JP2509293B2 - Pinch rolls for hot runner rolls and coilers - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hot run table roller and a coiler pinch roll having excellent wear resistance and seizure resistance.

(Prior Art) A strip hot-rolled by a hot strip mill is manufactured by a general manufacturing process as shown in FIG.
In a so-called hot run table having a length of 0 to 150 m, controlled cooling is performed according to intended quality, and the coil is wound by the winder 31. In the figure, 32 is a finish rolling roll, 33 is a top pinch roll for a coiler, and 34 is a bottom pinch roll. Pinch roll for coiler 33,34
Is usually a Co-based stellite overlay material, F
A high-hardness overlay layer is formed as a layer to be used by e-based Cr-Mo overlay material.

The hot run table is a roller with a diameter of 300-350 mm.
35 are arranged at intervals of 350 to 500 mm, and the total number of rollers reaches 250 to 350.

The controlled cooling is performed in the cooling zone B provided in the middle of the hot run table. A large number of cooling headers 36 are provided in the cooling zone B, and cooling water 37 is jetted toward the strip. Therefore, in the cooling zone B, a water film is formed on the roller surface.

Before and after the cooling zone B, semi-wet zones A and C
Is provided. In the semi-wet zones A and C, cooling water is not supplied in order to stably convey the strip.

Usually, the hot run table roller is rotationally driven so as to have a peripheral speed that is 8 to 20% faster than the transport speed in order to stably transport the strip. Since the strip conveying speed is usually about 800 to 1200 m / min, the strip and the roller surface cause a severe relative slip. Further, due to the presence of the cooling water for control cooling and the heat of the strip, the roller surface is in a corrosive atmosphere, and the progress of wear is remarkable.
Therefore, excellent wear resistance is required for the roller material.

A roller with a surface hardness of Hs
High Cr steel rollers, which are said to be 65 to 75, are known. In fact, Cr
When a high Cr steel roller of 8 wt% or more was used in the cooling zone, the amount of wear was 2-3 mm per year in terms of diameter reduction, which was a good result.

However, the high Cr steel roller has a drawback that it has poor thermal conductivity and anti-seizure property cannot be expected. Once seizure occurs, seizure flaws are transferred to the strip surface, degrading product quality. Therefore, the high Cr steel roller is actually used only in a cooling zone where seizure resistance is not required because a water film is formed on the roller surface.

Therefore, in the semi-wet zone where no water film is formed on the roller surface, it is not possible to use a high Cr steel roller with excellent wear resistance, and in general, seizure-resistant ductile cast iron rollers and 3% Ni cast iron rollers are not likely to occur. Laura is used. However, since these rollers have poor wear resistance, the wear is remarkable, and the reduction amount of the roller diameter reaches 10 or more mm per year, which causes a problem that the replacement cost of the roller significantly increases.

(Problems to be Solved by the Invention) With respect to such a problem, as disclosed in JP-A No. 61-557, a graphite crystallized high chromium cast iron material having both wear resistance and seizure resistance is used. A roller for a semi-wet zone having a transport layer has been developed.

However, the graphite crystallized high chromium cast iron material has a Cr content of 5
Since it is contained in a large amount of ~ 10%, it cannot be said that the material has sufficient seizure resistance, and the Cr carbide formed in the matrix is M ₇ C ₃ type with high hardness, The shape is narrow from the surface of the use layer to the inside, and the resistance to the shearing force acting on the surface of the use layer is not sufficient, and wear is likely to occur due to falling off at the peripheral edges of the graphite particles. There is a demand for improved sex. Furthermore, expensive Ni 4.5-10%
Since it is contained in a large amount, there is a problem that it is inferior in economic efficiency.

On the other hand, in the coiler pinch roll, the welding bead at the time of overlay welding is exposed in the used layer, and the wear resistance of this part is inferior, so rough skin and seizure easily occur, and the bead pattern is transferred to the rolled steel plate. There was a problem.

The present invention has been made in view of the above problems, and provides a hot run table roller and a coiler pinch roll which have excellent seizure resistance and wear resistance as a use layer and which are also excellent in economic efficiency. To aim.

(Means for Solving the Problems) The hot run table roller and the pinch roll for a coiler of the present invention made to achieve the above object are C: 2.8 to 3.5%, Si: 1.5 to 2.5%, Mn: 0.5 to 1.0. %, P: 0.1% or less, S: 0.08% or less, Ni: 3.5 to 4.5% (excluding 4.5%), Cr: 3.5 to 5.0% (excluding 5.0%), Mo: 0.3 to 1.0%, balance It is a feature of the invention that the use layer is formed of a graphite crystallized chromium cast iron material that is substantially formed of Fe and has a structure mainly composed of Cr carbide, graphite and bainite.

