KR0143478B1 - The making method of coil strip with ductile - Google Patents

Abstract

The present invention relates to a coil binding steel and a method for manufacturing the same, which are used for binding hot rolled and cold rolled wire, and have a tensile strength of 85kgf / m㎡ by appropriately adjusting the steel component and its content and adding a recovery annealing process during the manufacturing process. The purpose of the present invention is to manufacture a method for manufacturing a steel strip for binding steel products having excellent elongation of 10.0% or more.

The present invention by achieving the above object is by weight% C: 0.07 0.13%, Mn: 1.0 2.0%, Si: 0.3 0.8%, P: 0.02% or less, S; 0.02% or less, soluble Al: 0.02 0.08%, N: 0.006% or less, Ti: 0.03 0.10% Remainder: Slabs composed of Fe and inevitably contained impurities are homogenized at a temperature range of 1200 to 1250 ° C, and finished at a temperature range of 900 to 950 ° C that is higher than Ar _3. Hot rolled, wound in the temperature range of 500 ~ 700 ℃, cold rolled to the final thickness at 45 ~ 65% reduction rate, and then recovered and annealed in the annealing furnace maintained at the temperature range of 480 ~ 560 ℃. It is an object of the present invention to provide a method for producing a coil binding coil having excellent ductility by bluing in a temperature range of ℃.

Description

Rough manufacturing method for coil coupling with excellent ductility

1 is a graph comparing the tensile strength and elongation rate obtained by tensile test after bluing the inventive steel and the comparative steel according to the present invention

The present invention relates to a coil binding steel and a method for manufacturing the same, which are used for binding hot-rolled, cold-rolled and wire rods, and more specifically, for high-ductility coil binding having a tensile strength of 85kgf / m㎡ or more and an elongation of 10.0% or more. It relates to a general and a manufacturing method thereof.

Packaging steel used for binding cold rolled steel, hot rolled wire and wire rod is required to have sufficient tensile strength and ductility because it can be released or broken by a large load applied to a coil or an external impact. Such packing steel is usually slitng cold rolled steel sheet such as SAE 1527, 1022, etc. containing C: 0.1 0.5% by weight (hereinafter referred to as%) and Mn: 0.5% to 430-470 ° C. It is prepared by blueing (blueing) in a lead bath maintained in the temperature range of. In this case, blueing is a process of forming an oxide film having a desired color on a steel sheet to impart anti-rust properties required for roughly and at the same time securing appropriate strength and ductility required for roughly.

In order to increase the strength and elongation, that is, toughness of the packaging steel produced by the above process, conventionally required for the packaging steel by austempering heat treatment before carbonizing treatment of carbon steel having a high C content or Mn content, such as SAE 1527, etc. Sufficient toughness was secured.

However, in the case of the above method, the installation of expensive induction heating for ostempering requires a significant increase in the price of the product, thereby causing a problem of price burden for the demands of the coil binding coil.

In addition, steel containing high C and high Mn, such as SAE 1527 steel, has difficulty in applying a high productivity tandem cold rolling mill, and thus has a problem of applying a reversible cold rolling mill. This is because butt welding should be performed for continuous operation in the pickling line passing to remove scale formed on the surface during hot rolling, because the welding properties are deteriorated and welding is difficult when the C and Mn contents are increased.

Therefore, when manufacturing the coil binding steel using high carbon and high Mn steel such as SAE 1527 steel, expensive equipment such as pickling line, reversible cold rolling mill, and induction heating furnace must be installed.

In the case of SAE 1022 steel, if the cold rolled steel sheet is directly blued without undergoing an osstempering process, the manufacturability can be increased to 6-8%.

Therefore, the present inventor not only solves the above problems, but also does not have a high content of additive elements such as C, Si, and Mn in the steel, so that welding is possible in the pickling line of the existing integrated steelworks, and as a result, a continuous cold rolling machine having high productivity is used. By conducting recovery annealing for ductile recovery in cold annealing furnace as the material, the research and experiments are carried out to manufacture the coil steel having excellent strength and ductility after bluing treatment. The present invention is limited based on the results.

