30results about How to "Improve center segregation" patented technology

The invention relates to a method for improving center segregation of an extra thick slab with a thickness of 400mm, and belongs to the technical field of continuous casting of steelmaking. Degree of the center segregation of the extra thick slab with the thickness of 400mm is improved by a dynamic soft reduction technology, so that rating of the center segregation is free from above C2.0 so as to improve the inner quality of the extra thick slab. The specific steps are as follows: determining an optimal reduction position and an optimal rolling reduction: after determining the optimal reduction position, testing different rolling reductions in the reduction area: 5-6mm and 6-8mm and applying a certain rolling reduction of 0-0.5mm to a solid phase area; and combining lower power rating and C, S segregation ratios to determine the optimal rolling reduction.

The invention belongs to the technical field of metallurgy, and in particular relates to a spheroidizing annealing method for Cr and Mo steel with a sheet type microstructure. The spheroidizing annealing method comprises the steps of putting a Cr and Mo steel rolled product sample into a heating furnace, heating to 700-720 DEG C, preserving the temperature for 4-5 hours, then performing furnace cooling to 580-600 DEG C, taking out the Cr and Mo steel rolled product from the furnace, and cooling to room temperature, wherein the microhardness of the Cr and Mo steel rolled product subjected to spheroidizing annealing is 162.20-175.35HV, and the microstructure of the Cr and Mo steel rolled product consists of granular carbides dispersed on a ferritic matrix; the granular carbides have spheroidized structures in the level 5-6. According to the method, sub-medium temperature is preserved for certain time, and then the furnace cooling time is controlled, so that spheroidizing-annealed steel with high performance is obtained. The high preserved temperature is lower than the preserved temperature of the original technology, and the heat preservation time is shortened by almost three times, so that the energy consumption is obviously reduced, and the spheroidizing annealing efficiency is improved; the hardness of the steel subjected to the spheroidizing annealing technology is obviously reduced, the structure of a spheroidal pearlite is dispersive and fine, and the spheroidizing rate is high; the Cr and Mo steel subjected to spheroidizing annealing is high in cold heading performance and has a good application prospect.

The invention discloses a steel plate having a thickness of 150 mm, a low compression ratio and a low Z-direction performance, and a production method thereof. The steel plate comprises, by mass, 0.12-0.17% of C, 1.25-1.70% of Mn, 0.002-0.009% of S, 0.008-0.020% of P, 0.30-0.41% of Si, 0.032-0.042% of Als, 0.038-0.045% of Nb, 0.015-0.030% of Ti, 0.0030-0.0050% of N, and the balance of Fe and otherinevitable impurities. The production method comprises the following steps: smelting, continuous casting, heating, controlled rolling and controlled cooling. The rolling compression ratio of the produced steel plate is 1.77-1.80, the production method has the advantages of low production cost and fast production pace, and the steel plate has the characteristics of high flaw detection qualified rate, excellent mechanical properties and high performance uniformity of the microstructure in a thickness direction.

The invention discloses a method for improving the segregation and shrinkage of the center of a square and round billet; when a cast billet is cooled, the growth rate of solidified shells of the cast billet in an inner arc direction and an outer arc direction is relatively higher while the growth rate of solidified shells of the cast billet in a left side direction and a right side direction is relatively lower through a cooling method according to which the cooling strength in the inner arc direction and the outer arc direction of the cast billet is consistent, the cooling strength in the left side direction and the right side direction is consistent but the cooling strength in the inner and the outer arc directions is higher than that in the left and the right side directions, so that a liquid core on a solidified tail end of the cast billet is a rectangular area which is squashed in the inner and the outer arc directions and elongated in the left and the right side directions. According to the method for improving the segregation and shrinkage of the center of the square and round billet, because segregation solute elements and the distribution methods of solidification and shrinkage are controlled, the center of the cast billet is prevented from being segregated and enriched in a small area, so that the segregation and shrinkage of the center of the square and round billet and other continuous casting billets with similar width and thickness of cross sections are effectively improved, the effect is significant and stable, the use is simple and easy, the cost is low, and the cost performance in implementation is high. Simultaneously, a dynamic slight compression technology in continuous casting and a tail end electromagnetic stirring technology can be implemented.

The invention belongs to the technical field of metallurgy and particularly relates to a rolling process beneficial to spheroidizing annealing of a Cr and Mo steel. The rolling process is carried out according to the following steps of: carrying out cogging, rolling and spinning on a continuously cast steel billet; then always carrying out heat preservation to about 300 to 350 DEG C on a roll table cooling line and carrying out coil collection so as to obtain a Cr and Mo steel rolled product. According to the invention, by cogging heating control, steel rolling temperature control and after-rolling cooling control, segregation at the position of one second of R and center segregation are improved, grains are refined and growth of abnormal grains is avoided. Meanwhile, generation of large granular ferrite and pearlite is controlled, martensite is controlled below 35 percent; tissues mainly comprising bainite is formed, and carbide of the tissues is more uniformly distributed on a matrix. Moreover, according to a product produced by using the process, time of spheroidizing annealing is greatly shortened, an annealing process is simplified and spheroidized cementite is more dispersively and finely distributed.

