WO2012083671A1

WO2012083671A1 - Method for enhancing self-feeding ability of heavy section casting blank

Info

Publication number: WO2012083671A1
Application number: PCT/CN2011/076640
Authority: WO
Inventors: 李殿中; 栾义坤; 傅排先; 夏立军; 李依依
Original assignee: 中国科学院金属研究所
Priority date: 2010-12-23
Filing date: 2011-06-30
Publication date: 2012-06-28
Also published as: CN102161090A; KR20130094330A; JP2014500801A; US20130248056A1; EP2656946A1; KR101588677B1; EP2656946A4; JP5852126B2; CN102161090B

Abstract

A method for enhancing self-feeding ability of a heavy section casting blank includes the following steps: forced-cooling the outer surface of a casting blank to rapidly solidify it; heat-preserving the outer surface of the casting blank by a heat insulating material or an insulated cover to reduce the heat exchange intensity between the outer surface of the casting blank and the ambient; raising the outer surface temperature of the casting blank and reducing the radial temperature gradient of the casting blank via the latent heat of a casting blank core to make the casting blank core form a mushy region synchronously and promote the casting blank core to be solidified synchronously. The casting blank surface is in the high temperature state when the casting blank core is solidified synchronously, so that the self-feeding ability of the casting blank is enhanced under the solidification and shrinkage tensile stress of the casting blank core. This method is adapted for the heavy section metal casting blank, especially for the heavy section continuous casting round billet or square billet with the large height-diameter ratio and whose axial porosity can not be improved by the riser feeding. The method can eliminate the shrinkage void, the surface crack and the inner porosity of the casting blank.

Description

一种提高厚大断面铸坯自补缩能力的方法技术领域 Method for improving self-retracting capacity of thick and large section casting blanks

本发明涉及金属模铸宽厚板坯、厚大断面连铸圆坯、方坯与矩形坯等铸坯制造领域，具体地说是一种提高厚大断面铸坯自补缩能力，改善并消除铸坯内部缩孔疏松与表面裂纹的方法。背景技术 The invention relates to the field of metal mold casting wide slab, thick section continuous casting round billet, billet and rectangular billet, etc., in particular to improving the self-reduction ability of thick and thick section billet, improving and eliminating casting A method for loosening pores and surface cracks in a blank. Background technique

宽厚板被广泛应用于我国经济建设中。在大型舰船、远洋平台、水电机组、火电机组、压力容器、模具制造以及长途管线上，都大量使用宽厚板。我国近期新建数十条宽厚板轧钢生产线，包括鞍钢 5000mm、 5500mm轧机，宝钢 5000mm轧机等，新增产能 2000多万吨。因此，用于轧制宽厚板的厚大断面宽厚板坯需求量巨大。目前，连铸板坯最大厚度均小于 400mm，采用连铸板坯轧制厚度为 200mm的宽厚板，由于压下比小，很难保证芯部性能。而采用模铸方法或电渣重溶方法生产宽厚板坯，其生产效率低，成材率低，成本高。因此，迫切需要开发厚度大于 600mm的低成本、高效率宽厚板坯制造技术。水冷模宽厚板坯制造是一项快捷技术，但采用水冷模方法生产宽厚板坯时，由于水冷强度较大，容易造成宽厚板坯中心与表面温差大，凝固过程中热应力大，板坯表面和芯部产生裂纹。 Wide and thick plates are widely used in China's economic construction. Heavy plates are used extensively on large ships, offshore platforms, hydropower units, thermal power units, pressure vessels, mold making, and long-haul pipelines. In China, we have recently built dozens of wide and thick plate rolling production lines, including Angang 5000mm, 5500mm rolling mill, Baosteel 5000mm rolling mill, etc., with a new capacity of more than 20 million tons. Therefore, the demand for thick and thick slabs for rolling wide and thick plates is enormous. At present, the maximum thickness of the continuous casting slab is less than 400 mm, and the continuous casting slab is used to roll a thick plate having a thickness of 200 mm. Since the reduction ratio is small, it is difficult to ensure the core performance. The use of a die casting method or an electroslag remelting method for producing a wide and thick slab has a low production efficiency, a low yield, and a high cost. Therefore, there is an urgent need to develop a low cost, high efficiency wide and thick slab manufacturing technique with a thickness greater than 600 mm. The manufacture of wide and thick slabs for water-cooled molds is a fast technology. However, when water-cooled molds are used to produce wide and thick slabs, the water-cooling strength is large, and the temperature difference between the center and the surface of the wide and thick slabs is large, and the thermal stress during solidification is large. Cracks occur in the core.

