KR20080053706A - High strength, high ductility wire rod for drawing - Google Patents

Abstract

Mainly used for tire cords, wire ropes, piano wires, steel wires for bridges, etc., wire rods having excellent strength and ductility after wire drawing are provided.

The wire is composed of the remaining Fe and other unavoidable impurities, including, by weight, C: 0.92-0.97%, Mn: 0.5% or less, Si: 0.2-0.7%, Cr: 0.1-0.5%, and the Si and Cr The sum of the content of satisfies 0.5 ~ 1.0%.

According to the present invention, by providing a wire rod that can secure a high strength and high ductility after the wire processing, it is possible to manufacture a high-strength wire material having excellent wire workability.

Description

High-strength and High-ductility wire rod for wire drawing}

1 is a graph showing the increase in strength after drawing according to the composition of the drawing steel wire of the present invention.

Figure 2 is a graph showing the ductility after drawing according to the composition of the steel wire for drawing of the present invention.

Japanese Laid-Open Patent Publication No. 59-035655

The present invention relates to a high-strength high-ductility wire for wire used for the use of tire cords, wire ropes, piano wire, steel wire for bridges and the like. More specifically, the present invention relates to a wire rod for producing a high-strength wire material having excellent wire workability as it has a high strength and high ductility after wire drawing by appropriately controlling the content of C and simultaneously adding Si and Cr.

In general, there are three methods for obtaining high strength wire for drawing.

First, it is possible to increase the strength of the material itself by adding a large amount of reinforcing elements. Representative examples of such reinforcing elements include carbon. As the strength of the required wire rods gradually increased, the carbon content gradually increased from the vacancy zone to the vacancy zone and from the vacancy zone to the super-vacancy zone.

If the carbon content is increased as described above, the strength of the material may be improved as the fraction of cementite which is a hard phase increases in the wire rod and the lamellar spacing of the pearlite structure becomes dense.

In addition, techniques for adding various alloying elements in addition to carbon have been proposed, and in particular, Japanese Laid-Open Patent Publication No. 59-35655 proposes a technique for increasing the strength of wires by adding Co and Ni as alloying elements.

Secondly, the wire rod for drawing is that the rolled wire is drawn and heat treated to be processed into a final wire, the strength can be significantly improved by the work hardening during processing. When the wire is processed, the lamellar spacing can be miniaturized, the work hardening coefficient increases, the work can be hardened due to the accumulation of dislocations, and the like.

Third, the strength can be improved by increasing the fresh strain of the material separately from the above. In this case, the fresh strain of the material is closely related to the ductility of the material, and thus the material itself may be advantageously improved in strength as it is easily processed without breaking the wire during drawing.

However, since the above methods are not acting independently but are related to each other to change the strength of the wire rod, it may be limited to increase the strength by controlling them independently.

That is, when a large amount of alloying elements are simply added to improve the strength of the wire, problems such as disconnection may occur due to poor ductility of the wire in the subsequent wire manufacturing process after wire rod rolling. Therefore, in order to improve the strength after processing, it is necessary to consider various factors from various viewpoints.

The present invention is to improve the above-mentioned conventional problems, to provide a wire for high-strength ductility after the wire processing by the micronization of the pearlite layer structure by the addition of Si and Cr at the same time while controlling the content of C appropriately. , Its purpose is.

The present invention for achieving the above object, by weight, C: 0.92-0.97%, Mn: 0.5% or less, Si: 0.2-0.7%, Cr: 0.1-0.5%, including the remaining Fe and other unavoidable impurities Formulated, the sum of the content of Si and Cr relates to a high-strength high-ductility wire for wire drawing that satisfies 0.5 ~ 1.0%.

In addition, the present invention comprises P and S as the impurity, and P and S are each related to a high strength high ductility wire for drawing, characterized in that less than 0.03%.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present inventors have carefully examined the relationship between the carbon content and the strength of the wire rod, which have been added in a large amount in order to improve the strength of the wire rod, and have come to the following conclusion.

In general, as the strength of the wire rod increases, the carbon content generally increases from the subporous area to the superporous area, but according to the results of the present inventors, the strength improvement is no longer increased when the carbon content is increased by a certain level or more. Unexpectedly, the amount of fresh processing decreases, but rather reaches a limit where strength can decrease or can no longer be increased.

Therefore, the upper limit of carbon is limited to a range that allows sufficient fresh processing amount without continuously increasing the content of carbon, and in order to compensate for this, the addition of other alloying elements, in particular, Si and Cr, makes the pearlite layer structure finer. As a result, it was confirmed through the experiment that it is effective to secure the strength and ductility of the wire.

In addition, the present invention may include P and S as impurities, characterized in that the P and S are each 0.03% or less. Hereinafter, the composition range of the steel component of the present invention will be described.

The content of carbon (C) is preferably 0.92 to 0.97%.

When C is a key element to secure the strength or the content thereof exceeds 0.97%, the reduction of the cross-sectional reduction rate (RA) of the steel is reduced, and ultimately, the strength increase due to fresh processing cannot be expected, whereas it is less than 0.92%. It can be difficult to secure the targeted intensity. Therefore, the content of C is preferably limited to 0.92-0.97%.

The content of manganese (Mn) is preferably 0.5% or less.

