TWI615484B

TWI615484B - Hot-dip galvanized steel sheet

Info

Publication number: TWI615484B
Application number: TW105122622A
Authority: TW
Inventors: Takafumi Yokoyama; Kunio Hayashi; Masafumi Azuma; Eisaku Sakurada; Hiroyuki Kawata; Genki Abukawa
Original assignee: Nippon Steel & Sumitomo Metal Corp
Priority date: 2016-07-18
Filing date: 2016-07-18
Publication date: 2018-02-21
Also published as: TW201804005A

Description

熔融鍍鋅鋼板 Hot-dip galvanized steel sheet

技術領域 Technical field

本發明是有關於一種抗氫脆性優異、高降伏比且超高強度之熔融鍍鋅鋼板。具體而言，主要是有關於一種藉由壓製加工等成形為各種形狀的加工性優異且汽車用之抗氫脆性優異、高降伏比且超高強度之熔融鍍鋅鋼板。 The present invention relates to a hot-dip galvanized steel sheet excellent in hydrogen embrittlement resistance, high drop ratio and ultra high strength. Specifically, it is mainly a hot-dip galvanized steel sheet which is excellent in workability by molding into various shapes by press working, and which is excellent in hydrogen embrittlement resistance for automobiles, high in derating ratio, and high in strength.

背景技術 Background technique

近年來，作為地球暖化因應對策而限制溫室效應氣體之排出量，若由此觀點來看，則必須提升汽車之燃料消耗量。故，為了將車體輕量化同時確保碰撞安全性，目前正逐步擴大高強度鋼板之應用。又，在要求防鏽性的部位必須是施行過熔融鍍鋅之超高強度鋼板。 In recent years, as a countermeasure against global warming, the amount of greenhouse gas emissions has been limited. From this point of view, it is necessary to increase the fuel consumption of automobiles. Therefore, in order to reduce the weight of the vehicle body and ensure the safety of collision, the application of high-strength steel sheets is being gradually expanded. Further, in the portion where the rust prevention property is required, it is necessary to use an ultrahigh-strength steel sheet subjected to hot-dip galvanizing.

特別是近來對於拉伸強度1300MPa以上的超高強度鋼板及超高強度熔融鍍鋅鋼板之需求逐漸提高。再者，必須抑制碰撞時變形的構件必須是具有高降伏比之超高強度鋼板。 In particular, the demand for ultra high-strength steel sheets and ultra-high-strength hot-dip galvanized steel sheets having a tensile strength of 1300 MPa or more has been increasing recently. Further, the member which must be suppressed from deformation at the time of collision must be an ultra high strength steel sheet having a high drop ratio.

然而，在應用拉伸強度大於1300MPa的超高強度鋼板時，必須解決鋼板之氫脆化。所謂氫脆化乃以下現象：起因於自環境滲入的氫，使用狀況下有高應力作用的鋼構件乃藉由拉伸最大應力以下之附加應力而破裂。 However, when an ultrahigh-strength steel sheet having a tensile strength of more than 1300 MPa is applied, hydrogen embrittlement of the steel sheet must be solved. The so-called hydrogen embrittlement is the following phenomenon: Due to the infiltration of hydrogen from the environment, the steel member with high stress under the condition of use is broken by the additional stress below the maximum stress.

一般而言，鋼板的拉伸強度越是上升，鋼板的抗氫脆性越是劣化，然而，該機制本身尚未明確。 In general, the more the tensile strength of the steel sheet rises, the more the hydrogen embrittlement resistance of the steel sheet deteriorates. However, the mechanism itself is not yet clear.

迄今亦進行各種欲改善鋼板之氫脆性之嘗試。以下顯示其探討事例。 Various attempts have been made to improve the hydrogen embrittlement of steel sheets. The following is an example of the discussion.

於專利文獻1中揭示有一種關於高強度鋼板之技術，其將鋼板表層進行脫碳處理，並藉由鋼板表層的肥粒鐵體積率之增加而使其軟質化，且將鋼板內部組織作成肥粒鐵主體，再使少量具有細塊的麻田散鐵分散，藉此，兼顧高強度化與抗氫脆性。然而，專利文獻1中揭示的鋼板乃含有相當量屬於軟質組織之肥粒鐵，因此，並不適合用以獲得高降伏比。 Patent Document 1 discloses a technique for high-strength steel sheets in which a surface layer of a steel sheet is subjected to decarburization treatment, and softened by an increase in the volume fraction of ferrite grains on the surface layer of the steel sheet, and the internal structure of the steel sheet is made into a fertilizer. The granulated iron main body is dispersed with a small amount of granulated loose iron, thereby achieving both high strength and hydrogen embrittlement resistance. However, the steel sheet disclosed in Patent Document 1 contains a considerable amount of ferrite iron belonging to a soft structure, and therefore, it is not suitable for obtaining a high drop ratio.

於專利文獻2中揭示有一種關於高強度熔融鍍鋅鋼板之技術，其作成肥粒鐵之形態而適切地控制平均粒徑及縱橫比，並兼顧加工性與抗氫脆性。然而，於專利文獻2中揭示的鋼板中，亦含有一定量屬於軟質組織之肥粒鐵，因此，一般預料並不適合用以獲得高降伏比。 Patent Document 2 discloses a technique for a high-strength hot-dip galvanized steel sheet in which the average particle diameter and the aspect ratio are appropriately controlled in the form of ferrite iron, and both workability and hydrogen embrittlement resistance are considered. However, the steel sheet disclosed in Patent Document 2 also contains a certain amount of ferrite iron which belongs to a soft structure, and therefore, it is generally not expected to be suitable for obtaining a high drop ratio.

於專利文獻3中揭示有一種關於高強度熔融鍍鋅鋼板之技術，其將鋼組織作成麻田散鐵主體組織，更使Nb、V、Cr、Ti及Mo等碳化物析出而作成氫陷阱，藉此，改善抗氫脆性。然而，於專利文獻3中揭示的鋼板中，亦未考慮高降伏比。 Patent Document 3 discloses a technique for high-strength hot-dip galvanized steel sheet in which a steel structure is used as a main structure of a granulated iron, and a carbide such as Nb, V, Cr, Ti, and Mo is precipitated to form a hydrogen trap. Thus, the improvement of hydrogen embrittlement resistance. However, in the steel sheet disclosed in Patent Document 3, the high drop ratio is also not considered.

於專利文獻4中揭示有一種關於高強度熔融鍍鋅鋼板之技術，其將鋼組織作成部變韌鐵主體組織，更將殘留沃斯田鐵限制在小於4%而提升抗氫脆性。 Patent Document 4 discloses a method for high-strength hot-dip galvanizing The technology of the steel plate, which makes the steel structure into a tough iron main body structure, and further restricts the residual Worth iron to less than 4% to enhance the hydrogen embrittlement resistance.

然而，於熔融鍍鋅步驟中生成的部變韌鐵自其保持溫度區起大多屬於上部變韌鐵。相較於回火麻田散鐵及下部變韌鐵，上部變韌鐵乃韌性差之組織，因此，在將上部變韌鐵作成主體組織的鋼板中，會擔心韌性之降低。 However, the toughened iron formed in the hot-dip galvanizing step mostly belongs to the upper toughened iron since it maintains the temperature zone. Compared with the tempered Martian loose iron and the lower toughened iron, the upper toughened iron is a structure with poor toughness. Therefore, in the steel sheet in which the upper toughened iron is used as the main structure, there is a fear of a decrease in toughness.

先行技術文獻 Advanced technical literature 專利文獻 Patent literature

專利文獻1：國際公開第2011/065591號 Patent Document 1: International Publication No. 2011/065591

專利文獻2：日本特開2010-126787號公報 Patent Document 2: Japanese Laid-Open Patent Publication No. 2010-126787

專利文獻3：日本特開2004-323951號公報 Patent Document 3: Japanese Laid-Open Patent Publication No. 2004-323951

專利文獻4：日本特開平06-145893號公報 Patent Document 4: Japanese Laid-Open Patent Publication No. 06-145893

專利文獻5：日本特開2013-144830號公報 Patent Document 5: Japanese Laid-Open Patent Publication No. 2013-144830

專利文獻6：日本特開2009-203549號公報 Patent Document 6: Japanese Laid-Open Patent Publication No. 2009-203549

專利文獻7：國際公開第2013/047821號 Patent Document 7: International Publication No. 2013/047821

專利文獻8：國際公開第2013/047755號 Patent Document 8: International Publication No. 2013/047755

專利文獻9：國際公開第2011/065591號 Patent Document 9: International Publication No. 2011/065591

專利文獻10：日本特開平10-001740號公報 Patent Document 10: Japanese Patent Laid-Open No. Hei 10-001740

專利文獻11：日本特開平09-111398號公報 Patent Document 11: Japanese Patent Laid-Open No. 09-111398

專利文獻12：日本特開平06-145891號公報 Patent Document 12: Japanese Laid-Open Patent Publication No. 06-145891

專利文獻13：國際公開第2011/105385號說明書 Patent Document 13: International Publication No. 2011/105385

專利文獻14：日本特開2007-197819號公報 Patent Document 14: Japanese Laid-Open Patent Publication No. 2007-197819

非專利文獻 Non-patent literature

非專利文獻1：CAMP-ISIJ Vol.17(2004)p.396 Non-Patent Document 1: CAMP-ISIJ Vol. 17 (2004) p.396

非專利文獻2：鐵與鋼，vol.74(1988)，p.2353 Non-Patent Document 2: Iron and Steel, vol. 74 (1988), p. 2353

發明概要 Summary of invention

本發明之目的在於提供一種熔融鍍鋅鋼板，其抗氫脆性優異，且可獲得高拉伸強度及降伏比。 An object of the present invention is to provide a hot-dip galvanized steel sheet which is excellent in hydrogen embrittlement resistance and which can attain high tensile strength and a ratio of reduction.

發明人乃針對製得具下述特性之熔融鍍鋅鋼板之方法進行精心探討，而該熔融鍍鋅鋼板之抗氫脆性優異，且可獲得高拉伸強度，例如1300MPa以上之拉伸強度，以及高降伏比，例如75%以上之降伏比；探討結果，遂而獲得以下見解。 The inventors have intensively studied a method for producing a hot-dip galvanized steel sheet having the following characteristics, and the molten galvanized steel sheet is excellent in hydrogen embrittlement resistance, and can obtain high tensile strength, for example, tensile strength of 1300 MPa or more, and High drop-to-volt ratio, for example, a ratio of more than 75% of the fall-to-volt ratio;

(a)將肥粒鐵及上部變韌鐵之面積率限制在預定面積率以下，並作成麻田散鐵主體之組織。 (a) The area ratio of the ferrite iron and the upper toughened iron is limited to a predetermined area ratio, and the structure of the main body of the Ma Tian loose iron is prepared.

(b)為了抑制氫脆化破裂沿著舊沃斯田鐵晶界進展，使屬於晶界強化元素之B含有一定量以上，同時將麻田散鐵等的平均有效結晶粒徑控制在預定粒徑以下。 (b) In order to suppress hydrogen embrittlement and rupture along the old Worthfield iron grain boundary, B which is a grain boundary strengthening element contains a certain amount or more, and the average effective crystal grain size of the granulated iron or the like is controlled to be less than or equal to the predetermined particle diameter.

(c)將具有預定個數密度以上之Fe碳化物的麻田散鐵佔整體麻田散鐵之面積率作成50%以上。 (c) The area ratio of the granulated iron of the total amount of the Fe carbide having a predetermined number density or more to the entire granulated iron is 50% or more.

