JP2001105176A - Material for plasma welding excellent in wear resistance, corrosion resistance, seizure resistance and compound tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cladding by welding tool for plastic working of a roll, etc., excellent in wear resistance in hot/cold rolling, crack resistance and corrosion resistance. SOLUTION: A plasma welding material and a tool material welded with the melding material are constituted of a composition consisting of Fe, C, Cr, V, Mo, W, Nb, Ta, Zr, Al and lanthanides elements. By specifying an area rate of a MC carbide and a crystallization grain size of the MC carbide, better wear resistance/crack resistance/corrosion resistance effects can be exhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma welding material excellent in abrasion resistance, corrosion resistance and seizure resistance, and a composite tool such as a roll and a roller used in iron making.

[0002]

2. Description of the Related Art Conventionally, for high wear-resistant rolls and rollers used in the field of iron making, hot and cold tool steels such as SKD6 and 12, hardened high-speed steels or welded high-speed steels, stainless steels, heat-resistant alloy steels Etc. are often manufactured. In this case, the wear resistance of the SKD steel increases with an increase in the amount of carbon and Cr, but the hardness is limited because the carbide composition is Cr carbide, and it is difficult to significantly improve the wear resistance. . On the other hand, high-speed steel contains high-hardness carbides such as V, Mo, W, etc., so that the wear resistance is greatly improved. SKD, high-speed steel, etc. contain a large amount of carbides, and the base structure is mainly martensite, so that seizure resistance is relatively good, but corrosive atmospheres such as cooling water, steam and cleaning water. Corrosion wear associated with
Further, corrosion resistance such as oxidative wear caused by temperature rise due to heat transfer from the sheet passing material is not considered, and the original wear resistance cannot be sufficiently enjoyed. When focusing on corrosion resistance, there are conventional stainless steels and heat-resistant alloy steels.However, stainless steels and heat-resistant alloy steels must contain a large amount of carbides in the alloy design to make the base austenitic or martensite. However, there is a problem such as seizure caused by mechanical wear resistance and Cr content.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and improves corrosion resistance.
It is an object of the present invention to provide a plasma welding material and a composite tool having excellent wear resistance and seizure resistance.

[0004]

In order to achieve the above-mentioned object, the present invention employs the following means. That is, the invention according to claim 1 is characterized in that, by weight, 1.0 to 4.5% of C,
0.5% or less of Si, 1.0% or less of Mn, 8.0 to 2
0.0% Cr, 1.0-5.0% Ni, 5.0-2
A material for plasma welding, comprising 5.0% of V and the balance being Fe and unavoidable impurities. The invention according to claim 2 is that, by weight ratio, 1.0 to 4.5% of C, 0.5% or less of Si, 1.0% or less of Mn, and 8.0 to 20.0% of C.
r, 1.0 to 5.0% of Ni, 5.0 to 25.0% of V, Mo and W, one or two of
≦ 2Mo + W ≦ 20%, the balance being Fe and unavoidable impurities, a material for plasma welding. The invention according to claim 3 is that, by weight ratio, 1.0 to 4.5% of C, 0.5%.
% Si, 1.0% or less Mn, 8.0 to 20.0%
% Cr, 1.0-5.0% Ni, 5.0-25.0
%, One or two of V, Mo and W are 1.0 ≦ 2Mo + W ≦ 20%, one or two or more of Nb, Ta and Zr are 0.1 to 10.0%, and the balance is Fe. And a material for plasma welding, comprising an unavoidable impurity. According to the invention of claim 4, the weight ratio is 0.1.
The material for plasma welding according to any one of claims 1 to 3, wherein the material contains 01 to 1.0% Ti. According to a fifth aspect of the present invention, there is provided the plasma according to any one of the first to fourth aspects, wherein at least 0.3% by weight of Al and one or more lanthanoid elements are contained. Materials for welding. The invention according to claim 6 is characterized in that M
The material for plasma welding according to any one of claims 1 to 5, wherein the C carbide has a circle equivalent particle size of 1 to 150 µm. The invention according to claim 7 is characterized in that the area ratio of MC carbide in the weld metal is 10 to 70%.
7. The material for plasma welding according to any one of 6. The invention of claim 8 is a composite tool in which at least 0.5 mm or more of the surface layer is overlaid using the welding material according to any one of claims 1 to 7.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail to provide an understanding of the present invention. As a result of elucidating the cause of the deterioration of corrosion resistance from the organization, the inventors found that under a corrosive environment, base corrosion,
It has been found that the corrosion resistance decreases due to preferential oxidation of the matrix by heat transfer from the sheet passing material, and that the wear resistance also decreases due to the lack of MC carbide in the structure. The inventors have been studying to solve such a problem, and have set the base to be Cr-rich,
Alternatively, it was clarified that the corrosion resistance can be significantly improved by increasing the area ratio of the crystallized carbide, and that the wear resistance and seizure resistance can be further improved by finely crystallizing a large amount of MC carbide.

