TWI671409B - Steel plate and method of manufacturing same - Google Patents
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Abstract
本發明提供板厚中心部之收縮特性優異之高Mn鋼板。 該鋼板含有C：0.20%以上0.70%以下，Si：0.05%以上1.0%以下，Mn：15%以上35%以下，Al：0.1%以下，Cr：8.0%以下，N：0.0010%以上0.0500%以下，P：0.03%以下及S：0.005%以下，且其餘部分為Fe及不可避免雜質之成分組成，拉伸強度為600MPa以上且於-196℃之吸收能為27J以上進而板厚方向之收縮值為30%以上。The present invention provides a high-Mn steel sheet having excellent shrinkage characteristics at the center of the plate thickness. The steel sheet contains C: 0.20% or more and 0.70% or less, Si: 0.05% or more and 1.0% or less, Mn: 15% or more and 35% or less, Al: 0.1% or less, Cr: 8.0% or less, and N: 0.0010% or more and 0.0500% or less. , P: 0.03% or less and S: 0.005% or less, and the rest is composed of Fe and unavoidable impurities, the tensile strength is 600MPa or more, and the absorption energy at -196 ° C is 27J or more and the shrinkage value in the thickness direction More than 30%.
Description
本發明有關可較好地供於液化氣體儲槽用槽等之在極低溫環境使用之構造用鋼，尤其是板厚中心部特性優異之鋼板及其製造方法。The present invention relates to a structural steel which can be suitably used in a tank for a liquefied gas storage tank and the like in an extremely low temperature environment, particularly a steel plate having excellent properties at a center portion of a plate thickness and a method for manufacturing the same.
液化氣體儲存槽用槽等之構造物，由於其使用環境成為極低溫，故於該構造物使用熱軋鋼板時，不僅要求該鋼板之強度優異，亦要求在極低溫之韌性優異。例如，液化天然氣之儲槽所用之熱軋鋼板有必要確保在比液化天然氣之沸點即-164℃更低溫度區域下之優異韌性。極低溫儲存槽用構造物所用之鋼板的低溫韌性較差時，由於有無法維持作為該極低溫儲存槽用構造物之安全性之虞，故對於所適用之鋼板強烈要求低溫韌性之提高。Since structures such as tanks for liquefied gas storage tanks are used at extremely low temperatures, when using hot-rolled steel plates for the structures, not only the strength of the steel plate is required, but also the toughness at extremely low temperatures is required. For example, it is necessary for hot-rolled steel plates used in LNG storage tanks to ensure excellent toughness in a lower temperature region than the boiling point of LNG, which is -164 ° C. When the low-temperature toughness of the steel plate used in the structure for an extremely low-temperature storage tank is poor, there is a risk that the safety as the structure for the ultra-low-temperature storage tank cannot be maintained, and therefore, an improvement in low-temperature toughness is strongly required for the applied steel plate.
對於此要求，以往係使用具有在極低溫未顯示脆性之奧氏體(austenite)組織之奧斯體系不鏽鋼鋼板或9%Ni鋼板、或5000系鋁合金。然而，上述金屬材料由於合金成本或製造成本高，故對於便宜且極低溫韌性優異之鋼板有需求。因此，作為替代以往之極低溫用鋼的新鋼板，已檢討大量添加比較便宜之奧氏體安定化元素即Mn而作成奧氏體組織，將高Mn鋼適用作為極低溫環境之構造用鋼板。To meet this requirement, an Austenitic stainless steel plate or an 9% Ni steel plate or a 5000-series aluminum alloy having an austenite structure that does not show brittleness at extremely low temperatures has been conventionally used. However, since the above-mentioned metal materials have a high alloy cost or manufacturing cost, there is a demand for a steel sheet that is inexpensive and excellent in extremely low-temperature toughness. Therefore, as a new steel plate that replaces the conventional steel for extremely low temperature, a lot of Mn, which is a relatively inexpensive austenite stabilization element, has been added to form an austenite structure, and high-Mn steel has been applied as a steel plate for extremely low temperature environment.
例如，專利文獻1中，揭示藉由添加Mn 15~ 35%、Cu：5%以下，進而適量添加C與Cr，而被削性及熔熱熱影響部之於-196℃的夏比衝擊特性經改善的鋼材。For example, Patent Document 1 discloses a Charpy impact characteristic at -196 ° C of machinability and heat-melting heat-affected zone by adding Mn 15 to 35% and Cu: 5% or less and further adding C and Cr in appropriate amounts. Improved steel.
又，專利文獻2中揭示添加C：0.25~0.75%，Si：0.05~1.0%，Mn：超過20%且35%以下，Ni：0.1%以上且未達7.0%，Cr：0.1%以上且未達8.0%之低溫韌性經改善之高Mn鋼材。In addition, Patent Document 2 discloses the addition of C: 0.25 to 0.75%, Si: 0.05 to 1.0%, Mn: more than 20% and 35% or less, Ni: 0.1% or more and less than 7.0%, and Cr: 0.1% or more and not more. High Mn steel with improved low temperature toughness up to 8.0%.
