555601 A7 B7 五、發明説明（） 發明領域： (讀先閱讀背之溴意事項真蟥寫本貢〉 一種鎔鑄金屬連續鑄造之鑄塊模，特別是用以形成 長方形或方形切面之鋼條。 發明背景： 鑄錠或鑄塊可由鎔鑄金屬，特別是鋼，藉由在一管 狀的模具（鑄錠模）中的鎔鑄金屬連續鑄造，其後緊接著滾 壓（所謂的「鑄造及直接滾壓」技術）來形成。雖然此技術 可獲得相當高的產出速度及品質良好的產品，但其卻具 有數項的缺點·主要是與鎔鑄金屬在模具中被冷卻及固化 的處理有關-這些缺點限制了可獲得之最大產出速度及可 用相同的模具產出之產品範圍。 經濟部智慧財產局員工消費合作社印製 亦即，在一連續鑄塊模（即鎔鑄材料在其中冷卻及固 化之模具）中之過快的鑄造會造成最終產品中之瑕疵的產 生。詳言之，鎔鑄材料將熱傳給該鑄模壁所產生之冷卻 只有在該材料保持與鑄模壁接觸使得一固態金屬的表層 (所謂的「表皮」）被形成並在該材料移動通過該鑄模時逐 漸增厚的情況下才會完全有效。然而，當其固化時，該 材料會收縮且與該鑄模壁，特別是内邊緣，分離使得氣 袋會在該金屬表皮與該鑄模壁之間形成，因而降低散熱 量並減緩固化的過程。該金屬表皮（固態層）持續的成長， 除了在角落處之外，因而獲得部分固化的鎔鑄金屬且在 完成的產品中有遐戚的形成。 這亦提高了在邊緣處導因於該金屬表皮在其從鑄模 第4頁 本紙張尺度適用中國國家標準(CNS)A4規格(210X297公釐) 555601 A7 _____ B7 五、發明說明（） 中取出時在金屬表皮上之應力而產生的裂痕的可能性。 (請先閲讀背面之注意事項再填寫本頁) 簡言之，所得到的鑄條的扭力強度很差，很容易會 有沿著邊緣之縱向裂痕的形成，及具有一非常不平均之 表皮溫度，所有這些會在後續之滾壓階段產生問題並無 矸避免地損及完成產品的品質。 為了要克服這些缺點，一相當低的鑄造速度被保持 用以讓該材料能夠儘可能均勻地冷卻。而且，降低該鋒 模之内部角落的曲率半徑可降低氣袋的形成，但無法提 供太高的鑄造速度。 當只鑄造一種材料時，金屬表皮與鑄模壁的分離可 藉由改善該鑄模的幾何形狀，如使用被適當地傾斜的模 具，而被降低。然而，此解決方法無法被應用至用來製 造不同特性之材料（如不同種類的鋼）的缚模上。 最後，某些習知的鑄模具有一特殊的，如内凹壁， 切面供該鎔鑄金屬通過。然而，雖然降低了分離的問題， 但此種鑄模亦無法在某些限制之下讓鑄造速度提升。 發明目的及概述： 經濟部智慧財產局員工消費合作社印製 本發明的一個目的為用於金屬材料連續鑄造之鑄塊 模，其被設計來克服上述與習知鑄模相關的缺點。詳言 之，本發明的目的是要提供一種能夠在所有的點及沿著 該鑄模的整個長度上有效的冷卻該鎔鑄金屬的鑄塊模’ 用以防止該金屬與該鑄模的壁，及邊緣分離，及用以達 成能夠立即進行滾壓之頂級品質產品的高速鑄造。 第5頁 本紙張尺度適用中國國家標準(CNS)A4規格(210X 297公釐) 555601 A7555601 A7 B7 V. Description of the invention () Field of invention: (Read the first reading of the bromine matters and the true script of this tribute)> An ingot mold for continuous casting of cast metal, especially for forming rectangular or square cut steel bars. Background of the invention: An ingot or ingot can be continuously cast from cast metal, especially steel, by casting metal in a tubular mold (ingot mold), followed by rolling (the so-called "casting and direct "Rolling" technology). Although this technology can obtain a very high output rate and good quality products, it has several disadvantages. It is mainly related to the processing of the cast metal to be cooled and solidified in the mold. -These disadvantages limit the maximum output speed that can be obtained and the range of products that can be produced with the same mold. Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs, ie, in a continuous ingot mold (that is, where the cast material is cooled) And solidified molds) can cause flaws in the final product. In particular, the heat generated by the casting material's heat transfer to the mold wall can only be cooled by the material. The material remains in contact with the mold wall so that a solid metal surface (so-called "skin") is formed and will be fully effective only when the material gradually thickens as it moves through the mold. However, when it solidifies, the material Will shrink and separate from the mold wall, especially the inner edge, so that air pockets will form between the metal skin and the mold wall, thereby reducing heat dissipation and slowing down the solidification process. The metal skin (solid layer) continues to grow In addition to the corners, a partially solidified cast metal is obtained and there is a formation of relatives in the finished product. This also improves the edges at the edges due to the metal skin in the paper from the mold on page 4. The dimensions are applicable to China National Standard (CNS) A4 specifications (210X297 mm) 555601 A7 _____ B7 V. Description