[0006] In order to obtain a structure of an iron-based alloy in which the matrix in the structure is Cr-rich or contains MC carbide, Cr carbide and a complex carbide of Mo, W, Cr, an iron-based alloy containing these elements and carbon is generally used. Can be obtained by dissolving and cooling to crystallize carbides, pulverize or crystallize the molten metal into powder, and weld the resulting raw material to build up by welding or spraying. In this case, it suffices to perform the work on the minimum necessary portion.

The reasons for limiting each alloy element constituting the present invention will be described below. The reason why the C content is limited to 1.0 to 4.5% by weight is that if the C content is less than the lower limit, hard carbide is less crystallized, so that abrasion resistance and seizure resistance cannot be secured. on the other hand,
If the upper limit value is exceeded, Cr carbides are likely to be formed at the crystal grain boundaries, thereby deteriorating the weldability, and the Cr content in the matrix is reduced, so that sufficient corrosion resistance cannot be expected.
The reason for limiting the Cr content to 8.0 to 20.0% by weight is that the higher the Cr content, the more excellent the corrosion resistance is. However, if the Cr content is less than the lower limit, the corrosion resistance is not sufficiently exhibited. This is because it is not preferable because the hardness of the metal is reduced. Although the addition of Ni improves the toughness of the weld metal, the content is limited to 1.0 to 4.0% by weight. If the content is less than the lower limit, the toughness of the weld metal is inferior, and cracks occur during welding. Easier to do. On the other hand, if the value exceeds the upper limit, the amount of retained austenite in the weld metal increases, and the hardness decreases significantly. V is selected in balance with C in order to crystallize VC of extremely hard MC type carbide among carbides. In particular, in the case of the material of the present invention, this V
It is important to improve the wear resistance by utilizing C and to control the structure by crystallizing as a primary crystal carbide when the weld metal is solidified. V content from 5.0 to 25.0
When the C content is in the above range, when the V content is less than the lower limit, the hard MC carbide does not crystallize, but forms a solid solution in the matrix. This is because if the V content exceeds the upper limit, V is dissolved in the final solidified portion to significantly impair the corrosion resistance of the molten metal. Mo and W form double carbides such as M ₆ C carbide together with MC, M ₂ C carbide or Cr contained therein, and contribute to wear resistance and seizure resistance, and partially form a solid solution in the matrix. And contributes to suppressing a decrease in hardness at high temperatures and improving wear resistance. Mo, W amount is 1.0
If it is limited to ≦ 2Mo + W ≦ 20.0% by weight, if it is less than the lower limit value, it is not possible to sufficiently suppress the decrease in hardness at a high temperature or sufficiently exhibit the decrease in wear resistance. On the other hand, if it is at least the upper limit, the toughness and crack resistance will be reduced due to the excessive increase of net-like double carbides. When Nb, Ta, and Zr are contained, they form MC carbides and contribute to wear resistance and seizure resistance. Nb,
The reason that Ta and Zr are limited to 0.1 to 10.0% by weight is as follows.
If the amount is less than the lower limit, MC carbides are not generated, and if the amount exceeds the upper limit, the particle size of the MC carbides increases, which is not preferable. Si, Mn, Al and lanthanoid elements are usually used as a deoxidizing agent.
If the content exceeds 5% by weight and Mn exceeds 1.0% by weight, the toughness of the weld metal is impaired. Similarly, when the content of Al and the lanthanoid element exceeds 0.3% by weight, the weldability is remarkably deteriorated. The inclusion of a small amount of Ti promotes the refinement of primary MC carbides and crystal grains. The reason why the Ti content is defined as 0.01 to 1.0% by weight is that it is not preferable because the fine effect is not exhibited below the lower limit and the particle size of the MC carbide becomes larger when the upper limit is exceeded. is there.

