JPH0463249A - Soft magnetic stainless steel having high magnetic flux density and low coercive force - Google Patents

Abstract

PURPOSE:To obtain a soft magnetic stainless steel having the characteristics of high magnetic flux density and low coercive force and excellent in corrosion resistance by specifying the compsn. constituted of C, Si, Mn, S, Ni, Cr, Cu, Al, O, N and Fe. CONSTITUTION:This is a soft magnetic stainless steel contg., by weight, <=0.010% C, <=0.10% Si, <=0.10% Mn, <=0.010% S, <=0.10% Ni, 11 to 13% Cr, <=0.10% Cu, 0.05 to 0.15% Al, <=0.0070% O, <=0.0100% N, <=0.015% C+N and the balance Fe with impurity elements and having high magnetic flux density and low coercive force. By using this steel, the miniaturization of a magnetic circuit for a solenoid valve or the like is permitted.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a high magnetic flux device with excellent magnetic properties, electrical properties, and corrosion resistance that is used in electronic fuel injection devices (EFI), solenoid valves, magnetic sensors, etc. of automobiles, etc. It concerns low density, coercive force, soft magnetic stainless steel.

(Prior art) Before 1975, JIS@5VS430.5t was used as the magnetic core material for parts that required corrosion resistance in electronic fuel injection devices, solenoid valves, magnetic sensors, etc. used in automobiles.
IS410 etc. have been used. Later, in the early 1970s, F
The e43Cr-ISi-0,2581 needle was developed and is in use to date. However, in line with the recent trend toward miniaturization of actuators such as solenoid valves, there is a strong demand for miniaturization of magnetic circuits (fe13Cr-ISi
-0.25AI steel is no longer suitable.

Under these circumstances, we developed Fe-13Cr-ISi-0,25Al11 while maintaining the corrosion resistance of stainless steel.
There was a strong desire to develop a new material with even higher magnetic flux density and superior soft magnetic properties than tijl.

(Problems to be Solved by the Invention) The present invention was made in order to solve the above-mentioned drawbacks of conventional steel, and it is necessary to provide corrosion resistance for electronic fuel injection devices, solenoid valves, etc., which have recently become very strongly required. The object of the present invention is to provide a soft magnetic stainless steel that has the characteristics of high magnetic flux density and low coercive force necessary to make it possible to downsize magnetic circuits, and has excellent corrosion resistance.

(Means for solving the problem) Materials used for electronic fuel injection devices, solenoid valves, etc. are cold worked when manufacturing the parts, so in order to prevent deterioration of magnetic properties due to the effects of processing strain, Heat treated to improve magnetic properties. In order to obtain excellent magnetic properties, especially low coercive force, it is necessary to perform heat treatment at a high temperature of 900°C or higher, but in conventional steels such as 5US430.5U3410, a γ loop exists at around 800 to 1100°C. 80
When heat treated at 0° C. or higher, the processing strain disappears, but since transformation occurs, the transformation strain remains after cooling and the magnetic properties deteriorate. On the other hand, when the heat treatment was performed at a low temperature of less than 800°C, the processing strain did not completely disappear and a low coercive force could not be obtained. On the other hand, Fe-13Cr
Although 4Si-0,25Allil does not undergo γ transformation at high temperatures, the magnetic flux density decreases due to the inclusion of Si and AI, making it impossible to obtain satisfactory magnetic properties.

The present inventors have discovered that conventional steel can be improved by the combined addition of Si and Al.
Noting that it was not possible to obtain excellent magnetic flux density by reducing the loop area and stabilizing the ferrite phase, we made the T-loop area smaller by more efficient component adjustment, and the T-loop area was reduced from 900 to 1200''. About the amount of addition of the component that makes it possible to obtain excellent magnetic properties by making it possible to obtain both low coercive force and high magnetic flux density by enabling heat treatment at a high temperature called C. As a result of extensive research, we have arrived at the present invention.

In order to reduce the γ loop region, austenite former elements such as Ni, Cu, C+N, Mn
Si, which is a ferrite former element,
It has been conventionally said that it is sufficient to add AI or the like.

