SU1696015A1 - Method of producing thick-gauge plate - Google Patents

Abstract

The invention relates to metallurgy and can be used in the rolling of thick sheets and slabs of horizontally cast ingots. The purpose of the invention is to reduce the metal consumption by reducing the thickness of the layer removed during stripping. The method includes casting a horizontal ingot, its pre-deformation, stripping and rolling. New in the method is that before stripping the ingot is compressed on the thickness of the segregation layer, which includes an increased content of sulfur, phosphorus, carbon and non-metallic inclusions. This allows the use of heat hardened ingot, reduce the cost of redistribution, reduce transport costs. 3 il.

Description

The invention relates to metallurgy and can be used in the rolling of thick sheets and slabs of horizontally cast ingots.

The purpose of the invention is to reduce the metal consumption by reducing the thickness of the layer removed during stripping.

In a horizontally cast ingot there is no profit, and as a result of the characteristics of its solidification of liquates, nonmetallic inclusions, shrinkage defects of origin are concentrated in a certain surface layer along the upper face of the ingot, which is the rolling plane.

The fire stripping machine (MOH) does not completely remove the defective layer, therefore, at present, horizontal ingots after crystallization and subsequent cooling are sent to the mechanical workshops for gouging the mechanical removal of the upper layer, which drastically reduces the efficiency of the technological chain for the production of steel plates. It is not possible to use the heat of the hardened ingot and realize the heating for rolling from the hot end, which increases the cost of heating and the loss of metal with waste in the furnace. There are additional costs for transporting the ingot and operating the mechanical equipment. In addition, due to the deflection of the head surface of the ingot during shrinkage during the crystallization process, when cleaning the defective layer, the healthy metal is also removed from the side faces of the ingot.

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Reducing the costs and losses of metal in the production of thick sheets of horizontal ingots can be achieved by using a fire stripping machine located in the mill line to remove the defective layer after first reducing its thickness.

The rolling of ingots in roughing passes is characterized by a considerable unevenness in the distribution of the deformation over the height of the roll and its localization in the surface layers, which leads to their preferential stretching and thinning.

In this connection, it is proposed to pre-roll the roll to intermediate thickness, which will provide a reduction in the thickness of the defective layer and the possibility of its complete removal on the fire stripping machine. At this stage, the ingot should be reduced to the thickness of the segregation layer, the layer with a high content of sulfur, phosphorus, carbon, and non-metallic inclusions. Its thickness can be determined based on specific casting conditions.

With a smaller total reduction, the defective layer does not thin out enough, its removal to the Ministry of Health requires several passes, which leads to cooling of the bottom surface of the roll and creates a number of difficulties for its further rolling-km (bend of the roll, cracks on the surface). With a larger total reduction at the preliminary rolling stage, the risk of crack formation on the upper surface of the roll (corresponding to the head surface of the ingot) increases. Significant contamination with sulfides of this zone sharply reduces the ductility of the metal. When rolling, cracking of the defective layer is observed. With a significant total reduction at the pre-rolling stage, these cracks propagate into a healthy metal (due to the presence of tensile stresses in the contact zone and the presence of stress concentrators - these microcracks), which ultimately can lead to the rejection of the rolled sheet.

As a result of the stripping operation in the rolling flow, the cost of machining and additional inter-workshop transportation of ingot is eliminated for the MOG, it is possible to heat the ingot for rolling directly after crystallization and extraction from the mold, from hot land, which reduces costs on heating. Metal saving is achieved by reducing the losses during stripping (a healthy metal passes from the periphery of the head surface to tal of the roll and is not removed during stripping) and decreases the metal loss in the furnace due to a decrease in the heating time of the ingot while hot.

FIG. 1 schematically shows the production technology of thick sheets of the proposed method; Fig 2 - sulfur print made in the laboratory

ingot conditions, cross section; in FIG. 3 - the same for roll rolled from this ingot.

Horizontal ingot 1 with the thickness of NSL with defective head layer with the thickness of NP

5 and a segregation layer of thickness Hc is pre-compressed on a rolling mill of 2 HP; the thickness of the segregation layer is not of intermediate thickness —He; then the thinned defect layer hn is removed by

0, the fire stripping machine 3 and (figure 1) carry out further rolling to the required dimensions.

The proposed method was tested in laboratory conditions. A 53x120x260 mm rod was cast in a horizontal tray, the head surface of which was artificially saturated with sulfur to simulate a real picture of the distribution of sulfur over the horizontal ingot section. Wherein

0, the thickness of the segregation layer is 12 mm. and the thickness of the defect layer Hn is 4 mm. There is no small size of ingot with bent concaveness on the upper face. Sulfur print removed

5 cross-sectional ingot (schematically shown in figure 2),

Then, after heating to 1250 ° C, the ingot is rolled to a laboratory mill 340. In the process, the Lrokatkm visually observes the state of the head surface of the roll. At a thickness of 41 mm, corresponding to compression on the thickness of the segregation layer, the upper edge of the roll begins to crack. Examination of specimens that are scanned with a large reduction shows the penetration of surface cracks into a healthy metal. After rolling with a compression equal to the thickness of the segregation layer (12 mm), the thickness of the surface defect layer is 0.6-0.9 mm. A defective layer of this thickness (taking into account the scale of the simulation) can be removed on the fire stripping machine in the rolling stream (Fig. 3). Reduced metal loss compared to

5, by a known method, is achieved by reducing waste during stripping and metal loss when the ingot is heated for rolling.

Thus, the proposed method allows to improve the processability of the process and reduce metal losses.

Claims (1)

Invention Formula A method of producing thick sheets, including continuous casting of an ingot with a segregation layer, its preliminary deformation at rolling temperatures, stripping and rolling, characterized in that, in order to reduce metal consumption by reducing the thickness of the layer removed during stripping, the preliminary deformation is carried out by the amount of segregation lay A L X Lsrie .1 eri g 2 fig.Z