TWI640639B - Dual phase steel and method of forming the same - Google Patents
Dual phase steel and method of forming the same Download PDFInfo
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Abstract
本發明提供一種雙相鋼材及其製造方法,其係將具有特定成分之鋼胚經過特定熱軋製程條件,並搭配特定層流冷卻製程條件,以製得具有特定體積比之肥粒鐵相及麻田散鐵相,進而獲得具有高抗拉強度及高伸長率的雙相鋼材。 The invention provides a duplex steel and a manufacturing method thereof, which are characterized in that a steel preform having a specific composition is subjected to a specific hot rolling process condition and combined with a specific laminar flow cooling process condition to obtain a ferrite phase having a specific volume ratio and Ma Tian loose iron phase, which in turn obtains duplex steel with high tensile strength and high elongation.
Description
本發明是關於一種鋼材及其製造方法,特別是關於一種雙相鋼材及其製造方法。 The present invention relates to a steel material and a method of manufacturing the same, and more particularly to a duplex steel material and a method of manufacturing the same.
典型的雙相鋼材為複合組織的鋼材,其係包含軟質的肥粒鐵相及散佈在肥粒鐵相中之硬質的麻田散鐵相。因此,雙相鋼材兼具質軟及質硬之特性,可滿足新一代汽車零組件鋼材的需求,因為雙相鋼材不僅可提供足夠的安全保障,亦兼具良好的加工成形性。一般而言,降伏比愈小的材料,其加工成形性愈佳。降伏比係定義為降伏強度與抗拉強度的比值,其中降伏強度係使材料開始產生塑性變形所需的應力,而抗拉強度為材料破裂前所能承受的最大應力。另外,在進行加工時,由於雙相組織的特性,習知雙相鋼材之軟硬組織交接的界面易因受力而破裂。因此,一般雙相鋼材的伸長率較低。 A typical duplex steel is a composite structural steel that contains a soft ferrite iron phase and a hard granulated iron phase dispersed in the ferrite iron phase. Therefore, duplex steel has both soft and hard properties, which can meet the needs of the new generation of automotive component steels, because duplex steels not only provide sufficient safety, but also have good formability. In general, the smaller the ratio of the lower the ratio, the better the formability of the material. The drop ratio is defined as the ratio of the drop strength to the tensile strength, where the drop strength is the stress required to initiate plastic deformation, and the tensile strength is the maximum stress that can be withstood before the material breaks. In addition, at the time of processing, due to the characteristics of the two-phase structure, the interface of the soft and hard structure of the conventional duplex steel is easily broken by the force. Therefore, the elongation of the general duplex steel is generally low.
近年來,由於節能環保的重要性日益增加,汽車鋼材的目標係在兼顧高強度與薄尺寸。然而,具有高強度的雙相鋼材在厚度小於3毫米時,會造成層流冷卻製程中冷 卻溫度及/或持溫時間控制不當,或鋼材因邊緣過冷,導致鋼材在不同位置之相比例及性質上具有差異,也會有產生邊波、中波,而導致板形不良,以及表面紅銹的問題,進而使得鋼材無法滿足後續應用的需求。 In recent years, due to the increasing importance of energy conservation and environmental protection, the goal of automotive steel is to combine high strength and thin size. However, duplex steel with high strength will cause cold in the laminar cooling process when the thickness is less than 3 mm. However, if the temperature and/or temperature holding time are not properly controlled, or the steel is too cold due to the edge, the difference in the ratio and properties of the steel at different positions may occur, and side waves and medium waves may be generated, resulting in poor shape and surface. The problem of red rust, which in turn makes the steel unable to meet the needs of subsequent applications.
有鑑於此,亟須提供一種雙相鋼材及其製造方法,以獲得兼具有高抗拉強度、低降伏比及高伸長率,且不具有板形不良及兩相分布不均的問題。 In view of the above, it is not necessary to provide a duplex steel and a method of manufacturing the same to obtain a high tensile strength, a low drop ratio, and a high elongation, and there is no problem of poor sheet shape and uneven distribution of two phases.
本發明之一態樣是提供一種雙相鋼材的製造方法,其係藉由對含有特定成分之鋼胚進行包含二階段熱軋步驟的熱軋製程後,再將其冷卻而獲得雙相鋼材。 One aspect of the present invention provides a method for producing a duplex steel obtained by subjecting a steel preform containing a specific component to a hot rolling pass including a two-stage hot rolling step, followed by cooling to obtain a duplex steel.
本發明之另一態樣是提供一種雙相鋼材,其係具有特定體積比之肥粒鐵相及麻田散鐵相,且具有特定晶粒尺寸的肥粒鐵相。 Another aspect of the present invention is to provide a duplex steel having a ferrite phase having a specific volume ratio of a ferrite phase and a granulated iron phase and having a specific grain size.
