JPH0215142A - Soft magnetic steel - Google Patents

Abstract

PURPOSE:To obtain the title steel combining excellent cold forgeability, magnetic responsibility and corrosion resistance by forming it with the compsn. in which each content of C+N, Si, Mn, Cr and Al is regulated and constituted of the balance Fe with impurity elements. CONSTITUTION:The above soft magnetic steel is formed from the compsn. contg., by weight, <=0.03% (C+N), 0.21 to 0.40% Si, 0.21 to 0.40% Mn, 7 to 13% Cr, 1 to 5% Al and the balance Fe with impurity elements. The soft magnetic steel has excellent magnetic responsibility of <=0.8m sec relaxation time and has excellent cold forgeability of <=47kgf/mm<2> tensile strength. The soft magnetic steel furthermore has excellent machinability and corrosion resistance. The steel is therefore applicable to a proportional control-type electromagnetic valve, etc., of a pulse operating electronic fuel injection system or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a soft magnetic steel having excellent magnetic response, cold forgeability, and the like.

[Prior art]

For example, magnetic core materials used in proportional control type solenoid valves such as electronic fuel injection devices in automobile engines, or magnetic sensors are required to have excellent magnetic response in order to increase the pulse frequency of solenoid valve operation. It is being Such materials are required to have excellent corrosion resistance in order to improve their environmental resistance, and also to have excellent cold forgeability, which is essential for reducing costs.

Conventionally, the magnetic core materials for these devices were pure iron,
3%Si iron, 13%Cr-2.5%Si steel, 13%Cr
-1%5i-0,25%AI! steel is used.

[Problem to be solved]

However, although pure iron has excellent cold forgeability, it has poor magnetic response. Furthermore, like pure iron, 3% Si iron also has poor magnetic response, and is also poor in corrosion resistance and cold forgeability.

Further, 13Cr-2,5Si steel is excellent in single bend corrosion resistance, but is inferior in cold forgeability. Further, 13Cr-ISi-0,25Aff steel was excellent in corrosion resistance and machinability, but unsatisfactory in cold forgeability and magnetic response.

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

The present invention provides a soft magnetic steel that has excellent magnetic response with a relaxation time of 0.8 m5ec or less, excellent cold forgeability with a tensile strength of 47 Kgf/mm2 or less, and also has excellent machinability and corrosion resistance. This is what I am trying to do.

[Means for solving problems]

The present invention was made in view of the above-mentioned drawbacks of conventional steel, and is the result of extensive research into the effects of various alloying elements on magnetic response, corrosion resistance, cold forgeability, etc.
This has led to the completion of the present invention. That is, the present invention is based on new findings as described below.

Firstly, Fe-Cr-AP, in the components Cr7-13
% (weight ratio, hereinafter the same), when 8 ρ is added in a composite amount of 1 to 5%, the magnetic response is significantly improved.

Secondly, when 7 to 13% Cr and 1 to 5% Al are added in combination, an amazing improvement in corrosion resistance that cannot be expected by adding them alone can be obtained.

Furthermore, thirdly, in order to maximize the effect of adding Cr and Aff, it is necessary to add C, N, and S, which are solid solution strengthening elements.
It has been found that it is necessary to reduce impurity elements such as i, Mn, and other impurity elements such as Cu, Ni, and MO as much as possible. And, fourthly, when the impurity level is controlled to a low value that exceeds the common sense of ordinary alloy steel and stainless steel, the tensile strength is 47 kg.
It has been found that a soft magnetic steel having excellent cold forgeability of approximately f/mm2 can be obtained.

Based on these findings, the present invention contains 7 to 13% of Cr and 1 to 5% of AE, which significantly improves the magnetic response corrosion resistance without increasing the tensile strength. Along with the above Cr and AP, C+N0.
03% or less, Si0.21-0,40% Mn0.21
By suppressing the content to ~0.40%, cold forgeability was significantly improved.

Further, when 0.3% or less of Ti is contained in addition to the above composition, cold forgeability and corrosion resistance can be further improved.

Furthermore, the composition includes So, 0.5% or less, and Sea.

05% or less, Bi 0.3% or less, Pb 0.3% or less, and Zr, 0.2
% or less, and Te 0.03% or less, the machinability can be further improved without impairing the cold forgeability.

