JPS6335757A - Corrosion-resisting soft-magnetic steel - Google Patents

Abstract

PURPOSE:To obtain a corrosion-resisting soft-magnetic steel excellent in magnetic properties, electric properties, corrosion resistance, machinability, and cold forgeability, by specifying a composition consisting of C, N, Si, Mn, Cr, Al, and Fe. CONSTITUTION:The corrosion-resisting soft-magnetic steel has a composition consisting of, by weight, <=0.015% C+N, <=0.20% Si, <=0.20% Mn, 7-13% Cr, 2-5% Al, and the balance Fe with impurity elements and further containing, if necessary, <=0.08% Ti and/or one or more kinds among <=0.050% S, <=0.050% Se, and <=0.30% Pb and further <=0.20% Zr and/or <=0.030% Te, and it also has >=about 90muOMEGAcm electric resistance and <=about 44kgf/mm<2> tensile strength. Further, the above steel is excellent in corrosion resistance, magnetic properties, and machinability and is suitable for use in magnetic core parts for an electronic fuel injection equipment, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to soft magnetic steel materials, and more specifically to magnetic properties, electrical properties, corrosion resistance, and machinability used in electronic fuel injection devices, solenoid valves, magnetic sensors, etc. and a corrosion-resistant soft magnetic steel with excellent cold forgeability.

[Conventional technology] The magnetic core materials of electronic fuel injection devices, solenoid valves, magnetic sensors, etc. developed in recent years have high electrical resistance to improve response, excellent magnetic properties, and environmental resistance. There was a need for excellent corrosion resistance to improve this, as well as excellent cold forgeability, which is essential for reducing costs. The magnetic core materials for these devices include pure iron, 3Si iron, and 13Cr.
-2,5Sj clear, 13Cr-ISiO,25AI steel is used.

However, although pure iron has excellent magnetic properties and cold forgeability, it has low electrical resistance and poor corrosion resistance. Furthermore, although 3% Si steel has an electrical resistance superior to that of pure iron, its value is not necessarily sufficient at 60 μΩem, and it is also inferior in corrosion resistance and cold forgeability. 13Cr-2°5Siljl has excellent corrosion resistance and electrical resistance, but is inferior in cold forgeability.

Further, 13Cr-ISi-0,25AI steel has excellent corrosion resistance and machinability, but is not satisfactory in cold forgeability, magnetic properties, and electrical resistance.

As described above, none of the conventional steels satisfies all of magnetic properties, electrical resistance, cold forgeability, and corrosion resistance at the same time.

[Problems to be Solved by the Invention] The present invention has been made to solve the above-mentioned drawbacks of conventional scales used as magnetic core materials for electronic fuel injection devices, etc. The electrical resistance required for magnetic core materials such as magnetic sensors is 90μΩC11 or more, which shows excellent electrical resistance, and the tensile strength is 44Kgf/w+
It is an object of the present invention to provide a corrosion-resistant soft magnetic steel having a diameter of less than m2, having excellent cold forgeability, and further having excellent corrosion resistance, magnetic properties, and rigidity.

[Means for solving the problem] The corrosion-resistant soft magnetic steel of the present invention has a weight ratio of C+N, 0.0
15% or less, Si; 0.20% or less, Mn; 0°20
% or less, C'; 7 to 13%, Al; 2 to 5% as essential components, optionally containing Ti; 0.08% or less, further optionally containing S, 0.050% or less, Se; 0.0
50% or less, Pb, lfi or more of 0.30% or less, Zr; 0.20% or less, Te; O.

0.030% or less, and the remainder consists of Fe and impurity elements.

In view of the above-mentioned drawbacks of conventional steel, the present inventors have completed the present invention as a result of extensive research into the effects of various alloying elements on the magnetic properties, electrical resistance, corrosion resistance, and cold forgeability of pure iron. The present invention is based on the following new findings.

First, electrical resistance and tensile strength are contradictory properties, and when S1 is increased to increase electrical resistance, tensile strength increases significantly and cold forgeability is significantly impaired.

