JPH048499B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a high carbon steel wire rod which is excellent in wire drawability and fatigue resistance after wire drawing. After drawing these wires, they are used, for example, in bridge ropes, various wires for aircraft, long rubber belts, steel tire cords, and the like. (Prior art) High carbon steel wire rods commonly used for wire drawing have the following characteristics: 1. High-speed wire drawing is possible; 2. Excellent fatigue resistance after wire drawing. However, one of the things that adversely affect these properties is hard oxide-based nonmetallic inclusions. In general, Al ₂ O ₃ among oxide inclusions,
Monocompositional inclusions such as SiO ₂ , CaO, TiO ₂ , MgO, etc. have high hardness and are non-viscous. Therefore, it is a well-known fact that in order to produce high carbon steel wire rods with excellent wire drawability, it is necessary to increase the cleanliness of molten steel and to soften oxide inclusions. In this way, as a method for increasing the cleanliness of steel and softening non-viscous inclusions, a method for manufacturing high carbon steel wire rod steel with good wire drawability is disclosed in Japanese Patent Publication No. 57-22969, and a method for producing steel for high carbon steel wire rods with good wire drawability is disclosed in Japanese Patent Publication No. 57-22969. -24961 publication discloses methods for producing ultrafine wires, but the basic idea of these technologies is to create ternary oxide-based nonmetallic inclusions of Al ₂ O ₃ -SiO ₂ -MnO. It was limited to composition control. On the other hand, in JP-A-50-71507, the drawability of the product is improved by making the nonmetallic inclusions into the spacer tight region in the ternary phase diagram of Al ₂ O ₃ , SiO ₂ , and MnO. It was proposed that
-81907 publication reduces harmful inclusions by regulating the amount of Al added to molten steel.
Discloses a method for improving wire drawability. In addition, in Japanese Patent Publication No. 57-35243, regarding the production of steel cord with a non-viscous inclusion index of 20 or less, CaO-containing flux is blown into the ladle of molten steel together with a carrier gas (inert gas) under complete Al regulations. After preliminary deoxidation, it is proposed to soften the inclusions by blowing an alloy containing one or more of Ca, Mg, and REM. However, with these known methods, it is difficult to stably control the composition when modifying ternary nonmetallic inclusions, while when controlling multicomponent nonmetallic inclusions, it is difficult to achieve a low inclusion index. Since it is difficult to achieve this value, improvements in wire drawability and fatigue resistance after wire drawing cannot be expected, and the supply of higher quality wire rods is desired. (Problems to be Solved by the Invention) The object of the present invention is to provide a high carbon steel wire rod with extremely excellent wire drawability and fatigue resistance after wire drawing, such as for bridge ropes and various types of aircraft after wire drawing. The present invention aims to provide wire rods for use in wires, long rubber belts, steel tire cords, etc. (Means for solving the problem) The main points of the means for solving the above problem are (1) specifying the chemical composition of high carbon steel wire rod steel, (2) determining the total oxygen content. (3) to control the amount and composition of non-viscous inclusions by defining them within a certain range;
(4) Lowering the non-viscous inclusion index to make the amount and size distribution of non-viscous inclusions favorable for wire drawability and fatigue resistance after wire drawing;
Together with other constituent elements, the SiO ₂ -MnO-Al ₂ O ₃ ternary inclusions contained in the high carbon steel wire rod are modified into multi-component oxide inclusions with a specific composition range. The objective is to soften the material and lower the non-viscous inclusion index. Considering the plasticity of oxide-based nonmetallic inclusions,
It is known that a single composition or a particularly high content of a specific oxide results in hardness and poor plasticity; however, based on the results of many years of research, the present inventors have We found the optimal value for the combination of and the proportion occupied by inclusions. This is because it is difficult to accurately measure the hardness of non-viscous inclusions of less than 10 μm in wire rods.
