JP2571377B2 - Roll for continuous casting of an arb leave type - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an arbor sleeve type continuous casting roll.

[Prior art] Continuous casting rolls are made of low alloy steel solid rolls such as SCM430, SCM822, etc., whose surface is coated with a 13Cr stainless steel weld overlay or sprayed layer, or the above low alloy steel roll shaft. (Arbor) fitted with a 13Cr stainless steel sleeve is used. Further, as an improved type of arbor sleeve type roll, there has been proposed a roll in which a Cr-Mo alloy steel or the like is applied to a sleeve and the surface of which is coated with a weld overlay of 13Cr stainless steel (see, for example, Shokai 59). −110155
issue).

[Problems to be solved by the invention]

Both conventional solid rolls and arbor sleeve rolls have good resistance to thermal fatigue cracks and oxidative wear. However, once a thermal fatigue crack occurs, in the case of a solid roll, the crack is liable to propagate to the center of the base material, and it is not uncommon for a roll break accident to occur. On the other hand, in the arbor sleeve type roll, since thermal fatigue cracks stop at the interface between the arbor and the sleeve, the risk of breakage is small, but the sleeve is liable to penetrate and its service life is short. The same applies to the improved arbor sleeve type roll.

Furthermore, recent continuous casting operations tend to be continuous-continuous casting and different steel continuous-continuous casting. In this continuous-continuous casting operation, at the seam portion of the slab, once the conveyance of the slab is stopped and the seam is completely solidified and the conveyance is started, the heat effect on the rollers is greater than ever. It is severe. In addition, in the curved or vertical bending type continuous casting machine, the load applied to the roll in the range from the curved portion to the bending straightening point is greatly increased as compared with the related art. For this reason, improvement of mechanical fatigue strength as well as the above-mentioned thermal fatigue properties as properties required for the roll has been an issue.

The present invention has been made to address the above situation.

[Means and actions for solving the problems]

The present invention is an arbor sleeve type continuous casting roll formed by shrink-fitting a sleeve to an arbor, wherein the sleeve is
On the inner surface of the outer layer made of 13Cr stainless steel,
1.5%, Ni: 0.5 ~ 1.5%, C: 0.1 ~ 0.5%, Si: 0.3 ~ 0.6%, Mn:
0.7~1.4%, Mo: 0.2~0.5%, V: 0.05~0.15%, the balance substantially Fe, 0.2% yield strength 80 kg / mm ² or more, a high strength low alloy steel of tempered martensite structure A two-layer sleeve having an inner layer portion.

The sleeve fitted to the arbor (roll shaft) of the continuous casting roll of the present invention is a two-layer laminate of an inner layer portion and an outer layer portion, and the inner layer portion is formed of a low alloy steel having the above component composition. Cr (0.5-1.5%) increases the strength and Ni (0.5-1.5%)
%) Contributes to the improvement of strength and toughness, and Mo (0.2 to 0.5)
%) Improves the resistance to temper softening and V (0.05 to 0.15%).
%) Is effective in improving the strength and toughness due to the refinement of the crystal grains. C (0.1-0.5%) contributes to the strengthening of steel by forming solid solution and carbide in steel, Si (0.3-0.6%) is a deoxidizing agent, Mn (0.7-1.4%) is deoxidizing and desulfurizing It is an element contained as an agent. This low alloy steel undergoes a tempering treatment at a temperature of 500 to 600 ° C. after quenching from a temperature of 900 to 1000 ° C., thereby forming a tempered martensite structure. The inner layer has a high 0.2% proof stress of 80 kg / mm ² or more, and exhibits excellent resistance to thermal fatigue and mechanical fatigue.

The outer layer made of 13Cr stainless steel is laminated on the surface of the inner layer to provide the heat resistance and abrasion resistance required for the sleeve in contact with the continuous cast piece. As a material with excellent wear resistance, it is a material grade that has been applied as a coating material on the body surface of a continuous casting roll, for example, C: 0.03 to 0.08
%, Si: 0.3-1%, Mn: 0.3-1.5%, Cr: 11.5-15%, balance F
Those consisting of e are preferably used.

