TWI558821B - High strength hot rolled steel and its manufacturing method - Google Patents
High strength hot rolled steel and its manufacturing method Download PDFInfo
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本發明係關於一種鋼材，特別係關於一種高強度熱軋鋼材及其製造方法。 The present invention relates to a steel material, and more particularly to a high strength hot rolled steel material and a method of manufacturing the same.
傳統熱軋鋼鐵材料的設計觀念是超過60公斤的鋼材，就必須採用麻田散鐵或變韌鐵的設計。然而，由於麻田散鐵或變韌鐵設計的鋼材之加工成形性不佳，因此，無法做為須冷加工成形的汽車用鋼，即使是可加工成形之熱軋雙相鋼，一般也只應用到590MPa。 The design concept of traditional hot-rolled steel materials is more than 60 kg of steel, it must be designed with Ma Tian loose iron or toughened iron. However, due to the poor formability of the steel designed by the granulated iron or the toughened iron, it cannot be used as an automotive steel that needs to be cold-formed. Even the hot-rolled duplex steel that can be formed into a shape is generally applied only to 590 MPa.
一般雙相鋼是靠麻田散鐵的面積比率來達成其強度要求，超過590MPa之雙相鋼的麻田散鐵面積比率可能需超過30%，因此，也會面臨伸長率不足的問題。相對而言，以晶粒微米化及析出物奈米化的冶金設計，無疑為熱軋汽車用鋼朝高強度化發展提供一個很好的方向。 Generally, the dual-phase steel is based on the area ratio of the granulated iron to achieve its strength requirement. The ratio of the granulated iron area of the dual-phase steel exceeding 590 MPa may exceed 30%. Therefore, the problem of insufficient elongation is also encountered. Relatively speaking, the metallurgical design of grain micronization and nanocrystallization of precipitates undoubtedly provides a good direction for the development of high-strength steel for hot-rolled automobiles.
我國公告專利第I373532號「高強度熱軋鋼材及其製法」揭示一種晶粒微米化與析出物奈米化的冶金設計，其係利用Ti-V複合添加的方式製作熱軋鋼材，以提升熱軋鋼材之抗拉強度。惟，晶粒微米化及析出物奈米化之冶金設計所生產之鋼材，具備高降伏比的特性，加上熱軋汽車用鋼主要應用於汽車之安全結構件，其厚度相較於冷軋相對較厚，因此，鋼材之冷加工是一大難題。目前國內業者經常因加工設備能力不足而無法加工780MPa之鋼材。 China's announced patent No. I373532 "High-strength hot-rolled steel and its preparation method" discloses a metallurgical design of grain micronization and nanocrystallization of precipitates, which is made by using Ti-V composite addition method to produce hot-rolled steel to enhance heat. The tensile strength of rolled steel. However, the steel produced by the metallurgical design of grain micronization and precipitate nanocrystallization has high derating ratio characteristics, and the steel for hot rolling automotive is mainly used for safety structural parts of automobiles, and its thickness is compared with that of cold rolling. Relatively thick, therefore, cold working of steel is a big problem. At present, domestic manufacturers are often unable to process 780 MPa of steel due to insufficient processing equipment capacity.
因此，有必要提供一創新且具進步性之高強度熱軋鋼材及其製 造方法，以解決上述問題。 Therefore, it is necessary to provide an innovative and progressive high-strength hot-rolled steel and its system. Create methods to solve the above problems.