[0008] The MC carbide in the weld metal has a high hardness and thus determines the wear resistance. However, the shape thereof is variously crystallized from granular to angular or star. Since MC carbide is hard, if the size is too large, cracks are easily generated in the carbide and cause chipping. The shape is most desirably granular. When the size of each crystallized MC carbide is expressed by a circle-equivalent particle diameter represented by an average of the maximum length and the minimum length, the circle-equivalent particle diameter is preferably in the range of 1 to 150 μm. If it exceeds 150 μm, chipping tends to occur as described above. The lower limit was set to 1 μm, because the lower limit of 1 μm is that wear resistance can be sufficiently exhibited, and it is difficult to obtain a carbide particle size of less than 1 μm after welding.

The crystallization amount of MC carbide in the weld metal is important for securing wear resistance, seizure resistance, toughness, and the like.
It is desirable to crystallize. If it is less than the lower limit, sufficient wear resistance and seizure resistance cannot be secured. On the other hand, if the upper limit is exceeded, the toughness will deteriorate.

[0010] The composite tool which has been subjected to welding overlaying using the above-mentioned welding material can be used for machining rolls regardless of hot or cold.
Used as tools in all fields including wrapper rolls and rollers. When applied to iron-made members, it can be used as a tool material for plate rolling, seamless rolling, wire rod rolling, hot pressing, and also as a forging tool.

[0011] In this case, the thickness of the weld metal is preferably as thick as it can withstand long-term use. However, for example, in the case of plasma welding overlay, the thickness of one overlay is 1 to 3 mm, and is 0 after grinding. It becomes about 0.5 to 2 mm. Thick overlay is possible by repeating welding overlay. The build-up thickness may be determined in consideration of the cost of repeated welding and the cost reduction due to reuse. However, if the overlay thickness is 0.5 mm or less after finishing, the merit cannot be sufficiently enjoyed, so the lower limit of the overlay thickness is set to 0.5 mm.

When the composite tool of the present invention is applied to a roll or the like, at least the surface layer of the portion corresponding to the outer layer is a single-layer or multiple-layer sleep as a composite tool according to the claims, and is joined to the inner layer. Can be joined by methods such as welding, sintering, and melting, as well as shrink-fitting, fitting, and used as a composite roll.

[0013]

Embodiments of the present invention will be described below. A welding material having a composition as shown in the following Table 1 was subjected to plasma overlay welding on a base material made of a steel material for a machine structure, and (1) wear resistance,
(2) Crack resistance and (3) corrosion resistance were evaluated. The wear test was evaluated by a disk-to-disk wear tester as schematically shown in FIG. 1, and the corrosion test was evaluated by a salt spray test as specified in JISZ2371. In FIG. 1, reference numeral a denotes a heating piece (in charge of a work material), b denotes a test piece (in charge of a tool such as a roll material), c denotes a high-frequency heating device, d denotes a water-cooled nozzle, and e denotes a radiation thermometer. (Abrasion / Crack Test Conditions) (1) Specimen size: outer diameter 80 mm, thickness 10 mm, surface layer was welded by plasma overlay welding, and finished so that the overlay portion finally became 3 mm. (2) Heating piece size: outer diameter 160 mm, thickness 15 mm,
Material S45C (3) Wear test conditions: heated piece temperature 900 ° C, slip rate 1
The wear amount of 1% under a load of 70 kgf was compared by measuring the change in weight of the test piece after 10,000 rotations. The slip rate was defined as follows. ((Heating piece speed-test piece speed) / test speed change)
× 100 (%) (4) Crack test conditions: The temperature of the heated piece was 900 ° C., the sample was cooled with water after heating, and the crack depth was measured when the test was repeated 2,000 times.

