JP3845994B2 - Open-end manufacturing method with excellent openability, opening safety and rust resistance of scored parts - Google Patents

Description

【００７６】
この発明に従うスコア加工を行うことにより、スコア部の開口性、開口部安全性および耐さび性に優れたオープンエンドを得ることができた。特にスコア加工後、加熱処理を施した場合は、耐さび性が一層向上することが確認された。
【００７７】
参考例１
表２に示す成分組成になる鋼スラブを、表３に示す種々の条件で処理して冷延鋼板とした。ついで、冷延鋼板の一部については、同じく表３に示すSnめっき、Crめっき等の金属系めっき層またはエポキシアミノ系クリア、 PETフィルム等の有機樹脂被覆層、さらには金属系めっきと有機樹脂との複合層を被成した。
上記の各素材鋼板に、実施例１と同様にして、長円形状（長さ40mm、半径10mmφ−20mmφ）のオープンエンドスコア部を形成した。
かくして得られたオープンエンドスコア部を開口したときの開口性、開口部安全性および耐さび性について調査した結果を、表４に示す。
【００７８】
【表２】

【００７９】
【表３】

【００８０】
【表４】

【００８１】
この例は、スコア加工後の加熱軟化処理を省略した参考例であるが、この発明に従う条件下でスコア加工を行うことにより、開蓋性に優れ、かつ破断面に安全上好ましくない大きな「かえり」などが発生しない望ましいスコアが成形されることが明らかである。
この発明条件で成形されたスコアを有する蓋を取り付けた３ピース缶を製造し、水を充填して、加熱することで約２bar の内圧を発生させてその耐圧性を評価したところ、この発明条件で製造したものは従来のスコア成形法によるものと同等の耐圧性能を有していることが確認された。
また、同様に準備した試料缶をコンクリート面の上に1.5mm 高さから落下させて、スコア部の耐衝撃特性を調査したところ、この発明条件で製造されたスコア部は従来の方法で製造されたスコア部のほぼ同等の耐衝撃特性を有していることが明らかとなった。
【００８２】
実施例２
素材としては、
鋼Ａ--- Ｃ：0.0018wt％、Si：0.01wt％、Mn：0.50wt％、Ｐ：0.004 wt％、Al：0.055 wt ％、Ｓ：0.007 wt％、Ｎ：0.0095wt％およびNb：0.005 wt％を含有し、残部は実 質的にFeの組成
鋼Ｂ--- Ｃ：0.0018wt％、Si：0.01wt％、Mn：0.50wt％、Ｐ：0.004 wt％、Al：0.055 wt ％、Ｓ：0.007 wt％、Ｎ：0.0095wt％、Ti：0.008 wt％およびＢ：0.0005wt％を 含有し、残部は実質的にFeの組成
になる鋼スラブを、それぞれ次の条件
・スラブ加熱温度：1250℃
・仕上げ圧延温度：890 ℃
・仕上げ厚み：2.3 mm
・１次冷延圧下率：90％
・焼鈍：連続焼鈍（750 ℃−20ｓ過時効なし）
・２次冷延圧下率：10％（スキンパス）
で製造した冷延鋼板（厚み：0.20mm）およびその表面に目付量：6.5 g/m²のSnめっきを施した硬度：60のブリキ板を用いた。
上記の各素材鋼板を用いて、表５に示す条件で 202径（約54.0mmφ）のＳＯＴ（Stay−on−tab)蓋を作製し、諸特性を調査した。スコア成形法は、従来法のものと、この発明法によるものとで比較した。この時、開口性などに最も大きな影響を及ぼすと考えられるスコア残厚量を等しく設定した。
また、No.1については、その後に 240℃, 0.5minの加熱軟化処理を施した。
かくして得られたオープンエンドスコア部を開口したときの開口性、開口部安全性および耐さび性について調査した結果を、表５に併記する。
【００８３】
【表５】

【００８４】
同表より明らかなように、この発明に従い得られたオープンエンドはいずれも、スコア部開口性、開口部安全性および耐さび性の全てに優れていた。
【００８５】
参考例２
実施例３の鋼Ａと同一の鋼板を素材とし、表面処理として、金属Crを 100 mg/m²、酸化Crを20 mg/m²それぞれめっきした鋼板を製造し、その上に20μm 厚みのＰＥＴフィルムを熱融着させたフィルムラミネート鋼板を製造した。
ついで、表６に示す条件でスコア加工を行い、実施例３と同様にして開口性、開口部安全性および耐さび性について調査した。
得られた結果を表６に併記する。
【００８６】
【表６】