This is because we have been measuring the hardness of oxide-based nonmetallic inclusions in steel slabs before wire rolling for many years, and discovered the relationship between hardness and composition. Therefore, with the composition ratio and combination of oxide-based nonmetallic inclusions according to the present invention, the microvitkers hardness (Hv) does not exceed 690, as shown in Table 1 below, and the non-viscous inclusions do not exceed 690. It was confirmed that the property index was also 10 or less. In addition, in order to soften the hardness of non-viscous inclusions to Hv690 or less and to achieve high cleanliness so that the non-viscous inclusion index is 10 or less, the total input Al amount should be 5 to 9.5 g/ In the t-Steel and the first deoxidation, Si and Mn are added, and in the second deoxidation, Ca, Mg, Ba, Ti,
This is achieved by adding two or more of V, Zr, and Na and Al to make the total oxygen content in the wire 15 to 50 ppm, and by specifying the composition and combination of non-viscous inclusions according to the present invention. However, it is clear that the technical idea of the present invention is not limited thereby. Based on the outline of the means for solving the problems according to the present invention as described above, the gist of the present invention is as follows. (1) C: 0.50 to 0.95% Si: 0.15 to 0.35% Mn: 0.30 to 0.90% P: 0.025% or less S: 0.025% or less Carbon steel wire rod consisting of balance iron and unavoidable impurities satisfies the following conditions. A high carbon steel wire rod with excellent wire drawability and fatigue resistance after wire drawing. a) The total oxygen content must be 15 to 50 ppm. b The non-viscous inclusion index of the nonmetallic inclusions contained is 10 or less. c The composition of the non-viscous inclusions is _SiO2 : 25-70%,
MnO: 5-40%, MgO: 40% or less,
_Al2O3 : 35% or less _, CaO: 25% or less, _TiO2 :
6% or less, and the combinations are as follows. In addition to SiO ₂ and MnO, it contains 5% or more of Al ₂ O ₃ or MgO or both, and
A quaternary or higher oxide containing 2% or more of CaO or TiO ₂ or both. d. 80% or more of the counted non-viscous inclusions have the composition c. (2) C: 0.50 to 0.95% Si: 0.15 to 0.35% Mn: 0.30 to 0.90% P: 0.025% or less S: 0.025% or less Carbon steel wire rod consisting of balance iron and unavoidable impurities satisfies the following conditions. A high carbon steel wire rod with excellent wire drawability and fatigue resistance after wire drawing. a) The total oxygen content must be 15 to 50 ppm. b The non-viscous inclusion index of the nonmetallic inclusions contained is 10 or less. c The composition of the non-viscous inclusions is _SiO2 : 25-70%,
MnO: 5-40%, MgO: 40% or less,
_Al2O3 : 35% or less _, CaO: 25% or less, _TiO2 :
6% or less, other oxides 5% or less, and the combinations are as follows. In addition to SiO ₂ and MnO, it contains 5% or more of Al ₂ O ₃ or MgO or both, and
A quinary or higher oxide containing 2% or more of either or both of CaO and TiO ₂ and 5% or less of other oxides d 80% or more of the counted non-viscous inclusions have the composition of c. thing. The present invention will be explained in detail below. A more specific explanation of the combination of compositions of non-viscous inclusions in the high carbon steel wire rod of the present invention is as follows. There are the following nine combinations of inclusion compositions in the above-mentioned item 1 invention. (1) SiO ₂ +MnO+Al ₂ O ₃ +MgO+CaO+TiO ₂ (2) SiO ₂ +MnO+Al ₂ O ₃ +CaO (3) SiO ₂ +MnO+Al ₂ O ₃ +TiO ₂ (4) SiO ₂ +MnO+Al ₂ O ₃ +CaO+TiO ₂ (5) SiO ₂ +MnO+MgO +CaO ( 6) SiO ₂ +MnO+MgO+TiO ₂ (7) SiO ₂ +MnO+MgO+CaO+TiO ₂ (8) SiO ₂ +MnO+Al ₂ O ₃ +MgO+CaO (9) SiO ₂ +MnO+Al ₂ O ₃ +MgO+TiO _2Also , the combinations of inclusion compositions in the invention of item 2 are as follows: It is. (1) SiO ₂ +MnO+Al ₂ O ₃ +MgO+CaO+TiO ₂ +
Other oxides (2) SiO ₂ +MnO+Al ₂ O ₃ +CaO + other oxides (3) SiO ₂ +MnO+Al ₂ O ₃ +TiO ₂ + other oxides (4) SiO ₂ +MnO+Al ₂ O ₃ +CaO+TiO ₂ + other oxides (5) SiO ₂ +MnO+MgO+CaO+Other oxides (6) SiO ₂ +MnO+MgO+TiO ₂ +Other oxides (7) SiO ₂ +MnO+MgO+CaO+TiO ₂ +Other oxides (8) SiO ₂ +MnO+Al ₂ O ₃ +MgO+CaO+Other oxides (9) ) SiO ₂ +MnO+Al ₂ O ₃ +MgO+TiO ₂ +other oxides Next, the reasons for limiting the constituent elements of the present invention will be described. Regarding regulations on steel composition: Widely used as steel for high carbon steel wire rods, JIS G3502,
Killed steel, G3506 piano wire and hard steel wire, are used, and the standards for these are as follows.