This is clear from the line in FIG. 1, which shows the relationship between tensile strength and electrical resistance for Fe-3i steel. On the other hand, in the Fe-Cr-A I component system, Cr;
7-13%, AI.

When 2 to 5% of Fe-Cr-A is added simultaneously, Fe-Cr-A
As is clear from FIG. 1, which shows the relationship between tensile strength and electrical resistance for I-series steels, it has been found that the electrical resistance can be significantly increased without substantially increasing the tensile strength.

Second, we discovered that the combined addition of 7 to 13% Cr and 72 to 5% Al results in amazing improvements in corrosion resistance and magnetic properties that would not be expected by adding them alone. be.

Furthermore, thirdly, in order to maximize the effects of cold forgeability of Cr-Al, it is necessary to reduce C, N, Si, and Mn, which are solid solution strengthening elements, as much as possible. This is what we discovered. As a result, it has an excellent electrical resistance of 100μΩC- or more, and a tensile strength of 42
It has been discovered that a corrosion-resistant soft magnetic steel having excellent cold forgeability of Kgf/mm" or less can be obtained.

Based on these findings, the present invention contains 7 to 13% of Cr and 2 to 5% of Al to significantly improve electrical resistance, corrosion resistance, and magnetic properties without increasing tensile strength. and the above weight % of Cr
and AI and C+N; 0.015% or less,
By suppressing the H content to 0.20% or less of Si and 20% or less of MrBo, cold forgeability is greatly improved.

Furthermore, in addition to the above, the present invention contains Ti; 0.08% or less to improve corrosion resistance, and S;
0.050% or less, Sago, 050% or less r'13
; Contains 0.30% or less, and Zr; 0°20
By containing 0.030% or less of Te, the rigidity is improved without impairing cold forgeability.

Therefore, the present invention has an excellent electrical resistance of 90 μΩel1 or more, and a tensile strength of 44 Kgf/I*112.
Below, it is a corrosion-resistant soft magnetic steel that has excellent cold forging properties with a limit workability of 60% or more, and also has excellent corrosion resistance, magnetic properties, and rigidity. It is a candle suitable for etc.

The first invention of the present invention has CI-N as ff1Fi ratio:
0.

015% or less, Si; 0.20% or less, Mn; 0.2
01Y or less, C: 7 to 13%, AI: 2 to 5%, and the remainder consists of Fe and impurity elements.

The second invention further improves the magnetic properties, corrosion resistance, and cold forgeability of the first invention by further containing 0.08% or less of TiHo. The third invention further includes S;
0.050% or less, Se: 0.050% or less, Pb: 0
．． One or more of 30% or less and further Zr; 0.20
% or less, Te: 0.030% or less, and the rigidity is improved without impairing the cold forgeability of the first invention.

The fourth invention is the second invention: S: 0.050% or less, Se: 0
．． 050% or less, Pb: 0.30% or less, and further Zr: 0.20% or less, Te: 0.030%
By containing one or more of the following, machinability is improved without impairing the cold forgeability of the second invention.

Next, the reason for limiting the component composition in the present invention will be explained.

Cr; 7 to 13% Cr is an element that improves corrosion resistance, electrical resistance, and magnetic properties, and its effects become particularly pronounced when added in combination with 2 to 5% of AI. If the Cr content is less than 7%, the effect is not sufficient and excellent corrosion resistance and electrical resistance cannot be obtained.
The lower limit was set at 7%8.However, if the content exceeds 13%, cold forgeability is impaired, so the upper limit was set at 13%.

Al; 2 to 5% Al, like Cr, is a major element in the present invention that improves corrosion resistance, electrical resistance, and magnetic properties, and especially when added in combination with 7 to 13% Cr, its effect becomes an edict. . If the Al content is less than 2%, excellent corrosion resistance and electrical resistance cannot be obtained, so the lower limit was set at 2%.