本發明提供一種高強度熱軋鋼材，以總重為100wt%計算，包括0.01~0.25wt%的碳、0.50~3.00wt%的錳、0.01~1.20wt%的矽、0.01~0.06wt%的磷、0.0006~0.02wt%的硫、0.1~1.0wt%的鉻、0.03~0.30wt%的鈦、0.0020~0.0150wt%的氮、0.01~0.30wt%的鋁以及平衡量的鐵與不顯著的雜質，該鋼材的顯微結構包含一肥粒鐵相及一低溫變態相，該肥粒鐵相的面積比率為55%以上，而該低溫變態相的面積比率為15至45%。 The invention provides a high-strength hot-rolled steel material, which comprises 0.01-0.25 wt% carbon, 0.50-3.00 wt% manganese, 0.01-1.20 wt% bismuth, 0.01-0.06 wt% phosphorus, based on a total weight of 100 wt%. 0.0006~0.02wt% sulfur, 0.1~1.0wt% chromium, 0.03~0.30wt% titanium, 0.0020~0.0150wt% nitrogen, 0.01~0.30wt% aluminum and balance iron and insignificant impurities The microstructure of the steel material comprises a ferrite iron phase and a low temperature metamorphic phase, the ferrite grain iron phase has an area ratio of 55% or more, and the low temperature metamorphic phase has an area ratio of 15 to 45%.
本發明另提供一種高強度熱軋鋼材之製造方法，包括以下步驟：(a)提供一鋼胚，該鋼胚包括0.01~0.25wt%的碳、0.50~3.00wt%的錳、0.01~1.20wt%的矽、0.01~0.06wt%的磷、0.0006~0.02wt%的硫、0.1~1.0wt%的鉻、0.03~0.30wt%的鈦、0.0020~0.0150wt%的氮、0.01~0.30wt%的鋁以及平衡量的鐵與不顯著的雜質；(b)將該鋼胚加熱至1150℃以上；(c)對加熱後之鋼胚進行一熱軋步驟，並將完軋溫度控制在Ar3溫度以上，以獲得一完軋鋼材；及(d)對該完軋鋼材進行一階段冷卻步驟，以製得高強度熱軋鋼材。 The invention further provides a method for manufacturing a high-strength hot-rolled steel material, comprising the steps of: (a) providing a steel embryo comprising 0.01-0.25 wt% carbon, 0.50-3.00 wt% manganese, 0.01-1.20 wt. % 矽, 0.01~0.06wt% phosphorus, 0.0006~0.02wt% sulfur, 0.1~1.0wt% chromium, 0.03~0.30wt% titanium, 0.0020~0.0150wt% nitrogen, 0.01~0.30wt% Aluminum and a balance of iron and insignificant impurities; (b) heating the steel embryo to above 1150 ° C; (c) performing a hot rolling step on the heated steel slab and controlling the rolling temperature above the Ar3 temperature To obtain a finished steel; and (d) to perform a one-stage cooling step on the finished steel to obtain a high-strength hot-rolled steel.
本發明以奈米析出強化之肥粒鐵相加上面積比率為15至45%之低溫變態相(麻田散鐵或變韌鐵)的設計，可使鋼材具備較低之降伏強度(降伏比<0.75)。此外。由於肥粒鐵相中存在大量的奈米析出物，因此，鋼材之抗拉強度可提升至800MPa以上。 The invention adopts the design of the nano-precipitation-enhanced ferrite-grain iron phase plus the low-temperature metamorphic phase (Mashang loose iron or toughened iron) with an area ratio of 15 to 45%, so that the steel has a lower lodging strength (a ratio of lodging to < 0.75). Also. Since a large amount of nano-precipitates are present in the ferrite phase, the tensile strength of the steel can be increased to 800 MPa or more.
本發明製造方法所製得之高強度熱軋鋼材亦具備相當的拉伸伸長率及較佳之加工硬化率，故鋼材之冷加工成形性亦可大幅提升。 The high-strength hot-rolled steel obtained by the manufacturing method of the present invention also has a relatively high tensile elongation and a good work hardening rate, so that the cold formability of the steel can be greatly improved.
為了能夠更清楚瞭解本發明的技術手段，而可依照說明書的內容予以實施，並且為了讓本發明所述目的、特徵和優點能夠更明顯易懂，以下特舉較佳實施例，並配合附圖，詳細說明如下。 The embodiments of the present invention can be more clearly understood, and the objects, features, and advantages of the present invention will become more apparent. The details are as follows.
