KR100457237B1 - Manufacturing method of drawable high temper grade blackplate for minimum earing ratio - Google Patents

Abstract

The present invention relates to a method for producing a surface-treated disc, which is a material of a can prepared through drawing and ironing or a can undergoing a shallow drawing process, wherein the carbon content is 0.02% to 0.08% by weight and 0.6% or less of Mn. Low-carbon aluminum-kilted steel containing 0.02% to 0.06% of Al, 0.004% or less of N, and 0.0015% or less of oxygen to be hot rolled by ordinary annual rolling, and then pickled by a conventional method. %) Or less (CE is a manufacturing condition factor of 4 × continuous annealing temperature (℃) / 100 + 0.48 × hot rolled winding temperature (℃) / 100 -33.7 × carbon content (%).) By continuous annealing for more than 30 seconds at temperatures below 700 ℃, it has the advantage of manufacturing surface treatment discs for drawing and ironing cans corresponding to all thicknesses and steel grade levels. Something went wrong It is easy to use and wide range of carbon content because it can be sufficiently compensated by changing the annealing temperature after the change of hot rolling temperature and carbon content. In particular, it is possible to significantly reduce the amount of ear generation compared to the prior art.

Description

Manufacturing method of drawable high temper grade blackplate for minimum earing ratio

The present invention relates to a method for manufacturing a surface-treated disc, which is a material of a can prepared through drawing and ironing or a can which is subjected to a shallow drawing process. The present invention relates to a method for producing a high-strength surface treatment disc for processing with low ear formation.

In general, the cans are divided into three parts: the bottom, the body, and the lid, which are composed of three pieces of cans (3-piece cans). -piece cans).

The two-piece can (2-piece can) is manufactured through a process called drawing and then a second drawing or additional ironing process, in particular two-piece can (two-piece can) is a high productivity and light weight of the can As it is mainly used in recent years, the surface treatment disc is tin plated or chrome / chromium oxide plating (Tin Free Steel) to secure lubricity or corrosion resistance, and then cans are processed, and then washed and lacquered again to drink and food Will be saved.

Such cans are thin and have high strength, so the cans are lightened and the safety of the contents is secured. In order to increase the strength of the surface-treated disk, low-carbon cold-rolled steel sheets are continuously annealed to produce T3 and T4. The TD is the Rockwell surface hardness HR30T, which is 57 ± 3 and T4 is 60 ± 3. However, when manufacturing low carbon steel by continuous annealing, it is not excellent in workability. Usually, the plastic anisotropy value (r) is 1.0 to 1.4, which is lower than 1.7 of the soft material, so that processing such as drawing is difficult. Therefore, the most important thing for the hard surface treatment discs, such as T3 and T4, used as a material for two-piece cans, is to minimize the amount of ear formation formed during drawing. Ears formed during drawing not only lower the error rate of the can, but also the ear height is increased by ironing, and the torso of the can is torn.

Ear canning can be easily estimated by evaluating the texture of the surface-treated disc or the in-plane anisotropy value Δr. The in-plane anisotropy value is expressed as [r (0 °) + r (90 °)-2r (45 °)] / 2. The larger the in-plane anisotropy value is, the more the angle of workability in the rolling direction is different. Ear formation is large. Conventionally, in order to suppress this, a very narrow range of composition and manufacturing conditions are limited to produce extremely limited roughness, that is, T3 or T4, so that the roughness cannot be flexibly manufactured according to the shape and required thickness of the can ( Korean Patent Application No. 98-43831), as a method of evaluating ear occurrence, investigated the texture of the aggregates (Japanese Patent Application Laid-open No. Hei 9-263882). The organization has a problem in that the accuracy of the measured value is obtained because very different results are obtained depending on the thickness of the material, and expensive equipment such as X-rey is required for evaluation.

The present invention has been made to solve the problems caused by the conventional methods in view of the above situation, in order to minimize the amount of ear formation drawing by changing the cold reduction rate according to the composition, hot-rolling coil temperature and continuous annealing temperature It is an object of the present invention to provide a method for producing a high-strength surface treatment disc for processing of a relatively wide range of roughness of T3 to T5 having less ear formation at less than 5%.