However, if the content exceeds 5%, cold forgeability will be impaired, so the upper limit was set at 5%.

c+N: 0.015% or less C and N are elements that significantly impair magnetic properties, corrosion resistance, and cold forgeability. C+N: 0.010% or less is desirable, but considering actual manufacturability, 0.015% The following was made. In order to reduce the negative effects of C and N, it is necessary to (
It is desirable to add about 5 times as much Ti as C1N.

Si: 0.20% or less Si is an element normally required for deoxidation during refining, but Fc
-S not particularly necessary in Cr-Al steelmaking
Since i is an element that significantly impairs cold forgeability, 0,1
0% or less is preferable, but considering actual manufacturability, it is 0.2
It was set to 0% or less.

Mn: 0.20% or less Is Mn good for corrosion resistance, magnetic properties, and cold forgeability? It is desirable that the content be 0.10% or less since it causes significant damage, but it is set to 0.20% or less in consideration of actual manufacturability.

Ti: 0.08% or less Ti is an element that improves magnetic properties, corrosion resistance, and cold forgeability, and exhibits the greatest effect when added at about 5 positions of C + N N. However, addition of a large amount impairs cold forgeability, so it is limited to 0.08% or less.

S, 0.050% or less, Se; 0.050% or less S, S
E is added to improve machinability, but addition of too much l impairs cold forgeability, so is there an upper limit? It was set to 0°050%.

Pb, 0.30% or less Pb is an element that improves machinability, but the addition of 3 violet impairs cold forgeability, so it was set to 0.30% or less.

Tc: 0.030% or less Te is an element that improves machinability, promotes spheroidization of S inclusions and Se inclusions, and improves cold forgeability. However, addition of a large amount impairs cold forgeability, so the upper limit was set at 0.030%.

Zr: 0.20% Zr is an element that spheroidizes S inclusions and Se inclusions and improves cold forgeability. However, since addition of a large amount impairs cold forgeability, the upper limit was set at 0.20%.

[Example] Next, the characteristics of the steel of the present invention will be clarified by comparing it with conventional and comparative steels through examples. Table 1 shows the chemical composition of these test steels.

(Left below) In Table 1, Al~A9 steels are steels of the present invention, and Al-A9 steels are steels of the present invention.
3 is the first invention steel, A4 is the second invention steel, and A5 to A8 are the third invention steel.
Invention steel A9 is the fourth invention steel.

81~B4 steel is conventional steel, B1 steel is pure iron, B2lI4 is 3% Si steel, B3 steel is 13Cr 2.5Si steel, B4
jl is 13Cr-ISiO, 25AI steel. C
Steels 1 to C3 are comparative steels, C1 #l is a steel containing Cr lower than the composition range of the present invention, C2 steel is a steel containing Cr higher than the composition range of the present invention, and C3 #l is a steel containing Cr higher than the composition range of the present invention. It is a steel containing Al lower than the composition range.

The test steels in Table 1 were held at 900°C for 2 hours, and then subjected to heat treatment at a cooling rate of 100°C/hour. The magnetic flux density, coercive force, corrosion resistance, electrical resistance, and rigidity were measured, and the results are shown in Table 2.

The tensile strength was measured using a JISJ test acid piece, and the limit workability was determined according to the cold forging subcommittee standards of the Japan Society for Plastic Technology and the cold upsetting test acid method (temporary standard). Based on the test piece, the diameter is 14φ and the height is 21mm.
A compression test was carried out using a notched skewer with a crack of 50 mm.
This is a measurement of the upsetting rate in %.

Regarding the magnetic properties, a DC type BH) laser was used to test the specimen, which had an outer diameter of 24φ, an inner diameter of 16φ, and a thickness of 16111m.
A ring was prepared and its magnetic flux density and coercive force were measured.

Regarding corrosion resistance, we conducted a salt water spray test using a 5% NaCl aqueous solution at 35°C and measured the rusting rate. O
, Δ is the rusting rate of 25 to 50%, and X is the rusting rate of 50% or more.