發現當滿足(a)、(b)及(c)全體時，將可達成所期望之機械特性與抗氫脆性。 It was found that when all of (a), (b) and (c) are satisfied, the desired mechanical properties and hydrogen embrittlement resistance can be achieved.

本發明乃根據上述見解而完成，其要旨如下。 The present invention has been completed based on the above findings, and the gist thereof is as follows.

(1)一種熔融鍍鋅鋼板，其特徵在於具有以下所示之化學組成：以質量%計，C：0.14~0.3%、Si：0.001~2.0%、 Mn：2.0~4.0%、P：0.05%以下、S：0.01%以下、N：0.01%以下、Al：0.001~1.0%、Ti：0.001~0.10%、B：0.0001~0.01%、Mo：0~0.50%、Cr：0~0.80%、Ni：0~1.00%、Cu：0~1.00%、V：0~0.50%、Nb：0.0~0.10%、Ca：0.00~0.01%、Mg：0.00~0.01%、REM：0.00~0.01%、Bi：0.00~0.01%，及剩餘部分：Fe及雜質；又，具有以下所示之鋼組織：以面積率計，多邊形肥粒鐵：10%以下、上部變韌鐵：20%以下、殘留沃斯田鐵：5%以下、麻田散鐵：70%以上、具有個數密度為1×10⁶/mm²以上之Fe碳化物的麻田散鐵：相對於整體麻田散鐵為50%以上，及平均有效結晶粒徑：5.0μm以下。 (1) A hot-dip galvanized steel sheet characterized by having the chemical composition shown below: C: 0.14 to 0.3%, Si: 0.001 to 2.0%, Mn: 2.0 to 4.0%, P: 0.05% by mass% Hereinafter, S: 0.01% or less, N: 0.01% or less, Al: 0.001 to 1.0%, Ti: 0.001 to 0.10%, B: 0.0001 to 0.01%, Mo: 0 to 0.50%, Cr: 0 to 0.80%, Ni :0~1.00%, Cu: 0~1.00%, V: 0~0.50%, Nb: 0.0~0.10%, Ca: 0.00~0.01%, Mg: 0.00~0.01%, REM: 0.00~0.01%, Bi: 0.00~0.01%, and the remainder: Fe and impurities; in addition, it has the steel structure shown below: in terms of area ratio, polygonal ferrite iron: 10% or less, upper toughened iron: 20% or less, residual Worthfield Iron: 5% or less, 麻田散铁: 70% or more, 麻田散铁 with a number of Fe carbides having a density of 1 × 10 ⁶ /mm ² or more: 50% or more relative to the whole granulated iron, and the average effective Crystal grain size: 5.0 μm or less.

(2)如(1)之熔融鍍鋅鋼板，其中固溶B量為0.0010質量%~0.0100質量%，舊沃斯田鐵粒徑為1.0μm~7.0μm。 (2) The hot-dip galvanized steel sheet according to (1), wherein the amount of solid solution B is 0.0010% by mass to 0.0100% by mass, and the particle size of the old Worthite is 1.0 μm to 7.0 μm.

(3)如(2)之熔融鍍鋅鋼板，其中固溶B量與舊沃斯田鐵粒徑之積為0.0010質量%．μm以上。 (3) The molten galvanized steel sheet according to (2), wherein the product of the amount of solid solution B and the particle size of the old Worthite iron is 0.0010% by mass. More than μm.

(4)如(1)至(3)中任一項之熔融鍍鋅鋼板，其中前述化學組成中，Mo：0.001~0.50%成立。 (4) The hot-dip galvanized steel sheet according to any one of (1) to (3) wherein, in the chemical composition, Mo: 0.001 to 0.50% is established.

(5)如(1)至(4)中任一項之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Cr：0.001~0.80%、Ni：0.001~1.00%，或Cu：0.001~1.00%。 (5) The hot-dip galvanized steel sheet according to any one of (1) to (4), wherein any of the following or any combination of the above chemical compositions is established: Cr: 0.001 to 0.80%, and Ni: 0.001 to 1.00% , or Cu: 0.001~1.00%.

(6)如(1)至(5)中任一項之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等兩者成立：V：0.001~0.50%，或 Nb：0.001~0.10%。 (6) The hot-dip galvanized steel sheet according to any one of (1) to (5) wherein, in the chemical composition, the following or both are established: V: 0.001 to 0.50%, or Nb: 0.001~0.10%.

(7)如(1)至(6)中任一項之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Ca：0.0001~0.01%、Mg：0.0001~0.01%、REM：0.0001~0.01%，或Bi：0.0001~0.01%。 (7) The hot-dip galvanized steel sheet according to any one of (1) to (6) wherein, in the chemical composition, any combination of the following or the above is established: Ca: 0.0001 to 0.01%, Mg: 0.0001 to 0.01% , REM: 0.0001~0.01%, or Bi: 0.0001~0.01%.

若藉由本發明，則抗氫脆性優異，且可獲得高拉伸強度及降伏比。 According to the present invention, the hydrogen embrittlement resistance is excellent, and high tensile strength and a ratio of reduction are obtained.

圖1是以模式方式顯示實施例1中採用的熱處理與鍍覆之步驟圖。 Fig. 1 is a view showing a step of heat treatment and plating employed in the embodiment 1 in a mode.

圖2是以模式方式顯示實施例2中採用的熱處理與鍍覆之步驟圖。 Fig. 2 is a view showing the steps of heat treatment and plating employed in the embodiment 2 in a mode.

用以實施發明之形態 Form for implementing the invention

首先，說明有關本發明實施形態之熔融鍍鋅鋼板及使用於其製造之扁胚之化學組成。詳情如後述，有關本發明實施形態之熔融鍍鋅鋼板乃經由扁胚之熱壓延、冷壓延、連續退火、熔融鍍鋅處理及回火等來製造。故，熔融鍍鋅鋼板及扁胚之化學組成會考慮該等處理而不僅是熔融鍍鋅鋼板之特性。於以下說明中，只要未特別事先聲明，屬於熔融鍍鋅鋼板中所含各元素之含量單位之「%」乃意味著「質量%」。有關本發明實施形態之熔融鍍鋅鋼板乃具有以下所示之化學組成：以質量%計，C：0.14~0.3%、Si：0.001~2.0%、Mn：2.0~4.0%、P：0.05%以下、S：0.01%以下、N：0.01%以下、Al：0.001~1.0%、Ti：0.001~0.10%、B：0.0001~0.01%、Mo：0~0.50%、Cr：0~0.80%、Ni：0~1.00%、Cu：0~1.00%、V：0~0.50%、Nb：0.0~0.10%、Ca：0.00~0.01%、Mg：0.00~0.01%、REM(稀土類金屬：rare earth metal)：0.00~0.01%、Bi：0.00~0.01%，及剩餘部分：Fe及雜質。在此，雜質可例示：礦石或廢料等原材料中所含有者、於製造步驟中所含有者。 First, the chemical composition of the hot-dip galvanized steel sheet according to the embodiment of the present invention and the flat embryo used for the production thereof will be described. As will be described later, the hot-dip galvanized steel sheet according to the embodiment of the present invention is produced by hot rolling, cold rolling, continuous annealing, hot-dip galvanizing treatment, tempering, or the like of a flat embryo. Therefore, the chemical composition of the hot-dip galvanized steel sheet and the flat embryo takes into consideration the characteristics of the hot-dip galvanized steel sheet. In the following description, "%" of the content unit of each element contained in the hot-dip galvanized steel sheet is intended unless otherwise stated in advance. Taste "% by mass". The hot-dip galvanized steel sheet according to the embodiment of the present invention has the chemical composition shown below: C: 0.14 to 0.3%, Si: 0.001 to 2.0%, Mn: 2.0 to 4.0%, P: 0.05% or less, by mass% , S: 0.01% or less, N: 0.01% or less, Al: 0.001 to 1.0%, Ti: 0.001 to 0.10%, B: 0.0001 to 0.01%, Mo: 0 to 0.50%, Cr: 0 to 0.80%, Ni: 0~1.00%, Cu: 0~1.00%, V: 0~0.50%, Nb: 0.0~0.10%, Ca: 0.00~0.01%, Mg: 0.00~0.01%, REM (rare earth metal: rare earth metal) : 0.00~0.01%, Bi: 0.00~0.01%, and the remainder: Fe and impurities. Here, the impurities may be exemplified by those contained in raw materials such as ore or scrap, and included in the production steps.

(C：0.14~0.3%) (C: 0.14~0.3%)

C乃用以獲得所期望之拉伸強度必須之元素。若小於0.14%，則無法獲得所期望之拉伸強度，因此，作成0.14%以上。較為理想的是0.17%以上。另一方面，若大於0.3%，則抗氫脆性或焊接性降低，因此，作成0.3%以下。較為理想的是0.25%以下，更為理想的是0.22%以下。 C is the element necessary to obtain the desired tensile strength. If it is less than 0.14%, the desired tensile strength cannot be obtained, and therefore, it is made 0.14% or more. More preferably, it is 0.17% or more. On the other hand, when it is more than 0.3%, the hydrogen embrittlement resistance or the weldability is lowered, so that it is made 0.3% or less. More preferably, it is 0.25% or less, and more desirably 0.22% or less.

(Si：0.001~2.0%) (Si: 0.001~2.0%)

Si乃對於鋼板之高強度化有效之元素。若小於0.001%，則無法顯現添加效果，因此，作成0.001%以上。較為理想的是0.010%以上。另一方面，若大於2.0%，則與熔融鍍鋅之潤濕性及合金化速度降低。又，Si乃肥粒鐵生成元素，因此，若Si含量大於2.0%，則難以將多邊形肥粒鐵之面積率作成10%以下。故，Si含量乃作成2.0%以下。理想的是1.50%以下，較為理想的是0.90%以下，更為理想的是0.50% 以下。 Si is an effective element for the high strength of the steel sheet. If it is less than 0.001%, the effect of addition cannot be exhibited, and therefore, it is made 0.001% or more. More preferably, it is 0.010% or more. On the other hand, when it is more than 2.0%, the wettability and alloying speed with hot-dip galvanizing are lowered. Further, since Si is a ferrite-forming element, if the Si content is more than 2.0%, it is difficult to set the area ratio of the polygonal ferrite iron to 10% or less. Therefore, the Si content is made 2.0% or less. The ideal is 1.50% or less, more preferably 0.90% or less, and even more preferably 0.50%. the following.

(Mn：2.0~4.0%) (Mn: 2.0~4.0%)

Mn乃強力之沃斯田鐵安定化元素，且為對於鋼板之淬火性提升有效之元素。若小於2.0%，則無法充分地顯現添加效果，因此，作成2.0%以上。較為理想的是2.2%以上。另一方面，若大於4.0%，則抗氫脆性降低，因此，作成4.0%以下。較為理想的是3.5%以下，更為理想的是3.0%以下。 Mn is a powerful Worthite iron stabilizer element and is an effective element for the hardenability improvement of steel sheets. If it is less than 2.0%, the effect of addition cannot be sufficiently exhibited, so that it is made 2.0% or more. More than ideal is 2.2% or more. On the other hand, when it is more than 4.0%, the hydrogen embrittlement resistance is lowered, so that it is made 4.0% or less. More preferably, it is 3.5% or less, and more preferably 3.0% or less.

(P：0.05%以下) (P: 0.05% or less)

P乃固溶強化元素，且為對於鋼板之高強度化有效之元素。然而，若大於0.05%，則焊接性及韌性降低，因此，作成0.05%以下。較為理想的是0.02%以下。下限並無特殊之限制，然而，實用上，0.001%乃實質上的下限。 P is a solid solution strengthening element and is an element effective for increasing the strength of the steel sheet. However, when it is more than 0.05%, the weldability and toughness are lowered, so that it is 0.05% or less. More preferably, it is 0.02% or less. The lower limit is not particularly limited, however, practically, 0.001% is a substantially lower limit.