In order to achieve the above object, the present invention provides a method for producing a high-strength surface-treated disc with low ductility, in which the carbon content is 0.02% to 0.08%, the Mn content is 0.6% or less, the Al content is 0.02% to 0.06%, and the N content is 0.004. Low-carbon aluminum-killed steel containing less than or equal to% and less than or equal to 0.0015% of oxygen is hot rolled by ordinary annual rolling and pickled by a conventional method, followed by a cold rolling reduction of 56.8 + CE (%) or less (CE is 4 × Cold rolling at continuous annealing temperature (℃) / 100 + 0.48 × hot rolled winding temperature (℃) / 100-33.7 × carbon content (%)), followed by continuous annealing for more than 30 seconds at recrystallization temperature and below 700 ℃ Characterized in that.

According to the configuration of the present invention described above, high-strength surface for processing with less ear formation having a cup earing ratio of 5% or less at a drawing ratio of 2.0 or less of T3 to T5 having an in-plane anisotropy value of -0.15 to 0.15. Treatment discs can be produced.

EMBODIMENT OF THE INVENTION Hereinafter, the manufacturing method of the high-strength surface treatment original disk for processing with little ear formation of this invention is demonstrated in detail.

In the present invention, the carbon content was limited to 0.02% to 0.08%, so that the crude degree T3 to T5 should be prepared. The easiest way to produce the T3 to T5 is to increase the carbon content. The solid state of carbon and the presence of carbides increase the strength of the steel.The T3 of Rockwell surface hardness HR30T 57 ± 3 is in the range of 0.02 to 0.04 carbon content, T4 of HR30T 61 ± 3 is in the range of 0.03 to 0.06, HR30T 65 ± 3 T5 is in the range of 0.06 to 0.1, but the carbon content of 0.07 to 0.8% and Mn can be added to obtain the strength of the crude T5. When the carbon content is more than 0.08%, the cold reduction rate can be minimized. Was very low, so the upper limit was limited to 0.08%.

Mn is added with C as a means of securing strength. It is not necessary to add Mn separately in the preparation of T3 to T4, but when the Mn content is low, there is a problem of high temperature brittleness due to S, and it is preferable to set the Mn / S ratio to 17 or more. In the roughness T5, the target hardness is obtained by adding Mn in addition to carbon. When the carbon content is 0.07% or more, the Mn content of about 0.6 HR30T 62 or more is obtained, so the upper limit thereof is limited to 0.6% in the present invention.

Al should be added at least 0.02% because it removes oxygen from steel and precipitates AlN of solid solution. If the Al content is more than 0.02%, oxygen in the molten steel is removed to Al ₂ O ₃ , and AlN is precipitated during hot rolling to reduce the solid solution nitrogen. However, if too much is added, there is a problem of increasing the amount of plastic organic precipitation during hot rolling with the coarsening of AlN to form irregular crystal grains.

Nitrogen helps to secure the strength of the steel, but because of the aging phenomenon, it causes a strainer strain defect during processing, it is preferable to limit as much as possible within the surface treated master plate to be processed as in the present invention to within 0.004% It was.

Oxygen degrades the workability of the steel and forms inclusions in combination with Al, Mn, etc. in the steel. The finely present inclusions act as the biggest factor to tear the french portion during the processing of the french fries in the drawing and ironing cans, so the oxygen limit is limited to within 0.0015%. The method of reducing the oxygen of the steel is not so difficult in low carbon steel as in the present invention, and it is sufficiently removed by adding Al so as to be at least 0.02%, but if necessary, the oxygen in the steel can be easily removed by RH degassing.

Slabs are produced by continuous casting of steel containing other unavoidable elements, followed by hot rolling in the usual manner, and the hot rolling temperature is appropriately controlled in relation to the strength of the steel. The high temperature oxide film formed on the hot rolled coil is completely removed by ordinary pickling conditions, and in cold rolling, the cold reduction rate varies depending on the carbon content of the steel, the hot rolled coil temperature, and the annealing temperature to be applied after rolling. It is the key.