根據本發明之一態樣,提供一種雙相鋼材的製造方法,其係包含提供鋼胚、對鋼胚進行熱軋製程,以獲得完軋鋼材,以及對完軋鋼材進行層流冷卻製程,以獲得雙相鋼材。鋼胚係包含0.08重量%至0.20重量%的碳、1.5重量%至3.0重量%的錳、1.0重量%至1.5重量%的矽、1.0重量%至2.0重量%的鋁、大於0重量%且小於或等於0.5重量%以下的鉬、大於0重量%且小於或等於0.20重量%以下的鈦、大於0重量%且小於或等於0.20重量%以下的釩、大於0重量%且小於或等於0.01重量%以下的氮、小於或等於0.15重量 %的鈮、其餘量為鐵及不可避免的雜質。 According to an aspect of the present invention, a method for manufacturing a duplex steel is provided, which comprises providing a steel blank, performing a hot rolling process on the steel blank to obtain a rolled steel, and performing a laminar cooling process on the finished steel. Obtained duplex steel. The steel germline comprises from 0.08 wt% to 0.20 wt% carbon, from 1.5 wt% to 3.0 wt% manganese, from 1.0 wt% to 1.5 wt% niobium, from 1.0 wt% to 2.0 wt% aluminum, greater than 0 wt% and less than Or equal to 0.5% by weight or less of molybdenum, more than 0% by weight and less than or equal to 0.20% by weight of titanium, more than 0% by weight and less than or equal to 0.20% by weight of vanadium, more than 0% by weight and less than or equal to 0.01% by weight The following nitrogen, less than or equal to 0.15 weight % of the bismuth, the balance is iron and inevitable impurities.
上述熱軋製程包含對鋼胚進行第一熱軋步驟,以形成第一熱軋鋼材,接著,對第一熱軋鋼材進行第二熱軋步驟,以形成完軋鋼材。第一熱軋步驟之第一軋延比為1.0至2.0,且第二熱軋步驟之第二軋延比為0至0.5。上述層流冷卻製程係以每秒10℃以上的冷卻速率,使完軋鋼材冷卻至450℃以下。 The hot rolling process includes performing a first hot rolling step on the steel blank to form a first hot rolled steel material, and then performing a second hot rolling step on the first hot rolled steel material to form a rolled steel material. The first rolling ratio of the first hot rolling step is 1.0 to 2.0, and the second rolling ratio of the second hot rolling step is 0 to 0.5. The above laminar cooling process cools the finished steel to below 450 ° C at a cooling rate of 10 ° C or more per second.
根據本發明之一實施例,上述熱軋製程的鋼帶速度為7.0m/s至9.0m/s。 According to an embodiment of the present invention, the steel strip speed of the above hot rolling pass is from 7.0 m/s to 9.0 m/s.
根據本發明之一實施例,在上述熱軋製程之前,更包含對鋼胚進行一加熱製程,以使該鋼胚升溫至1200℃至1250℃。 According to an embodiment of the present invention, before the hot rolling process, the steel embryo is further subjected to a heating process to raise the steel embryo to 1200 ° C to 1250 ° C.
根據本發明之一實施例,上述熱軋製程之完軋溫度係大於或等於Ar3溫度。 According to an embodiment of the invention, the rolling temperature of the hot rolling pass is greater than or equal to the Ar3 temperature.
根據本發明之一實施例,在上述層流冷卻製程之後,方法更包含對雙相鋼材進行盤捲步驟。 According to an embodiment of the invention, after the laminar cooling process described above, the method further comprises the step of coiling the duplex steel.
根據本發明之一實施例,上述冷卻速率為每秒10℃至100℃。 According to an embodiment of the invention, the above cooling rate is from 10 ° C to 100 ° C per second.
根據本發明之一實施例,上述層流冷卻製程包含第一冷卻步驟、空冷步驟及第二冷卻處理。首先,對完軋鋼材進行第一冷卻步驟,以形成第一冷卻鋼材,其中第一冷卻步驟係將完軋鋼材冷卻至600至700℃。接著,對第一冷卻鋼材進行空冷步驟,以形成一第二冷卻鋼材。然後,對第二冷卻鋼材進行第二冷卻步驟,以使第二冷卻鋼材冷卻至 450℃以下。 According to an embodiment of the invention, the laminar cooling process includes a first cooling step, an air cooling step, and a second cooling process. First, a first cooling step is performed on the finished steel to form a first cooled steel, wherein the first cooling step cools the finished steel to 600 to 700 °C. Next, the first cooled steel material is subjected to an air cooling step to form a second cooled steel material. Then, the second cooling steel is subjected to a second cooling step to cool the second cooled steel material to Below 450 °C.