S11~S14‧‧‧步驟 S11~S14‧‧‧Steps
圖1顯示本發明高強度熱軋鋼材之製造方法流程圖。 BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing the method of manufacturing the high strength hot rolled steel of the present invention.
本發明提供一種高強度熱軋鋼材，以總重為100wt%計算，包括0.01~0.25wt%的碳、0.50~3.00wt%的錳、0.01~1.20wt%的矽、0.01~0.06wt%的磷、0.0006~0.02wt%的硫、0.1~1.0wt%的鉻、0.03~0.30wt%的鈦、0.0020~0.0150wt%的氮、0.01~0.30wt%的鋁以及平衡量的鐵與不顯著的雜質。 The invention provides a high-strength hot-rolled steel material, which comprises 0.01-0.25 wt% carbon, 0.50-3.00 wt% manganese, 0.01-1.20 wt% bismuth, 0.01-0.06 wt% phosphorus, based on a total weight of 100 wt%. 0.0006~0.02wt% sulfur, 0.1~1.0wt% chromium, 0.03~0.30wt% titanium, 0.0020~0.0150wt% nitrogen, 0.01~0.30wt% aluminum and balance iron and insignificant impurities .
該鋼材的顯微結構包含一肥粒鐵相及一低溫變態相，該低溫變態相係為變韌鐵或麻田散鐵。在本實施例中，該肥粒鐵相的面積比率為55%以上，而該低溫變態相的面積比率為15至45%。較佳地，該肥粒鐵相的粒徑小於20微米，且該肥粒鐵相與該低溫變態相的加總面積比率大於95%。 The microstructure of the steel material comprises a ferrite phase and a low temperature metamorphism phase, and the low temperature metamorphism phase is a toughened iron or a granulated iron. In the present embodiment, the area ratio of the ferrite grain iron phase is 55% or more, and the area ratio of the low temperature metamorphic phase is 15 to 45%. Preferably, the ferrite iron phase has a particle size of less than 20 microns, and the ratio of the total area of the ferrite iron phase to the low temperature metamorphic phase is greater than 95%.
此外，在本實施例中，該高強度熱軋鋼材另具有複數個分散於該肥粒鐵相中的析出物，該等析出物含有碳化物。較佳地，碳化物的粒徑為20奈米以下。 Further, in the present embodiment, the high-strength hot-rolled steel material further has a plurality of precipitates dispersed in the ferrite-grained iron phase, and the precipitates contain carbides. Preferably, the particle size of the carbide is 20 nm or less.
為進一步提升鋼材之抗拉強度，該高強度熱軋鋼材可另包括一合金成份，該合金成份選自0.01~0.10wt%的鈮、0.05~0.50wt%的鉬、0.01~0.60wt%的鎳、0.01~0.80wt%的銅及其彼此組合中的其中一種。 In order to further improve the tensile strength of the steel, the high-strength hot-rolled steel may further comprise an alloy component selected from the group consisting of 0.01 to 0.10 wt% of niobium, 0.05 to 0.50 wt% of molybdenum, and 0.01 to 0.60 wt% of nickel. One of 0.01 to 0.80% by weight of copper and a combination thereof.