進而，專利文獻3中揭示含有C：0.001~ 0.80%，Mn：15~35%，且藉由添加Cr、Ti、Si、Al、Mg、Ca、REM之元素，而改善了母材及熔接部之極低溫韌性及之高Mn鋼材。 [先前技術文獻] [專利文獻]Furthermore, Patent Document 3 discloses that C: 0.001 to 0.80% and Mn: 15 to 35% are added. By adding elements of Cr, Ti, Si, Al, Mg, Ca, and REM, the base material and welded portion are improved. Extremely low temperature toughness and high Mn steel. [Prior Art Literature] [Patent Literature]
專利文獻1：日本特表2015-508452號公報 專利文獻2：日本特開2016-84529號公報 專利文獻3：日本特開2016-196703號公報Patent Document 1: Japanese Patent Publication No. 2015-508452 Patent Document 2: Japanese Patent Publication No. 2016-84529 Patent Document 3: Japanese Patent Publication No. 2016-196703
[發明欲解決之課題][Questions to be Solved by the Invention]
高Mn鋼由於與一般碳鋼相比為高合金，故熔點低，而且熔點附近之黏性高，因此與碳鋼相比，有容易產生粗大鑄造缺陷之特徵。因此，製品中若殘存鑄造缺陷，則以十字接頭等而於鋼板的板厚方向作用拉伸應力時，有於製品產生斷裂導致構造物崩壞之虞。Compared with carbon steel, high Mn steel is a high alloy, so it has a low melting point and high viscosity near the melting point. Therefore, compared with carbon steel, it has the characteristics of being prone to coarse casting defects. Therefore, if casting defects remain in the product, when tensile stress is applied to the plate thickness direction of the steel plate by a cross joint or the like, there is a possibility that the product may break and the structure may collapse.
然而，專利文獻1、2及3所記載之鋼材，並未提及基於為了達成強度及低溫韌性之製造成本的觀點及上述之奧氏體鋼材使用時之構造物的安全性之觀點而變的重要的板厚中心部的收縮特性，尚有檢討餘地。However, the steel materials described in Patent Documents 1, 2, and 3 do not mention changes made based on the viewpoint of the manufacturing cost for achieving strength and low-temperature toughness, and the viewpoint of the safety of the structure when the above-mentioned austenitic steel is used. There is still room for review of the shrinkage characteristics of the important plate thickness center.
本發明係鑒於該問題，目的在於提供板厚中心部之收縮特性優異之高Mn鋼板。 [用以解決課題之手段]The present invention is made in view of this problem, and an object thereof is to provide a high-Mn steel sheet having excellent shrinkage characteristics at the center portion of the plate thickness. [Means to solve the problem]
本發明人等為解決上述課題，以高Mn鋼為對象，關於鋼板之成分組成或製造方法等進行積極研究，最終獲得以下見解。 (i)藉由以高Mn鋼為基礎，將S含量抑制於0.005%以下，可減低MnS之生成量，並改善板厚方向之拉伸特性。 (ii)進而，於加工熱軋中，藉由以壓下比3以上進行軋製，而使鑄造缺陷無害化，且於最終3次中之至少2次中，將每1次之壓下率設為10%以上，而實現鋼板全體之整粒化，抑制異常粗大粒之殘存，可改善板厚方向之拉伸特性。In order to solve the above-mentioned problems, the present inventors made active research on the component composition, manufacturing method, and the like of high-Mn steel, and finally obtained the following findings. (I) By suppressing the S content to less than 0.005% based on high Mn steel, the amount of MnS can be reduced and the tensile properties in the thickness direction can be improved. (ii) Further, in the process of hot rolling, rolling is performed at a reduction ratio of 3 or more to make the casting defects harmless, and at least 2 of the final 3 times, the reduction ratio of each time is reduced. When it is set to 10% or more, the entire steel sheet can be granulated, the residual of abnormally coarse grains can be suppressed, and the tensile properties in the thickness direction can be improved.
本發明係基於以上見解加以進一步檢討而完成者，其要點如下。 1. 一種鋼板，其以質量%計，含有 C：0.20%以上0.70%以下， Si：0.05%以上1.0%以下， Mn：15%以上35%以下， Al：0.1%以下， Cr：8.0%以下， N：0.0010%以上0.0500%以下， P：0.03%以下及 S：0.005%以下， 且具有其餘部分為Fe及不可避免雜質之成分組成，拉伸強度為600MPa以上且於-196℃之吸收能為27J以上進而板厚方向之收縮值為30%以上。The present invention has been completed based on the above findings and further review. The main points are as follows. 1. A steel sheet, in terms of mass%, containing C: 0.20% to 0.70%, Si: 0.05% to 1.0%, Mn: 15% to 35%, Al: 0.1% or less, Cr: 8.0% or less , N: 0.0010% or more and 0.0500% or less, P: 0.03% or less and S: 0.005% or less, and has the composition of the rest of Fe and unavoidable impurities, tensile strength of 600MPa or more and absorption energy at -196 ° C It is 27 J or more and the shrinkage value in a thickness direction is 30% or more.
