JPH02179855A - Free-cutting soft-magnetic stainless steel - Google Patents

Abstract

PURPOSE:To improve the magnetic properties, electric properties, weldability, corrosion resistance, machinability, etc., of the steel by adding specific amounts of Ti, etc., to a Cr steel and also reducing the total content of C and N and Al content, respectively. CONSTITUTION:A soft-magnetic stainless steel has a composition which consists of, by weight ratio, <=0.03% C, 2.0-3.0% Si, <=0.40% Mn, 0.015-0.050% S, 10-13% Cr, 0.05-0.20% Ti, <=0.03% N, <=0.010% Al, 0.10-0.30% Pb, and the balance Fe with impurity elements and in which C+N is regulated to <=0.05%. Further, 0.010-0.050% Se is incorporated to the above composition, if necessary. In this steel, magnetic properties are improved by the incorporation of Ti and the increase in Si quantity and also superior machinability is provided by means of Pb. This steel is suitable for fixed iron core, movable iron core, etc., for solenoid valve.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the magnetic properties, electrical properties, weldability, heat treatability, corrosion resistance, mechanical properties, and Regarding soft magnetic stainless steel with excellent rigidity.

[Conventional technology] Conventionally, the fixed iron core, movable iron core, etc. of solenoid valves have a maximum magnetic permeability,
Soft magnetic stainless steel was used because it has excellent magnetic properties such as magnetic flux density, electrical resistance, corrosion resistance, and mechanical properties.

In recent years, there has been a demand for soft magnetic stainless steel with even better magnetic and electrical properties, and 0,06C2,2Si 13Cr steel with an increased Si content of up to 2.2% has been developed.
Some of them are put into practical use. This soft magnetic stainless steel has good magnetic properties with a maximum magnetic permeability of 2000 or more, a magnetic flux density of 1100OG or more, and an electrical resistance of 90 μΩ-C.
1, the steel had excellent electrical properties, and was also relatively good in corrosion resistance, mechanical properties, and workability, making it an excellent steel in terms of quality balance.

[Problem to be solved by the invention] Recently, solenoid valves have been made smaller, and there is a demand for higher output and higher response, but the soft magnetic stainless steel mentioned above has insufficient magnetic properties and electrical resistance. It has been desired to develop a soft magnetic stainless steel that has better magnetic properties and electrical resistance, and also has superior fatigue strength after welding as welding applications are increasing. Furthermore, stainless steel is more difficult to cut than ordinary steel, and it has been strongly desired to improve the machinability of these soft magnetic stainless steels as well.

The present invention was made in view of the above-mentioned problems with conventional soft magnetic stainless steels, and has better magnetic properties, electrical properties, weldability, and heat treatability than conventional soft magnetic stainless steels.
The purpose is to provide a soft magnetic stainless steel with excellent corrosion resistance, mechanical properties, and rigidity.

[Means for Solving the Problems] The present invention is the result of extensive research in order to solve the drawbacks of conventional steels, and the present inventors have developed the magnetic properties of 12Cr steel, fatigue strength after welding, and heat treatment. As a result of investigating the effects of various alloying elements on properties and corrosion resistance, firstly, the magnetic properties were significantly improved by increasing the Cr content to 10 to 13%, adding Ti and Si, and reducing C and N. Second, the fatigue strength after welding is low A1, low CfN, and Ti
Thirdly, the heat treatment properties are improved by adding Ti.
Fourthly, corrosion resistance is improved by adding 10 to 13% Cr, adding Ti, and reducing CfN. Fifthly, machinability is improved by adding 10 to 13% Cr and reducing CfN. It has been found that the addition of s and Se can improve the magnetic and electrical properties without deteriorating them.

That is, the magnetic properties such as maximum permeability and magnetic flux density are 10~
In 13Cr stainless steel, improvements were made by reducing the amount of CfN and adding Ti and Si, and the amount of CfN was reduced to 0.
By containing 0.05% or less, Ti 0 about 1%, and Si 2% or more, the maximum magnetic permeability is 4400 or more, which is more than twice that of conventional steel (<0.06C-2, 23i-13Cr), and provides excellent magnetic properties. In addition, the fatigue strength after welding can be reduced to 0 by increasing the penetration depth of the weld by reducing the Ai amount to 0.010% or less.
．． By reducing the Ti content to about 1% and reducing the CfN content to 0.05% or less, the toughness after welding is improved, and the fatigue strength after welding is increased to 120 kgf /
With C type 2 or higher, it is possible to obtain twice the immersion weldability of the above-mentioned conventional steel.

