JP2972031B2 - High-speed steel-based sintered alloy for steel roll, roll body and manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a construction of a roll for rolling a steel material.
Wear resistant is the material,耐肌Arasei torso of <br/> high speed steel-based sintered alloy and the rolling roll excellent in seizure resistance and the like as well as
It relates to the production method.

[0002]

2. Description of the Related Art The surface of a body of a roll for hot or cold rolling of a steel material has good abrasion resistance, hardly causes rough surface (cracks, irregularities, chipping, etc.), and seizure with a material to be rolled. It is necessary for things to hardly occur. Conventionally, cast iron rolls have been used as hot rolling rolls, and forged steel rolls have been used as cold rolling rolls. Recently, as a measure to reduce the rolling conditions and to improve the service life of the roll, a roll with a sintered alloy layer having a high-speed steel-based chemical composition formed on the body surface by hot isostatic pressing sintering, etc. It has also been tried for use (JP-A-58-21856, JP-A-63-297).
No. 510).

[0003]

The high-speed steel alloy has a metal structure in which fine carbide particles are precipitated and dispersed in a hard matrix of a martensite or bainite phase by being subjected to a quenching and tempering tempering heat treatment. . Due to its hard matrix and the effect of strengthening the dispersion of carbide particles, it has good abrasion resistance and rough surface resistance, etc., and it can be expected to improve the roll life by applying it to rolling rolls. Becomes
The present invention has been made to further improve the material properties of a high-speed steel-based sintered alloy.

[0004]

SUMMARY OF THE INVENTION The steel material of the present invention
The high-speed steel-based sintered alloy for rolling rolls has C of 1.7% or less, Si of more than 0.6%, 3.5% or less, and Mn of 0.1% or less.
6% or less, Cr: 3 to 8%, Mo: 3 to 9%, W: 5 to 5%
14%, one or two or more of V, Ti, Nb: 8% or less (total amount ), B: 2% or less, Ni: 3% or less, balance substantially
It is a sintered body of high-speed steel-based alloy powder composed of Fe.
Hereinafter, the reasons for limiting the components of the sintered alloy according to the present invention will be described. All percentages indicating elemental content are weight percent .

C: 1.7% or less C is a carbide forming element, and V, Ti, Nb, W, M
Combines with o, Cr, etc. to form carbides of MC type, M ₆ C type, M ₂ C type, etc., and increases the hardness of the alloy. However, an increase in the amount of C, on the other hand, causes deterioration of the toughness of the alloy due to excessive precipitation and coarsening of the carbide and a decrease in workability.
Therefore, the upper limit is 1.7%.

Si: more than 0.6% and not more than 3.5% Si has a deoxidizing effect and an effect of improving hardenability, and also enhances corrosion resistance, especially pitting resistance. The effect of improving hardenability can be observed even when the addition is 0.6% or less, but in order to secure the effect of improving corrosion resistance, addition exceeding 0.6% is required. Further, a part of Si is replaced with an M element (W or the like) of the M ₆ C type carbide, thereby making it possible to save M element. Although these effects are increased by increasing the amount of addition, the alloy is embrittled with an increase in the amount of carbide precipitation, so the upper limit is 3.5%.

Mn: 0.6% or less Mn has a deoxidizing effect and an effect of improving hardenability. The addition amount for obtaining this effect is sufficient up to 0.6%, and a large amount of addition causes coarsening of austenite grains at a high temperature and causes embrittlement of the alloy. For this reason,
The upper limit was 0.6%. Preferably, 0.2-0.4%
It is.

[0008] Cr: 3 to 8% Cr is an element for improving the hardenability of the alloy and contributes to the improvement of corrosion resistance. This effect requires at least 3%. The effect increases as the amount of addition increases, but the effect of improving hardenability can be sufficiently obtained by adding up to about 5%. The effect of improving corrosion resistance becomes remarkable when added over 5%, and is particularly effective in enhancing pitting corrosion resistance. However, the addition of a large amount causes a decrease in impact characteristics and a decrease in softening resistance at high temperatures.
% As the upper limit.