此處，板厚方向之收縮值可藉由根據JIS Z3199之試驗而測定。Here, the shrinkage value in the thickness direction can be measured by a test according to JIS Z3199.
2. 如前述1之鋼板，其中前述成分組成進而以質量%計含有選自下述之1種或2種以上： Nb：0.003%以上0.030%以下， V：0.01%以上0.10%以下， Ti：0.003%以上0.040%以下及 B：0.0003%以上0.0100%以下。2. The steel sheet according to the above 1, wherein the aforementioned component composition further comprises, by mass%, one or more selected from the following: Nb: 0.003% or more and 0.030% or less, V: 0.01% or more and 0.10% or less, and Ti: 0.003% or more and 0.040% or less and B: 0.0003% or more and 0.0100% or less.
3. 如前述1或2之鋼板，其中前述成分組成進而以質量%計含有選自下述之1種或2種以上： Cu：0.01%以上0.70%以下， Ni：0.01%以上0.50%以下， Sn：0.01%以上0.30%以下， Sb：0.01%以上0.30%以下， Mo：0.05%以上2.0%以下及 W：0.05%以上2.0%以下。3. The steel sheet according to 1 or 2 above, wherein the aforementioned component composition further comprises, by mass%, one or more selected from the following: Cu: 0.01% or more and 0.70% or less, Ni: 0.01% or more and 0.50% or less, Sn: 0.01% to 0.30%, Sb: 0.01% to 0.30%, Mo: 0.05% to 2.0%, and W: 0.05% to 2.0%.
4. 如前述1、2或3之鋼板，其中前述成分組成進而以質量%計含有選自下述之1種或2種以上： Ca：0.0005%以上0.0050%以下， Mg：0.0005%以上0.0100%以下及 REM：0.0010%以上0.0200%以下。4. The steel sheet according to the above 1, 2 or 3, wherein the aforementioned component composition further comprises, by mass%, one or more selected from the following: Ca: 0.0005% or more and 0.0050% or less, Mg: 0.0005% or more and 0.0100% or more Below and REM: 0.0010% or more and 0.0200% or less.
5. 一種鋼板之製造方法，其係製造如前述1至4中任一項之鋼板，且將鋼材加熱至1000℃以上1300℃以下後，以壓下比：3以上且最終3次中之至少2次之壓下率為每1次10%以上進行熱軋。 [發明效果]5. A method for manufacturing a steel plate, which comprises manufacturing the steel plate according to any one of the foregoing 1 to 4, and heating the steel material to a temperature of 1000 ° C or more and 1300 ° C or less, and at a reduction ratio of 3 or more and at least 3 times in the end Hot rolling was performed at a rolling reduction of 10% or more per time. [Inventive effect]
依據本發明，可提供板厚中心部之收縮特性優異之鋼板。而且，本發明之鋼板若適用於液化氣體儲存槽用槽等之在極低溫環境下使用之鋼構造物，則大有助於該構造物之安全性提高，帶來產業上格外之效果。且，與既有材料相比由於較便宜，故亦具有經濟性優異之優點。According to the present invention, it is possible to provide a steel plate having excellent shrinkage characteristics at the center portion of the plate thickness. In addition, if the steel sheet of the present invention is applied to a steel structure used in an extremely low temperature environment, such as a tank for a liquefied gas storage tank, it will greatly contribute to the improvement of the safety of the structure and bring an industrially extraordinary effect. In addition, it is cheaper than existing materials, so it has the advantage of excellent economy.
以下，針對本發明之鋼板具體加以說明。又，本發明不限定於以下實施形態。 [成分組成] 首先，針對本發明鋼板之成分組成及其限定理由加以說明。又，表示成分組成之「%」只要未特別限定，則意指「質量%」。Hereinafter, the steel sheet of the present invention will be specifically described. The present invention is not limited to the following embodiments. [Component composition] (1) First, the component composition of the steel sheet of the present invention and the reasons for its limitation will be described. In addition, "%" showing an ingredient composition means "mass%" as long as it is not specifically limited.
C：0.20%以上0.70%以下 C對於高強度化有效，進而係便宜的奧氏體安定化元素，且係用以獲得奧氏體組織之重要元素。為了獲得該效果，C有必要含有0.20%以上。另一方面，若含有超過0.70%，則會偏析於板厚中心部，由於促進Cr碳化物及Nb、V、Ti系碳化物之過度析出，故使低溫韌性降低並且使收縮值降低。因此，C設為0.20%以上0.70%以下。較好設為0.25%以上0.60%以下。C: 0.20% or more and 0.70% or less C is effective for high strength and is an inexpensive austenite stabilizing element. It is also an important element for obtaining an austenite structure. In order to obtain this effect, it is necessary to contain C in an amount of 0.20% or more. On the other hand, if it contains more than 0.70%, it will segregate at the center of the plate thickness and promote excessive precipitation of Cr carbides and Nb, V, and Ti-based carbides, thereby lowering the low-temperature toughness and reducing the shrinkage value. Therefore, C is set to be 0.20% or more and 0.70% or less. It is preferably at least 0.25% and at most 0.60%.
