JPH06116683A - High mn nonmagnetic steel excellent in machinability and corrosion resistance - Google Patents

Abstract

PURPOSE:To produce high Mn nonmagnetic steel having excellent machinability and corrosion resistance as well as strength and magnetic properties by specifying its chemical compsn., Ni equivalent and Cr equivalent. CONSTITUTION:In the high Mn nonmagnetic steel, each element of C, Mn, Ni, Cr, Mo, N, S and Al is specified as well as the Ni equivalent [=Ni%+30X(C%+N%)+0.5XMn%] is regulated to <=16 and the Cr equivalent (=Cr%+Mo%+1-5XSi%) is regulated to <=24, and furthermore, 0.01 to 0.13% In is incorporated therein. In this way, while excellent strength properties and magnetic properties of the high Mn nonmagnetic steel are maintained and without exerting a bad influence upon its corrosion resistance, its machinability is improved. Thus, the high Mn nonmagnetic steel excellent in all of strength, magnetic properties, corrosion resistance and machinability can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a high Mn non-magnetic property which has corrosion resistance comparable to that of stainless steel, has strength and stable magnetic properties superior to those of stainless steel, and has improved workability, especially machinability. It is about steel.

[0002]

2. Description of the Related Art In recent years, along with the development of magnetic utilization technology, the range of application of non-magnetic steel has been increasing. In particular, VT in the field of light electrical technology, which has developed significantly in recent years
The use of non-magnetic steel is rapidly increasing in precision machine parts such as R, audio equipment, office equipment, and other electronic equipment that need to avoid magnetism.

As such a non-magnetic steel, SU has been conventionally used.
Austenitic stainless steels such as S304 and 316 have been used, but these stainless steels are insufficient in strength in addition to the drawback that the magnetic permeability increases to 1.5 times or more by cold working. Therefore, the use ratio of high-Mn non-magnetic steel, which has corrosion resistance comparable to that of austenitic stainless steel and has high strength and stable non-magnetism, has recently been increasing.

[0004]

However, the high Mn non-magnetic steel has very poor machinability as compared with ordinary carbon steel and stainless steel, and a method of adding S, Pb or the like to improve the machinability. However, this method has a drawback that the corrosion resistance becomes extremely poor.

The present invention has been made in view of the above circumstances, and its purpose is to provide strength and stable magnetic characteristics higher than those of austenitic stainless steel, and also excellent in corrosion resistance and machinability. It is intended to provide a high Mn non-magnetic steel exhibiting excellent performance.

[0006]

The high Mn non-magnetic steel according to the present invention, which has been able to solve the above problems, has a C: 0.0.
5 to 0.2% (weight%: same below), Mn: 5 to 23
%, Ni: 15% or less, Cr: 13 to 22%, Mo: 5
% Or less, In: 0.01 to 0.13%, N: 0.15 to
0.6%, S: 0.02% or less, Al: 0.03% or less,

The balance is Fe and unavoidable impurities, and the Ni equivalent calculated by the following formula is 16 or less, Cr.
The gist is that the equivalent weight is 24 or less. Ni equivalent = Ni% + 30 × (C% + N%) + 0.5 × M
n% Cr equivalent = Cr% + Mo% + 1.5 × Si%

[0008]

[Operation] S, Pb, B has long been used as a machinability improving element.
It has been confirmed that i and the like have excellent effects. However, since all of these machinability improving elements are present as inclusions in the steel, adding them to the high Mn nonmagnetic steel significantly impairs corrosion resistance and hot workability.

However, as a result of various researches conducted by the present inventors, as will be described in detail below, the composition of the high Mn non-magnetic steel and the N content of N are shown.
The machinability of a high Mn non-magnetic steel is remarkably improved by determining the i equivalent and Cr equivalent, and especially by including a small amount of In in the steel, and most of In is in austenite. Since it does not form a solid solution and precipitates as inclusions, it does not adversely affect the corrosion resistance. Furthermore, if the In content is within a certain limit, machinability improving elements such as S, Pb and Bi were added. The present invention has been completed based on the new finding that hot workability, which is sometimes observed, does not deteriorate. Hereinafter, the reasons for defining the component composition in the present invention will be described in detail.