(S：0.01%以下) (S: 0.01% or less)

S乃雜質元素，且為越少越好的元素。若大於0.01%，則於鋼中形成MnS而使韌性及擴孔性劣化，因此，作成0.01%以下。較為理想的是0.005%以下，更為理想的是0.002%以下。下限並無特殊之限制，然而，實用上，0.0001%乃實質上的下限。 S is an impurity element, and the less the better the element. When it is more than 0.01%, MnS is formed in the steel to deteriorate the toughness and the hole expandability, so that it is made 0.01% or less. It is preferably 0.005% or less, more preferably 0.002% or less. The lower limit is not particularly limited, however, practically, 0.0001% is a substantially lower limit.

(N：0.01%以下) (N: 0.01% or less)

N乃雜質元素，且為越少越好的元素。若大於0.01%，則於鋼中生成粗大的氮化物而擴孔性降低，因此，作成0.01%以下。較為理想的是0.005%以下。下限並無特殊之限制，然而，實用上，0.001%乃實質上的下限。 N is an impurity element, and the less the better the element. When it is more than 0.01%, coarse nitride is formed in the steel and the hole expandability is lowered. Therefore, it is made 0.01% or less. More preferably, it is 0.005% or less. The lower limit is not particularly limited, however, practically, 0.001% is a substantially lower limit.

(Al：0.001~1.00%) (Al: 0.001~1.00%)

Al乃用以脫氧而添加的元素。若小於0.001%，則無法顯現添加效果，因此，作成0.001%以上。較為理想的是0.010%以上。另一方面，若大於1.00%，則添加效果飽和，同時成本上升，除此之外，鋼的變態溫度上升而增加熱壓延時之負載，因此，作成1.00%以下。較為理想的是0.50%以下，更為理想的是0.20%以下。 Al is an element added for deoxidation. If it is less than 0.001%, the effect of addition cannot be exhibited, and therefore, it is made 0.001% or more. More preferably, it is 0.010% or more. On the other hand, when it is more than 1.00%, the effect of addition is saturated and the cost is increased. In addition, the abnormal temperature of the steel rises and the load of the hot pressing delay increases, so that it is made 1.00% or less. It is preferably 0.50% or less, more preferably 0.20% or less.

(Ti：0.001~0.10%) (Ti: 0.001~0.10%)

Ti乃以下元素：於鋼中形成TiN而將N固定，並發揮可抑制構成淬火性降低因子的BN生成之作用，同時將加熱時之沃斯田鐵粒徑微細化，有助於韌性及抗氫脆性之提升。若小於0.001%，則無法顯現添加效果，因此，作成0.001%以上。較為理想的是0.010%以上。另一方面，若大於0.10%，則生成粗大的Ti碳化物，鋼板之韌性及抗氫脆性降低，因此，作成0.10%以下。較為理想的是0.07%以下。 Ti is the following element: TiN is formed in steel to fix N, and it functions to suppress the formation of BN which constitutes a quenching reduction factor, and at the same time, the particle size of Worthite iron during heating is refined to contribute to toughness and resistance. Increased hydrogen embrittlement. If it is less than 0.001%, the effect of addition cannot be exhibited, and therefore, it is made 0.001% or more. More preferably, it is 0.010% or more. On the other hand, when it is more than 0.10%, coarse Ti carbide is formed, and the toughness and hydrogen embrittlement resistance of the steel sheet are lowered, so that it is made 0.10% or less. More preferably, it is 0.07% or less.

(B：0.0001~0.01%) (B: 0.0001~0.01%)

B乃以下元素：於鋼板之加熱時朝沃斯田鐵晶界偏析，並使沃斯田鐵晶界安定化而發揮提高鋼之淬火性之作用，同時提高晶界強度而有助於鋼板之韌性及抗氫脆性之提升。若小於0.0001%，則無法顯現添加效果，因此，作成0.0001%以上。較為理想的是0.0006%以上，更為理想的是0.0011%以上。 B is the following element: segregation toward the Worthite iron grain boundary during heating of the steel sheet, and the stability of the Worstian iron grain boundary to improve the quenching property of the steel, and at the same time increase the grain boundary strength to contribute to the toughness and hydrogen resistance of the steel sheet. Increase in brittleness. If it is less than 0.0001%, the effect of addition cannot be exhibited, and therefore, it is made 0.0001% or more. More preferably, it is 0.0006% or more, and more desirably 0.0011% or more.

另一方面，若大於0.01%，則生成硼化物而阻礙鋼之淬火性，因此，作成0.01%以下。較為理想的是0.005%以下，更為理想的是0.004%以下。 On the other hand, when it is more than 0.01%, boride is formed and the hardenability of steel is inhibited, so that it is made 0.01% or less. It is preferably 0.005% or less, more preferably 0.004% or less.

Mo、Cr、Ni、Cu、V、Nb、Ca、Mg及REM並非必要元素，而是可於鋼板及鋼中有限度地適當含有預定量之任意元素。 Mo, Cr, Ni, Cu, V, Nb, Ca, Mg, and REM are not essential elements, but may appropriately contain a predetermined amount of any element in the steel sheet and the steel.

(Mo：0~0.50%) (Mo: 0~0.50%)

Mo乃以下元素：有助於鋼板之淬火性之提升，同時使退火步驟中加熱後之冷卻~鍍覆浸漬中產生的部變韌鐵變態延遲而有助於所需組織之形成。又，Mo乃以下元素：將加熱中的沃斯田鐵粒徑微細化，有助於韌性及抗氫脆性之提升。故，亦可含有Mo。若Mo含量小於0.001%，則無法顯現添加效果，因此，Mo含量宜為0.001%以上，更為理想的是0.050%以上。另一方面，若Mo含量大於0.50%，則添加效果飽和，同時製造成本上升，因此，Mo含量為0.50%以下，較為理想的是0.30%以下。即，「Mo：0.001~0.50%」宜成立。 Mo is the following element: it contributes to the improvement of the hardenability of the steel sheet, and at the same time, the cooling of the heating in the annealing step, the partial toughening iron generated in the plating impregnation, is delayed, and contributes to the formation of the desired structure. Further, Mo is an element which refines the particle size of the Worthite iron during heating and contributes to improvement in toughness and hydrogen embrittlement resistance. Therefore, it can also contain Mo. When the Mo content is less than 0.001%, the effect of addition cannot be exhibited. Therefore, the Mo content is preferably 0.001% or more, more preferably 0.050% or more. On the other hand, when the Mo content is more than 0.50%, the effect of addition is saturated and the production cost is increased. Therefore, the Mo content is 0.50% or less, preferably 0.30% or less. That is, "Mo: 0.001 to 0.50%" should be established.

(Cr：0~0.80%、Ni：0~1.00%、Cu：0~1.00%) (Cr: 0~0.80%, Ni: 0~1.00%, Cu: 0~1.00%)

Cr、Ni、Cu皆為對於鋼板之高強度化有效之元素。故，亦可含有Cr、Ni或Cu，抑或該等之任意組合。無論是Cr、Ni、Cu中的何者，若含量小於0.001%，則無法顯現添加效果，因此，分別宜為0.001%以上，更為理想的是0.010%以上。另一方面，若Cr含量大於0.80%，或是Ni含量大於1.00%，抑或Cu含量大於1.00%，則添加效果飽和，同時製造成本上升。故，Cr含量作成0.80%以下，Ni含量作成1.00%以下，Cu含量作成1.00%以下，較為理想的是Cr含量為0.50%以下，Ni含量為0.50%以下，Cu含量為0.50%以下。即，「Cr： 0.001~0.80%」、「Ni：0.001~1.00%」或「Cu：0.001~1.00%」，抑或該等之任意組合宜成立。 Cr, Ni, and Cu are all effective elements for increasing the strength of the steel sheet. Therefore, it may contain Cr, Ni or Cu, or any combination of these. In any of Cr, Ni, and Cu, if the content is less than 0.001%, the effect of addition cannot be exhibited. Therefore, it is preferably 0.001% or more, and more preferably 0.010% or more. On the other hand, if the Cr content is more than 0.80%, or the Ni content is more than 1.00%, or the Cu content is more than 1.00%, the effect of addition is saturated, and the manufacturing cost increases. Therefore, the Cr content is 0.80% or less, the Ni content is 1.00% or less, and the Cu content is 1.00% or less. Preferably, the Cr content is 0.50% or less, the Ni content is 0.50% or less, and the Cu content is 0.50% or less. That is, "Cr: 0.001~0.80%", "Ni: 0.001~1.00%" or "Cu: 0.001~1.00%", or any combination of these should be established.

(V：0~0.50%、Nb：0.0~0.10%) (V: 0~0.50%, Nb: 0.0~0.10%)

V及Nb乃形成碳化物並有助於鋼板之高強度化之元素。故，亦可含有V或Nb，抑或該等兩者。無論是何者元素，若含量小於0.001%，則無法顯現添加效果，因此，V含量及Nb含量皆宜作成0.001%以上，更為理想的是V含量為0.030%以上，Nb含量為0.005%以上。另一方面，若V含量大於0.50%，或是Nb含量大於0.10%，則添加效果飽和，同時成本上升，因此，V含量作成0.50%以下，Nb含量作成0.10%以下，較為理想的是V含量為0.30%以下，Nb含量為0.05%以下。即，「V：0.001~0.50%」或「Nb：0.001~0.10%」，抑或該等兩者宜成立。 V and Nb are elements which form carbides and contribute to the high strength of the steel sheet. Therefore, it is also possible to contain V or Nb, or both. In any case, if the content is less than 0.001%, the effect of addition cannot be exhibited. Therefore, the V content and the Nb content are preferably 0.001% or more, more preferably 0.03% or more, and Nb content is 0.005% or more. On the other hand, if the V content is more than 0.50%, or the Nb content is more than 0.10%, the effect of addition is saturated and the cost is increased. Therefore, the V content is made 0.50% or less, and the Nb content is made 0.10% or less, preferably V content. It is 0.30% or less, and the Nb content is 0.05% or less. That is, "V: 0.001 to 0.50%" or "Nb: 0.001 to 0.10%", or both should be established.

(Ca：0.00~0.01%、Mg：0.00~0.01%、REM：0.00~0.01%、Bi：0.00~0.01%) (Ca: 0.00~0.01%, Mg: 0.00~0.01%, REM: 0.00~0.01%, Bi: 0.00~0.01%)

Ca、Mg、REM乃有助於鋼中夾雜物之微細分散化。又，Bi乃減輕鋼中的Mn、Si等取代型合金元素之微偏析。任一者皆為有助於鋼板之韌性及加工性提升之元素。故，亦可含有Ca、Mg、REM或Bi，抑或該等之任意組合。無論是何者元素，若含量小於0.0001%，則無法顯現添加效果，因此，較為理想的是0.0001%以上，更為理想的是0.0010%以上。另一方面，無論是何者元素，若大於0.01%，則會阻礙延性，因此，作成0.01%以下，較為理想的是0.005%以下。即，「Ca：0.0001~0.01%」、「Mg：0.0001~0.01%」、「REM：0.0001~0.01%」或「Bi：0.0001~0.01%」，抑或該等之任意組合宜成立。 Ca, Mg, and REM contribute to the fine dispersion of inclusions in the steel. Further, Bi reduces microsegregation of substituted alloying elements such as Mn and Si in steel. Either one is an element that contributes to the toughness and workability of the steel sheet. Therefore, it may contain Ca, Mg, REM or Bi, or any combination of these. Regardless of the element, if the content is less than 0.0001%, the effect of addition cannot be exhibited. Therefore, it is preferably 0.0001% or more, and more preferably 0.0010% or more. On the other hand, if it is more than 0.01%, the ductility is inhibited. Therefore, it is preferably 0.01% or less, and more preferably 0.005% or less. That is, "Ca: 0.0001 to 0.01%", "Mg: 0.0001 to 0.01%", and "REM: 0.0001 to 0.01%" Or "Bi: 0.0001~0.01%", or any combination of these should be established.