of the invention () The possibility of cracks caused by the stress on the metal skin when taking out. (Please read the precautions on the back first (Fill in this page again) In short, the torsion strength of the obtained casting is very poor, it is easy to have longitudinal cracks along the edges, and it has a very uneven table. Skin temperature, all of which will cause problems in the subsequent rolling stage and inevitably damage the quality of the finished product. To overcome these shortcomings, a relatively low casting speed is maintained to make the material as uniform as possible Cooling. Moreover, reducing the radius of curvature of the inner corners of the front mold can reduce the formation of air pockets, but cannot provide too high casting speed. When only one material is cast, the separation of the metal skin from the mold wall can improve the mold. The geometry, such as the use of properly tilted molds, is reduced. However, this solution cannot be applied to the molds used to make materials with different characteristics (such as different types of steel). Finally, some practices The known mold has a special feature, such as a recessed wall, through which the cast metal passes. However, although the problem of separation is reduced, this type of mold cannot increase the casting speed under certain restrictions. Purpose and summary of the invention: Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economics. One object of the present invention is an ingot mold for continuous casting of metallic materials, which is designed to overcome the above-mentioned disadvantages associated with conventional molds. In detail, the object of the present invention is to provide an ingot mold capable of effectively cooling the cast metal at all points and along the entire length of the mold to prevent the metal and the wall of the mold, and Edge separation and high-speed casting for top-quality products that can be rolled immediately. Page 5 This paper is sized for China National Standard (CNS) A4 (210X 297 mm) 555601 A7
五、發明說明（） 根據本發明，一種用於錄鍀金屬~特別是形成矩形或 方形切面的鋼條一的連續鑄造之鑄塊模被提供，其包含一 縱向長形的鑄造導管，該鎔鑄金屬流經該導管並被冷 卻；該鑄造導管具有一大致矩形的截面且是由一第一及 第二對大致平行，邊對邊的側壁所界定；該第一及第 二對側壁大致彼此垂直，並界定四個内邊緣；其特徵在 於該鋒造導管包含至少一第一部分其具有圓角的内邊緣 及一内切面，其從該錄鋒金屬被送入之一縱向第一端朝 向與該第一端相對的一縱向第二端逐漸地改變；在該至 ^ 一第一部分的切面中的該變化是由一相對應之在該等 圓角緣的曲率半徑上之連續，漸進的變化；該曲率半徑 從在該第一端的最大值逐漸減小至在該第二端的最小 值。 詳言之，在該導管的至少一第一部分的切面是要在 該嫁轉金屬通過該至少一第一部分時重現該錄鏵金屬的 熱收縮。 根據本發明之該鑄塊模的特殊設計提供在該錄鏵金 屬的所有表面點，包括在内邊緣上的點，及沿著該轉模 的整個長度上的點的冷卻。事實上，藉由該變化切面部 分之特殊内切面的本質，該材料在任何時間都被保持著 與該鑄模的壁及内邊緣接觸，其事實上重現該材料在其 冷卻及固化時之冷卻模式。 該金屬因而可在不需要保持一相當低的錡造速度之 下而被防止與該鑄模的壁及邊緣分離。根據本發明，冷 第6頁 本紙張尺度適用中國國家標準(CNS)A4規格(210X297公釐) f請先閲讀背面之注意事項再場寫本頁> 訂. 線< 經濟部智慧財產局員工消費合作社印製 555601 A7 _—_____^B7 五、發明説明（） 卻該鑄模的内部是如此的古1 + 有效率，因而可以立即直接滾 麈從該導管出來的產品，而了 + 不而任何中間處理，因為該 材料具有所需要的特性（特 (請先閲讀背面之注意事項再填寫本頁) 】疋’在邊緣的内部應力，及 一均勻的表皮溫度）。甚去 贫’相同的鑄模可被用於不同材 料的鋒造上，如用來製浩 不同種類的鋼鐵，同時能夠確 保高品質的產品並保持高的產出速度。 式簡單說明： 本發明的一非限制性的眘 勺實施例將參照附圖中所示的 範例來加以說明，其中·· 第1圖顯示根據本發明士 m 贫月<一用於鎔鑄金屬的連續鑄造之 一鎊塊模的立髏示意囷； 第2圖為顯示第1圖中之毯 口 丁<鳞模的鎔鑄金屬入口切面的平 面示意圖。 牖號對照說明： 經濟部智慧財產局員工消費合作社印製 1 鑄塊模 2 鑄造導管 3 第一對壁 4 第二對壁 5 邊緣 7 第一縱向 8 第一部分 9 第二部分 10 第二端 11 第二端 12 漏斗狀部分 13 中間段 14 第一部 15 第二部 本紙張尺度適用中國國家標準(CNS)A4規格(210X297公釐) 555601 五 經濟部智慧財產局員工消費合作社印製 發明説明（） 發明詳細說明： 在第i及第2圖中，零件被刻意 成比例地顯TF用 以突顯本發明之主要特徵，其中標號丨 八表用於録鎊金 屬，如鋼冑，之矩形士刀面鋼條形式的連續轉造的鋒塊模。 