In the present invention, the effects of a wide range of carbon content, hot rolling conditions, cold rolling rate, and continuous annealing temperature on the annual anisotropy of the surface treated discs were investigated. In other words, the optimum cold reduction rate for minimizing ear formation was lower with higher carbon content and higher with higher hot rolling and annealing temperature. Since the plastic anisotropy value (r) of the 45 ° component increases as the carbon content increases at the uniform cold rolling rate, the solid-state carbon increases the {110} and {200} components in the aggregate structure of the material. And especially {200} develops to increase the plastic strain ratio of 45 °.

In general, if the cold reduction rate is increased at the same carbon content, the amount of {200} texture is rapidly increased above the specified reduction rate, thereby significantly increasing the occurrence of 45 ° in the rolling direction. Increasing the hot rolled temperature increases the carbide coarsening, thereby reducing the carbon content re-used at the beginning of continuous annealing recrystallization, thereby reducing the {200} component and increasing the {222} component to minimize ear The cooling rate decreases slightly. As the temperature of the continuous annealing temperature increases, the degree of ear formation at 0 ° and 90 ° increases as the strength of {222} and {110} increases, thus acting as a factor to increase the cold reduction rate.

In the present invention, the above phenomenon is systematically investigated and the following equation is empirically derived through the results. In other words, the minimum cold reduction rate is 56.8 ± CE to set the Δr value to 0.15 or less. Herein, CE is a manufacturing condition coefficient, CE = 4 × continuous annealing temperature (° C.) / 100 + 0.48 × hot rolling winding temperature (° C.) / 100-33.7 × carbon content (%). The repayment of the cooling reduction rate for setting the Δr value to -0.15 or more is 58.9 ± CE. By applying the cold reduction rate as described above, when producing an original drawing having a drawing rate of 2 or less, a can can be produced with almost no earring having an ear formation rate of 5% or less.

Here, the ear formation rate is expressed as ΔH / Hmin, where ΔH is the height difference between the highest and lowest portions of the cup, and Hmin is the height of the lowest portion of the cup. When the cold rolling is completed, the rolled oil is removed by degreasing and continuous annealing, and the continuous annealing temperature may be annealed for 30 seconds or more at a temperature above the recrystallization temperature and below 700 ° C. so as to obtain a target quality. The upper limit of the annealing temperature is 700 ° C. because the amount of solid solution carbon exceeding 700 ° C. increases rapidly, and as mentioned above, there is a problem that can cause emptying of the can and deterioration of hardness due to the generation of stretcher strain.

Flexibly applying the cold reduction rate according to the component and material manufacturing process as in the present invention has the advantage of manufacturing the surface treatment for drawing and ironing cans corresponding to all thickness and high strength levels. For example, if the thickness of material T5 needs 0.2mm thickness, first, the carbon content should be 0.08% and the hot-rolling temperature should be 630 ℃ to produce the quality T5. The thickness of the hot rolled coil may be 1.43. As such, the present invention not only facilitates the design for minimizing the occurrence of ear, but also makes it easy to use because it can be sufficiently compensated by changing the annealing temperature at the time when there is a problem in the manufacturing process and there is a change in the hot rolling temperature and the carbon content. It has the advantage that it can be applied to all high-strength surface treatment discs for processing.

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

Example

Inventive steels (1 to 5) and comparative steels (6 to 10) having chemical components as shown in Table 1 are melted in vacuum and then cast into ingots, or melted in converters and continuously cast, then 1,200 to 1,230. It reheated at the temperature of ° C, the hot finish rolling temperature was 865 ° C or more, and the hot rolled winding temperature was 650 to 700 ° C. The thickness of the hot rolled coil or coil was from 1.45 mm to 2.47 mm, and the hot oxide film was removed by pickling, and then rolled at a cold reduction rate of 83 to 90% to obtain a thickness of 0.245 to 0.25 mm. After degreasing, continuous annealing and rough rolling of about 0.4% were performed to prepare a surface treated disc.