[0014]

[Table 1]

(Corrosion Test Conditions) (1) Specimen size: 50 mm in length, 20 mm in width, 10 mm in thickness, and 2 mm in surface of the test piece, after plasma overlay welding, finished to 2 mm in overlay layer. (2) Test conditions: 5% saline was sprayed on the test piece at 35 ° C. for 1 hour, and the weight loss after the test was compared. Table 2 shows the results of the abrasion, crack and corrosion tests, the MC carbide area ratio, and the circle-equivalent particle size based on the structure observation. In addition,
The wear, crack, and corrosion tests were also performed simultaneously on a cast high-speed steel as a comparative material, and compared with the high-speed steel. That is, abrasion ratio = abrasion weight of test material / abrasion weight of high-speed material, crack length ratio = crack length of test specimen /
Crack length and corrosion ratio of high-speed steel = corrosion loss of test material /
Expressed by the corrosion loss of high-speed steel.

[0016]

[Table 2]

The material of the present invention is compared with cast high-speed steel.
Abrasion resistance is about 20-50%, crack resistance is 10-35
% And the corrosion resistance is improved by 20 to 80%.

[0018]

As described in detail above, the present invention is excellent in wear resistance, crack resistance, and corrosion resistance, so that it can be applied to hot working tools such as rolls and rollers and cold working tools. As a result, it greatly contributes to key industries.

[Brief description of the drawings]

FIG. 1 is a diagram showing a design outline of a disk-to-disk wear tester.

[Explanation of symbols]

 a Heating piece (working material side) b Test piece (tool such as roll material) c High frequency heating device d Water cooling nozzle e Radiation thermometer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitaro Sasaki 2-22-19 Imamachi, Kokurakita-ku, Kitakyushu-shi (72) Inventor Hide Uchida 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Tsuyoshi Inoue 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Headquarters (72) Inventor Yasuhiro Wada 20-1 Shintomi, Futtsu-shi, Chiba Technology Development Headquarters Nippon Steel Corporation F term (reference) 4E001 AA03 BB11 CA07 DA07 EA05

Claims (8)

[Claims] (1) 1.0 to 4.5% by weight of C, 0.
5% or less of Si, 1.0% or less of Mn, 8.0 to 20.
0% Cr, 1.0-5.0% Ni, 5.0-25.
A plasma welding material comprising 0% V and the balance being Fe and unavoidable impurities. 2. 1.0 to 4.5% of C, 0.1% by weight.
5% or less of Si, 1.0% or less of Mn, 8.0 to 20.
0% Cr, 1.0-5.0% Ni, 5.0-25.
A material for plasma welding, characterized in that one or two of V, Mo and W of 0% are 1.0 ≦ 2Mo + W ≦ 20% and the balance is Fe and unavoidable impurities. 3. A 1.0 to 4.5% C, 0.1% by weight ratio.
5% or less of Si, 1.0% or less of Mn, 8.0 to 20.
0% Cr, 1.0-5.0% Ni, 5.0-25.
One or two of V, Mo and W of 0% are 1.0 ≦ 2Mo + W ≦ 20%, one or two or more of Nb, Ta and Zr are 0.1 to 10.0%, and the remainder is A material for plasma welding, comprising Fe and inevitable impurities. 4. The material for plasma welding according to claim 1, wherein the material contains 0.01 to 1.0% by weight of Ti. 5. The plasma welding apparatus according to claim 1, wherein the composition contains one or more of Al and lanthanoid elements in a weight ratio of 0.3% or less. material. 6. The plasma welding material according to claim 1, wherein the MC carbide in the weld metal has a circle equivalent particle size of 1 to 150 μm. 7. The area ratio of MC carbide in the weld metal is 10
The material for plasma welding according to any one of claims 1 to 6, wherein the content is up to 70%. 8. A composite tool obtained by overlaying at least 0.5 mm or more of the surface layer using the welding material according to claim 1.