Mo: 3 to 9% Mo is remarkably effective in improving hardenability and contributes to improvement in temper softening resistance. Further, it precipitates finely as an M ₂ C-type carbide and causes secondary hardening. These effects are ensured by adding 3% or more. However, if it exceeds 9%, the effect is almost saturated.

W: 5 to 14% W has the effect of forming a solid solution at the time of austenitization for quenching to enhance quenchability. W is a strong carbide-forming element, and is finely precipitated as M ₆ C-type carbide by tempering to bring about remarkable secondary hardening. In addition, it shows tempering softening resistance. The lower limit of the addition amount is set to 5% in order to obtain sufficient secondary hardening due to precipitation of the carbide. The effect is increased by increasing the addition, but on the other hand, the toughness and the like are reduced due to the coarsening of the precipitated carbide, so the upper limit is 14%.

V, Ti, Nb: 8% or less Each of the elements V, Ti, and Nb precipitates as fine MC-type carbides by tempering after quenching and brings about remarkable secondary hardening. The effect is increased by increasing the amount of addition, but excessive addition of carbide causes excessive precipitation of carbides, which lowers the toughness of the alloy and deteriorates the workability. Therefore, the upper limit is 8%.

[0012] The sintered alloy of the present invention, together with the above elements,
Component set containing up to 2% B and up to 3% Ni
Have

B: 2% or less B is an alternative element to C and forms boride to contribute to improvement of wear resistance. 2% B is equivalent to 1% C. In addition, solid solution in the base strengthens the base. However, the addition of a large amount lowers the melting point of the alloy and lowers the strength, so the upper limit is 2%. Preferably it is 0.5-1%.

Ni: 3% or less Ni is an austenite phase stabilizing element, and is effective in improving toughness by increasing the amount of retained austenite. However, the increase in the amount of austenite, on the other hand, causes difficulty in machining, so that it should not exceed 3%. Preferably, it is 0.1 to 2.5%.

The sintering method for producing the sintered alloy of the present invention is arbitrary, but preferably a hot isostatic pressing sintering method (HIP sintering method) is applied. According to the HIP sintering method, a high-density sintered alloy can be obtained under a uniform action of a high pressing force.

The abrasion resistance and rough surface resistance of the rolling roll
Since it is of Lumpur barrel surface problems, when applying the sintered alloy of the present invention is to b Lumpur barrel, suitable metallic material (e.g., Cr-Mo-based alloy steel JIS G4105, the same 41
It is preferable to form a roll body having a laminated structure in which a hollow or solid cylindrical body made of a Cr-Ni-Mo alloy steel of No. 03 is used as a base material and the outer periphery thereof is coated with the sintered alloy of the present invention. .

The manufacturing process of the roll body in which the surface of the metal substrate is coated with the sintered alloy of the present invention will be described.
First, metal base material (hollow or solid circle body base material)
Is surrounded by a suitable encapsulant (for example, a carbon steel cylinder), and an alloy powder (gas atomized powder or the like having a predetermined chemical composition) having a predetermined chemical composition is used as a sintering material.
m or less), the powder-filled layer is degassed, sealed, and then subjected to hot isostatic pressing sintering to form a sintered alloy layer. If the sintered alloy powder is accompanied by a relatively large amount of oxide film, a reducing gas such as a hydrogen-containing gas is introduced into the powder packed layer, the oxide film is reduced and removed under heating, and then degassed and sealed. Hot isostatic pressing sintering may be performed. The hot isostatic pressing sintering treatment is suitably achieved by maintaining the temperature at 900 to 1200 ° C. and the pressure at about 500 to 1500 kgf / cm ² for an appropriate time (about ² to 4 hours). During the sintering process, a strong close bonding relationship is formed at the interface between the sintered alloy layer and the metal substrate. After sintering is complete,
The capsule is removed by machining and the necessary shape is corrected.