大断面连铸圆坯用于取代一般模铸钢锭，其生产效率高，材料利用率高，表现出良好的发展势头。大断面连铸圆坯可用于生产核电筒类件，风电环类件以及汽车、轮船、机械用关键轴类零件，厚大断面圆坯的目标产品年产量超过 3000万吨。近年来，采用连铸技术生产厚大断面圆坯越来越受到重视。该技术是将金属液连续浇注到水冷结晶器中，钢水在水冷结晶器中凝固，并通过引锭装置不断将凝固部分由下端拉出，实现铸坯的连续铸造。采用该工艺生产铸坯，其高径比大，难以实现铸坯的轴线补缩，容易造成钢锭中心缩孔与疏松；且由于钢锭外表面多采用强制冷却工艺，造成外表面温度过低，产生裂纹。这些缺陷限制了连铸圆坯向更大断面尺寸（≥(D800mm) 的发展。 The large-section continuous casting round billet is used to replace the general die-cast steel ingot, which has high production efficiency and high material utilization rate, showing a good development momentum. Large-section continuous casting round billet can be used to produce nuclear torch parts, wind power ring parts and key shaft parts for automobiles, ships and machinery. The annual output of the target products of thick and large round billets exceeds 30 million tons. In recent years, the use of continuous casting technology to produce thick section round billets has received increasing attention. The technique is to continuously cast a molten metal into a water-cooled crystallizer, and the molten steel is solidified in a water-cooled crystallizer, and the solidified portion is continuously pulled out from the lower end by a starter device to realize continuous casting of the cast strand. The slab is produced by the process, and the height-to-diameter ratio is large, and it is difficult to realize the axial packing of the slab, which is easy to cause shrinkage and looseness in the center of the steel ingot; and because the outer surface of the steel ingot adopts a forced cooling process, the outer surface temperature is too low, resulting in crack. These defects limit the development of continuous casting round billets to larger cross-sectional dimensions (≥ (D800mm)).

厚度为 400mm以上的厚大断面连铸方坯和矩形坯同样存在内部缩孔疏松与表面裂纹等宏观缺陷。 Large-section continuous casting billets and rectangular billets with a thickness of 400 mm or more also have macroscopic defects such as internal shrinkage porosity and surface cracks.

一般而言，解决铸坯内部缩孔疏松缺陷，多采用增加冒口尺寸、或采用保温（发热）冒口，实现铸坯沿重力方向的顺序凝固。然而，厚大断面连铸坯的冒口比例非常小，且高径比大于 4，无法实现铸坯的轴向重力补缩。 In general, to solve the problem of loose pores in the slab, the size of the riser is increased, or the riser is heated to achieve the sequential solidification of the slab in the direction of gravity. However, the proportion of the riser of the thick section continuous casting billet is very small, and the aspect ratio is greater than 4, and the axial gravity feeding of the billet cannot be achieved.

综上所述，厚大断面铸坯内部缩孔疏松、表面裂纹是限制铸坯向更大断面尺寸发展的技术瓶颈。因此，提高厚大断面铸坯凝固过程中的补缩能力，解决厚大断面铸坯内部缩孔疏松与表面裂纹缺陷至关重要。发明内容 In summary, the internal shrinkage of the thick and large section slab is loose and the surface crack is the technical bottleneck restricting the development of the slab to a larger section size. Therefore, it is essential to improve the shrinkage ability of the thick section slab during solidification, and to solve the problem of shrinkage and surface crack defects in the thick section slab. Summary of the invention

本发明的目的在于提供一种通过提高厚大断面铸坯自补缩能力，改善厚大断面模铸宽厚板坯、连铸圆坯和矩形坯中心缩孔疏松和表面裂纹的方法，解决现有技术中铸坯中心质量差，表面产生裂纹，废品率高的问题。从而，有利于开发直径大于 500mm 的圆坯，厚度大于 400mm的方坯或矩形坯制造技术。 The object of the present invention is to provide a method for improving the shrinkage and surface cracks of the thick and large slab, the continuous casting round billet and the rectangular billet at the center by increasing the self-retracting capacity of the thick and large section casting blank, and solving the existing method. In the technology, the center of the casting blank is of poor quality, the surface is cracked, and the scrap rate is high. Thus, it is advantageous to develop a diameter greater than 500mm Round billet, billet or rectangular billet manufacturing technology with a thickness greater than 400 mm.

基于此目的，本发明的技术方案是： For this purpose, the technical solution of the present invention is:

一种提高厚大断面铸坯自补缩能力的方法，在金属液浇注后，立即通过模具水冷、直接喷水、喷雾或吹风等方式对铸坯外表面进行强制冷却，使铸坯外表面快速凝固结壳；待铸坯外表面温度降低到 800〜1000°C，凝固层厚度达到铸坯断面厚度或直径的 5-30%时，停止对外表面强制冷却。 A method for improving the self-retracting capacity of a thick section casting blank, after the pouring of the molten metal, the outer surface of the casting blank is forcedly cooled by means of water cooling, direct water spraying, spraying or blowing, so that the outer surface of the casting blank is fast Coagulating crust; When the outer surface temperature of the billet is lowered to 800~1000 °C, when the thickness of the solidified layer reaches 5-30% of the thickness or diameter of the billet section, the external surface is forced to cool.