However, it is currently not known exactly how effective each element is individually. In addition, in order to obtain high magnetic flux density, C
It is necessary to reduce all elements except r as much as possible. By utilizing recent excellent net-making technology, the present inventors were able to remove Cr (C+N, Si, Mn, Ni, Cu) to a level that could not be reached with conventional metallurgical methods.
, AI, 0, etc. were reduced, and the presence or absence of T loops was measured. However, it was found that if only the elements other than Cr were lowered, the T-loop would become smaller to some extent, but it would still exist in the heat treatment temperature range. Therefore, the ferrite former elements Si, AI, MO, Ti
As a result of further research on the effect of AI, compared to other elements, AI has the greatest effect of reducing the γ-loop region, and together with the effect of reducing the austenite former element, it has been found that AI has the greatest effect on reducing the γ-loop region. It was discovered that a single phase could be obtained. It was also found that AI has a smaller negative effect on reducing magnetic flux density than Si, and it also serves as a deoxidizing agent, so it was discovered that a very large effect can be obtained by adding a small amount. .

That is, as a result of thorough investigation and research into the influence of alloys on 13Cr stainless steel, the present inventors have reduced other elements as much as possible except for Cr, which ensures corrosion resistance, and
The minimum amount of A necessary to reduce the loop area and obtain the deoxidizing effect.
By adding I, we succeeded in securing magnetic properties (high magnetic flux density and low coercive force) at a level that could not be predicted conventionally.

That is, in the present invention, C: 0.010% or less in weight ratio,
Si: 0.10% or less, Mn: 0.10Z or less, S: 0
．． 010X or less, Ni: 0.10X or less, Cr: 11
~13%, Cu: 0.10% or less, Al: 0.05~
0.15%, O: 0.0070X or less, N: 0.010
Contains 0Z or less, C+N: 0.015% or less, and the remainder F
This is a soft magnetic stainless steel with high magnetic flux density and low coercive force, characterized by comprising e and impurity elements.

Next, the reasons for limiting the composition of the high magnetic flux density soft magnetic stainless steel of the present invention will be explained.

C, 0,010% or less C is an element that adversely affects magnetic properties and corrosion resistance, and in the present invention, it is desirable to reduce it as much as possible.
The upper limit was set to 0.010χ. Note that in order to further improve magnetic properties, it is desirable that the content be 0.005% or less.

Si: 0.10% or lessSi is a deoxidizing element, but it deteriorates magnetic properties, so
It is desirable to reduce it as much as possible, and the upper limit is 0.
It was set to 10χ.

Mn: 0.10% or less Since the content of Mn significantly impairs corrosion resistance and magnetic properties, it is desirable to reduce it as much as possible, and the upper limit is set at 0.10%.
I set it as X.

s ; o, oioz S is contained as an impurity in steel, but since it is an element that impairs magnetic properties, its upper limit was set to 0.010χ.

Cr; 11-131 Cr is an essential basic element for ensuring the necessary corrosion resistance and electrical resistance, and at the same time has the effect of narrowing the temperature range of the T phase. In order to fully obtain the above effect, at least 1
It is necessary to contain 1% or more. However, even if the content exceeds 13X, the effect of improving corrosion resistance is not large and the magnetic properties are also impaired, so the upper limit was set at 13χ.

AI, 0.05-0.15χ AI is an important element that makes the most of the features of the present invention,
It is an optimal element for narrowing the γ-loop region and obtaining a single ferrite phase in the heat treatment temperature range, and is also highly effective as a deoxidizing agent. In order to obtain this effect, the content must be 0.05% or more. However, if the content exceeds 0.15χ, the magnetic flux density and coercive force deteriorate, so the upper limit was set at 0.15χ.

0; 0.0070% or less Since 0 lowers the magnetic flux density and worsens the magnetic properties, it is desirable to have as little as possible, but in consideration of actual manufacturability, the upper limit was set at 0.0070χ.

N, 0.0100% or less N is contained in steel as an impurity, but limiting it to 0.0100% or less is effective in improving magnetic properties, so the upper limit was set to 0.0100χ.

C+N: 0.015% or less C and N are elements that combine with Cr to form carbonitrides, lowering corrosion resistance and also deteriorating magnetic flux density and coercive force. It also has the effect of being an austenite former element and expands the T-loop region.
It is necessary to reduce as much as possible, and the upper limit is set to 0.015χ.

