JP2005144488A - Build-up welding material for continuous casting roll and roll using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a build-up welding material for a continuous casting roll which is excellent in thermal crack resistance with high proof stress, high ductility and low thermal expansibility at an elevated temperature, and also to provide the rolls using the welding material. <P>SOLUTION: The build-up welding material for the continuous casting roll is characterized by the chemical specification in mass%, which includes C:≤0.1 %, Cr:10-15 %, Mo:8-15 %, Co:≤15 %, W:≤5 %, Al:1-5 %, Ti:1-5%, and the remainder of Ni and inevitable impurities, besides, conforming to the equation: Cr %/33+Mo %/25+W %/31≤1. Furthermore, the build-up welding material for the continuous casting roll whose chemical specification additionally includes in mass% Si:≤0.5 %, Mn:≤0.5 %, S:≤0.005 %, Nb:≤3 %, Ta:≤6 %, and the continuous casting roll using the material is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a continuous casting roll overlay welding material and roll having high heat resistance, high ductility and low thermal expansion characteristics at high temperatures and excellent heat crack resistance.

  Conventionally, continuous casting rolls used at a high temperature of about 600 ° C. are in a harsh environment where rapid superheating and rapid cooling are repeated. They are damaged by thermal cracking and high temperature oxidation, and manufactured by maintaining and replacing them. Cost increase is an issue. To solve these problems, for example, as disclosed in Japanese Patent Application Laid-Open No. 2001-340991 (Patent Document 1), as a continuous casting roll having excellent heat cracking resistance, C: 0.07% or less, Si: 1 %: Mn: 1% or less, P: 0.03% or less, S: 0.03% or less, Ni: 3 to 5%, Cr: 15.5 to 17.5%, Cu: 3 to 5%, There has been proposed a continuous casting roll in which a built-up layer composed of Mo: 1.5% or less, Nb: 0.3 to 0.6%, the balance Fe and inevitable impurities is formed by welding.

Further, as disclosed in JP-A-2002-239697 (Patent Document 2), as a continuous casting roll excellent in Ni-based heat cracking resistance, C: 0.05% or less, Si: 0.05 %: Mn: 0.2% or less, Cr: 17-22%, Co: 10-14%, Mo: 4-8%, W: 0.8-1.5%, Al + Ti: 3-5.5 %, A Ni-alloy-based powder composed of the remaining Ni and unavoidable impurities has been proposed as a build-up roll for continuous casting in which a thickness of 2 mm or more is build-up welded by a powder plasma arc build-up welding method.
JP 2001-340991 A Japanese Patent Laid-Open No. 2002-239697

  As described above, a continuous casting roll in which a Ni-based austenitic alloy such as Fe-based martensite precipitation hardening stainless steel or Patent Document 2 is built up on the surface has been proposed. Fe-based stainless steel is inferior in high-temperature yield strength compared to Ni-based superalloys, and Ni-based superalloys have a relatively large thermal expansion coefficient. Therefore, there is a demand for a material having high-temperature proof stress and low thermal expansion characteristics, and more excellent heat-resistant crack resistance because the load applied to the continuous casting roll tends to increase as the casting technology increases in speed and temperature. Yes.

  In order to improve the thermal crack resistance of the continuous casting roll in such a use environment, it is important to have excellent high temperature proof stress and high temperature ductility and low thermal expansion characteristics. Therefore, as described above, Fe-based stainless steels generally have lower high-temperature proof stress than Ni-based superalloys, while Ni-based superalloys have a relatively high coefficient of thermal expansion, and these materials have sufficient heat cracking resistance. Not.

  Thus, although various Ni-base superalloys are commercially available, these are mainly developed as gas turbines and their peripheral materials, and are developed on the assumption that they are used in a temperature range close to 1000 ° C. Therefore, it is often not developed on the premise that the continuous casting roll is used at around 600 ° C. In general, these alloys are often used after being subjected to a solution treatment at a temperature close to 1100 ° C. in order to eliminate solidification bending and heterogeneous phase formation, and then subjected to an aging treatment at a temperature of about 700 ° C.

  However, clad rolls built for continuous casting also have problems such as interfacial cracking, and it is difficult to make a solution treatment, so it is important to have good characteristics even in a process in which the solution treatment is omitted. It becomes. Therefore, in consideration of these factors, the development is advanced and the use temperature is around 600 ° C., and even in the process where the solution treatment is omitted, the formation of the brittle phase is suppressed, and it has high yield strength, high ductility, and low thermal expansion characteristics. The present inventors have developed a Ni-base superalloy excellent in hot wear resistance and heat cracking resistance and led to the invention.