根據本發明之另一態樣,提供一種雙相鋼材,其係包含0.08重量%至0.20重量%的碳、1.5重量%至3.0重量%的錳、1.0重量%至1.5重量%的矽、1.0重量%至2.0重量%的鋁、大於0重量%且小於或等於0.5重量%以下的鉬、大於0重量%且小於或等於0.20重量%以下的鈦、大於0重量%且小於或等於0.20重量%以下的釩、大於0重量%且小於或等於0.01重量%以下的氮、小於或等於0.15重量%的鈮、其餘量為鐵及不可避免的雜質。再者,雙相鋼材之肥粒鐵相與麻田散鐵相之體積比為1.2至1.9,且肥粒鐵相之平均晶粒尺寸為不大於10μm。 According to another aspect of the present invention, there is provided a duplex steel comprising 0.08 wt% to 0.20 wt% carbon, 1.5 wt% to 3.0 wt% manganese, 1.0 wt% to 1.5 wt% niobium, 1.0 wt. % to 2.0% by weight of aluminum, more than 0% by weight and less than or equal to 0.5% by weight of molybdenum, more than 0% by weight and less than or equal to 0.20% by weight of titanium, more than 0% by weight and less than or equal to 0.20% by weight or less Vanadium, more than 0% by weight and less than or equal to 0.01% by weight of nitrogen, less than or equal to 0.15% by weight of bismuth, the balance being iron and unavoidable impurities. Furthermore, the volume ratio of the ferrite phase of the duplex steel to the granulated iron phase is 1.2 to 1.9, and the average grain size of the ferrite phase is not more than 10 μm.
根據本發明之一實施例,上述肥粒鐵相之平均晶粒尺寸為5μm至10μm。 According to an embodiment of the present invention, the ferrite-iron phase has an average grain size of from 5 μm to 10 μm.
根據本發明之一實施例,上述雙相鋼材實質不包含變韌鐵相。 According to an embodiment of the invention, the duplex steel material does not substantially comprise a toughened iron phase.
應用本發明之雙相鋼材及其製造方法,其係藉由具有特定成分之鋼胚,在特定熱軋製程條件下,製得具有特定體積比之肥粒鐵相及麻田散鐵相,以獲得具有高抗拉強度及高伸長率的雙相鋼材。 The duplex steel of the present invention and a method for producing the same are obtained by using a steel preform having a specific composition to obtain a ferrite phase and a granulated iron phase having a specific volume ratio under a specific hot rolling condition. Dual phase steel with high tensile strength and high elongation.
100‧‧‧方法 100‧‧‧ method
110‧‧‧提供鋼胚 110‧‧‧ Providing steel embryos
120‧‧‧對鋼胚進行第一熱軋步驟,以獲得第一熱軋鋼材 120‧‧‧First hot rolling step on steel blank to obtain first hot rolled steel
130‧‧‧對第一熱軋鋼材進行第二熱軋步驟,以獲得完軋鋼材 130‧‧‧Second hot rolling step for the first hot rolled steel to obtain finished steel
140‧‧‧對完軋鋼材進行層流冷卻製程,以獲得雙相鋼材 140‧‧‧Laminar cooling process for finished steel to obtain duplex steel
為讓本發明之上述和其他目的、特徵、優點與實施例能更明顯易懂,所附圖式之詳細說明如下: The above and other objects, features, advantages and embodiments of the present invention will become more apparent and understood.
[圖1]係繪示根據本發明一實施例之雙相鋼材的製造方法的部分流程圖。 Fig. 1 is a partial flow chart showing a method of manufacturing a duplex steel according to an embodiment of the present invention.
承上所述,本發明提供一種雙相鋼材及其製造方法,其係藉由對含有特定成分之鋼胚進行包含二階段熱軋步驟的熱軋製程後,並經過層流冷卻製程而製得之具有特定兩相體積比的雙相鋼材。 In view of the above, the present invention provides a duplex steel and a method for producing the same, which are obtained by subjecting a steel preform containing a specific component to a hot rolling process including a two-stage hot rolling step and then performing a laminar cooling process. A duplex steel having a specific two-phase volume ratio.
請參閱圖1,其係繪示根據本發明一實施例之雙相鋼材的製造方法100的部分流程圖。首先,進行步驟110,提供鋼胚。在一實施例中,鋼胚係包含0.08重量%至0.20重量%的碳、1.5重量%至3.0重量%的錳、1.0重量%至1.5重量%的矽、1.0重量%至2.0重量%的鋁、大於0重量%且小於或等於0.5重量%以下的鉬、大於0重量%且小於或等於0.20重量%以下的鈦、大於0重量%且小於或等於0.20重量%以下的釩、大於0重量%且小於或等於0.01重量%以下的氮、小於或等於0.15重量%的鈮、其餘量為鐵及不可避免的雜質。藉由鋼胚具有特定成分及特定含量,可大幅提高沃斯田鐵相變態成肥粒鐵相的起始溫度。 Please refer to FIG. 1 , which is a partial flow chart of a method 100 for manufacturing a duplex steel according to an embodiment of the invention. First, step 110 is performed to provide a steel blank. In an embodiment, the steel germ system comprises 0.08 wt% to 0.20 wt% carbon, 1.5 wt% to 3.0 wt% manganese, 1.0 wt% to 1.5 wt% niobium, 1.0 wt% to 2.0 wt% aluminum, More than 0% by weight and less than or equal to 0.5% by weight of molybdenum, more than 0% by weight and less than or equal to 0.20% by weight of titanium, more than 0% by weight and less than or equal to 0.20% by weight of vanadium, more than 0% by weight and Less than or equal to 0.01% by weight of nitrogen, less than or equal to 0.15% by weight of bismuth, and the balance being iron and unavoidable impurities. By having a specific composition and a specific content of the steel embryo, the starting temperature of the iron phase of the Worthite transformation into the ferrite phase can be greatly improved.