Furthermore, even in post-processing annealing, the magnetic properties do not deteriorate even when annealing is carried out at a high temperature of 920°C due to the inclusion of approximately 0.1% T1, and coarsening of crystal grains at high temperatures is suppressed. ductility and toughness are improved. Therefore, what was conventionally held at 850° C. for 4 hours in a batch furnace can be annealed in a holding time of about 30 minutes by increasing the temperature, and can be annealed in a continuous furnace. By adopting a continuous furnace, productivity can be greatly improved and contribute to reducing heat treatment costs.

In addition, corrosion resistance is improved by reducing the amount of CfN and by using about 0.1% Ti.
This was greatly improved by the inclusion of . Furthermore, as shown in FIG. 1, the machinability can be improved by adding PB without deteriorating the magnetic and electrical properties.

Based on these findings, the present invention aims to reduce C+Nfi to 0.05% or less in 12Cr steel, increase the amount of Si to 2.0 to 3.0%, and increase the amount of Si to 2.0 to 3.0%. T
i, 0.015~0.050% S and 0.10~
Contain 0.30% pb and further increase the amount of A1 to 0.01
By regulating the content to 0% or less, the magnetic properties are greatly improved, as well as the fatigue strength after welding, heat treatment properties, corrosion resistance, electrical resistance, mechanical properties, and rigidity. The steel of the present invention has a maximum magnetic permeability of 4,400 or more, a magnetic flux density of 12,000 or more, and excellent magnetic properties, and has a fatigue strength of 120 kBf/cm after welding.
2 or higher, and even when annealed at a high temperature of 920°C, the magnetic properties do not deteriorate, and what was conventionally processed in a batch furnace can be processed in a continuous furnace, greatly improving productivity. It also has electrical resistance, corrosion resistance,
It is a soft magnetic stainless steel with excellent mechanical properties and rigidity, and the present invention can fully respond to miniaturization, high output, and high response of electromagnetic valves.

That is, the steel of the present invention is the first steel of the invention, and the weight ratio is ``
(C: 0.03% or less, Si: 2.0-3.0%, Mn
; 0.40% or less, S; 0.015 to 0.050%, C
"; 10-13%, Ti; 0.05-0.20%, N,
0.03% or less, Al; 0.010% or less, Pb; O.

10 to 0.30%, c+N: 0.05% or less, and the remainder consists of Fe and impurity elements. In order to further improve the stiffness of the first invention steel, the second invention steel is further coated with Sego, 010 to 0.
In order to further improve the corrosion resistance of the first invention, the third invention further contains Mo; 3% or less, N
i; 0.50% or less, Cu, 0.50% or less, S: 0.
0.005% or less.

The reasons for limiting the composition of the steel of the present invention will be explained below.

C is an element that impairs magnetic properties, fatigue strength after welding, heat treatability, and corrosion resistance, and in the present invention, it is desirable to reduce it as much as possible, and the upper limit is set to 0.03%. Note that in order to further improve magnetic properties, weldability, and heat treatability, it is desirable that the content be 0.015% or less.

Si improves magnetic properties such as maximum permeability and magnetic flux density,
It is an element that increases electrical resistance, and is an important element for soft magnetic steel, and must be contained in an amount of at least 2.0%. However, even if Si is contained in an amount exceeding 3.0%, there is little improvement in magnetic properties and the ductility and toughness are impaired, so the upper limit was set at 3.0%.

Like Si, Mn is an element necessary for deoxidation during steel manufacturing,
The upper limit is 0.
It was set at 40%.

Cr is a basic element that gives stainless steel corrosion resistance f1, and must be contained in an amount of at least 10% or more.

However, if the content increases, magnetic properties such as magnetic flux density will be impaired, so the upper limit was set at 13%.