[Table] In consideration of the above JIS standards, ease of manufacture, and practical aspects, the present invention has defined the following component ranges. C: 0.50-0.95%: Generally speaking, when it is called high carbon steel wire rod, there is no clear definition of carbon content, but when the wire is drawn particularly thin,
The higher the carbon content, the more disadvantageous the conditions will be. For this reason, the lower limit of carbon content was set at 0.50%, and the upper limit was set at 0.95%, which is the upper limit for commonly used piano wire. Si: 0.15 to 0.35%: Like Mn, Si is an element necessary for deoxidizing the steel of the present invention, and at least the range of JIS hard steel wire is a necessary condition. Mn: 0.30-0.90: Mn is also an element necessary for deoxidizing the steel of the present invention,
The ranges for JIS hard steel wire rod and piano wire rod were set as the lower and upper limits, respectively. P: 0.025% or less, S: 0.025% or less: When drawing high carbon steel wire rod, P and S not only deteriorate the wire drawability but also the ductility after wire drawing, so at least JIS piano It is necessary to set an upper limit equal to that for wire rods. In addition to the above chemical components, the high carbon steel wire rod of the present invention may contain small amounts of additional elements such as Cr, Ni (for example, 0.1% or less each), Nb, and B, which are added to improve material properties. may include. Regarding the regulation of total oxygen content of 15 to 50 ppm: If the total oxygen content is high, blowholes will occur during solidification of molten steel and cause surface flaws, so 50 ppm
Since the amount of non-viscous inclusions will increase in wire rods with an oxygen content exceeding 50 ppm, the upper limit was set at 50 ppm. On the other hand, Al and Mg
15ppm when using a large amount of strong deoxidizer such as
Although it is easy to set the total oxygen amount to the following, it has been confirmed as a result of many years of research that 15 ppm or more is required in order to control the composition of non-viscous inclusions in the wire of the present invention. Therefore, the lower limit was set at 15 ppm. The preferred range is 17-40 ppm. Furthermore, as shown in FIG. 2, when the total oxygen amount is less than 15 ppm and more than 50 ppm, the life of the die becomes extremely poor. From this point of view, the total amount of oxygen is 15
~50ppm. Regarding the regulations for non-viscous inclusion index 10 and below: The amount and size distribution of non-viscous inclusions in oxide-based nonmetallic inclusions in a wire rod affect wire drawability and fatigue resistance after wire drawing. From this point of view, also in the pot of the present invention, it is necessary to keep the amount of non-viscous inclusions as low as possible, but if the amount is 10 or less on the non-viscous inclusion index, other configurations It was confirmed that excellent wire drawability and fatigue resistance after wire drawing could be achieved in accordance with the requirements. This can be seen in Figures 1 and 3.