若鋼胚中的矽含量小於1.0重量%,則無法有效達成固溶強化的效果;然而,若鋼胚中添加過多的矽,例如大於1.5重量%,則可能使後續製得之鋼材沿著晶界產生雪明碳鐵,由於雪明碳鐵為硬脆相的成分,因此若在晶界中產生雪明碳鐵,則容易在製程中導致鋼材破裂。鋼胚具有之特 定含量的鋁係有助於鋼胚在後續熱軋製程中,將沃斯田鐵相轉變成肥粒鐵相。然而,習知雙相鋼材的製造方法中,肥粒鐵相係在冷卻過程中才開始生成。因此,若使用之鋼胚的鋁含量小於1.0重量%,則組織中易有高碳相生成,若使用之鋼胚的鋁含量大於2.0重量%,則會導致嚴重的鑄造問題,因而無法獲得良好的雙相鋼材特性。 If the niobium content in the steel embryo is less than 1.0% by weight, the effect of solid solution strengthening cannot be effectively achieved; however, if too much niobium is added to the steel embryo, for example, more than 1.5% by weight, it is possible to make the subsequently obtained steel along the crystal. Snow-bound carbon iron is produced in the world. Since the ferritic carbon-iron is a component of the hard and brittle phase, if the ferritic carbon iron is produced in the grain boundary, the steel is easily broken during the process. Steel embryo A fixed amount of aluminum helps the steel to transform the Worth iron phase into a ferrite iron phase during subsequent hot rolling. However, in the conventional method for manufacturing a duplex steel, the ferrite phase is formed only during the cooling process. Therefore, if the aluminum content of the steel slab used is less than 1.0% by weight, a high carbon phase tends to be formed in the structure, and if the aluminum content of the steel slab used is more than 2.0% by weight, serious casting problems may occur, and thus good results cannot be obtained. Duplex steel properties.
鋼胚中適量添加錳元素,可使沃斯田鐵相的相變溫度降低,有利於部分沃斯田鐵相的殘留,並使波來鐵相的形成延後。但若鋼胚中具有太高含量的錳(例如大於3.0重量%),將使殘留之沃斯田鐵相的穩定性大大提高,不利於提高鋼材的延性,亦會使鋼材中帶狀組織增加,進而聚集硬脆相組織,故不利於鋼材的整體性能表現。 The addition of manganese in the steel embryo can reduce the phase transition temperature of the iron phase of the Worthfield, which is beneficial to the residual of the iron phase of some Vostian and delays the formation of the iron phase. However, if the steel embryo has too high content of manganese (for example, more than 3.0% by weight), the stability of the residual Wolster iron phase will be greatly improved, which is not conducive to the improvement of the ductility of the steel, and will also increase the band structure in the steel. And then gather hard and brittle phase structure, it is not conducive to the overall performance of steel.
鋼胚中添加特定含量的鉬、鈮及釩係有助於達成細化晶粒的效果。另外,鋼胚中添加特定含量的鈦、釩及氮,則是可達到析出強化的效果,即可使後續製得之鋼材的強度上升。 The addition of specific amounts of molybdenum, niobium and vanadium to the steel embryo contributes to the effect of refining the grains. In addition, when a specific content of titanium, vanadium, and nitrogen is added to the steel, the effect of precipitation strengthening can be achieved, and the strength of the subsequently obtained steel can be increased.