The two-layer sleeve can be manufactured by various methods. For example, a method is employed in which a centrifugal casting tube made of high-strength low-alloy steel is used as an inner layer member, and a weld overlay or a thermal spray layer made of a heat-resistant and wear-resistant material is formed as an outer layer member on the outer peripheral surface. In centrifugal casting, a 13Cr stainless steel melt is cast into a mold to form a cylindrical abrasion resistant outer layer by the action of centrifugal force, and then a high-strength, low-alloy steel melt is cast inside the inner layer. It can also be manufactured by forming a hollow cylindrical body.

The thickness of the two-layer sleeve may be determined appropriately. For example, good results can be obtained by setting the thickness of the inner layer to 20 to 50 mm and the thickness of the outer layer to 0.5 to 5 mm.

After forming the two-layer sleeve composed of the inner layer and the outer layer, the inner layer (high-strength low-alloy steel) is subjected to quenching and tempering for refining. The quenching process is 900-100
It is performed by quenching from 0 ° C.
This is performed by heating and maintaining the temperature in a temperature range of 600 ° C. The lower limit of the quenching temperature is set to 900 ° C. in order to obtain a uniform austenite phase, and the upper limit is set to 1000 ° C. at higher temperatures because the structure becomes coarse and the strength and toughness decrease. The steel structure becomes a martensite phase by quenching. The tempering temperature is 500-600 ° C.
If the temperature is lower than ℃, the effect of improving strength and toughness is insufficient.
This is because in a high temperature range exceeding ℃, the strength is reduced due to the coarsening of carbides and the like. By the tempering treatment, the steel structure becomes a tempered martensite structure, high strength and high toughness are provided, and good crack resistance against thermal and mechanical fatigue is secured.

The heat treatment is performed at an appropriate stage according to the method of manufacturing the two-layer sleeve. For example, in the case where the outer layer portion is formed on the outer surface of a cylindrical inner layer member by a thermal spraying method, after the thermal spraying, a fusing treatment in which the outer layer portion is heated to about 900 ° C. in order to strengthen the adhesive force at the interface between the sprayed layer and the inner layer member. After completion of fusing, quenching is performed by rapidly cooling from the same temperature, and then tempering is performed.

The double-layer sleeve thus manufactured is shrink-fitted to an arbor prepared separately, and machine-finished at a necessary portion such as the surface of the sleeve, thereby completing a desired arbor sleeve type roll. The material of the arbor may be a conventionally used low alloy steel such as SCM430 or SCM822.

[Action]

The roll for continuous casting of the present invention has heat resistance and abrasion resistance due to the outer layer portion of the sleeve, and also has high strength and excellent resistance to thermal fatigue and mechanical fatigue due to its inner layer portion, Even if a fatigue crack is generated in the outer layer, the propagation of the crack is effectively prevented or delayed due to the high fatigue strength of the inner layer.

[Examples] [I] Production of test rolls (a) Roll A 13Cr stainless steel cladding layer (outer layer member) on the surface of a high strength low alloy steel centrifugal casting tube (inner layer member) by plasma welding To form Then, after quenching at 950 ° C and water cooling, tempering at 550 ° C, shrink-fitting into a separately prepared low-alloy steel (SCM430) arbor, machining, and adding An inventive roll (this is referred to as a test roll A) was manufactured. (10) is an arbor, (11) is a cooling water hole penetrating the axis of the arbor, (20) is a two-layer sleeve, (21) is an inner layer portion, and (22) is an outer layer portion. The materials and dimensions of each member are as follows.

Arbor: Material (SCM430): C: 0.3%, Si: 0.21%, Mn: 0.7%, Cr: 1.
08%, Mo: 0.21%, balance Fe.

Outer diameter: 270φ Sleeve inner layer: Material C: 0.15%, Si: 0.55%, Mn: 0.8%, Cr: 1.2%, Ni:
0.8%, Mo: 0.4%, V: 0.12%, balance Fe.