所述的提高厚大断面铸坯自补缩能力的方法，凝固层厚度达到 50-300mm时，停止对外铸坯外表面强制冷却。 The method for improving the self-retracting capacity of the thick and large section casting blank, when the thickness of the solidified layer reaches 50-300 mm, stops the forced cooling of the outer surface of the outer casting blank.

所述的提高厚大断面铸坯自补缩能力的方法，控制铸坯外表面冷却条件，使铸坯外表面的温度维持在固相线以下 200〜400°C之间，铸坯外表面凝固层处于低变形抗力的塑性变形区。 The method for improving the self-retracting capacity of the thick and large section casting blank controls the cooling condition of the outer surface of the casting blank, so that the temperature of the outer surface of the casting blank is maintained between 200 and 400 ° C below the solidus line, and the outer surface of the casting blank is solidified. The layer is in a plastic deformation zone with low deformation resistance.

所述的提高厚大断面铸坯自补缩能力的方法，铸坯外表面停止强制冷却后，继而采用保温材料或保温罩对铸坯外表面进行保温，降低铸坯外表面与外界的换热强度，利用铸坯芯部返热使铸坯外表面温度升高，减小铸坯径向温度梯度，使铸坯芯部同时进入糊状区，使铸坯芯部同时凝固。 The method for improving the self-retracting capacity of the thick and large section casting blank, after the outer surface of the casting blank is stopped for forced cooling, the outer surface of the casting blank is insulated by the heat insulating material or the heat insulating cover, and the heat exchange between the outer surface of the casting blank and the outside is reduced. Strength, using the core heat of the slab to increase the temperature of the outer surface of the slab, reducing the radial temperature gradient of the slab, so that the core of the slab enters the mushy zone at the same time, and the core of the slab is simultaneously solidified.

所述的提高厚大断面铸坯自补缩能力的方法，芯部金属液同时凝固时，凝固收缩产生径向拉应力，拉应力作用于外表面高温凝固层，使已凝固金属发生塑性变形，由外表面向铸坯中心发生塑性移动，实现铸坯径向自补缩。 The method for improving the self-shrinking ability of a thick and large section casting blank, when the core metal liquid is simultaneously solidified, the solidification shrinkage generates a radial tensile stress, and the tensile stress acts on the outer surface high temperature solidified layer to plastically deform the solidified metal. Plastic movement occurs from the outer surface to the center of the slab to achieve radial self-feeding of the slab.

所述的提高厚大断面铸坯自补缩能力的方法，铸坯芯部同时凝固，并实现径向自补缩后，铸坯表面与芯部仍处于高温状态；此时进行高温脱坯，铸坯脱模温度大于 800 °C。 The method for improving the self-retracting capacity of the thick and large section casting blank, the core of the casting blank is simultaneously solidified, and after the radial self-feeding, the surface of the casting blank and the core are still in a high temperature state; The casting mold release temperature is greater than 800 °C.

所述的提高厚大断面铸坯自补缩能力的方法，铸坯脱模温度优选为 850-1200°C。所述的提高厚大断面铸坯自补缩能力的方法，该方法适用于厚度大于 400mm的连铸方坯或矩形坯，直径大于 500mm的连铸圆坯以及厚度大于 600mm的模铸宽厚板坯。 The method for improving the self-shrinking ability of the thick and large section casting blank is preferably 850-1200 ° C. The method for improving the self-retracting capacity of a thick and large section casting blank, the method is suitable for a continuous casting billet or a rectangular blank having a thickness of more than 400 mm, a continuous casting round blank having a diameter of more than 500 mm, and a molded wide and thick slab having a thickness of more than 600 mm. .

本发明的有益效果是： The beneficial effects of the invention are:

1、传统意义上，铸件补缩多沿重力方向进行轴线补缩，本发明通过控制铸坯外部冷却条件，实现了铸坯凝固过程中垂直于重力方向的径向自补缩。 1. In the traditional sense, the castings are supplemented by the axis in the direction of gravity. The invention achieves the radial self-feeding perpendicular to the direction of gravity during the solidification of the slab by controlling the external cooling conditions of the slab.