接著,對鋼胚進行熱軋製程。在一實施例中,在進行熱軋製程之前,可選擇性地對鋼胚進行加熱製程,以使鋼胚升溫至1200℃至1250℃。此加熱製程有助於鋼胚的合金成分發生固溶現象。熱軋製程首先進行步驟120,對鋼胚進行第一熱軋步驟,以獲得第一熱軋鋼材。在一實施例中,第一熱軋步驟之軋延比為1.0至2.0。補充說明的是,本發明說明書中使用的軋延比係定義為初始的鋼胚厚度及軋延後鋼胚厚度之差值與軋延後鋼胚厚度的比值,如式(1)所 示。若第一熱軋步驟之軋延比大於2.0,則鋼材的變形量太大,或易使鋼材之板型不符合需求,且軋延比大於2.0可能超出機台的負荷。若軋延比太小,例如小於1.0,則後續製得之鋼材可能有雙相組織分布不均的問題,亦有提早析出之肥粒鐵相不足的情況,並且會影響後續熱軋步驟的軋延比。 Next, the steel blank is subjected to a hot rolling process. In one embodiment, the steel blank may be selectively heated prior to the hot rolling to heat the steel to 1200 ° C to 1250 ° C. This heating process contributes to the solid solution of the alloy components of the steel. The hot rolling process first proceeds to step 120 where a first hot rolling step is performed on the steel blank to obtain a first hot rolled steel. In an embodiment, the rolling ratio of the first hot rolling step is from 1.0 to 2.0. It is to be noted that the rolling ratio used in the specification of the present invention is defined as the ratio of the difference between the initial steel blank thickness and the post-rolling steel blank thickness to the thickness of the rolled steel after the rolling, as in the formula (1). Show. If the rolling ratio of the first hot rolling step is greater than 2.0, the deformation amount of the steel material is too large, or the plate type of the steel is not suitable for the demand, and the rolling ratio of more than 2.0 may exceed the load of the machine. If the rolling ratio is too small, for example, less than 1.0, the subsequently obtained steel may have a problem of uneven distribution of the two-phase structure, and there is also an insufficient iron phase of the precipitated precipitate, which may affect the subsequent hot rolling step. Yanbi.
在式(1)中,r係代表軋延比,h係代表軋延後之鋼材厚度,而h0係代表軋延前之鋼材厚度。 In the formula (1), r represents the rolling ratio, h represents the thickness of the steel after rolling, and h 0 represents the thickness of the steel before rolling.
接著,進行步驟130,對第一熱軋鋼材進行第二熱軋步驟,以獲得完軋鋼材。在一實施例中,第二熱軋步驟的軋延比為0至0.5。若軋延比大於0.5,表示第一熱軋步驟的軋延比太小,無法達成本發明之熱軋製程的功效。在一例示中,第一熱軋步驟的軋延比係大於第二熱軋步驟的軋延比。在一具體例中,若熱軋製程包含七座熱軋機,則可選擇以前四座熱軋機進行第一熱軋步驟,而後三座熱軋機進行第二熱軋步驟,但本發明不限於此。再者,藉由控制第一熱軋步驟及第二熱軋步驟的軋延比,可縮小微觀組織中沃斯田鐵相的平均晶粒尺寸,進而縮小後續製得之鋼材的雙相組織的平均晶粒尺寸。 Next, in step 130, a second hot rolling step is performed on the first hot rolled steel material to obtain a rolled steel material. In one embodiment, the second hot rolling step has a rolling ratio of from 0 to 0.5. If the rolling ratio is more than 0.5, it means that the rolling ratio of the first hot rolling step is too small to achieve the effect of the hot rolling pass of the present invention. In one example, the rolling ratio of the first hot rolling step is greater than the rolling ratio of the second hot rolling step. In a specific example, if the hot rolling process includes seven hot rolling mills, the first four hot rolling mills may be selected for the first hot rolling step, and the last three hot rolling mills are subjected to the second hot rolling step, but the invention is not limited thereto. this. Furthermore, by controlling the rolling ratio of the first hot rolling step and the second hot rolling step, the average grain size of the Wostian iron phase in the microstructure can be reduced, thereby reducing the two-phase structure of the subsequently obtained steel. Average grain size.
本發明利用添加特定含量的合金與熱軋製程來製造雙相鋼材,以使雙相組織的成長時間較短,因此,提早於熱軋製程中開始成長肥粒鐵相,而非冷卻過程中才開始成長肥粒鐵相,更有助於後續生成具有良好強度與延性的雙相鋼材。 The invention utilizes the addition of a specific content of alloy and a hot rolling process to manufacture a duplex steel, so that the growth time of the two-phase structure is short, and therefore, the ferrite-iron phase begins to grow earlier in the hot rolling process, rather than during the cooling process. The beginning of the growth of the ferrite iron phase is more conducive to the subsequent generation of duplex steel with good strength and ductility.
在一實施例中,熱軋製程(包含第一熱軋步驟及第二熱軋步驟)的鋼帶速度為7.0m/s至9.0m/s。由於本發明須在熱軋製程開始產生肥粒鐵相,而鋼帶速度會影響鋼材的空冷時間,因此,鋼帶速度會連帶影響成長肥粒鐵相的時間。若鋼帶速度太快,例如高於9.0m/s,則鋼材的空冷時間太短,沒有足夠時間成長肥粒鐵相;反之,若鋼帶速度低於7.0m/s,則鋼材的空冷時間太長,可能形成晶粒過大的肥粒鐵,無法滿足本發明之肥粒鐵相的晶粒尺寸,進而影響後續鋼材的強度。 In one embodiment, the hot strip rolling speed (including the first hot rolling step and the second hot rolling step) is from 7.0 m/s to 9.0 m/s. Since the present invention is required to produce a ferrite-grained iron phase at the beginning of the hot rolling process, and the strip speed affects the air-cooling time of the steel, the speed of the strip will affect the time of growing the ferrite phase. If the speed of the steel strip is too fast, for example, higher than 9.0 m/s, the air cooling time of the steel is too short, and there is not enough time to grow the ferrite iron phase; conversely, if the steel strip speed is lower than 7.0 m/s, the air cooling time of the steel If it is too long, it may form an excessively large grain of ferrite, which cannot satisfy the grain size of the iron phase of the ferrite of the present invention, thereby affecting the strength of the subsequent steel.
