JPS6016495B2 - Roll manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides for the production of centrifugally cast Adamite rolls.
The purpose is to provide a high-hardness Adamite roll with excellent quality at a low cost by heat treatment after casting.

Generally, in the finishing front stand of a hot strip mill in the thin plate rolling process, a roll made of adamite material, which is less prone to roughening and has excellent wear resistance, is used as the roll for the front stand.

As is well known, this adamite material roll usually has a weight percentage of C: 1.0 to 2.8, Si: 0.3 to 1.5, Mn;
0.3-1.5, Ni; 0.3-2.0, Cr; 0.5
~2.0, Mo: 0.2~2.0, the remainder is made of a material essentially consisting of Fe, and is cast as a single roll that integrally forms the body and shaft core, and the roll material after casting is heated at high temperature. It has been subjected to diffusion heat treatment, spheroidizing dawn anchor, and quenching and tempering heat treatment, and its hardness is usually Hs45 to 6 degrees Fahrenheit. On the other hand, when Adamite material rolls are used as rolls for front and rear stands, there is almost no problem when rolling ordinary steel materials, but when rolling special steel sheets such as stainless steel materials and high C materials, there are no problems. Its deformation resistance is higher than that of rolled steel.
In addition, since the material itself is hard, the wear resistance of the rolls is poor, and the so-called top marks and tail marks, which are the dents on the roll surface that occur when relatively low temperature parts such as the top and tail of the rolled material pass through. This can become a problem, causing troubles such as early roll reshuffling.

In order to solve this problem, it is necessary to increase the hardness of the roll itself, but in the conventional casting production of single adamite rolls, increasing the hardness to Hs60 or higher increases the residual stress of the rail, making it difficult to manufacture. There is a problem in that the same part of the ear breaks during use, and it is not practicable. On the other hand, it is conventionally known to obtain a composite roll with high hardness on the roll surface and strong rut resistance on the roll axis by casting or other methods, but the present invention focuses on this composite roll structure, and By using a centrifugal force casting method, we cast a composite roll using adamite material and a shaft core made of spheroidal graphite cast iron, and by uniquely applying a special heat treatment method to this composite roll material, we created an adamite outer shell. The hardness of the material layer is 360 to 75 days, and the shaft core is made of spheroidal graphite cast iron, making it possible to provide a high-hardness Adamite roll that maintains strong rutting properties. , by centrifugal casting means, the outer shell is in weight percent C;1.
0-2.8, Si; 0.3-1. Fu Mn; 0.3-1
．． 5 Ni; 0.3 to 2.0, Cr; 0.5 to 2.0,
Mo: 0.2 to 2.0, a composite roll made of an adamite material with the remainder substantially made of Fe, a core part made of a spheroidal graphite cast iron material, and the outer shell and the core part are integrated by welding. This composite roll is then heat-treated to diffusion-temperate the entire roll at 95,000 to 10,500 C, and then the entire roll is transformed into A, A at a temperature above the transformation point, and a spherical shape at a temperature within 200 C from the transformation point. After being desensitized and then cooled to about 30,000 degrees, only the outer shell was rapidly heated to about 90 degrees.
The core is maintained at an aging temperature of 0 qo or more, and even if the quenching temperature is reached, the part corresponding to the shaft core remains below the transformation point, and only the outer shell is rapidly cooled to undergo dawn aging. After that, the entire roll is heated to 50,000 to 60,000 and subjected to tempering heat treatment to obtain a high hardness Adamite roll.

The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 shows a conventional Adamite roll made by single-piece casting, in which the body 3 and the shaft core 4 are both integrally formed. 1 is a high-hardness Adamite roll formed by a centrifugally cast composite roll obtained by the method of the present invention, and numeral 1 indicates an outer shell of adamite material formed by centrifugal force casting, and 2 indicates a bag core made of spheroidal graphite cast iron material.

In the present invention, first, in the same way as the casting production of a composite roll by the known centrifugal casting method, C; 1.0 to 2.8, Si; .3~1
．． 5, Nm; 0.3-1.5, Ni; 0.3-2.0,
A molten Adamite material consisting of Cr: 0.5-2.0, Mo: 0.2-2.0, and the remainder substantially Fe is cast to form an outer shell 1 made of Adamite material, and then a molten spheroidal graphite cast iron material is cast. and cast the mari core part 2 made of spheroidal graphite cast iron material.
A composite roll material in which both are welded and integrated is obtained, and this roll material is subsequently subjected to heat treatment of 950 qo to 1
A diffusion racing anchor that heats the entire roll at a temperature of 05 pi○,
, A above the transformation point, improve the matrix structure at a temperature within 200 qo from the transformation point, that is, perform spheroidization dawn anchor heat treatment, then cool to about 300 oz, then continue to rapidly heat only the outer shell 1 to form an ant of 900 oz or more. The shaft center part 2 is kept at the input temperature, and the shaft core part 2 is
, At a temperature below the transformation point, the roll is cooled by forced air cooling or fog water cooling, etc., and then heated to 5000 ml.
By tempering at 0 to 600 qo, the hardness of the outer shell 1 is adjusted to Hs 60 to 75.More details will be explained below. special quenching,
By tempering, the hardness is adjusted to Hs 60 to 75. Generally, the heat treatment for Adamite rolls involves a series of heat treatments: diffusion sintering → spheroidizing sintering → dawn heat treatment, and tempering treatment. It is publicly known.