Therefore, the present invention has excellent magnetic responsiveness with a relaxation time of 0.8 m5ec or less, and a tensile strength of 47 kg.
It is a soft magnetic steel that has excellent cold forging properties with f 7mm2 or less and a limit workability of 60% or more, and also has excellent corrosion resistance and machinability. It is an alloy suitable for etc.

That is, the first invention of the present invention has a weight ratio of C1N0903.
% or less, Sin, 21-0.40%3Mn0.21-0
．． 40%, 7 to 13% of Cr, and 1 to 5% of AN, with the balance consisting of Fe and impurity elements. Further, the second invention further includes Tie in the first invention at 30% or less, and the magnetic responsiveness of the first invention,
It has further improved corrosion resistance and cold forgeability. Further, the third invention further provides 30.05% or less of S in the first invention.
One or more of e0.05% or less, B1013% or less, Pb0.3% or less, and Zr0.2% or less, T
It contains one or two of e0.03% or less, and improves machinability without impairing the cold forgeability of the first invention.

Next, the reason for limiting the chemical components as described above will be explained.

Cr Near - 13% Cr is an element that improves magnetic response and corrosion resistance, especially 1 to 13%.
When added in combination with 5% AP, the effect becomes remarkable. If the Cr content is less than 7%, the effect is not sufficient and excellent magnetic response and corrosion resistance cannot be obtained, so the lower limit is set to 7%. However, if the content exceeds 13%, it will actually impair magnetic response and cold forgeability, so the upper limit should be set at 13%.
And so.

Aj2: 1-5% Like Cr, Aj2 is the main element of the present invention that improves magnetic response and corrosion resistance, and its effect becomes particularly remarkable when it is added in combination with 7-13% Cr. If AP is less than 1%, excellent magnetic responsiveness cannot be obtained, so the lower limit was set at 1%. However, if it exceeds 5%, the magnetic response and cold forgeability will be impaired, so the upper limit was set at 5%.

CfN: 0.03% or less 2 C and N are elements that significantly impair magnetic response, corrosion resistance, and cold forgeability, and in the case of CfN, 0.025% or less is desirable, but considering actual manufacturability, 0.02% or less is preferred. 0.3% or less. In order to reduce the negative effects of C and N, C
It is desirable to add about 5 times as much Ti as 10N.

Si: 0.21-0.40% Si is an element required for deoxidation during normal steelmaking, and the lower limit is 0.
．． It was set at 21%. However, it is an element that significantly impairs magnetically responsive cold forgeability.

Therefore, it is preferable to set the upper limit to 0.3%, but
Considering actual manufacturability, it was set to 0.4% or less.

Mn: 0.21 to 0.40% Mn, like Si, is an element necessary for deoxidation during steel manufacturing, and the lower limit was set to 0.21%. However, magnetic response, corrosion resistance, and cold forgeability are significantly impaired.

Therefore, it is preferable to set the upper limit to 0.3%, but
In consideration of actual manufacturability, the content was set to 0.4% or less.

Ti: 0.3% or less Ti is an element that improves magnetic response, corrosion resistance, and cold forgeability, and exhibits the greatest effect when added about 5 times the amount of CfN. However, since addition of a large amount impairs cold forgeability, it is limited to 0.3% or less.

S: 0.05% or less, Se: 0.05% or less S and Se are added to improve machinability.

Adding too much will impair cold forgeability, so the upper limit should be set at 0°05.
%.

Bi: 0.3% or less, pb: o, 3% or less Bi and Pb are elements that improve machinability.

Addition of a large amount impairs cold forgeability, so the content was set to 0.3% or less.

Te: 0.03% or less.

Te is an element that improves machinability, promotes spheroidization of S inclusions and Se inclusions, and improves cold forgeability. However, since addition of a large amount actually impairs cold forgeability, the upper limit was set at 0.03%.

Zr: 0.2% or less.

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 0.2%.

[Example] Next, the characteristics of the alloy of the present invention will be clarified through examples in comparison with conventional steel and comparative steel. Table 1 shows the chemical composition of these test golds.

In Table 1, Nos. 1 to 8 are alloys of the present invention, and N.

1 and 2 are the first invention alloy No. 3 is the second invention alloy No.
, 4 to 8 are the third invention alloys.

In addition, No. C1 and C2 are conventional steels, and No. C1 is 3%
Si class, No, C2 is 13Cr-ISi-0,25AP
It is steel. No., C3, and C4 are comparative steels, and N.