2、本发明在厚大断面铸坯凝固初期，采用水冷、雾冷或风冷的方式提高铸坯与外部的界面换热系数，使铸坯表面迅速凝固，快速建立铸坯表面强度，防止凝固初期铸坯表面凝固层厚度较薄，强度过低而产生的热裂纹。 2. In the initial stage of solidification of thick section slab, water-cooling, fog-cooling or air-cooling is adopted to improve the interface heat transfer coefficient between the slab and the outside, so that the surface of the slab is rapidly solidified, and the surface strength of the slab is quickly established to prevent solidification. The thickness of the solidified layer on the surface of the initial slab is relatively thin, and the strength is too low to cause thermal cracking.

3、本发明中，铸坯凝固层厚度断面直径或厚度的 5-30% (—般为 50-300mm)时，停止铸坯外部的强制冷却，此时已凝固的外层区域温度较低，用于为铸坯芯部未凝固区域提供一个低温外部环境，保证芯部金属液的凝固速度，避免芯部晶粒过于粗大。 3. In the present invention, when the thickness of the solidified layer of the slab is 5-30% (typically 50-300 mm), the forced cooling outside the slab is stopped, and the temperature of the solidified outer layer is low. It is used to provide a low temperature external environment for the unsolidified area of the core of the slab, to ensure the solidification speed of the core metal liquid, and to avoid the core grain being too coarse.

4、本发明在铸坯凝固中后期，对铸坯表面进行保温，使铸坯表面升温至塑性区，有利于防止铸坯表面受较大热应力而产生裂纹。 4. In the late stage of solidification of the slab, the invention heats the surface of the slab to heat the surface of the slab to the plastic zone, which is beneficial to prevent the surface of the slab from being subjected to large thermal stress and causing cracks.

5、本发明在铸坯凝固中后期对铸坯表面进行保温，可以减小厚大断面铸坯由内向外的温度梯度，使铸坯中心大面积区域同时进入糊状区，实现铸坯中心同时凝固，避免集中缩孔缺陷的产生。 5. The invention keeps the surface of the slab in the middle and late stage of solidification of the slab, and can reduce the temperature gradient from the inside to the outside of the slab of the thick section, so that the large area of the slab at the same time enters the mushy area at the same time, and realizes the center of the slab simultaneously Solidification, to avoid the occurrence of concentrated shrinkage defects.

6、采用本发明涉及的方法，铸坯中心大面积同时凝固时，由于凝固收缩产生径向拉应力，驱使铸坯外部已凝固的高温固相金属发生由铸坯表面向中心的塑性移动，实现铸坯凝固过程的径向自补缩，改善甚至消除铸坯内部缩孔疏松缺陷。 6. According to the method of the present invention, when the center of the slab is solidified at the same time, the diameter is solidified and contracted. The tensile stress drives the high-temperature solid phase metal which has solidified outside the slab to move from the surface of the slab to the center, and achieves the radial self-feeding of the slab solidification process, improving or even eliminating the shrinkage porosity of the slab.

7、采用本发明涉及的方法，充分发挥厚大断面铸坯径向自补缩能力，可以减小铸坯冒口尺寸，进一步提高厚大断面铸坯的材料利用率。 7. By adopting the method of the invention, the radial self-retracting capacity of the thick and thick section slab can be fully utilized, the size of the slab riser can be reduced, and the material utilization rate of the thick section slab can be further improved.

8、本发明使用范围较广，可用于生产厚大断面连铸圆坯、方坯或矩形坯，也可以用于生产模铸宽厚板坯，还可用于生产其他厚大断面铸件。 8. The invention has wide application range and can be used for producing round-shaped continuous billet, billet or rectangular billet, and can also be used for producing moulded wide and thick slab, and can also be used for producing other thick and large section castings.

9、采用本发明涉及的方法可以使铸坯实现高温脱模、热送，提高生产效率，节约能耗。 9. By adopting the method of the invention, the slab can be subjected to high temperature demolding and heat transfer, thereby improving production efficiency and saving energy consumption.

总之，本发明通过控制铸坯不同凝固阶段的外部冷却条件，首先使铸坯外表面迅速凝固结壳，建立强度，防止出现表面裂纹；然后对铸坯表面进行保温缓冷，使芯部大面积处于糊状区，铸坯外表面凝固层维持在较高温度以有利于实现塑性变形；进而实现铸坯后续凝固收缩过程中的同时凝固和固相移动，达到高温可变形金属径向自补缩的目的，从而消除铸坯内部缩孔与表面裂纹，并显著改善直至消除铸坯内部疏松。同时，本方法可以实现铸坯高温热送，提高生产效率，实现节能的目的。本发明适用于厚大断面金属铸坯，尤其适用于高径比大，无法通过冒口补缩改善轴线疏松的厚大断面连铸圆坯和方坯。附图说明 In short, the present invention firstly controls the external cooling condition of the slab in different solidification stages, firstly rapidly solidifies the outer surface of the slab, and establishes strength to prevent surface cracking; then, the surface of the slab is insulated and slowly cooled to make the core large area. In the mushy zone, the solidified layer on the outer surface of the slab is maintained at a higher temperature to facilitate plastic deformation; thereby achieving simultaneous solidification and solid phase movement in the subsequent solidification and shrinkage of the slab, and achieving high-temperature deformable metal radial self-feeding The purpose of this is to eliminate internal shrinkage cavities and surface cracks in the slab and significantly improve until the internal looseness of the slab is eliminated. At the same time, the method can realize high-temperature heat transfer of the slab, improve production efficiency, and achieve energy saving. The invention is suitable for thick and large section metal casting blanks, and is especially suitable for thick and large section continuous casting round billets and billets which have large height to diameter ratio and can not be improved by feeder feeding. DRAWINGS

