JPS637325A - Hearth roller for thick plate - Google Patents

Abstract

PURPOSE:To obviate the generation of a pickup on the rear surface of a heated thick plate even after long-term use by intermittently disposing ceramic sleeves to the outside of a hollow roller core body and providing clearances and cushion materials between the roller core body and the ceramic sleeves. CONSTITUTION:The ceramic sleeves 2 are independently and loosely fitted at spaced intervals from each other via the clearances 3 and cushion materials 4 to the outside of the hollow roller core body 1 consisting of a heat-resisting steel, etc. Stoppers 5 to restrain the movement of the ceramic sleeves 2 and the cushion materials 4 in the axial direction of the roll are provided thereto. The clearances 3 are provided with the size required to absorb the thermal expansion of the roller core body 1 and the ceramic sleeves 2. The revolutions of the roller core body 1 of a hearth roller constituted in such a manner are transmitted to the sleeves 2 through the cushion materials 4 by the weight of the ceramic sleeves 2. The thick plate is smoothly moved forward and backward in follow up to the roller core body 1 by the addition of the weight of the thick plate to be conveyed during the passing thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a hearth roller for thick plates used when heat treating thick plates in a roller hearth furnace.

[Conventional technology]

Thick plates may be hardened or hardened to increase their strength as needed.
Tempering treatment and skewering treatment for the purpose of making grains finer are performed. In such heat treatment, the treatment temperature is 1000°C.
Therefore, when using a roller hearth furnace, use ACI standard HK2O (25%) for the hearth roll.
Heat-resistant steel such as Cr-20%Nt) is used, and the shape is hollow to reduce weight.

[Problem that the invention seeks to solve]

However, in a hearth roll like this, the atmosphere is ot? As the Q degree increases, oxide scale adheres to the surface, which causes surface flaws called pickups to occur on the back side of the heated thick plate as it passes over the rolls.

Moreover, it has been found from past experience that hollow rolls made of heat-resistant tIBI cause localized blistering during use, and that this blistering also causes pink-up.

Pink amplifiers can be prevented if the rolls are replaced frequently, but heat-resistant lake rolls are expensive, and replacing the '6H2 is impossible due to cost. At Kuwagyo, we are dealing with this problem by repairing most of our pickups. However, this addition 12 also requires a small amount of time and effort, resulting in increased manufacturing costs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hearth roll for thick plates that is free from the risk of generating pick amps even after long-term use.

[Means for Solving the Problems] By the way, as a means for increasing the heat resistance of hearth rolls, there is water cooling of the rolls. However, this water cooling cannot be easily adopted because it reduces the thermoeconomic efficiency of the furnace by as much as 20% to 30% and causes large heat losses.

Therefore, countermeasures from the viewpoint of materials are being considered.

One of these is the introduction of ceramics, and examples of the use of ceramics have already been seen in hearth rolls (Japanese Patent Application Laid-Open No. 104415/1983, etc.). However, although ceramics have excellent heat resistance, they have poor impact resistance, and their use has been limited to hearth rolls for thin plates such as galvanized steel plates.

In other words, in the case of thin plates, not only are they lightweight, but also because they are used as strips, tensile force is constantly applied in the longitudinal direction, and even when the plates pass through a roller hearth furnace, there is virtually no burden on the hearth rolls. Since there is no need to apply heat, ceramics can be used. However, thick plates are themselves heavy, and because they are used for cutting, each hearth roll carries a static load of several hundred kg.
￥If there is a downward curvature or a burr on the end surface, the impact load when passing one plate is several times or even tens of times that amount, and common sense would not consider the use of ceramics in hearth rolls for thick plates. It was assumed that it would not be allowed.

The present invention provides a ceramic sleeve and a cushioning material roller in which a ceramic sleeve is intermittently arranged outside a hollow roller core body in the axial direction of the roller, a clearance and a cushioning material are provided between the roller core body and the ceramic sleeve. By providing a stopper to restrict axial movement, the three-strip feature allows the introduction of ceramics into hearth rolls for thick plates, thereby suppressing the occurrence of pink-up without frequent roll replacement.

[Effect]

What is important in the design of hearth rolls is the prevention of creep deformation. In particular, rolls for thick plates receive a large static load from the material, unlike rolls for thin plates, so prevention of creep deformation is important. However, when the ceramic sleeve is fitted around the roll core, the load due to the ceramic sleeve is newly added to the roll core, which becomes even more disadvantageous in terms of creep deformation. In addition, ceramic sleeves inevitably become thicker due to their manufacturing technology and impact load resistance, and as a result, it is difficult to suppress their own weight. The structure of a ceramic sleeve roll intended for thin plates cannot be put to practical use.

Figure 3 shows the 10'l (r -1% creep curve) of HK40 material, and Figure 4 shows the dimensional range of thick plates that can be processed determined from the same curve. .6m
, outer diameter 300mm, inner diameter 260mm, wall thickness 20m, ceramic sleeve dimensions 330m5. Outer diameter 370m
m, meat jzo 201-1 material is SI3N4 (90% or more)
The case is shown below.