C: 0.05% to 0.2% C is an element that is indispensable for ensuring non-magnetic properties and strength, and must be contained in an amount of 0.05% or more to achieve the purpose. . However, if too large, the machinability deteriorates, so it is necessary to suppress it to 0.2% or less. Mn: 5 to 23% Mn is an austenite forming element, and if it is less than 5%, its effect is not effectively exhibited. However, if the content exceeds 23%, the hot workability is significantly deteriorated.

Ni: 15% or less Ni not only acts as an austenite-forming element, but also acts to enhance corrosion resistance, so it is better to have a large content, but the effect saturates at about 15%, so 15% is added. It is economically useless to add a large amount beyond. The N
The lower limit of the i content is most practically determined by considering the contents of C, N and Mn, which have the same effect as Ni, in consideration of the contents of C, N and Mn. With the above, the above effects are effectively exhibited. Ni equivalent = Ni% + 30 × (C% + N%) + 0.5 × M
n%

Cr: 13-22% Cr is an important element for improving the corrosion resistance, and 1
If it is less than 3%, the effect is not sufficiently exhibited. But 2
If it exceeds 2%, not only the non-magnetism becomes unstable, but also the hot workability becomes poor. The upper limit of the Cr content is Cr
Similarly, the contents of Mo and Si, which adversely affect the hot workability, are also taken into consideration, and it is preferable to determine the Cr equivalent represented by the following equation. To prevent the deterioration of the hot workability, the Cr equivalent is 24 It is necessary to keep below. Cr equivalent = Cr% + Mo% + 1.5 × Si%

N: 0.15 to 0.6% N is an essential element for forming austenite and improving strength and corrosion resistance, and its content is 0.15.
If it is less than%, these effects cannot be effectively exhibited. However, if it is too large, bubbles will be generated in the steel ingot and the hot workability will be deteriorated, so it must be suppressed to 0.6% or less. Mo: 5% or less Mo is an element that improves the corrosion resistance and strength, and the larger the amount, the more preferable. However, the effect is saturated at about 5%, and no further effect is obtained, which is economically wasteful.

S: 0.02% or less S exists as MnS inclusions in steel and contributes to improvement of machinability, but if it exceeds 0.02%, corrosion resistance is significantly deteriorated. Al: 0.03% or less Al is an element necessary as a deoxidizing agent, but if it is contained in excess of 0.03%, a C-based inclusion is generated to deteriorate the corrosion resistance. Therefore, the Al content is 0.03% or less.

In: 0.01 to 0.13% In has a peculiar function and effect of increasing machinability without adversely affecting the corrosion resistance as described above, and in order to effectively exhibit such a function. Must be contained in an amount of 0.01% or more. However, if the content is too large, the hot workability tends to be remarkably deteriorated, so 0.13% is set as the upper limit at which such adverse effects are not substantially manifested.

The present invention is constructed as described above and has a high M
n Non-magnetic steel composition, especially C, Mn, N, Mo, S,
While specifying the content of Al, etc., Ni equivalent and Cr
By specifying the equivalent weight and containing a small amount of In, the machinability and corrosion resistance can be remarkably enhanced while maintaining the stable non-magnetic property and high strength which are the original properties of high Mn non-magnetic steel. Therefore, it is possible to provide an ideal high Mn non-magnetic steel satisfying all the required properties of corrosion resistance, strength, non-magnetic property and machinability.

Next, examples of the present invention will be shown. However, the present invention is not limited by the following examples, and
Any appropriate modification and implementation within a range that is compatible with the spirit of the preceding and following statements is included in the technical scope of the present invention.

[0018]

EXAMPLES 15 high Mn non-magnetic steels having the composition shown in Table 1 were used.
It is melted in a 0 kg high frequency furnace, cast and then forged to a diameter of 25 mm or a diameter of 80 mm and then subjected to a solution treatment to give a diameter of 25 mm.
The forged material having a diameter of 80 mm was subjected to a corrosion resistance test, a room temperature tensile test and a high temperature tensile test after processing the test piece, and the forged material having a diameter of 80 mm was subjected to a cutting test. The test results are shown in Table 2. The test conditions are as follows.