其次，說明有關本發明實施形態之熔融鍍鋅鋼板之鋼組織限定理由。於以下說明中，只要未特別事先聲明，屬於構成鋼組織的相或組織之比例單位之「%」乃意味著任意截面中的面積率(%)。有關本發明實施形態之熔融鍍鋅鋼板乃具有以下所示之鋼組織：以面積率計，多邊形肥粒鐵：10%以下、上部變韌鐵：20%以下、殘留沃斯田鐵：5%以下、麻田散鐵：70%以上、具有個數密度為1×10⁶/mm²以上之Fe碳化物的麻田散鐵：相對於整體麻田散鐵為50%以上，及平均有效結晶粒徑：5.0μm以下。 Next, the reason for limiting the steel structure of the hot-dip galvanized steel sheet according to the embodiment of the present invention will be described. In the following description, "%" which is a proportional unit of a phase or a structure constituting a steel structure means the area ratio (%) in an arbitrary cross section unless otherwise stated. The hot-dip galvanized steel sheet according to the embodiment of the present invention has the steel structure shown below: in terms of area ratio, polygonal ferrite iron: 10% or less, upper toughened iron: 20% or less, and residual Worthite iron: 5% In the following, Ma Tian loose iron: 70% or more, Ma Tian loose iron having a number of Fe carbides having a density of 1 × 10 ⁶ /mm ² or more: 50% or more with respect to the whole granulated iron, and an average effective crystal grain size: Below 5.0 μm.

(多邊形肥粒鐵：10%以下、上部變韌鐵：20%以下) (Polygonal ferrite iron: 10% or less, upper toughened iron: 20% or less)

若多邊形肥粒鐵大於10%，或是上部變韌鐵大於20%，則鋼板軟質化，難以獲得75%以上之降伏比，因此，多邊形肥粒鐵乃作成10%以下，上部變韌鐵乃作成20%以下。較為理想的是多邊形肥粒鐵為5%以下，上部變韌鐵為10%以下。 If the polygon ferrite iron is greater than 10%, or the upper toughening iron is greater than 20%, the steel sheet is softened, and it is difficult to obtain a fall ratio of 75% or more. Therefore, the polygonal ferrite iron is made 10% or less, and the upper tough iron is Make 20% or less. It is preferable that the polygonal ferrite iron is 5% or less, and the upper toughened iron is 10% or less.

(殘留沃斯田鐵：5%以下) (Remaining Worth Iron: 5% or less)

若殘留沃斯田鐵大於5%，則壓製成型後藉由加工誘發變態自殘留沃斯田鐵變態的新生麻田散鐵會影響到氫脆化，難以獲得優異之抗氫脆化特性，因此，殘留沃斯田鐵乃作成5%以下。較為理想的是2%以下。 If the residual Worthite iron is more than 5%, the new Matian iron which is metamorphosed by the processing and the metamorphosis from the residual Worthite iron after the press molding will affect the hydrogen embrittlement, and it is difficult to obtain excellent hydrogen embrittlement resistance. The residual Worthite iron is made 5% or less. More preferably, it is 2% or less.

(麻田散鐵：70%以上) (Ma Tian loose iron: 70% or more)

若麻田散鐵小於70%，則無法確保所需強度，因此，作成70%以上。較為理想的是80%以上。 If the loose iron in the field is less than 70%, the required strength cannot be ensured. More than 70%. More than ideal is more than 80%.

鋼組織之面積率之算出乃如下述般進行。在有關多邊形肥粒鐵、上部變韌鐵、波來鐵、雪明碳鐵、麻田散鐵、回火麻田散鐵之面積率方面，切出鋼板之壓延方向截面，並藉由硝太蝕劑使鋼組織現出，且藉由掃描型電子顯微鏡(倍率：5000倍，10視野)，拍攝所現出鋼組織中的1/8~3/8厚度位置，並將藉由計點法自所獲得組織照片算出的平均值作成面積率。 The calculation of the area ratio of the steel structure was carried out as follows. In terms of the area ratio of the polygonal ferrite iron, the upper toughened iron, the Bora iron, the ferritic carbon iron, the maitian loose iron, and the tempered granulated iron, the rolling direction section of the steel sheet is cut out, and the nitrate etchant is used. The steel structure is made out, and by scanning electron microscopy (magnification: 5000 times, 10 fields of view), the thickness of 1/8~3/8 in the steel structure is taken, and will be measured by the counting method. The average value calculated from the tissue photograph was obtained to create an area ratio.

在有關殘留沃斯田鐵之面積率方面，將鋼板之1/4厚度之面作成觀察面並進行X射線繞射，且將自bcc與fcc之峰值面積比算出的值作成面積率。 Regarding the area ratio of the residual Worthite iron, the 1/4 thickness surface of the steel sheet was made into an observation surface and X-ray diffraction was performed, and the area ratio calculated from the peak area ratio of bcc and fcc was made into the area ratio.

(具有個數密度為1×10⁶/mm²以上之Fe碳化物的麻田散鐵：相對於整體麻田散鐵為50%以上) (Massao iron with a number of Fe carbides with a density of 1×10 ⁶ /mm ² or more: 50% or more relative to the whole granulated iron)

為了兼顧75%以上之降伏比與優異之抗氫脆化特性，在鋼組織中所含麻田散鐵中，將以面積率計50%以上之區域作成具有個數密度為1.0×10⁶/mm²以上之Fe碳化物的麻田散鐵。 In order to balance the lodging ratio of 75% or more and the excellent hydrogen embrittlement resistance, in the field of the loose iron contained in the steel structure, a region having an area ratio of 50% or more is formed to have a number density of 1.0 × 10 ⁶ /mm.麻田散铁 of ² or more Fe carbides.

若具有個數密度為1.0×10⁶/mm²以上之Fe碳化物之麻田散鐵小於整體麻田散鐵之50%，則難以獲得75%以上之降伏比，因此，具有個數密度為1.0×10⁶/mm²以上之Fe碳化物之麻田散鐵乃作成50%以上。較為理想的是65%以上。又，若Fe碳化物之個數密度小於1.0×10⁶/mm²，則無法獲得優異之抗氫脆化特性，因此，Fe碳化物之個數密度乃作成1.0×10⁶/mm²以上。較為理想的是5.0×10⁶/mm²以上。 If the granulated loose iron having a Fe carbide having a number density of 1.0×10 ⁶ /mm ² or more is less than 50% of the whole granulated iron, it is difficult to obtain a fall ratio of 75% or more, and therefore, the number density is 1.0×. The granulated iron of Fe carbide of 10 ⁶ /mm ² or more is made 50% or more. More than ideal is more than 65%. Further, when the number density of Fe carbides is less than 1.0 × 10 ⁶ /mm ² , excellent hydrogen embrittlement resistance cannot be obtained. Therefore, the number density of Fe carbides is made 1.0 × 10 ⁶ /mm ² or more. More preferably, it is 5.0 × 10 ⁶ /mm ² or more.

在有關存在於麻田散鐵之Fe碳化物之個數密度方面，切出鋼板之壓延方向截面，並藉由硝太蝕劑現出鋼組織，且藉由掃描型電子顯微鏡(倍率：5000倍，10視野)，拍攝所現出鋼組織中的1/8~3/8厚度位置，並於所獲得組織照片中，測定Fe碳化物之個數，並算出個數密度。 In terms of the number density of Fe carbides present in the granulated iron, the section of the steel sheet in the rolling direction is cut out, and the steel structure is produced by the oxidizing agent, and by scanning electron microscopy (magnification: 5000 times, 10 fields of view, the 1/8~3/8 thickness position in the steel structure is taken, and the number of Fe carbides is measured in the obtained photograph of the tissue, and the number density is calculated.

(平均有效結晶粒徑：5.0μm以下) (Average effective crystal grain size: 5.0 μm or less)

有效結晶粒徑乃意味著被結晶方位差10°以上之晶界包圍的區域(後述)之大小(粒徑)。舉例言之，若為麻田散鐵，則相當於塊體粒徑。 The effective crystal grain size means the size (particle diameter) of a region (described later) surrounded by grain boundaries having a crystal orientation difference of 10 or more. For example, if it is a granulated iron, it is equivalent to the bulk particle size.

為了獲得優異之抗氫脆化特性，將平均有效結晶粒徑作成5.0μm以下。若平均有效結晶粒徑大於5.0μm，則大角度晶界之晶界面積減少而抗氫脆化特性降低，因此，平均有效結晶粒徑乃作成5.0μm以下。較為理想的是4.0μm以下。 In order to obtain excellent hydrogen embrittlement resistance, the average effective crystal grain size is made 5.0 μm or less. When the average effective crystal grain size is more than 5.0 μm, the grain boundary area of the large-angle grain boundary is reduced and the hydrogen embrittlement resistance is lowered. Therefore, the average effective crystal grain size is 5.0 μm or less. It is preferably 4.0 μm or less.

平均有效結晶粒徑乃藉由EBSP-OIM(電子背向散射繞射圖形-定位影像顯微術，Electron Back Scatter Diffraction Pattern-Orientation Image Microscopy)法進行測定。EBSP-OIM法乃將電子射線照射至掃描型電子顯微鏡(SEM)內高傾斜的試料，並藉由高感度相機，拍攝於後方散射所形成的菊池圖形。又，藉由利用電腦之影像處理，於短暫等待期間測定照射點之結晶方位。又，可使用軟體來分析測定值。 The average effective crystal grain size was measured by an EBSP-OIM (Electron Back Scatter Diffraction Pattern-Orientation Image Microscopy) method. The EBSP-OIM method irradiates an electron beam to a highly oblique sample in a scanning electron microscope (SEM), and captures a Kikuchi pattern formed by rear scattering by a high-sensitivity camera. Further, by using image processing by a computer, the crystal orientation of the irradiation spot is measured during a short waiting period. Also, software can be used to analyze the measured values.

於EBSP-OIM法中，可定量分析鋼組織之微細構造及結晶方位。EBSP-OIM法中的解析度乃依存於SEM之解析度，但可藉由最小20nm之解析度進行分析。於本發明中，為了辨識可構成有效晶粒邊界的塊體邊界，以臨界值10°定義鋼之晶粒邊界，並於映射方位差10°以上之晶粒邊界的影像中，將晶粒視覺化而求取平均結晶粒徑。 In the EBSP-OIM method, the fine structure and crystal orientation of the steel structure can be quantitatively analyzed. The resolution in the EBSP-OIM method depends on the solution of SEM Resolution, but can be analyzed by a resolution of at least 20 nm. In the present invention, in order to identify the boundary of the block which can constitute the effective grain boundary, the grain boundary of the steel is defined by a critical value of 10°, and the grain vision is imaged in the image of the grain boundary where the orientation difference is more than 10°. The average crystal grain size was obtained.

