JPS6120647A - Production of clad billet by continuous casting - Google Patents

Abstract

PURPOSE:To reduce the cost of production by heating cladding metals to a specific temp., supplying continuously said metals into a vertical mold, pouring a molten steel to the inside of the cladding metals and cooling forcibly the molten steel upon lapse of prescribed time. CONSTITUTION:The cladding metals 3a, 3b are continuously supplied into the vertical multi-stage mold 11 so as to contact with the inside surface of the mold. The metals 3a, 3b are formed by welding to a rectangular square cylinder and are heated to 400-1,200 deg.C preheating temp. by a quick heater 14. The molten steel 4 in a tundish 1 is poured through a nozzle 15 into the cavity formed of the metals 3a, 3b. The molten steel in the mold 11 is weakly cooled and begins to solidify in the upper stage part 11a. The molten steel is then quickly cooled in the lower stage part 11b of the mold to form an unsolidified clad billet 5 after the prescribed time. The billet is drawn while the billet is cooled by a cooling nozzle 21. The cost is considerably reduced by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing a clad slab by continuous casting.

[Prior art and its problems]

Generally, clad steel plates are manufactured by crimping a laminate material such as stainless steel onto a face plate using various processing methods such as rolling.

This method takes time and effort, and has the disadvantage of increasing the manufacturing cost of clad steel sheets.

Therefore, the inventor Alj proposed a method for manufacturing 91 pieces of cladding by continuous casting in order to make it possible to obtain clad steel plates at low cost, in the above-mentioned Japanese Patent Application No. 58-284, 9.
I proposed this as number 1.

As shown in FIG. 6, this proposed method for manufacturing ζ-clad slabs consists of placing a mold, for example, a pair of long sides together, in a vertical mold 2 provided directly under the tundish. While welding the material 3a and the pair of short-side mating materials 3b, the material 3a is continuously supplied vertically, and at the same time, the molten material is supplied from the tundish l to the air space surrounded by the mating material 4J' 13b in the mold 2. A44 is continuously injected to form an unsolidified clad slab 5 in which the outer surface of the unsolidified slab is welded to the mating materials 3a and 3b, and this unsolidified clad slab 5 is continuously pulled out from the vertical mold 2. , cooled,
Clad slab 1 For example, a three-layer clad slab having cladding materials on all four sides is obtained.

By rolling the clad slab produced in this way to a desired thickness, a clad steel plate can be easily obtained. If a thin clad slab is manufactured, it becomes possible to obtain a clad steel plate as it is without rolling it.

By the way, in the above manufacturing method, the long side side joining material 3a
In order to facilitate the straightening by the straightening roll 6 and the solution with the molten steel 4, the heater 7 is used to preheat the material, and it is also desirable to preheat the short side mating material 3b. Laminating material 3a.

The preheating temperature that makes it easier to weld 3b to molten steel 4 was not necessarily clear.

The present inventors discovered that, in the process of experimentally manufacturing clad slabs based on the above-mentioned manufacturing method using a small continuous casting test device, the preheating temperature of the cladding material supplied into the mold was equal to that of the base material. In order to manufacture clad slabs that greatly support the weldability between materials and have excellent weldability of the first laminate, the preheating temperature of the laminate and the timing of the start of hard cooling of the laminate must be appropriate. Knowledge of what must be done (7. Patent application 1984-284.
In the manufacturing method of No. 91, improper preheating or cooling of the laminate material may result in poor weldability of the laminate material. It is not possible to stably produce pieces.

[Purpose of the invention]

In view of the above points, the present invention makes it possible to stably produce a clad slab with excellent welding properties for one laminate. The object of the present invention is to provide a method for manufacturing clad slabs by continuous Uj forming.

[Summary of the invention]

In this invention, a composite material heated to a temperature of 400 to 1200°C is continuously fed vertically into a vertical mold provided directly below a tundish so that the outer surface of the composite material is in contact with the inner surface of the mold. .

At the same time, the molten steel in the tanditshu.

Inject into the inside of the laminate in the mold.

