JPH09227980A - Chromium base alloy for high temperature member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a Cr base alloy excellent in high temp. strength, oxidation resistance or the like and useful as a skid button in a steel heating furnace or the like. SOLUTION: This steel has a compsn. contg. 60 to <85% Cr, in which the coexistence of <=0.8% C and <=1.5% Si is allowable, and the balance substantial Ni and/or Co. If desired, the alloy contains one or >= two kinds of elements selected from the groups of <=10% W, <=10% Mo, <=10% Nb, <=10% Ti and <=10% V or/and one or two kinds of elements selected from <=10% Hf and <=10% Al.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chromium-based alloy for high-temperature members useful as a substitute material for hearth materials such as skid buttons and refractory materials for supporting a steel material to be heated in a steel material heating furnace.

[0002]

2. Description of the Related Art A skid button, which is a hearth metal product of a steel heating furnace, is required to have a strength capable of withstanding the repeated action of the weight of steel in a high temperature environment and an oxidation resistance against an oxidizing atmosphere.
As a material for such a high temperature portion, conventionally, as a material thereof, a high Ni-high Cr heat resistant alloy steel (for example, SCH12
Etc.), high Co alloy steel (50Co-20Ni-Fe), etc. have been used. 1200 ° C in the recent steel heating furnace
High-temperature operation exceeding 1300 ° C is generalized, and operation in a high temperature range of 1300 ° C or higher is also carried out. As an improved material to cope with such severe operating conditions,
JP-A-3-162545 discloses that the Cr content is 60%.
The above-mentioned Cr-Fe alloy is disclosed, and it is disclosed in JP-A-5-2718.
Japanese Patent Laid-Open No. 40 discloses a Cr-Ni alloy, a Cr-Co alloy, etc. containing 85% or more of Cr.

[0003]

The above Cr-Fe alloy (Cr 60% or more) has excellent high-temperature strength, oxidation resistance, etc., but has a problem that solidification shrinkage during casting is large and casting shrinkage easily occurs. There is. On the other hand, the casting yield of Cr-Ni (Co) alloy (Cr 85% or more) is relatively good, but since the melting point is extremely high at about 1770 ° C or more, the load on the refractory of the melting furnace and the casting mold is large, There are great difficulties in melting and casting operations. The present invention maintains the excellent high temperature strength and oxidation resistance of the Cr-based alloy while maintaining melting
The present invention provides a Cr-based alloy that alleviates and alleviates the above drawbacks associated with casting.

[0004]

Cr for a high temperature member of the present invention
The base alloy contains Cr: 60% or more and less than 85%,
Mixing of C: 0.8% or less and Si: 5% or less is allowed, and the balance substantially consists of Ni or / and Co.
If desired, the Cr-based alloy of the present invention may have W: 10% or less,
Mo: 10% or less, Nb: 10% or less, Ti: 10% or less, V: 10% or less, or one or more elements selected from the group, and / or Hf: 10% or less, Al: 1
A composition containing one or two elements selected from the group of 0% or less is provided.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The Cr-based alloy of the present invention has a high Cr-containing composition, so that it has excellent mechanical strength and oxidation resistance in a high temperature oxidizing atmosphere, and also has Ni or Co as a balance component. With this structure, the melting point is as low as 1700 ° C. or less, the difficulty of melting and casting operations is reduced, and the occurrence of shrinkage cavities due to solidification shrinkage during casting is suppressed and prevented.

The reasons for limiting the components of the Cr-based alloy of the present invention are as follows. All percentages indicating elemental contents are weight percentages. Cr: 60% or more but less than 85% The lower limit of the Cr content is 60% because the oxidation resistance to withstand a high temperature oxidative atmosphere exceeding 1300 ° C such as in a steel heating furnace and the repeated high load of heated steel materials. This is to ensure high temperature strength that can resist the action. Although its high temperature strength and oxidation resistance are increased by increasing the amount of Cr, its alloy has a high melting point, which increases the load on the refractory and the casting mold in the melting furnace, making melting and casting operations difficult. Therefore, the Cr content is 85%
It is necessary to limit it to less than.

Ni, Co: Balance component By using Ni and Co as a balance component, solidification shrinkage in the casting process and the occurrence of casting defects such as shrinkage cavities are alleviated and alleviated, and the casting yield can be increased. Become.
The selection of Ni and Co is arbitrary, and both elements may be contained in an arbitrary ratio.

C: 0.8% or less, Si: 5% or less C and Si are not essential elements, and if these elements are mixed in a large amount, they cause deterioration in high temperature strength, oxidation resistance and the like. However, the mixing of a small amount helps facilitate the melting and casting operations of the alloy while maintaining the required high-temperature strength and oxidation resistance. Therefore, C is within the range of 0.8% or less,
Si is allowed to be mixed within the range of 5% or less.