What is plotted with O in Figure 4 is the dimension of the j1 plate actually provided, but in the case of the above roll core, if there is no ceramic sleeve, the dimensions of the thick plate actually provided are all within the allowable range. (However, pickup will occur).

However, in a structure in which a sleeve is arranged in the entire roll axis direction as shown in Japanese Patent Application Laid-Open No. 51-104415,
17 of the - section deviates from the allowable range of dimensions, causing deflection due to creep deformation during the period of use, and the roller cannot be put to practical use, not to mention the occurrence of pink amplifier.

However, the hearth roll for thick plates of the present invention has the following characteristics.
This synergistic effect prevents the occurrence of pickup and provides sufficient practicality.

■ Ceramic sleeves are disposed intermittently in the roll axis direction, reducing the creep load on the roll core and allowing J-boards of any size to be conveyed without creep deformation. The permissible dimensional range of the roll of the present invention, shown by the broken line in 4th and 1, is when three ceramic sleeves of 400 μ in length are arranged per roll.

■ Since the creep load on the roll core can be reduced, sufficient sleeve thickness can be ensured, and since a cushioning material is interposed between the roll core and the ceramic sleeve, the ceramic sleeve can be protected from the impact load caused by the thick plate. Protect and prevent its cracking.

■ The stopper prevents the ceramic sleeve and cushioning material from shifting, and stabilizes the crack prevention effect of the ceramic sleeve.

Note that the clearance provided between the roll core and the ceramic sleeve is for preventing the ceramic sleeve from cracking due to thermal expansion of the roll core.

〔Example〕

1 UA is a longitudinal front view showing the structure of an example of a hearth roller for thick plate according to the present invention, and FIG. 2 is a longitudinal side view thereof.

In both figures, l is a hollow roller core made of heat-resistant steel such as HK40, and 2 is a clearance 3 on the outside of the roller core 1.
and a ceramic sleeve loosely fitted independently with a gap between them via the buffer material 4; 5 represents a stopper for restraining the movement of the ceramic sleeve 2 and the buffer material 4 in the roll axis direction.

In this example, three ceramic sleeves 2 are used per roll, but the number is not limited to this number, and the sleeve width, sleeve spacing, etc. described below are taken into consideration in addition to the furnace size and roll body length. be determined appropriately. However, since it may not be possible to pass a material to be processed having a small width with only two or so, the number is usually three or more.

The material of ceramic sleeve 2 is Si+Na, ZrO
General-purpose ceramics such as □, SiC, and Alto3 are used singly or as a mixture or composite with metal, but from the viewpoint of thick plates, high-strength Si3N4 or Z"
0! Particularly preferred are ceramics containing as a main component.

The particle size of ceramics is 5μ from the viewpoint of thick plate use.
It is preferably less than m, particularly 3 μm or less. That is, 3 μm
If the particle diameter is too large, particularly 5 μm or more, the particle bonding strength decreases, the crack propagation speed increases, and the impact load of the thick plate may not be withstood.

The thickness of the ceramic sleeve 2 is preferably 20 to 50 mm. If it is less than 20 mm, it is difficult to manufacture and may not be able to withstand the impact load caused by the thick plate. If it exceeds 50 mm, the load on the roll core 1 increases. This is disadvantageous in terms of creep deformation.

The length of the ceramic sleeve 2 is determined to reduce the load on the roll core 1 and expand the applicable thick plate size.
It is desirable to keep the total to 1/2 or less of the body length of the roll. Regarding the individual sleeve length, if the length of each sleeve is less than 200 m, the number of sleeves will increase, and the number of sleeves will increase accordingly, and the overall length will increase. The weight of the sleeve increases, leading to a decrease in creep strength, and if it exceeds 400m++, the weight of each sleeve increases, causing deflection of the roll core l, which poses a risk of creep failure. ■The evening range is preferable.

If the sleeve width is limited to this range, the roll core 1
Sleeve breakage caused by bending can be prevented.

It is desirable that the interval between the ceramic sleeves 2 be equal to or longer than the sleeve length, especially from the viewpoint of thick plates. If it is less than the sleeve length, the total weight of the sleeve applied to the roll core l increases, which is disadvantageous in terms of creep deformation.

Needless to say, these sleeve dimensions are appropriately selected from the above-mentioned preferred range depending on the scale of the furnace.

The loose II material 4 is interposed to prevent the sleeve 2 from directly hitting the roller core 1 and causing breakage of the sleeve 2 when the thick plate collides with the ceramic sleeve 2. Specifically, Any material may be used as long as it is softer than the material of the sleeve 2 and can withstand the temperature of the furnace atmosphere, such as ceramic fibers, mild steel pipes, and wires.

The clearance 3 is for absorbing thermal expansion between the roller core 1 and the ceramic sleeve 2, and only needs to have a size necessary for absorbing this. Normally, at room temperature, the difference in diameter (for example, the difference between the inner diameter of the ceramic sleeve 2 and the outer diameter of the cushioning material 4) is maintained by 5 degrees or more and 6'.