(Function) The conveyance use layer of the roller of the present invention is Si: 1.5 to 2.5%, Ni: 3.
Since it was formed from a chromium cast iron material with a specific composition of 5 to 4.5% (excluding 4.5%) and Cr: 3.5 to 5.0% (excluding 5.0%), graphite was produced along with crystallization of high hardness Cr carbide and cementite. Is crystallized and has both abrasion resistance and seizure resistance. Cementite does not have a directional morphology like Cr carbide and has a large grain size, so that it has good resistance to falling wear, and the coexistence of both carbides improves wear resistance.

Further, since the matrix structure is composed of a tough structure mainly composed of bainite, it is possible to further prevent the wear due to the falling of carbide on the peripheral edges of the graphite grains, and it is possible to improve the wear resistance.

Further, in the case of a hot run table roller, as a result of the toughness of the transport-use layer itself, it is not necessary to form an inner layer made of a tough material on the inner surface of the transport-use layer to form a composite, and the productivity of the roller can be improved. it can.

(Example) Hereinafter, the reason for limiting the components of the graphite crystallized chromium cast iron material forming the use layer of the roller and roll of the present invention will be explained, and the application to the use layer will be mentioned. In the following, all component units are% by weight.

C: 2.8-3.5% C combines with Cr and Fe to form high hardness Cr carbide and cementite, which contributes to the improvement of wear resistance and crystallizes into graphite by the graphitization promoting elements of Si and Ni. . If it is less than 2.8%, formation of Cr carbide and crystallization of graphite are reduced, and wear resistance and seizure resistance deteriorate. On the other hand, if it exceeds 3.5%, the crystallization of graphite becomes excessive with the Cr content in the present invention, and wear resistance is deteriorated.

Si: 1.5 to 2.5% Si is an element necessary for crystallizing graphite together with Ni. When the Ni content in the present invention is less than 1.5%, the graphite hardly crystallizes, while when it exceeds 2.5%, the graphite is excessively crystallized, and the wear resistance and toughness deteriorate.

Mn: 0.5-1.0% Mn is required for deoxidation and desulfurization in the manufacturing process. If it is less than 0.5%, the above-mentioned action is insufficient, while if it exceeds 1.0%, the toughness of the matrix structure deteriorates.

P: 0.1% or less P is preferably as small as possible, and is 0.1% or less from the viewpoint of preventing embrittlement.

S: 0.08% or less Since S makes the material brittle like P, the smaller the content, the better. S: 0.08% or less.

Ni: 3.5 to 4.5% (excluding 4.5%) Ni is contained to make the matrix structure finer, improve toughness, and crystallize graphite. If it is less than 3.5%, a sufficient effect cannot be obtained, while if it is more than 4.5%, retained austenite is increased and seizure resistance is impaired. In addition, it becomes a factor of high cost.

Cr: 3.5 to 5.0% (excluding 5.0%) Cr combines with C to form a high hardness Cr carbide of about Hv1350, which contributes most to the improvement of wear resistance. If it is less than 3.5%, the amount of Cr carbide is small and sufficient wear resistance cannot be secured. On the other hand, when the content is 5.0% or more, almost all the carbides formed are Cr carbides, the formation of cementite is almost eliminated, the crystallization of graphite is suppressed, and the seizure resistance and wear resistance are reduced.

Mo: 0.3-1.0% Like Ni, Mo is included to strengthen the base structure. 0.
If it is less than 3%, there is almost no effect, while if it exceeds 1.0%, the retained austenite is stabilized, which is not preferable.

The graphite crystallized chromium cast iron material of the present invention is composed of the above alloy components, and the balance being Fe and impurities inevitably mixed.

The chromium cast iron material is in the as-cast state, and retained austenite, pearlite and high hardness Cr carbide and cementite crystallized in the matrix formed by martensite, and graphite crystallized, which is different in form from graphite. By coexisting with carbide, seizure resistance can be secured and wear resistance can be improved.

In the present invention, all or most of the matrix structure is made into a bainite structure by heat treatment to strengthen the matrix, thereby making it more difficult to remove carbides around the edges of the graphite grains and contributing to improvement in wear resistance.

In the heat treatment, the cast material is heated and held at the austenitizing temperature, and then rapidly cooled to 400 to 600 ° C., at this temperature for 5 to 15 hours.
A step of holding the material, isothermally transforming all or most of the base material into bainite, and then gradually cooling the base material is adopted.

Since the matrix of the graphite crystallized chromium cast iron material of the present invention is formed mainly of tough bainite, the cast iron material as a whole has toughness. Therefore, the cast iron material of the present invention can be used as an outer layer material that is a use layer of a hot run table roller or a pinch roll for a coiler, and in the case of a roller that does not receive a large load, a single roller (in this case, a roller thickness of Most of them also function as a transport-use layer.)