The gist of the invention is that
(1) By mass%, C: 0.1% or less, Cr: 10-15%, Mo: 8-15%, Co: 15% or less, W: 5% or less, Al: 1-5%, Ti: A welding material for overlaying continuous casting rolls, comprising 1 to 5%, consisting of the balance Ni and inevitable impurities, and satisfying Cr% / 33 + Mo% / 25 + W% / 31 ≦ 1.
(2) The welding material for continuous casting roll build-up according to the above (1) containing, by mass%, Si: 0.5% or less and Mn: 0.5% or less.

(3) The welding material for continuous casting roll build-up according to (1) or (2), wherein S is 0.005% or less in mass%.
(4) The welding material for overlaying continuous casting rolls according to the above (1) to (3), which contains, by mass%, Nb: 3% or less and Ta: 6% or less.

(5) Welding material for continuous casting roll build-up according to (1) to (4) that satisfies 20% ≦ γ ′ amount ≦ 35%, LM absolute value ≦ 0.015 mm, Nv, Nv ′ ≦ 2.30 .
However, strengthening phase mainly composed of γ ′: Ni ₃ Al LM absolute value: lattice constant mismatch of γ-γ ′ phase (Lattice Mismatch h)
Nv: average electron vacancy number of γ phase
Nv ′: Average number of electron vacancies of γ ′ phase (6) A continuous casting roll comprising the welding material for overlaying a continuous casting roll according to (1) to (5).

  According to the present invention, it is possible to obtain a continuous casting roll overlay welding material having high proof stress, high ductility, low thermal expansion characteristics at high temperatures and excellent heat cracking resistance, and a continuous casting roll using the same. It is effective.

Hereinafter, the reasons for limiting the component composition according to the invention will be described.
C: 0.1% or less C is an element for strengthening grain boundaries by forming carbides such as Ti, Cr, Mo, and W at grain boundaries. However, if it exceeds 0.1%, the Ti, Cr, Mo, W concentration in the grains decreases, and the proof stress and oxidation resistance are adversely affected, so the upper limit was made 0.1%.
Cr: 10-15%
Cr needs to be added in an amount of 10% or more in order to ensure oxidation resistance at high temperatures (around 600 ° C.). However, if it exceeds 15%, a brittle intermetallic compound is precipitated and ductility is lowered. Therefore, the range was made 10 to 15%.

Mo: 8-15%
Mo is an element having the effect of improving the high-temperature proof stress by dissolving in the γ phase and lowering the thermal expansion coefficient. In addition, there is an effect of increasing the corrosion resistance against hydrofluoric acid contained in the mold powder. However, if the amount is less than 8%, the effect is not sufficient, and if it exceeds 15%, a brittle intermetallic compound is precipitated and the ductility is lowered, so the range was made 8 to 15%.
Co: 15% or less Co is an element having an effect of improving ductility. However, if it exceeds 15%, the cost increases, so the upper limit was made 15%.

W: 5% or less W is an element having an effect of improving the high temperature proof stress by dissolving in the γ phase and an effect of lowering the thermal expansion coefficient. However, if over 5% is added, brittle intermetallic compounds are precipitated and ductility is lowered, so the upper limit was made 5%.
Al: 1 to 5%
Al has the effect of forming a γ ′ phase and improving high-temperature yield strength. However, if it is less than 1%, the effect is not sufficient, and if it exceeds 5%, the ductility decreases, so the range was made 1 to 5%.

Ti: 1 to 5%
Ti replaces Al in the γ ′ phase and strengthens the γ ′ phase. However, if it is less than 1%, the effect is not sufficient, and if it exceeds 5%, the ductility decreases, so the range was made 1 to 5%.
Cr% / 33 + Mo% / 25 + W% / 31 ≦ 1
When the value of Cr% / 33 + Mo% / 25 + W% / 31 exceeds 1, brittle intermetallic compounds are formed and ductility is lowered, so the upper limit was set to 1.

Si: 0.5% or less Si is an element for improving the hot-water flow when building up. However, if it exceeds 0.5%, inclusions such as oxides are precipitated, and mechanical properties such as impact value are deteriorated. Therefore, the upper limit was made 0.5%.
Mn: 0.5% or less Mn is an element for improving the flowability of hot water during overlaying, like Si. However, if it exceeds 0.5%, inclusions such as oxides are precipitated, and mechanical properties such as impact value are deteriorated. Therefore, the upper limit was made 0.5%.

S: 0.005% or less S is an element resulting from hot cracking during overlaying. Therefore, in order to suppress the high temperature crack at the time of overlaying, it is necessary to make it 0.005% or less.
Nb: 3% or less Nb is an element that improves the yield strength by solid solution in the γ ′ phase. However, if it exceeds 3%, the ductility decreases, so the upper limit was made 3%.
Ta: 6% or less Ta, like Nb, is an element that dissolves in the γ ′ phase and improves the yield strength. However, if it exceeds 6%, the ductility decreases, so the upper limit was made 6%.