Si：0.05%以上1.0%以下 Si係作為脫氧材發揮作用，不僅為製鋼上必要，而且藉由固熔於鋼而固熔強化，具有使鋼板高強度化之效果。為了獲得此等效果，Si必須含有0.05%以上。另一方面，若含有超過1.0%，則熔接性及表面性狀劣化。因此，將Si設為0.05%以上1.0%以下。較好設為0.07%以上0.5%以下。Si: 0.05% or more and 1.0% or less Si is used as a deoxidizing material. It is not only necessary for steel making, but also solidified and strengthened by solid solution in steel, which has the effect of increasing the strength of steel plates. In order to obtain these effects, Si must be contained in an amount of 0.05% or more. On the other hand, when the content exceeds 1.0%, the weldability and surface properties are deteriorated. Therefore, Si is set to 0.05% to 1.0%. It is preferably at least 0.07% and at most 0.5%.
Mn：15%以上35%以下 Mn係比較便宜的奧氏體安定化元素。本發明中，係用以兼具強度與極低溫韌性的重要元素。為了獲得其效果，Mn必須含有15%以上。另一方面，含有超過35%時，改善極低溫韌性之效果飽和，導致合金成本上升。且，熔接性、切斷性劣化。再者，助長偏析，引起極低溫韌性之降低或板厚方向拉伸特性之劣化、發生應力腐蝕龜裂。因此，Mn設為15%以上35%以下。較好設為18%以上28%以下之範圍。Mn: 15% to 35% Mn is a relatively inexpensive austenite stabilizing element. In the present invention, it is an important element used to have both strength and extremely low temperature toughness. In order to obtain this effect, Mn must be contained in an amount of 15% or more. On the other hand, when the content exceeds 35%, the effect of improving the low-temperature toughness is saturated, which leads to an increase in the cost of the alloy. In addition, the weldability and cutting properties are deteriorated. In addition, it promotes segregation, causes a decrease in the extremely low temperature toughness, a deterioration in the tensile properties in the thickness direction, and causes stress corrosion cracking. Therefore, Mn is set to 15% to 35%. The range is preferably 18% to 28%.
Al：0.1%以下 Al係作為脫氧劑發揮作用，於鋼板之熔鋼脫氧製程中，最常廣泛使用。且，將鋼中之固熔N固定，形成AlN而具有抑制因固熔N減低所致之韌性劣化的效果。因此，較好以0.01%以上含有。另一方面，Al含有超過0.1%時，由於熔接時擴散於熔接金屬部，使熔接金屬之韌性劣化，故設為0.1%以下。較好設為0.07%以下。更好設為0.02%以上0.06%以下。Al: 0.1% or less Al is used as a deoxidizer and is most commonly used in the process of deoxidizing molten steel of steel plates. In addition, fixing the solid solution N in the steel to form AlN has the effect of suppressing the deterioration of toughness due to the decrease of the solid solution N. Therefore, it is preferably contained at 0.01% or more. On the other hand, when the Al content exceeds 0.1%, it diffuses into the weld metal portion during welding and deteriorates the toughness of the weld metal, so it is set to 0.1% or less. It is more preferably 0.07% or less. It is more preferably at least 0.02% and at most 0.06%.
Cr：8.0%以下 Cr係高Mn鋼的低溫韌性及耐腐蝕性提高所必要之元素。另一方面Cr於軋製中有以氮化物、碳化物、碳氮化物等之形態析出之情況，由於因該等析出物之形成而成為腐蝕或破壞之起點而使低溫韌性降低，故將上限設為8.0%。較好Cr量設為1.0%以上6.0%以下，更好為1.5%以上5.5%以下之範圍。Cr: 8.0% or less Cr is an element necessary for improving the low-temperature toughness and corrosion resistance of high-Mn steel. On the other hand, Cr may be precipitated in the form of nitrides, carbides, carbonitrides, etc. during rolling. The low-temperature toughness is lowered because the formation of these precipitates becomes the starting point of corrosion or damage, so the upper limit is set. Set it to 8.0%. The amount of Cr is preferably in the range of 1.0% to 6.0%, more preferably in the range of 1.5% to 5.5%.
N：0.0010%以上0.0500%以下 N係奧氏體安定化元素，係提高極低溫韌性之有效元素。且具有與Nb、V及Ti結合而作為氮化物或碳氮化物微細析出，作為擴散性氫之捕獲部位而抑制應力腐蝕龜裂之效果。為了獲得此等效果，N有必要含有0.0010%以上。另一方面，若含有超過0.0500%，則促進過量氮化物或碳氮化物之生成，不僅使固熔元素量降低且耐腐蝕性降低，亦使韌性降低。因此，N設為0.0010%以上0.0500%以下。較好N量設為0.0020%以上0.0200%以下。N: 0.0010% or more and 0.0500% or less N is an austenite stabilizing element, and is an effective element for improving the extremely low temperature toughness. In addition, it has the effect of suppressing stress corrosion cracking by combining with Nb, V, and Ti to precipitate finely as nitrides or carbonitrides, and as a trapping site for diffusible hydrogen. In order to obtain these effects, N must be contained in an amount of 0.0010% or more. On the other hand, if the content exceeds 0.0500%, the formation of excessive nitrides or carbonitrides is promoted, which not only reduces the amount of solid-solution elements and the corrosion resistance, but also decreases the toughness. Therefore, N is set to be 0.0010% or more and 0.0500% or less. The N content is preferably 0.0020% or more and 0.0200% or less.