图 1 采用本发明生产的水冷模铸宽厚板坯。 Figure 1 shows a water-cooled die cast wide slab produced by the present invention.

图 2 采用本发明生产的厚大断面连铸圆坯。其中，图 2(a)为厚大断面连铸圆坯实物图，图 2(b)为连铸圆坯横截面。 Figure 2 shows a thick section continuous casting round billet produced by the present invention. Among them, Fig. 2(a) is a solid view of a thick section continuous casting round billet, and Fig. 2(b) is a cross section of a continuous casting round billet.

图 3 未采用本发明生产的中心具有缩孔缺陷的连铸圆坯。其中，图 3(a)为厚大断面连铸圆坯实物图，图 3(b)为连铸圆坯横截面。具体实施方式 Figure 3 is a continuous casting billet having a shrinkage cavity defect in the center produced by the present invention. Among them, Fig. 3(a) is a solid view of a thick and continuous continuous casting round blank, and Fig. 3(b) is a cross section of a continuous casting round blank. detailed description

本发明通过提高厚大断面铸坯自补缩能力，消除内部缩孔与表面裂纹、改善疏松的方法，其实施步骤与方式如下： The invention improves the self-retracting ability of the thick and thick section casting blank, eliminates the internal shrinkage cavity and surface crack, and improves the looseness. The implementation steps and methods are as follows:

1、采用感应电炉或电弧炉等熔炼设备进行钢水熔炼，然后进行脱氧除气。 1. The molten steel is smelted by a melting furnace such as an induction furnace or an electric arc furnace, and then deoxidized and degassed.

2、将熔炼处理好的钢水浇注到模铸宽厚板坯型腔或连铸结晶中。 2. Cast the molten steel that has been smelted into the mold cavity or continuous casting crystallization.

3、通过水冷模具、结晶器对铸坯外表面进行强制冷却，使铸坯外表面迅速凝固结壳，亦可采用喷水、喷雾或吹气方式，加强铸坯对外热交换。 3. The outer surface of the slab is forcibly cooled by water-cooled mold and crystallizer, so that the outer surface of the slab can be quickly solidified and crusted. The water can be sprayed, sprayed or blown to enhance the external heat exchange of the slab.

4、在铸坯表面强制冷却过程中，采用接触式或非接触式测温设备监测铸坯表面温度，尽量控制铸坯表面温度在 800〜1000°C。防止温度过低，已凝固金属发生固态相变产生组织应力而诱发裂纹；同样避免温度过高，凝固层厚度较薄、强度较低，在金属液静压力下铸坯表面发生"鼓肚"，形成裂纹。 4. During the forced cooling of the surface of the slab, the surface temperature of the slab is monitored by contact or non-contact temperature measuring equipment, and the surface temperature of the slab is controlled as much as possible at 800~1000 °C. To prevent the temperature from being too low, the solidified phase of the solidified metal undergoes a solid phase transformation to induce tissue stress and induce cracks; also avoid the temperature is too high, the thickness of the solidified layer is thinner, the strength is lower, and the surface of the slab is "bulk belly" under the static pressure of the metal liquid. A crack is formed.

5、待铸坯凝固层厚度达到 50-300mm后，停止对铸坯表面进行强制冷却，转而对铸坯表面进行保温。铸坯表面温度不断上升，监测铸坯外表面温度，并通过保温或冷却等工艺措施调节铸坯与外部的界面换热强度，使铸坯表面温度维持在材料固相线以下 200〜400°C的塑性变形区。 5. After the thickness of the solidified layer of the slab reaches 50-300 mm, the surface of the slab is stopped for forced cooling, and the surface of the slab is kept warm. The surface temperature of the slab is continuously increased, the temperature of the outer surface of the slab is monitored, and the interfacial heat exchange intensity between the slab and the outside is adjusted by heat preservation or cooling, so that the surface temperature of the slab is maintained below 200~400 ° C of the solid phase of the material. Plastic deformation zone.