For electrical resistance, test pieces were measured using the Wheatstone bridge method: 1.2φX500m+*t! It was measured using

Regarding rigidity, using a test piece of 10IIg, rotation speed 725r, p, screw, drill 5KH5φ, back mold 4■ (
A test drive was conducted to measure the time required to drill a hole.

As is known from Table 2, Bl steel, which is a conventional steel, is inferior in terms of cold forgeability and magnetic flux density, but corrosion resistance and
It has poor electrical resistance and coercive force. B2U is inferior in terms of magnetic flux density, but has poor electrical resistance, cold forgeability,
It has poor corrosion resistance and coercive force. B3 steel has excellent corrosion resistance and electrical resistance, but is inferior in coercive force, magnetic flux density, and cold forgeability. B411 has excellent corrosion resistance and machinability, but is inferior in coercive force, magnetic flux density, and cold lid forgeability.

In addition, for C1 steel, which is a comparison steel, Cri is 5.2
Since it is as low as 0%, it is inferior in electrical resistance and corrosion resistance. As for C2 clear, since the Cr content is as high as 15.10%, the cold forgeability is poor. CB if
However, since the Al content is as low as 1.25%, the electrical resistance is poor.

On the other hand, the steel of the present invention, Al~89 Wei, has Cr
Contains 7 to 12% of Jtt, 2 to 5% of Aljl, and has an E & solubilization element value such as C, N, Si, Mn, etc., C-N: 0. O 15% or less, Si; 0.20% or less, Mn
; By making it extremely low at 0.20% or less, the electrical resistance is 90μΩC@ or more and the tensile strength is 44
It has excellent cold forgeability with a maximum working rate of 60% or more, and a magnetic flux density of 13,000G or more, and a coercive force of 1.O.
It has a smoothness of less than Oe5 and also has excellent corrosion resistance and machinability.

[Effects of the invention] *As explained above, the invention achieves excellent results by adding appropriate amounts of Cr and AI in combination and reducing solid solution strengthening elements such as Si, Mn, C, and N. It has electrical resistance, cold forgeability, magnetic properties, and corrosion resistance. Furthermore, by adding S, Se, Pb, Te, Zr, and Ti in combination as necessary, the present invention improves the rigidity without impairing cold forgeability. Electronic fuel injection′! It is a 1d six-way steel suitable for magnetic core parts manufactured by cold forging such as A position, ':r, and magnetic valves, and has high practicality.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between tensile strength and electrical resistance for Fe-Cr-Al series steel and Fe-9i series steel. Patent applicant: Aichi Steel Co., Ltd.

Claims (4)

[Claims] (1) C+N in weight ratio: 0.015% or less, Si;
0.20% or less, Mn; 0.20% or less, Cr; 7-1
A corrosion-resistant soft magnetic steel characterized by containing 3% Al, 2 to 5% Al, and the remainder consisting of Fe and impurity elements. (2) C+N in weight ratio: 0.015% or less, Si;
0.20% or less, Mn; 0.20% or less, Cr; 7-1
3%, Al: 2 to 5%, and Ti: 0.08% or less, with the remainder consisting of Fe and impurity elements. (3) C+N in weight ratio: 0.015% or less, Si;
0.20% or less, Mn; 0.20% or less, Cr; 7-1
3%, Al; Contains 2-5%, and S; 0.050%
Below, one or more of Se: 0.050% or less, Pb: 0.30% or less, Zr: 0.20% or less, Te
; Contains one or more of 0.030% or less, the balance being Fe
Corrosion-resistant soft magnetic steel characterized by comprising impurity elements. (4) C+N in weight ratio: 0.015% or less, Si;
0.20% or less, Mn; 0.20% or less, Cr; 7-1
3%, Al: 2 to 5%, Ti: 0.08% or less, and one of S: 0.050% or less, Se: 0.050% or less, Pb: 0.30% or less Above and more Z
1 out of r: 0.20% or less, Te: 0.030% or less
1. Corrosion-resistant soft magnetic steel characterized by containing at least one of Fe and the remainder consisting of Fe and impurity elements.