JPS58167060A - Method and device for production of thin steel sheet - Google Patents

Abstract

PURPOSE:To produce a thin steel plate free from segregation by casting an ingot of a specific thickness or below by using a continuous casting machine wherein the coefft. of solidification rate is in the range of a specific value and subjecting the same continuously to rolling and finish rolling so as to roll the same to the specific thickness or below. CONSTITUTION:Molten steel is supplied from a tundish 1 into a twin belt type casting machine 2 wherein the coefft. of solidification rate is 15-25mm./min<1/2> to cast an ingot having <=80mm. thickness. The ingot is further cooled to solidify in a secondary cooling zone 2, whereafter the ingot is drawn with punch rolls 4 and is cut to a desired weight and length with an ingot cutter 5. The cut end face of the cut ingot is corrected under hot working with a corrector 6 for the cut end of the ingot. The cut ingot is fed to a device 7 unifying the ingot temp. to make the ingot temp. uniform, whereafter the ingot is passed through a broadside rolling down device 8 for the ingot and a hot finishing mill 9. A thin steel sheet of <=26mm. thickness is thus obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for forming molten steel into a straight-thin hot rolled plate.

Continuous casting has many advantages over the traditional one-block process and is rapidly gaining popularity. however.

There are four problems with the continuous casting method. First of all.

Current continuous casting requires a reduction of more than a light minute in order to satisfy the properties required for the product, so a slab of thickness is cast and hot rolled using this material. In addition, casting equipment investment and heat III Yanshun-investment are i! Second, because the time required for solidification is long, the quality of the slab deteriorates due to increased segregation of slabs, growth of non-metallic inclusions, growth of 1% bubbles, etc. That's true.

The second point above is a problem that can be overcome by performing continuous solidification, and point s1 can also be solved by setting the thickness of the slab that can provide the necessary thickness when performing rapid solidification. It should be done. In addition,
The fifth iii is the mechanical properties of the steel plate on the vertical axis, and the rolling ratio (if the thickness of the rolled v1ta is 8, kl, then the rolling ratio is hl/h)
a) and hl when ht=80■
is plotted on the horizontal axis and shown in 7.

(see the same figure), it can be seen that the necessary rolling reduction ratio of 50 is sufficient.

This way of thinking has already been applied to metals with a low melting temperature and a thermal conductivity of O+%, such as steel and aluminum, but it is thought that it is possible to use public funds for steel, and its specifics are No specific methods and devices have been proposed.

In other words, in the case of -, the melting temperature is high and the thermal conductivity is low, so rapid solidification is difficult and there are problems such as generation of segregated parts, and the melt is directly turned into a thin slab! I! It is considered difficult to cast for a long time.

The present inventor has repeatedly conducted research on directly casting Kll steel into thin slabs under the above-mentioned actual conditions, and has discovered that it is possible under certain conditions, and has arrived at the present invention.

That is, one object of the present invention is to propose a method for manufacturing a thin laminate plate that can prevent segregation of slabs as much as possible, and a second object is to provide an economical apparatus for use in the method. It is something that When the base melt solidifies as shown in the example and experimental results graph shown in the following 1 illustrative diagram, the final solidification position (center position of the slab) where the solute components are concentrated and a segregated area is generated. What is the degree of this central segregation?

It varies depending on the solidification rate and slab thickness. 11211■
Shizuka 25. ,,/m ” fA, □@L, a-all is the range in which segregation can be ignored.Here, the center segregation degree (χ
/y) was determined as shown in Figure 6.

χ indicates 5■/I'', ◎ of IW sample analysis, and V indicates am of ladle analysis.

Sukawa5. When solidifying, □゜2゜-/, i0 machining, □ casting, it is possible to cast a slab with a thickness of 80- or less and cracking during segregation.

As a continuous casting machine that continuously casts such thin slabs (80 mm or less) at high speed, there are two types of continuous casting machines that can be considered: the low # Liebe A/) lin continuous casting machine and the twin bell) lin continuous casting machine, but the W-Tliebe v) [Continuous casting machines are uniquely suited to hold wide sheets of equal thickness;
The thickness of the slab tends to fluctuate, and the rotor is huge, making it difficult to control the velocity.On the other hand, continuous casting has fewer drawbacks such as upper ε and is suitable for casting wide thin slabs. I am sending.

By the way, in the operation of the continuous casting machine.

The surface quality of the slab is affected by the belt movement speed (Vs) and the supply rate of the molten metal.No. 3 rI!J is a graph of the experimental results when the molten metal is molten steel. ”, and “・” means that the slab Table 1 properties are “
"Poor" and "O" indicates the state of molten steel breakage.As is clear from this table, the surface properties of the slab are "good" when it is below the one-dot line, which means that molten steel breakage is not likely to occur. While preventing v@ -Vt ≦ Vs X 1,5
It is only necessary to operate so as to satisfy the equation ``-0.