C3 is steel containing Cr higher than the composition range of the present invention, N
αC4 is a steel containing lower An than the composition range of the present invention.

Next, for characteristic evaluation, 9
00° (HX2Hr heating and then cooling rate),
After heat treatment OOC/Hr, bow tensile strength, limit processing rate, magnetic response, corrosion resistance, and machinability were measured, and the results are shown in Table 2.

The tensile strength was measured using a JIS No. 4 test piece. Regarding the limit work rate, a compression test was performed using a test piece with a diameter of 14φ, a height of 21 mm, and a notch, based on the standards of the cold forging subcommittee of the Japan Society for Plasticity Working and the cold upsetting test method (provisional standard). The upsetting rate with a cracking incidence of 50% was measured.

Regarding magnetic response, we used a direct current BH) laser to fabricate a ring with an outer diameter of 24φ, an inner diameter of 16φ, and a thickness of 16mm as a test piece, wound it with two primary and secondary coils, and applied a pulse to the primary coil. The magnetic flux density was measured by applying a current and measuring and integrating the secondary voltage. Then, from the maximum value of magnetic flux density at this time, (1-(1/C)'1xtoo%(6
The time taken for the reduction (about 3%), that is, the relaxation time, was measured.

Regarding corrosion resistance, a salt spray test was conducted using a 5% NaCf aqueous solution at 35°C, and the speech rate was measured. 2. If the speech rate is less than 5%, ◎2. Those with a departure rate of less than 25 to 50% were rated Δ1, and those with an utterance rate of over 50% were rated ×.

Regarding machinability, using a test piece with a body thickness of 10 mm, the number of revolutions was 7.
A drilling test was conducted at 25 rpm, a drill of 5KH5φ, and a load of 4kg, and the time required to drill the hole was measured.

As is known from Table 2, C1 steel, which is a conventional steel, is inferior in cold forgeability, corrosion resistance, magnetic response, and machinability.

C2 steel has good corrosion resistance, but is poor in cold forgeability and magnetic response.

In addition, regarding C3 steel, which is a comparative steel, the Cr content is 14.
Since it is high at 36%, it has excellent corrosion resistance, but
Poor cold forging properties. C4 steel has a low AN content and therefore has excellent cold forgeability, but is inferior in magnetic response.

In contrast to these, the alloy of the present invention contains 7 to 13% Cr and A
Contains 1 to 5% N, and the values of solid solution strengthening elements such as C, N, and SiMn are as follows: C+N: 0.03% or less, Si: 0.
By setting Mn: 21 to 0.40% and Mn: 0°21 to 0.40%, the relaxation time of magnetic response is 0.8 m5ec.
It has excellent cold forgeability with a tensile strength of 47 kg f 7 mm2 or less and a limit workability of 60% or more, and is also excellent in corrosion resistance and machinability.

〔Effect of the invention〕

As explained above, the present invention has excellent cold forgeability and magnetic responsiveness by adding appropriate amounts of Cr and AP in combination and reducing solid solution strengthening elements such as Si, Mn, C, and N as much as possible. It also has corrosion resistance. Furthermore, Ti
Alternatively, machinability is improved without impairing cold forgeability by adding S, 5eBi, Pb, Zr and Te in combination as necessary.

The present invention is a soft magnetic steel suitable for magnetic core parts manufactured by cold forging, such as proportional control type solenoid valves such as pulse-actuated electronic fuel injection devices, or magnetic sensors, and has high practicality. be.

Claims (3)

[Claims] (1) Weight ratio of C+N0.03% or less, Si0.2
1-0.40%, Mn0.21-0.40%, Cr7-
A soft magnetic steel characterized by containing 13% and 1 to 5% Al, with the balance consisting of Fe and impurity elements. (2) Weight ratio of C+N0.03% or less, Si0.2
1-0.40%, Mn0.21-0.40%, Cr7-
13%, Al 1 to 5%, and further contains Ti 0.3% or less, with the balance consisting of Fe and impurity elements. (3) Weight ratio of C+N0.03% or less, Si0.2
1-0.40%, Mn0.21-0.40%, Cr7-
13%, Al 1 to 5%, and one or more of S0.05% or less, Se0.05%, Bi0.3% or less, Pb0.3% or less, and further Zr0.2% or less, A soft magnetic steel characterized in that it contains one or two of 0.03% or less of Te, and the remainder consists of Fe and impurity elements.