在一實施例中,熱軋製程的完軋溫度須控制在大於或等於Ar3溫度。Ar3溫度係定義為鋼材在冷卻過程中,沃斯田鐵相開始變態成肥粒鐵相的溫度。因此,若完軋溫度未控制在大於或等於Ar3溫度,鋼材可能同時包含沃斯田鐵相及肥粒鐵相,則此不為本發明之雙相鋼材欲生成的微觀組織(即肥粒鐵相及麻田散鐵相),亦無法達成本發明之雙相鋼材的強度。 In one embodiment, the finishing temperature of the hot rolling pass must be controlled to be greater than or equal to the Ar3 temperature. The Ar3 temperature system is defined as the temperature at which the steel phase of the Vostian begins to metamorphose into the ferrite phase during the cooling process. Therefore, if the rolling temperature is not controlled at a temperature greater than or equal to Ar3, and the steel may contain both the Worthfield iron phase and the ferrite iron phase, this is not the microstructure of the duplex steel of the present invention (ie, ferrite iron). It is also impossible to achieve the strength of the duplex steel of the present invention.
然後,進行步驟140,對完軋鋼材進行層流冷卻製程,以獲得雙相鋼材。在一實施例中,層流冷卻製程係包含第一冷卻步驟、空冷步驟以及第二冷卻步驟。首先,對上述獲得之完軋鋼材進行第一冷卻步驟,以形成第一冷卻鋼材。在一實施例中,第一冷卻步驟係將完軋鋼材冷卻至650℃至700℃。接著,對第一冷卻鋼材進行空冷步驟,以形成第二冷卻鋼材。然後,對第二冷卻鋼材進行第二冷卻步驟,以使第二冷卻鋼材冷卻至450℃以下。若層流冷卻製程的冷 卻溫度高於450℃,則形成之雙相鋼材之微觀結構可能包含肥粒鐵相及變韌鐵相,然而,本發明之雙相鋼材係包含肥粒鐵相及麻田散鐵相,可大幅提升鋼材強度及伸長率,並降低降伏比。 Then, in step 140, a laminar cooling process is performed on the finished steel to obtain a duplex steel. In one embodiment, the laminar cooling process comprises a first cooling step, an air cooling step, and a second cooling step. First, a first cooling step is performed on the obtained rolled steel material to form a first cooled steel material. In one embodiment, the first cooling step cools the finished steel to 650 ° C to 700 ° C. Next, the first cooled steel material is subjected to an air cooling step to form a second cooled steel material. Then, the second cooling steel is subjected to a second cooling step to cool the second cooled steel to 450 ° C or lower. If the laminar cooling process is cold However, if the temperature is higher than 450 ° C, the microstructure of the formed duplex steel may include the ferrite iron phase and the tough iron phase. However, the duplex steel of the present invention comprises the ferrite iron phase and the Ma Tian iron phase, which can be substantially Improve steel strength and elongation, and reduce the ratio of fall and fall.
在一實施例中,層流冷卻製程的冷卻速率為每秒10℃以上,較佳為每秒10℃至100℃,更佳為每秒60℃至90℃。若冷卻速率低於每秒10℃,因冷卻速率太慢,第一冷卻步驟的時間增加,則空冷步驟的時間減少,不利於生成較小晶粒的肥粒鐵相,則無法使鋼材的強度有顯著地提升。 In one embodiment, the laminar cooling process has a cooling rate of 10 ° C or more per second, preferably 10 ° C to 100 ° C per second, more preferably 60 ° C to 90 ° C per second. If the cooling rate is lower than 10 ° C per second, because the cooling rate is too slow, the time of the first cooling step is increased, the time of the air cooling step is reduced, which is not conducive to the formation of the ferrite phase of the smaller grains, and the strength of the steel cannot be made. There is a significant improvement.
在一實施例中,在步驟140之後,可選擇性地對雙相鋼材進行盤捲步驟,以獲得鋼捲,其中盤捲步驟的盤捲溫度即上述層流冷卻製程中第二冷卻步驟的冷卻溫度。接著,在另一實施例中,可選擇性地對鋼捲進行酸洗步驟,以去除表面銹板,並進行再加工處理。 In an embodiment, after step 140, the duplexing steel may be selectively subjected to a coiling step to obtain a steel coil, wherein the coiling temperature of the coiling step is cooling of the second cooling step in the laminar cooling process. temperature. Next, in another embodiment, the steel coil may be selectively subjected to a pickling step to remove the surface rust plate and subjected to reprocessing.
