size, microcracks that tend to occur during wire drawing are prevented, and since the development of the generated microcracks is suppressed, the rate of wire breakage is also reduced. Have.
Further, Zr also improves the corrosion resistance of the wire rod and the steel cord wire. To obtain such effects effectively, Zr
, It is necessary to add 0.05% or more. However, 0.3%
If added in excess, the effect will not only be saturated, but toughness and ductility will be deteriorated.

Further, in the wire rod according to the present invention, one or two elements selected from the group consisting of Ti and Nb can be added in addition to the above-mentioned elements. In this case, the added amount of these elements is 0.05 to 0 in the total amount with Zr described above.
It is in the range of 30%. Addition of these elements is effective for suppressing coarsening of crystal grains and for making the size of the nodule smaller, and by such an effect, the wire drawing workability of the wire can be further enhanced.

The wire rod according to the present invention can be obtained, for example, by hot rolling steel having the above-described chemical composition and then adjusting and cooling the steel wire, and the wire diameter is usually in the range of 5.0 to 6.4 mm. This wire rod is subjected to the required wire drawing and patenting treatment, brushed if necessary, and then subjected to the final wet wire drawing to obtain a wire diameter reduction of 95% or more.
It has a tensile strength of 230 kgf / mm ² or more when it is made as an ultrafine wire of 0.5 mm or less.

(Effects of the Invention) As described above, in the wire rod according to the present invention, in particular, V
And, due to the effect of Zr, excellent corrosion resistance is provided, and the austenite grain size and nodule size are refined to improve the wire drawing workability, and the micro cracks that are likely to occur in the wire drawing process. It is possible to prevent the occurrence of cracks, suppress the progress of the generated microcracks, and reduce the occurrence rate of wire breakage.

Further, by reducing the amounts of P and S and the amount of Al, disconnection due to non-ductile inclusions is also suppressed.
Therefore, according to the wire rod of the present invention, not only the disconnection does not occur in the final wet drawing step, but also the occurrence of disconnection is suppressed in the twisted wire step in which twisting, tensile and bending stresses larger than in this step are applied. In addition, since the amount of C in the wire is kept relatively large, it is possible to manufacture ultrafine wire and steel cord having high strength and high toughness.

(Example) Hereinafter, the present invention will be specifically described in detail based on examples.

Example A disconnection index of a Katpie disconnection when a steel wire having a chemical composition shown in Table 1 and having a wire diameter of 5.5 mm and a conventional steel wire having a diameter of 0.25 mm is twisted into a steel cord. Is shown in the table. Here, the wire breakage index indicates the number of wire breaks per twisting of a unit weight of the ultrafine wire, and the larger the number of wire breaks, the higher the wire breakage index. In addition, in this example, in order to easily cause the cut wire breakage and to more clearly show the effect of the steel of the present invention, the C content is 0.79 to 0.83%, the wire strength is 310 to 335 kgf /
mm ²

As shown in Table 1, in comparison with conventional steel, addition of Zr and V,
Furthermore, the ultrafine wire obtained from the steel wire rod of the present invention to which one or two of Nb and Ti are added has a wire breaking index significantly reduced as compared with the ultrafine wire made of conventional steel. However, the comparative steel 18 in which the Si content was excessively added in excess of the range specified in the present invention had the wire breaking index significantly deteriorated.

In addition, after removing the plating of the fine wire with a wire diameter of 0.25 mm, 3%
A cycle test in which a salt solution was sprayed for 30 minutes and dried at 50 ° C. for 30 minutes was set as one cycle, and a repeated test of 5 cycles was performed to examine the corrosion weight loss per unit area (mg / cm ² ). As a result, it is shown that the steel of the present invention is superior in corrosion resistance to the conventional steel.

Next, in the production of extra fine wires, it is very important for the intermediate drawn wire to have a large tensile strength after the final lead patenting treatment in order to obtain the final ultra fine wires with high strength. Therefore, a wire having a wire diameter of 5.5 mm made of the steels of the present invention of steel numbers 7 and 17 and the conventional steel of steel number 1 shown in Table 1 is temporarily drawn (finished wire diameter 2.6 mm), primary patenting treatment, secondary wire drawing. After finishing (diameter of finished wire 1.6 mm), final patenting treatment was applied at various lead temperatures. FIG. 1 shows the relationship between the lead temperature and the tensile strength of the 1.6 mm diameter lead patented material thus obtained.