上述提及的各種成份分別具有不同的作用，於本發明中，除了碳、錳、矽、磷、硫、鉻、鈦、氮、鋁以及鐵為主要成份之外，其餘成份可依據實際需要進行添加。以下分別針對各種成份及其含量比例對該高強度熱軋鋼材的影響進行說明： The various components mentioned above have different effects. In the present invention, in addition to carbon, manganese, strontium, phosphorus, sulfur, chromium, titanium, nitrogen, aluminum and iron as main components, the remaining components can be carried out according to actual needs. Add to. The following describes the effects of various components and their content ratios on the high-strength hot-rolled steel:
碳：為鋼材中重要的強化元素，且亦是決定奈米析出物與變韌鐵或麻田散鐵的重要元素。當碳含量太低時，析出物與變韌鐵或麻田散鐵均不易生成。當碳含量太高時，則析出物容易粗化，且變韌鐵或麻田散鐵的比率也會太高，進而使得鋼材的伸長率降低。因此，較佳地，碳含量應控制在0.01~0.25wt%。 Carbon: It is an important strengthening element in steel and is also an important element in determining nano-precipitates and toughened iron or granulated iron. When the carbon content is too low, precipitates and toughened iron or granulated iron are not easily formed. When the carbon content is too high, the precipitates are easily coarsened, and the ratio of the toughened iron or the granulated iron is too high, which in turn causes the elongation of the steel to decrease. Therefore, preferably, the carbon content should be controlled to be 0.01 to 0.25 wt%.
錳：為鋼材中重要的固溶強化元素，同時也是促進變韌鐵或麻田散鐵生成的元素，主要用以提高鋼材強度。當錳含量太高時，變韌鐵或麻田散鐵的比率也會太高，致使鋼材的成形性不佳。因此，較佳地，錳含量應控制在0.50~3.00wt%。 Manganese: It is an important solid solution strengthening element in steel. It is also an element that promotes the formation of toughened iron or granulated iron. It is mainly used to increase the strength of steel. When the manganese content is too high, the ratio of the toughened iron or the granulated iron is too high, resulting in poor formability of the steel. Therefore, preferably, the manganese content should be controlled at 0.50 to 3.00% by weight.
氮：為固溶強化元素，且氮與鈦的結合性良好，在超過1400℃以上的高溫就會開始形成氮化鈦(TiN)。本發明主要藉由氮化鈦的生成及運用氮化鈦的高溫穩定性，在熱軋加熱爐內阻止沃斯田鐵晶粒的過度成長。然而，當氮含量太高時，會造成氮化鈦過度粗化而成為破壞起始源。因此，較佳地，氮含量應控制在0.0020~0.0150wt%。 Nitrogen is a solid solution strengthening element, and the bonding property of nitrogen and titanium is good, and titanium nitride (TiN) starts to form at a high temperature exceeding 1400 ° C or higher. The present invention mainly prevents the excessive growth of the Worthite iron crystal grains in the hot rolling furnace by the formation of titanium nitride and the high temperature stability of the titanium nitride. However, when the nitrogen content is too high, the titanium nitride is excessively roughened to become a source of destruction. Therefore, preferably, the nitrogen content should be controlled to be 0.0020 to 0.0150% by weight.
鈦：為常用的析出強化元素，鈦除了可於高溫產生氮化鈦外，亦可在第一階段噴水冷卻與持溫過程中，產生碳化鈦(TiC)析出。較佳地，鈦與氮的含量比值係大於3.42，以使鈦的過飽和度提高，並可在短時間內大量成核產生奈米級析出物，進而達到析出強化的目的。然而，當鈦含量太高時，會使得析出的碳化鈦粗化，並讓析出強化效果下降。因此，較佳地，鈦含量應控制在0.03~0.30wt%。 Titanium: It is a commonly used precipitation strengthening element. In addition to titanium nitride which can be produced at high temperature, titanium can also be precipitated in the first stage of water spray cooling and holding temperature to produce titanium carbide (TiC). Preferably, the ratio of the content of titanium to nitrogen is greater than 3.42, so that the supersaturation of titanium is improved, and a large amount of nucleation can be produced in a short time to produce nano-scale precipitates, thereby achieving the purpose of precipitation strengthening. However, when the titanium content is too high, the precipitated titanium carbide is coarsened and the precipitation strengthening effect is lowered. Therefore, preferably, the titanium content should be controlled to be 0.03 to 0.30% by weight.