6、铸坯中心与外表面的温度梯度逐渐减小，铸坯中心区域大面积进入糊状区。在后续冷却过程中，铸坯中心实现同时凝固；凝固收缩产生拉应力，促使铸坯外表面已经凝固的固态金属发生塑性变形，铸坯表面向中心塑性移动，实现铸坯凝固过程的径向自补缩。 6. The temperature gradient between the center and the outer surface of the slab is gradually reduced, and the central area of the slab enters the mushy area in a large area. In the subsequent cooling process, the center of the slab is simultaneously solidified; the solidification shrinkage generates tensile stress, and the solid metal which has solidified on the outer surface of the slab is plastically deformed, and the surface of the slab is plastically moved toward the center to realize the radial self-solidification process of the slab. Feeding.

实施例 1 Example 1

该实施例采用本发明涉及的方法生产模铸宽厚板坯，宽厚板坯材质为 Q345 , 宽厚板坯厚度为 1000mm, 总质量为 60吨。 This embodiment produces a molded wide and thick slab by the method of the present invention. The wide and thick slab material is Q345, the thick and thick slab has a thickness of 1000 mm, and the total mass is 60 tons.

采用电弧炉进行钢水熔炼，再经 LF炉精炼，然后将钢水转入 VD炉进行脱氧除气，钢水在 1560Ό时浇注到分体式水冷模具中，总浇注时间为 30min。通过计算机模拟计算得知，浇注结束后 40min，宽厚板坯表面凝固层厚度为 90mm。此时减小水冷模具水流量，并增大模具与宽厚板坯之间的间隙，降低宽厚板坯表面散热速度。监测宽厚板坯表面温度变化发现，宽厚板坯表面温度由 920'C升高至 110(TC-1250°C，之后铸坯温度缓慢下降，直至完全凝固。铸坯完全凝固后，进行 900°C高温脱模，脱模后缓冷，冷却速度控制在 30-40°C/h。 The electric arc furnace is used for molten steel smelting, and then refined by the LF furnace, and then the molten steel is transferred to the VD furnace for deoxidation and degassing. The molten steel is poured into the split water-cooling mold at 1560 Torr, and the total pouring time is 30 min. According to the computer simulation calculation, the thickness of the solidified layer on the surface of the wide and thick slab is 90 mm 40 minutes after the pouring. At this time, the water flow rate of the water-cooling mold is reduced, and the gap between the mold and the wide and thick slab is increased, and the heat dissipation speed of the surface of the wide and thick slab is reduced. Monitoring the surface temperature change of the wide slab found that the surface temperature of the wide and thick slab increased from 920'C to 110 (TC-1250 °C, after which the temperature of the slab slowly decreased until it was completely solidified. After the slab was completely solidified, it was 900 °C. High temperature demoulding, slow cooling after demolding, cooling rate controlled at 30-40 ° C / h.

图 1为本实施例生产的宽厚板坯，无损探伤发现，连铸钢锭内部无疏松缩孔缺陷，铸坯表面质量完好，未发现表面裂纹。 Fig. 1 shows a wide and thick slab produced in the present embodiment. It is found by nondestructive testing that there is no loose and shrinkage hole defect in the continuous casting steel ingot, and the surface quality of the slab is intact, and no surface crack is found.

实施例 2 Example 2

该实施例采用本发明涉及的方法生产厚大断面连铸圆坯，圆坯材质为 20CrNi2Mo, 直径为 1000mm, 长度为 8m，圆坯总重量为 45吨。 This embodiment uses the method of the present invention to produce a thick section continuous casting round billet, the round billet material is 20CrNi2Mo, the diameter is 1000 mm, the length is 8 m, and the total weight of the round billet is 45 tons.

将熔炼处理好的钢水浇注到结晶器中，浇注温度为 1540Ό , 铸坯拉坯速度为 0.1m/mi_n。经模拟计算，铸坯被拉出结晶器时，表面凝固层厚度约为 50mm，表面温度约为 850°C。铸坯一经拉出结晶器即采用石棉布等保温隔热材料对铸坯表面进行保温，铸坯表面温度升高至 1200-1260°C，处于塑性区。铸坯由内向外温度梯度较小，实现了中心区域同时凝固。随后冷却过程中，铸坯外表面发生塑性变形，固相由外向内发生收缩移动，实现了径向自补縮。 The good melt processing molten steel poured into the mold, the pouring temperature is 1540Ό, slab casting speed of 0.1m / mi _n. According to the simulation calculation, when the slab is pulled out of the crystallizer, the surface solidified layer has a thickness of about 50 mm and a surface temperature of about 850 °C. Once the slab is pulled out of the crystallizer, the surface of the slab is insulated with an insulating material such as asbestos cloth, and the surface temperature of the slab is raised to 1200-1260 ° C, which is in the plastic zone. The temperature gradient of the slab from the inside to the outside is small, and the central region is simultaneously solidified. Subsequently, during the cooling process, the outer surface of the slab is plastically deformed, and the solid phase undergoes contraction and movement from the outside to the inside, realizing radial self-feeding.