P：0.03%以下 P若含有超過0.03%，則有偏析於粒界使粒界強度降低，成為破壞起點之情況。因此，將0.03%設為上限，期望儘可能減低。因此，P設為0.03%以下。由於P越少則特性越提高，故較好設為0.025%以下，更好設為0.020%以下。又，於抑制至未達0.0005%時，由於需要相當大的製鋼成本，故基於經濟性之觀點較好設為0.0005%以上。P: 0.03% or less When P is contained in excess of 0.03%, segregation at the grain boundary may reduce the strength of the grain boundary, and may become the starting point of failure. Therefore, 0.03% is set as an upper limit, and it is desirable to reduce it as much as possible. Therefore, P is set to 0.03% or less. The smaller the P content, the better the characteristics. Therefore, it is preferably set to 0.025% or less, and more preferably 0.020% or less. Moreover, when it is suppressed to less than 0.0005%, since considerable steelmaking cost is required, it is preferable to set it as 0.0005% or more from the viewpoint of economy.
S：0.005%以下 S由於於鋼中形成MnS使低溫韌性及鋼板方向拉伸時之收縮顯著劣化，故將0.005%設為上限，期望儘可能減低。較好設為0.002%以下。又，於抑制至未達0.0001%時，由於需要相當大的製鋼成本，故基於經濟性之觀點較好設為0.0001%以上。S: 0.005% or less S forms MnS in the steel, which significantly deteriorates the low-temperature toughness and shrinkage when the steel sheet is stretched in the direction of the steel. Therefore, 0.005% is set as the upper limit, and it is desirable to reduce it as much as possible. The content is preferably 0.002% or less. In addition, when it is suppressed to less than 0.0001%, a considerable steel-making cost is required, so it is preferably set to 0.0001% or more from the viewpoint of economy.
上述成分以外之其餘部分係Fe及不可避免之雜質。作為不可避免雜質有Zr、As等。The remainder other than the above components are Fe and inevitable impurities. Examples of unavoidable impurities include Zr and As.
本發明中，以進一步提高強度及低溫韌性為目的，除上述必須元素以外，可根據需要含有下述元素。 Nb：0.003%以上0.030%以下 Nb係提高鋼板強度之有效元素。為了獲得此等效果，較好以0.003%以上添加Nb。另一方面，含有超過0.030%時，有粗化碳氮化物析出，成為破壞起點而使板厚方向之拉伸特性劣化之情況。且，有使析出物粗大化，母材韌性劣化之情況。因此，含有Nb時，較好設為0.003%以上0.030%以下。更好設為0.005%以上，又更好設為0.007%以上。同樣地，更好設為0.025%以下，又更好設為0.022%以下。In the present invention, for the purpose of further improving strength and low-temperature toughness, in addition to the above-mentioned essential elements, the following elements may be contained as necessary. Nb: 0.003% or more and 0.030% or less Nb is an effective element for improving the strength of steel plates. In order to obtain these effects, it is preferable to add Nb at 0.003% or more. On the other hand, when the content exceeds 0.030%, roughened carbonitrides may be precipitated, which may become the starting point of failure, and the tensile properties in the thickness direction may be deteriorated. In addition, the precipitate may be coarsened and the toughness of the base material may be deteriorated. Therefore, when Nb is contained, it is preferably set to 0.003% or more and 0.030% or less. It is more preferably 0.005% or more, and still more preferably 0.007% or more. Similarly, it is more preferably set to 0.025% or less, and more preferably set to 0.022% or less.
V：0.01%以上0.10%以下 V係提高鋼板強度之有效元素。為了獲得此等效果，較好以0.01%以上含有V。另一方面，含有超過0.10%時，有粗化碳氮化物析出，成為破壞起點之情況。且，有使析出物粗大化，母材韌性劣化之情況。因此，含有V時，較好設為0.01%以上0.10%以下。更好設為0.02%以上，又更好設為0.03%以上。同樣地，更好設為0.09%以下，又更好設為0.08%以下。V: 0.01% or more and 0.10% or less V is an effective element for improving the strength of steel plates. In order to obtain these effects, V is preferably contained in an amount of 0.01% or more. On the other hand, when the content exceeds 0.10%, roughened carbonitrides may be precipitated and become the starting point of failure. In addition, the precipitate may be coarsened and the toughness of the base material may be deteriorated. Therefore, when V is contained, it is preferably set to 0.01% or more and 0.10% or less. It is more preferably set to be 0.02% or more, and more preferably set to be 0.03% or more. Similarly, it is more preferably 0.09% or less, and still more preferably 0.08% or less.