矽：為固溶強化元素，矽可促進肥粒鐵相變化並且延遲雪明碳鐵的析出，使得過飽和的碳得以產生大量奈米級析出物。當矽添加不足時，則無法得到上述效果。因此，較佳地，矽含量應控制在 0.01~1.20wt%。 矽: For the solid solution strengthening element, strontium can promote the iron phase change of the fertilizer and delay the precipitation of ferritic carbon iron, so that the supersaturated carbon can produce a large number of nano-scale precipitates. When the 矽 is insufficiently added, the above effect cannot be obtained. Therefore, preferably, the niobium content should be controlled at 0.01~1.20wt%.
磷：屬於鋼材中的不純物，容易偏析至晶界，造成晶界脆化。然而，磷也是促進肥粒鐵生成的重要元素，適當的調整磷含量，可控制肥粒鐵之生成。因此，較佳地，磷含量應控制在0.01~0.06wt%。 Phosphorus: It is an impurity in steel, which is easy to segregate to the grain boundary and cause grain boundary embrittlement. However, phosphorus is also an important element to promote the formation of ferrite and iron. Proper adjustment of phosphorus content can control the formation of ferrite. Therefore, preferably, the phosphorus content should be controlled to be 0.01 to 0.06 wt%.
硫：屬於鋼材中的不純物，在高溫時可能產生TiS、Ti4C2S2與MnS，其中TiS及Ti4C2S2會消耗所添加的鈦，而MnS受軋延後會呈長條狀，成為破壞起始源。因此，較佳地，硫含量應控制在0.0006~0.02wt%。 Sulfur: It is an impurity in steel. TiS, Ti 4 C 2 S 2 and MnS may be produced at high temperatures. TiS and Ti 4 C 2 S 2 will consume the added titanium, while MnS will be stripped after rolling. Shape, becoming the source of destruction. Therefore, preferably, the sulfur content should be controlled at 0.0006 to 0.02 wt%.
釩：為常用的析出強化元素，當添加適量釩時，可延後TiC析出物的粗大，使得TiC可保持奈米級尺寸並大量分散於肥粒鐵相中。然而，當釩含量太高時，則容易讓析出物粗化。因此，較佳地，釩含量應控制在0.01~0.30wt%。 Vanadium: It is a commonly used precipitation strengthening element. When an appropriate amount of vanadium is added, the coarseness of the TiC precipitate can be delayed, so that the TiC can maintain the nanometer size and be dispersed in the ferrite iron phase. However, when the vanadium content is too high, it is easy to coarsen the precipitate. Therefore, preferably, the vanadium content should be controlled to be 0.01 to 0.30% by weight.
鉻：為提高鋼材硬化能與提昇耐蝕性的重要元素，同時也是析出強化元素。添加鉻的目的是藉由鉻與碳的良好親和性，以延遲雪明碳鐵之析出。因此，較佳地，鉻含量應控制在0.1~1.0wt%。 Chromium: An important element for improving the hardening energy of steel and improving corrosion resistance, and also a precipitation strengthening element. The purpose of adding chromium is to delay the precipitation of ferritic carbon iron by a good affinity of chromium and carbon. Therefore, preferably, the chromium content should be controlled to be 0.1 to 1.0% by weight.
鋁：主要用來作為煉鋼時進行脫氧。當鋁含量低於0.01wt%時，將造成脫氧不足；當鋁含量高於0.30wt%時，將影響成形性。因此，較佳地，鋁含量應控制在0.01~0.30wt%。 Aluminum: Mainly used for deoxidation during steel making. When the aluminum content is less than 0.01% by weight, deoxidation is insufficient; when the aluminum content is more than 0.30% by weight, the formability is affected. Therefore, preferably, the aluminum content should be controlled to be 0.01 to 0.30% by weight.