The invention discloses a preparation process of composite casting blanks for a high-toughness thick steel plate. The preparation process adopts continuous casting blanks with different furnace numbers, the same steel grades and different carbon contents to compound so as to meet the requirements for overall strength and core toughness, thus the composite continuous casting blanks for an extra-thick steel plate with high surface quality and excellent core impact toughness are obtained. The low carbon design of an inner layer greatly improves the metallurgical quality of the central portion andprovides strong support for improving the toughness of the center and the whole. The high carbon design of an outer layer provides a carbon source for the whole compositions to ensure the whole strength, the uniformity of the compositions is achieved through diffusion, finally the whole compositions with both toughness and strength are obtained, and the occurrence rate of surface cracks is reduced.

The invention discloses a non-steady state continuous casting process capable of damaging a small steel ingot structure, and belongs to the technical field of metal material preparation. A drawing velocity is based on the conventional drawing velocity Vo, and is vertically fluctuated at small amplitude in a certain period T, namely V=Vo+a; and after continuous casting is started normally and becomes stable, a certain conventional drawing velocity Vo is determined according to a superheat degree, the drawing velocity is improved to Vo+a, billets are continuously drawn for time of T1, the drawing velocity is reduced to Vo-a in time of T3, the billets are continuously drawn for time of T2, and the drawing velocity is improved to Vo+a in time of T4 to complete a billet drawing period T. The non-steady state continuous casting process has the advantages that: the small steel ingot structure can be damaged and dendrite is inhibited from bridging, so that the compactness of continuous castings is improved, a non-steady state continuous casting process with center segregation is improved, and the non-steady state continuous casting process is suitable for continuous casting production lines for square billets, plate billets, round billets and the like.

The invention provides a method for reducing center segregation of a low-alloy steel continuous casting billet. The method aims at solving the problem that the qualification rate of internal segregation of the low-alloy high-strength steel casting billet is low. The method comprises the following steps that firstly, according to continuous casting billet production data of a target continuous casting machine, a carbon equivalent range of a target steel type continuous casting billet with qualified center segregation of the target steel type continuous casting billet is obtained through analysis, the component content of the target steel type continuous casting billet is subjected to back calculation, and the optimal molten steel component content range corresponding to the carbon equivalent range of the target steel type in production and the optimal pouring parameter range of the target molten steel are optimized; and therefore, according to the optimal component content range and the optimal pouring parameter range, the low-alloy target steel type continuous casting billet with qualified center segregation can be produced. The molten steel components and the pouring parameters are optimized according to the carbon equivalent range, the production conditions for preparing the target steel type continuous casting billet with qualified internal segregation quality can be found out more accurately, and therefore the center segregation of the low-alloy steel continuous casting billet can be effectively improved, and the internal segregation quality of the low-alloy steel continuous casting billet is improved.

The invention discloses a continuous casting process for producing free-cutting steel through a converter, and relates to the technical field of steel production, full protection pouring is adopted for continuous casting, long nozzle argon seal protection is adopted from a steel ladle to a tundish, submersed nozzle protection pouring is adopted from the tundish to a crystallizer, a covering agent is used for molten steel in the steel ladle and the tundish, and covering slag is used in the crystallizer; during pouring, a crystallizer is used for electromagnetic stirring, secondary cooling, vibration and tail end stirring parameters are controlled, and the casting speed of a continuous casting billet and the tundish molten steel temperature are controlled. By optimizing the continuous casting billet cooling process, the quality of the free-cutting steel can be effectively improved on the premise that the cost is not increased, and the rolling defects of the continuous casting billet are overcome.

The invention discloses a preparation method for high-quality continuously cast mother billets of a plastic mould steel extra-thick plate. The preparation method is characterized in that in a continuous casting process, billet pulling speed is controlled to be 0.80m/min-0.90m/min; solidification end is heavily pressed down; and press-down amount is distributed according to a solid phase rate under light pressing and heavy pressing. The preparation method disclosed by the invention improves internal quality of cast billets by a solidification end dynamic heavy-pressing technology, so that the center segregation defect and the center porosity defect of cast billets are improved; under the target of producing the extra-thick plate with specification of 120 mm (compression ratio only being 2.12 to 1), internal quality of a flaw detection thick plate with a low compression ratio is effectively improved, and a flaw detection qualification rate of the flaw detection thick plate with the low compression ratio in a production process is controlled to be 99% or higher. Cast billets industrially produced by the method are good in effect after being implemented, and can efficiently meet use requirements of mould steel.