The method is characterized in that the molten steel is solidified and welded to the outer surface of the laminate, and then the laminate is strongly cooled once a predetermined time has elapsed.

[Structure of the invention]

As mentioned above, the present inventors have proposed the
Based on the manufacturing method of No. 8-28491.

In the process of experimentally manufacturing clad slabs using a small continuous casting test device, we found that the preheating temperature of the welding process and the start time of intense cooling largely control the weldability between the base material and the cladding material. I found out that.

Figures 3 (a) to (d) show the state of the interface between 1 laminate and molten steel when the laminate is supplied into the vertical mold of a small continuous casting test device at different preheating temperatures, determined by heat transfer calculations. 1
This is what is illustrated.

Here, 8 is the laminate material, 9 is the molten steel in the mold, 10 is the surface of the molten copper, and 21 is the liquidus line at the solidification interface (fB=o)
-fSld Solidus line of solidification interface (f, = 1.0) -T
is the preheating temperature of the laminate 10. Preheating temperature T of laminating material 8
i-] The temperature of the preheated laminate 8 is indicated when the molten metal level of the d steel reaches 1°.

FIG. 3(a) shows the case where the l-111 laminated material 8 was not preheated. The cooling of the outer surface of the laminated material 8 was determined by weak cooling such as air cooling, direct or indirect water cooling usually performed in continuous casting, and strong cooling at a secondary degree, but Figure 1 does not distinguish between these. It is illustrated.

In Fig. 3(a), the 1-phase gland 2s rising below the molten metal level 10 continues to rise as it goes in the slab drawing direction, and the interface between the laminate material 8 and the molten steel 9 reaches the melting temperature. Never.

Figure 3 (If the first laminate material 8 is not preheated from ml, the interface between the first laminate material 8 and the molten steel 9 will not reach the melting temperature even if the cooling of the first laminate material 8 is greatly relaxed. , therefore,
Although it is expected that the laminate material 8 cannot be welded to the base material formed from the molten steel 9, this has actually been confirmed in casting tests.

Fig. 3(b) shows the case where the first laminated material 8 is preheated to 400°C.
Figure 3(c) shows 1 when preheated to 1200℃.
Both of the laminates 8 were cooled slightly.

In these cases, the solidus line 2s enters into the laminate B in a predetermined area below the molten metal level 10, and the interface between the laminate 8 and the molten steel 9 reaches the melting temperature at point a or b, and becomes solid. A liquid coexistence state is created.

Therefore, when the first laminate material 8 is preheated to 400 to 200[deg.] C., it is expected that the base material and the laminate material will be well welded. However, when the 5th laminate 8 is preheated to 2010° C., the 1st laminate 8 melts and breaks, as shown at point C in FIG. 3(C).

Unsolidified clad slab cannot be pulled out. Therefore, in this case, it is necessary to strengthen the cooling of the outer surface of the first laminated material 8 when the strength of the first laminated material 8 is present.

Fig. 3(d) shows the case where the first laminate 8 is preheated to 1000°C. Here, the outer surface of the 1st laminate 8 is initially cooled gently to ensure that the 1st laminate 8 has the strength of half the thickness. 1 at point d
This depends on switching to strong cooling.

In Fig. 3(d), after the in-phase line 2s enters the laminate 8 at point e and the interface between the laminate 8 and the molten steel 9 reaches the melting temperature, the cooling is switched to strong cooling from point d. solidus line ys
has risen to 2, the melting of the laminated material 8 has stopped and recovery has occurred.

Therefore, in this case, the capacity of the phantom matrix and the dead material 8 can be sufficiently guaranteed, and there will be no problem in pulling out the unsolidified crust 1 piece.

Figure 4 shows the results of welding when a clad slab was cast using austenitic stainless steel 1sUs304 with a thickness of 5 ms as the cladding material and molten steel equivalent to machine structural steel 40 as the base metal. The start line island and the limit line L2 for the occurrence of fusing are illustrated with respect to the preheating time of one laminate material and the elapsed time t after pouring the molten steel.