圖1顯示本發明高強度熱軋鋼材之製造方法流程圖。參閱圖1之步驟S11，提供一鋼胚，該鋼胚包括0.01~0.25wt%的碳、0.50~3.00wt%的錳、0.01~1.20wt%的矽、0.01~0.06wt%的磷、0.0006~0.02wt%的硫、0.1~1.0wt%的鉻、0.03~0.30wt%的鈦、0.0020~0.0150wt%的氮、0.01~0.30wt%的鋁以及平衡量的鐵與不顯著的雜質。在此 步驟中，該鋼胚係可依據一般熔煉製程製作，例如將上述元素組成與鐵進行熔煉後，再予以連鑄成鋼胚。 BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing the method of manufacturing the high strength hot rolled steel of the present invention. Referring to step S11 of FIG. 1, a steel embryo is provided, which comprises 0.01-0.25 wt% carbon, 0.50-3.00 wt% manganese, 0.01-1.20 wt% bismuth, 0.01-0.06 wt% phosphorus, 0.0006~. 0.02 wt% sulfur, 0.1-1.0 wt% chromium, 0.03-0.30 wt% titanium, 0.0020-0.0150 wt% nitrogen, 0.01-0.30 wt% aluminum, and a balance of iron with insignificant impurities. here In the step, the steel germ system can be produced according to a general melting process, for example, the above elemental composition is smelted with iron, and then continuously cast into a steel embryo.
在本實施例中，為進一步提升鋼材之抗拉強度，該鋼胚可另包括一合金成份，該合金成份選自0.01~0.10wt%的鈮、0.05~0.50wt%的鉬、0.01~0.60wt%的鎳、0.01~0.80wt%的銅及其彼此組合中的其中一種。 In this embodiment, in order to further improve the tensile strength of the steel, the steel embryo may further comprise an alloy component selected from 0.01 to 0.10 wt% of bismuth, 0.05 to 0.50 wt% of molybdenum, and 0.01 to 0.60 wt. One of nickel, 0.01 to 0.80% by weight of copper, and a combination thereof.
參閱步驟S12，將該鋼胚加熱至1150℃以上。此步驟主要是為了讓該鋼胚能在後續冷卻步驟中產生奈米析出物，因此，先將該鋼胚放置於一再加熱爐中，並將再加熱溫度控制在1150℃以上，以使TiN以外的其他析出物(如TiC)可再固溶回去，並在後續冷卻的步驟中，重新析出奈米級TiC。較佳地，該再加熱溫度不大於1300℃。 Referring to step S12, the steel embryo is heated to above 1150 °C. This step is mainly for the steel embryo to produce nano precipitates in the subsequent cooling step. Therefore, the steel embryo is first placed in a reheating furnace, and the reheating temperature is controlled to be above 1150 ° C so as to be outside the TiN. The other precipitates (such as TiC) can be re-dissolved back and the nano-TiC is re-precipitated in the subsequent cooling step. Preferably, the reheating temperature is not more than 1300 °C.
參閱步驟S13，對加熱後之鋼胚進行一熱軋步驟，並將完軋溫度控制在Ar3溫度以上，以獲得一完軋鋼材。此步驟可運用一般軋延機進行熱軋，而完軋溫度控制在Ar3溫度(為冷卻過程中沃斯田鐵開始變態成肥粒鐵的起始溫度)以上的目的在於：當完軋溫度低於Ar3溫度時，熱軋步驟將會在兩相區中進行，使得肥粒鐵相提早生成而導致肥粒鐵相的晶粒產生粗化現象，且相變化溫度太高的肥粒鐵無法產生大量的奈米析出物，故完軋溫度需控制在Ar3溫度以上。較佳地，完軋溫度為Ar3溫度至960℃。 Referring to step S13, a hot rolling step is performed on the heated steel slab, and the rolling temperature is controlled above the Ar3 temperature to obtain a finished steel. This step can be performed by a general rolling mill for hot rolling, and the finishing temperature is controlled at the Ar3 temperature (the starting temperature at which the Worth iron starts to metamorphose into the ferrite iron during the cooling process). The purpose is to lower the rolling temperature. At the temperature of Ar3, the hot rolling step will be carried out in the two-phase zone, so that the ferrite grain iron phase is formed early and the grain of the ferrite grain iron phase is coarsened, and the ferrite iron with too high phase change temperature cannot be produced. A large amount of nano-precipitate, so the rolling temperature needs to be controlled above the Ar3 temperature. Preferably, the finishing temperature is from Ar3 temperature to 960 °C.