鑄模！包含一縱向長形的缚造導管2，該鎔铸金屬流 經該導管並被冷卻；該轉造導營2且古 T 八有一大致矩形的截 面且是由-第-對3及一第二對4大致平行，邊對邊之 預設大小的側壁所界定；及該第一及第二對側壁3及4 大致彼此垂直，並界定四個内邊緣5。 在第1圖所示的非限制性範例中，導管2是彎曲的， 其中壁3是平直的及壁4具有一預設的曲率，但很明顯 地可以是非所述（直的形狀。不論何種情形，導管2大 致延伸於一與該對平的壁3平行的預定方向上。 根據本發明，導管2包含該鎔鑄金屬被送入之第一 縱向端7，一具有變化的内切面之第一部分8 ;及一接連 的第二部分9其具有一固定的内切·面並終止於該鎔鑄金 屬被送出之孩導管2的第二端1〇。第一部分8縱向延伸 一預定長度到達一由該導管2的中間段所界定的第二端 11，該中間段是位在該鎔鑄金屬被送出該第一部分8及 該鎔鑄金屬被送入該第二部分9處。 由壁3及4所界定之邊緣5沿著導管2的整個長度 於内部被圓角化；邊緣5的曲率半徑沿著第一部分8逐 漸地變化，從在端7處的最大值Ri持續地減小至在相對 端1 1處的最小值R2，並沿著第二部分9的整個長度被保 第8頁 本紙張尺度適用中國國家標準(CNS)A4規格(210x297公楚) Φ! (請先閱讀背面之注意事項再填寫本頁) 訂· 555601 A7 B7 五、發明説明（） 持R2的固定值；及該邊緣5被選定之曲率半徑最小值R2 對於滾壓從該鑄造導管2送出之金屬而言是最佳值。 (請先閲讀背面之注意事項再填寫本頁} 沿著第一部分8之在邊緣5的曲率半徑上的逐漸變 化在第一部分8的切面上產生一對應的逐漸變化。詳言 之，在切面上的變化是藉由在第一部分8的四個邊緣5 上的每個漏斗狀的部分1 2而被獲得：四個漏斗狀的部分 1 2側向地突伸超越壁3及4，縱向地從第一部分8的端7 延伸至端1 1，並朝向第一部分8的端1 1傾斜變窄，其由 平行壁3及4所界定，因而具有一縱向變化且在面積上 從端7至端1 1逐漸變小。 在端11，第一部分8具有一矩形截面其不帶有突起 並第二部分9之固定切面相銜接。 在第一部分8之切面上的變化可再現在該金屬被送 入時之熱收縮，並沿著第一部分8冷卻。為此目的，在 本發明的一較佳實施例中，在第一部分8之切面上的變 化及在邊緣5的曲率半徑上之對應變化並非是線性的變 化。 經濟部智慧財產局員工消費合作社印製 此外，該變化切面之第一部分8的縱向延伸部最好 是大約等於固定切面的第二部分9之縱向延伸部。根據 一較佳實施例，該第一部分8的縱向延伸部係小於該第 二部分9的縱向延伸部，如約為其9 5 %。 在一典型的實施例中’單純只是作為非限制性的範 例’第一部分8及第二部分9分別具有的長度為 1^=450111111及L2 = 600mm ;該等長度，與於下文中所顯示 第9頁 本紙張尺度適用中國國家標準(CNS)A4規格(210X297公釐）5. Description of the invention () According to the present invention, a continuous casting ingot mold for recording metal ~ especially a steel bar forming a rectangular or square cut surface is provided, which includes a longitudinally elongated casting duct. Cast metal flows through the duct and is cooled; the cast duct has a generally rectangular cross-section and is defined by a first and second pair of substantially parallel, side-to-side sidewalls; the first and second pair of side walls are generally adjacent to each other It is vertical and defines four inner edges; it is characterized in that the frontal-made duct includes at least a first part which has an inner edge with rounded corners and an inward section, which is fed from one of the longitudinal first ends of the recording metal into The first end opposite to a longitudinal second end gradually changes; the change in the tangent to the first part is a continuous, progressive change corresponding to the radius of curvature of the fillet edges ; The radius of curvature gradually decreases from a maximum value at the first end to a minimum value at the second end. In detail, the cut surface in at least a first portion of the catheter is to reproduce the thermal contraction of the recording metal when the grafted metal passes through the at least a first portion. The special design of the ingot mold according to the present invention provides cooling of all surface points of the recording metal, including points on the inner edges, and points along the entire length of the mold. In fact, due to the nature of the special inner cut surface of the changed cut section, the material is kept in contact with the wall and inner edge of the mold at all times, which in fact reproduces the cooling of the material as it cools and solidifies mode. The metal can thus be prevented from separating from the walls and edges of the mold without the need to maintain a relatively low forming speed. According to the present invention, the cold paper page 6 applies the Chinese National Standard (CNS) A4 