(鋼全體之平均差排密度：1.0×10¹⁵/m²~1.0×10¹⁶/m²) (Average difference density of the whole steel: 1.0×10 ¹⁵ /m ² ~1.0×10 ¹⁶ /m ² )

為了兼顧1300MPa以上之拉伸強度與優異之抗氫脆化特性，宜將鋼全體之平均差排密度作成1.0×10¹⁵/m²~1.0×10¹⁶/m²。差排有助於材料之強化，因此，若為高強度化之觀點，則以大量含有者為佳，然而，若為氫脆化特性之觀點，則以少者為佳。若平均差排密度小於1.0×10¹⁵/m²，則無法獲得1300MPa以上之拉伸強度，因此，較為理想的是作成1.0×10¹⁵/m²以上，更為理想的是5.0×10¹⁵/m²以上。 In order to achieve both tensile strength of 1300 MPa or more and excellent hydrogen embrittlement resistance, it is preferable to set the average difference density of the entire steel to 1.0 × 10 ¹⁵ /m ² to 1.0 × 10 ¹⁶ /m ² . Since the difference is advantageous for the reinforcement of the material, it is preferable to use a large amount of the material in view of high strength. However, in view of hydrogen embrittlement characteristics, it is preferable. When the average difference discharge density is less than 1.0 × 10 ¹⁵ /m ² , the tensile strength of 1300 MPa or more cannot be obtained. Therefore, it is preferable to form 1.0 × 10 ¹⁵ /m ² or more, and more preferably 5.0 × 10 ¹⁵ / m ² or more.

另一方面，若平均差排密度大於1.0×10¹⁶/m²，則藉由鋼中的差排與氫之相互作用，鋼材中的滲入氫量增加而抗氫脆化特性劣化，因此，較為理想的是作成1.0×10¹⁶/m²以下，更為理想的是0.5×10¹⁶/m²以下。 On the other hand, if the average difference discharge density is more than 1.0 × 10 ¹⁶ /m ² , the amount of infiltrated hydrogen in the steel material increases and the hydrogen embrittlement resistance deteriorates due to the interaction between the difference between the steel and the hydrogen. It is preferably made 1.0 × 10 ¹⁶ /m ² or less, more preferably 0.5 × 10 ¹⁶ /m ² or less.

鋼全體之平均差排密度乃根據非專利文獻「CAMP-ISIJ Vol.17(2004)p.396」之「利用X射線繞射之差排密度之評價方法」所揭示之方法，自(110)α、(211)α、(220)α之半值寬算出平均差排密度。 The average difference in density of the entire steel is based on the method disclosed in the "Method for Evaluating the Difference in Density of X-Ray Diffraction by CAMP-ISIJ Vol. 17 (2004) p.396", from (110) The half value width of α, (211) α, and (220) α is calculated as the average difference row density.

若藉由如上述構造有關本發明實施形態之熔融鍍鋅鋼板，則可獲得例如1300MPa以上之拉伸強度、75%以上之降伏比及優異之抗氫脆化特性。若拉伸強度小於 1300MPa，則有時會難以確保輕量化與碰撞安全性，因此，宜獲得1300MPa以上之拉伸強度，更宜獲得1350MPa以上之拉伸強度。若降伏比小於75%，則有時會難以確保碰撞安全性，因此，宜獲得75%以上之降伏比，且宜獲得80%以上之降伏比。 When the hot-dip galvanized steel sheet according to the embodiment of the present invention is constructed as described above, for example, a tensile strength of 1300 MPa or more, a fall ratio of 75% or more, and excellent hydrogen embrittlement resistance can be obtained. If the tensile strength is less than At 1300 MPa, it may be difficult to ensure weight reduction and collision safety. Therefore, it is preferable to obtain a tensile strength of 1300 MPa or more, and it is more preferable to obtain a tensile strength of 1350 MPa or more. If the drop ratio is less than 75%, it is sometimes difficult to ensure collision safety. Therefore, it is preferable to obtain a fall ratio of 75% or more, and it is preferable to obtain a fall ratio of 80% or more.

固溶B量宜為0.0010質量%以上，舊沃斯田鐵粒徑宜為1.0μm~7.0μm。固溶B乃提高舊沃斯田鐵粒之晶界強度而有助於鋼板之韌性及抗氫脆性之提升。然而，若固溶B量小於0.0010質量%，則有時無法獲得充分之韌性及抗氫脆性。故，固溶B量宜作成0.0010質量%以上，更宜作成0.0015質量%以上。又，若舊沃斯田鐵粒徑小於1.0μm，則舊沃斯田鐵粒之晶界面積過大，利用固溶B之晶界強度之提升有時會不足。故，舊沃斯田鐵粒徑宜作成1.0μm以上，較為理想的是2.0μm以上。另一方面，若舊沃斯田鐵粒徑大於7.0μm，則材料之韌性劣化，因此，抗氫脆化特性亦劣化。故，舊沃斯田鐵粒徑宜作成7.0μm以下。 The amount of solid solution B is preferably 0.0010% by mass or more, and the particle size of the old Worthite is preferably 1.0 μm to 7.0 μm. Solid solution B improves the grain boundary strength of the old Worthfield iron particles and contributes to the toughness and hydrogen embrittlement resistance of the steel plate. However, if the amount of solid solution B is less than 0.0010% by mass, sufficient toughness and hydrogen embrittlement resistance may not be obtained. Therefore, the amount of solid solution B should preferably be 0.0010% by mass or more, and more preferably 0.0015% by mass or more. Further, if the particle size of the old Worthite iron is less than 1.0 μm, the grain boundary area of the old Worthfield iron grain is too large, and the increase in the grain boundary strength by the solid solution B may be insufficient. Therefore, the particle size of the old Worthite iron should be made 1.0 μm or more, and more preferably 2.0 μm or more. On the other hand, if the particle size of the old Worthite iron is more than 7.0 μm, the toughness of the material is deteriorated, and therefore the hydrogen embrittlement resistance is also deteriorated. Therefore, the particle size of the old Worthfield iron should be made 7.0 μm or less.

固溶B量可藉由自熔融鍍鋅鋼板中所含B之總質量減去硼化物等析出物中所含B之質量而算出。析出物中所含B之質量可藉由利用萃取殘渣法測定B析出物之質量，並將其換算成B析出物中所含B之質量而獲得。萃取殘渣法中B析出物之定量方法例如揭示於非專利文獻2中。舊沃斯田鐵粒徑乃切出鋼板之壓延方向截面，並藉由苦味酸酒精溶液現出舊沃斯田鐵晶界，且藉由掃描型電子顯微鏡(倍率：1000倍，5視野)，拍攝所現出舊沃斯田鐵晶界中的1/8~3/8 厚度位置，並使用藉由線段法自所獲得組織照片算出的平均值。 The amount of solid solution B can be calculated by subtracting the mass of B contained in the precipitate such as boride from the total mass of B contained in the hot-dip galvanized steel sheet. The mass of B contained in the precipitate can be obtained by measuring the mass of the B precipitate by the extraction residue method and converting it into the mass of B contained in the B precipitate. A method for quantifying the precipitate of B in the extraction residue method is disclosed, for example, in Non-Patent Document 2. The old Worthfield iron particle size is cut out from the rolling direction section of the steel plate, and the old Worthfield iron grain boundary is produced by a picric acid alcohol solution, and by a scanning electron microscope (magnification: 1000 times, 5 fields of view), the shooting place 1/8~3/8 of the old Worthfield iron grain boundary The thickness position and the average value calculated from the obtained tissue photograph by the line segment method.

固溶B量與舊沃斯田鐵粒徑之積宜為0.0010質量%．μm以上。舊沃斯田鐵粒徑越小，舊沃斯田鐵粒之晶界面積越大。故，為了獲得一定之晶界強度，舊沃斯田鐵粒徑越小，越需要大量之固溶B。發明人在此種觀點下進行調查時明白，當固溶B量與舊沃斯田鐵粒徑之積為0.0010質量%．μm以上時，特別是可獲得優異之抗氫脆化特性。 The amount of solid solution B and the particle size of the old Worthite iron is preferably 0.0010% by mass. More than μm. The smaller the particle size of the old Worthfield iron, the larger the grain boundary area of the old Worthfield iron grain. Therefore, in order to obtain a certain grain boundary strength, the smaller the particle size of the old Worthfield iron, the more the solid solution B needs to be obtained. When the inventors conducted this investigation, they understood that the product of the amount of solid solution B and the particle size of the old Worthite was 0.0010% by mass. When it is more than μm, in particular, excellent hydrogen embrittlement resistance can be obtained.

其次，說明有關本發明實施形態之熔融鍍鋅鋼板之製造方法。於該製造方法中，依該順序進行具有上述化學組成的扁胚之熱壓延、冷壓延、連續退火、熔融鍍鋅處理、合金化處理及回火。 Next, a method of producing a hot-dip galvanized steel sheet according to an embodiment of the present invention will be described. In the production method, hot rolling, cold rolling, continuous annealing, hot-dip galvanizing treatment, alloying treatment, and tempering of the flat embryo having the above chemical composition are carried out in this order.

於熱壓延中，進行扁胚加熱、粗壓延、精壓延及冷卻。 In the hot calendering, flat embryo heating, coarse calendering, fine rolling and cooling are performed.

扁胚加熱溫度乃作成1180℃以上。若扁胚加熱溫度小於1180℃，則無法充分地溶解扁胚中的硼化合物，且無法確保充分量之固溶硼。舉例言之，扁胚可使用藉由連續鑄造製得之扁胚、藉由造塊法製作之扁胚、藉由薄扁胚鑄造法鑄造之扁胚。扁胚可於鑄造後在保持於1180℃以上之溫度下直接供給至熱壓延設備，亦可在冷卻至小於1180℃之溫度，例如室溫後進行加熱而供給至熱壓延設備。 The radish heating temperature is made above 1180 °C. If the radish heating temperature is less than 1180 ° C, the boron compound in the spheroid is not sufficiently dissolved, and a sufficient amount of solid solution boron cannot be secured. For example, the flat embryo can use a flat embryo made by continuous casting, a flat embryo made by a block making method, and a flat embryo cast by a thin flat embryo casting method. The flat embryo may be directly supplied to the hot rolling apparatus at a temperature maintained at 1180 ° C or higher after casting, or may be supplied to the hot rolling apparatus by heating after cooling to a temperature of less than 1,180 ° C, for example, room temperature.

於粗壓延中，將溫度作成1050℃以上且1150℃以下，將總軋縮率作成50%以上。這是為了在熱壓延中充分地產生再結晶，並使熱軋鋼板之組織均質化。 In the rough rolling, the temperature is made 1050 ° C or more and 1150 ° C or less, and the total rolling reduction ratio is made 50% or more. This is for sufficiently recrystallizing in hot rolling and homogenizing the structure of the hot rolled steel sheet.

於精壓延中，將藉由1050℃以下之溫度進行的最初道次至倒數第2道次之總軋縮率作成60%以上且95%以下，將最終道次之壓延率作成5%以上且30%以下，將最終道次之溫度作成880℃以上且980℃以下。若藉由1050℃以下之溫度進行的最初道次至倒數第2道次之總軋縮率大於95%，或是最終道次之壓延率大於30%，則於精壓延中促進硼化物之析出，無法確保充分量之固溶硼。當最終道次之溫度小於880℃時亦如此，於精壓延中促進硼化物之析出，無法確保充分量之固溶硼。若藉由1050℃以下之溫度進行的最初道次至倒數第2道次之總軋縮率小於60%，或是最終道次之壓延率小於10%，則熱軋鋼板之組織粗大化，無法獲得所期望之有效結晶粒徑。 In the finish rolling, the total rolling reduction rate from the first pass to the second last pass of the temperature of 1050 ° C or lower is 60% or more and 95% or less, and the rolling rate of the final pass is 5% or more. 30% or less, the temperature of the final pass is 880 ° C or more and 980 ° C or less. If the total rolling reduction from the initial pass to the temperature of 1050 ° C to the second pass is greater than 95%, or the final pass rate is greater than 30%, the precipitation of boride is promoted in the finish rolling It is impossible to ensure a sufficient amount of solid solution boron. This is also the case when the temperature of the final pass is less than 880 ° C, and the precipitation of boride is promoted in the finish calendering, and a sufficient amount of solid solution boron cannot be ensured. If the total rolling reduction rate from the initial pass to the temperature of 1050 ° C to the second pass is less than 60%, or the final pass rolling ratio is less than 10%, the microstructure of the hot rolled steel sheet is coarsened. The desired effective crystal grain size is obtained.