Furthermore, in the operation of a twin-belt continuous caster, the slab width (W
The relationship between l) and the molten metal supply width is also a major factor that influences the surface properties of the slab 11. 841g is a graph of experimental results when the molten metal is molten steel, and the cases depending on the operating speed (2 copies) are collectively displayed. Immediately, “○” or “・” means U=5
tw in moderation of %/-.

In the case of continuous casting over a period of 40 centimeters, "Δ" or "mu" indicates the case of continuous casting at a speed of U-10sga%- at t=20w. The condition is good and the condition is "poor", and the following operating condition formula is derived from the figure.

Wt--≦150 hours・・・・・・・・・■or.

! L You can operate a twin belt rotary casting machine.

It should be noted that the effective length of the cast is preferably 5 m or less from a practical point of view. The belt can be placed on the slab once it has completely solidified.
It is necessary to keep the solidified shell of the slab above a certain value in order to cope with bulging caused by K.

For example, when casting a slab with a thickness of 70 cm by tilting the continuous casting machine at an angle of 25 m, it is necessary to secure a hardness iii* of 1125 m5. To achieve this, the cooling capacity of the primary cooling zone of the twin-belt continuous casting machine is strengthened.

Thus, twin bee A/ ) l [Thickness 80 mm by continuous casting machine.
(2) The following slabs are cast and flowed through the apparatus of the present invention shown in No. 111, and finally become hot-strength rolled plates of 26 or less.

That is, Fig. 1 is an overall schematic diagram of the apparatus of the present invention, (υ is the tundish of the molten steel supply device, (!) is the twin belt continuous continuous caster, (3) is the secondary cooling zone, and (4) is the pinch roll. , (5) is a slab cutting machine, (a) is a slab anst repair machine,
(γ) is a slab temperature equalization device, (8) is a slab width control device, (9) is a hot finishing rolling mill group, and Masu is a rolled steel plate cutting device. The following will be explained in detail along the flow of the slab.

The slab that is suitable for the belt is further cooled and solidified in the secondary cooling zone (II), but bulging also occurs in the cooling zone (3), so the roll pitch is 150W and the secondary cooling zone is Following (3), the pinch rolls (4) arranged in a round shape to pull out the slab are the twin bearing 7) IL continuous casting machine (2).
It is driven approximately in synchronization with the vehicle speed.

Next, the slab fin cutting machine (5) located at the ninth position for cutting the slab into the desired stacked length and length i5 may be either a gas cutting machine or a saw lid cutting machine, but if the object to be cut is thin Because it is a slab, it must be cut!
With 1ftWi, slag adhesion and cross-sectional deformation inevitably occur, so a primary cast slab cut surface correction machine (6) is indispensable. That is, the slab cut surface correction machine (6) is arranged to hotly apply a solvent, cut, and straighten the cut end surface of the slab.

By the way, the twin belt warm continuous casting machine (2
), as mentioned at the beginning, is driven at a higher speed than conventional casting machines, and as a result, the overall temperature of the slab is high and the temperature difference between the surface and the inside is kept low. Since it is a thin slab with a thickness of 80 mm, it is unavoidable that both ends of the slab (as well as the center) will be at low temperatures. A temperature equalization device (7) is provided.

The heating by this slab temperature equalization device (7) varies depending on the type of ilN, but it is necessary to heat the slab to a temperature of 960°C or higher when rounding the central part of the slab to about 950°C.

Note that 9 (not shown) is an optical or electromagnetic device installed between the cut surface correction machine (6) and the slab temperature equalization device (7) in order to check the surface texture of the slab and ensure universal quality. It is desirable to install a slab surface inspection device.

In this way, the temperature is made uniform and the round slab is transferred to the slab width retainer device (
8] It is rolled by the hot finishing mill group (9), cut by the rolled steel plate cutting device (to), and then wound up as a hot rolled plate or carp V, which is shipped as is. At this point, the slab width control device is used, which is impossible because the thickness of the slab is extremely thin. can get.

Note that in the method of the present invention, the solidification rate coefficient is 15 to 25.
wm7b + and the thickness is set to 80- or less because in this range, segregation in the slab becomes negligible.

As explained above, the method of the present invention involves casting thin slabs at high speed and rolling them continuously to produce products. 〇－
Because of the following, it is possible to obtain slabs with low segregation sufficient to be rolled and manufactured into products, and the slab can be easily manufactured into products. Since it is considerably thinner than conventional continuous casting parts, the load on the cutting machine and other equipment is reduced, extending the life of the equipment, and it also eliminates the need for rough rolling rolls, which were previously considered indispensable. This method has the great advantage of being able to significantly reduce equipment investment, as well as being able to operate at high speeds since it is a method of casting at high speed and continuously rolling nine thin cast slabs into 11 products.