The present invention provides a method for manufacturing a steel coil for binding steel coil products having excellent ductility of at least 85 kgf / m ㎡ and elongation of at least 10.0% by adjusting the steel component and its content and adding a recovery annealing process during the manufacturing process. I would like to, but its purpose is.

Hereinafter, the present invention will be described.

In the present invention, C: 0.07 ~ 0.13%, Mn: 1.0 ~ 2.0%, Si: 0.3 ~ 0.8%, P: 0.02% or less, S; 0.02% or less, Soluble Al: 0.02 ~ 0.08%, N: 0.006 % Or less, Ti: 0.03 to 0.10% The remainder: relates to a coil binding coil having excellent ductility composed of impurities and inevitably contained impurities.

In addition, the present invention is in weight% C: 0.07 to 0.13%, Mn: 1.0 to 2.0%, Si: 0.3 to 0.8%, P: 0.02% or less, S; 0.02% or less, Soluble Al: 0.02 to 0.08%, N : 0.006% or less, Ti: 0.03 ~ 0.10% Remainder: Slabs composed of Fe and inevitable impurities are homogenized at a temperature range of 1200 to 1250 ° C, followed by finishing hot at a temperature range of 900 to 950 ° C above the Ar ₃ temperature. Rolling, winding in the temperature range of 500 ~ 700 ℃, cold rolling to final thickness at 45 ~ 65% reduction rate, recovery recovery annealing in the annealing furnace maintained at the temperature range of 480 ~ 560 ℃, and then 430 ~ 470 ℃ It relates to a method for producing a coil binding coil by bluing in the temperature range of.

Hereinafter, the present invention will be described in more detail.

In order to achieve the above object, in the present invention, the steel is prepared as described above, and hot rolling, cold rolling, recovery annealing, and bluing to manufacture the steel for binding of the present invention are preferable.

Since the present invention contains a large amount of Si and Mn in addition to carbon, when the carbon content is 0.13% or more, the weldability is deteriorated and welding in pickling lines is difficult, and there is a fear of breakage during continuous cold rolling. If the content is less than 0.07%, the strength is insufficient, so the carbon content is preferably limited to 0.07 0.13%.

Manganese is added to the steel to make the structure of the hot-rolled sheet into a mixed structure of ferrite and perlite. At this time, it is added to 1.0% or more because it is dissolved in cementite constituting the perlite layer structure to harden the material. When added, the reinforcing effect is slowed down and the ductility is deteriorated. Also, the deterioration of weldability makes it difficult to apply to pickling lines and continuous cold rolling mills, so the manganese content is preferably limited to 1.0 2.0%.

Si is added to steel to improve the combination of strength and ductility by making the ferrite and pearlite mixed structure of hot rolled sheet uniform and refined. For this purpose, it should be added more than 0.3% but worsen weldability when more than 0.8% is added. Therefore, the Si content is preferably limited to 0.3 0.8%.

Phosphorus is the substitution type alloy element having the largest solid hardening effect, so when it is added at 0.02% or more, the hardening of steel deteriorates the ductility after bluing treatment. In addition, sulfur is preferably added to 0.02% or more, so the sulfide-based inclusions act as a factor to inhibit the toughness of the steel, so the phosphorous sulfur is preferably limited to 0.02% or less, respectively.

Aluminum is added for the purpose of deoxidation of steel, but if the content is less than 0.02%, the deoxidation effect is small and if excessively added to more than 0.08%, it becomes a factor of material hardening. Therefore, the content is preferably limited to 0.02 0.08%. .

When 0.006% or more of nitrogen is added, the tensile strength after bluing is increased by increasing the amount of AlN or the amount of solid solution nitrogen, but the ductility is lowered. Therefore, the upper limit is preferably limited to 0.06%.