Wall thickness: 45 ^t Sleeve outer layer Material (13Cr stainless steel layer): C: 0.08%, Si: 0.6%, Mn:
0.8%, Cr: 14.0%, balance: Fe. Wall thickness: 5 ^t . Further, the following two test rolls B and C were used as comparative examples.
Was made.

(B) Roll B A conventional centrifugal casting tube made of 13Cr stainless steel (component composition is the same as the outer layer of the roll A) is shrink-fitted on the peripheral surface of an arbor of the same material as the roll A as a sleeve. Roll B equivalent to arbor sleeve type roll
Produced. Arbor outer diameter: 270φ, sleeve thickness: 50 ^t .

(C) Roll C By forming a weld build-up layer of 13Cr stainless steel (the component composition is the same as the outer layer portion of the roll A) on the peripheral surface of the arbor of the same material as the roll A, it is equivalent to a conventional solid roll. Roll C to be manufactured. Arbor outer diameter: 360φ, overlay thickness: 5 ^t .

[II] Fatigue test As shown in FIG. 3, each test roll R (A, B, C) was
The test roll (R) is brought into contact with the lower surface of the roll (R ₁ ) corresponding to the continuous cast piece (slab) and pressed by the pressing rolls (R ₂ , R ₂ ) so that the bending stress of the test roll (R) becomes 15 kg / mm. While adjusting the load on the test roll, the surface of the roll (R ₁ ) was heated with a burner (B) to reduce the contact temperature with the test roll (R) by 10%.
While maintaining the temperature at 00 ° C., the surface of the test roll (R) is rapidly cooled by spraying cooling water from the nozzle (N). Under the above thermal fatigue and mechanical fatigue conditions, the test roll (R)
The relationship between the number of rotations and the fatigue crack depth was measured for each test roll, and the results shown in FIG. 2 were obtained. In FIG. 2, each of the curves (A), (B) and (C) represents a test roll A,
The results of B and C are shown. The test roll A of the present invention is a conventional arbor sleeve type roll (test roll B).
In comparison with the solid roll (test roll C), it is shown that the crack growth is effectively suppressed even under the condition where severe thermal fatigue and mechanical fatigue are superimposed.

〔The invention's effect〕

The arbor sleeve type continuous casting roll of the present invention has excellent resistance to the growth of cracks caused by thermal and mechanical fatigue, as compared with conventional arbor sleeve type rolls and solid rolls. Further, the oxidation resistance and abrasion resistance required on the surface of the sleeve are ensured by the outer layer of the sleeve. Therefore, the continuous casting roll of the present invention exhibits a stable long-term service life even after fatigue cracks occur in the sleeve, and contributes to the stabilization and efficiency of the continuous casting operation. It is also possible to cope with severer operations of casting and different steel series continuous casting.

[Brief description of the drawings]

FIG. 1 is a partially sectional front view showing an embodiment of the roll of the present invention,
FIG. 2 is a graph showing the relationship between the number of rotations of the roll and the fatigue crack depth, and FIG. 3 is an explanatory view of a fatigue strength test procedure relating to the example. 10: arbor, 20: double-layer sleeve, 21: inner layer, 22: outer layer.

Claims (1)

(57) [Claims] 1. An arbor sleeve type continuous casting roll in which a sleeve is shrink-fitted to an arbor, wherein the sleeve comprises:
On the inner surface of the outer layer made of 13Cr stainless steel,
1.5%, Ni: 0.5 ~ 1.5%, C: 0.1 ~ 0.5%, Si: 0.3 ~ 0.6%, Mn:
0.7~1.4%, Mo: 0.2~0.5%, V: 0.05~0.15%, the balance substantially Fe, 0.2% yield strength 80 kg / mm ² or more, a high strength low alloy steel of tempered martensite structure An arbor sleeve type continuous casting roll excellent in fatigue crack resistance, which is a two-layer sleeve having an inner layer portion.