JP3390779B2 - High toughness cold roll with excellent wear resistance, peel resistance and chatter mark resistance under rusting environment - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of molding, manufacturing, quenching and tempering by a powder metallurgy method.
In particular, the present invention relates to a high toughness cold roll excellent in wear resistance, peeling resistance and chatter mark resistance (corrugated uneven wear generated on the roll surface during use) under a rust generation environment.

[0002]

2. Description of the Related Art Conventionally, cold rolls are not only peeling-resistant, chatter-marking resistant, and wear-resistant, but are often used in an aqueous environment, so rust resistance is an important characteristic. The characteristics tend to conflict. For general applications, bearing steel S
UJ2 and cold die steel SKD11 series molten tool steels are used. For applications that require further wear resistance, molten or powdered high speed tool steels can be used for applications requiring rust resistance. Is S
Martensitic molten stainless steels such as US420J2 and SUS440C have been used. However, due to the recent stricter usage environment, the conventional materials have insufficient balance of wear resistance, peeling resistance and chatter mark resistance, especially in the environment where rust is generated. However, the unevenness of the roll surface, which is caused by the lack of these characteristics, causes a problem that a defective product is printed on the workpiece. In addition, long cold rolls are induction hardened to prevent bending during quenching, but conventional cold die steel, high speed tool steel and stainless steel have poor induction hardenability. There was a problem.

[0003]

As described above,
Since the conventional material is not a material designed in consideration of abrasion resistance, peeling resistance, and chatter mark resistance under the rust generation environment required for cold rolls, there are advantages and disadvantages to these characteristics, Not satisfied with sufficient characteristics. That is, when conventional materials are used for cold work rolls, bearing steel and cold die steel have insufficient rust resistance, and high-speed tool steel has wear resistance but rust resistance. Poor, and martensitic stainless steel has disadvantages such as poor wear resistance.

Further, SKD11, molten high speed tool steel, S
In US440C, etc., giant eutectic carbides with a size of several tens of μm are unevenly distributed, so that peeling accidents and chatter marks due to lack of toughness and inhomogeneity are likely to occur, and it is generally applied to long rolls. However, there is a drawback that the induction hardenability is poor. In order to significantly improve the above disadvantages and disadvantages, the present invention takes into consideration the interaction between rusting and wear, and is particularly excellent in wear resistance and peeling resistance in an environment where rust is generated, and chatter mark resistance. It is to provide a high toughness cold roll having good hardenability.

[0005]

The first aspect of the present invention is to provide weight%.
, C: 2.0 to 3.0%, Si: 2.0% or less, M
n: 2.0% or less, Cr: 15.0 to 30.0%, Mo
+ 1/2 × W: 2.0% or less, and V: 3.0 to 8.
0%, Nb: 3.0% or less 1 type or 2 types V + 1 /
2Nb contains 3.0 to 8.0%, the formula of rust wear, M =
1000 / {-7.63 + 7.58 × C (%) + 0.4
5 x Cr (%) -1.60 x Mo (%) + 2.20 x W
(%) + 1.34 × V (%) − 0.50 × Nb (%)}
With respect to 34 ≦ M ≦ 50, the second is 1% of Ni: 0.2 to 2.0% and Co: 0.2 to 8.0%.
Alloy powder containing two or more kinds and the balance Fe and unavoidable impurities produced by the HIP method or the hot extrusion method, the ratio of carbides having a particle size of 5 μm or less is 95% or more of the whole and 60 HRC or more. By quenching to a hardness and tempering, it has succeeded in achieving the above object.

The cold roll of the present invention finds and improves the evaluation characteristic value for suppressing the wear amount in a rust generation environment which is increased by repeated rust generation-wear-creation of new interface-wear. Is to balance the peeling resistance and chatter mark resistance, which deteriorate due to the elements added for this purpose. To do so, consider the composition of the carbide, the state of precipitation, the amount of precipitation, and the solid solution component in the matrix. In addition to designing the optimum components described above, it is necessary to determine the manufacturing method.