In addition, in the apparatus of the present invention, a cast slab cut surface correction machine is installed in the slab cutting machine, and the slab surface properties can be maintained by normalizing the sludder adhesion and cross-sectional deformation that occur due to the cutting of thin slabs. is,
A slab temperature equalization device is placed on the key of the slab width control device, which eliminates the temperature difference between both ends of the slab and the center, which occurs due to the thin slab, allowing smooth rolling of the slab. Many specific 4# methods such as those performed in

[Brief explanation of the drawing]

1st WA is an overall schematic diagram of the apparatus of the present invention, Figure 112 is a graph showing the relationship between solidification rate coefficient and slab thickness with respect to segregation,
FIG. 3 is a graph showing the relationship between surface texture and sliding speed and molten steel supply rate, and FIG. 4 is a graph showing the relationship between surface texture and slab width and molten steel supply width. msm
is a graph showing the relationship between mechanical properties and this.
The figure is a graph showing the relationship between central segregation degree and frequency. (1) is a tanditshu, (1) is a twin belt sump continuous caster, (a) is a secondary cooling zone, (4) is a pinch au, (!
t) is a slab cutting machine, (6) is a slab cutting surface correction machine, (η is a slab temperature equalization device, (8) is a slab width retainer device, (9)
11I finishing thick rolling machine, - is rolling track cutting device. Figure 5 Figure 6 I place IL (Xh) Figure 4 @ Yua Ni (Wt) beak. Procedural amendment (set 11, Showa 5s, ■Mon! 0, Director General of the Patent Office, 1, Incident indication i8wati'1 year tatami patent application No. 1101314 #2, issue 91
Thin steel in IO41 - 〇 Follow-up method Warping method O device 3, Relationship with the case of the person making the amendment Applicant address Osaka Liao, Osaka city Higashi-ku Tori Is Ding 111 Qiao Di Mr. Hat name) (211) Sumitomo Metal Works leprosy rod Shikisha 4, generation
Rijin 5, date of Showa year month
Contents of the date amendment tl) Amend the patent - Soku no Sou - to commute to the attached sheet (1)
I'm happy with my book! In the 7th line of ilaig, the phrase "by the hot water supply bay 11" is corrected to "by the molten steel supply speed (vm)". (4) On the 18th line of the same page in the same book, the text "Relationship with molten metal supply" is corrected to "Relationship with Minato Steel Supply Conduit (Wl)." (4) Replacing the phrase “iirUml■/-” on page 6 of the circular with “vl-1 earthquake/-”
” he corrected. (5) Same book, same page 4 lines 1irtrmloms/-4
Correct the statement to rv1mlos/ml. -(D) A certain meeting, r!tx1o・≧10-...■
1” is corrected. ff) Same book, same page, line 12 ■ “Belt width (Wt)
J is corrected to [slab width (Ws) j]. (6) Correct the information in Figure 3 as shown in Figure 3 and the 4th WA meeting appendix. & List of attached documents (1) Scope of claims after amendment 1 copy (8) Amended drawings [ii (Figures 3 and 4)] Claims (1) From continuous casting to finish rolling A method for manufacturing a thin steel sheet in which the steps up to
Thickness 1 using a continuous casting machine with F5 swi/m''
A method for manufacturing a thin steel sheet, characterized in that a slab of 180 mm or less is cast, and the plated slab is successively rolled and finished rolled to obtain a rolled steel sheet with a spacing of 26 m or less. This is a series of manufacturing equipment that continuously converts thin cast slabs into hot rolled steel sheets, including Toko Steel supply equipment, twin belt casting - 1 secondary cooling, 1 bud, and vinyl casting. It consists of a series of equipment for rolling strips, slab cutting machines, slab cutting and correction machines, slab temperature direct equalization equipment, slab width reduction equipment, hot finish rolling equipment, and rolled steel plate cutting equipment! Equipment for manufacturing thin steel 4[O].

Claims (1)

[Scope of Claims] [l] A method for manufacturing a thin steel plate in which continuous casting and finish rolling are performed continuously, the solidification rate coefficient being 15 to 2S-/
, ”T A □ Sewing, ,, □. A slab of 14.8゜■ or less is cast, and the cast slab is continuously subjected to FE]ii and finish rolling to form a 26- or less O heat rolled plate. (2) A series of manufacturing equipment for converting molten steel into thin slabs, which are then continuously hot-rolled and rolled into plates, including the Kikko-no-Rin equipment, the Twinpe J& /) Rin casting machine, secondary cooling bud, bin narrow y bud, slab cutting machine, slab cutting/correction machine, slab temperature equalization device, slab width retainer device, hot fighting finishing rolling machine group, and rolling/plate cutting Clause 1 i5m where a series of devices are arranged to create a seven-stage mold
Apparatus for use in this method.