【００８７】
この例は、スコア加工後の加熱軟化処理を省略した参考例であるが、同表より明らかなように、加熱軟化処理前の段階でも、得られたオープンエンドはいずれも、スコア部開口性、開口部安全性および耐さび性の全てに優れていた。
【００８８】
【発明の効果】
かくして、この発明によれば、スコア部の開口性および開口部安全性に優れるだけでなく、耐さび性にも優れたオープンエンドを、簡便かつ安価に得ることができる。
特に、この発明は、アルミ材で多く製造されていた缶蓋材に替わって鉄材を適用する場合に、従来問題とされた、余分な補修塗装を必要とすることなしに、イージーオープン缶蓋を製造することができ、またこのイージーオープン缶蓋は、開口の際、その切り口に従来のような鋭い「かえり」を生じることがないため、その部分で手、指、口先等を切傷するなどの危険が極めて小さい、すなわち極めて高い安全性を有する点で大きな利点を持つ。
【図面の簡単な説明】
【図１】素材鋼板に予備せん断加工を施した状態を示した図である。
【図２】予備せん断加工後、逆方向からの戻しせん断加工を付加する状態を示した図である。
【図３】予備せん断加工ついで戻しせん断加工を施した後の素材鋼板の脆化状態を示した図である。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an open end used as a lid of an easy open can.DeWith respect to the manufacturing method, particularly, the openability of the score portion formed at the open end, that is, the openability and the safety of the open portion, and the rust resistance of the score processing portion are advantageously improved.
[0002]
[Prior art]
A beer can is a so-called easy open can that can open food cans and take out foods and beverages inside the can body without using special tools such as can openers by introducing a cut called a score into the can lid in advance. It is used in various beverage cans and food cans including carbonated beverage juice cans.
The type is roughly classified into a “pull-off type” in which a tab serving as a “lever” is completely cut out at the time of opening and a “steion type” in which the tab is attached to the can even after opening. Moreover, there are a partial easy open end where the opening is partially made with respect to the can diameter, and a full easy open end where the entire opening is opened, and most of the food cans are the latter.
[0003]
The above-described score processing has a great influence on the ease of opening, that is, the openability of the easy open can lid.
Openness is known to be improved by reducing the remaining thickness of the plate after score processing (score remaining thickness) as much as possible, but it is limited in terms of industrial stability and maintaining pressure resistance against internal pressure increases. was there.
In other words, if the openness is prioritized and the remaining thickness of the score is reduced too much, cracks will occur in the score during processing, thermal internal pressure will increase during transportation and storage, and impact stress will increase. The risk of problems such as leakage of contents due to the application increases.
[0004]
As the conventional techniques, those disclosed in Japanese Patent Laid-Open Nos. 54-54786, 57-175034, and 62-235053 are known. All of these are techniques related to the formation of the score portion, and although an improvement effect of the opening property is seen, it is not necessarily sufficient.
On the other hand, there have been several proposals to disperse coarse non-metallic inclusions in the steel to facilitate fracture as a starting point for voids, which in the ideal state certainly improves the openness, but in practice Since the dispersion of these non-metallic inclusions is extremely non-uniform, it causes unexpected unstable fracture, which causes a problem in terms of reliability. In addition, since these materials are inevitably deteriorated in moldability, there is a problem that cracking occurs when the so-called rivet processing necessary for fixing the tab is performed, and molding becomes impossible.
[0005]
In addition, one of the drawbacks of the iron easy open can lid is that rust prevention measures at the score processing part are indispensable. In this kind of can lid, since openability is a top priority issue, it gives a sharp cut (score), but even if a surface-treated steel plate is used, it is inevitable that the exposure of the steel will be avoided. In the state, rust generated during storage becomes a big problem. Therefore, the iron easy open lid needs to be subjected to a repair coating on the processed portion after the score processing, but this is an additional disadvantage and is extremely disadvantageous in terms of cost.
[0006]
In this regard, techniques that eliminate the need for repair coating after forming a score by using extrusion or pressing are disclosed in JP-A-6-115546-115548, JP-A-7-51779, and JP-A-8- Proposed in the 99140 publication.
However, although these techniques can considerably improve the corrosion resistance of the score processed portion by using a material having a resin film, the distortion of the score processed portion is widespread, and it has not been sufficient. Furthermore, in the case of a full open end, there is a problem that the burr of the cut edge exists in a sharp form, so there is a problem that the hand, finger, mouth, etc. are cut, which is sufficient in terms of ensuring the safety of the opening. I could not say.
[0007]
In this way, when opening an easy open can lid and using it for use, there are very many opportunities for hands, fingers, mouths, etc. to touch the fracture surface, and in such cases, the hands, fingers, mouths, etc. will be cut. It is difficult, in other words, ensuring safety after opening cans is also an important requirement.
[0008]
In this regard, with respect to a method for manufacturing an easy open can lid, there are JP-A-60-204452 and JP-A-62-64729 as techniques for improving the safety of the cut surface.
With these technologies, the cross-sectional structure of the notch of the lid (opening the lid along this) is formed into a complex shape as if the plate was folded, and its elastic restoring force was used to sharpen it. By preventing the cut end from being exposed in isolation, an attempt is made to prevent a cut accident such as a user's hand or finger.
However, although the above technique can improve safety, it is difficult to apply when the area of the cut surface is small, and it also has a problem in that it requires many machining steps with a complicated mold. It was.
[0009]
[Problems to be solved by the invention]
  The present invention advantageously solves the above-mentioned problem, and of course has excellent opening performance of the score processing portion, and is excellent in safety after opening the can, and also in the rust resistance of the score processing portion. Excellent easy open can open engineDeAdvantageous manufacturing methodTheIt is what we are going to propose.
[0010]
[Means for Solving the Problems]
The inventors first examined the applicable material, and it was difficult to manufacture the raw material into a uniform material by the conventionally proposed method of simply making the material brittle. It became clear that there was a question about reliability after being assembled as a body.
Therefore, as a material, various forming methods were intensively studied in order to ensure the opening property, the safety of the cut end, and the corrosion resistance while utilizing the excellent ductility of iron. As a result, the following remarkable findings were obtained.
[0011]
1) The energy required for opening is lower when the cut is present on both sides than the conventional score shape where the cut is present only on one side of the plate surface.