The range of each component and the reason for limitation thereof will be described. C is an important element constituting the present invention, which forms a carbide by combining with Cr, Mo, W, V, Nb, etc., and the remainder solid-solution strengthens the matrix. If it is less than 2.0%, the amount of carbide and the amount of solid solution C are small, so that the wear resistance as a cold roll is insufficient, and if it exceeds 3.0%, the amount of carbide is large and the peeling resistance deteriorates. 0.0 to 3.0%.

Si is added as a deoxidizer and contributes to strengthening the matrix, but if it exceeds 2.0%, the toughness deteriorates, so it is made 2.0% or less. Mn, like Si, is used as a deoxidizing agent and contributes to the improvement of hardenability. However, if it exceeds 2.0%, the transformation temperature is lowered and the annealing hardness is less likely to decrease, and Mn remains after quenching. Since austenite increases and quenching hardness decreases, it is set to 2.0% or less.

[0009] Cr forms a solid solution in the matrix to improve the hardenability and, in particular, greatly contributes to the improvement of the rust resistance, and forms carbide to provide the wear resistance as a cold roll. It is an important ingredient. If it is less than 15%, it is not sufficient to obtain the desired rust resistance, and 30.0%
If it exceeds 1.0, C in the matrix will be insufficient, quenching hardness will decrease, wear resistance will decrease, net-like carbides will increase, and peeling resistance will also deteriorate, so 15.0-30.0.
%.

Mo and W, like Cr, are components that form carbides and form a solid solution in the matrix to contribute to the improvement of wear resistance, chatter mark resistance and rust resistance. , Is an expensive element that hinders the improvement of peeling resistance due to the graining effect of Cr carbide by the addition of Nb and is expensive.
The upper limit required to satisfy the required characteristics is Mo + 1/2
W is 2.0%.

[0011] V and Nb are extremely important components that form extremely hard MC carbides and increase the secondary hardening hardness during high temperature tempering, and thus greatly contribute to the improvement of wear resistance and chatter mark resistance. Further, coarsening of crystal grains at the time of high temperature quenching is prevented and Cr carbide is granulated, which contributes to improvement of peeling resistance. To obtain the above effects of V and Nb, V + 1/2
Nb needs to be 3.0% or more, and their addition amount is 8.
If it exceeds 0%, the amount of carbides becomes too large and the toughness, machinability and hot workability deteriorate. Therefore, the range is
It is 3.0 to 8.0% at V + 1/2 Nb.

Ni and Co do not form carbides and form a solid solution in the matrix to improve rust resistance. Further, since the transformation temperature is lowered and the solid solution is likely to occur in a shorter period of time, it has an effect of improving the induction hardenability. Ni: less than 0.2%, C
o: Less than 0.2%, this effect is almost negligible, and N
If i: 2.0% or more and Co: 8.0% or more, the annealing hardness is hard to decrease, and a large amount of retained austenite is generated during quenching, resulting in low hardness. Therefore, Ni is
0.2 to 2.0% and Co to 0.2 to 8.0%.

A material excellent in wear resistance under a rust generation environment, which is a feature of the present invention, that is, in order to suppress a wear amount which is increased by repeating rust generation-wear-creation of new interface-rust generation to be small, Within the range of components, and the balance of these components is the formula of rust wear, M = 1000 / {-7.63+
7.58 x C (%) + 0.45 x Cr (%) -1.60
× Mo (%) + 2.20 × W (%) + 1.34 × V
(%) − 0.50 × Nb (%)} 34 ≦ M ≦ 5
0, the alloy powder consisting of the balance Fe and unavoidable impurities was manufactured by the HIP method or the hot extrusion method, and the ratio of carbides having a particle size of 5 μm or less was 9% in total.
What is achieved by quenching and tempering to a hardness of 60 HRC or more at 5% or more, and Ni, C
It has been found that the induction hardenability is improved by adding an appropriate amount of o.

Next, the manufacturing process of the cold roll will be described. The above-mentioned invention components are high C, high Cr, high V (Nb)
When it is manufactured by the melting method, it produces huge eutectic carbides, which significantly deteriorates peeling resistance and induction hardenability, and rusts due to the deterioration of the roughness of the roll surface during use. And the cold workability and hot workability are deteriorated, which makes manufacturing difficult. Therefore, the alloy powder by water or gas atomization in which the giant eutectic carbide does not precipitate is manufactured by the HIP method and the hot extrusion method.
After processing this material into a predetermined shape, quenching or induction quenching-tempering is performed to obtain a hardness of 60 HRC or more. The tempering temperature is preferably a low tempering temperature, but if high temperature tempering is required as a measure against bending or the like, the treatment is performed twice or more.

