JP3479724B2 - Metal wire for rubber product reinforcement - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal wire for reinforcing rubber products used as a rubber product reinforcing material for tires, conveyor belts, hoses and the like. 2. Description of the Related Art Generally, a metal wire for reinforcing rubber products of this kind is formed into a tire cord or a conveyor cord by twisting a plurality of such wires, and then embedded in rubber of a tire or a conveyor belt, or a hose. A plurality of them are knitted at the time of manufacture and are used by being embedded in rubber of a hose. [0003] The properties required of these metal wires for reinforcing rubber products are that they have sufficient strength to withstand applications in the above-mentioned fields of use and also have toughness, and are excellent in wire drawing workability. And low cost. [0004] High carbon steel wires are widely used as the metal wires for reinforcing rubber products. Usually, a hot rolling material is subjected to several patenting treatments on the way, and the wire is drawn. The wire is finished to a required size through several cold wire drawing steps while preventing the toughness of the drawn material from being lowered for each processing. For this reason, many manufacturing steps were required, and the manufacturing cost was high. [0005] Further, since a high carbon steel wire is used, the die wear during cold drawing is large, and the die must be replaced frequently. Therefore, there has been a problem that the manufacturing cost is increased. The present invention has been made in view of the above-mentioned problems of the prior art, and it has been found that a wire rod having a certain chemical composition is optimally heat-treated, then drawn, and the metal structure is controlled to a certain level. An object of the present invention is to provide a metal wire for reinforcing rubber products, which has excellent strength and toughness, is excellent in wire drawing workability, and can be manufactured at low cost. Means for Solving the Problems When a carbon steel is patented, a pearlite structure is obtained. Pearlite has a structure in which cementite, which is extremely difficult to plastically deform and has high strength, and ferrite, which is soft and has low strength, are alternately layered. Therefore, when a large deformation is applied to carbon steel, ferrite undergoes plastic deformation, but cementite cannot be plastically deformed, so that a large stress is applied to cause a shear fracture to develop into a crack in a metal structure. Since the proportion of pearlite increases as the carbon content increases, the proportion of cementite increases in proportion thereto. Therefore, in the conventional method using a high carbon steel wire, there is a tendency that although the strength is large, the drawability is poor. Conversely, a method using a low-carbon steel wire is conceivable only for the purpose of improving the drawability, but this method does not provide the required strength and toughness as long as it is manufactured under ordinary manufacturing conditions. That is, even if a strong working with a total area reduction of 95 to 99% is performed, a tensile strength of 190 N / mm ² or more cannot be obtained. The present inventor has conducted a deep study on the above contradictory phenomena, which is conventional common knowledge. As a result, even if a low-carbon steel wire is used, the chemical composition is limited, and the size and the size of By controlling the shape and the abundance in an appropriate range, it has been found that a metal wire having excellent drawability and having the same strength and toughness as a high carbon steel wire can be obtained. The present invention has been accomplished. That is, the metal wire for reinforcing rubber products according to the present invention contains 0.10 to 0.35% by weight of C and 0.10% by weight of Si.
0.30% by weight and 0.10 to 0.90% by weight of Mn, the balance being Fe and inevitable impurities, and the carbide particles in the cross section are S ≦ 5 × 10 ⁻³ μm ² (S: carbide particles The cross-sectional area of the carbide particles is approximately elongate or substantially circular, and the total area ratio of the carbide particles in the cross section is 2 to 2.
10%, a metal structure in which the carbide particles are converged, a wire diameter of 0.10 to 0.50 mm, and a tensile strength of 2000 to 3000 N / mm ² . By the way, the above-mentioned various numerical limitations are determined based on the results obtained by a number of experiments, and the outline thereof is as follows. C is an element that contributes to solid solution strengthening and is important for forming carbides and imparting strength. When the content is too large, the workability is reduced. When the content is too small, the required strength cannot be obtained. . In addition, in order to satisfy the size, shape and abundance of the carbide particles according to the metal wire of the present invention, 0.10 to 0.3
It is necessary to add in the range of 5% by weight. [0013] Si needs to be 0.10% by weight or more as a deoxidizing agent. Further, as a solid solution in ferrite as an alloy element, the strength increases as the amount increases, but if the amount is too high, the occurrence of decarburization increases and the drawability is impaired, so the content is set to 0.30% by weight or less. Mn is 0.10 as a deoxidizing agent similarly to Si.