It is clear from the figure. That is, FIG. 1 shows that when the inviscid inclusion index exceeds 10, the die life decreases, and FIG. 3 shows that when the index exceeds 10, the wire breakage rate becomes extremely high. For the above reasons, in the present invention, the non-viscous inclusion index is defined as 10 or less, preferably 5 or less. Regarding the composition of non-viscous inclusions: The composition of individual inclusions counted as the non-viscous inclusion index changes in various ways depending on the deoxidizing method, but as a result of many years of research and investigation, wire drawability and elongation According to the present invention, the composition of the non-viscous inclusions in a wire rod having excellent post-wire fatigue resistance is defined as follows. (1) The composition of the non-viscous inclusions is SiO ₂ :25-70%,
MnO: 5-40%, MgO: 40% or less, Al ₂ O ₃ :
35% or less, CaO: 25% or less, TiO ₂ : 6% or less, and the combination is as follows: In addition to SiO ₂ and MnO, 5% of either Al ₂ O ₃ or MgO or both 4 containing the above and further containing 2% or more of either CaO or TiO ₂ or both
An oxide of an elementary type or higher. (2) The composition of the non-viscous inclusions is SiO ₂ :25-70%;
MnO: 5-40%, MgO: 40% or less, Al ₂ O ₃ :
35% or less, CaO: 25% or less, TiO ₂ : 6% or less,
Contains 5% or less of other oxides in the following combinations: In addition to SiO ₂ and MnO, it contains 5% or more of Al ₂ O ₃ or MgO or both, and further contains CaO or TiO ₂ A quinary or higher oxide containing 2% or more of either or both of the following and 5% or less of other oxides. The reason for the limitation for each combination of compositions will be explained, but it is difficult to develop the technology for individual compositions of the multi-component inclusions as in the present invention. In the present invention, the upper and lower limits have been set based on research data over many years. In order to lower the index value and soften the inviscid inclusions, which is the object of the present invention, a specific combination of oxide compositions in the multi-component system as described above is required. First of all, it must contain SiO ₂ and MnO, and
A combination of quaternary or higher oxides containing either or both of Al ₂ O ₃ or MgO, and either or both of CaO or TiO ₂ is one combination, and in addition to these oxides, other A combination of five or more elemental oxides containing 5% or less of the oxides. As a result of many years of research, it has been found that when 5% or less of other oxides are contained, it contributes to further softening of the non-viscous inclusions. Regardless of the composition of the non-viscous inclusions according to the present invention, the steel of the present invention is a wire rod with excellent wire drawability and fatigue resistance after wire drawing. These are clear as shown in Table 1 and FIGS. 1 to 3.

【table】

[Table] First, we will explain the reasons for limiting the components that make up the non-viscous inclusions. When SiO ₂ exceeds 70%, it becomes a hard oxide and the non-viscous inclusion index becomes high. on the other hand,
If it is less than 25%, good combination with other oxides cannot be obtained as a multi-component oxide inclusion. Therefore, the range was defined as 25-70%. The preferred range is
It is 35-60%. MnO is substituted or combined for Al and Mg deoxidation, and MnO of 40% or more is not produced. On the other hand, MnO
If it is less than 5%, the non-viscous inclusions become hard, so the range was defined as 5 to 40%. Preferably 8-30
%. When the composition ratio of MgO exceeds 40%, hard MgO
Since it becomes a system inclusion, the range was set to 40% or less. The preferred range is 5-25%. When Al ₂ O ₃ exceeds 35%, the combination of multi-element oxides becomes poor and the balance is lost, and the values of other oxide elements in the inclusions decrease, resulting in hard inclusions as shown in Table 1. Become. This limit is 35%. Preferably it is 25% or less. Next, regarding the combination of Al ₂ O ₃ and MgO, the present invention allows SiO ₂ -based oxides suspended in molten steel to be composited with Ca, Mg, Al, etc. in the second deoxidation step. During the production of wire rods, the non-viscous inclusions in the produced wire become soft, especially when the sum of either Al ₂ O ₃ and MgO or both is 5% or more, and the non-viscous inclusion index becomes low as shown in Table 1. Therefore, the lower limit is defined as 5%. Next, let's talk about CaO. When the content of CaO is high, it generally becomes spherical inviscid inclusions, but when the content is 25% or less and it is a multi-component system as in the present invention, CaO also has the hardness of oxide inclusions. This contributes to lowering the value of the non-viscous inclusion index. Therefore, the upper limit of CaO content is defined as 25% (see Table 1). The preferred CaO content is 1
~20%. Next, let's talk about _TiO2 . Ti is generally an element used for adjusting austenite crystal grains, etc., but no examples have been found where it has been used to lower the value of multi-component oxide-based nonmetallic inclusions, that is, to soften them, as in the present invention. Particularly when the content of TiO ₂ is 6% or less in the non-viscous inclusions having this multi-component composition, softening is effective (see Table 1). Therefore, the content of TiO ₂ was limited to 6% or less. Preferably it is 4% or less. Furthermore, although it is a combination of CaO and TiO ₂ ,
When either or both of TiO ₂ is contained in an amount of 2% or more, the non-viscous inclusions are made softer (first
(see table). Finally, the regulation of 5% or less of other oxides will be described. In order to obtain the multi-component non-viscous inclusions according to the present invention, the composition shown above is necessary, but in addition,
In addition to the secondary deoxidizing elements, V, Ba, Zr, Na, etc. can be added. Including these, trace amounts of oxides such as Cr and K that are unavoidably mixed are referred to as other oxides. If the content of other oxides is within 5%, it contributes to softening of the non-viscous inclusions (see Table 1).