[0015]

【Example】

(Example 1) As a test material by the powder method shown in Table 1, an alloy powder was produced by gas atomization, and the powder was used for a diameter of 150.
HI is filled in a mm steel capsule and degassed and then sealed.
After P (hot isostatic pressing) treatment, diameter 35mm
It was created by stretching. Further, the test material by the melting method was prepared by forging and rolling a φ35 rolled material from a running steel ingot or a 100 kg steel ingot in a high frequency induction furnace to a diameter of 35 mm, and used for each test.

(1) Rust wear (wearability under rust generation environment) evaluation test The test material was processed into a diameter of 30 mm to prepare a roll test piece,
After quenching-tempering treatment under the conditions shown in Table 1, after finishing processing, under the test conditions shown in Table 2, while tap water is dropped, it is brought into contact with the mating roll and driven to rotate to cause wear in a rusting environment. The amount was measured and evaluated. The test results are shown in Table 1. The amount of rust wear is a formula of rust wear, M = 1000 / {-7.
63 + 7.58 x C (%) + 0.45 x Cr (%)-
1.60 x Mo (%) + 2.20 x W (%) + 1.34
For xV (%)-0.50xNb (%)}, it can be seen that when the M value is 50 or less, it is stable at a low wear amount of 50 mg or less.

[0017]

[Table 1]

[0018]

[Table 2]

(2) Peeling Resistance Evaluation Test The test material was processed into φ30 mm to prepare a test piece for a roller pitching test, which was subjected to quenching-tempering treatment under the conditions shown in Table 1 and finishing processing, and then Table 3 The number of rotations until the occurrence of pitching (peeling that progresses due to fatigue cracks) caused by applying sliding friction with the load and the slip ratio under the test conditions shown in was measured. The results were arranged by a Weibull distribution map and evaluated by a breakage probability (L ₁₀ life) of 10%. The results are shown in Table 1.

[0020]

[Table 3]

The peeling resistance has a strong correlation with a carbide ratio of 5 μm or less and shows a life of 30E + 04 cycles or more at 95% or more. In particular, powder materials have the same value (M) according to the same rust wear equation. It can be seen that the peel resistance is 10 times or more that of the lumber. Further, in the powder material, M-1 and M- in which carbide grain size is adjusted with the same component
When 2 and S-1 and S-2 are compared, the carbide ratio of 5 μm or less shows a more stable life when 95% or more, and the carbide ratio of 5 μm or less decreases as the M value decreases. However, it tends to have a short life, and in particular M =
It becomes more remarkable when it is less than 34.

(3) Chatter mark resistance evaluation test Regarding the test piece evaluated for wear resistance under the rust occurrence environment of (1) above, the uneven wear state was measured using a roundness measuring instrument. Since the wear condition of the test piece is wavy like chatter marks, the test piece was evaluated by the maximum value-minimum value of the raceway surface. The results are shown in Table 1. It can be seen that the ingot material is greatly unevenly worn and has a large wavy shape as compared with the powder material. Roundness between powder materials is similar to peel resistance.
Influenced by the ratio of carbides, the invention steels having a value (M) of rust wear of 34 to 50 have a stable result of 20 μm or less. On the other hand, an effect can be expected.

(4) Induction hardenability evaluation test Under the above-mentioned quenching conditions of the test piece for wear resistance test in the rust generating environment, heat treatment when the heating time during quenching is shortened from the usual 20 minutes to 5 minutes The hardness measurement results are shown in Table 1. The hardness of the additive-free material of Ni or Co is 6 in both cases.
In contrast to less than 0 HRC, the Ni or Co additive material exhibits a high hardness of 60 HRC or more, and as the content increases, it approaches the hardness of normal heat treatment. That is, it has been confirmed that high hardness can be obtained by heating for a short time, and that high hardness can be obtained at a lower temperature in the case of the same heating time, so that it is excellent in induction hardenability. I understand.