specification (210X297 mm) f Please read the notes on the back before writing this page > Order. Line < Bureau of Intellectual Property, Ministry of Economic Affairs Printed by the employee consumer cooperative 555601 A7 _______ ^ B7 V. Description of the invention () But the inside of the mold is so ancient 1 + efficient, so the product coming out of the catheter can be rolled out immediately, and + Any intermediate treatment, because the material has the required characteristics (specially (please read the precautions on the back before filling this page)] 疋 'internal stress at the edges, and a uniform skin temperature. In addition, the same casting mold can be used for the cutting of different materials, for example, it can be used to make different types of steel, while ensuring high-quality products and maintaining high output speeds. A brief description of the formula: A non-limiting cautious embodiment of the present invention will be described with reference to the examples shown in the drawings, in which ... FIG. 1 shows according to the present invention m lean months < The standing cross of a pound block mold, which is one of the continuous casting of metal, is schematically illustrated; FIG. 2 is a schematic plan view showing a cut-out metal inlet section of the blanket mold &scale; No. 对照 Note: Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 1 Ingot mold 2 Casting duct 3 First pair of walls 4 Second pair of walls 5 Edge 7 First longitudinal 8 First part 9 Second part 10 Second end 11 Second end 12 Funnel-shaped section 13 Middle section 14 First section 15 Second section This paper size applies the Chinese National Standard (CNS) A4 specification (210X297 mm) 555601 Fifth Ministry of Economic Affairs Intellectual Property Bureau Staff Consumer Cooperatives printed invention description ( ) Detailed description of the invention: In Figures i and 2, the parts are deliberately displayed in proportion to TF to highlight the main features of the present invention, where the number 丨 eight tables are used to record pound metal, such as steel reeds, rectangular swords. Continuously converted front die in the form of a steel bar. Mould! Contains a longitudinally elongated constrained conduit 2 through which the cast metal flows and is cooled; the restructured guide battalion 2 and the ancient T8 have a generally rectangular cross-section and are composed of -first-to-3 and second The pair 4 is substantially parallel and is defined by side walls of a predetermined size from side to side; and the first and second pair of side walls 3 and 4 are substantially perpendicular to each other and define four inner edges 5. In the non-limiting example shown in Fig. 1, the catheter 2 is curved, wherein the wall 3 is straight and the wall 4 has a predetermined curvature, but it can obviously be non-mentioned (straight shape. Whatever In any case, the duct 2 extends approximately in a predetermined direction parallel to the pair of flat walls 3. According to the invention, the duct 2 comprises a first longitudinal end 7 into which the cast metal is fed, with a varying inner cut surface A first part 8; and a successive second part 9 which has a fixed inward surface and terminates at the second end 10 of the child duct 2 from which the cast metal