Ti is more than 0.03% because it plays a role of widening the temperature at which recovery annealing can be performed during recovery annealing of cold rolled material and increasing the strength by forming fine precipitates such as TiC on the hot rolled plate. The more it adds, the better. However, when Ti is added in an amount of 0.10% or more, excessive Ti-based oxides are formed, resulting in deterioration of workability such as clogging of nozzles in the steelmaking casting process. Therefore, the Ti content is preferably limited to 0.03 to 0.10%.

Hereinafter, a method of manufacturing the steel having a composition according to the present invention will be described in detail. In the present invention, after heating the steel composition as described above using a converter after heating the continuously cast slab in a temperature range of 1200 ~ 1250 ℃ that can be sufficiently homogenized austenite structure before hot rolling 900 directly above the Ar ₃ temperature 900 It is preferable to finish the hot rolling in the temperature range of 950 ° C. The reason is that when the hot rolling finish temperature is 900 ° C or lower, the temperature of the top, tail and edges of the hot rolled coil is lower than the Ar ₃ temperature. This is because it causes the non-uniformity of the material, and when the temperature becomes 950 ° C or higher, the grains of the hot rolled sheet are coarsened, thereby harming the combination of strength and ductility after bluing. In addition, the hot rolled steel sheet as described above is preferably wound in a temperature range of 500 ~ 700 ℃, the reason is that when the coiling temperature is 700 ℃ or more coarse grains of hot rolled sheet strength and ductility after blueing The lower the coiling temperature of the hot-rolled sheet is better because the combination of H is lowered, but if the temperature is too low below 500 ° C, the hit ratio of the hot-rolled coil is lowered, which is a factor of material variation.

The coiled hot rolled plate is pickled and then cold rolled in a productive continuous cold rolling mill with a cold reduction rate of 45-65%. Of course, cold rolling is also possible to apply a reversible rolling mill. In this case, the cold reduction rate is applied according to the thickness of the desired product, but the lower the cold reduction rate, the better the ductility after blueing. However, if the cold rolling rate is too low below 45%, not only the thickness of the hot rolled sheet should be lowered, but also the tissue recovery temperature is increased to move the bluing temperature to a higher temperature, thereby increasing the energy required for bluing as well as the color of the ash coating. It will also cause deterioration. On the other hand, if the cold reduction ratio is 65% or more, the rolling load is caused during cold rolling, and the ductility after blueing deteriorates.

The purpose of the annealing is to recover the necessary ductility by restoring the tissue from the cold rolled material to the state of recovery tissue immediately before recrystallization. Therefore, if the recovery annealing temperature is too low below 480 ° C, recovery does not occur and cold rolled material remains. If the recovery annealing temperature is higher than 560 ° C, recrystallization proceeds after recovery and the ductility increases, but the strength decreases rapidly. Therefore, it is preferable to limit the recovery annealing temperature of the temperature range of 480 ~ 560 ℃. In this case, it is also possible to use a continuous annealing instead of an annealing for recovery annealing, but in this case, it may be applied as a factor that lowers the productivity due to the property of the present invention to manage the annealing temperature lower than the normal working temperature.

In general, the main purpose of the bluing process is to improve ductility by forming a blue oxide film and restoring tissue to secure rust. In the present invention, the former is mainly an object, and the latter does not play a large role. This is because, in the case of the present invention, the ductility is sufficiently recovered in the recovery annealing process. In terms of oxide film formation to ensure rust resistance, the bluing temperature ranges from 430 to 470 ° C.

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

EXAMPLE

Table 1 shows the chemical components of the inventive steel and the comparative steel. Steels 1 to 3 are steels to which recovery annealing is applied before bluing treatment, and steels 4 to 14 are comparative steels which are directly bluing without recovery annealing treatment.

Steel Nos. 4 and 5 are steels with a small amount of Ti or Nb added to SAE 1022 steel, which is annealed in an annealing furnace after cold rolling. On the other hand, steels 6 to 8 contain a small amount of Ni in SAE 1022 equivalent steel, and steels 9 to 10 correspond to existing SAE 1022 steels. Steels 11 to 14 are steels in which Ti, V, Mo, and Nb are added in small amounts to SAE 1022 steel.