The clearance 3 is provided between the ceramic sleeve 2 and the cushioning material 4 in the illustrated example, but this is because the cushioning material 4 is attached to the outer surface of the roller core l, and the clearance 3 is provided between the ceramic sleeve 2 and the buffer material 4. When the loose II material 4 is installed in advance on the inner surface of the roller core 1 and the cushioning material 4, a clearance 3 is naturally formed between the roller core 1 and the cushioning material 4.

The stopper 5 is for preventing movement of the ceramic sleeve 2 and the cushioning material 4 in the roll axis direction, and not only prevents the ceramic sleeve 2 from shifting relative to the roll core 1, but also prevents the ceramic sleeve of the cushioning material 4 from shifting. Another purpose is to prevent the sleeve 2 from being misaligned with respect to the sleeve 2, thereby stabilizing the effect of preventing breakage of the sleeve 2.

Any structure and attachment method for the stopper 5 may be used as long as it can prevent the sleeve 2 and the cushioning material 4 from moving in the roll axis direction.

In the hearth roller with the above configuration, the rotation of the roller core 1 is transmitted to the sleeve 2 by the weight of the ceramic sleeve 2 via the cushioning material 4, and during sheet passing, the weight of the thick plate to be conveyed is also added, causing the rotation of the roller core 1. The plank can be advanced by 117 steps without any trouble by following the above.

Next, the effects of implementing the present invention will be described.

Furnace internal dimensions: 1fi 4.6m, furnace height 2m, furnace length 30m,
The hearth roller has a body length of 4.6m, an outer diameter of 300++A, an inner diameter of 260mm, a wall thickness of 20mm, and is made of heat-resistant steel of HK40.The hearth roller is placed in a roller hearth furnace with an atmospheric gas of N2 and a maximum operating temperature of 1000°C. As body 1, the outside has an inner diameter of 330 mm, an outer diameter of 370 mm, and a wall thickness of 20 mm.
Three ceramic sleeves 2 having a diameter of 400 mm and a material of 5 iJa (90%) were loosely fitted into each roll at intervals of 850 mm. As the cushioning material 4, ceramic fiber was wound around the roll core 1 at the fitting portion of the sleeve 2 to a thickness of 51 mm, and the clearance 3 was the difference between the outer diameter of the cushioning material 4 and the inner diameter of the sleeve 2, which was 20 mm.

Figures 5 (a) to 4 show the thickness distribution, plate width distribution, and star-shaped distribution of thick plates with an average plate size of 1720 m, an average plate width of 1900 m, and an average unit weight of 1.9 tons. Although 567 tons of heat treatment was carried out in the above-mentioned roller hearth furnace, there were no surface defects such as big bumps on the back side of the thick plate, no deflection of the roller core 1, and no breakage of the ceramic sleeve 2. The heat pattern in this heat treatment is shown in FIG. Furthermore, this roller hearth furnace has produced 600
Although the parts above 0) have been heat treated, no abnormalities have been observed in either the product or the hearth roller.

〔Effect of the invention〕

As is clear from the above description, the hearth roller of the present invention incorporates ceramics into the roller for thick plates, which has a large static load and impact load that is incomparable to thin plates, and the ceramics can only prevent surface flaws on the original plate. This effectively prevents cracking of the ceramics and deflection of the roll core caused by the increased weight of the ceramics.
As a result, the quality of the thick plate after heat treatment can be improved without any restrictions on the plate size and with sufficient durability for practical use.

Therefore, according to the hearth roller of the present invention, it is possible to avoid the increase in cost associated with repairing surface flaws on the thick plate, and the cost required for replacing the roll is also reduced, resulting in a large gain in the heat treatment cost of the thick plate and the finished product cost as a whole. Become something.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view showing the structure of an example of a hearth roller for a j-zo plate according to the present invention, FIG. Figure 4 is a creep curve diagram of NK40 material showing the theoretical background of
A) to C → are plate thickness distribution diagrams (A) of thick plates used in the examples of the present invention, plate width distribution diagrams C-cut and i overlap right diagram (C), and 6th
The figure is a heat pattern diagram of the heat treatment applied to the floor in the same example. In the figure, 1; roller core, 2; ceramic sleeve, 3
: Clearance, 4; Cushioning material, 5: Straight bar. Figure 1 Figure 2 Figure 3 Temperature (°C) Width (m) Procedure Nail 11 Original (self-motivated) 6゜August 1986 2. '3, 1986 Patent Application No. 150954 Re1. Title of the invention: Hearth Roller for Thick Plate 3. Relationship with the amended person's case. Address of the patent applicant: 5-44 Kawaramachi, Higashi-ku, Osaka (Amakusa Building) (Documents) (Date of optical transmission Showa year, month, day) Contents of the amendment in the "Detailed Description of the Invention" column of the specification subject to amendment, "Konofureni" on page 2, line 12, should be amended to "Konofureni". Masu.

Claims (1)

[Claims] (1) A hollow roller core body (1) made of heat-resistant steel, with a clearance (3) and a cushioning material (4) on the outside thereof,
and a plurality of ceramic sleeves (2) loosely fitted independently from each other at intervals in the axial direction of the roller, and a stopper for restraining movement of the sleeves (2) and the cushioning material (4) in the axial direction of the roller. (5) A hearth roll for thick plates comprising: