JPS60162507A - Manufacture of hot rolled steel sheet - Google Patents

Abstract

PURPOSE:To manufacture a hot rolled steel sheet having an excellent mill-scale film at low cost by removing scales produced on the surface of a steel slab to rough roll the slab by sticking glass paper to its surface and finish rolling the coated slab thereafter by removing the glass sticking matter. CONSTITUTION:A steel slab 7 manufactured by a continuous casting method or blooming method is heated at need by a heating furnace 1. After removing scales on the surface of slab 7 by descaling devices 9a, 9b, glass paper is stuck to its surface by glass-paper sticking devices 10a, 10b to form a molten glass film. This slab 7 is then rolled into a sheet shape by roughing mills R1-R6. Next, the surface of this rough rolled steel sheet is descaled by descaling device 90a, 90b to remove the glass film. This steel sheet is successively finish-rolled by finishing mills F1-F6, to form a mill scale excellent in adhesive, anticorrosive, and pickling properties, and is wound up into a coil by a winder 15 after cooling the sheet by cooling devices 14a, 14b.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing hot rolled steel sheets used for general structures, automobiles, etc.

(Prior art) In the hot rolling process, a glass-like substance is formed on the front and back surfaces of the rolled material. This reduces the amount of descaling water used, eliminates floating scale, and reduces scale on the surface of the steel plate after winding (hereinafter referred to as black scale to distinguish it from the secondary scale described above). A method for achieving excellent adhesion, corrosion resistance, and pickling properties is a well-known technique disclosed in JP-A-57-115901.

7. By the way, in this method, after heating and removing the primary scale, a glassy substance with a melting point of 850 to 1200°C is applied to the surface of the material to be rolled, and then the high-pressure water spray in the descaling tank is substantially omitted and the heating is continued. However, since glass powder is used as the glassy substance, there remains a technical problem in ensuring uniform coating thickness, and there is also the possibility that scale, water, or steam may be present in the glass powder in the coating equipment. In addition, there are problems such as the contamination of glass lumps that fall on contact with the steel material, and environmental equipment costs related to handling glass powder.In addition, a glass coating is attached to the surface of the hot-rolled steel sheet after winding. Therefore, if the black scale is processed as it is, uneven peeling may occur, which may be inconvenient for the purpose of use.

(Objective of the Invention) The present invention provides an economical method for producing hot rolled steel sheets having an excellent black scale coating by providing a new coating method that solves the above-mentioned problems caused by glass powder coating. The other purpose is to suppress the generation of secondary scale, and to ensure the hot rolling temperature and save power of the deskebonzo by omitting the high-pressure water descaling link as much as possible. The aim is to improve hot rolling lubricity using molten glass and reduce rolling power costs.

(Structure and operation of the invention) The present invention provides a hot-rolled steel plate manufacturing method in which a slab or steel slab manufactured by a continuous casting method or a blooming method is hot-rolled directly or by reheating and performing rough and finish rolling steps. In,
Before rough rolling, the slab or steel slab is descaled, glass paper is applied to the upper and lower surfaces of the slab or steel slab, and after rough rolling, the slab or steel slab is descaled before finish rolling. The gist of this invention is a method for producing a hot rolled steel sheet, which is characterized by performing finish rolling after removing deposits.

The present invention will be explained in detail below.

FIG. 1 is a schematic explanatory diagram of a manufacturing method according to an embodiment of the present invention.

Molten steel produced in a converter (not shown) is transferred from ladle 1! -2, it is injected into a mold 3, solidified, and formed into a slab 4, which is continuously pulled downward while being guided, drawn, bent, etc. by a group of rolls 5.

Next, it is cut by a gas cutter 6 into unit slabs, such as slabs 7, of a predetermined length. Reference numeral 8 denotes a heating device, such as an end rust induction heating device, provided during the conveyance. 1
1. Is there a problem with temperature drop, surface scratches, etc. in the heating furnace? f
7 is turned into a cold piece and treated for defects, then charged into the heating furnace 11 and reheated to the rolling temperature.If the temperature drop is not so large, it is charged into the heating furnace 11 for a short time and the hot rolled 2 Sent to Inn. 12.13 schematically shows the yarn path.