In addition to air cooling, the primary cooling of the outer surface of the laminated material 1 was performed by various cooling methods such as a method using a graphite resistant material, a method using a high melting point metal body with an indirect weak cooling structure, or a method using a cermet.

Here, the start of welding at the welding start line 11 means that the interface between the laminate material and the molten steel becomes molten salt J and a solid-liquid coexistence state is reached, and the limit of fusing occurrence at the fusing occurrence limit line 12 means 1. This indicates that the outer surface of the laminate has reached the melting temperature and has lost its rigidity.

Therefore, the preheating temperature T of the laminate material and the elapsed time t after injection of molten steel as the start time of strong cooling of the laminate material 1 are defined as
If a suitable selection is made within the region A between 1 and 12, a clad slab with excellent weldability for the 1st laminate material can be obtained.

5US304 as the laminating material and 40US as the base material.
Figure 5 shows a microscopic photograph of the metallographic structure of the joint surface between the base material and the cladding material of a cladding piece produced using molten steel of KSi-Ae killed steel using a small continuous casting test device. , ), shown in (b).

FIG. 5(a) shows the preheating temperature T represented by point f in FIG.
It can be seen that when the cladding material is preheated and strong cooling of the cladding material is started at the elapsed time t after pouring the molten steel, the cladding material and the base metal are welded together. Figure 5(b):.

When the cladding material is preheated to the preheating temperature T indicated by point 2 in Fig. 4, and strong cooling of the cladding material is started at the elapsed time t after pouring the molten steel, the cladding material and the base metal are completely welded together. I know that there is.

Based on the above, in this invention.

The preheating temperature of the laminated material is 400 to 1200°C.

As long as the combination of base material and laminate is a normal combination of low-, medium-carbon, and low-alloy steel for the base material and high-carbon steel, high-alloy steel for the laminate, the temperature is 400 to 1200℃. This is because the weldability of the laminate can be guaranteed at a preheating temperature of . If the temperature of the laminated material is less than 400°C, the welding properties of one laminated material cannot be obtained.

However, when the temperature exceeds 1200°C, the tensile strength It of the first laminate material decreases significantly, causing a problem that the first laminate material deforms or breaks.

In this invention, the cooling start time of one composite material is set after a predetermined time has elapsed from the injection of molten steel;
The interface between the laminate and the molten steel reaches a melting temperature, and a solid-liquid coexistence state is sufficiently created.

It is necessary to determine the point at which the stiffness of the laminate will not be lost forever. In this case, the timing at which the interface between the 1st laminate and the molten steel reaches the melting temperature depends on the preheating temperature of the 1st laminate, the thickness of the laminate, and the molten steel injection conditions (molten steel temperature at the time of pouring, molten steel temperature at the pouring section, etc.). The stirring intensity of the molten steel) and the type of combination of the base metal and the cladding material vary, so the timing to start cooling the cladding material is determined by taking these into consideration.

FIG. 1 is a detailed explanatory diagram of the present invention.

In Fig. 1, 1] is a rectangular vertical multi-stage mold installed directly under the tandish, and 3a is the mold 1.
1 is a long side lining material that is continuously supplied to the mold 11 so as to be in contact with the inner surface of the long side, and 3b is a short side lining material that is continuously supplied to the mold 11 so as to be in contact with the inner surface of the short side thereof. It is. A pair of long side mating materials 3a and a pair of short side mating materials 3
b are each bent downward at right angles by straightening rolls 6 and 12, and then formed into a rectangular square cylinder by welding with a welder 13, and then heated by a heating coil of a rapid heater 14.
It is heated to a predetermined preheating temperature of 400 to 1200°C and guided into the mold coco. Note that 7 is a heater that heats the long side (1411) laminate material 3a to make it easier to straighten, and if a similar heater is used to also heat the short side laminate material 3b, 75:
good.

When the laminate materials 3a and 3b are guided into the mold ll.

At the same time, the molten steel 4 in the tongue tissue 1 passes through the injection nozzle]5 at the bottom of the tongue tissue 1.

The laminate material 3a +' 3b is injected into the air space formed.