Ti significantly improves magnetic properties such as maximum permeability and magnetic flux density, and also improves heat treatment properties. Furthermore, Ti is an element that also improves corrosion resistance, and is the most important element in the present invention. In order to obtain these effects, it is necessary to contain at least 0°05% or more, and the lower limit is set at 0°05%. However, even if it contains more than 0.20% of Ti, the effect will be saturated, so
The upper limit was set at 0.20%.

N is an element that impairs magnetic properties, fatigue strength after welding, and heat treatment properties, and it is desirable to reduce its content as much as possible, with the upper limit set at 0.03%.

CfN is an element that impairs magnetic properties, fatigue strength after welding, and heat treatment properties.6 In the present invention, it is necessary to reduce the amount of CfN as much as possible, and the upper limit is set to 0.05%.

S is an element that impairs corrosion resistance but improves machinability.

In order to obtain the stiffness that is ff, it is necessary to contain 0.015% or more, and the lower limit is set to 0.015%. However, if S is contained in an amount exceeding 0.050%, corrosion resistance will be impaired, so the upper limit was set at 0.05%.

A1 is an element that impairs fatigue strength after welding.

However, by lowering A1, it is an element that can increase the penetration depth of the weld and improve the fatigue strength.In the present invention, it is desirable to reduce its content as much as possible, and its upper limit was set to 0.010%.

Se and pb are elements that improve machinability.

To obtain excellent stiffness, Se should be 0.010%
As mentioned above, it is necessary to contain Pb at least 0.10%, and the lower limit is 0.010% for Se and 0.10% for Pb.
%. However, Se 0.050%, PbI2.3
If the content exceeds 0%, the magnetic properties will be impaired, so the upper limit was set at t3e0.050'A and PbO130%.

Mo, Ni, Cu, and S are elements that improve corrosion resistance in the present invention. However, if Mo exceeds 3% and Ni and Cu exceed 0.5% each, the magnetic properties will be impaired, so the upper limit is M.

was 3%, and Ni and Cu were 0.5%. Further, although S is an element that improves machinability, it is also an element that reduces corrosion resistance. In order to obtain excellent corrosion resistance, 0.0
0.05%, and the upper limit is 0.005%.
And so.

[Example] Next, the characteristics of the present invention will be clarified by comparing the characteristics with conventional steel and comparative steel using examples.

Table 1 shows the chemical composition of these test steels.

In Table 1, steels A to L are invention steels, and steels A to C are first steels.
The invention steels, D to F steels, are second invention steels, and G to L steels are third invention steels. M to P steels are comparative steels, M steel has a high A1 content, N steel does not contain Ti, 0w4 has a high FC system content I, and e steel has a low S;. Further, Q to S steels are conventional steels.

(Margins below) Table 2 shows the maximum magnetic permeability, magnetic flux density, and It shows electrical resistance, hardness, corrosion resistance, rigidity, and fatigue strength after welding. Regarding the magnetic properties, a test piece was prepared using a direct current BH) laser with an outer diameter of 24φ, an inner diameter of 16φ, and a thickness of 16m1.
A ring marked * was created and the maximum magnetic permeability and magnetic flux density were measured. flXlX resistance was measured using the hobby stone bridge method as a test piece of 1.2φX50C1am.
It was measured using a line. Regarding corrosion resistance, 3
．． A 60-minute salt spray test was conducted using a 5% NaCl aqueous solution, and the rusting rate was measured. Those with a rusting rate of less than 1% were given a rating of 5, and those with a rusting rate of less than 1% to 10% were given a rating. 4, those with a rusting rate of less than 10 to 30% are given a rating of 3, those with a rusting rate of less than 30 to 60% are given a rating of 2, and those with a rusting rate of less than 60% are given a rating of 3.
A score of 1 was given as 0% to 100%. Furthermore, the rigidity was measured by drill life, and the fatigue strength after welding was measured by welding 5US304 and performing a pressure fatigue test at plasma 53AX 100V and t = 2mm. As is known from Table 2, Q steel, which is a conventional steel, has an electrical resistance of 92 μΩ-ell and a hardness of Hv1 type 8, which is excellent in terms of electrical resistance and hardness, but it does not meet the required amount. Because it does not contain Ti and has a high C1N and A content, it has insufficient magnetic properties with a maximum permeability of 2300 and a magnetic flux density of 11200G, and the fatigue strength after welding is 90kgf/em. In addition, R31l has a low Si content of 0.45% and does not have the desired Ti content.
In addition, it contains no amount of Al, C+N, and CrJ.
Due to the high i, the magnetic properties are significantly inferior, with a maximum magnetic permeability of 900 and a magnetic flux density of 7800 G, and the electrical resistance is also low at 60 μΩ-elm, and the fatigue strength after welding is low. It is inferior in hardness and stiffness, and like R steel, S#l has a low Si content and does not contain the desired Ti content,
Furthermore, due to the high Al content and C+N content, magnetic properties, electrical resistance, hardness, and stiffness are inferior.