Ti：0.003%以上0.040%以下 Ti係作為氮化物或碳氮化物析出，提高鋼板強度之有效元素。為了獲得此等效果，較好以0.003%以上含有Ti。另一方面，含有超過0.040%時，有使析出物粗大化，母材韌性劣化之情況。又，有粗化碳氮化物析出，成為破壞起點之情況。因此，含有Ti時，較好設為0.003%以上0.040%以下。更好設為0.005%以上，又更好設為0.007%以上。同樣地，更好設為0.035%以下，又更好設為0.032%以下。Ti: 0.003% or more and 0.040% or less Ti is an effective element that precipitates as a nitride or a carbonitride to improve the strength of the steel sheet. In order to obtain these effects, Ti is preferably contained in an amount of 0.003% or more. On the other hand, when the content exceeds 0.040%, the precipitates are coarsened, and the toughness of the base material may be deteriorated. In addition, roughened carbonitrides may precipitate and become the starting point of destruction. Therefore, when Ti is contained, it is preferably set to 0.003% or more and 0.040% or less. It is more preferably 0.005% or more, and still more preferably 0.007% or more. Similarly, it is more preferably 0.035% or less, and still more preferably 0.032% or less.
B：0.0003%以上0.0100%以下。 B係提高奧氏體粒界強度之元素，係提高極低溫韌性之有效元素。為了獲得此等效果，較好以0.0003%以上含有B。另一方面，含有超過0.0100%時，會生成粗大之B析出物，使韌性降低。因此，較好將B設為0.0100%以下之範圍。更好設為0.0030%以下。B: 0.0003% or more and 0.0100% or less. B is an element that enhances the austenite grain boundary strength, and is an effective element that improves the extremely low temperature toughness. In order to obtain these effects, B is preferably contained in an amount of 0.0003% or more. On the other hand, if the content exceeds 0.0100%, coarse B precipitates are formed, and toughness is reduced. Therefore, B is preferably set to a range of 0.0100% or less. It is more preferably 0.0030% or less.
再者，本發明可根據需要含有下述元素。 Cu：0.01%以上0.70%以下，Ni：0.01%以上0.50%以下，Sn：0.01%以上0.30%以下，Sb：0.01%以上0.30%以下，Mo：0.05%以上2.0%以下，W：0.05%以上2.0%以下之1種或2種以上。The present invention may contain the following elements as necessary. Cu: 0.01% or more and 0.70% or less, Ni: 0.01% or more and 0.50% or less, Sn: 0.01% or more and 0.30% or less, Sb: 0.01% or more and 0.30% or less, Mo: 0.05% or more and 2.0% or less, and W: 0.05% or more One or more than 2.0%.
Cu、Ni、Sn、Sb、Mo及W係藉由與Cr複合添加，而提高高Mn鋼的耐腐蝕性之元素。 該效果於高Mn鋼中，上述任一元素與Cr共存時明顯化，於各自之上述下限值以上得以顯現。然而，任一元素均係超過上述上限值而較多含有時，會使熔接性或韌性劣化，且就成本觀點亦不利。Cu, Ni, Sn, Sb, Mo, and W are elements that are added in combination with Cr to improve the corrosion resistance of high-Mn steel. This effect is noticeable in high Mn steel when any of the above elements coexist with Cr, and appears above the respective lower limit values. However, if any element is contained in excess of the above upper limit, the weldability and toughness are deteriorated, and the cost is disadvantageous.
因此，Cu、Ni、Sn、Sb、Mo及W較好以上述範圍添加。更好Cu量為0.02%以上0.50%以下，Ni量為0.02%以上0.40%以下，Sn量為0.02%以上0.25%以下，Sb量為0.02%以上0.25%以下，Mo量為0.05%以上1.50%以下，W量為0.05%以上1.50%以下。Therefore, Cu, Ni, Sn, Sb, Mo, and W are preferably added in the above range. More preferably, the amount of Cu is 0.02% to 0.50%, the amount of Ni is 0.02% to 0.40%, the amount of Sn is 0.02% to 0.25%, the amount of Sb is 0.02% to 0.25%, and the amount of Mo is 0.05% to 1.50%. Hereinafter, the amount of W is 0.05% to 1.50%.
又再者，本發明中可根據需要含有下述元素。 Ca：0.0005%以上0.0050%以下，Mg：0.0005%以上0.0100%以下，REM：0.0010%以上0.0200%以下之1種或2種以上。Furthermore, the following elements may be contained in this invention as needed. Ca: 0.0005% or more and 0.0050% or less, Mg: 0.0005% or more and 0.0100% or less, and REM: 0.0010% or more and 0.0200% or less.
