JPS62280349A - Soft-magnetic stainless steel for cold forging - Google Patents

Abstract

PURPOSE:To manufacture the titled stainless steel excellent in cold forgeability, electromagnetic properties, and corrosion resistance, by incorporating specific percentages of C, Si, Mn, S, Cr, Ti, N, and Al to Fe and by specifying the total amount of C and N. CONSTITUTION:A soft-magnetic stainless steel which has a composition consisting of, by weight ratio, <=0.015% C, 0.10-<0.40% Si, <=0.40% Mn, <=0.002% S, 11-13% Cr, 0.03-0.20% Ti, <=0.015% N, 0.30-0.80% Al, and the balance Fe with impurity elements and satisfying C+N=0.025% is prepared. In this way, the soft-magnetic stainless steel for cold forging having superior magnetic properties such as >=about 13,000G magnetic flux density and <=about 1.0Oe coercive force, also having superior electric properties such as >=about 65muOMEGA-cm electric resistance, and excellent in cold draft as to have <=about 40kgf/mm<2> tensile strength and >=about 60% critical draft can be obtained.

Description

[Detailed description of the invention] (Industrial application field) Regarding stainless steel.

(Prior art) Conventionally, the properties required for soft magnetic stainless steel include electrical properties such as magnetic flux density and coercive force, as well as electrical resistance and corrosion resistance.In order to obtain particularly excellent magnetic properties, 2Si
-13Cr steel, I Si-0,20Al -13Crt
M, etc. have been developed and some of them are in practical use.

In recent years, the development of applications for soft magnetic stainless steel has progressed, and it has come to be used for parts with complex shapes such as the body and core of electronic fuel injection devices. The development of steel was required.

For the above requirements, for example, I 5i-13Cr-0
, 2Al steel and other steels with C lucidity reduced to about 0.01% have been developed and are used in some areas.

(Problem to be solved) However, the tensile strength of these steels is 44.5.
kg f/mm m, reduction of area is 74%, limit processing rate is 4
It has been desired to develop a soft magnetic stainless steel having cold forgeability and electromagnetic properties better than 7%.

(Means for Solving the Problems) The present invention was made in view of the drawbacks of conventional steels, and the present inventors have investigated the effects of various alloying elements on the electromagnetic properties and cold forgeability of 13Cr steel. As a result of IIJ investigation of the effects, the magnetic properties were improved by adding Al and Ti and lowering the C and N content, and the electrical properties were significantly improved by the addition of 81, while cold forgeability was improved by adding Ti. It has been found that this can be improved by lowering C+N and S.

In particular, when the C+N content of Ti is a normal value of about 0.06%, the cold forgeability is hardly improved and the magnetic properties are only slightly improved. However, C+N Lucid is 0.025
% or less, the addition of about 0.05% of 'ri will result in the formation of precipitates that affect both magnetic properties and cold forgeability, which will reduce cold forgeability. However, the amount of C is 0.025%
If all the C+N is fixed with Ti, only harmless small TiC and TiN precipitates are formed, and only the interstitial solid solution strengthening effect of C+N disappears, resulting in cold forging. It is thought that the properties and magnetic properties will be significantly improved.

Based on these findings, the present invention has developed C+ in 13Cr steel.
The amount of N should be 0.025% or less and 0.30 to 0.
It contains 80% Al and 0.01 to 0.20% Ti, greatly improving electromagnetic properties, and 0.01% to 0.20% Ti.
Contains 30-0.80% Al to improve electrical properties,
Another 0.0? ~0.20% of Ti and 0.20% of C and 0.20% of Ti.
By setting the S content to 0.025% or less and 0.002% or less, cold forgeability is significantly improved.

Therefore, the steel of the present invention has a magnetic flux density (B
■), has excellent magnetic properties with a coercive force of 1.00e or less, and has excellent electrical properties with an electrical resistance of 65μΩ-1 or more, and has excellent cold workability and tensile strength of 40kg.
f/mm or less, and the limit processing rate is 60% or more.

That is, the steel of the present invention has a weight ratio of C of 0.015% or less, Si of 0.10 to less than 0.40%, and Mn of 0.40%.
% or less, ] S 0.002% or less, Cr 11-13%, Ti 0
．． Ot ~0.20%, N 0.015% or less, C+N
0.025% or less, Alo, 30 to 0.80%, and the remainder consists of Fe and impurity elements.
．． 30% or less, S 0.0/lo% or more, Ss 0.0
Contains one or more of 10% or less, and
When containing S and Se, Te0.002 to 0.0
40% and further contains S + Se + 'reO01
The fourth invention further improves the cold buildability of the second invention by adding Mo 2.5% to the first invention.
5% or less, Cu 0.5% or less, Ni 0.5% or less,
Contains 0.20% or less of Nb and 0.20% or less of V,
It further improves the corrosion resistance of the second invention by containing one or more of the following: 1st shot/lower, Ni 0.5% or less, Nb 0.20% or less, and V 0.20% or less. The sixth invention further includes Mo 2.5% or less, Cu 0.
5% or less, Ni005% or less, Nb0.20% or less, V
The corrosion resistance of the third invention is further improved by containing 51 or 2 or more kinds of 0.20% or less? This is what I did.