2) In the case of the same score remaining thickness, the sharper the cut shape, the lower the energy required for opening.
3) In the processing of the score part, the strength of iron can be reduced more effectively by performing the repetitive processing in which processing is performed from one direction and then processing is performed from the opposite direction, rather than processing from a single direction. .
4) In the case of the above 3), there is little occurrence of a so-called “kaeri” convex portion generated at the final fracture position.
5) In the case of 3) above, although the strength of the opening is reduced, the can lid member has sufficiently high rigidity against the increase of internal pressure and the application of an impact load.
6) In processing with a large amount of strain in a single direction, there is a limit to the ability to follow the deformation of the plating layer and coating layer on the surface, and these layers are easily peeled off to expose the base iron. If it exists, the followability with respect to the deformation | transformation of the ground iron of these layers is favorable, and exposure of a ground iron can be prevented effectively.
[0012]
  The present invention has been developed as a result of intensive studies on the control of the score portion shape and the optimization of the machining history based on the above knowledge.
  That is, the gist of the present invention is as follows..
[0033]
1. In the open end manufacturing method of easy open cans, the materials of the easy open cans are: C: 0.1 wt% or less, Si: 0.30 wt% or less, Mn: 1.00 wt% or less, Al: 0.005 to 0.20 wt%, and N: A surface treatment layer containing 0.020 wt% or less, the balance being Fe and inevitable impurities, and the surface being composed of one or more of a metal plating layer and an organic resin coating layer, or a composite layer of both In forming a score at the open end using a cold-rolled steel sheet, first, from one direction to the score processing assumed portion, pre-shear processing is performed with a pre-shear processing amount of 10 to 50% of the plate thickness, Reverse shearing is performed in the opposite direction under the condition that the pre-shearing and backshearing process results in 30 to 90% of the plate thickness.In addition, after or after the processing of the score part, 150 ~ 250 Heat to ℃An open-end manufacturing method that is excellent in openability, safety of the opening, and rust resistance of the score processing portion, characterized by the above.
2. the above1In addition, the cold-rolled steel sheet has a composition containing one or more selected from Nb: 0.003 to 0.02 wt%, Ti: 0.003 to 0.02 wt%, and B: 0.0005 to 0.004 wt%. An open-end manufacturing method that is excellent in openability, safety of the opening, and rust resistance of the score processing portion, characterized by the above.
[0035]
3. the above1 or 2In the case where the surface treatment layer includes an organic resin coating layer, the heating temperature is set to be equal to or higher than the glass transition point of the organic resin, and the lid opening property, the opening safety, and the rust resistance of the score processed portion Excellent open-end manufacturing method.
[0036]
4. the above1 or 2In this case, when the surface treatment layer is an Sn plating layer, the heating temperature is set to be equal to or higher than the melting point of Sn. End manufacturing method.
[0037]
5. the above1 or 2In the case where the surface treatment layer is a Sn plating layer, or the above4The method for producing an open end having excellent openability, safety of the opening, and rust resistance of the score processed portion, wherein a Ni diffusion layer is formed in advance on the surface of the ground iron.
[0038]
6. the above1-4In any of the above, the cold-rolled steel sheet, which is a raw material, is characterized by omitting the annealing after cold rolling, and has an open end with excellent lid opening and opening safety and rust resistance of the score processed part. Production method.
[0039]
7. the above1-6In any of the above, in the annealing process of the cold-rolled steel sheet, which is the raw material, the open end is excellent in lid opening and opening safety and rust resistance in the score processed part, characterized by decarburizing 5 ppm or more Manufacturing method.
[0040]
DETAILED DESCRIPTION OF THE INVENTION
The score forming method, which is a feature of the present invention, will be described below.
1) Preliminary processing is added to the assumed score processing portion (see FIG. 1).
As shown in FIG. 1, a preliminary shearing process is applied from one direction to the score processing assumed part. By this processing, the surface layer portion is in a state where shear fracture has occurred, and the center portion is in a state subjected to shearing processing.
2) Next, a return shearing process is applied to the preliminary shearing part from the reverse direction (see FIG. 2).
By this return shearing process, the surface of the material returns to a substantially flat state.
3) Finally, 30 to 90% of the total plate thickness is sheared and broken (see FIG. 3).
By adding the processing history of 1) and 2) described above to the score processing assumption part, when viewed in the thickness direction, the front side and the back side are sharp in shape (and have small openings, ie closed) cracked parts ( In the center portion, there is a portion subjected to a strong repeated shear strain occupying 10 to 70% of the plate thickness.
[0041]
When the score portion formed as described above is opened, the crack progresses due to a large stress concentration due to sharp notches existing on the front and back surfaces. Although the portion where the crack progresses does not break, it has already been subjected to a large repeated shear strain, so the ductility of the material itself is reduced, so the crack easily develops.
In addition, the final shear fracture position (the position at which burr is generated) corresponds to the inner part of the sheet thickness direction at least with respect to the original sheet material, and further, the ductility of the material tends to decrease, so a large burr is generated. Therefore, there is no fear of hand or finger cuts or the like in actual use due to the generation form.
[0042]
Further, the rust resistance of the opening is described as follows.
That is, when a plating layer of tin or the like is present in advance, a part is peeled off by the pre-shearing process, but the amount thereof is small and most of it is present in a state of covering the surface following the steel plate. In such a state, performing the shearing in the opposite direction as in the present invention is a direction for recovering the coating of the plating, and an effect of gathering the coating material in the sheared portion can be expected. Therefore, the exposure of the underlying iron is very slight at the end of molding.