Ca、Mg及REM係控制MnS等之介隔物的形態上有用的元素，可根據需要含有。此處，所謂控制介隔物的形態，係指使經伸展的硫化物系介隔物作成粒狀介隔物。經由控制該介隔物之形態，可提高板厚方向之拉伸特性、韌性及耐硫化物應力腐蝕龜裂性。為了獲得此等效果，較好Ca及Mg含有0.0005%以上，REM含有0.0010%以上。Ca, Mg, and REM are elements useful for controlling the morphology of a spacer such as MnS, and may be contained as necessary. Here, the control of the form of the spacer means that the stretched sulfide-based spacer is made into a granular spacer. By controlling the morphology of the spacer, the tensile properties in the thickness direction, toughness, and resistance to sulfide stress corrosion cracking can be improved. In order to obtain these effects, it is preferable that Ca and Mg contain 0.0005% or more, and REM contain 0.0010% or more.
另一方面，任一元素以含有較多時，均有使非金屬介隔物量增加，反而使板厚中心部之特性降低之情況。因此，含有Ca時較好設為0.0050%以下，含有Mg時較好設為0.0100%以下，含有REM時較好設為0.0200%以下。更好Ca量設為0.0010%以上0.0040%以下，Mg量設為0.0010%以上0.0040%以下，REM量設為0.0020%以上0.0150%以下。On the other hand, when any element is contained in a large amount, the amount of non-metallic spacers may increase, but the characteristics of the center portion of the plate thickness may decrease. Therefore, when Ca is contained, the content is preferably 0.0050% or less, when Mg is contained, the content is preferably 0.0100% or less, and when REM is contained, the content is preferably 0.0200% or less. The Ca content is more preferably 0.0010% to 0.0040%, the Mg content is 0.0010% to 0.0040%, and the REM content is 0.0020% to 0.0150%.
具有以上成分組成之鋼板，重要的是進而板厚方向之收縮值為30%以上。亦即，其理由為板厚方向之收縮值未達30%時，以例如十字熔接接頭部等發生破壞而顯著損及作為構造物之健全性之故。It is important for a steel sheet having the above composition to further reduce the shrinkage value in the thickness direction by 30% or more. That is, the reason is that when the shrinkage value in the thickness direction does not reach 30%, the cross-welded joint portion or the like is damaged, and the soundness of the structure is significantly damaged.
其次，針對本發明之鋼板的製造方法加以說明。亦即，本發明之鋼板可藉由將具有上述成分組成之鋼材加熱至1000℃以上1300℃以下後，以壓下比：3以上且最終3次中之至少2次之壓下率為每1次10%以上進行熱軋而製造。 又，以下說明中，溫度「℃」意指板厚中心之溫度。Next, the manufacturing method of the steel plate of this invention is demonstrated. That is, the steel sheet of the present invention can be obtained by heating a steel material having the above-mentioned component composition to a temperature of 1000 ° C. or more and 1300 ° C. or less, with a reduction ratio of 3 or more and at least 2 of the final 3 times. Manufactured by hot rolling more than 10%. In the following description, the temperature "° C" means the temperature at the center of the plate thickness.
[鋼材的加熱溫度：1000℃以上1300℃以下] 將鋼材加熱至1000℃以上係謂了使組織中之析出物固熔，使結晶粒徑等均一化，作為加熱溫度設為1000℃以上1300℃以下。加熱溫度未達900℃時，由於析出物未充分固熔故無法獲得期望特性。又，1300℃以上之加熱除了因結晶粒徑之粗大化而使材質劣化以外，由於亦需要過多能量而使生產性降低，故加熱溫度上限設為1300℃。較好設為1050℃以上1250℃以下，更好為設為1100℃以上1250℃以下之範圍。[Heating temperature of steel: 1000 ° C or higher and 1300 ° C or lower] 加热 Heating steel to 1000 ° C or higher refers to solidifying the precipitates in the structure and uniformizing the crystal grain size. The heating temperature is set to 1000 ° C to 1300 ° C. the following. When the heating temperature is less than 900 ° C, the precipitates are not sufficiently solidified, so that desired characteristics cannot be obtained. In addition to heating at 1300 ° C or higher, in addition to the deterioration of the material due to the coarsening of the crystal grain size, too much energy is required to reduce productivity, so the upper limit of the heating temperature is 1300 ° C. The temperature is preferably 1050 ° C or higher and 1250 ° C or lower, and more preferably 1100 ° C or higher and 1250 ° C or lower.
又，作為鋼材，除了連續鑄造鋼板材(slab)以外，亦可使用造塊鋼板材或鋼錠等之以常用方法製造之材料。In addition, as the steel material, in addition to continuous casting of a steel plate (slab), a material produced by a conventional method such as a block steel plate or an ingot can also be used.