參閱步驟S14，對該完軋鋼材進行一階段冷卻步驟，以製得高強度熱軋鋼材。在本實施例中，該階段冷卻步驟包括：以大於每秒20℃的冷卻速率將該完軋鋼材快速冷卻至580至760℃，以避免軋延所產生的缺陷被回復，同時可降低肥粒鐵的變態溫度； 對冷卻後之該完軋鋼材進行空冷持溫5至15秒，以產生肥粒鐵相變化，並且產生大量的奈米級析出物；及以大於每秒20℃的冷卻速率將持溫後之該完軋鋼材快速冷卻至一盤捲溫度，以進行盤捲。較佳地，該盤捲溫度小於350℃。 Referring to step S14, the finished steel is subjected to a one-stage cooling step to obtain a high-strength hot-rolled steel. In this embodiment, the cooling step of the stage comprises: rapidly cooling the finished steel material to a temperature of 580 to 760 ° C at a cooling rate of more than 20 ° C per second, so as to avoid the defects generated by the rolling and being recovered, and at the same time reducing the fertilizer particles. The metamorphic temperature of iron; Cooling the rolled steel is air cooled for 5 to 15 seconds to produce a ferrite grain iron phase change, and a large amount of nanoscale precipitates are produced; and the temperature is maintained at a cooling rate of more than 20 ° C per second. The finished steel is rapidly cooled to a coil temperature for coiling. Preferably, the coil temperature is less than 350 °C.
茲以下列實例予以詳細說明本發明，唯並不意謂本發明僅侷限於此等實例所揭示之內容。 The invention is illustrated by the following examples, which are not intended to be limited to the scope of the invention.
依據表1之成份進行調配，再預先進行真空熔煉並澆鑄製得鋼胚。依據表2之再加熱溫度，使鋼胚於一高溫爐中進行加熱，並維持再加熱溫度2小時，以獲得經加熱之鋼胚。於一軋延機中對經加熱之鋼胚進行熱軋步驟，再依據表2之完軋溫度，將鋼胚軋延至3~5毫米厚，以獲得完軋鋼材。完軋鋼材以每秒30℃的冷卻速率進行第一階段冷卻步驟，並依據表2之持溫溫度及持溫時間進行空冷持溫，再以每秒30℃的冷卻速率將持溫後之完軋鋼材快速冷卻至300℃以下，以進行盤捲步驟，最後製得發明例1~19之熱軋鋼材。 According to the composition of Table 1, the steel preform is prepared by vacuum melting and casting in advance. The steel embryos were heated in a high temperature furnace according to the reheating temperature of Table 2, and the reheating temperature was maintained for 2 hours to obtain heated steel embryos. The heated steel preform is subjected to a hot rolling step in a rolling mill, and then the steel blank is rolled to a thickness of 3 to 5 mm according to the rolling temperature of Table 2 to obtain a rolled steel. The finished steel is subjected to a first-stage cooling step at a cooling rate of 30 ° C per second, and air-cooling is carried out according to the holding temperature and holding time of Table 2, and then the temperature is maintained at a cooling rate of 30 ° C per second. The rolled steel material was rapidly cooled to 300 ° C or lower to carry out the coiling step, and finally the hot rolled steel materials of Inventive Examples 1 to 19 were obtained.
1.降伏強度(Yield Strength，以下簡稱為「YS」)：依據標準方法CNS 2112,G2014進行測試，單位為MPa。 1. Yield Strength (hereinafter referred to as "YS"): Tested according to the standard method CNS 2112, G2014, the unit is MPa.