Therefore, the upper limit of the content of these alone or in combination of two or more is specified to be 5%. Next, combinations of these non-viscous inclusion compositions will be explained. All of the 18 combinations of non-viscous inclusions described above exhibit excellent properties. First, it will be shown that (SiO ₂ +MnO) is essential in any combination. As shown in the examples, the non-viscous inclusions made of multi-component oxides according to the present invention are produced after the deoxidation product of SiO ₂ +MnO is produced in the first deoxidation. It can be obtained by compositing SiO ₂ -based deoxidation products in secondary deoxidation. Therefore, as a matter of course, the base SiO ₂ ,
MnO must be present in non-viscous inclusions. Next, Al ₂ O ₃ or MgO will be explained. One of the deoxidizing techniques for producing multi-component oxide-based nonmetallic inclusions according to the present invention is a technology that utilizes the strong deoxidizing effects of Al and Mg and the agglomeration and flotation effect of these inclusions in molten steel. However, as a result of investigating the inclusion composition in the same molten steel, it was found that there is a close relationship between Al ₂ O ₃ and MgO. The results are shown in Table 2. Between Al ₂ O ₃ and MgO, within the composition range of the non-viscous inclusion according to the present invention, the higher the Al ₂ O ₃ content, the lower the MgO content. Conversely, when the MgO content is high, the Al ₂ O ₃ content tends to be low. Accordingly
Specified as containing either Al ₂ O ₃ or MgO, or both.

[Table] Next, we will discuss the stipulation that either CaO or TiO ₂ or both are included. Multi-component oxide-based nonmetallic inclusions such as those of the present invention exhibit various compositional changes depending on the deoxidizing conditions, and in particular, the composition changes to lower the index value and soften the multi-component non-viscous inclusions. is CaO or _TiO2
As a result of many years of research, it has become clear that one or both of these must be present in the non-viscous inclusion, so it has been defined as above. These are also shown in Table 1. Moreover, it has been obtained from the results of many years of research that more than 80% of the non-viscous inclusions of 5μ or more, which are counted by taking into consideration the non-viscous inclusions that are unavoidably mixed in, have the above composition. These long-term data were obtained by counting a large amount of accumulated data of the same and different melted materials, and the slope data is mainly obtained when disassembling a coil of 5.5φ wire rod of the same melted material. Measured values and data from wire coils of different melted materials. Generally, those skilled in the art know 5.5φ and some 4.0φ
The rolled product coils up to this point are called strands, and their cleanliness is measured and graded before being shipped to wire drawing companies. The present inventors have also obtained a large amount of data in order to use this index as an index representing cleanliness. As an example of the results, as shown in Table 2, there are cases in which non-viscous inclusions having a composition outside the composition range of the present invention are contained due to unavoidable contaminants. Therefore, the ratio of the amount of non-viscous inclusions exhibiting a composition within the range of the present invention to the amount of inclusions outside the range is 80% or more. Here, non-viscous inclusions will be explained. Non-viscous inclusions are determined by observing a longitudinal section of a wire through the center line at 200 to 400 times magnification using a microscope, etc.
Refers to B-type or C-type inclusions with a length or thickness of 5μ or more as shown in G0555, and where the length (l) and thickness (d) of each inclusion are 5 or less. Count. Next, the non-viscous inclusion index will be explained. The non-viscous inclusion index is performed by inspecting the entire area of the wire with a microscope over a length twice the diameter of the wire (for example, 5.5 x 1.1 mm in the case of 5.5φ), and determining the size of each non-viscous inclusion. Classified separately, each with 5~
This is the cumulative value multiplied by the following coefficients: 9μ x 1, 10 to 19μ x 5, and 20μ or more x 20. The index counted here measures an area of 60.5 mm ² for a 5.5φ wire, but when the diameter of the wire is different, the value is converted to 60.5 mm ² . The wire diameter is not particularly important. (Function) Through many experiments, the present inventors investigated the relationship between the inviscid inclusion index, die life and wire breakage rate, and the relationship between the total oxygen content and die life by comparing with the conventional technology. Table 1 shows the contents of this example. Here, A to H are steels according to the invention and I to R are steels according to the prior art. Further, the manufacturing methods for the steels of the present invention in Table 1 A to H are as follows. Melting was carried out using an LD converter. When tapping steel from the LD converter into a ladle, a slag stopper ball was used to limit the outflow of LD slag to a minute amount (less than 50m/m thickness). Further, during tapping, a carburizer and deoxidizing alloy iron such as Fe-Mn, Fe-Si, and Si-Mn were added to adjust the composition of C, Mn, and Si. Argon gas was also injected from the bottom of the ladle during the pouring process. The molten steel in the ladle after receiving the steel is so-called killed steel, which has been deoxidized with Si, Mn, etc. After installing this ladle at the position where molten steel is to be refined, in either case, 3 to 15 kg of synthetic slag for molten steel refining/t-Steel and 0.5 to 0.5 kg of CaC ₂ are added.