It needs to be at least weight%. Also, it has the function of improving the hardenability, but if it is too much, it will impair the wire drawing workability, so that 0.90
% By weight or less. The cross-sectional area S of the carbide particles is 5 × 10 ⁻³ μm ²
If it is larger, the wire drawing workability is deteriorated, and the strength and toughness are also reduced. Therefore, S is set to 5 × 10 ⁻³ μm ² or less. If the total area ratio of the carbide particles in the cross section is 2% or less, the desired strength cannot be obtained, and if it exceeds 10%, the drawability is reduced. The reason for setting the wire diameter to 0.10 to 0.50 mm is that if the wire diameter is smaller than 0.10 mm, the mechanical strength required for this kind of metal wire is not reached.
If it is larger than m, the flexibility is inferior and the repeated bending fatigue property deteriorates. The tensile strength is from 2000 to 3000 N / mm ²
The reason for this is that if the metal wire is embedded at 2000 N / mm ² or less, when the metal wire is embedded in rubber and used, it cannot withstand the tensile force applied to the metal wire due to the bending deformation of the rubber, resulting in disconnection. 3000 N in the metal wire according to the configuration of the present invention
This is because it is virtually impossible to achieve a tensile strength of / mm ² or more. When the rubber wire for reinforcing a rubber product having the above structure is used by being embedded in a rubber such as a tire or a conveyor belt or a hose, it has sufficient strength and toughness. It can withstand use under various conditions. Further, by controlling the size, shape and abundance of carbide particles in the cross section within an appropriate range,
Even when the wire drawing rate is increased, the occurrence of cracks in the metal structure due to shear fracture of cementite is suppressed. Examples of the present invention will be described below together with conventional examples and comparative examples. The chemical composition of the steel wire used here is shown in Table 1.
And the unit is% by weight. The steel wire used in the conventional example and the comparative example is an ordinary hard steel wire mainly having a changed carbon content. [Table 1] Using these wires, the heat treatment conditions before the final drawing were variously changed, and thereafter, the degree of working in the final drawing was appropriately selected and the drawing was performed. The metal structure in the cross section of the obtained thin metal wire was observed, and the mechanical properties of the thin metal wire were measured. Table 2 shows the results. [Table 2] Experiments Nos. 1, 2, and 3 are examples of the present invention, Examples 4 and 5 are examples obtained by performing a conventional patenting process, and Experiments Nos. 6 and 7 are generally used as a conventional spring material. It is an example of a product manufactured by performing an oil tempering process. The parentheses in the table indicate the patenting processing conditions. The tempered martensite structure in the metal structure after the heat treatment refers to a wire rod which has been subjected to wire drawing or the like in the previous step is heated to a temperature not lower than the A ₁ transformation point (preferably 750 to 950 ° C.).
Austenitized by heating at around), then rapidly cooled (preferably performs oil quenching), fully martensite and further A ₁ below the transformation point after (preferably 350 ° C. to 550 ° C.
This is a structure obtained by performing tempering in (range). The pearlite structure (specifically, a fine pearlite structure) is obtained by a patenting treatment, which is a kind of constant temperature transformation treatment widely used for this type of wire, and after heating to about 1000 ° C. A structure in which ferrite and cementite obtained by using a molten metal such as lead or a molten salt as a cooling medium and quenching in a hot bath at about 550 ° C. are layered with each other. As the mechanical properties after the drawing of the fine wires of Experiment Nos. 1 to 7, tensile strength and elongation drawing were measured. At the same time, wire drawing quality and cost were evaluated. The drawability was estimated based on the true strain ε = 2ln Do / Df (where Do: wire diameter before drawing, Df: wire diameter after final drawing). The specimens obtained by drawing the pearlite structures of Experiment Nos. 4 and 5 have good drawability, but have a large number of steps, and are inferior in cost due to the use of a lead furnace with expensive equipment costs. The samples obtained by drawing the tempered martensite structures of Experiment Nos. 6 and 7 were poor in drawability and could not be processed to the target finished wire diameter. In addition, the cost is inferior due to the large number of steps. These causes are considered to be due to the difference in the shape of the carbide in the metal structure after the drawing and the degree of the carbon content of the wire. On the other hand, Experiment No. 1 of the present invention was used.