2.抗拉強度(Tensile Strength，以下簡稱為「TS」)：依據標準方法CNS 2112,G2014進行測試，單位為MPa。 2. Tensile Strength (hereinafter referred to as "TS"): Tested according to the standard method CNS 2112, G2014, the unit is MPa.
3.伸長率(Elongation，以下簡稱為「E1」)：依據標準方法CNS 2112,G2014進行測試，單位為%。 3. Elongation (hereinafter referred to as "E1"): The test was performed according to the standard method CNS 2112, G2014, and the unit is %.
4.麻田散鐵比率：單位為%。 4. Ma Tian loose iron ratio: the unit is %.
發明例1~19之測試結果如表2所示。由表2之測試結果可證明，透過適當地調整鋼材組成及含量比例，並控制再加熱溫度(>1150℃)、完軋溫度(<960℃)及階段冷卻空冷持溫的溫度與時間，確實可製得低降伏比與超高抗拉強度的熱軋鋼材。 The test results of Inventive Examples 1 to 19 are shown in Table 2. From the test results in Table 2, it can be proved that by properly adjusting the steel composition and content ratio, and controlling the reheating temperature (>1150 ° C), the rolling temperature (<960 ° C) and the temperature and time of the cooling air cooling temperature, it is indeed It can produce hot rolled steel with low drop ratio and ultra high tensile strength.
本發明利用光學顯微鏡與電子顯微鏡對發明例1~19所製得之熱 軋鋼材進行顯微結構的觀察，發現鋼材主要是以肥粒鐵相為主，且肥粒鐵相比率大於55%。此外，肥粒鐵相中亦發現分散有大量的碳化鈦析出物，且該等碳化鈦析出物之粒徑為20奈米以下。另外，表2之結果亦顯示各鋼材中的麻田散鐵比率均介於15至45%之間。 The present invention utilizes an optical microscope and an electron microscope to heat the inventive examples 1 to 19. The microstructure of the rolled steel was observed. It was found that the steel was mainly composed of ferrite and iron phases, and the ratio of ferrite and iron was more than 55%. Further, it has been found that a large amount of titanium carbide precipitates are dispersed in the ferrite phase, and the titanium carbide precipitates have a particle diameter of 20 nm or less. In addition, the results in Table 2 also show that the ratio of 麻田散铁 in each steel is between 15 and 45%.
本發明以奈米析出強化之肥粒鐵相加上面積比率為15至45%之低溫變態相(麻田散鐵或變韌鐵)的設計，可使鋼材具備較低之降伏強度(降伏比<0.75)。此外，由於肥粒鐵相中存在大量的奈米析出物，因此，鋼材之抗拉強度可提升至800MPa以上。再者，本發明製造方法所製得之高強度熱軋鋼材亦具備相當的拉伸伸長率及較佳之加工硬化率，故鋼材之冷加工成形性亦可大幅提升。 The invention adopts the design of the nano-precipitation-enhanced ferrite-grain iron phase plus the low-temperature metamorphic phase (Mashang loose iron or toughened iron) with an area ratio of 15 to 45%, so that the steel has a lower lodging strength (a ratio of lodging to < 0.75). In addition, since a large amount of nano-precipitates are present in the ferrite phase, the tensile strength of the steel can be increased to 800 MPa or more. Furthermore, the high-strength hot-rolled steel obtained by the production method of the present invention also has a relatively high tensile elongation and a good work hardening rate, so that the cold formability of the steel can be greatly improved.
上述實施例僅為說明本發明之原理及其功效，並非限制本發明，因此習於此技術之人士對上述實施例進行修改及變化仍不脫本發明之精神。本發明之權利範圍應如後述之申請專利範圍所列。 The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the scope of the present invention. The scope of the invention should be as set forth in the appended claims.
S11~S14‧‧‧步驟 S11~S14‧‧‧Steps
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