is sent out. The first part 8 extends longitudinally by a predetermined length Reaching a second end 11 defined by the middle section of the duct 2, the middle section is where the cast metal is sent out of the first part 8 and the cast metal is sent into the second part 9. The edge 5 defined by 3 and 4 is rounded internally along the entire length of the duct 2; the radius of curvature of the edge 5 gradually changes along the first part 8, continuously decreasing from the maximum value Ri at the end 7 to The minimum value R2 at the opposite end 1 and is along the entire length of the second part 9 Page 8 This paper size is in accordance with Chinese National Standard (CNS) A4 (210x297 cm) Φ! (Please read the precautions on the back before filling this page) Order · 555601 A7 B7 V. Description of the invention () R2 fixed And the minimum radius of curvature R2 of the selected edge 5 is the best value for rolling the metal sent from the casting duct 2. (Please read the precautions on the back before filling out this page} Along the first part 8 The gradual change in the radius of curvature of the edge 5 produces a corresponding gradual change in the cutting plane of the first part 8. In detail, the change in the cutting plane is by each of the four edges 5 of the first part 8 A funnel-shaped part 12 is obtained: four funnel-shaped parts 12 project laterally beyond the walls 3 and 4 and extend longitudinally from the end 7 of the first part 8 to the end 11 and towards the first part 8 The end 11 is obliquely narrowed, which is defined by the parallel walls 3 and 4, and thus has a longitudinal change and gradually becomes smaller in area from the end 7 to the end 11. At the end 11, the first portion 8 has a rectangular cross section which does not The fixed cuts with protrusions and the second part 9 meet. In the first The change on the 8th plane can reproduce the thermal shrinkage of the metal when it is fed in and cool down along the first part 8. For this purpose, in a preferred embodiment of the invention, on the first plane 8 And the corresponding change on the radius of curvature of edge 5 is not a linear change. Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs In addition, the longitudinal extension of the first section 8 of the change section is preferably approximately equal to the fixed section The longitudinal extension of the second portion 9. According to a preferred embodiment, the longitudinal extension of the first portion 8 is smaller than the longitudinal extension of the second portion 9, such as about 95%. In a typical embodiment In the 'merely as a non-limiting example', the first part 8 and the second part 9 have lengths of 1 ^ = 450111111 and L2 = 600mm respectively; these lengths are applicable to the paper size shown on page 9 below China National Standard (CNS) A4 specification (210X297 mm)