(Tensile test): JIS No. 4 test piece, test temperature 25 ° C. (corrosion resistance test): 5% salt spray after 2000 hours, red rust occurrence rate (%) (Machinability test): Carbide life: Tool; P10 , V = 150 m / min, f =
0.2 mm / rev, d = 1.0 mm, dry cutting, life standard; VB = 0.2 mm Drill life: Tool; 10 mm diameter drill (SHK51 +
TiN), V = 20 m / min, f = 1.0 mm / re
v, dry cutting, life standard; melting loss (high temperature drawing test): test temperature 1100 ° C, pulling speed 2m
m / sec, test atmosphere (vacuum → Ar substitution)

[0020]

[Table 1]

[0021]

[Table 2]

From Tables 1 and 2, the following can be considered. The symbol A is the conventional high Mn non-magnetic steel (P
CD18), the tensile properties and corrosion resistance at room temperature and high temperature are good, but the machinability is extremely poor. The symbols B, C and D are S and P as machinability improving elements.
It contains b or Bi in an appropriate amount, and has a significantly improved machinability compared to the code A. However, the S-added steel with the code B is significantly deteriorated in corrosion resistance, and the Pb-added steel with the code C and the Bi-added steel with the code D are poor in corrosion resistance, and particularly the tensile properties are significantly deteriorated under high temperature conditions.

On the other hand, an appropriate amount of I as a machinability improving element is used.
The high Mn non-magnetic steel of the present invention containing n (reference numerals E to I)
Has excellent properties in tensile properties at room temperature and high temperature, corrosion resistance, and machinability. Incidentally, the symbol J is a comparative example in which the added amount of In is too large, and although the machinability is enhanced, the tensile properties at room temperature and high temperature are deteriorated and the corrosion resistance is also deteriorated.

Further, FIG. 1 is a graph showing the results of the corrosion resistance test of the reference materials A, B, C, D and I among the test materials shown in Table 1 above, in which an appropriate amount of In is added. The invention steel (symbol I) does not show any deterioration in corrosion resistance like the comparative steels (symbols B, C, D) to which S, Pb and Bi are added as machinability improving elements, and is the base steel (symbol A). It can be seen that it has excellent corrosion resistance equivalent to.

FIG. 2 is a graph showing the relationship between the In content and the aperture value at high temperature. The In content is 0.13%.
Although no extreme decrease is observed to some extent, if it exceeds 0.13%, the high temperature reduction value tends to decrease extremely.

Further, FIGS. 3 and 4 are graphs showing the influence of the In content on the life of the cemented carbide tool and the life of the drill, and the lifespan of these increases substantially linearly until the In content reaches about 0.13%. However, it can be seen that when the In content is 0.13%, the life extension effect reaches a saturated state, and no further significant improvement can be expected.

[0027]

The present invention is constituted as described above, and the composition of the steel material defines the Ni equivalent and Cr equivalent, and
In particular, by containing an appropriate amount of In, the machinability can be remarkably improved without adversely affecting the corrosion resistance and the tensile properties, which results in excellent corrosion resistance, strength properties and non-magnetism and machinability. It has become possible to provide a good high Mn non-magnetic steel.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a salt water spraying time and a rust occurrence rate of a test steel used in Examples.

FIG. 2 is a graph showing the influence of the In content on the high-temperature drawing value.

FIG. 3 is a graph showing the effect of In content on the life of cemented carbide tools.

FIG. 4 is a graph showing the effect of In content on drill life.

Claims (1)

[Claims] 1. C: 0.05 to 0.2% (weight%: the same applies hereinafter), Mn: 5 to 23%, Ni: 15% or less, Cr: 13 to 22%, Mo: 5% or less, In : 0.01 to 0.13%, N: 0.15 to 0.6%, S: 0.02% or less, Al: 0.03% or less, balance Fe and unavoidable impurities, and calculated by the following formula. A high Mn nonmagnetic steel excellent in machinability and corrosion resistance, characterized in that the Ni equivalent is 16 or less and the Cr equivalent is 24 or less. Ni equivalent = Ni% + 30 × (C% + N%) + 0.5 × M
n% Cr equivalent = Cr% + Mo% + 1.5 × Si%