Furthermore, in order to increase the hardness of the roll surface using adamite material, it is also known to perform rapid cooling such as water cooling after holding the roll at the quenching temperature. However, although these methods are possible for small castings, they are theoretically impossible for castings with large shapes and volumes, such as rolling rolls for hot strip mills, which are the subject of this invention. Even if it is possible, it will be difficult in actual work, and if you try to secure a hardness of Hs 60 to 75 after quenching and tempering, a large residual stress will remain, leading to problems such as cracking during heat treatment and breakage during use. They are definitely connected. Therefore, in order to reduce this large residual stress, it is a great advantage to make the bag core 2 a cast iron material with a small elastic modulus, that is, a spheroidal graphite cast iron material according to the present invention. , the heat treatment necessary for the Adamite roll material is applied only to the outer shell 1, and the heat treatment for the spheroidal graphite cast iron material of the shaft core part 2 requires only two heat treatments: the initial diffusion bran anchor and the spheroidized anchor. Sufficient rice toughness is obtained, and the remaining dawn hardening and tempering heat treatments are not necessary. However, in order to exhibit the toughness of the adamite material of the outer shell 1 and its properties as a rolling roll used for hot strip mill finishing front stand rolls, etc., the above-mentioned heat treatment and tempering heat treatment are essential. In the invention, only the adamite part of the outer shell 1 is rapidly heated, and after reaching the dawning temperature, it is then forcibly cooled by air, and then it is rapidly cooled by spray water cooling etc. and subjected to competitive treatment, and then tempering heat treatment is performed. However, this can be effectively concentrated on the outer shell 1, and an increase in hardness can be effectively obtained.

This heat-treated rod, the spheroidal graphite cast iron member of the shaft core part 2, is
Even with the rapid heating of the outer shell adamite material, almost no temperature increase was observed, and even when the dawn temperature of the outer shell 1 was heated to 90,000, the temperature at the shaft core remained at about 600°C or higher. Therefore, when rapidly cooling from the quenching temperature, there is heat that escapes to the roll surface side by cooling means such as air cooling or water cooling, and heat that escapes to the scale core 2 by heat conduction, and the entire roll is simply heated. However, compared to the case where the outside of the roll is forcedly cooled, an extremely fast cooling rate can be obtained, and the desired increase in hardness can be reliably expected. Next, a technical explanation of the heat treatment conditions of the present invention is as follows.

<Diffusion sintered anchor; 950-1050qo> This is done for the purpose of component polarization and homogenization of the structure.

Therefore, for diffusion moderation, the higher the temperature is, the more effective it is (lower than the solidus line in the phase diagram), but from an industrial perspective, it is set to 1050 oo or less in consideration of energy consumption, furnace life, etc. Also 9
If it is less than 50 oo, the diffusion rate in the metal solid is slow and takes a long time, and diffusion annealing is meaningless. Spheroidizing race anchor; A, above A, 120,000> Spheroidizing heat treatment is performed before quenching and tempering heat treatment, the remaining primary cementite is cut with a diffusion hammer, and the base cementite is spheroidized. This treatment can significantly improve toughness.

Regarding the temperature, it is necessary to have an austenite region at or above the A transformation point, but if the temperature exceeds the A point or 20,000, cementite will dissolve into the austenite and no spheroidization will occur. <Tempering heat treatment; 500 to 60,000> Tempering is performed to reduce residual stress caused by quenching and to stabilize the quenched product.

In addition, since Adamite rolls are generally used for hot rolling, and the roll surface that comes into contact with the rolled plate rises to around 600 oo, it is possible to prevent the effects of heat during rolling by giving a thermal history in advance through heat treatment to cause structural transformation during rolling. The goal is to prevent Regarding the temperature, if the temperature is 500 oo or less, the residual stress cannot be reduced, and if the temperature is 60 qo or more, the hardness decreases significantly and the desired high hardness cannot be obtained. Next, the composition of the outer shell material used in the present invention is well known as mentioned above, and although the technical significance of the composition has been generally explained in the past, the explanation is omitted because it is not clear. . Next, specific examples of the present invention will be shown.