[熱軋時之壓下比：3以上] 熱軋之壓下比未達3時，難以藉由鑄造缺陷之壓著而抑制板厚方向之拉伸特性之降低。再者，藉由軋製促進再結晶而實現整粒化亦變不充分，殘存粗大奧氏體粒之結果，使強度及韌性等之特性劣化，因此將壓下比限定於3以上。較好壓下比4以上，更好壓下比5以上。又，壓下比之上限並無必要特別限定，但較好為50以下。其原因為壓下比超過50時，機械特性之異向性顯著變大之故。[Reduction ratio during hot rolling: 3 or more] 时 When the reduction ratio during hot rolling is less than 3, it is difficult to suppress the reduction in tensile properties in the thickness direction by the pressing of casting defects. Furthermore, the recrystallization is promoted by rolling to make the graining insufficient, and the coarse austenite grains remain. As a result, properties such as strength and toughness are deteriorated. Therefore, the reduction ratio is limited to 3 or more. A better reduction ratio is 4 or more, and a better reduction ratio is 5 or more. The upper limit of the reduction ratio is not particularly limited, but it is preferably 50 or less. The reason is that when the reduction ratio exceeds 50, the anisotropy of the mechanical characteristics becomes significantly larger.
此處，所謂熱軋之壓下比係以軋製材之板厚/軋製後之鋼板板厚加以定義。Here, the reduction ratio of hot rolling is defined by the thickness of a rolled material / the thickness of a steel sheet after rolling.
[最終3次中之至少2次之壓下率為每1次10%以上] 最終決定鋼板材質之最終3次中，針對至少2次，藉由將每1次之壓下率設為10%以上，首先可使鑄造缺陷確實無害化，進而因實現鋼板全體之整粒化，而可抑制異常粗大粒之殘存，板厚方向之拉伸試驗的收縮值提高之結果，可確保30%以上之收縮值。[The rolling reduction rate of at least 2 times in the last 3 times is 10% or more per time] The final 3 times of final determination of the steel material, for at least 2 times, the rolling reduction rate of each time is set to 10% In the above, firstly, the casting defects can be truly harmless, and the entire grain of the steel sheet can be achieved, thereby suppressing the residual of abnormally coarse grains. As a result, the shrinkage value of the tensile test in the thickness direction of the steel sheet can be increased, which can ensure more than 30% Shrink value.
亦即，理由為限制最終3次中之至少2次之壓下率，可確實壓著鑄造缺陷之故。因此，較好最終3次之全部每次的壓下率各設為10%以上。另一方面，最終3次中之至少2次之壓下率未達10%時，殘存鑄造缺陷且板厚中心部之收縮值降低。又，壓下率上限並無必要特別限定，但基於軋製荷重等之設備限制較好設為30%。That is, the reason is to limit the reduction ratio of at least two of the last three times, and it is possible to surely suppress the casting defect. Therefore, it is preferable to set the rolling reduction rate of each of the last three times to 10% or more. On the other hand, when the reduction ratio of at least two of the last three times is less than 10%, the casting defects remain and the shrinkage value of the center of the plate thickness decreases. The upper limit of the reduction ratio is not particularly limited, but it is preferable to set the equipment limit based on the rolling load to 30%.
[熱軋後之冷卻] 為了獲得鋼板強度及低溫韌性等必要特性，亦可實施熱軋後水冷等。 [實施例][Cooling after Hot Rolling] In order to obtain necessary properties such as strength and low temperature toughness of the steel sheet, water cooling after hot rolling may be performed. [Example]
將表1所示之No.1~26的鋼熔製作成鋼板材後，藉由表2所示之製造條件作成板厚為30~50mm之鋼板。接著將所得試料No.1~30之鋼板供於下述所示之拉伸試驗。該拉伸試驗結果一併記載於表2。After the steels Nos. 1 to 26 shown in Table 1 were melted into a steel plate, a steel plate having a thickness of 30 to 50 mm was produced under the manufacturing conditions shown in Table 2. Next, the obtained steel plates of samples Nos. 1 to 30 were subjected to a tensile test shown below. The results of this tensile test are also shown in Table 2.
板厚方向之拉伸試驗的收縮值係依據JIS G3199進行評價。試驗片形狀係使用A型試驗片。又，自距離鋼板表面之板厚的1/4深度位置(以下稱為1/4t部)採取之圓棒拉伸試驗片之拉伸強度係將使用自1/4t部採取之夏比試驗片於-196℃之夏比吸收能以3片之平均值而評價。The shrinkage value of the tensile test in the thickness direction was evaluated in accordance with JIS G3199. The shape of the test piece was a type A test piece. In addition, the tensile strength of a round bar tensile test piece taken from a 1/4 depth position (hereinafter referred to as a 1 / 4t portion) from the thickness of the steel plate surface is a Charpy test piece taken from a 1 / 4t portion The Charpy absorption energy at -196 ° C was evaluated as an average of 3 tablets.
與本發明一致之本發明例(試料No.1~14)確認滿足收縮為30%以上。另一方面，偏離本發明範圍之比較例(試料No.15~30)係拉伸強度、吸收能及收縮之任一者以上在本發明之申請專利範圍以外，無法滿足上述目標性能。Examples of the present invention (Sample Nos. 1 to 14) consistent with the present invention confirmed that the shrinkage was satisfied to be 30% or more. On the other hand, the comparative examples (Sample Nos. 15 to 30) that deviate from the scope of the present invention are any one of tensile strength, absorbent energy, and shrinkage, which are outside the scope of the patent application of the present invention and cannot satisfy the above-mentioned target performance.
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| TW202009314A (en) | 2020-03-01 |
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