Note that an inert gas is introduced from the pipe 16 into the air space formed by the composite materials 3a and 3b to reduce the oxygen concentration to 1
It is preferable to prevent the inner surfaces of the joints 4i' 3a and 3b and the molten steel on the molten metal surface from being oxidized.

The mold 11 has an upper part 1 that allows the inside of the mold to be cooled slightly.
j, a, and the lower part 111 that allows strong cooling of the inside of the mold.
). For such a mold.

As shown in Fig. 2(a), the upper part is made of an indirect water-cooled ceramic mold 17, the lower part is made of a grid made of cast iron, etc., and a spray nozzle is attached to the back of the mold.
As shown in FIG. 2(b), both the upper and lower parts are formed of a grid 18, and a spray nozzle 19 is provided on the back side of the grid so as to be movable up and down. A mold having a structure whose position is adjustable can be used.

In FIG. 1, reference numeral 20 denotes an electromagnetic coil for stirring the molten steel near the molten metal surface in the mold 11.

The molten steel injected into the air space formed by the cladding materials 3a, 3b in the mold 11 is transferred to the upper stage 1 where the mold 9 is slightly cooled.
．． It starts to solidify loosely in la. At this time, the laminate materials 3a and 3b that have come into contact with the molten steel reach a melting temperature at the interface with the molten steel and undergo a solid-liquid coexistence state, so that they are welded to the shell in which the molten steel has solidified. Next, the molten steel is strongly cooled in the lower part 11b of the mold 11, and solidification progresses rapidly to form an unsolidified clad slab 5 having the first lamination materials 3a, 3b on the surface.

The unsolidified clad slab 5 that has passed through the lower part 11b of the mold 11 is then sprayed with cooling water from the cooling nozzle 2 installed below the mold 11.

It is pulled out from the mold 11 by the pinch rolls 23 using the support rolls 22 as a guide. The unsolidified clad cast piece 5 pulled out from the mold 1 is as follows.

After it is completely cooled, it becomes a clad slab whose entire surface is covered with laminated material.

By rolling the clad slab produced in this manner to a desired thickness, a clad steel slab can be easily obtained, and a thin clad slab can be manufactured.

It becomes possible to obtain a clad steel plate as is without rolling.

〔Effect of the invention〕

As explained above, according to the present invention, a clad steel plate can be easily obtained, the manufacturing cost of clad steel slabs can be significantly reduced, and clad slabs can be stably made and welded easily. can be made into a good one.

[Brief explanation of drawings]

FIG. 1 is a detailed explanatory diagram of the present invention, and FIG. 2 (a). (b) il'' 1. Schematic sectional views of the molds used in the method of the present invention, Figures 3 (a) to (d) are explanatory diagrams showing the state of the interface between the laminate and molten steel, and Figure 4 6. ':1,
Graph illustrating the welding start line 1.1 of the mounting material and the fusing occurrence limit line 12, Figure 5 (aJ, (b)) 1l-1: Showing the metallographic structure of the joint between the cladding material and the base material. Fig. 6 is an explanatory diagram of the method of mounting.
・-Heartside 41111 combined month, 4,9...melting; steel. 5. Uncured 1. 'rl clad casting6. ]2... Straightening roll. Piece 7...-heater. 8. Laminating material, 10... Hot water surface. 11.Multi-stage mold-11a...upper stage part. IFb Lower part, 13...Welder, 14.Rapid heating'AL 15...Injection nozzle. 2]・Spray nozzle + 22...Support roll. 23. Pinch roll.

Claims (1)

[Claims] There are 40
A cladding material heated to a temperature of 0 to 1200°C is continuously supplied vertically so that the outer surface of the cladding material is in contact with the inner surface of the mold, and at the same time, the molten steel in the tundish is fed into the mold. The molten steel solidifies to form an unsolidified clad slab welded to the outer surface of the composite material, and then the unsolidified clad slab in the mold is injected into the molten steel. A method for manufacturing a clad slab by continuous casting, characterized in that the composite material is strongly cooled after a predetermined time has elapsed from the time of pouring.