如图 2(a)所示，为本实施例采用本发明涉及的技术生产的厚大断面连铸圆坯。经无损探伤发现，铸坯内部无缩孔缺陷，铸坯表面也无裂纹缺陷。如图 2(b)所示为圆坯横断面，中心无集中缩孔缺陷，疏松级别小于 2级。 As shown in Fig. 2(a), this is a thick-section continuous casting round blank produced by the technique of the present invention. After non-destructive testing, there is no shrinkage hole defect inside the slab, and there is no crack defect on the surface of the slab. As shown in Fig. 2(b), the round billet cross section has no concentrated shrinkage hole defects in the center, and the looseness level is less than 2 grades.

如图 3(a)所示，未实施本发明涉及技术所生产的同等尺寸规格的连铸圆坯。圆坯中心存在大面积缩孔和疏松缺陷，如图 3(b)所示。 As shown in Fig. 3(a), the continuous casting round billet of the same size and size produced by the technology of the present invention is not implemented. There are large areas of shrinkage and loose defects in the center of the round blank, as shown in Figure 3(b).

结果表明，本发明通过控制铸坯不同凝固阶段的外部冷却条件，使铸坯中心大面积进入糊状区，同时使铸坯外表面凝固层维持在较高温度，实现了铸坯后续凝固收缩过程中的固相塑性移动，达到了高温可变形金属径向 ΰ补缩的目的，改善了铸坯内部缩孔疏松，并防止了外表面裂纹的产生。 The results show that the invention can control the external cooling condition of different solidification stages of the slab, so that the center of the slab enters the mushy area in a large area, and at the same time, the solidification layer on the outer surface of the slab is maintained at a higher temperature, thereby realizing the subsequent solidification and shrinkage process of the slab. The solid phase plastic movement in the medium achieves the purpose of radial entanglement of the deformable metal at high temperature, improves the shrinkage of the internal shrinkage of the slab, and prevents the occurrence of cracks on the outer surface.

将上述实施例处理后的（&800-1200mm圆坯，按照 YB/T 4149-2006进行检测处理前后的缺陷等级（参见表 1 )。 The defect grade of the &800-1200 mm round billet treated in the above embodiment was measured according to YB/T 4149-2006 (see Table 1).

表 1

Table 1

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Claims

权利要求书 Claim

1、一种提高厚大断面铸坯自补缩能力的方法，其特征在于：在金属液浇注后，立即对铸坯外表面进行强制冷却，使铸坯外表面快速凝固结壳； 1. A method for improving the self-retracting capacity of a thick section casting blank, characterized in that: after the pouring of the molten metal, the outer surface of the casting blank is immediately forcibly cooled, so that the outer surface of the casting blank is rapidly solidified and crusted;

继而采用保温材料或保温罩对铸坯外表面进行保温， ffl以降低铸坯外表面与外界的换热强度； Then, the outer surface of the slab is insulated by using an insulating material or a heat insulating cover, and ffl is used to reduce the heat exchange intensity between the outer surface of the slab and the outside;

利用铸坯芯部返热使铸坯外表面温度升高，减小铸坯径向温度梯度，使铸坯芯部同时进入糊状区，促使铸坯芯部同时凝固； The heat of the outer surface of the slab is increased by the heat return of the core of the slab, and the radial temperature gradient of the slab is reduced, so that the core of the slab enters the mushy zone at the same time, and the core of the slab is simultaneously solidified;

铸坯芯部同时凝固时，铸坯表面仍处于高温状态，在芯部凝固收缩拉应力作用下提高铸坯自补缩能力； When the core of the slab is solidified at the same time, the surface of the slab is still in a high temperature state, and the self-shrinking ability of the slab is improved under the action of the solidification shrinkage and tensile stress of the core;

铸坯芯部完全凝固后，进行高温脱坯，脱坯后进行缓冷或高温退火。 After the core of the slab is completely solidified, it is subjected to high-temperature de-emulsion, and after de- ing, it is subjected to slow cooling or high-temperature annealing.