After forming the sintered alloy layer on the surface of the metal substrate as described above, the sintered alloy layer is subjected to a heat treatment (quenching / tempering). The quenching / tempering treatment may be performed according to a conventional method, and the quenching temperature is about 1050 to 1250 ° C.
Preferably, the temperature is from 1100 to 1200 ° C. For cooling from the same temperature, an oil bath, a salt bath, or the like can be used, but in order to prevent cracking and cracking of the sintered alloy layer due to thermal stress. The gas (N ₂ gas or the like) may be used as a refrigerant and cooled at a controlled cooling rate (for example, 5 to 20 ° C./min) in a substantially normal pressure or a pressurized (for example, 3 to 7 kgf / cm ² ) atmosphere. .

The tempering treatment following quenching is about 500
After heating and maintaining the temperature at 徐 600 ° C., preferably 520-580 ° C., the operation is gradually cooled (for example, air-cooled) once or a plurality of times (for example, 2 to 4 times).

In the sintered alloy of the present invention, carbides are finely precipitated by quenching and tempering in a martensite or bainite phase or a matrix containing these phases as a main phase and a small amount of a retained austenite phase. A distributed metallographic structure is provided. The precipitated carbides occupy about 20 to 45% in area ratio, are abundant compared to the amount of carbides (usually about 10 to 15%) in general ingots, and are uniformly dispersed. The sintered alloy of the present invention has improved abrasion resistance, skin roughness resistance, seizure resistance, corrosion resistance, etc., which are desired as a material for the body of a rolling roll, etc., by the chemical composition and the metal composition. Have.

FIG. 1 shows, as a specific example of the use of the sintered alloy according to the present invention, a cross-sectional structure of a cylindrical body having a laminated structure in which a sintered alloy layer 12 is formed on the outer peripheral surface of a cylindrical metal base material 11. Is shown. The composite member 10 is used as a roll for rolling, for example, by fitting an arbor 20 separately prepared in the hollow hole. In the example of the figure, the sintered alloy layer 12 having a constant layer thickness is formed over the entire outer peripheral surface of the base material 11, but this is not always necessary, and for example, a round steel finish rolling roll or the like may be used. In the roll having the caliber, it is needless to say that the sintered alloy layer may be formed only on the circumferential groove surface, and the other portion may have a partial composite structure in which the surface of the substrate is exposed. The thickness of the sintered alloy layer 12 is not particularly limited, but in the case of a roll for rolling, if it is too thin,
Since the peeling of the sintered alloy layer is easily caused by the action of the shear stress caused by the rolling load, the thickness is preferably about 3 mm or more. However, if the thickness is too large, cracks easily occur due to thermal stress. Therefore, it is appropriate to set the thickness to about 25 mm.

[0022]

EXAMPLE A metal powder (average particle size: 200 μm) prepared to a predetermined chemical composition is used as a sintering material, hot isostatic pressing and sintering, and then quenched and tempered in the sintered alloy block. By performing the treatment, a test sintered alloy was obtained. However, the hot isostatic pressing sintering process was performed at a temperature of 1150 ° C. and a pressure of 100.
The quenching treatment is performed under the conditions of 0 kgf / cm ² and a holding time of 3 hr. The quenching treatment is performed by holding at 1200 ° C. for 1 hour in a vacuum quenching chamber and then introducing N ₂ gas (normal temperature and normal pressure) to cool the gas. In the tempering treatment, a heat pattern of heating and holding at 540 ° C. for 5 hours and allowing it to cool was repeated three times.

Table 1 shows the chemical compositions of the test sintered alloys. For each of the test sintered alloys, a hardness (Hs) measurement, a wear test, a corrosion resistance test, a seizure test, a thermal shock test, and a bending test were performed, and the results shown in Table 2 were obtained. Test No. Nos. 1 and 2 are invention examples. 101 to 105 are comparative examples.