Normally, in direct rolling, the continuously cast slurry f7 is descaled on the front and back surfaces by the descaling devices 9a p 9b, and then immediately transferred to the glass paper adhering devices 10m, 10.
Glass paper is pasted on the front and back surfaces via b, and then rough rolled by rough rolling mills R1 to R6.

Thereafter, the glass coating on the surface is removed by descaling devices 90a and 90b. Next, the material is rolled into a material having a predetermined thickness and width by finishing mills F1 to F6, and the material is rolled into a cooling device 14.
After receiving the prescribed cooling effect from a and 14b, the winder 1
5 into a coil.

FIG. 2 is a schematic view of one embodiment of the glass paper deposition device according to the present invention, in which a glass paper 16 wound into a coil is used to form 17a, 1
7b is a pinch roller that serves both as a drawer and a guide for the glass paper. 18 is a cutting device for 16 m of glass paper, which is fixed to the heat insulating plate 19.

20a and 20b are press rollers for firmly adhering the glass paper 16a to the material to be rolled 22, and are supported by cylinders 21a and 21b so as to be able to rise and fall, respectively.
m and 21b are fixed to a support beam (not shown) and are located directly above the rolled material 22.

When it is detected visually or by a photoelectric detector (not shown) that the rolled material 22 has reached a predetermined position by the conveyance roller 23, the pinch rollers 17a, 17
b is activated to let the glass paper 16a hang down onto the conveying system. The temperature of the rolled material 22 is 850~ even in direct rolling.
When the temperature is as high as 1200° C. and the temperature of the rolled material 22 is higher than the melting point of the glass paper 1-6a, 650 to 1100° C.,
The glass paper 16a is fused to the surface of the material to be rolled 22.

Therefore, if 16 m of glass paper is fed out one after another, the surface of the material to be rolled 22 can be completely covered as it moves.

The presser loaf 20 m + 20 b is used in this case to supplement the uniform application, but in some cases the presser roller 20. a and 20b may be unnecessary.

Furthermore, in order to apply glass paper to the sides and front and rear surfaces of the material to be rolled after descaling, a method such as making the glass paper to be applied to the upper and lower surfaces larger than the material to be rolled and pressing it with an edger roll may also be used. Good results may be obtained if this is done.

Next, after confirming that the surface adhesion of the rolled material 22 has been completed by an optical detection device (not shown) or a measurement signal from a measuring device for measuring the length of the rolled material 22 and glass paper feeding length, or by visual inspection, the The cutting device 118 is operated to cut the glass paper 16m.

According to this device, glass paper can be easily and reliably adhered to the material to be rolled 22.

FIG. 3 is a schematic diagram of an example coating for applying glass paper 161L to the back surface of the material to be rolled 22, in which the pinch roller 17
a, 17b, the coiled glass paper 16 to the glass paper 1
6m is pulled out, the glass paper 16m is guided diagonally while sliding on the oblique guide row 224, and the glass paper 16a is pressed against the back surface of the rolled material 22 that has been conveyed by the pressing row 225.

The timing of feeding out 16 m of glass paper and the adhesion procedure are as follows.
This is almost the same as the case shown in the figure.

Reference numeral 26 denotes a cutting device for the glass paper 16a, which is activated to cut the glass paper 16m when the adhesion of the rolled material 22 is completed or predicted to be completed. As the device, an appropriate device such as a well-known guillotine shear or rotary blade shear can be used.