Those obtained by drawing a mixed structure of ferrite and pearlite of Nos. 3 to 3 are very excellent in drawability, and are also excellent in cost because the number of steps is small and the die wear during drawing is small. It has been found. Microscopic photographs of the metal structures of Experiment Nos. 1 to 3 of the present invention are shown in FIGS. Granules appearing white in the photograph are carbides. This picture is a magnification of 20,0
This is an electron micrograph taken at a magnification of 00 for about 15 seconds with a 4% picral solution of a corrosive liquid, and the shape of the carbide can be clearly confirmed. The numerical values of the average particle area and the total area ratio of the carbide particles shown in Table 2 were obtained by using the images of FIGS. Note that numbers 4 to 7 are also obtained in the same manner. In the present invention, it is very important that the final wire has excellent drawability.
Conventionally, the important purpose of wire drawing is to reduce the diameter and improve the tensile strength.However, if the tensile strength is too large, many breaks occur during drawing, and Impossible. Therefore, a heat treatment (such as a patenting process) is performed again, and the wire is further drawn. In this case, if the drawability is poor, the working degree cannot be increased, and it is necessary to repeat the heat treatment many times, and the number of dies used increases. As for the patenting treatment with this wire type, the heating temperature is about 1000 ° C. and the lead temperature is around 550 ° C. as described before. If the wire diameter is small, it is difficult to control the temperature. It is very difficult to control the cooling rate between the heating furnace and the lead furnace. On the other hand, when the drawability is good as in the present invention, the workability can be increased and the number of heat treatments can be reduced. Further, since the wire diameter at the time of the final heat treatment can be made larger than before, temperature control is easy, and disconnection at the time of heat treatment hardly occurs. As described above, the present invention uses a low-carbon steel material having a constant chemical composition and has the same strength and toughness as a high-carbon steel wire, and has good drawability. Can be obtained. Therefore, an intermediate heat treatment step can be omitted,
Also, the number of dies used for wire drawing can be greatly reduced,
Further, since the temperature control during the heat treatment is easy and the occurrence of disconnection is reduced, there is a remarkable effect that the cost can be greatly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a magnification 2 showing a metal structure in a cross section of a metal wire for reinforcing a rubber product which is an example (experiment number 1) of the present invention.
It is an electron microscope photograph of 0000 times. FIG. 2 is an electron micrograph (magnification: 20,000) showing a metal structure in a cross section of a rubber wire for reinforcing a rubber product as another example (Experiment No. 2) of the present invention. FIG. 3 is an electron micrograph (magnification: 20,000) showing a metal structure in a cross section of a metal wire for reinforcing rubber products according to another example (Experiment No. 3) of the present invention.

Claims (1)

(57) [Claim 1] C is 0.10 to 0.35% by weight, Si is 0.10 to 0.30% by weight, and Mn is 0.10 to 0.90%.
% By weight, the balance being Fe and unavoidable impurities,
Carbide particles in the cross section are S ≦ 5 × 10 ⁻³ μm ²
(S: average cross-sectional area of carbide particles) shows a substantially elongated shape or a substantially circular shape, the total area ratio of the carbide particles in the cross section is 2 to 10%, and the metal structure mixed with the carbide particles And the wire diameter is 0.10 to 0.50 mm
And a metal wire for reinforcing rubber products having a tensile strength of 2000 to 3000 N / mm ² .