3Kg/t-Steel was added to the molten steel in the ladle and changed. However, synthetic slag is not added to conventional steel. When the amount of synthetic slag added to the steel of the present invention is small,
The ability of oxide-based inclusions such as Al ₂ O ₃ , MgO, and TiO ₂ to capture synthesis slag is low, and if the amount is too large, heat loss due to formation of synthesis slag is large, and some synthesis slag does not turn into slag. This is because it is wasted, and furthermore, when steel is tapped from an LD converter, the steel is tapped at a significantly high temperature, which increases the amount of fluctuation in oxygen in the steel. Next, Ar was injected from the bottom of the ladle to stir the molten steel, and the amount of Ar was 200/min. After performing the above operations (however, Ar continues to be injected without interruption), in the steel of the present invention, Mg,
A secondary deoxidizer containing two or more of Ca, Ba, Ti, V, Zr, and Na and Al was added to the molten steel as a modifier for SiO ₂ and MnO. Here, the secondary deoxidizing agent is added by press-fitting the deoxidizing agent sealed in an iron container into the molten steel, but it can also be done by spraying the bare molten steel surface with Ar, by wire coating method, or by bullet method. An addition method is also possible. At this time, various ferroalloys and deoxidizing ferroalloys are used.
The total input Al amount including Al is 5.0 per tonne of molten steel.
Adjusted to ~9.5g. In conventional steel, Mg and Ca alloy iron were added at various levels as appropriate. In the present invention, Mg, Ca, Ba, Ti,
V, Zr, and Na were added as a ferroalloy, and Al was adjusted with Al in the ferroalloy or shot Al. After adding the ferroalloy, the components were further finely adjusted and the ladle molten steel refining was completed. The molten steel is continuously cast from a ladle through a tundish, followed by blooming through a heating furnace, billet rolling, and billet refining, and then wire rods are produced by wire rod rolling through a heating furnace, etc. It is something. After that, the 5.5φ wire rod was drawn to 0.175φ or less, and as a result of investigation, the following was found. As mentioned above, the nonviscous inclusion index is 10.
It was found that the wire drawability and fatigue resistance after wire drawing were significantly superior to those of conventional wires because the wire was soft and the wire drawability was below 100. Furthermore, as shown in FIG. 1, with conventional steels, it was not possible to achieve a satisfactory die life in any index. However, in the case of the wire of the present invention, the die life was significantly improved. Furthermore, from the relationship between the index and wire breakage rate shown in FIG. 3, it is clear that the wire breakage rate of the steel of the present invention is significantly reduced compared to the conventional steel. Furthermore, as is clear from Table 1, the amount of non-viscous inclusions can also be reduced. From these results, it was found that under conditions where the inviscid inclusion index is 10 or less, the die life is improved and the wire breakage rate is significantly reduced. Note that the die life index is the amount of wire drawn material per number of dies used. As for the hardness, as shown in Table 1, it is softer than before. In addition, the composition of non-viscous inclusions
The results obtained by the EPMA method were summarized and defined as the composition range shown above. More than 80% of the non-viscous inclusions counted had the above composition. Furthermore, as is clear from Figure 2, the total oxygen amount is 15~
It can be seen that the die life is long in the 50ppm range. Figure 4 shows the results of a rotational fatigue test of a wire drawn to 0.175φ, and shows the relationship between the stress index and the number of repetitions. Stress index is stress TS (tensile strength)
It is corrected by the coefficient of From this figure 4,