Further, if heat treatment is performed thereafter, the fracture portion of the plating layer is repaired by the reflow effect, so that the rust resistance effect is completely recovered.
[0043]
  The present invention will be specifically described below.
  First, the scope of application of the present invention will be described., SuTealIn a canCan be applied.
  In addition, the applicable material has sufficient formability.Cold rolled steel sheetAny of these can be used advantageously,canSteel plates are particularly suitable.
[0044]
  hereThe preferred composition of the steel plate for cans is as follows.
  That is,
    C: 0.1 wt% or less,
    Si: 0.30 wt% or less,
    Mn: 1.00 wt% or less,
    Al: 0.005 to 0.20 wt%,
    N: 0.020 wt% or less
Containing as needed
    Nb: 0.003 to 0.02 wt%,
    Ti: 0.003 to 0.02 wt%,
    B: 0.0005 to 0.004 wt%
1 type or 2 types or more selected from among them, and the balance is substantially Fe composition.
[0045]
  In addition, the reason which limited the component composition to said range in the above-mentioned suitable raw material steel plate is as follows.
C: 0.1 wt% or less
  If the amount of C exceeds 0.1 wt%, the fraction of carbides present in the steel plate will increase rapidly, and the ductility of the steel plate will deteriorate significantly, so the amount of C should be 0.1 wt% or less.There is a need. Furthermore, from the viewpoint of workability, it is desirable to make it 0.02 wt% or less.
  Although the lower limit is not particularly set, when the C amount is less than 0.0005 wt%, the coarsening of crystal grains becomes remarkable, and the risk of occurrence of rough skin defects similar to the so-called orange peel phenomenon increases. Is preferably 0.0005 wt% or more.
  Furthermore, when high material stability and excellent ductility are required, the range of 0.0015 to 0.015 wt% is desirable.
[0046]
Si: 0.30wt% or less
If Si is contained excessively, the surface treatment property deteriorates, and as a result, problems such as deterioration of corrosion resistance occur, so the upper limit was made 0.30 wt%. When particularly excellent corrosion resistance is required, 0.02 wt% or less is suitable.
[0047]
Mn: 1.00wt% or less
Mn is an element effective for preventing hot cracking due to S, and needs to be added according to the content of S. Further, since Mn has the effect of refining crystal grains, such addition is desirable in terms of material.
On the other hand, when Mn is added in a large amount, not only the corrosion resistance is deteriorated, but also the steel plate is hardened and cold rolling is deteriorated, and finally the opening property as a lid material is deteriorated. %. In applications where better corrosion resistance and moldability are required, it is preferably 0.60 wt% or less, and more preferably 0.20 wt% or less.
[0048]
Al: 0.005 to 0.20 wt%
Al needs to be contained in an amount of at least 0.005 wt% as a deoxidizer, but an increase in the content leads to deterioration of surface properties and a marked decrease in solid solution N, so the upper limit was made 0.20 wt%. From the viewpoint of material stability, 0.008 to 0.060 wt% is desirable.
[0049]
N: 0.020 wt% or less
If the N content exceeds 0.020 wt%, not only the occurrence rate of surface defects on the steel sheet increases, but also the occurrence of slab cracking during continuous casting becomes significant, so the upper limit was made 0.020 wt%. By strengthening the steel by adding N, the pressure resistance and impact strength of the can lid can be improved, and the thickness of the steel sheet can be reduced while maintaining them at a sufficient level. Further, even when such a solid solution strengthening of N is utilized, the lid material of the present invention has a feature that there is almost no deterioration of the lid opening property. The lower limit is not particularly specified, but when the strength as a cover material is required, the above-mentioned desirable effect is exhibited by adding approximately 30 ppm or more of N.
From the viewpoint of improving the stability and yield of the material considering the entire manufacturing process, a range of 0.015 wt% or less is more preferable. In particular, in applications where strength as a lid is not required, application of low nitrogen steel of about 20 ppm is desirable.
[0050]
With the steel composition described above, a steel material that sufficiently satisfies the required characteristics can be obtained, but it is advantageous to selectively add Nb, Ti, and B as elements that improve these characteristics.
Nb: 0.003 to 0.02 wt%
By adding Nb, the microstructure of the steel sheet can be refined. The refinement of the steel sheet structure significantly improves the reliability with respect to the impact load applied after the EOE processing until the time of use. Such an effect is generally obtained from the addition of 0.003 wt% or more. However, even if added over 0.02 wt%, these effects are saturated and the recrystallization temperature rises remarkably, making it difficult to perform the annealing process in the production of the steel sheet. Therefore, the Nb addition amount is preferably about 0.003 to 0.02 wt%.
[0051]
Ti: 0.003 to 0.02wt%
By adding Ti, the microstructure of the steel sheet can be made finer as with Nb. Further, by adding Ti, the shape control of inclusions is achieved, and the reliability against shock load is significantly improved after EOE processing and before use. Such an effect is generally obtained from the addition of 0.003 wt% or more. However, even if added over 0.02 wt%, these effects are not only saturated, but the recrystallization temperature rises remarkably, making it difficult to perform an annealing process in the production of the steel sheet. Therefore, the Ti addition amount is preferably about 0.003 to 0.02 wt%.
[0052]
B: 0.0005 to 0.004 wt%
By adding B, the formability of the steel sheet, particularly the local ductility can be improved. Such an effect is exhibited when 0.0005 wt% or more is added. However, when added over 0.0040 wt%, in addition to saturation of such effects, the yield stress increases conversely, and the workability deteriorates. Therefore, the amount of B added is preferably about 0.0005 to 0.004 wt%.
It should be noted that the above effects of Nb, Ti, and B are not offset individually, and even when two or more kinds of Nb, Ti, and B are added in combination, the respective effects are not offset.
[0053]
Cold rolled steel sheet obtained by subjecting a steel slab adjusted to the above-mentioned preferred component composition to hot rolling, pickling, cold rolling, annealing, then light skin pass or secondary cold rolling of about 5 to 30% However, a surface-treated steel sheet in which the surface of the cold-rolled steel sheet is coated with an organic resin such as electrotin plating or chromate treatment or an organic resin coating such as a PET film or paint is more advantageous.
[0054]
Next, suitable manufacturing conditions for the steel material will be described.