In addition, M steel, which is a comparative steel, has a fatigue strength of 40 kgf/cIl12 after welding because it contains a large amount of A1.
As for Na, by not containing Ti, the maximum magnetic permeability is low at 3200, the magnetic flux density is low at 11200G, and the fatigue strength after welding is also low.As for Q steel, C amount and C+Nil
The maximum magnetic permeability is 3000. It has low magnetic properties with a magnetic flux density of 11,400G, and a low fatigue strength of 100 kgf/am2 after welding, and is also poor in corrosion resistance and rigidity, and P steel does not contain the necessary amount of Si. Therefore, the maximum permeability is 3800
Its magnetic properties are low, with a magnetic flux density of 10,600 G, and its electrical resistance is also low, at 80 μΩ-ell.

On the other hand, A to Mw4, which are the steels of the present invention, reduce the amount of C0N and the amount of Al as much as possible, and have a 0.05~0.0.
Contains 20% Ti and the amount of Si is 2.0 to 3.0
%, S to O, O], 5 to 0.050%, Cr to 10 to 1
By setting it to 3%, the maximum magnetic permeability is 4400 or more,
It has excellent magnetic properties with a magnetic flux density of 12,000 G or more, and an electrical resistance of 92 μΩ-cr or more.
120 kgf/c for fatigue strength after welding
It has excellent electrical properties and weldability, with a value of over 100 m'', and corrosion resistance with a rusting rate of less than 10%, hardness of Hv 1 type 0 or more, and machinability of 500 theory or more. It also has excellent rigidity.

[Effects of the Invention] As described above, the steel of the present invention significantly improves magnetic properties by reducing the C+N content, by containing an appropriate amount of Ti, and by increasing Si, and by containing an appropriate amount of Pb. Improved machinability, heat treatment properties, corrosion resistance,
It also has excellent electrical properties, mechanical properties, and stiffness.
The steel of the present invention is a free-cutting soft magnetic stainless steel suitable for fixed iron cores, movable iron cores, etc. of electromagnetic valves, and has high practicality.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between Pb content and magnetic properties. Figure 1 PB amount (・mu)

Claims (3)

[Claims] (1) C: 0.03% or less, Si: 2.0 in terms of weight ratio
~3.0%, Mn; 0.40% or less, S; 0.015~
0.050%, Cr; 10-13%, Ti; 0.05-
0.20%, N; 0.03% or less, Al; 0.010%
Below, Pb; contains 0.10 to 0.30%, and C +
A free-cutting soft magnetic stainless steel characterized by containing N: 0.05% or less, with the remainder consisting of Fe and impurity elements. (2) C: 0.03% or less, Si: 2.0 in terms of weight ratio
~3.0%, Mn; 0.40% or less, S; 0.015~
0.050%, Cr; 10-13%, Ti; 0.05-
0.20%, N; 0.03% or less, Al; 0.010%
Hereinafter, Pb; 0.10 to 0.30%, Se; 0.010
A free-cutting soft magnetic stainless steel characterized by containing ~0.050%, C+N: 0.05% or less, and the remainder consisting of Fe and impurity elements. (3) C: 0.03% or less, Si: 2.0 in terms of weight ratio
~3.0%, Mn; 0.40% or less, Cr; 10-13
%, Ti: 0.05-0.20%, N: 0.03% or less, Al: 0.010% or less, Pb: 0.10-0.30
%, and C+N; 0.05% or less, and further contains M
o: 3% or less, Ni: 0.50% or less, Cu: 0.50
% or less, S: 0.005% or less, and the free-cutting soft magnetic stainless steel is characterized by containing one or more of S;