冷卻乃於自精壓延結束經過1秒鐘以上後進行，並藉由5℃/秒以上且50℃/秒以下之冷卻速度，冷卻至450℃以上且700℃以下之溫度，並於該溫度下進行捲繞。若在自精壓延結束經過1秒鐘以上之前開始冷卻，則沃斯田鐵無法充分地再結晶，異向性顯著化。若冷卻速度小於5℃/秒，則會促進高溫區的肥粒鐵變態，熱軋鋼板之組織粗大化，無法獲得所期望之有效結晶粒徑。冷卻速度之上限並未特別設置，然而，實質上難以作成50℃/秒以上。若捲繞溫度大於700℃，則熱軋鋼板之組織粗大化，無法獲得所期望之有效結晶粒徑，或者會促進硼化物之析出，無法確保充分量之固溶硼。若捲繞溫度小於450℃，則熱軋鋼板之強度過剩，後續之冷壓延會變得困難。捲繞溫度宜作成500℃以上且650℃以下。 The cooling is performed after the completion of the self-finishing rolling for 1 second or more, and is cooled to a temperature of 450 ° C or higher and 700 ° C or lower by a cooling rate of 5 ° C /sec or more and 50 ° C / sec or less, and at the temperature. Winding is performed. When cooling is started before the completion of the self-refining rolling for 1 second or more, the Worthite iron cannot be sufficiently recrystallized, and the anisotropy is remarkable. When the cooling rate is less than 5 ° C / sec, the ferrite and iron in the high temperature region are promoted, and the structure of the hot rolled steel sheet is coarsened, and the desired effective crystal grain size cannot be obtained. The upper limit of the cooling rate is not particularly set, however, it is substantially difficult to form 50 ° C / sec or more. When the winding temperature is more than 700 ° C, the structure of the hot-rolled steel sheet is coarsened, the desired effective crystal grain size cannot be obtained, or the precipitation of boride is promoted, and a sufficient amount of solid solution boron cannot be secured. If the winding temperature is less than 450 ° C, the strength of the hot-rolled steel sheet is excessive, and subsequent cold rolling becomes difficult. The winding temperature should be made above 500 °C And below 650 ° C.

於捲繞後，遵循常法進行熱軋鋼板之酸洗。亦可進行熱軋鋼板之調質壓延。藉由調質壓延，可矯正形狀，或者提升酸洗性。 After the winding, the pickling of the hot rolled steel sheet is carried out in accordance with a usual method. It is also possible to carry out quenching and tempering of hot rolled steel sheets. By quenching and tempering, the shape can be corrected or the pickling property can be improved.

於冷壓延中，將軋縮率作成20%以上且80%以下。若軋縮率小於20%，則於退火中無法獲得微細之沃斯田鐵粒。另一方面，若軋縮率大於80%，則壓延加重會變得過大，導致冷軋機之負載增大。軋縮率宜作成30%以上且70%以下。 In the cold rolling, the rolling reduction ratio is made 20% or more and 80% or less. If the rolling reduction ratio is less than 20%, fine Worthfield iron particles cannot be obtained during annealing. On the other hand, if the rolling reduction ratio is more than 80%, the calendering is increased too much, resulting in an increase in the load of the cold rolling mill. The rolling reduction ratio should be made 30% or more and 70% or less.

於連續退火中，進行升溫、保持及冷卻。 During continuous annealing, the temperature is raised, maintained, and cooled.

於升溫中，將700℃以上且Ac₃點以下之溫度區中的平均加熱速度作成0.1℃/秒以上且10℃/秒以下。藉由將該平均加熱速度作成10℃/秒以下，可促進硼元素朝沃斯田鐵晶界之偏析。另一方面，若該平均加熱速度小於0.1℃/秒，則鋼板之加熱需要長時間，損害生產性，因此，將其作成實質上的下限。 In the temperature rise, the average heating rate in a temperature range of 700 ° C or more and Ac ₃ point or less is made 0.1 ° C / sec or more and 10 ° C / sec or less. By setting the average heating rate to 10 ° C / sec or less, segregation of boron element toward the Worthfield iron grain boundary can be promoted. On the other hand, if the average heating rate is less than 0.1 ° C / sec, the heating of the steel sheet takes a long time and the productivity is impaired, so that it is set to a substantially lower limit.

於升溫後，以1秒鐘以上且500秒鐘以下之時間保持於Ac₃點以上且900℃以下之溫度區。若保持溫度小於Ac₃點，或者保持時間小於1秒鐘，則無法充分地沃斯田鐵化。另一方面，若保持溫度大於900℃，則沃斯田鐵粒粗大化，有效結晶粒徑變得過大而抗氫脆性劣化。若保持時間大於500秒鐘，則損害生產性。 After the temperature is raised, the temperature is maintained at a temperature range of Ac ₃ or more and 900 ° C or less for 1 second or longer and 500 seconds or shorter. If the holding temperature is less than Ac ₃ point, or the holding time is less than 1 second, it is not possible to sufficiently fertilize Worth. On the other hand, when the temperature is maintained at more than 900 ° C, the Worthfield iron particles are coarsened, the effective crystal grain size becomes excessively large, and the hydrogen embrittlement resistance is deteriorated. If the holding time is longer than 500 seconds, the productivity is impaired.

於保持後，進行自保持溫度至450℃以上且600℃以下之溫度之冷卻。自保持溫度至650℃之平均冷卻速度乃作成0.5℃/秒以上。若該平均冷卻速度小於0.5℃/秒，則肥粒鐵變態過度地進行，多邊形肥粒鐵之面積率有時會大於10%。自650℃至450℃以上且600℃以下之溫度之平均冷卻速度乃作成3℃/秒以上。若該平均冷卻速度小於3℃/秒，則肥粒鐵變態過度地進行，多邊形肥粒鐵之面積率有時會大於10%。若藉由3℃/秒以上之平均冷卻速度持續冷卻至小於450℃之溫度，則會促進上部變韌鐵之生成，上部變韌鐵之面積率有時會大於20%。藉由3℃/秒以上之平均冷卻速度之冷卻宜於470℃以上停止。若以大於600℃停止藉由3℃/秒以上之平均冷卻速度之冷卻，則之後會促進肥粒鐵之生成，肥粒鐵面積率有時會大於10%。亦可將自保持溫度至450℃以上且600℃以下之溫度之平均冷卻速度作成3℃/秒以上。 After the holding, cooling is performed from the holding temperature to a temperature of 450 ° C or more and 600 ° C or less. Average cooling rate from holding temperature to 650 ° C It is made at 0.5 ° C / sec or more. If the average cooling rate is less than 0.5 ° C / sec, the fermented iron is excessively deformed, and the area ratio of the polygonal ferrite iron is sometimes more than 10%. The average cooling rate from 650 ° C to 450 ° C and above 600 ° C is made 3 ° C / sec or more. If the average cooling rate is less than 3 ° C / sec, the fermented iron is excessively deformed, and the area ratio of the polygonal ferrite iron is sometimes more than 10%. If the cooling is continued to a temperature of less than 450 ° C by an average cooling rate of 3 ° C /sec or more, the formation of the upper toughened iron is promoted, and the area ratio of the upper toughened iron may be more than 20%. The cooling by an average cooling rate of 3 ° C / sec or more is preferably stopped above 470 ° C. If the cooling by an average cooling rate of 3 ° C /sec or more is stopped at more than 600 ° C, the formation of ferrite iron is promoted thereafter, and the area ratio of the ferrite iron is sometimes more than 10%. The average cooling rate from the holding temperature to a temperature of 450 ° C or higher and 600 ° C or lower may be made 3 ° C / sec or more.

於熔融鍍鋅處理中，進行保持以及於鍍浴中的浸漬。 In the hot-dip galvanizing treatment, the holding and the immersion in the plating bath are performed.

保持時間乃自連續退火的藉由3℃/秒以上之平均冷卻速度之冷卻開始，並將保持溫度作成450℃以上且600℃以下，將保持時間作成1秒鐘以上且1000秒鐘以下。若保持溫度小於450℃，則會促進上部變韌鐵之生成，若保持溫度大於600℃，則會促進肥粒鐵之生成。若保持時間大於1000秒鐘，則上部變韌鐵過度地生成。保持時間宜作成500秒以下，更宜作成100秒以下。在實際操作上，難以將保持時間作成小於1秒。 The holding time is started from the cooling of the continuous annealing by an average cooling rate of 3 ° C /sec or more, and the holding temperature is 450 ° C or more and 600 ° C or less, and the holding time is made 1 second or more and 1000 seconds or less. If the temperature is kept below 450 ° C, the formation of upper toughened iron is promoted, and if the temperature is maintained above 600 ° C, the formation of ferrite iron is promoted. If the holding time is longer than 1000 seconds, the upper toughening iron is excessively generated. The holding time should be made 500 seconds or less, and it should be made 100 seconds or less. In practice, it is difficult to make the hold time less than 1 second.

鍍浴可含有Fe、Si、Al、Mg、Mn、Cr、Ti及Pb 等雜質。舉例言之，鍍浴溫度乃作成420℃以上且500℃以下，鋼板之侵入板溫乃作成420℃以上且500℃以下，浸漬時間乃作成5秒鐘以下，鍍覆量乃作成每單面25g/m²以上且75g/m²以下。鍍覆量例如可藉由氣體擦拭等公知方法進行控制。 The plating bath may contain impurities such as Fe, Si, Al, Mg, Mn, Cr, Ti, and Pb. For example, the plating bath temperature is 420 ° C or more and 500 ° C or less, the intrusion plate temperature of the steel plate is 420 ° C or more and 500 ° C or less, the immersion time is 5 seconds or less, and the plating amount is 25 g per side. /m ² or more and 75 g/m ² or less. The amount of plating can be controlled, for example, by a known method such as gas wiping.

於合金化處理中，進行對處理溫度之控制及冷卻。 In the alloying treatment, the treatment temperature is controlled and cooled.

合金化處理之處理溫度乃作成480℃以上且600℃以下。當鍍浴後的鋼板溫度小於480℃時，加熱至480℃以上且600℃以下之溫度。若處理溫度小於480℃，則合金化之進行緩慢，有時會損害生產性，或者發生合金化之不均。處理溫度宜作成500℃以上。另一方面，若處理溫度大於600℃，則合金化過度地進行，鋼板之粉化性劣化。處理溫度宜作成580℃以下。 The treatment temperature of the alloying treatment is 480 ° C or more and 600 ° C or less. When the temperature of the steel sheet after the plating bath is less than 480 ° C, it is heated to a temperature of 480 ° C or more and 600 ° C or less. If the treatment temperature is less than 480 ° C, the alloying progresses slowly, sometimes impairing productivity, or uneven alloying occurs. The treatment temperature should be made at 500 ° C or higher. On the other hand, when the treatment temperature is more than 600 ° C, the alloying progresses excessively, and the powdering property of the steel sheet deteriorates. The treatment temperature should be made below 580 °C.