The slab is desirably produced by a continuous casting method in order to prevent macro segregation of components. The continuously cast slab may be once cooled to room temperature as it is or may be directly charged into the heating furnace at a high temperature without cooling.
[0055]
The finish rolling temperature is not particularly restricted, but by setting it to 850 ° C or higher as usual, a uniform and fine hot-rolled base metal structure can be obtained, thereby making the structure of the final product uniform and fine. Can be planned. However, when the finishing rolling temperature exceeds 950 ° C., the occurrence of wrinkles due to the scale becomes remarkable, which is not preferable in the field of steel sheets for cans that require a strong surface integrity. The range of 880 to 920 ° C. is more desirable in terms of material uniformity.
Although there is no particular restriction on the hot rolling coiling temperature, an intermediate temperature of about 550 to 750 ° C is recommended as is usually done with a base plate of an ultrathin steel plate for cans. .
[0056]
Annealing conditions; above recrystallization temperature and below 800 ° C
In order to improve the ductility of the material, annealing at a recrystallization temperature or higher is essential. However, when annealing exceeding 800 ° C is performed, significant grain growth occurs, increasing the risk of surface roughness after forming. Accordingly, the annealing temperature is preferably not less than the recrystallization temperature and not more than 800 ° C. For steel sheets for cans that are extremely thin with a thickness of 0.35 mm or less, annealing at a lower temperature and shorter time (approximately 20 seconds) is advantageous from the viewpoint of improving productivity.
[0057]
Cold rolling reduction after annealing; light skin pass or 5% to 40%
Secondary cold rolling after annealing is performed for the purpose of adjusting the surface state of the steel sheet and adjusting the strength level according to the application. If a light skin pass of about 1% or more is not performed after annealing, the detailed mechanism is unknown, but the surface may be deformed unevenly, or the beauty of the surface after processing as a product will be significantly reduced. On the other hand, when the rolling reduction exceeds 40%, the ductility is remarkably deteriorated and the risk of causing breakage during molding increases.
[0058]
Continuous rolling (endless rolling) with sheet bar joining on the entry side of the finishing mill
By performing endless rolling, hot rolling at the front and rear ends of the steel strip is performed under more steady conditions, so that the uniformity of the material in the longitudinal direction in particular can be stably improved. Further, according to this method, the leading and trailing end plates are stably carried out, so that the shape and dimensions of the hot-rolled mother plate serving as the final product mother plate can be ensured with extremely high accuracy.
[0059]
Lubrication rolling with a friction coefficient of 0.2 or less during hot rolling
By carrying out lubrication rolling during hot rolling, the detailed mechanism is unknown, but in particular, it is possible to reduce fluctuations in the final material of the front end portion and the rear end portion of the hot rolling coil. Probably, it is presumed that various metallurgy phenomena during transformation / precipitation proceed more uniformly by making the strain distribution in the thickness direction more uniform during hot rolling. As a result of investigating material changes by variously changing the lubrication conditions during hot rolling, no matter what lubricant is used, the friction coefficient during rolling is 0.2 or less, more desirably 0.15 or less. A uniform material uniformity effect was obtained.
[0060]
surface treatment
The cold-rolled steel sheet produced as described above is usually subjected to a surface treatment for improving rust resistance. Any surface treatment can be used as long as it is applied to normal steel plates for cans. For example, as metal plating, tin plating, chromium plating, nickel plating, nickel / chromium plating, and further chromate treatment. and so on. Examples of the organic resin coating include an organic resin film such as PET and a paint.
Note that the metal plating and the organic resin coating may each be a single layer or a plurality of layers, and there is no problem as a composite layer of the metal plating and the organic resin coating.
[0061]
As mentioned above, although the typical manufacturing method of a raw material cold-rolled steel plate was demonstrated, omitting an annealing process among the above-mentioned processes, using what was work-hardened as a raw material metal plate improves the intensity as a lid material. This is advantageous in that the same lid material strength can be secured with a thinner thickness.
This is because the cost of the metal material used per can can be reduced by using a thinner material with higher strength.
[0062]
This method of omitting annealing is particularly effective when a high-purity, ultra-low carbon steel with a C content of 0.0015 wt% or less is used as the material. Since there is no element surface concentration (during annealing), there are advantages such as improved corrosion resistance.
Even if the annealing is omitted in this manner, there is no disadvantage to the lid opening property and the opening portion safety.
[0063]
In addition, in the annealing step described above or separately, the decarburization treatment is performed to form a decarburized layer on the steel sheet surface, and when the cover material is configured, the openability can be further improved, and at the time of forming This is advantageous in that the wear of the mold (tool) can be reduced and the mold life can be extended.
However, this effect cannot be fully exerted unless the decarburization amount is less than 5 ppm. Therefore, when performing such decarburization treatment, the decarburization amount must be 5 ppm or more.
In addition, as a decarburization process means, adjustment of the hydrogen gas concentration, a dew point, etc. in a continuous annealing furnace is advantageous.
[0064]
  A score part is formed in the material manufactured as described above as follows.
  That is, as shown in FIG. 1, the preliminary shearing process is performed from one direction on the score processing assumed part. As a result of this processing, a portion where shear fracture has occurred in the surface layer portion and a portion subjected to shear processing in the central portion are generated.
  In order to improve the openability, it is desirable to perform a larger shearing process at this stage, but if the processing amount exceeds 50% of the plate thickness, a satisfactory score part strength cannot be secured after the return shearing process described later. . On the other hand, by performing pre-shear processing of approximately 10% or more with respect to the total plate thickness, a score part with excellent opening properties can be finally formed, so the pre-shear processing amount is 10 to 50%WhenDoThere is a need.