20% ≦ γ ′ amount ≦ 35%, LM absolute value ≦ 0.015Å, Nv, Nv ′ ≦ 2.30
If the amount of γ ′ is less than 20%, the yield strength is low, and if it exceeds 35%, the ductility becomes low, and build-up cracking is likely to occur. Therefore, the range is set to 20 to 35%. Preferably, it is 23 to 30%. When the LM absolute value exceeds 0.015%, the γ 'phase aggregates and precipitates, and ductility decreases. Therefore, the upper limit was set to 0.015cm. Preferably it is 0.010 mm. When Nv and Nv ′ exceed 2.30, a brittle phase is precipitated and ductility is lowered. Therefore, the upper limit was set to 2.30. Preferably it is 2.28.

  The LM absolute value described above represents a lattice constant mismatch of the γ-γ ′ phase, and Nv and Nv ′ are the average electron vacancy numbers of γ and γ ′, respectively, and Nv = ΣCxNx and Nv ′ = ΣC′xNx. Here, Cx and C′x are the concentrations of the X element constituting the γ and γ ′ phases, respectively, and Nx is the number of intrinsic electron vacancies of the X element.

  The average number of electron vacancies in a Ni-based alloy is limited to γ and γ ′ phase alloys in which γ ′ is uniformly precipitated in the γ matrix. It is limited within a range not exceeding the solid solubility of γ ′. Even if it is only γ and γ ′ phases at the beginning when this limit is exceeded, a phase such as σ phase is precipitated in addition to γ and γ ′ phases during use for a long time, or γ ′ phase is η phase or It transforms into δ phase and deteriorates its properties. One of the quantities defining this limit is the average number of electron vacancies. If Nv and Nv ′ are 2.26 or less, the σ phase is not generated at all, and if it exceeds 2.41, the σ phase is always generated, and there are cases where the σ phase is generated or not in the middle. . Therefore, the average number of electron vacancies can be regarded as an amount that limits the boundary between γ or γ ′ and the σ phase.

Hereinafter, the present invention will be specifically described with reference to examples.
A 25 kg base material was melted in an induction melting furnace in an Ar atmosphere, hot water was discharged from a φ5 nozzle at 1600 ° C., and gas atomization was performed with Ar gas to obtain a powder having a component composition as shown in Table 1. This was classified to −250 / + 63 μm, and 6 layers of PTA were deposited on the low alloy substrate. A tensile test piece and a thermal expansion test piece were prepared from this build-up layer and heat-treated at 600 ° C. for 4 hours. The results are shown in Table 1. As the evaluation, 0.2% proof stress (MPa) and elongation (%) are subjected to a tensile test at 600 ° C., and the thermal expansion coefficient (× 10 ⁻⁶ ) is shown as thermal expansion characteristics at RT to 600 ° C.

As shown in Table 1, no. 1 to 10 are examples of the present invention. 11 to 15 are comparative examples. Comparative Example No. No. 11 has a low 0.2% yield strength because the amount of Mo as a component composition is low. Comparative Example No. Since No. 12 has a high Cr content and a low Mo content, it has a low 0.2% yield strength and a high thermal expansion coefficient. Comparative Example No. No. 13 has a high C content, a low Cr content, and a high Ti content, and therefore is inferior in elongation and oxidation resistance. Comparative Example No. No. 14 has a high C content, a high W content, and a high S content. Comparative Example No. No. 15 has a high Mo content, low Ti, and high Si, and therefore is inferior in 0.2% proof stress and elongation. In contrast to this, No. It turns out that it is excellent in any of 1-10.


Patent applicant Sanyo Special Steel Co., Ltd. and others 1
Attorney: Attorney Shiina

Claims (6)

% By mass
C: 0.1% or less,
Cr: 10 to 15%,
Mo: 8-15%,
Co: 15% or less,
W: 5% or less,
Al: 1 to 5%,
Ti: 1 to 5%,
A continuous casting roll overlay welding material characterized by comprising the balance Ni and unavoidable impurities and satisfying Cr% / 33 + Mo% / 25 + W% / 31 ≦ 1. The welding material for continuous casting roll build-up according to claim 1, comprising, by mass%, Si: 0.5% or less and Mn: 0.5% or less. The welding material for continuous casting roll build-up according to claim 1 or 2, wherein the mass% is S: 0.005% or less. The welding material for continuous casting roll build-up according to claim 1, comprising, by mass%, Nb: 3% or less and Ta: 6% or less. The continuous casting roll overlay welding material according to claim 1, satisfying 20 ≦ γ ′ amount ≦ 35%, LM absolute value ≦ 0.015%, Nv, Nv ′ ≦ 2.30.
However, strengthening phase mainly composed of γ ′: Ni ₃ Al LM absolute value: lattice constant mismatch of γ-γ ′ phase
Nv: average electron vacancy number of γ phase
Nv ′: average number of electron vacancies in the γ ′ phase A continuous casting roll comprising the welding material for overlaying a continuous casting roll according to claim 1.