JPH01319627A - Sheet-like decarburization preventive material and method for steel products and coating device for sheet-like decarburization preventive material - Google Patents

Abstract

PURPOSE:To heat the surface of steel products such as billets without oxidizing and decarburizing said surfaces by previously press welding the decarburization preventive sheet consisting of an oxide system having a specific compsn. onto the surfaces of the steel products at the time of heating the steel products in a heating furnace. CONSTITUTION:The steel products 1 such as slabs, blooms and billets to be heated are mounted on the decarburization preventive sheet 2 having the compsn. consisting of 10-25wt.% powdery Al2O3, 4-12wt.% Na2O and K2O in total, 10-15wt.% moisture and the balance SiO2 powder and having 0.1-1mm thickness. A supporting plate 3 on the rear surface of the steel products 1 is risen to bring the decarburization preventive sheet 2 into tight contact with the rear surface of the steel products 1. Rolls 4, 4 are then risen at both sides of the steel products 1 to press weld the sheet 2 to the side face of the steel products 1 and in succession, the rolls 4 are traversed to press weld the sheet 2 atop the steel products 1 and to press weld the sheet 2 over the entire surface in the longitudinal direction of the steel products 1; thereafter, the steel products are heated to <=1,170 deg.C in a heating furnace. The sheet 2 is easily stripped from the steel products 1 after the heating treatment.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a decarburization prevention material that is coated on the surface of steel materials when the steel materials are put into a heating furnace, a method for preventing decarburization of steel materials using the same prevention material, and a method for preventing decarburization of steel materials using the same prevention material. This invention relates to a coating device for anti-charcoal material.

(Prior Art and Problems to be Solved by the Invention) Steel products are generally manufactured by heating steel materials such as slabs, blooms, and fillets in a heating furnace and then rolling them. This may be caused by a decrease in grain strength due to decarburization. Therefore, JP-A-54-10
7410, SiC100 is used as a decarburization prevention material.
A mixed powder is used in an amount of 950 to 2000 parts by weight based on parts by weight, and it is common to make an aqueous solution and use a spray nozzle to apply it to steel materials. A common method for preventing decarburization is to apply the above-mentioned mixed powder to the surface of a steel material, apply an antioxidant thereon, and heat the mixture.

The problems with such a decarburization prevention layer are ■ Even though the purpose of preventing decarburization is achieved because the mixed powder contains C-based 51G, when the steel material is heated, carburization occurs on the surface of the steel material. The C content on the surface of the steel material increases by 0.05 to 0.10% by weight relative to the inside of the steel material. If rolling is carried out in such a state, the surface of the steel 42 becomes brittle due to carburization, so surface flaws frequently occur and product defects occur.

(2) When applied in the form of a mixed powder, it flows through the spray nozzle as an aqueous solution, which tends to cause equipment drubbing such as spray clogging, as well as uneven and incomplete coating of the formed film. Furthermore, as direct rolling progresses, from the perspective of energy conservation, flowing mixed powder with an aqueous solution causes energy loss due to evaporation of water, which is a problem.

In addition to the problems with the dominant decarburization prevention material, the problems with the method of preventing decarburization are: In addition to the problems with the dominant decarburization prevention material, It takes more time and doubles the coating equipment, which doubles the equipment cost. Such a method is disadvantageous in terms of direct rolling and low cost equipment.

■ After application by spraying, etc., a drying process is necessary to prevent the decarburization prevention material from peeling off during transportation before heating, or due to the nature of the decarburization prevention material, rapid heating may generate bubbles and deteriorate the film. The drying process takes a long time and reduces productivity.

■ Steel 4. Coating on fl 1) The coating has a decarburization prevention function by adhesion during heating, and after extraction in a heating furnace, the peelability of the decarburization prevention material is important. If the steel material is coated with anti-decarburization strips before being put into the rolling mill, it must be removed, which requires additional labor or equipment. For this reason, it is necessary to take into account the composition of the decarburization prevention material and to regulate conditions for good releasability, that is, coating thickness and heating temperature conditions, or the prior art does not disclose the above.

(Means for Solving the Problems) The present invention advantageously solves the above-mentioned problems, and the gist thereof is as follows.