  At this time, the setting of the clearance affects the shape of the finally remaining crack (notch) portion. Although it is advantageous to set a small clearance, since it is possible to form a sharper notch portion finally, setting an excessively small clearance is disadvantageous in terms of mold wear and the like. Approximately + 10% to -10% of board thickness is recommended.
[0065]
Next, a return shearing process is applied to the preliminary shearing part from the reverse direction.
This step is most preferably performed in the opposite manner to the above-described pre-shearing process. However, as shown in FIG. The same effect can be obtained. In this case, it is important to apply reverse shear, and it is not always essential to return to a completely flat state.
Further, the shear fracture amount introduced to the lower surface side of FIG. 2 by the return shearing process tends to be smaller than the preliminary shearing process amount due to plastic deformation. For this reason, even if a pre-shearing process of about 50% is applied and a reversion process of the same degree is applied, the shear fracture portion does not necessarily penetrate.
[0066]
  By adding the processing history of 1) and 2) described above to the score processing assumption part, as shown in FIG. 3 above, when viewed in the thickness direction, the front side and the back side have sharply cracked portions, that is, shear fractures. In the central portion, there is a portion subjected to a strong repeated shear strain occupying 10 to 70% of the plate thickness.
  Openness (force required for opening, because there are 30% or more parts that are shearingly destroyedDEnergy) is significantly improved. However, when the portion exceeds 90%, the strength of the single body is remarkably lowered, and the reliability against an increase in can internal pressure, impact stress, and the like is remarkably lowered. Therefore, the shear fracture part is 30-90 of the total thickness.%WhenDoThere is a need.
[0067]
  Since the score portion formed as described above easily cracks at the time of opening, there is no problem in terms of opening.
  In addition, the final shear fracture position (the position where the burr is generated) corresponds to the inner part in the thickness direction at least with respect to the original sheet material, and the ductility of the material tends to decrease, resulting in a large burr. Therefore, the opening safety after opening the can is excellent.
  Furthermore, when a plating layer such as tin is present in advance, a part of it is peeled off by the shearing process, but the amount thereof is slight, and it is repaired somewhat by the reverse shearing process in the reverse direction. It also improves rust.
  In addition, if heat softening treatment is performed during or after score processing, the ductility of the strongly processed portion can be recovered appropriately to prevent unstable destruction, and the reliability of the container during storage is improved. be able to.
  Such softening treatment can be used when cold-rolled steel is used as the material.If150 ° C or higher for sufficient softening effectThere is a need. Also, heating above 250 ° C is not preferable in terms of generating temper color..
[0068]
In addition, by the above-mentioned heat softening treatment, the fracture portion of the surface treatment layer is repaired by the reflow effect, and the rust resistance effect is completely recovered, but in order to fully exhibit this effect, the heating temperature is set to the surface treatment layer. When is a Sn plating layer, it is desirable that the melting point (232 ° C.) or higher of Sn, and when the surface treatment layer is an organic resin coating layer, the glass softening point or higher.
[0069]
Furthermore, as the metal plating, particularly when Sn plating is performed, it is advantageous to previously form a Ni diffusion layer on the surface of the ground iron.
This is because if a Ni diffusion layer is formed in advance on the surface of the ground iron, the electrochemical potential difference of the layer structure is reduced, and the corrosion rate is significantly reduced.
The formation of such a Ni diffusion layer is 0.10 g / m at the entry side of the continuous annealing furnace.²This is achieved by applying the following thin plating and annealing under normal conditions.
[0074]
【Example】
Example1
  As materials, C: 0.03 wt%, Si: 0.02 wt%, P: 0.005 wt%, Mn: 0.15 wt%, Al: 0.045 wt%, S: 0.010 wt% and N: 0.0035 wt%, the balance A steel slab that has a substantially Fe composition
・ Slab heating temperature: 1250 ℃
・ Finish rolling temperature: 850 ℃
・ Finish thickness: 2.0 mm
・ Primary cold rolling reduction: 90%
・ Annealing: Continuous annealing (no over-aging at 700 ℃ -20s)
・ Secondary cold rolling reduction ratio: 1.5% (skin pass)
Cold-rolled steel sheet (thickness: 0.20 mm) manufactured on the surface and its surface weight: 2.8 g / m²A 25 # tin plate with Sn plating was used. In addition, about the tinplate, the epoxy ester type coating was given and it used for the test.
  For each material steel plate above,In the manner shown in FIGS. 1 and 2, pre-shear processing is performed on the score processing assumption portion with various processing amounts as shown in Table 1, and then reverse shear processing is performed with various processing amounts as shown in Table 1. Thus, the shear fracture ratio shown in Table 1 is obtained.An open-ended score portion having an oval shape (length 40 mm, radius 10 mmφ-20 mmφ) was formed.
  In addition, a part thereof was subjected to heat softening treatment at 210 ° C. for 20 minutes.
  Table 2 also shows the results of the investigation on the opening property, opening safety and rust resistance when the open end score part thus obtained was opened.
  Note that the openability is determined by measuring a pop value, a tear value, and a detach value (all N = Ten Average). Here, the pop value is the stress required to generate the initial crack by causing the tab, and the tear value is the stress necessary to stably continue shear fracture at the score and the detached value. The tab is detached from the lid body. This is the stress required to perform the process and is a value that depends greatly on the plate thickness and design. 2.0, 3.5, 4.0 kgf It can be said that the opening is generally good if it is about the following.
  AlsoThe rust resistance was evaluated based on the presence or absence of rust on the surface, particularly the score-formed part, after holding the material in an environment where condensation and drying were repeated for about 1 month.
  In addition,Table 1For comparison, according to the conventional method, the result of the investigation when the score part is formed by the press notch from one direction is also shown.
[0075]
[Table 1]