In accordance with the present invention, V and Zr (and optionally Nb
And / or Ti) is added to obtain a wire with high lead patenting strength, it is necessary to raise the lead temperature of patenting by about 30 to 40 ° C as compared with the conventional steel wire. The inventive steel wire rod has a higher drawing value than any conventional steel wire rod in any lead temperature range.

FIG. 2 shows the relationship between various austenitizing heating temperatures and the pearlite nodule size for the invention steels 10 and 14 and the conventional steel 2. It is shown that the steel of the present invention has a smaller nodule size and a fine pearlite structure as compared with the conventional steel.

Further, the wire diameter of the steels 9 and 13 of the present invention and the conventional steel 3 is 5.
Each 5 mm wire rod was subjected to final patenting treatment, brushed, and then finally wet drawn at various processing rates to obtain ultrafine wires. The relationship between the processing rate and the tensile strength of the obtained ultrafine wire at this time is shown in FIG.

The steel wire rod of the present invention has a work hardening rate equivalent to that of the conventional steel wire rod in the final wire drawing process, and therefore, it is possible to easily design the relationship between the final strength and the wire diameter without changing the existing manufacturing equipment. You can

Next, FIG. 4 shows the results of evaluation of the ultrafine wire after the final wet drawing by the toughness and ductility and the drawing value by the tensile test.
The drawing values of the ultrafine wires obtained from the steel wire rods of the present invention 8, 11 and 16 and the conventional steel wire rod 5 are both influenced by the tensile strength of the wire rod, but under a certain tensile strength, The steel wire of the present invention has a higher drawing value than the conventional steel wire.
That is, according to the steel wire rod of the present invention, toughness and ductility are maintained up to a high strand strength.

In order to evaluate the corrosion resistance, the degree of rust generation was examined with a dew-type tester. After subjecting the invention steels 6 and 12 and the conventional steel 4 as the test steels to the secondary patenting treatment, they were brushed. This wire was subjected to the test as it was attached to the wire or after the wire was peeled off.

In the test, while repeating a cycle of 30 ° C. for 3 hours and 20 ° C. for 1 hour, 5% saline solution was sprayed in an atomized state once every 4 hours.

With regard to the brass adhered wire, 23% rust was generated in the conventional steel after 1 week, but 15% in the invention steel 6 and 12% in the invention steel 6.
It was 13%. Also, for the metal stripping wire, 2
After the day, the conventional steel had 75% rust, but the invention steel 6
68% and 12 were 61%. Therefore, it is clear that the wire of the present invention has excellent corrosion resistance.

[Brief description of drawings]

FIG. 1 shows the relationship between the lead temperature, the tensile strength and the drawing value of the 1.6 mm diameter lead patented material obtained by subjecting the steel of the present invention and the comparative steel wire rod to the final patenting treatment at various lead temperatures. The graph shown in FIG. 2 is a graph showing the relationship between the heating temperature and the nodule size for the steels of the present invention and the comparative steels, and FIG. 3 is for the steels of the present invention and the comparative steel wire rods, respectively, after the final patenting treatment and after brushing. Then, a graph showing the relationship between the workability of the ultrafine wire obtained by final wet drawing at various workability and the tensile strength of the obtained ultrafine wire, FIG. It is a graph which shows the relationship between the toughness and ductility of the ultrafine wire after the final wet drawing, and the drawing value by a tensile test about a steel wire rod.

Continuation of the front page (56) Reference JP-A-54-39315 (JP, A) JP-A-52-12611 (JP, A) JP-A-62-77418 (JP, A) JP-A-62-4859 (JP , A)

Claims (2)

[Claims] 1. By weight%, C 0.60 to 0.90%, Si 0.05% or more, less than 0.5%, Mn 0.30 to 0.90%, P 0.04% or less, S 0.04% or less, Al 0.002% or less, Zr 0.05 to 0.30%, And V 0.10 to 0.50%, the balance being iron and unavoidable impurities, and a high strength, high toughness ductile corrosion resistant wire for extra fine wires. 2. By weight%, C 0.60 to 0.90%, Si 0.05% to less than 0.5%, Mn 0.30 to 0.90%, P 0.04% or less, S 0.04% or less, Al 0.002% or less, Zr 0.05 to 0.30%, And V 0.10 to 0.50%, and at least one element selected from the group consisting of Nb and Ti in a total amount of Zr of 0.05 to 0.30%, and a balance of iron and unavoidable impurities. Wire rod for ultra-fine wire with high toughness and corrosion resistance.