The prediction of the end can be easily performed, for example, by setting the photoelectric detection device 27 at an appropriate position and calculating the movement of the photoelectric detection device 27 by a control device (not shown) based on the signal. By controlling the cutting device 26 in a feedforward manner based on the calculation result, it is possible to adhere the glass paper 16 in an appropriate amount. 28 is a heat insulating plate for insulating the glass paper 16m from melting due to the high heat of the rolled material 22 before it is attached, so that seizure will not occur;
Perform water cooling if necessary. This heat shield plate 28 is the material to be rolled 22
It also has the function of preventing secondary scale that comes off from the glass paper 16a from adhering to the glass paper 16a.

In FIG. 4, a glass paper 29 having a length and width sufficient to cover the surface of the material to be rolled 220 is placed on a table 30 in advance.
This is a schematic diagram of an apparatus in which a predetermined number of sheets are placed on the surface of a material to be rolled 22 via a vacuum suction conveyance tool 31 and then deposited one by one on the surface of the material to be rolled. The lifting shaft 32 is fixed to a crane device 34 mounted on a girder 33 so as to be movable. This method has the advantage that it is economical and labor intensive when a large amount of rolled material such as slabs is used compared to preset dimensions, and maintenance operations are easy.

As mentioned above, in the present invention, the slab 7 cut by the gas cutting machine 6 is immediately descaled and glass paper is applied thereto, or the glass paper is applied after descaling on the entry side of the roughing mill R1. is applied and rough rolling is performed. Therefore, it is desirable to carry out the process at the early stage of hot rolling, when the length of the material to be rolled is relatively short and the adhesion is easy, or when the material to be rolled is at a high temperature and the effect of suppressing secondary scale generation is enhanced. As the descaling means, in addition to the aforementioned descaling means using high-pressure water, any polishing IJ means such as a rotating wire brush or a roll containing abrasive grains or steel wool can be employed.

Next, as the glass paper according to the present invention, ultra-fine glass phino 9- is filtered into a paper shape, and commercially available Grapest (trade name, manufacturer: Oriental Asbestos ((trans)), etc. is suitably used.Glass paper As a material, it is also possible to use a material made by adding paper, thread, etc. to glass powder and forming it into a paper shape.The thickness is 0.15 to 5.
．． 0m is used 2>i, if the Oma 9 is thin, the film formed by melting will be too thin and the anti-oxidation ability will be poor.
If it is too thick, it will take too long to melt during deposition, reducing productivity! Quantitative power decreases and becomes useless as the effect saturates against the purpose; increases and loses economic efficiency. According to the experience of the present inventors, a value of about 2.0 to 3.011111 is suitable.

Next is the melting point of glass paper, which according to the inventors' experience is 6.
A temperature of 50 to 1100°C is preferred. The maximum temperature of the rolling roll in the hot rolling process is 5E500 to 600°C, so if the melting point is 650°C or higher, there is little risk that glass will adhere to the surface of the rolling roll and interfere with rolling.

On the other hand, if the melting point of glass paper is too high and exceeds the rough rolling temperature of 1000℃, it will solidify during the rolling process, cracks will appear in the coating, local oxidation will occur, and floating scale will occur. In addition to causing phenomena such as pressure washing on the surface of the pressurized abrasive, there are many other problems such as poor lubricity of the roll and accelerated wear. Therefore, the upper limit of the melting point of glass paper is 1100℃
Therefore, it is desirable that the material be in a softened state even at 900°C.

The main component of the glass paper is K5i as shown in the example.
n2# Na2O, CIO or S l 021 At
203 or CaOf as the main component is used,
5I0250~80%, Ca010~30%,
200-30g for Na2o+6. At2030 to 20 cm, etc., and MgO to these.

A mixture of one or more of two or more of pe O+ LLO+ B O+ BeO+ TIO and Z rO2252232 is used. Then, glass fibers having a diameter of several microns or glass powder having a particle size of 100 mesh or less are added to these glass components with an inorganic binder and fibrous material to form a paper-like material as described above.