[0076]
By performing the score processing according to the present invention, it was possible to obtain an open end excellent in the opening property of the score portion, the safety of the opening portion, and the rust resistance. In particular, it was confirmed that rust resistance was further improved when heat treatment was performed after score processing.
[0077]
Reference example 1
  Steel slabs having the composition shown in Table 2 were processed under various conditions shown in Table 3 to obtain cold-rolled steel sheets. Next, for some of the cold-rolled steel sheets, metal plating layers such as Sn plating and Cr plating, or epoxyamino clear, organic resin coating layers such as PET film, and metal plating and organic resin shown in Table 3 are also used. A composite layer with was deposited.
  An open-ended score portion having an oval shape (length 40 mm, radius 10 mmφ−20 mmφ) was formed on each material steel plate in the same manner as in Example 1.
  Table 4 shows the results of investigations on the opening property, opening safety, and rust resistance when the open-ended score portion thus obtained was opened.
[0078]
[Table 2]

[0079]
[Table 3]

[0080]
[Table 4]

[0081]
  This example is a reference example in which the heat softening process after score processing is omitted,It is apparent that by performing score processing under the conditions according to the present invention, a desirable score is formed that is excellent in openability and does not generate a large “burl” that is not preferable for safety on the fractured surface.
  A three-piece can fitted with a lid having a score formed under the conditions of the present invention was manufactured, filled with water, and heated to generate an internal pressure of about 2 bar, and the pressure resistance was evaluated. It was confirmed that the product manufactured by the method has pressure resistance equivalent to that obtained by the conventional score forming method.
  Similarly, a sample can prepared in the same manner was dropped from a height of 1.5 mm onto a concrete surface, and the impact resistance characteristics of the score portion were investigated. The score portion manufactured under the conditions of this invention was manufactured by a conventional method. It was clarified that it has almost the same impact resistance characteristics as the score part.
[0082]
Example2
  As a material,
Steel A --- C: 0.0018 wt%, Si: 0.01 wt%, Mn: 0.50 wt%, P: 0.004 wt%, Al: 0.055 wt%, S: 0.007 wt%, N: 0.0095 wt% and Nb: 0.005 Contains wt%, the balance is essentially Fe composition
Steel B --- C: 0.0018 wt%, Si: 0.01 wt%, Mn: 0.50 wt%, P: 0.004 wt%, Al: 0.055 wt%, S: 0.007 wt%, N: 0.0095 wt%, Ti: 0.008 Contains wt% and B: 0.0005wt% with the balance being substantially Fe
Each steel slab will be in the following conditions
・ Slab heating temperature: 1250 ℃
・ Finish rolling temperature: 890 ℃
・ Finish thickness: 2.3 mm
・ Primary cold rolling reduction: 90%
-Annealing: Continuous annealing (750 ° C-20s without overaging)
・ Secondary cold rolling reduction: 10% (skin pass)
Cold-rolled steel sheet (thickness: 0.20mm) manufactured on the surface and its basis weight: 6.5 g / m²A tin plate with a hardness of 60 plated with Sn was used.
  Using each of the above steel plates, 202 diameter (about 54.0 mmφ) SOT (Stay-on-tab) lids were produced under the conditions shown in Table 5, and various characteristics were investigated. The score forming method was compared between the conventional method and the method according to the present invention. At this time, the remaining score amount that is considered to have the greatest influence on the opening property was set equal.
  No. 1 was then heat-softened at 240 ° C for 0.5 min.
  Table 5 shows the results of investigation on the opening property, opening safety and rust resistance when the open end score portion thus obtained was opened.
[0083]
[Table 5]

