JP4115610B2 - Electromagnetic stainless steel with excellent low temperature toughness - Google Patents

Description

【００１６】
その測定条件は次の通りである。
（１）シャルピー衝撃試験（ＪＩＳ Ｚ ２２４２）
ＪＩＳ４号Ｖノッチ サブサイズ（５×１０×５５Ｌ）試験片で−１００〜１００℃で試験を行い、エネルギー遷移温度（Ｔ_rE）を測定。
（２）磁気特性
リング状試験片を作製し、８５０℃×４ｈ保持の真空磁気焼鈍を施した後に直流Ｂ−Ｈトレーサを用いて磁束密度Ｂ₂₅および保磁力Ｈ_C を測定した。
【００１７】
（３）固有抵抗
ケンビンダブルブリッジを用いた直流４端子法で測定した。
（４）耐食性
φ１２×２１Ｌの試験片をエメリー研磨紙で８００番まで研磨した後、サイクル湿潤試験（２０℃、９０％ＲＨ、１．５ｈ保持→７０℃、９０％ＲＨ、４．５ｈ保持 サイクル数；２０回）を行い下記基準で比較した。
○：発錆の面積率が５％未満で耐食性が良好であるもの
×：発錆の面積率が５％以上で耐食性が不良好であるもの
その結果を表２に示す。
【００１８】
【表２】

【００１９】
【発明の効果】
以上述べたように、本発明による電磁ステンレス鋼は、特に優れた低温靱性を有するものであり、しかも磁気特性や電気抵抗特性の改善されたものであり、また有効な耐食性を有するものであって、冷間鍛造用材料として腐食環境向けの電磁材料として用いられるものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic stainless steel excellent in low temperature toughness used in electromagnetic valves and various sensors used in cold districts and cooling atmospheres.
[0002]
[Prior art]
Conventionally, magnetic core materials such as solenoid valves and magnetic sensors have a high specific resistance for improving magnetic response, excellent magnetic properties, and corrosion resistance. Therefore, for example, when it is used at 10 ° C. or lower, particularly −20 ° C. or lower, an electromagnetic material having excellent toughness even at a low temperature is demanded. Further, when forming a part by cold forging the material, it is required that the toughness at normal temperature is good. For example, Japanese Patent Publication No. 63-53255 is known as a technique for improving its toughness while maintaining its effective corrosion resistance. This patent includes C + N ≦ 0.02%, Si + Al ≧ 1.4%, 2Si + Al ≦ 6%, Al ≦ 3.5%, Ti: 0.10 to 0.60%, Cr: 5 to 15%, Mn ≦ 0.40%, Pb: 0.05 to 0.25%, P ≦ 0.040%, S ≦ 0.030% The balance is essentially made of Fe. It is.
[0003]
Japanese Examined Patent Publication No. 6-10324 is known as a soft magnetic rod tube material having improved corrosion resistance and machinability without impairing electromagnetic characteristics. In this patent, C + N ≦ 0.02%, Si ≧ 3%, Mn ≦ 0.50%, Cr: 12-18%, Al: 0.8-less than 1.5%, Mo: 0.05-0. 5%, Pb ≦ 0.040%, S ≦ 0.030%, remaining Fe and inevitable impurities, a free-cutting corrosion-resistant soft magnetic bar tube steel.
[0004]
[Problems to be solved by the invention]
However, in the above-mentioned Japanese Patent Publication No. 63-53255, toughness can be achieved without degrading electromagnetic characteristics by adding an appropriate amount of Cr, Si, Al, Ti, and Pb and suppressing C and N to extremely low values. Although improving the corrosion resistance and machinability at the same time, it is still not sufficient to improve the low temperature toughness, and in Japanese Patent Publication No. 6-10324 Therefore, C and N are suppressed as much as possible, Al is added at 0.8% or more to improve corrosion resistance, and in order to further improve corrosion resistance, Mo is added and Pb is added to improve machinability However, this also has a problem that it is not yet sufficient to improve the low temperature toughness.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the inventors have intensively developed, and as a result, the amount of C, Si, P, S, Cr, O, N, which adversely affects the low temperature toughness, and the grain size are regulated to improve the low temperature toughness. An object of the present invention is to provide an electromagnetic stainless steel whose low temperature toughness is improved by adding Al effective to the steel. The gist of the invention is that
(1) By mass, C: 0.015% or less, Si: 0.18 to 2.5%, Mn: 0.5% or less, P: 0.03% or less, S: 0.06% or less, Ni : 0.1 to 0.34%, Cr: 4 to 15%, Al: 0.5 to 4%, O: 0.01% or less, N: 0.015% or less, and the balance is Fe An electromagnetic stainless steel excellent in low temperature toughness characterized by having a grain size number 3 or more in steel.
[0006]
(2) the steel described in (1), further, Ti, electromagnetic stainless steel with excellent low temperature toughness characterized in that the addition below 1% of one or two or more of Z r.
(3) An electromagnetic stainless steel excellent in low-temperature toughness characterized by further adding 1% or less of one or two of Mo and Cu to the steel described in (1 ) .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the reason for limiting the component composition according to the present invention will be described.
C: 0.015% or less C is inevitably introduced in the production of stainless steel, but this C deteriorates magnetic properties, deteriorates toughness, and deteriorates cold forgeability. Therefore, its content must be adjusted with 0.015% as the upper limit.
[0008]
Si: 0.18 to 2.5%
Si is an effective element for increasing the specific resistance, and increases the specific resistance as the Si% in the stainless steel increases. On the other hand, this Si is an effective element for improving the magnetic properties. However, addition of Si exceeding 2.5% leads to deterioration of cold forgeability and low temperature toughness, so the upper limit needs to be 2.5%.
[0009]
Mn: 0.5% or less Mn, like C, is an element that is inevitably introduced in the manufacturing process of stainless steel, but its large amount impairs the cold forgeability of stainless steel. Therefore, the upper limit was made 0.5%.
P: 0.03% or less, S: 0.06% or less, N: 0.015% or less P, S, and N deteriorate cold forgeability, and S and N both adversely affect the magnetic properties. In addition to being an element that exerts an influence on the low temperature toughness, they were made 0.03% or less, 0.06% or less, and 0.015% or less, respectively. In addition, since the low temperature toughness is ensured mainly by the crystal grain size as described later, when machinability is required, S may be set higher than 0.03% and 0.06% or less.
[0010]
Ni: 0.1 to 0.34%
Ni is an element that effectively improves the corrosion resistance of stainless steel and improves low-temperature toughness. However, if the content is less than 0.1%, the effect cannot be achieved. If the content exceeds 0.34%, the effect is saturated and the magnetic properties are deteriorated, so the content is 0.1 to 0.34%. did. Cr: 4-15%
Cr is an element effective for corrosion resistance, and is also effective for increasing specific resistance. However, addition of a large amount exceeding 15% significantly deteriorates magnetic properties and hinders low-temperature toughness. On the other hand, if it is less than 4%, it is not effective from the viewpoint of corrosion resistance.
[0011]
Al: 0.5-4%
Al is an extremely effective element for improving low temperature toughness and improving corrosion resistance. However, if it is less than 0.5%, it is not effective from the viewpoint of low-temperature toughness, and addition exceeding 4% saturates the effect, so its content was made 0.5 to 40%.
O: 0.01% or less O is an element that forms oxide inclusions and hinders low-temperature toughness and significantly deteriorates the cold forgeability of stainless steel. It was.
[0012]
Ti, 1 or two or more than 1% of Ti Z r, Z r is the additional inclusion as a selection element, thereby improving the cold forgeability improvement and stainless steel low temperature toughness. Particularly when adding S more than 0.03% to 0.06% or less for improving machinability, good low temperature toughness can be maintained by adding Ti and Zr. However, the addition of a large amount of these elements deteriorates the magnetic properties and impairs the cold forgeability.
1% or less of one or two of Mo and Cu 1% or less Mo and Cu can each effectively improve the corrosion resistance of stainless steel, so 1% was made the upper limit.
[ 0013 ]
The grain size number 3 or more is the grain size number 3 or more, which is the greatest feature of the present invention. When the grain size is small (the grain size number is large), the number of crystal grains and grain boundaries per unit volume Increases, disperses stress and improves low temperature toughness. On the other hand, when the crystal grains become large (the crystal grain size number becomes small), the number of crystal grains and crystal grain boundaries per unit volume decreases, stress concentrates, and low temperature toughness decreases. Therefore, the lower limit of the crystal grain size number is set to 3.
[ 0014 ]
【Example】
Table 1 shows the chemical components of the steel of the present invention and the comparative steel. The materials of these compositions were annealed after melting 50 kg steel ingots in a vacuum induction furnace and forging them to a diameter of 40 mm. Furthermore, each test piece was produced from an annealed 40 mm diameter round bar and used for each measurement.
For low temperature toughness, transition temperature was measured by Charpy impact test. The magnetic properties were measured with a BH tracer, the specific resistance was evaluated by a direct current four-terminal method, and the corrosion resistance was evaluated by a cycle wet test.
[ 0015 ]
[Table 1]