It can be seen that the stress is significantly improved when the number of repetitions (times) is 10 ⁵ or more. As a result, when the wire rod of the present invention is drawn and used in steel tires, the life of the tires becomes longer than that of conventional tires, and the maneuverability during high-speed running is improved. Furthermore, impact resistance has been improved, making it less likely to be damaged, and the brakes are more effective. Furthermore, fuel consumption was also significantly reduced. (Effect of the invention) The high carbon steel wire rod of the present invention has a small amount of non-viscous inclusions and has good wire drawability, and is a significantly superior wire rod that can be subjected to wire drawing processing at a high speed even in sizes of 50μ or less than 5.5φ wire rods. It is. Furthermore, since the wire rod of the present invention has a small amount of non-viscous inclusions and is soft, it is significantly superior in both wire drawability (wire breakage and die wear amount) and fatigue resistance compared to wire rods made by conventional methods. In particular, since wire breakage can be reduced, the productivity of wire drawing can be significantly improved. As mentioned above, the wire rod of the present invention has a small amount of non-viscous inclusions and is soft, so it has excellent fatigue resistance. It is an excellent steel material with a wide range of applications such as long rubber belts and steel tire cords, and is a modified steel with oxide-based nonmetallic inclusions that can be used in all Si and Mn-based deoxidized steels. The technical idea of the present invention is applicable to steel types generally referred to as high carbon steel wire rods and various steels manufactured by conventional deoxidation with Si, Mn, Ti, Al, etc., and can be applied to these steel materials. In order to improve the heat treatability and workability of
% or less, or steels in which Nb or B is added, considering the inclusion composition, are naturally included within the scope of the present invention.

[Brief explanation of drawings]

Figure 1 shows the relationship between the non-viscous inclusion index and die life, Figure 2 shows the relationship between the total oxygen content and die life, and Figure 3 shows the relationship between the non-viscous inclusion index and wire breakage rate. A diagram showing the relationship, FIG. 4, is a diagram showing the fatigue results of the steel of the present invention and the conventional steel.

Claims (1)

[Claims] 1 C: 0.50 to 0.95% Si: 0.15 to 0.35% Mn: 0.30 to 0.90% P: 0.025% or less S: 0.025% or less In a carbon steel wire rod consisting of the balance iron and unavoidable impurities, the following A high carbon steel wire rod with excellent wire drawability and fatigue resistance after wire drawing, which satisfies the following conditions. a) The total oxygen content must be 15 to 50 ppm. b The non-viscous inclusion index of the nonmetallic inclusions contained is 10 or less. c The composition of the non-viscous inclusions is _SiO2 : 25-70%,
MnO: 5-40%, MgO: 40% or less,
_Al2O3 : 35% or less _, CaO: 25% or less, _TiO2 :
6% or less, and the combinations are as follows. In addition to SiO ₂ and MnO, it contains 5% or more of Al ₂ O ₃ or MgO or both, and
A quaternary or higher oxide containing 2% or more of CaO or TiO ₂ or both. d. 80% or more of the counted non-viscous inclusions have the composition c. 2 C: 0.50 to 0.95% Si: 0.15 to 0.35% Mn: 0.30 to 0.90% P: 0.025% or less S: 0.025% or less Carbon steel wire consisting of balance iron and unavoidable impurities must satisfy the following conditions. A high carbon steel wire rod with excellent wire drawability and fatigue resistance after wire drawing. a) The total oxygen content must be 15 to 50 ppm. b The non-viscous inclusion index of the nonmetallic inclusions contained is 10 or less. c The composition of the non-viscous inclusions is _SiO2 : 25-70%,
MnO: 5-40%, MgO: 40% or less,
_Al2O3 : 35% or less _, CaO: 25% or less, _TiO2 :
6% or less, other oxides (V, Ba, Zr,
5% or less of Na oxide and trace amounts of oxides that are inevitably mixed (hereinafter referred to as other oxides), and the combinations thereof are as follows. In addition to SiO ₂ and MnO, it contains 5% or more of Al ₂ O ₃ or MgO or both, and
A quinary or higher oxide containing 2% or more of either or both of CaO and TiO ₂ and 5% or less of other oxides d 80% or more of the counted non-viscous inclusions have the composition of c. thing.