1. Al2O3 10~25 heavy view n1 A total of 4~12% by weight of Na2O and or K2O, 10~25% by weight of water, the balance being SiO2 and unavoidable impurities, and a thickness of 0.1~1.0 mm. Sheet-shaped decarburization prevention material for steel materials.

2. A method for preventing decarburization of a steel material, which comprises coating the surface of the steel material with the decarburization preventing material described in item 1 above, and then heating the material at a heating temperature of 1170° C. or lower.

3. A decarburization prevention material coating device for steel material, which coats the surface of the steel material with the sheet-like decarburization prevention material described in item 1 above,
a support press plate that supports a decarburization prevention material in contact with the lower surface of the steel material; a pair of wrapping rolls that can rise and fall on the side of the steel material and move laterally; and a pair of wrapping rolls that press the wrapping rolls against the steel material surface. (Pull-pressing mechanism and the roll for rolling.)
7. A coating device for a sheet-like decarburization prevention material for steel, characterized by having a roll movement mechanism that allows it to be raised and lowered and moved laterally.

4. The above-mentioned device characterized by having a plurality of suction pads for conveying the sheet-like decarburization prevention material described in item 1 above, and a conveyance mechanism for conveying the diagnostic adsorption pad to the support pressure plate described in item 3 above. This is a coating device for sheet-like decarburization prevention material for steels T and L as described in item 3.

(Function) The decarburization prevention material according to the present invention will be explained with reference to FIGS. 1 and 2. The decarburization prevention material 2 according to the present invention is not a conventional aqueous solution containing gold powder or a mixture thereof, but is a comb-like solid substance, and is made of a thin film with a thickness of 1 to 1.0 mm and reinforcement with Saran resin or the like. It is characterized by being composed of a thin film 13.

Regarding 8F1203 in the decarburization prevention material of the present invention, if it is less than 10% by weight in the decarburization prevention 4Δ, the fire resistance will be low, so when heating, the effect of preventing decarburization cannot be obtained, so the lower limit is set to 10%. 5%. On the other hand, An 20. or 30
If it exceeds % by weight, the airtightness of the film will decrease.
Since the effect of preventing decarburization cannot be obtained, the upper limit is set at 30% by weight.

Na2O and K2O are important components indispensable for melting and vitrifying the film during heating.

If the sum of Na2Q and 2(l) is less than 5% by weight, the vitrification of the film during heating will be insufficient and the effect of preventing decarburization will not be obtained, so the lower limit is set at 5% by weight.On the other hand, the sum of Na2O and K2O If it exceeds 15% by weight, the glassing rate of the coating increases when heated, and at high temperatures the coating becomes fluid and the decarburization prevention effect decreases. .

If the water content is less than 10% by weight, it becomes anhydrous and loses its flexibility, so the lower limit is set at 10% by weight.On the other hand, if it exceeds 30% by weight, it becomes a rubbery solid or liquefies, so the upper limit is set at 30% by weight. Weight%.

The thickness of the comb-shaped solid of the above component system is less than 0.1 mm1
If 7 colanders are used near I, the decarburization effect will occur, so the lower limit is set at 3.1 m.
m, and if it exceeds 1.0 mm, the adhesion during heating will be poor and it will be easy to peel off in the heating furnace, so the upper limit is set to 10 mm. In addition, a thin film such as Saran resin has a weak strength when used as a decarburization prevention sheet and may cause trouble such as breakage during wrapping work, so it serves as a reinforcing material.

The material for this thin film is limited to Saran-O Δ1 fat, as long as it has appropriate flexibility and strength necessary for wrapping around the i-steel material.

In the method for preventing decarburization of steel according to the present invention, the sheet-shaped decarburization prevention material according to the present invention is wrapped around the surface of the steel and heated in a heating furnace. When heating, if the heating temperature exceeds 1170℃, the above decarburization prevention material (2FeO・5iO2) FAY
-The melting reaction of ALITE increases its adhesion to steel materials. For this reason, the decarburization prevention material cannot be peeled off after heating, and labor or equipment is required to peel it off, so the upper limit is set at 1170°C.