division Chemical composition (% by weight) Manufacturing method C Mn P S Al N O Ti Invention steel One 0.024 0.20 0.012 0.011 0.035 0.0031 0.0012 - Vacuum melting 2 0.028 0.18 0.011 0.009 0.042 0.0032 0.0010 - Melting 3 0.054 0.25 0.009 0.008 0.023 0.0018 0.0012 - Vacuum melting 4 0.06 0.42 0.009 0.012 0.027 0.0023 0.0009 - 5 0.07 0.056 0.012 0.010 0.032 0.0021 0.0010 - Comparative steel 6 0.032 0.25 0.012 0.012 0.043 0.0027 0.0017 - Melting 7 0.003 0.13 0.009 0.011 0.032 0.0021 0.0013 0.025

The steels of Table 1 were subjected to the same manufacturing conditions as in Table 2 below, and the hardness and in-plane anisotropy values were evaluated. Was prepared to evaluate the rate of incidence of crack cracking, and the value is obtained by obtaining more than 2 million cans. The actual earing amount was determined by drawing a 96 mm diameter disc with a 50 mm punch (draw rate 1.92) and measuring the minimum and maximum height of the cup.

division River Manufacture conditions Hardness (RH30T) △ r Incidence rate (%) French crack incidence (ppm) Hot rolled winding temperature (℃) Cold Rolling Rate (%) Annealing Temperature (℃) Invention One One 700 87.0 680 55.2 0.11 3.1 - 2 2 700 87.5 670 56.1 -0.06 2.2 11.7 3 3 700 87.0 670 58.7 -0.12 4.0 - 4 4 670 85.0 650 59.8 0.007 1.1 - 5 5 630 84.0 650 62.8 0.07 1.7 - Comparative method 6 One 600 90.0 700 56.1 -0.29 5.8 - 7 3 700 83.0 650 57.3 0.35 7.7 - 8 4 700 87.0 650 58.9 -0.27 5.4 - 9 5 700 88.0 680 61.2 -0.24 5.8 - 10 6 680 87.5 670 56.7 -0.08 3.4 21.5 11 7 680 89.0 700 51.2 -0.04 0.6 9.3

Inventive methods 1 to 5 all have a value of less than 5%, while Comparative methods 6 to 9 have an increase of 5%, so that defects may occur easily during ironing. In particular, Comparative Method 8 is the same condition as the conventional known technology (Korean Patent Application No. 98-43831), but showed a problem that the earing rate exceeds 5%. That is, the method of the present invention has the advantage that it can significantly reduce the incidence rate than the prior art. Comparative method 10 exceeded 20 ppm of the crack incidence rate due to the high content of oxygen in the steel. Comparative method 11 had the best workability, the lowest ear formation, and the lowest incidence of fracturing cracks. In this case, when the thickness of the surface-treated disc is 0.245 to 0.25 mm, there is a problem that the pressure resistance of the can is insufficient.

As described above, by applying the cold reduction rate flexibly according to the component and material manufacturing process according to the method of the present invention, there is an advantage that a surface treatment disc for drawing and ironing cans corresponding to all thickness and steel grade levels can be manufactured. Not only is it easy to design for minimization, but it is easy to use and wide range of carbon content because it can be compensated sufficiently by changing the annealing temperature in the case of a change in hot rolling temperature and carbon content due to problems during the manufacturing process. It can be applied to a high strength surface treatment disc for processing of a relatively wide range of roughness of T3 to T5, and in particular, there is an effect of significantly reducing the amount of ear generation compared to the prior art.

Claims (1)

Low carbon aluminum-kilted steel containing 0.02% to 0.08% carbon by weight, 0.6% or less Mn, 0.02% to 0.06% Al, 0.004% or less N, and 0.0015% or less oxygen by hot rolling by ordinary annual rolling After rolling and pickling in the usual way, the cold rolling reduction is 56.8 + CE (%) or less (CE is the manufacturing condition coefficient as 4 × continuous annealing temperature (℃) / 100 + 0.48 × hot rolled winding temperature (℃) / 100-33.7 × A method for producing a highly sensitive surface treatment original for processing having low ductility, characterized in that the sheet is cold-rolled to a carbon content (%) and then continuously annealed for 30 seconds or more at a temperature above the recrystallization temperature and below 700 ° C.