[0084]
As is clear from the table, all of the open ends obtained in accordance with the present invention were excellent in score part opening property, opening part safety and rust resistance.
[0085]
Reference example 2
  The same steel plate as steel A of Example 3 is used as a raw material, and as a surface treatment, metal Cr is 100 mg / m.², Cr oxide 20 mg / m²Each of the plated steel plates was manufactured, and a film laminated steel plate was prepared by thermally fusing a PET film having a thickness of 20 μm thereon.
  Next, score processing was performed under the conditions shown in Table 6, and the opening property, opening safety and rust resistance were investigated in the same manner as in Example 3.
  The obtained results are also shown in Table 6.
[0086]
[Table 6]

[0087]
  This example is a reference example in which the heat softening process after score processing is omitted,As is clear from the table,Even at the stage before heat softening,All of the obtained open ends were excellent in all of score part opening property, opening part safety and rust resistance.
[0088]
【The invention's effect】
Thus, according to the present invention, it is possible to easily and inexpensively obtain an open end that is not only excellent in the opening property and safety of the score portion but also excellent in rust resistance.
In particular, the present invention provides an easy-open can lid without requiring an extra repair coating, which has been a problem in the past, when an iron material is applied in place of a can lid material that is often manufactured from aluminum. The easy open can lid can be manufactured, and when it is opened, it does not produce a sharp “burl” like the conventional one at the cut end. It has a great advantage in that the danger is very small, ie it has a very high safety.
[Brief description of the drawings]
FIG. 1 is a view showing a state in which a pre-shearing process is performed on a raw steel plate.
FIG. 2 is a view showing a state in which a reverse shearing process is applied in the reverse direction after the preliminary shearing process.
FIG. 3 is a diagram showing an embrittled state of a raw steel plate after pre-shearing and then back shearing.

Claims (7)

In the open end manufacturing method of easy open cans, the materials of the easy open cans are C: 0.1 wt% or less, Si: 0.30 wt% or less, Mn: 1.00 wt% or less, Al: 0.005 to 0.20 wt%, and N: A surface treatment layer containing 0.020 wt% or less, the balance being Fe and inevitable impurities, and the surface being composed of one or more of a metal plating layer and an organic resin coating layer, or a composite layer of both In forming a score at the open end using a cold-rolled steel sheet, first, from one direction to the score processing assumed portion, pre-shear processing is performed with a pre-shear processing amount of 10 to 50% of the plate thickness, the shearing returning from the opposite direction from that, and facilities under conditions in which the pre-shearing and said return to shear fracture portion by shearing is 30 to 90% of the plate thickness, further during processing of the score portion or after processing , Characterized by heating the plate to 0.99 ~ 250 ° C., open the lid of the opening safety and scoring unit manufacturing method of open-ended excellent resistance to rust of. The cold-rolled steel sheet according to claim 1 , further comprising one or more selected from Nb: 0.003 to 0.02 wt%, Ti: 0.003 to 0.02 wt%, and B: 0.0005 to 0.004 wt%. An open-end manufacturing method excellent in openability, safety of the opening, and rust resistance of the score processed portion, characterized by having a composition. In Claim 1 or 2 , when the said surface treatment layer contains an organic resin coating layer, heating temperature shall be more than the glass transition point of organic resin, Opening property, opening safety, and score processing Open-end manufacturing method with excellent rust resistance. According to claim 1 or 2, when the surface treatment layer is a Sn plating layer, the heating temperature, characterized in that equal to or higher than the melting point of Sn, anti rust open lid of the opening safety and scoring unit Open-end manufacturing method with excellent properties. When the surface treatment layer is a Sn plating layer according to claim 1 or 2 , or according to claim 4 , a Ni diffusion layer is formed in advance on the surface of the ground iron. Open-end manufacturing method with excellent safety and rust resistance of the score processing part. In any one of Claims 1-4 , about the cold-rolled steel plate which is a raw material, the annealing after cold rolling is abbreviate | omitted, In the lid opening property and opening part safety | security, and the rust resistance of a score process part Excellent open-end manufacturing method. In any one of Claims 1-6 , in the annealing process of the cold-rolled steel sheet which is a raw material, 5 ppm or more of decarburization is performed, The openability and safety of an opening part, and the rust resistance of a score process part Excellent open-end manufacturing method.

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