(1) Abrasion test The specific wear amount Ws (mm ² / kg)
f) measuring (i) rotating ring: SUJ2: hardness (H _RC) 60, the rotation wheel width 3.0 mm (ii) the wear rate: 3.4m / sec (iii) Wear distance: 200 meters (iv) final load: 16 .8kg ・ f

(2) Corrosion test A test piece (test area 35 × 35, mm) was subjected to salt water (about 800
(cc + NaCl 69.5 g, concentration 8%) for 24 hours, and left to dry in the air for 24 hours. This process is repeated five times, and the pitting corrosion of the test specimen is visually observed. The numerical value in the column of "number of pits" in Table 2 indicates the number of micro-pits due to pitting generated on the surface of the test piece.

(3) Seizure resistance test By a Falex-type seizure test (pressing load: 150 kg), a mating material (SUS304 stainless steel) was pressed against the surface of the test piece, and the rotational torque was measured. The presence or absence of seizure between the sliding surfaces of the test piece and the mating material is determined (test time: 5 minutes). In Table 1, "Seizure resistance"
In the column, “” means no seizure (low torque stability), and “×” means seizure occurrence (abnormal torque fluctuation).

(4) Thermal Shock Test A test specimen (Φ25 × t5, mm) was heated to 900 ° C. for 1 hour, and then a heat cycle of heating and quenching was repeated. The presence or absence of cracks on the test piece surface was determined by die check. In Table 2, the numerical value in the column of "thermal shock resistance" indicates the number of heat cycle repetitions up to the occurrence of cracks, and the mark "○" indicates that no cracks occurred after the repetition of 20 times.

(5) Bending test The bending strength (Kgf / mm ² ) was measured by a three-point bending method.
Specimen size: 3 × 4 × 50, mm, span distance 30m
m.

[0029]

[Table 1]

[0030]

[Table 2]

The test results of the above Examples are based on the results of
This shows that gold has improved wear resistance, strength, corrosion resistance, surface roughening resistance, thermal shock resistance, etc., over conventional high-speed steel-based sintered alloys.

[0032]

The sintered alloy of the present invention has excellent and stable wear resistance, strength, corrosion resistance, rough surface resistance, seizure resistance, etc. due to its chemical composition and metal structure. By coating the surface of the metal cylinder with the sintered alloy of the present invention and using it as a body member of a rolling roll, effects such as improvement of roll life, reduction of roll maintenance, etc. are obtained, and the body surface When the state is stable, a great effect can be obtained in improving the quality of the material to be rolled. The sintered alloy of the present invention is also useful as a material for a structural part such as a mold, a bearing, a cylinder, or a surface modifying material thereof.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing an example in which a sintered alloy according to the present invention is applied to a surface of a metal substrate.

[Explanation of symbols]

 11 Metal substrate 12 Sintered alloy layer

Continuation of front page (56) References JP-A-3-285040 (JP, A) JP-A-4-124247 (JP, A) JP-A-55-148747 (JP, A) JP-A-3-287745 (JP) JP-A-56-77362 (JP, A) JP-A-50-151705 (JP, A) JP-A-58-144456 (JP, A) JP-A-49-135807 (JP, A) 63-62845 (JP, A) JP-A-62-120401 (JP, A) JP-A-48-23615 (JP, A) JP-B-48-7967 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00 304 C22C 33/02

Claims (3)

(57) [Claims] 1. C: 1.7% or less, Si: more than 0.6%
, 3.5% or less, Mn: 0.6% or less, Cr: 3 to 8
%, Mo: 3 to 9%, W: 5 to 14%, V, Ti, Nb
1 or 2 or more: 8% or less, Ni: 3% or less, B:
High-speed steel alloy powder consisting of 2% or less, with the balance being substantially Fe
High speed steel-based sintering for steel rolling rolls
Money. 2. The high-speed steel-based sintered alloy according to claim 1,
Layer on the outer peripheral surface of the roll body substrate.
Roll body of steel rolling roll. 3. A high-speed steel based on the outer peripheral surface side of the roll body base material.
Filled with alloy powder, degassed and sealed and hot isostatically pressed and sintered
3. The production of the roll body according to claim 2, wherein
Method.