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

C is an element that deteriorates cold forgeability due to its solid solution strengthening effect and also has an adverse effect on magnetic properties. In the present invention, it is desirable to reduce it as much as possible, and the upper limit is set at 0.015%. In addition, in order to further improve cold forgeability and magnetic properties, it is desirable that the content is preferably 0.010% or less.

, Si changes magnetic properties such as magnetic flux density and coercive force, and
It is also an element that increases electrical resistance, with a lower limit of 0.
It was set at 10%.

However, does Si have a solid solution strengthening effect? It's rented space forging.

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

Although S is an element that improves machinability, it is also an element that impairs cold forgeability, and its upper limit was set at 0.002%. Cr is a basic element that imparts corrosion resistance to stainless steel, and must be contained in an amount of at least 11%.

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

Al is an element that improves magnetic properties and electrical resistance, and has a synergistic effect when combined with Si.
If the Al content exceeds 0.80%, the excellent cold forgeability of the present invention will deteriorate ((j), so the upper limit was set at 0.80%.

Ti significantly improves magnetic properties such as magnetic flux density and coercive force, and in the extremely low range where c+NB is 0.025% or less, Ti improves tensile strength and limits by fixing C+N into fine carbonitrides. It is an element that significantly improves cold forgeability such as processing rate, and is an essential element in the present invention.

To obtain these effects, at least 0. Oi% or more The lower limit was set at 0.01%.

In addition, to obtain better magnetic properties and cold forgeability, C+
The target amount should be three times that of Ni, and it is desirable to add 0.05% or more.

However, even if 0.20% or more of Ti is contained, the effect is 2.
Since the fruit becomes saturated, the upper limit was set at 0.20%.

°', -'N'N, like C, is an element that improves cold forgeability through solid solution strengthening action, and in the present invention, it can be used to further improve cold forgeability. is desirably 0.012% or less.

The purpose is to obtain excellent cold forgeability with a strength of 40 kg f/m or less and a limit workability of 60% or more, and it is necessary to reduce C+Nl as much as possible, with the upper limit being 0.025%. And so.

Bi-, Pb, S, Se, and Te are all elements that improve machinability.

However, when a large amount of Bi and Pb is contained, cold forgeability
Since hot workability is affected by Ba fl, the upper limit is set at 0.30 for each.
%.

In addition, when a large amount of sl is contained, the cold forgeability and corrosion resistance are
Therefore, the upper limit was set at 0.040%.

Furthermore, Te has the effect of neutralizing the effects of S and Se on cold forgeability, and must be contained in an amount of at least 0.02%. However, if a large amount is included,
On the contrary, it impairs cold forging properties, so the upper limit is set to 0.0/
It was set at 10%. In addition, if the Se content exceeds 0.040%, the corrosion resistance and cold forgeability will deteriorate by 1n, so the upper limit of Se is set at 0.040%.

Furthermore, the main objective of the present invention is to obtain excellent cold forgeability, and the total amount of S + Se + Te is set to 0.050%.

Zr is an element that makes MnS spheroidal and improves cold forgeability, and must be contained in an amount of at least 0.02%. However, if a large amount of Zr is contained, the amount of inclusions increases and cold forgeability is impaired, so the upper limit was set at 0.15%.

Mo, Cu, N1% Nb, ■ are elements that improve corrosion resistance.

However, ho is 2.5%, and Cu and Ni are each 0.5%.
'3 If A, Nb, and ■ exceed 0.20%, their magnetic properties and cold forgeability will change, so the upper limit is set at 2.5% for gate 0, and 0.2% for Cu and Ni. 5%, Nb,
■ was set at 0.20%.

(Example) Next, an example will be shown in which the characteristics of the steel of the present invention are compared with conventional steel.

In Table 1 below, steels A to l' are steels of the present invention, and steels U to W are conventional steels.

Table 2 shows the test steel in Table 1 at 900°CX211
The tensile strength, limit processing rate, magnetic flux density, coercive force, corrosion resistance, electrical resistance, and machinability of A-W steel, which is maintained at r and then subjected to heat blasting at a cooling rate of 100°C/11r, are evaluated. It is.

The tensile strength was measured using a JIS No. 4 test piece, and the limit workability was determined according to the standards of the cold forging subcommittee of the Japan Society of Plastic Technology, and the cold upsetting test method (tentative standard > f, W, ) of the test pieces.

Regarding the magnetic properties, a ring with an outer diameter of 24 φ, an inner diameter of 16 ψ, and a thickness of 16 mm was prepared as a test piece using a DC type Bll tracer, and the magnetic flux density and coercive force were measured.

Also, regarding corrosion resistance, use a solution of 5% NaCl at 35°C7 in salt water spray. The test was conducted and the completion rate was measured, and those with a completion rate of 5% or less were rated ◎, and those with a completion rate of over 5 to 25% were rated ○. The electrical resistance was determined by the Wheatstone method using 1.2φ×500 IJX as a test piece.

Regarding machinability, a test piece with a thickness of 1011 was used and
i! 1.725 r, p, m, drill 5KII 5φ,
A drilling test was conducted with a load of 4 kg, and the time required to drill the hole was measured.