藉由雙相鋼材的製造方法100所製得之雙相鋼材包含肥粒鐵相及麻田散鐵相。在一實施例中,製得之雙相鋼材實質不包含變韌鐵相。在一實施例中,肥粒鐵相及麻田散鐵相之體積比為1.2至1.9。若體積比大於1.9,表示肥粒鐵相太多,則所製得之鋼材的強度較低;然而,若體積比小於1.2,表示麻田散鐵相太多,則鋼材的伸長率較低。在一實施例中,肥粒鐵相的平均晶粒尺寸係不大於10μm,較佳為5μm至10μm。若肥粒鐵相的平均晶粒尺寸大於10μm,則會有肥粒鐵相及麻田散鐵相分布不均的問題,且較粗大的 組織容易使鋼材在進行塑形或其他應用時產生裂痕。在另一實施例中,由於雙相鋼材具有均勻分布的肥粒鐵相及麻田散鐵相,麻田散鐵相的平均晶粒尺寸亦不大於10μm。 The duplex steel obtained by the method 100 for producing a duplex steel includes a ferrite phase iron phase and a 麻田散铁 phase. In one embodiment, the biphasic steel produced does not substantially contain a toughened iron phase. In one embodiment, the volume ratio of the fermented iron phase to the 麻田 loose iron phase is from 1.2 to 1.9. If the volume ratio is greater than 1.9, indicating that the iron phase of the fertilizer is too much, the strength of the obtained steel is low; however, if the volume ratio is less than 1.2, indicating that the iron phase of the field is too much, the elongation of the steel is low. In one embodiment, the ferrite iron phase has an average grain size of no greater than 10 μm, preferably 5 μm to 10 μm. If the average grain size of the ferrite grain iron phase is larger than 10 μm, there will be a problem of uneven distribution of the ferrite grain phase and the granule iron phase, and the coarser The tissue tends to cause cracks in the steel during shaping or other applications. In another embodiment, since the duplex steel has a uniformly distributed ferrite phase and a granulated iron phase, the average grain size of the granulated iron phase is not more than 10 μm.
在一實施例中,藉由雙相鋼材的製造方法100所製得之雙相鋼材的拉伸強度為900MPa以上,降伏比為0.50至0.65,且伸長率為大於15%。 In one embodiment, the duplex steel obtained by the method 100 for producing a duplex steel has a tensile strength of 900 MPa or more, a drop ratio of 0.50 to 0.65, and an elongation of more than 15%.
以下利用數個實施例以說明本發明之應用,然其並非用以限定本發明,本發明技術領域中具有通常知識者,在不脫離本發明之精神和範圍內,當可作各種之更動與潤飾。 The following examples are used to illustrate the application of the present invention, and are not intended to limit the present invention. Those skilled in the art can make various changes without departing from the spirit and scope of the present invention. Retouching.
利用以下表一所列之鋼胚成分,以表二所列之製程條件配合上述之雙相鋼材的製造方法製造鋼材,並將所獲得之鋼材的微觀組織及機械性質列於以下表三。表一的「-」表示未添加之成分。在表三之微觀組織中,「F」表示肥粒鐵相,「B」表示變韌鐵相,而「M」表示麻田散鐵相。表三的機械性質係根據日本工業規格(JIS)進行拉伸試驗所測得,其中降伏比為降伏強度與抗拉強度的比值,而未能量測到的伸長率係以「-」表示。 Using the steel embryo components listed in Table 1 below, the steel materials were produced in accordance with the process conditions listed in Table 2 in conjunction with the above-described manufacturing method of the duplex steel, and the microstructure and mechanical properties of the obtained steel materials are listed in Table 3 below. The "-" in Table 1 indicates the unadded ingredients. In the microstructure of Table 3, "F" indicates the ferrite phase, "B" indicates the toughened iron phase, and "M" indicates the Matian iron phase. The mechanical properties of Table 3 were measured according to the tensile test of Japanese Industrial Standards (JIS), wherein the ratio of the drop is the ratio of the strength of the drop to the tensile strength, and the elongation measured by the energy is indicated by "-".
鋼胚C及鋼胚D由於矽含量較高(在1.0重量%至1.5重量%之間),不僅可達到固溶強化的效果,亦有助於避免雪明碳鐵在晶界生成,進而可避免鋼材破裂。再者,鋼胚C及鋼胚D之錳含量為2.0重量%至3.0重量%之間且鋁含量為1.0重量%至2.0重量%之間,故可使鋼胚在熱軋製程階段,便開始產生肥粒鐵相,並使波來鐵相的形成延後。 Steel embryo C and steel embryo D can not only achieve the effect of solid solution strengthening due to the high content of cerium (between 1.0% and 1.5% by weight), but also help to avoid the formation of schmöcarbon in the grain boundary. Avoid steel breakage. Furthermore, the manganese content of the steel embryo C and the steel embryo D is between 2.0% by weight and 3.0% by weight and the aluminum content is between 1.0% and 2.0% by weight, so that the steel embryo can be started in the hot rolling stage. Produces a ferrite grain iron phase and delays the formation of the Borne iron phase.