[ 0016 ]
The measurement conditions are as follows.
(1) Charpy impact test (JIS Z 2242)
JIS No. 4 V-notch Subsize (5 × 10 × 55L) test piece is tested at −100 to 100 ° C., and energy transition temperature (T _rE ) is measured.
(2) Magnetic characteristics A ring-shaped test piece was prepared and subjected to vacuum magnetic annealing at 850 ° C. × 4 h, and then the magnetic flux density B ₂₅ and the coercive force H _C were measured using a DC B—H tracer.
[ 0017 ]
(3) Specific resistance It measured with the direct current | flow 4 terminal method using a Kenbin double bridge.
(4) Corrosion resistance After polishing a φ12 × 21L test piece with emery abrasive paper to No. 800, cycle wet test (20 ° C., 90% RH, 1.5 h hold → 70 ° C., 90% RH, 4.5 h hold cycle) Number; 20 times) and compared according to the following criteria.
○: Area ratio of rusting is less than 5% and corrosion resistance is good ×: Area ratio of rusting is 5% or more and corrosion resistance is unsatisfactory Table 2 shows the results.
[ 0018 ]
[Table 2]

[ 0019 ]
【The invention's effect】
As described above, the electromagnetic stainless steel according to the present invention has particularly excellent low-temperature toughness, has improved magnetic characteristics and electrical resistance characteristics, and has effective corrosion resistance. It is used as an electromagnetic material for corrosive environments as a material for cold forging.

Claims (3)

By mass
C: 0.015% or less,
Si: 0.18 to 2.5%,
Mn: 0.5% or less,
P: 0.03% or less,
S: 0.06% or less,
Ni: 0.1 to 0.34%,
Cr: 4 to 15%,
Al: 0.5-4%
O: 0.01% or less,
N: 0.015% or less,
An electromagnetic stainless steel excellent in low-temperature toughness, characterized by comprising a balance Fe and having a grain size number of 3 or more in the steel. The steel according to claim 1, further, Ti, electromagnetic stainless steel with excellent low temperature toughness characterized in that the addition below 1% of one or two or more of Z r. An electromagnetic stainless steel excellent in low-temperature toughness, characterized by further adding 1% or less of one or two of Mo and Cu to the steel described in claim 1 .