RU2032489C1 - Ingot mould for pouring steel ingots - Google Patents

Abstract

FIELD: ferrous metallurgy. SUBSTANCE: ingot mould has areas transient between the borders and limited by the curvilinear surface formed by two radius conjugated by a plane or by three radius. The middle area is directed opposite to the areas on the ends and is bent in the inner cavity of the ingot mould. The radius values of the areas on the ends make up 10%, and of the middle area - 15. ..20% of the inner width of the ingot mould in its middle part. EFFECT: facilitated manufacture. 2 dwg

Description

 The invention relates to metallurgy.

 The rounding angles of the internal angles of the molds are known, for example, the configuration of the internal rounding angles of the molds is made with one radius of size within 8-13 (on average 10%) of the reduced ingot thickness, this configuration is generally accepted for all types of molds in both domestic and foreign practice; the internal rounding angles of the mold are also made of one radius and also of a size within 0.1D (reduced ingot diameter), however, convexities (local tides) are added near the rounding angles supposedly to reduce angular hot cracks.

 The disadvantages of the known angles are as follows: the main surface defect of the ingot of calm steel grades is angular longitudinal cracks, the formation of which is associated with a radius of 3 rounding of the internal corners of the molds. A decrease in the radius of curvature increases the rate of crystallization of the crust in the corners of the ingot and reduces the tendency to form hot cracks under the influence of ferrostatic pressure of molten steel. However, there is a danger of the formation of angular longitudinal cracks in rolling due to the coincidence of the planes of the slack at the junction of the transcrystallization zones with the diagonals of the ingot. In addition, small rounding radii cause overheating and melting of corners in heating wells (KMK and MMK experience). With an increase in the radius of curvature, the risk of ingot damage by hot cracks in the corners of the ingots increases.

 The given limits of the sizes of the radii of the internal rounding angles of the molds, although confirmed by special studies, domestic and foreign practice, however, they do not eliminate the listed disadvantages, but only reduce them to a certain minimum. However, this minimum is so large that even with the recommended sizes of those radii, huge damage is caused in the form of marriage due to angular and transverse hot cracks on the faces of the ingots overheating of the corners of the ingots, reduced resistance of the molds, etc. that this damage is an insurmountable obstacle to the path so necessary to improve the quality of the metal, increase the productivity of steel mills by increasing the temperature of the metal and increasing the speed of its casting.

 The purpose of the invention is to eliminate hot cracks of both angular and transverse cracks on the ingots, as well as to reduce the weight of the molds and to increase their resistance.

 This goal is achieved by the fact that a new configuration of the internal rounding angles of the molds is proposed, namely that the rounding is performed not by one radius, but by three, with the middle of them being in the opposite direction. This configuration was developed and tested by new data on the mechanism of the formation of hot cracks at the corners and on the faces of ingots.

 So, if, according to previous tests, longitudinal hot cracks at the corners of the ingots form 3-10 minutes after the start of the formation of the primary crust, according to later studies it turned out that angular longitudinal and transverse hot cracks on the blooming ingots form in the first 10-15 seconds of crystallization primary crust with an equally early formation of a gap in the corners of the ingot. Moreover, the formation, as well as the loosening of the primary crust, does not occur suddenly with a continuous rupture with healing of cracks with liquid metal, but it is slowed down, since the decisive factor in their formation: the length of the gap in the corners (in the cross section of the ingot), which also forms at the time of formation of angular hot cracks, increases slow down.

 The cause of the formation of transverse hot cracks is the ingot hanging on its upper sections at a distance of 100 mm from the metal mirror due to the formation of a gap between the bottom of the ingot and the bottom of the mold, and also slowed down accordingly to the formation of a gap. Transverse hot cracks form mainly on the faces of the ingot, since gaps already appear in the corners. The depth of longitudinal and transverse hot cracks does not exceed 10-15 mm. Further deepening of hot cracks are shrinkage phenomena, expressed in the withdrawal into opposite cracks of adjacent sections of the ingot with a crack.

 In FIG. 1 and 2 show the proposed mold ingots for rail ingots weighing 6.8 tons

 The solid lines 1 represent the dimensions of the proposed mold, and the dotted lines 2 of the working one. Moreover, the aspect ratios of both dimensions of the molds are presented exactly to the scale. Both profiles have the same cross-sectional area, where the width of the mold 3 (740 mm) for the proposed mold is increased by size 4 (5 mm). Radius 5 is made equal to 10-12% of the reduced thickness of the ingot, and radius 6 is greater than radius 5 by 16-18%. Area 7 is compensated by two platforms 8, position 9 represents the area of the P-50 rail, and position 10 represents the area of the pipe billet with a diameter of 160 mm. The wall thickness along the faces of both molds is 177 mm. Position 11 depicts the excess area of the working mold in comparison with the proposed. This excess for one mold is equal to 800 kg.

 It is established that gaps in the corners are formed due to shrinkage in the direction of 12 of the primary crust of the ingot on its faces. Since in the proposed configuration of the internal angles of curvature, gaps are formed due to the shrinkage of only one face, the width of the resulting gap 13 will be two times or more less than the length of the prototype, since the length of the cutting crust is smaller. Therefore, angular hot cracks on the ingots will not form even at significantly higher metal temperatures and casting speeds.

 Since the primary crust 14 in the first 15-20 s from the moment of filling this horizon under the influence of the liquid phase 15 in section 16 will be pressed against the wall of the mold, and the presence of its bend will increase this pressure, then in section 16 the hanging of the already cast part of the ingot will naturally be larger than on the edges of the ingot. Since the formation of transverse cracks in section 16 is difficult due to its short width, there will be no transverse cracks on the faces of the ingot, which is also facilitated by the shorter width of the faces of the ingot compared to the prototype.

 The above-mentioned angular cracks of the ingots, which are formed in the first compressions of the ingot on blooming due to the coincidence of the diagonal planes of the ingot with the junction of the transcrystallization zones, will be eliminated, since in the proposed mold, firstly, the transcrystallization zones do not coincide with the diagonal planes of the ingot, and secondly , the transcrystallization zones themselves will have a smaller plane of slack. Transverse cracks on the faces of the ingot formed in the first passes of the ingot on blooming due to the reduction of the width of the faces compared to the prototype will also be eliminated.

 The physicomechanical properties of the metal will increase due to a more uniform ingot deformation during rolling less, compared with the prototype, the difference in the distance from the axis of the ingot between corners and faces, surface defects will also decrease, especially on pipe billets: torn from overheating of the ingot corners in heating wells, longitudinal cracks.

 It is known that during the heating of the mold the temperature of its corners (according to the prototype) is always lower than the edges. In the proposed mold, there will be no such temperature difference, which will reduce thermal stresses and at the same time increase their resistance by later formation of a heat network and longitudinal cracks.

 The manufacture of molds with the proposed configuration of the angles of curvature differs only in the additional work of the modeler of no more than one person-h for one model.

Claims (1)

 A SILICON FOR TASTING OF STEEL INGOTS, having faces and between them mating sections bounded by a curved surface, characterized in that, in order to increase the physicomechanical properties of the ingots and to reduce the formation of cracks during casting and rolling, longitudinal at the corners of the ingots, and transverse at the edges, the curved surface of the mating sections is made along two radii conjugated by a plane, or along three radii, the middle of the sections is directed oppositely extreme and concave into the internal cavity is stated gical, wherein the radius of the edge portions is 10% of the width of the mold at a middle portion, and the radius of the middle portion 15 of this 20% of the width of the mold.

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