The Cr-based alloy of the present invention may optionally contain W:
10% or less, Mo: 10% or less, Nb: 10% or less, T
i: one or more elements selected from the group of 10% or less and V: 10% or less, and / or one or two elements selected from the group of Al: 10% or less and Hf: 10% or less
A composition containing the elements of the seed is provided. W, Mo, Nb,
Each element of Ti and V enhances high temperature compression creep strength, and A
Each of the elements l and Hf has an effect of enhancing high temperature oxidation resistance. The content of each element of W, Mo, Nb, Ti, and V is limited to 10% or less.
This is because the oxidation resistance of the alloy is deteriorated, and the upper limits of the respective contents of Al and Hf are limited to 10% because if the contents are exceeded, the toughness of the alloy is impaired. Preferably, W is 1 to 5%, Mo is 1 to 8%, Nb is 1 to 5%, and Ti is 1
~ 5%, V is 0.5-4%, Hf is 0.1-2
%, Al is 0.5 to 5%.

[0010]

[Examples] Each match money shown in Table 1 was melted and cast, and the results shown in the right column of the table were obtained. Specimen Nos. 1 to 9 are invention examples, and Nos. 11 to 16 are comparative examples. Of the comparative examples,
No. 11 is an alloy of substantially Cr single composition, No. 12 is C
An alloy in which the amount of r is outside the upper limit of the present invention and Fe is a balance component, No. 13 is an alloy in which the amount of Cr satisfies the upper limit of the present invention, but the balance component is Fe, No. .14 to No. 16 are alloys having Ni or / and Co as a balance component, but the amount of Cr deviates from the upper limit of the present invention.

[Melting] By a high frequency melting furnace. [Casting] Casting method: Immersion casting Mold material type: Sand mold Casting size: 150 × 200 × 60 (mm) (rectangular solid) Casting temperature: Melting point + 100 ℃

[Castability] The castability of each cast product is evaluated by the size of shrinkage cavities and the presence or absence of casting cracks. The symbols in the "shrink" and "crack" columns of "castability" in the table are as follows. "Shrink" column ○: Shrinkage cavities are minimal (Shrinkage depth <40 mm, Yield> 50
%) △: Shrinkage cavity slightly large (Shrinkage depth 40 to 120 mm, yield
15 to 50%) ×: Shrinkage cavity occurrence is remarkable (shrinkage cavity depth> 120 mm, yield <15
%) “Crack” column ○… No color check cracks △… No visual cracks, color check cracks ×… Visual cracks

[Compressive Strength] Test piece (φ30 × 50 h, mm) The stress (kg / mm ² ) which produces 1% strain at 1400 ° C. and 100 Hr was measured. [Oxidation resistance] Test piece (φ8 × 50 l, mm) After holding for 100 hr in a heating furnace (atmosphere atmosphere) at 1250 ° C., increase in oxidation (mg / cm ² ) of the test piece was measured.

As shown in Table 1, invention examples (No. 1 to 9)
Has a melting point of 1700 ° C. or less, good castability, and excellent high-temperature strength and oxidation resistance. Comparative Example N
o.11 (Cr single composition) and No. 12 (Cr amount: excess, balance component: Fe) have high melting points, poor castability, and poor compressive strength. No.13 (Balance component: Fe)
Poor castability and low compressive strength. No.14-16 (Cr content:
Excess) has Ni or Co as a balance component like the invention example, but the compressive strength is not sufficient and the melting point is higher than 1700 ° C. The load on the mold is large.

[0015]

[Table 1]

[0016]

INDUSTRIAL APPLICABILITY The Cr-based alloy of the present invention has high strength and oxidation resistance in a high temperature oxidizing atmosphere, and is suitably used as a metal material in a furnace for heating a steel material. Further, the melting / casting operability is good, the melting energy is reduced, and the load on the melting / casting apparatus members is reduced, so that the service life of these apparatus members can be improved.

Claims (2)

[Claims] 1. An alloy containing Cr: 60% or more and less than 85%, C: 0.8% or less, and Si: 5% or less, with the balance being substantially Ni or / and Co. Cr-based alloy for high temperature members. 2. A Cr content of 60% or more and less than 85%, W: 10% or less, Mo: 10% or less, Nb:
One or more elements selected from the group of 10% or less, Ti: 10% or less, V: 10% or less, or / and one selected from the group of Hf: 10% or less and Al: 10% or less. Or containing two kinds of elements, C: 0.8% or less,
And Si: A Cr-based alloy for high temperature resistant members, in which 5% or less is allowed to be mixed and the balance is substantially Ni and / or Co.