On the other hand, when applying the sheet-shaped decarburization prevention material according to the present invention to the surface of a steel material, the first decarburization prevention material is placed on an existing conveyance table or conveyance roll, and the steel material is wound without rolling. is easy. However, with this method, the adhesion of the above-mentioned sheet decarburization prevention material to the surface of the steel material is poor;
Air gaps are likely to occur. If it is placed in a heating furnace in such a state, the decarburization prevention material will be damaged in the areas where there are gaps and the decarburization effect will be lost, causing a problem.

In order to solve the above-mentioned problems, a device for wrapping a sheet-like decarburization prevention material according to the present invention is required.

(Example) In Table 1, the decarburization prevention material according to the present invention and the decarburization prevention method using the same prevention system will be explained together with comparative examples.

The results are shown when a film layer for preventing decarburization was formed on the surface of a fillet with a length of 18 m containing 7 to 08% CO, heated, and then rolled to produce a wire rod.

In methods No. 1 to 7 according to the present invention, when the cross section of the wire rod as a product was inspected, no decarburization occurred at all. Furthermore, when rolling after heating, the film layer for preventing decarburization was completely peeled off during roll conveyance, and there was no effect on the product after rolling.

In the composition of the film layer, cases where Afi 203 is outside the lower limit and upper limit of the specified range of the present invention are shown as No. or not achieved.

No. 10 is the composition of the b layer, Na2O and K2O
If the total amount is less than 4% by weight, the state becomes brittle and easily permeable during heating, and the effect of preventing decarburization cannot be achieved.

No. 11 is the composition of the film layer, Na2O and K2O
If the combined amount exceeds 12% by weight, the film layer will run off during heating and will not function as a decarburization prevention layer.

No. 12 is a case where the water content of the coating mixture is less than 10% by weight. In this case, the film layer does not become rubber-like and has poor adhesion to the steel material, resulting in insufficient decarburization effect.

No. 13 is a case where the water content of the coating mixture exceeds 25% by weight, and the film layer is not in the form of a comb but in the form of an aqueous solution, making it impossible to maintain a uniform film thickness on the steel material. Similarly, for N014, the thickness of the coating layer to prevent decarburization is 0.1 mm.
If it is less than that, decarburization occurs and becomes a problem.

No. 15 is a case where the thickness of the coating layer for preventing decarburization exceeds 10 mm, the adhesion during heating is poor, and it is easy to peel off in the furnace, causing a partial decarburization phenomenon.

No. i6 is when the heating temperature exceeds 1170°C, and the coating layer is (2FeO・5iO2) FA'1ALIT
Due to the melting reaction of E, the adhesion to the steel material increased significantly, and adhesion of the coating layer to the rolled product was observed.

The present invention will be described in detail below based on the embodiment shown in FIG. As an example of a steel material, when considering a billet 1-, there is a sheet-like decarburization prevention material 2 of the present invention on the lower surface side of the billet 1, and a supporting press plate 3 below it. The billet 1 is in close contact with the sheet-shaped decarburization prevention material 2 while being supported by the supporting presser plate 3 due to its own weight. It is preferable that the surface of the support press plate 30 be made of an oily material so that it does not come into close contact with the sheet-like decarburization prevention material 2. On both sides of the supporting press plate 3, there are a pair of winding rolls 4 on which a movable sheet-like decarburization prevention material is wrapped around the side and top surfaces of the billet 1. In the support stand 5 supporting the wrapping roll 4, there is a pressing mechanism 6 having a cylinder for pressing the wrapping roll 4 against the side and top surfaces of the fillet l-1. Furthermore, the support stand 5
It has a lifting motor 7 for raising and lowering the winding roll 4 and a traversing motor 8 for moving the winding roll
There is a roll movement mechanism that has eight ribs on the side and top surfaces of billet 1.

In FIG. 4, the portion surrounded by chain lines indicates the device in FIG. The apparatus of the present invention further includes a plurality of suction pads 9 for adsorbing the sheet-shaped decarburization prevention material 2, and the sheet-shaped decarburization prevention material 2 adsorbed by the suction pads 9 on a winding roll 4 ( Or a cylinder 10 for raising and lowering and a motor 1 for traversing to move to a supporting presser plate 3)]
It has a conveyance mechanism having.