As is known from Table 2 below, conventional steel U steel has excellent corrosion resistance, but has low magnetic properties with a magnetic flux density of 12,100G, and has a required T of 5.
By not containing i, the tensile strength is 47 kl f
/ mm, and the limit working rate was 44%, which is poor in cold forgeability, and also poor in electrical resistance and machinability.

In addition, steel has a low Al content of 0.20% and does not contain the necessary 1'i, so it has poor magnetic properties such as magnetic flux density.
It has poor electrical properties, poor cold forgeability with a tensile strength of 45 kg f/mm, and poor machinability due to the high Si content. Furthermore, regarding W steel,
The content of elements that deteriorate cold forgeability due to solid solution strengthening effects such as
% Ti, 0.30-0.80% Al, 11-13%
By containing Cr, the tensile strength is 40 kg.
It has excellent cold forgeability with a f/m% or less and a limit working rate of 60% or more, and its magnetic properties are excellent with a magnetic flux density of 13000c or more and a coercive force of 1.00e or less. In addition, corrosion resistance, electrical resistance, and machinability are also excellent, and by containing an appropriate amount of Ti and regulating the upper limit of Si and nn, magnetic properties are not impaired (cold forgeability is improved). and
Furthermore, the combined addition of S, Pb, and Zr improves cold forgeability (machinability is improved, and
This is a soft magnetic stainless steel for cold forging that is suitable for electronic fuel injection devices, etc., and has high practicality.

Claims (6)

[Claims] (1) C0.015% or less by weight, Si0.10
~Less than 0.40%, Mn 0.40% or less, S0.002
% or less, Cr11-13%, Ti0.03-0.20%
, N0.015% or less, C+N0.025% or less, Al
A soft magnetic stainless steel for cold forging, characterized in that it contains 0.30 to 0.80%, with the remainder consisting of Fe and impurity elements. (2) C0.015% or less by weight, Si0.10
- less than 0.40%, Mn 0.40% or less, Cr11-1
3%, Ti 0.03-0.20%, N 0.015% or less, C+N 0.025% or less, Al 0.30-0.80%
Contains 0.30% or less of Bi, and 0.30% of Pb.
Contains one or more of S0.040% or less and Se0.040% or less, and contains 1 or more of S, Se.
Te0.002 to 0.040 when containing more than one species
%, S+Se+Te 0.050% or less, and the remainder consists of Fe and impurity elements. (3) C0.015% or less by weight, Si0.10
- less than 0.40%, Mn 0.40% or less, Cr11-1
3%, Ti 0.03-0.20%, N 0.015% or less, C+N 0.025% or less, Al 0.30-0.80%
Contains 0.30% or less of Bi, and 0.30% of Pb.
Hereinafter, it contains one or more of S0.040% or less and Se0.040% or less, and when containing one or more of S and Se, it contains Zr0.02 to 0.15%, Furthermore, a soft magnetic stainless steel for cold forging characterized in that S+Se is 0.050% or less, and the balance is Fe and impurity elements. (4) C0.015% or less by weight, Si0.10
~Less than 0.40%, Mn 0.40% or less, S0.002
% or less, Cr11-13%, Ti0.03-0.20%
, N0.015% or less, C+N0.025% or less, Al
Contains 0.30 to 0.80%, and further contains Mo2.5% or less, Cu0.50% or less, Ni0.50% or less, Nb0
．． A soft magnetic stainless steel for cold forging, characterized in that it contains one or more of 20% or less and 0.20% or less of V, with the remainder consisting of Fe and impurity elements. (5) C0.015% or less by weight, Si0.10
- less than 0.40%, Mn 0.40% or less, Cr 11-13%, Ti 0.03-0.20%, N0.
015% or less, C+N 0.025% or less, Al 0.30
~0.80%, furthermore Bi0.30% or less, P
b0.30% or less, S0.040% or less, Se0.04
Contains one or more of 0% or less, and S
, if one or more types of Se are contained, Te0.002~
Contains 0.040% and further contains S+Se+Te0.05
0% or less, and Mo2.5% or less, Cu0.5% or less, Ni0.5% or less, Nb0.20% or less, V0.2
Contains one or more of 0% or less, the balance being Fe
Soft magnetic stainless steel for cold forging, characterized by comprising impurity elements. (6) C0.015% or less by weight, Si0.10
- less than 0.40%, Mn 0.40% or less, Cr 11-13%, Ti 0.03-0.20%, N0.
015% or less, C+N 0.025% or less, Al 0.30
~0.80%, furthermore Bi0.30% or less, P
b0.30% or less, S0.040% or less, Se0.04
Contains one or more of 0% or less, and S
, if one or more types of Se are contained, Te0.002~
0.040%, one type of Zr0.02 to 0.15, further S + Se + Te 0.050% or less, Mo 2.5% or less, Cu 0.5% or less, Ni 0.5% or less, Nb 0.20% Below, V0.
Contains one or more of 20% or less, the remainder being F
A soft magnetic stainless steel for cold forging characterized by comprising e and impurity elements.