然後，進行自合金化處理之處理溫度至(Ms點-80℃)以下之溫度之冷卻。該冷卻中的平均冷卻速度乃作成5℃/秒以上。若該平均冷卻速度小於5℃/秒，則部變韌鐵過度地生成，有時難以獲得所期望之顯微組織。若以大於(Ms點-80℃)停止藉由5℃/秒以上之平均冷卻速度之冷卻，則麻田散鐵之生成量不足，具有個數密度為1×10⁶/mm²以上之Fe碳化物的麻田散鐵量不足。藉由5℃/秒以上之平均冷卻速度之冷卻停止溫度宜作成(Ms點-120)℃以下。 Then, cooling is performed from the treatment temperature of the alloying treatment to a temperature of (Ms point - 80 ° C) or lower. The average cooling rate during this cooling was made 5 ° C / sec or more. If the average cooling rate is less than 5 ° C / sec, the toughened iron is excessively formed, and it is sometimes difficult to obtain a desired microstructure. If the cooling by the average cooling rate of 5 ° C / sec or more is stopped at (Ms point - 80 ° C), the amount of granulated iron is insufficient, and Fe carbonization having a number density of 1 × 10 ⁶ /mm ² or more is obtained. The amount of iron in the field of Ma Tian is insufficient. The cooling stop temperature by an average cooling rate of 5 ° C /sec or more is preferably made (Ms point - 120) ° C or less.

於回火中，在200℃以上且400℃以下之溫度區進行5秒鐘以上且500秒鐘以下之保持。若保持溫度小於200℃，或者保持時間小於5秒鐘，則回火不足，其結果，會產生具有個數密度為1×10⁶/mm²以上之Fe碳化物的麻田散鐵小於整體麻田散鐵之50%，或者平均差排密度大於1.0×10¹⁶/m²之情形。保持溫度宜作成220℃以上。另一方面，若保持溫度大於400℃，或者保持時間大於500秒鐘，則回火過剩，其結果，無法獲得充分之拉伸強度。保持溫度宜作成350℃以下。回火可於熔融鍍鋅線內進行一連串的熱處理，亦可於熔融鍍鋅處理後，在以常溫捲繞後進行使用熱處理裝置之熱處理。 In the tempering, the temperature is maintained in a temperature range of 200 ° C or more and 400 ° C or less for 5 seconds or more and 500 seconds or less. If the temperature is kept below 200 ° C, or the holding time is less than 5 seconds, the tempering is insufficient, and as a result, the granulated iron having a number of Fe carbides having a density of 1 × 10 ⁶ /mm ² or more is smaller than the whole 麻田散50% of iron, or a case where the average difference density is greater than 1.0 × 10 ¹⁶ /m ² . Keep the temperature at 220 ° C or above. On the other hand, if the temperature is maintained at more than 400 ° C or the holding time is more than 500 seconds, tempering is excessive, and as a result, sufficient tensile strength cannot be obtained. Keep the temperature below 350 °C. The tempering may be carried out in a series of heat treatments in the hot-dip galvanizing line, or after the hot-dip galvanizing treatment, after the coiling at normal temperature, heat treatment using a heat treatment apparatus may be performed.

當合金化處理中藉由5℃/秒以上之平均冷卻速度之冷卻停止溫度為200℃以上且400℃以下時，亦可直接在200℃以上且400℃以下之溫度區保持5秒鐘以上且500秒鐘以下。當合金化處理中藉由5℃/秒以上之平均冷卻速度之冷卻停止溫度小於200℃時，加熱至200℃以上且400℃以下之溫度。若由生產性之觀點來看，則此時的升溫速度宜作成1℃/秒以上。 When the cooling stop temperature at an average cooling rate of 5 ° C /sec or more in the alloying treatment is 200 ° C or more and 400 ° C or less, it may be directly maintained in a temperature range of 200 ° C or more and 400 ° C or less for 5 seconds or more. Less than 500 seconds. When the cooling stop temperature is less than 200 ° C by an average cooling rate of 5 ° C /sec or more in the alloying treatment, the temperature is raised to a temperature of 200 ° C or more and 400 ° C or less. From the viewpoint of productivity, the temperature increase rate at this time should preferably be 1 ° C / sec or more.

亦可省略合金化處理。此時，藉由5℃/秒以上之平均冷卻速度，將排出自鍍浴的鋼板冷卻至(Ms點-80℃)以下之溫度，然後，進行在200℃以上且400℃以下之溫度區保持5秒鐘以上且500秒鐘以下的回火。在省略合金化處理之情況下，當排出自鍍浴時的溫度為200℃以上且360℃以下時，為了回火，亦可直接在200℃以上且400℃以下之溫度區保持5秒鐘以上且500秒鐘以下。當排出自鍍浴時的溫度小於200℃時，為了回火，乃加熱至200℃以上且400℃以下之溫度。若由生產性之觀點來看，則此時的升溫速度宜作成1℃/秒以上。 The alloying treatment can also be omitted. At this time, the steel sheet discharged from the plating bath is cooled to a temperature of (Ms point - 80 ° C) or lower by an average cooling rate of 5 ° C /sec or more, and then maintained in a temperature range of 200 ° C or more and 400 ° C or less. Tempering for more than 5 seconds and less than 500 seconds. When the alloying treatment is omitted, when the temperature at the time of discharge from the plating bath is 200 ° C or more and 360 ° C or less, in order to temper, it may be directly maintained in a temperature range of 200 ° C or more and 400 ° C or less for 5 seconds or more. And less than 500 seconds. When the temperature at which the plating bath is discharged is less than 200 ° C, it is heated to 200 ° C or higher and 400 ° C for tempering. The temperature below. From the viewpoint of productivity, the temperature increase rate at this time should preferably be 1 ° C / sec or more.

於熔融鍍鋅處理後，亦可進行調質壓延。藉由調質壓延，舉例言之，可矯正鋼板之平坦度，或者調整表面粗度。為了避免延性之劣化，利用調質壓延之伸長率宜作成2%以下。 After the hot-dip galvanizing treatment, quenching and tempering can also be carried out. By quenching and tempering, for example, the flatness of the steel sheet can be corrected, or the surface roughness can be adjusted. In order to avoid deterioration of ductility, the elongation by quenching and tempering is preferably made 2% or less.

實施例 Example

其次，說明本發明之實施例，然而，於實施例中的條件乃用以確認本發明之可實施性及效果所採用的一條件例，本發明並不限於該一條件例。只要未脫離本發明之要旨而達成本發明之目的，則本發明可採用各種條件。 Next, the embodiment of the present invention will be described. However, the conditions in the examples are a conditional example used to confirm the workability and effects of the present invention, and the present invention is not limited to the one condition example. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(實施例1) (Example 1)

將具有表1所示化學組成的鋼熔製而作成鑄片，並藉由表2所示之熱軋條件對該鑄片施行熱壓延而作成厚度3mm之熱軋鋼板。對該熱軋鋼板施行酸洗後，藉由表2所示之冷軋條件(軋縮率)施行冷壓延，並作成厚度1.2mm之冷軋鋼板。表1中的空欄表示該元素之含量小於檢測界限，剩餘部分為Fe及雜質。表1中的底線表示該數值脫離本發明之範圍。 Steel having the chemical composition shown in Table 1 was melted to form a cast piece, and the cast piece was subjected to hot rolling by the hot rolling conditions shown in Table 2 to prepare a hot rolled steel sheet having a thickness of 3 mm. After the hot-rolled steel sheet was pickled, cold rolling was performed by cold rolling conditions (rolling reduction ratio) shown in Table 2, and a cold-rolled steel sheet having a thickness of 1.2 mm was formed. The blank column in Table 1 indicates that the content of the element is less than the detection limit, and the remainder is Fe and impurities. The bottom line in Table 1 indicates that the value is outside the scope of the present invention.

藉由圖1及表3所示之熱處理條件對所製得冷軋鋼板施行熱處理後，藉由圖1及表3所示之鍍覆條件施行熔融鍍鋅。再者，藉由圖1及表3所示之條件進行合金化處理、二次冷卻、再加熱及三次冷卻，並製得合金化熔融鍍鋅鋼板。 The cold-rolled steel sheets obtained were subjected to heat treatment by the heat treatment conditions shown in Figs. 1 and 3, and then subjected to hot-dip galvanizing by the plating conditions shown in Figs. 1 and 3. Further, alloying treatment, secondary cooling, reheating, and tertiary cooling were carried out under the conditions shown in Figs. 1 and 3, and an alloyed hot-dip galvanized steel sheet was obtained.

在與壓延方向呈直角的方向中，自所製得合金化熔融鍍鋅鋼板採集JIS5號拉伸試驗片，並進行拉伸試驗，且測定拉伸強度(TS)、總伸長(EL)。遵循日本鋼鐵聯盟規格之「JFS T 1001擴孔試驗方法」，測定擴孔率(λ)。再者，遵循前述方法，識別鋼組織。 A JIS No. 5 tensile test piece was taken from the obtained alloyed hot-dip galvanized steel sheet in a direction perpendicular to the rolling direction, and subjected to a tensile test, and tensile strength (TS) and total elongation (EL) were measured. The hole expansion ratio (λ) was measured in accordance with the "JFS T 1001 Reaming Test Method" of the Japan Iron and Steel Federation specifications. Furthermore, the steel structure is identified following the method described above.

抗氫脆化特性之評價乃藉由以下試驗方法來進行。 The evaluation of the hydrogen embrittlement resistance was carried out by the following test methods.

自所製得合金化熔融鍍鋅鋼板，採集業已以間隙10%打孔為30mm φ的試驗片，並以最長24小時，將打孔試驗片浸漬於pH1之鹽酸水溶液中。每隔3小時便觀察試驗片之打孔端面，並觀察有無破裂。將即便浸漬12小時後亦未發現破裂者視為合格。 From the obtained alloyed hot-dip galvanized steel sheet, a test piece having a hole of 30 mm φ by a gap of 10% was collected, and the punched test piece was immersed in a hydrochloric acid aqueous solution of pH 1 for a maximum of 24 hours. The perforated end faces of the test pieces were observed every 3 hours, and the presence or absence of cracking was observed. Those who did not find cracks even after immersion for 12 hours were regarded as qualified.

表4與表5(接續表4)顯示所獲得之結果。表4或表5中的底線表示該數值脫離本發明之範圍。 Table 4 and Table 5 (continued Table 4) show the results obtained. The bottom line in Table 4 or Table 5 indicates that the value is outside the scope of the present invention.

在化學組成及製造方法位於本發明範圍內的發明例中，鋼組織乃位於本發明之範圍，且可獲得1300MPa以上之拉伸強度、75%以上之降伏比(YR)、良好之抗氫脆性。另一方面，在化學組成及鋼組織中的一者或兩者位於本發明範圍外的比較例中，無法獲得所期望之機械特性。 In the invention examples in which the chemical composition and the production method are within the scope of the present invention, the steel structure is within the scope of the present invention, and a tensile strength of 1300 MPa or more, a fall ratio (YR) of 75% or more, and good hydrogen embrittlement resistance can be obtained. . On the other hand, in the comparative examples in which one or both of the chemical composition and the steel structure are outside the scope of the present invention, the desired mechanical properties cannot be obtained.

(實施例2) (Example 2)

藉由表6所示之熱軋條件，對表1所示化學組成的鋼板之一部分施行熱壓延，並作成厚度3mm之熱軋鋼板。對該熱軋鋼板施行酸洗後，藉由表6所示之冷軋條件(軋縮率)施行冷壓延，並作成厚度1.2mm之冷軋鋼板。 One part of the steel sheet having the chemical composition shown in Table 1 was subjected to hot rolling by the hot rolling conditions shown in Table 6, and a hot rolled steel sheet having a thickness of 3 mm was formed. After the hot-rolled steel sheet was pickled, cold rolling was performed by cold rolling conditions (rolling reduction ratio) shown in Table 6, and a cold rolled steel sheet having a thickness of 1.2 mm was formed.