The sheet-like decarburization prevention material 2 is cut into a required length from a sheet-form decarburization prevention material roll 12 wound into a coil shape and supplied. Such a sheet-like decarburization prevention material roll 12 can be easily manufactured using a commercially available steel helt trier or the like.

FIG. 5 shows a flow of wrapping around the surface of a billet 1 using the apparatus according to the present invention. Figure 5(a) shows the adsorption para l-
The sheet-like decarburization prevention material 2 adsorbed in step 9 is transferred to billet 1.
This shows how it is set on the bottom surface of the . In (b), the supporting presser plate 3 is raised to bring the decarburization prevention material 2 into close contact with the lower surface of the billet 1. In the same step (c), the decarburization prevention material 2 is pressed onto the side surface of the billet while the winding roll 4 is ascending. In (d) and (e), the decarburization prevention material 2 is pressed onto the top surface of the billet while the winding roll 4 is rotated. In (f), after the decarburization prevention material 2 is wrapped around the surface of the billet 1, the billet 1 returns to its initial position.

(Effect of the invention) The present invention exhibits the following excellent effects.

■ Steel quality problems such as carburization can be advantageously avoided, and there is no need to double coat the antioxidant.
It is possible to shorten the time for applying the decarburization prevention material and reduce equipment costs.

■ The decarburization prevention material is easy to peel off after heating, and no labor or equipment is required for this peeling.

■ The method of wrapping the decarburization preventive material in the shape of a sheet around the steel material makes it possible to form a uniform film with no defects compared to conventional techniques that apply an aqueous solution or a liquid substance, and prevents clogging of spray nozzles. No maintenance required. Furthermore, by omitting the drying process, there is no reduction in productivity even if the process is carried out online.

(2) From the point of view of energy saving, the decarburization prevention material in the form of Sea 1 is advantageous because it does not lower the temperature of the steel material during hot-piece charging.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the structure of the sheet-shaped decarburization prevention material of the present invention, FIG. 2 is an explanatory diagram showing the state of the sheet-shaped decarburization prevention material 2 of the present invention after being wrapped around a steel material, and FIG. FIG. 4 is an explanatory diagram of an embodiment of the winding and unloading device of the present invention, and FIG.
Figure 5 (a), (b), (c), (d)
, (e) and (f) are diagrams showing the flow of an embodiment in which a sheet-like decarburization prevention material is wrapped around the surface of the prepared material using the apparatus of the present invention. 1... Fillet L- (steel material) 2... Sheet-like decarburization prevention material 3... Pressing plate for support 4... Roll for winding 5
...Support stand 6...Press mechanism 7...Elevating motor 8...Motor for traversing 9...Suction pad 10...Cylinder for elevating and lowering 11...Motor for traversing 12... Sheet-like decarburization prevention material roll 13...reinforcing thin film

Claims (1)

[Claims] 1 Al_2O_3 10-25% by weight, a total of 4-12% by weight of Na_2O and/or K_2O, moisture 10-2
5% by weight, the remainder consisting of SiO_2 and unavoidable impurities,
A sheet-like decarburization prevention material for steel, characterized in that the thickness is 0.1 to 1.0 mm. 2. A method for preventing decarburization of a steel material, which comprises coating the surface of the steel material with the decarburization preventing material according to claim 1, and then heating the material at a heating temperature of 1170° C. or lower. 3. A decarburization prevention material coating device for steel material, which coats the surface of the steel material with the sheet-like decarburization prevention material according to claim 1, and a supporting press plate that supports the sheet-like decarburization prevention material in contact with the lower surface side of the steel material. a pair of wrapping rolls that can rise and fall on the side of the steel material and move in the lateral direction; a pressing mechanism that presses the wrapping rolls against the surface of the steel material; and a pair of wrapping rolls that can rise and fall and move in the lateral direction. 1. An apparatus for coating steel with a sheet-like decarburization prevention material, characterized in that it has a roll moving mechanism for coating steel with a sheet-like decarburization prevention material. 4. Claim 3, characterized by comprising a plurality of suction pads for conveying the sheet-like decarburization prevention material according to claim 1, and a conveyance mechanism for conveying the suction pads to the supporting presser plate according to claim 3. An apparatus for coating the steel described above with a sheet-like decarburization prevention material.