Ni: 0.10% or less, Cu: 0.10% or less Ni and Cu are elements that improve corrosion resistance, but they are austenite former elements that expand the T-loop region and worsen magnetic properties. .

In the present invention, since the magnetic properties are the most important, it is necessary to reduce them as much as possible, and the upper limit is 0.10 for both.
It was set as χ.

(Example) Next, the features of the present invention will be clarified by comparing them with conventional steel and comparative steel through examples. Table 1 shows the chemical composition of the test steel.

(Left below) In Table 1, steels 1 to 7 are the inventive mesh, steels 8 to 14 are comparative steels, and steel 15 is the conventional mesh, Fe-13Cr-I.
Si-0,25A]M.

The test steels in Table 1 were melted in an electric furnace, hot rolled,
Heat treatment was performed under the conditions of 0°C for 2 hours and a cooling rate of 100'C/hour, and the magnetic flux density, coercive force, corrosion resistance, and presence or absence of transformation to γ phase at high temperatures were measured.

The magnetic properties were measured using a DC type BH tray sheet with an outer diameter of 24 mmφ, an inner diameter of 16 mmφ, and a thickness of 16IIIl as a test piece.
A ring test piece was manufactured and the magnetic flux density and coercive force were measured.

Regarding corrosion resistance, a salt spray test was conducted in accordance with JIS Z2371, and the rust rate was measured. ◎ if the rust rate was less than 5%, ○ if the rust rate was 5% or more and less than 25%, and 5 if it was 25% or more.
A value of less than 0% was designated as Δ, and a value of 50% or more was designated as ×.

The presence or absence of transformation to γ phase at high temperature is determined by diameter 3I and length 1
A test piece of 0IllI11 was prepared, heated to 1000''C, and then determined from the dimensional change of the test piece during cooling, which was measured using a Formaster tester.

Table 2 shows the measured magnetic flux density, coercive force, corrosion resistance, and presence or absence of transformation to γ phase.

(Left below) Table 2 shows that the steel has significantly superior magnetic properties compared to conventional steel, and also has excellent corrosion resistance.

(Effects of the Invention) As detailed above, the high magnetic flux density and low coercive force soft magnetic stainless steel of the present invention ensures corrosion resistance and electrical resistance by adding the necessary minimum amount of Cr, and has austenite former elements. By reducing all of them as much as possible and adding a small amount of AI, which is a ferrite former element, the T-loop area can be made smaller by adding a smaller amount of ferrite former element than conventional steel, and processing distortion can be completely eliminated. 80
It has become possible to perform heat treatment at temperatures above 0°C without causing transformation, and it has become possible to significantly improve both magnetic flux density and coercive force compared to conventional steels. Therefore, the present invention enables miniaturization of magnetic circuits such as electromagnetic valves, and has high practicality in industry.

As is clear from Table 2, the comparative steel 8tiA is
Due to the high Cr content, although the corrosion resistance is excellent, the magnetic flux density is inferior.The 9 steel has a low Cr content, so the coercive force is inferior due to the corrosion resistance and γ transformation, and the 10
Because steel has a low AI content, its magnetic properties such as magnetic flux density and coercive force are inferior due to the influence of γ transformation. Steel No. 11 has a high Si and AI content, so it has an inferior magnetic flux density, and steel No. Since copper has a high C+N content, it has poor corrosion resistance, and transformation to γ phase occurs at high temperatures, which causes transformation strain during heat treatment, resulting in poor magnetic properties.
, due to the high Cu content, the magnetic properties are inferior due to transformation strain like the 12 steel, and the 14 steel has a high Mn content, so the 12.13! Similar to IT, it has poor magnetic properties.

Claims (1)

[Claims] 1. Weight ratio: C: 0.010% or less, Si: 0.1
0% or less, Mn 0.10% or less, S: 0.010% or less, Ni: 0.10% or less, Cr: 11-13%, Cu:
0.10% or less, Al: 0.05-0.15%, O: 0
．． 0070% or less, N: 0.0100% or less, C+N:
A high magnetic flux density, low coercive force soft magnetic stainless steel characterized by containing 0.015% or less, with the remainder consisting of Fe and impurity elements.