(Example 2) In the composition range of the steel of the present invention,
2.2C-17.5Cr-0.4Mo-5.5V- (1
Ni) ... Rust wear equation, M = 42 from alloy powder by gas atomization, tension leveler roll (φ80 × length 2200 of SS steel pickling line)
mm) was manufactured, and an actual machine comparison test with a conventionally used roll was performed. The results are shown in Table 4. (1) Manufacturing process Nitrogen gas atomization-Canning-Vacuum degassing-HIP
-Forging-Processing-Induction hardening-Tempering-Finishing (2) Heat treatment conditions / hardness Induction hardening: 1170 ° C (1Ni material is 1130)
℃), tempering: 530 ℃ × 5 hours × 2 times, surface hardness:
63HRC

(3) Test Results The tension leveler roll of the invention material is 1/1 of the conventional steel.
The amount of wear was 0 or less, and there was almost no rusting. Roll life is SUJ2: 20,000t, SUS440C: 10
10,000t, Inventive material: 200,000t or more (remove due to damage to other parts)
In particular, the invented material did not generate chatter marks (uneven wear) on the roll surface and did not print on the material to be processed (SS steel plate), so that good product skin was obtained. As a result of testing the backup roll, almost the same effect was obtained.

[0026]

[Table 4]

[0027]

As described above, the cold roll according to the present invention has a ratio of carbides having a particle size of 5 μm or less of 95% or more of the total in the material produced by the HIP method or the hot extrusion method of the alloy powder. , Hardened to a hardness of 60 HRC or more, and tempered, to find an expression of rust wear and an effective range thereof as an index for suppressing the amount of wear increased by the interaction of rust and wear. , Further peel resistance,
The excellent anti-chatter mark property improves the surface texture of the plate and significantly reduces the defective rate, so that its industrial value is extremely large.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Mikiya Yamana, 3007 Nakajima, Nakajima, Himeji, Hyogo Prefecture Sanyo Special Steel Co., Ltd. (72) Inventor Manabe Yuu 3702-4 Iioka, Saijo City, Ehime Prefecture (56) Reference JP-A-9-291346 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C22C 38 / 00-38/60 F16C 13/00

Claims (2)

(57) [Claims] 1. By weight%, C: 2.0 to 3.0% Si: 2.0% or less Mn: 2.0% or less Cr: 15.0 to 30.0% Mo + 1 / 2W: 2.0 % Or less and V: 3.0 to 8.0% Nb: 3.0% or less of 1 type or 2 types of V + 1/2 Nb
Content of 3.0 to 8.0%, formula of rust wear, M = 100
0 / {-7.63 + 7.58 × C (%) + 0.45 × C
r (%)-1.60 x Mo (%) + 2.20 x W (%)
+ 1.34 × V (%) − 0.50 × Nb (%)} satisfying 34 ≦ M ≦ 50, the alloy powder consisting of the balance Fe and unavoidable impurities is manufactured by the HIP method or the hot extrusion method. The ratio of carbides having a particle size of 5 μm or less is 95% or more of the whole, and the material is hardened to a hardness of 60 HRC or more and tempered, and the wear resistance and the peeling resistance in a rust generating environment are evaluated. High toughness cold roll with excellent chatter mark. 2. By weight%, C: 2.0 to 3.0% Si: 2.0% or less Mn: 2.0% or less Cr: 15.0 to 30.0% Mo + 1/2 × W: 2 0.0% or less and V: 3.0 to 8.0% Nb: 3.0% or less of 1 type or 2 types of V + 1 / 2Nb
3.0 to 8.0%, Ni: 0.2 to 2.0%, Co: 0.2 to 8.0%, including one or two kinds, and the formula of rust wear, M = 1000 / {- 7.63 + 7.58 x C
(%) + 0.45 × Cr (%)-1.60 × Mo (%)
+2.20 x W (%) +1.34 x V (%) -0.50
XNb (%)} satisfies 34 ≦ M ≦ 50, and the alloy powder containing the balance Fe and unavoidable impurities is HI.
For materials produced by the P method or the hot extrusion method,
If the ratio of carbides with a particle size of 5 μm or less is 95% or more of the
High toughness with excellent wear resistance, peeling resistance and chatter mark resistance in a rusting environment characterized by being hardened and tempered to a hardness of 60 HRC or more and having good induction hardenability Cold roll.