根據上表三的結果,鋼胚C及鋼胚D以條件三或條件四的製程所製得之鋼材的微觀組織皆為肥粒鐵相及麻田散鐵相,且肥料鐵相與麻田散鐵相的體積百分率係介於1.28至1.85,並具有平均粒徑為7μm至9μm的肥粒鐵相。因此,前述鋼材皆具有900MPa以上的抗拉強度、0.50至0.65的降伏比以及大於15%的伸長率。 According to the results in Table 3 above, the microstructure of the steel produced by the steel embryo C and the steel embryo D in the condition three or four conditions is the ferrite iron phase and the granitic iron phase, and the ferrite phase and the granitic iron The volume fraction of the phase is between 1.28 and 1.85 and has an iron phase of the ferrite having an average particle diameter of from 7 μm to 9 μm. Therefore, the aforementioned steel materials each have a tensile strength of 900 MPa or more, a fall ratio of 0.50 to 0.65, and an elongation of more than 15%.
然而,鋼胚A至鋼胚D在經過條件一及條件二的製程所製得之鋼材的肥粒鐵相平均晶粒尺寸皆較大(大於10μm),主要是由於條件一及條件二的加熱溫度較低(皆為1150℃),導致所添加之Nb、Ti、V及Mo無法充分固溶,因而無法達成晶粒細化的效果。再者,條件一及條件二的第一軋延比較小(小於1),導致所製得之鋼材的雙相組織分散不均,且在熱軋製程時肥粒鐵相的析出量不足。 However, the average grain size of the iron phase of the steel grain A to steel embryo D obtained by the process of Condition 1 and Condition 2 is larger (greater than 10 μm), mainly due to the heating of Condition 1 and Condition 2 The lower temperature (all 1150 ° C) causes the added Nb, Ti, V, and Mo to be insufficiently dissolved, and thus the effect of grain refinement cannot be achieved. Furthermore, the first rolling of Condition 1 and Condition 2 is relatively small (less than 1), resulting in uneven dispersion of the two-phase structure of the obtained steel, and insufficient precipitation of the ferrite-iron phase during the hot rolling.
條件一之熱軋製程的鋼帶速度較小(小於7.0m/s)且層流冷卻製程的冷卻速率較慢(小於10℃/s),因而導致過多肥粒鐵相生成,且為平均晶粒尺寸較大的肥粒鐵相,進而使製得之鋼材的強度不足(抗拉強度小於900MPa)。 Condition 1 The hot rolling speed of the steel strip is small (less than 7.0 m / s) and the laminar cooling process has a slower cooling rate (less than 10 ° C / s), resulting in excessive ferrite iron phase formation and average crystal The iron grain phase of the grain size is larger, and the strength of the obtained steel is insufficient (the tensile strength is less than 900 MPa).
條件一及條件二由於冷卻溫度較高(大於450℃),較容易形成肥粒鐵相及變韌鐵相的雙相組織,則製得之鋼材的抗拉強度較低,且降伏比較高,不利於製作高強度鋼材。 Condition 1 and Condition 2, because of the higher cooling temperature (greater than 450 ° C), it is easier to form a two-phase structure of the ferrite phase and the tough iron phase, and the obtained steel has lower tensile strength and higher fluctuation. Not conducive to the production of high-strength steel.
根據上述實施例,本發明藉由具有特定成分及含量的鋼胚,搭配加熱溫度、熱軋製程的軋延配比、鋼帶速 度及層流冷卻製程的冷卻速率及溫度,使製得之鋼材具有細小且均勻的肥粒鐵相,且肥粒鐵相及麻田散鐵相具有特定體積比,進而獲得具有高抗拉強度、高伸長率及特定降伏比的雙相鋼材。 According to the above embodiment, the present invention adopts a steel embryo having a specific composition and content, and is matched with a heating temperature, a rolling ratio of a hot rolling pass, and a steel strip speed. And the cooling rate and temperature of the laminar cooling process, so that the obtained steel has a fine and uniform ferrite grain iron phase, and the ferrite grain iron phase and the mai field iron phase have a specific volume ratio, thereby obtaining high tensile strength, Duplex steel with high elongation and specific drop ratio.
雖然本發明已以數個實施例揭露如上,然其並非用以限定本發明,在本發明所屬技術領域中任何具有通常知識者,在不脫離本發明之精神和範圍內,當可作各種之更動與潤飾,因此本發明之保護範圍當視後附之申請專利範圍所界定者為準。 While the invention has been described above in terms of several embodiments, it is not intended to limit the scope of the invention, and the invention may be practiced in various embodiments without departing from the spirit and scope of the invention. The scope of protection of the present invention is defined by the scope of the appended claims.
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