555601 五、發明説明（） 的其它距離十都是沿著一與平的壁3平行的軸(其與 可以疋彎曲之導管2的縱軸相反)被測量的。 因此’在鎔鑄金屬入口端7之邊緣5的曲率半徑為 RfUmm;在離入口端7 —距離L3 = 24〇mm(其是由沿著與 平的壁3平行的軸測量）的第一部分8的中間段13(第i 圖）處其曲率半徑假設一中間值1〇 4mm;及在第一部分8 的响11(即，離端7 — LiysOmm的距離或離中間段13 一 L4 = 210mm的距離）其曲率半徑等於最小值κ〇ιηιη , 其然後沿著孩第二部分9的整個長度被保持於到導管2 的出口端1 0為止。介於曲率半徑上的變化與離第一部分 8的鎔鑄金屬入口端7的距離之間的比例因而並不是常 數，而是隨著離端7的距離而減小：在所示範例中，中 間段13將第一部分8分成長度不同之一第一部14及一第 二部15,該比例在沿著第一部14的長度L3 = 24〇mm處（在 該處曲率半徑從11mm減至10.4mm)約為〇 〇〇25，及該比 例在沿著第二部15的長度L4 = 2 10mm處（在該處曲率半徑 從 10.4mm 減至 l〇mm)約為 〇.〇〇2。 在此舉例的實施例中，在邊緣5的曲率半徑上的變 化，與離該導管2的鎔鑄金屬輸入端7的距離為線性函 數相反的是，其很顯然地當鎔鑄金屬冷卻時，重現鎮鋒 金屬在切面上的變化（其因此為該金屬之熱收縮的函 數）。 壁對3及4的尺吋很顯然地可被選擇用以獲得預定 尺吋之成品。詳言之，為了要形成方形切面的鋒塊，平 第10頁 本紙張尺度適用中國國家標準(CNS)A4規格(210X297公釐) ' ...........Φ.........訂.........線· (請先閲讀背面之注意事項再填寫本頁) 經濟部智慧財產局員工消費合作社印製 555601 A7 B7 五、發明説明（） 的壁3之寬度與彎曲的壁4的寬度之間的比例最好是1 : 1.01。 (請先閲讀背面之注意事項再填寫本頁) 很明顯地，在不偏離本案申請專利範圍所界定的範 圍之下可對上述之鑄塊模作出改變。 經濟部智慧財產局員工消費合作社印製 第11頁 本紙張尺度適用中國國家標準(CNS)A4規格(210X297公釐)555601 V. The other distances of the invention (10) are measured along an axis parallel to the flat wall 3 (which is opposite to the longitudinal axis of the bendable tube 2). Therefore 'the radius of curvature at the edge 5 of the cast metal entrance end 7 is RfUmm; at the distance 7 from the entrance end 7 the distance L3 = 24 mm (which is measured along an axis parallel to the flat wall 3) 8 The radius of curvature at the middle section 13 (picture i) assumes an intermediate value of 104 mm; and the ring 11 at the first section 8 (ie, the distance from the end 7 — LiysOmm or the distance from the middle section 13 to L4 = 210 mm ) Its radius of curvature is equal to the minimum value κιιιη, which is then maintained along the entire length of the second part 9 to the exit end 10 of the duct 2. The ratio between the change in the radius of curvature and the distance from the cast metal entrance end 7 of the first part 8 is therefore not constant, but decreases with distance from the end 7: in the example shown, the middle Segment 13 divides the first part 8 into a first part 14 and a second part 15 with different lengths, and the ratio is at the length L3 = 24 mm along the first part 14 (where the radius of curvature is reduced from 11 mm to 10.4 mm) is about 0.0025, and the ratio is about 0.002 at the length L4 = 2 10 mm along the second portion 15 (where the radius of curvature is reduced from 10.4 mm to 10 mm). In this exemplary embodiment, the change in the radius of curvature of the edge 5 is in contrast to a linear function of the distance from the cast metal input end 7 of the duct 2, which is obviously when the cast metal is cooled, Reproduce changes in the ballast metal on the cut plane (which is therefore a function of the metal's thermal contraction). The sizes of the wall pairs 3 and 4 can obviously be selected to obtain a finished product of a predetermined size. In detail, in order to form a square-shaped frontal block, the paper size on page 10 applies the Chinese National Standard (CNS) A4 specification (210X297 mm) '........... Φ ... ...... Order ...... line · (Please read the precautions on the back before filling out this page) Printed by the Intellectual Property Bureau of the Ministry of Economic Affairs Employee Cooperatives 555601 A7 B7 V. Description of Invention () The ratio between the width of the wall 3 and the width of the curved wall 4 is preferably 1: 1.01. (Please read the notes on the back before filling this page) Obviously, the above ingot mold can be changed without departing from the scope defined by the scope of the patent application in this case. Printed by the Employees' Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs Page 11 This paper size applies to China National Standard (CNS) A4 (210X297 mm)