When the cast iron material of the present invention is used as an outer layer material of a composite roller or a composite roll, a tough cast iron material such as high-grade cast iron or ductile cast iron is usually used as the inner layer material.

The hot run table roller or pinch roll of the present invention is provided as a composite roller, a roll, or a single roller, but in any case, the cylindrical body portion having the used layer is cast by the centrifugal casting method. It is customary.

After centrifugal casting of the body, in order to mainly use bainite as the base of the used layer, the above-mentioned heat treatment is performed, and then the shaft is assembled at both ends of the body and machined to a predetermined product roller. To be done. The term “roller” as used in the present invention also includes the cylindrical body itself that forms the body.

Next, specific examples of the hot run table roller of the present invention will be described.

First, a manufacturing example of a single roller having a body outer diameter of 320 mm, a body inner diameter of 195 mm, and a body length of 1730 mm will be described.

(1) The molten roller material according to the present invention shown in Table 1 below was cast at 1380 ° C. in a centrifugal casting mold rotating on a casting machine and gradually cooled to room temperature.

(2) After the body is cast, it is heated and held at the austenitizing temperature (850 ℃) in a heat treatment furnace, then rapidly cooled to 500 ℃ and
After holding for 0 hour, the base was transformed into bainite and then gradually cooled.

(3) The results of microscopic observation of the metal structure of the body are shown in FIGS. 1 and 2.

From FIG. 1, it is known that a large amount of carbide is crystallized and graphite is crystallized in the fine bainite matrix. Further, from FIG. 2, it can be observed that graphite is dispersed and crystallized throughout the entire structure. It should be noted that FIG. 2 shows the sample which was polished but not corroded.

(4) After the body portion was machined, the shaft portions were assembled at both ends thereof to obtain a product roller.

When this roller was installed in a hot run table and tested online for 1 year, the wear amount was 0.7 in diameter reduction.
~ 1.0mm, high Cr which is said to have good wear resistance
It was confirmed that the wear resistance was superior to that of the steel roller.
In the semi-wet zone, no seizure occurred.

Next, a description will be given of a manufacturing example of a composite roller having a body outer diameter of 330 mm, a body inner diameter of 170 mm, and a body length of 1700 mm.

(1) The molten metal of the outer layer material having the chemical composition shown in Table 2 is added to the centrifugal force casting die rotating on the casting machine for a wall thickness of 50 mm (casting weight 68
0kg) It was cast. The casting temperature is 138 in both the example and the conventional example.
The temperature was 0 ° C. Incidentally, the conventional example is the graphite crystallized high chromium cast iron material disclosed in JP-A-61-557.

(2) When the inner surface of the outer layer is almost solidified (10 minutes after the start of casting), the inner layer material (ductile cast iron) shown in Table 2 is cast on the inner surface of the outer layer for a thickness of 30 mm (cast weight 300 kg) It is.

(3) The outer layer and the inner layer were completely solidified 25 minutes after the start of the casting of the outer layer. Then, after stopping the rotation and slowly cooling to room temperature, the roller body was taken out from the mold, heated and held at the austenitizing temperature (850 ° C), then rapidly cooled to 500 ° C, and held at this temperature for 10 hours, then cooled in the furnace. did.

(4) After the outer peripheral surface of the body was machined, the body was subjected to ultrasonic flaw detection. As a result, the welding between the outer layer and the inner layer was good in Example 11 and the conventional example. The amount of the outer layer melted by the inner layer molten metal was 6 to 8 mm.

Table 3 shows the results of examining the composition of the inner layer after casting. The composition of the outer layer is almost the same as the composition of the molten metal, so the description thereof is omitted.

(5) A test piece was sampled from the body obtained as described above, and the mechanical properties, seizure resistance, and wear resistance of the outer layer were examined.

 The results of examining the mechanical properties are shown in Table 4.

It is known from Table 5 that the examples of the present invention are slightly inferior in hardness to the conventional examples, but are excellent in strength and elongation and good in toughness.

 The seizure resistance was examined by a fabby test.

(I) In the Fabry test, as shown in FIG. 3, one end of the test pin 11 is fixed to the rotating machine 12 by the shear pin 13, and the other end is fixed under a constant load P to form a pair of V blocks 14,1.
The test pin 11 is rotated while being sandwiched by 4, and the presence or absence of seizure and the degree thereof are checked by the torque required for rotation.

(Ii) The test conditions for the Fabry test were as follows.

Test pin size …… φ6.5 × 40l V block size …… φ12 Test pin speed… 300rpm (0.1m / sec) Load load P ………… 35kg Test environment ………… No lubrication (iii) As a result of the Fabry test, In Example 11 and the conventional example, no remarkable rise of torque indicating the seizure state was observed, but the maximum torque required for rotation was 45 in Example 11.
kg.cm, the conventional example is 34 kg.cm, and it is known that the example has better seizure resistance than the conventional example.