The Mn is a severe elemental segregation, and if it exceeds 0.5% is very likely to cause low temperature tissue, the content of Mn is preferably limited to 0.5% or less.

The content of silicon (Si) is preferably 0.2 to 0.7%.

Si is an element which plays a very important role in the present invention together with Cr. In the case of C, the strength is slightly increased as the amount of addition increases, while the amount of fresh processing decreases, eventually limiting the increase in strength. In the process of overmasonry, coarse cementite is precipitated to provide a major cracking location in the wire. do. On the contrary, Si plays a role of increasing strength by enhancing solid solution without encouraging the formation of cementite cementite in the pore-forming range. To this end, addition of 0.2% or more is required, while in excess of 0.7%, the ductility of lamellar ferrite may be drastically reduced, which may worsen the freshness. Therefore, the content of Si is preferably limited to 0.2 ~ 0.7%.

The content of chromium (Cr) is preferably 0.1 to 0.5%.

Cr is an element which plays a very important role in the present invention, in addition to Si, thereby improving strength and ductility by miniaturizing the layered structure of pearlite. If the content of Cr is less than 0.1%, it is impossible to secure a sufficient layered microstructured effect. If the content of Cr is more than 0.5%, productivity may be deteriorated by slowing the constant temperature transformation rate. Therefore, the content of Cr is preferably limited to 0.1 to 0.5%.

Silicon (Si) + chromium (Cr): 0.5 to 1.0% is preferable.

The Si and Cr is effectively added to the composite, the strength and ductility are increased together when the content is added 0.5 ~ 1.0%. If the amount is less than 0.5%, the increase in strength is not preferable, whereas if it is more than 1.0%, the ductility may decrease, so the sum of the Si and Cr contents is preferably limited to 0.5 to 1.0%.

The present invention is composed of Fe and other unavoidable impurities in addition to the above components.

In the present invention, P and S are other inevitable impurities, and P and S are preferably 0.03% or less, respectively. When the content of P and S is contained in a large amount, the toughness of the steel is deteriorated, so it is not preferable but it is preferably limited to 0.03% or less in consideration of steelmaking load.

The remaining impurities may be included within the range inevitably included in the steelmaking process.

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLE

Tensile strength and cross-sectional reduction rate of the drawn material, which was prepared by heating the inventive steel 1 and the comparative steels (1 to 4) as shown in Table 1 under the usual process conditions, rolling and cooling the finished wire rod, and then drawing a 20% cross-sectional reduction rate ( RA) was measured.

division Ingredient (% by weight) C Si Mn Cr P S Si + Cr Inventive Steel 1 0.92 0.5 0.3 0.2 0.008 0.009 0.7 Comparative Steel 1 0.92 0.2 0.3 - 0.014 0.008 0.2 Comparative Steel 2 0.92 0.2 0.3 0.2 0.010 0.009 0.4 Comparative Steel 3 0.97 0.2 0.3 - 0.011 0.006 0.2 Comparative Steel 4 0.97 0.2 0.3 0.2 0.010 0.008 0.4

division Tensile Strength (MPa) Cross section reduction rate (%) ε = 0 ε = 1.34 ε = 2.23 ε = 3.15 ε = 3.58 ε = 0 ε = 1.34 ε = 2.23 ε = 3.15 ε = 3.58 Inventive Steel 1 1361 1810 2174 2775 3335 35.8 57.9 49.7 41.3 40.1 Comparative Steel 1 1208 1735 1973 2437 2942 29.5 50.5 55.6 40 38.3 Comparative Steel 2 1240 1745 2040 2554 3102 31.2 55.9 46.2 40 38.6 Comparative Steel 3 1216 1762 1997 2558 2995 25 47.5 42.4 37.7 35.6 Comparative Steel 4 1248 1736 2089 2652 3248 29.1 50 46.8 32.5 29.3 ε = ln (A ₀ / A _f ) [A ₀ : Steel cross section before drawing A _f : Steel cross section after drawing]

As shown in Table 2, in the case of the invention steel 1 satisfying the component range of the present invention, the tensile strength of 3335MPa, the cross-sectional reduction rate of 40.1% at a strain rate of 3.58 to ensure high strength and high ductility after drawing, high strength drawing excellent It can be seen that the production of ash.

However, for the comparative steels (1, 3) without adding Cr, the tensile strength and the ductility were shown as the tensile strength of 3000 MPa or less and the section reduction rate of 38.3% or less at 3.58 strain.

In addition, in the case of comparative steel (2,4) in which Si and Cr are added in a composite but the content does not satisfy the component range of the present invention, the strength and ductility of heat than that of the inventive steel 1 satisfying the component range of the present invention Indicated.

As described above, according to the present invention, it is possible to provide a wire for wire having high strength and high ductility after wire drawing by controlling the content of C and simultaneously adding Si and Cr. In addition, the use of the wire rod for drawing has the effect of providing a high-strength wire rod excellent in the drawability.

Claims (2)

By weight percent C: 0.92-0.97%, Mn: 0.5% or less, Si: 0.2-0.7%, Cr: 0.1-0.5%, including the remaining Fe and other inevitable impurities, the content of the Si and Cr The sum is high strength high ductility wire rod for 0.5 ~ 1.0%. According to claim 1, wherein the impurity comprises a P and S, wherein the P and S are each a high strength, high ductility wire for wire drawing, characterized in that less than 0.03%.

Images