<Example> An outer shell adamite material having a chemical composition as shown in the table below,
700? The rut core is made of spheroidal graphite cast iron material. A hot strip mill roll having 8 x 1676 parts was manufactured by centrifugal casting means.

1st Example 2nd Example Each of the rolls described above was subjected to diffusion anchor treatment at 1030 qo for 2 feeding hours, then subjected to spheroidizing bran pure heat treatment at 820 oooh for 3 hours, and after cooling the entire roll to 300 qo, the quenching temperature was Rapid heating up to 900 qo (heating rate 300
°C/hour) and held until the temperature from the roll surface to the 6th point reached the dawning temperature, and then cooled with water cooling after spraying (cooling rate 300q
o/hour) and then subjected to tempering heat treatment at 550° C. to remove transformation stress and residual stress and to relieve strain.

After completing this series of heat treatments, the surface was processed by machining and the hardness was measured.
7. In the second example, a hardness of Hs 63 to 65 was obtained. Furthermore, when the roll of the first example was actually used as a roll of a pre-stand for hot strip mill finishing, there was no breakage and the roll had excellent roughness resistance and abrasion resistance.
In addition, in order to investigate the roll residual stress in the roll of the second embodiment, we will show the results of investigating the tensile stress in the bag direction of the shaft core part 2, which causes breakage during use. .5~7.6k9/Hiro (center of tension roll)
Met. As a result, the tensile stress in the axis direction (roll center) is as low as 6-7k9/Iso, and compared to the conventional heat treatment method that heats the entire roll, the hardness Hs has been improved by 10-12 degrees internally and externally, and residual stress has also been reduced. It was confirmed that there was almost no change. In addition, by heating the entire body with a single casting roll and making the rumored mist coating conditions more severe than before in order to increase the hardness,
The bow residual stress at the center of the o-le axis increases, and 10
It was ~16k9/boiled.

Therefore, thermal stress during use (generally 1 20 minutes after the start of rolling)
0 to 12k9/h), the material stress of coarse crystals or nest-like defects that are likely to occur at the center of the roll is exceeded, leading to breakage.
It is extremely advantageous to use cast iron with a low elastic modulus, since shrinkage cavities and the like occur in the center of this type of cast iron. Furthermore, in the roll heat treatment of the present invention, the equipment can be reduced by using a type of heat treatment furnace in which the roll neck is supported by supporting rollers and only the roll arms are heated while being rotated, without using the conventional cart type furnace. It is also advantageous and simple in terms of energy saving. The present invention is as described above, and is extremely advantageous in that it can provide an Adamite roll with high hardness that is suitable for rolling rolls and other rollers that require wear resistance and breakage resistance. .

In particular, although the present invention adopts a composite roll structure, by using Adamite for the outer shell and spheroidal graphite cast iron for the koji core, the hardness of the Adamite layer increases while maintaining the spheroidal graphite cast iron at a temperature below the A transformation point. can be obtained reliably and easily, and the quenching and tempering treatments only need to be done on the adamite material side, reducing overall heat consumption and manufacturing costs, and increasing hardness, which was difficult to achieve with single-piece cast adamite rolls. It is extremely advantageous that the hardness Hs is improved by 10 to 12 degrees under the same roll residual stress, and it exhibits excellent wear resistance and breakage resistance due to the spheroidal graphite cast iron material in the scale core, making it suitable for severe use. This can improve roll durability under certain conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a single cast Adamite roll, and FIG. 2 is an explanatory diagram of a roll according to the present invention. 1...Outer shell, 2, 4...Wisteria core, 3...Chest. Figure 1 Figure 2

Claims (1)

[Claims] 1. By centrifugal casting means, the outer shell, in weight percent, is C;1.
0-2.8, Si; 0.3-1.5, Mn; 0.3-1
．． 5, Ni; 0.3 to 2.0, Cr; 0.5 to 2.0,
Mo: 0.2 to 2.0, the balance is made of adomite material consisting essentially of Fe, the shaft core is made of spheroidized graphite cast iron material, and the outer shell and shaft core are integrated by welding. manufacturing a roll and subsequently heat treating the composite roll to diffusion annealing the entire roll at 950°C to 1050°C;
Next, the entire roll was subjected to spheroidizing annealing at a temperature above the A_1 transformation point and within 200°C from the A_3 transformation point, and then cooled to about 300°C, and only the outer shell was rapidly heated to 90°C.
The quenching temperature is maintained at 0℃ or above, and even if the quenching temperature is reached, the portion corresponding to the shaft core remains below the A_1 transformation point, and only the outer shell is rapidly cooled and quenched. A method for manufacturing a roll, characterized in that a high hardness adamite roll is obtained by heating the entire roll to 500°C to 600°C and subjecting it to a tempering heat treatment.