藉由圖2及表7所示之熱處理條件對所製得冷軋鋼板施行熱處理後，藉由圖2及表7所示之鍍覆條件施行熔融鍍鋅。再者，藉由圖2及表7所示之條件進行二次冷卻、再加熱及三次冷卻，並製得熔融鍍鋅鋼板。 The cold-rolled steel sheets obtained were subjected to heat treatment by the heat treatment conditions shown in Figs. 2 and 7, and then subjected to hot-dip galvanizing by the plating conditions shown in Figs. 2 and 7. Furthermore, secondary cooling is performed by the conditions shown in FIG. 2 and Table 7, The mixture was heated again and cooled three times to obtain a hot-dip galvanized steel sheet.

在與壓延方向呈直角的方向中，自所製得熔融鍍鋅鋼板採集JIS5號拉伸試驗片，並進行拉伸試驗，且測定拉伸強度(TS)、總伸長(EL)。遵循日本鋼鐵聯盟規格之「JFS T 1001擴孔試驗方法」，測定擴孔率(λ)。遵循前述方法，識別鋼組織。 A JIS No. 5 tensile test piece was taken from the obtained hot-dip galvanized steel sheet in a direction perpendicular to the rolling direction, and subjected to a tensile test, and tensile strength (TS) and total elongation (EL) were measured. The hole expansion ratio (λ) was measured in accordance with the "JFS T 1001 Reaming Test Method" of the Japan Iron and Steel Federation specifications. The steel structure is identified following the method described above.

自所製得熔融鍍鋅鋼板，採集業已以間隙10%打孔為30mm φ的試驗片，並以最長24小時，將打孔試驗片浸漬於pH1之鹽酸水溶液中。每隔3小時便觀察試驗片之打孔端面，並觀察有無破裂。將即便浸漬12小時後亦未發現破裂者視為合格。 From the obtained hot-dip galvanized steel sheet, a test piece which was punched with a gap of 10% to 30 mm φ was collected, and the punched test piece was immersed in a hydrochloric acid aqueous solution of pH 1 for a maximum of 24 hours. The perforated end faces of the test pieces were observed every 3 hours, and the presence or absence of cracking was observed. Those who did not find cracks even after immersion for 12 hours were regarded as qualified.

表8顯示所獲得之結果。 Table 8 shows the results obtained.

在表8所示的實施例(發明例)中，任一者之化學組成皆位於本發明之範圍內，且鋼組織位於本發明之範圍，因此，可獲得1300MPa以上之拉伸強度、75%以上之降伏比(YR)、良好之抗氫脆性。 In the examples (inventive examples) shown in Table 8, the chemical composition of any of them is within the scope of the present invention, and the steel structure is within the scope of the present invention, so that a tensile strength of 1300 MPa or more, 75% can be obtained. The above fluctuation ratio (YR), good resistance to hydrogen embrittlement.

產業上之可利用性 Industrial availability

本發明可利用在例如與適合於汽車車體或零件的鋼板相關之產業中。 The invention can be utilized in industries such as those associated with steel sheets suitable for automotive bodies or parts.

Claims

一種熔融鍍鋅鋼板，其特徵在於具有以下所示之化學組成：以質量%計，C：0.14~0.3%、Si：0.001~2.0%、Mn：2.0~4.0%、P：0.05%以下、S：0.01%以下、N：0.01%以下、Al：0.001~1.0%、Ti：0.001~0.10%、B：0.0001~0.01%、Mo：0~0.50%、Cr：0~0.80%、Ni：0~1.00%、Cu：0~1.00%、V：0~0.50%、Nb：0.0~0.10%、Ca：0.00~0.01%、Mg：0.00~0.01%、REM：0.00~0.01%、Bi：0.00~0.01%，及剩餘部分：Fe及雜質；並且具有以下所示之鋼組織：以面積率計，多邊形肥粒鐵：10%以下、上部變韌鐵：20%以下、殘留沃斯田鐵：5%以下、麻田散鐵：70%以上、具有個數密度為1×10⁶/mm²以上之Fe碳化物的麻田散鐵：相對於整體麻田散鐵為50%以上，及平均有效結晶粒徑：5.0μm以下；其固溶B量為0.0010質量%~0.0100質量%，舊沃斯田鐵粒徑為1.0μm~7.0μm。 A hot-dip galvanized steel sheet characterized by having the chemical composition shown below: C: 0.14 to 0.3%, Si: 0.001 to 2.0%, Mn: 2.0 to 4.0%, P: 0.05% or less, in mass%, S : 0.01% or less, N: 0.01% or less, Al: 0.001 to 1.0%, Ti: 0.001 to 0.10%, B: 0.0001 to 0.01%, Mo: 0 to 0.50%, Cr: 0 to 0.80%, Ni: 0~ 1.00%, Cu: 0~1.00%, V: 0~0.50%, Nb: 0.0~0.10%, Ca: 0.00~0.01%, Mg: 0.00~0.01%, REM: 0.00~0.01%, Bi: 0.00~0.01 %, and the remainder: Fe and impurities; and have the steel structure shown below: in terms of area ratio, polygonal ferrite iron: 10% or less, upper toughened iron: 20% or less, residual Worthite iron: 5% In the following, Ma Tian loose iron: 70% or more, Ma Tian loose iron having a number of Fe carbides having a density of 1 × 10 ⁶ /mm ² or more: 50% or more with respect to the whole granulated iron, and an average effective crystal grain size: 5.0 μm or less; the amount of solid solution B is 0.0010% by mass to 0.0100% by mass, and the particle size of the old Worthite is 1.0 μm to 7.0 μm.

如請求項1之熔融鍍鋅鋼板，其中固溶B量與舊沃斯田鐵粒徑之積為0.0010質量%．μm以上。 The molten galvanized steel sheet according to claim 1, wherein the product of the amount of solid solution B and the particle size of the old Worthite iron is 0.0010% by mass. More than μm.

如請求項1或2之熔融鍍鋅鋼板，其中前述化學組成中，Mo：0.001~0.50%成立。 The molten galvanized steel sheet according to claim 1 or 2, wherein Mo: 0.001 to 0.50% of the chemical composition is established.

如請求項1或2之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Cr：0.001~0.80%、Ni：0.001~1.00%，或Cu：0.001~1.00%。 The molten galvanized steel sheet according to claim 1 or 2, wherein any of the following or any combination of the above chemical compositions is established: Cr: 0.001 to 0.80%, Ni: 0.001 to 1.00%, or Cu: 0.001 to 1.00%.

如請求項3之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Cr：0.001~0.80%、 Ni：0.001~1.00%，或Cu：0.001~1.00%。 The molten galvanized steel sheet according to claim 3, wherein any of the following or any combination of the foregoing chemical compositions is established: Cr: 0.001 to 0.80%, Ni: 0.001 to 1.00%, or Cu: 0.001 to 1.00%.

如請求項1或2之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等兩者成立：V：0.001~0.50%，或Nb：0.001~0.10%。 The molten galvanized steel sheet according to claim 1 or 2, wherein, in the chemical composition, the following or both are satisfied: V: 0.001 to 0.50%, or Nb: 0.001 to 0.10%.

如請求項3之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等兩者成立：V：0.001~0.50%，或Nb：0.001~0.10%。 The molten galvanized steel sheet according to claim 3, wherein, in the chemical composition, the following or both are established: V: 0.001 to 0.50%, or Nb: 0.001 to 0.10%.

如請求項4之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等兩者成立：V：0.001~0.50%，或Nb：0.001~0.10%。 The molten galvanized steel sheet according to claim 4, wherein, in the chemical composition, the following or both are established: V: 0.001 to 0.50%, or Nb: 0.001 to 0.10%.

如請求項5之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等兩者成立：V：0.001~0.50%，或Nb：0.001~0.10%。 The molten galvanized steel sheet according to claim 5, wherein, in the chemical composition, the following or both are established: V: 0.001 to 0.50%, or Nb: 0.001 to 0.10%.

如請求項1或2之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Ca：0.0001~0.01%、Mg：0.0001~0.01%、REM：0.0001~0.01%，或Bi：0.0001~0.01%。 The molten galvanized steel sheet according to claim 1 or 2, wherein any of the following or any combination of the foregoing chemical compositions is established: Ca: 0.0001 to 0.01%, Mg: 0.0001 to 0.01%, REM: 0.0001 to 0.01%, or Bi: 0.0001 to 0.01%.

如請求項3之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Ca：0.0001~0.01%、Mg：0.0001~0.01%、REM：0.0001~0.01%，或Bi：0.0001~0.01%。 The molten galvanized steel sheet according to claim 3, wherein any of the following or any combination of the above chemical compositions is established: Ca: 0.0001 to 0.01%, Mg: 0.0001 to 0.01%, REM: 0.0001 to 0.01%, or Bi: 0.0001~0.01%.

如請求項4之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Ca：0.0001~0.01%、Mg：0.0001~0.01%、REM：0.0001~0.01%，或Bi：0.0001~0.01%。 The molten galvanized steel sheet according to claim 4, wherein any of the following or any combination of the above chemical compositions is established: Ca: 0.0001 to 0.01%, Mg: 0.0001 to 0.01%, REM: 0.0001 to 0.01%, or Bi: 0.0001~0.01%.

如請求項5之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Ca：0.0001~0.01%、Mg：0.0001~0.01%、REM：0.0001~0.01%，或Bi：0.0001~0.01%。 The molten galvanized steel sheet according to claim 5, wherein any of the following or any combination of the above chemical compositions is established: Ca: 0.0001 to 0.01%, Mg: 0.0001 to 0.01%, REM: 0.0001 to 0.01%, or Bi: 0.0001~0.01%.

如請求項6之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Ca：0.0001~0.01%、Mg：0.0001~0.01%、REM：0.0001~0.01%，或Bi：0.0001~0.01%。 The hot-dip galvanized steel sheet according to claim 6, wherein any of the following or any combination of the above chemical compositions is established: Ca: 0.0001 to 0.01%, Mg: 0.0001 to 0.01%, REM: 0.0001 to 0.01%, or Bi: 0.0001~0.01%.

如請求項7之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Ca：0.0001~0.01%、Mg：0.0001~0.01%、REM：0.0001~0.01%，或Bi：0.0001~0.01%。 The hot-dip galvanized steel sheet according to claim 7, wherein any of the following or any combination of the above chemical compositions is established: Ca: 0.0001 to 0.01%, Mg: 0.0001 to 0.01%, REM: 0.0001 to 0.01%, or Bi: 0.0001~0.01%.

如請求項8之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Ca：0.0001~0.01%、Mg：0.0001~0.01%、REM：0.0001~0.01%，或Bi：0.0001~0.01%。 The molten galvanized steel sheet according to claim 8, wherein any of the following or any combination of the foregoing chemical compositions is established: Ca: 0.0001 to 0.01%, Mg: 0.0001 to 0.01%, REM: 0.0001 to 0.01%, or Bi: 0.0001~0.01%.

如請求項9之熔融鍍鋅鋼板，其中前述化學組成中，下述或該等之任意組合成立：Ca：0.0001~0.01%、Mg：0.0001~0.01%、REM：0.0001~0.01%，或Bi：0.0001~0.01%。 The molten galvanized steel sheet according to claim 9, wherein any of the following or any combination of the above chemical compositions is established: Ca: 0.0001 to 0.01%, Mg: 0.0001 to 0.01%, REM: 0.0001 to 0.01%, or Bi: 0.0001~0.01%.