(Example) 1 Ultra-low carbon At-killed continuous νJ casting slab (thickness 250wn
) was descaled with high-pressure water on the inlet side of the rough rolling mill, immediately coated with glass paper with a thickness of 3 and having the ingredients shown in Table 1 in the manner described in Figures 2 and 3 above, and then After rolling, high-pressure water descaling was performed in front of the finishing mill to remove the glass coating, and finishing rolling was performed to obtain 1.8
A hot-rolled steel plate with a thickness of mn was manufactured.

The comparative material was conventionally hot-rolled (roughly rolled) without any coating.

A method was adopted in which hot rolling was performed while performing high-pressure water descaling on the entry side of finishing rolling.

The load during rough hot rolling was measured on each stand, and the rough No. 3 stand (F,) (reduction amount 23 mm) and rough No. 5 stand (
At a rolling reduction of 16 tn), the rolling load of the lath-adhered rolled material was reduced by 14% and 23%, respectively, compared to the comparative material.

On the other hand, the hot-rolling finishing exit temperature of the rolled material coated with glass paper was increased by about 50°C to 80°C compared to the conventional material. In addition, the surface condition of the glass-covered wave-rolled material was comparable to that of ordinary material. (Example) 2 A continuous cast slab of general structural rolled steel material 8841 was made into a cold slab, and after cleaning the defects, it was reheated at 1250°C. After descaling the surface with high-pressure water, 2111I thick glass paper was applied using the method shown in Figures 3 and 4, and after rough rolling, it was descaled with high-pressure water twice on the front of a finishing mill, and then finished rolling. Action 3
．． A hot-rolled steel plate with a thickness of 2cm was manufactured.

The comparative material was subjected to conventional hot rolling, that is, rough rolling, finishing rolling, and descaling with high pressure water.

In the case of the present invention, there is almost no scale generation during rough rolling, the rolling load is reduced by more than 10% compared to normal materials, and the finishing temperature is 40%.
The surface condition of the material heated to ~60°C and then pickled was as good as that of the comparative material. (Effects of the Invention) According to the present invention, the glass coating can be made uniform, so rolling is easy. The lubricating effect is excellent, and the generation of secondary scale can be significantly suppressed. Furthermore, descaling
It has the advantage of saving 10 to 30 cubic meters of rolling power and requiring only a small environmental cost.In addition, compared to conventional technology, equipment costs are lower and hot-rolled steel sheets with excellent surface quality can be produced economically. can.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of a manufacturing method according to Embodiment K of the present invention, and FIGS. 2 to 4 are schematic explanatory diagrams of different embodiments of the glass paper deposition apparatus according to the present invention. 1... Ladle, 2... Tundish, 3... Mold, 4... Slab, 5... Roll group, 6... Gas cutting machine, 7... Slab, 8...・Heating device, 9a, 9b
, 90a, 90b... descaling device, 10a
, 10b...Glass paper adhering device, 14a-14b
...Cooling device, 15... Winding machine, 16... Glass paper, 17a, 17b... Pinch roller, 18... Cutting device, 19... Heat shield plate, 20a. 20b... Press roller, 21a, 21b... Cylinder, 22... Rolled material, 23... Conveyance roller, 2
4... Oblique guide roller, 25... Pressing roller, 2
6... Cutting device, 27... Photoelectric detection device, 28...
- Heat shield plate, 29...Glass paper, 30...Glass paper stand, 31...Vacuum suction transport tool, 32...Elevating cylinder, 33...Girder-134...Crane device. Figure 1 1 □□□-114^ 2nd 6 Figure 3) Figure 4 7

Claims (1)

[Claims] In a hot-rolled steel sheet manufacturing method in which a slab or steel slab manufactured by a continuous casting method or a blooming method is hot-rolled directly or reheated and subjected to rough and finish rolling steps, the casting process is performed before rough rolling. After descaling the slab or steel slab, then applying glass paper to the upper and lower surfaces of the slab or steel slab, performing rough rolling, and then descaling and removing the glass adhered material before finish rolling. , a method for producing a hot-rolled steel sheet, which is characterized by performing finish rolling;