Abrasion resistance is tested by a roller abrasion test as follows.
It was evaluated by measuring the diameter reduction amount.

(I) Test Procedure As shown in FIG. 4, a test roller 21 sampled from the rollers of the example and the conventional example is pressed against a steel roller (width 50 mm) 22 heated to 500 ° C. with 1500 kg to make the test roller 21. Was rotated, and the diameter reduction amount of the test roller 21 after the predetermined rotation was examined.

(Ii) Results The diameter reduction amount per 10 ⁶ rotations of the test roller was as follows.

Example 11: 0.18% Conventional example: 0.33% (iii) Evaluation It was confirmed that Example 11 was improved in wear resistance by about 45% as compared with the conventional example.

Further, a specific example of a top-pinch composite roll for a down coiler having a body outer diameter 900 mm, a body inner diameter 700 mm, and a body length 1800 mm will be described.

(1) The outer layer molten metal according to the present invention shown in Table 5 below is cast at 1,380 ° C. in a centrifugal casting mold rotating on a casting machine,
After the inner surface of the molten metal was solidified after casting, the inner layer molten metal shown in the same table was cast and gradually cooled to room temperature.

(2) Austenitizing temperature 85 in the heat treatment furnace after casting the body
After heating and holding at 0 ° C., it was rapidly cooled to 500 ° C., held at 500 ° C. for 10 hours to transform the matrix into bainite, and then gradually cooled.

(3) After the body portion was machined, a shaft portion composed of a hub and a shaft was assembled at both ends thereof to obtain a top pinch roll.

(4) When this roll was installed in the pinch roll section and subjected to an online test for 5 months, a conventionally used build-up roll was seized at the bead section, causing rough skin, while maintaining good roll skin. It was As for wear, the conventional roll is rough due to bead flaws and wear.
While it was 5.2 mm in 4.5 months, in the example roll
It was 4.5 mm in 4.5 months, which was good.

(Effects of the Invention) As described above, the hot run table roller and the pinch roll for the coiler of the present invention have the use layer of Ni: 3.5.
~ 4.5%, Cr: 3.5-5.0% graphite crystallized chrome cast iron material with a specific composition, forming Cr carbide and cementite and graphite, and forming the matrix with toughness bainite, it is extremely excellent Since it has abrasion resistance and seizure resistance, it can be sufficiently applied as a roller or a pinch roll for a semi-wet zone where a water film is not formed by cooling water, and does not deteriorate the quality of the strip. Further, as a result of the excellent life, the frequency of roller replacement can be reduced, and maintenance costs can be reduced. Further, since the expensive Ni content can be suppressed, the economy is excellent.

[Brief description of drawings]

1 and 2 are micrographs of a metallographic structure of a graphite-crystallized chromium cast iron material forming a conveyance use layer of the roller of the present invention, and the magnification is 50 times in both figures. FIG. 3 is an explanatory view of the seizure test procedure, FIG. 4 is an explanatory view of the wear test procedure, and FIG. 5 is an explanatory view of the overall arrangement of the hot run table.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroaki Katayama 64 Nishimukojima-cho, Amagasaki City, Hyogo Prefecture Kubota Iron Works Co., Ltd. Amagasaki Factory (72) Inventor Shinro Maeke, Kumuda Iron Works Co., Ltd. Company Amagasaki Factory (56) Reference JP 63-126604 (JP, A) JP 62-23969 (JP, A) JP 49-134526 (JP, A)

Claims (2)

(57) [Claims] 1. The chemical composition is% by weight, C: 2.8 to 3.5%, Si: 1.5 to 2.5%, Mn: 0.5 to 1.0%, P: 0.1% or less, S: 0.08% or less, Ni: 3.5 to 4.5. % (Excluding 4.5%), Cr: 3.5 to 5.0% (excluding 5.0%), Mo: 0.3 to 1.0%, the balance is essentially formed of Fe, and the structure is mainly composed of carbide, graphite and bainite. A hot run table roller characterized in that a use layer is formed of a graphite crystallized chromium cast iron material composed of a matrix. 2. The chemical composition is% by weight, C: 2.8 to 3.5%, Si: 1.5 to 2.5%, Mn: 0.5 to 1.0%, P: 0.1% or less, S: 0.08% or less, Ni: 3.5 to 4.5. % (Excluding 4.5%), Cr: 3.5 to 5.0% (excluding 5.0%), Mo: 0.3 to 1.0%, the balance is essentially formed of Fe, and the structure is mainly composed of carbide, graphite and bainite. A pinch roll for a coiler, wherein a use layer is formed of a graphite crystallized chromium cast iron material composed of a matrix.