Tensile strength and elongation were measured in a state in which the steel formed as shown in Table 1 was prepared in a coil binding band steel according to the manufacturing process of Table 2 and then blued, and the results are shown in Tables 2 and 1 below. .

As can be seen in Table 2 by weight% C: 0.08 ~ 0.11%, Si: 0.4 ~ 0.6%, Mn: 1.4 ~ 1.6%, P: 0.01 ~ 0.02%, S: 0.005 ~ 0.010%, Soluble Al: 0.03 Inventive steel (1 ~ 3) composed of ~ 0.05%, N: 0.003 ~ 0.005%, Ti: 0.05 ~ 0.06% after homogenizing at 1210 ~ 1240 ℃, temperature range of 920 ~ 950 ℃ above Ar temperature Hot rolled at, and wound at a temperature range of 610 to 640 ° C., followed by cold rolling to a final thickness at a reduction ratio of about 55%, and recovery annealing at an anneal furnace at 520 ° C. at a temperature range of 440 to 460 ° C. The bluing invented materials 1 to 6 exhibit a very excellent material having a tensile strength of 88 kgf / m 2 or more and an elongation of 11% or more.

On the other hand, comparative steels (4, 5), in which a small amount of Ti or Nb was added to SAE 1022 steel, were recovered by annealing in an annealing furnace after cold rolling, and the comparative materials (a, b) had a tensile strength of 91 96 kgf / m㎡. The low elongation rate of 7.3 ~ 8.2% showed that high elongation could not be obtained by applying recovery annealing. In the case of the comparative material (c ~ k) in which the comparative steels (6 to 8) in which the trace amount of Ni was added to the SAE 1022 steel were treated under the conditions of Table 2 above, the tensile strength was 93 99 kgf / m < 2 > In the case of the comparative material (1 to m) treated with the comparative steel (9 to 10) containing no Ni under the conditions of Table 2, the tensile strength was 86 to 95 kgf / m㎡ and the elongation was 0.7 to 7.5%. Elongation is less than 9.0%.

On the other hand, when the comparative steels (11 to 14), each of which added a small amount of Ti, V, Mo, and Nb instead of Ni to SAE 1022 steel, were manufactured under the conditions shown in Table 2 above, the tensile strength was 90 kgf / m regardless of the steel type. Although it became more than ㎡, elongation is very small ductility over 4.2 ~ 6.2%. These results are due to insufficient recovery of the tissues because Ti, V, Mo and Nb are all elements that delay the recovery process of the tissue during the bluing process by the precipitate or the solute element drag effect.

As described above, the present invention is to bluish the SAE 1527 steel by induction heating and then blueing by adding a process of performing recovery annealing by using an ordinary annealing apparatus which is generally owned by an integrated steel mill. The coarse steel for binding with elongation of 10% or more manufacturable can be easily manufactured. Therefore, the present invention does not require pickling equipment, reversible cold rolling equipment, induction heating furnace, etc., which should be provided by the steel maker when SAE 1527 steel is used as coil binding steel, and has a tensile strength of only 85kgf / m㎡. As described above, there is an effect that the steel sheet for high toughness coil binding having an elongation of 10.0% or more can be manufactured.

Claims (1)

Weight% C: 0.07-0.13%, Mn: 1.0-2.0%, Si: 0.3-0.8%, P: 0.02% or less, S; 0.02% or less, soluble Al: 0.02-0.08%, N: 0.006% or less, Ti: 0.03-0.10% Remainder: Slab composed of Fe and inevitably contained impurities is homogenized at a temperature range of 1200-1250 ° C, followed by finishing hot rolling at a temperature range of 900-950 ° C above the Ar ₃ temperature, and 500 Winding in the temperature range of -700 ° C, cold rolling to final thickness at 45-65% reduction rate, recovery-annealing in an annealing furnace maintained in the temperature range of 480-560 ° C, and then temperature of 430-470 ° C The manufacturing method of the coil binding coil excellent in ductility characterized by blueing in the range.