2、按照权利要求 1 所述的提高厚大断面铸坯自补缩能力的方法，其特征在于：在金属液浇注后，立即通过模具水冷、直接喷水、喷雾或吹风等方式对铸坯外表面进行强制冷却，待铸坯外表面温度降低到 800-1000°C，凝固层厚度达到铸坯断面厚度或直径的 5-30%时，停止对外表面强制冷却。 2. The method for improving the self-retracting capacity of a thick and large section slab according to claim 1, wherein: after the pouring of the molten metal, the mold is directly cooled by water, directly sprayed, sprayed or blown. The surface is forcedly cooled. When the temperature of the outer surface of the slab is lowered to 800-1000 ° C, and the thickness of the solidified layer reaches 5-30% of the thickness or diameter of the slab, the external surface is forced to cool.

3、按照权利要求 1或 2所述的提高厚大断面铸坯自补缩能力的方法，其特征在于：凝固层厚度达到 50-300mm时，停止对外铸坯外表面强制冷却。 A method for improving the self-retracting ability of a thick and large-section slab according to claim 1 or 2, characterized in that: when the thickness of the solidified layer reaches 50-300 mm, the external cooling of the outer surface of the slab is stopped.

4、按照权利要求 1所述的提高厚大断面铸坯自补缩能力的方法，其特征在于- 控制铸坯外表面冷却条件，根据铸坯表面实测温度及时对铸坯外表面进行保温或强制冷却，使铸坯外表面的温度维持在固相线以下 200-400°C之间，铸坯外表面凝固层处于低变形抗力的塑性变形区。 4. The method according to claim 1, wherein the method for controlling the self-retracting capacity of the thick and large section slab is characterized in that: the cooling condition of the outer surface of the slab is controlled, and the outer surface of the slab is insulated or forced according to the measured temperature of the surface of the slab. Cooling, the temperature of the outer surface of the slab is maintained between 200-400 ° C below the solidus line, and the solidified layer on the outer surface of the slab is in a plastic deformation zone with low deformation resistance.

5、按照权利要求 1所述的提高厚大断面铸坯自补缩能力的方法，其特征在于：芯部金属液同时凝固时，凝固收缩产生径向拉应力，拉应力作用于外表面高温凝固层，使已凝固金属发生塑性变形，由外表面向铸坯中心发生塑性移动，实现铸坯径向自补缩。 5. The method according to claim 1, wherein the core metal liquid solidifies at the same time, the solidification shrinkage generates a radial tensile stress, and the tensile stress acts on the outer surface to solidify at a high temperature. The layer causes the solidified metal to be plastically deformed, and plastically moves from the outer surface to the center of the casting blank to realize radial self-feeding of the casting blank.

6、按照权利要求 1所述的提高厚大断面铸坯自补缩能力的方法，其特征在于：所述高温脱坯，铸坯脱模温度大于 80(TC， 6. The method according to claim 1, wherein the high temperature stripping, the mold release temperature is greater than 80 (TC,

7、按照权利要求 6所述的提高厚大断面铸坯自补缩能力的方法，其特征在于：铸坯脱模温度优选为 850-1200°C。 7. The method of claim 6, wherein the mold release temperature is preferably 850-1200 °C.

8、按照权利要求 1所述的提高厚大断面铸坯自补缩能力的方法，其特征在于：铸坯高温脱模后进行缓冷，冷却速度小于 50°C/h。 8. The method according to claim 1, wherein the slab is subjected to slow cooling after high temperature demolding, and the cooling rate is less than 50 ° C / h.

9、按照权利要求 8所述的提高厚大断面铸坯补缩能力的方法，其特征在于：所述冷却速度优选为 10-30°C/h。 A method of improving the feeding capacity of a thick and large section slab according to claim 8, wherein the cooling rate is preferably 10 to 30 ° C / h.

10、按照权利要求 1所述的提高厚大断面铸坯自补缩能力的方法，其特征在于：铸坯脱模后，高温退火温度大于 800°C，高温退火温度优选为 850-1100 °C，退火冷却速度小于 50°C/h。 10. The method according to claim 1, wherein the high temperature annealing temperature is greater than 800 ° C and the high temperature annealing temperature is preferably 850-1100 ° C after the casting blank is demolded. , Annealing cooling rate is less than 50 ° C / h.

11、按照权利要求 10所述的提高厚大断面铸坯自补缩能力的方法，其特征在于- 优选为 10-40°C/h。 11. A method of increasing the self-shrinking ability of a thick section slab according to claim 10, characterized in that it is - preferably 10-40 ° C / h.

12、按照权利要求 1所述的提¾厚大断面铸坯自补缩能力的方法，其特征在于：该方法适用于厚度人于 400mm的连铸方坯或矩形坯，直径大于 500mm的连铸圆坯以及厚度大于 600mm的模铸宽厚板坯。 12. The method according to claim 1, wherein the method is suitable for continuous casting billet or rectangular blank having a thickness of 400 mm and continuous casting having a diameter of more than 500 mm. Round blanks and molded wide slabs with a thickness greater than 600 mm.

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