JPS5844725B2 - Manufacturing method of non-magnetic steel wire and steel bar - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing non-magnetic steel wire and steel rod,
The purpose of the present invention is to provide a new method for manufacturing non-magnetic steel wires and bars that have particularly high strength, excellent magnetic properties, good dimensional accuracy, and smooth surface texture.

Non-magnetic steel is steel that has extremely low magnetic permeability (μ) and does not become magnetized even when placed in a strong magnetic field.

This type of steel has traditionally been used in some electromagnetic equipment, but recently it has been used in equipment that makes even the slightest magnetic change a problem, such as geomagnetic observation equipment, and in fusion experimental equipment. Non-magnetic steel is also being used as a structural material for equipment and the like where the influence of induced magnetic fields caused by large currents is a concern.

Furthermore, many parts of electromagnetic equipment, machines and other shell structural parts are required to be non-magnetic.

Non-magnetic steel used for the above applications is required not only to have low magnetic permeability (P), but also to have sufficiently high strength and low cost.

Furthermore, when used for PC steel bars, steel wires, springs, bolts, etc., it is necessary to have excellent luxation resistance, and for special non-magnetic electrical parts, machinery and other structural parts, Steel bars with round, square, hexagonal, flat, etc. cross-sectional shapes with excellent dimensional accuracy are required.

Steel bars for such parts are often manufactured by machining, and therefore, it is desired that the steel bars have excellent machinability such as cutting and drilling.

SUS has traditionally been widely used as a non-magnetic steel.
It is an austenitic steel represented by 304.

However, SUS 304 series steel is not only expensive because it contains large amounts of Cr and Ni, but also has a yield strength of 30k.
gf/- is low inside and outside.

Austenitic steel cannot be strengthened by heat treatment such as quenching, so cold working is the only way to increase its strength. However, in 5US304 steel, the magnetic permeability increases with cold working, making it unsuitable as a non-magnetic steel. It becomes something.

Furthermore, conventional austenitic steel has a very high relaxation rate and is not suitable for use in PC steel bars, springs, bolts, etc.

Furthermore, Ni-Cr austenitic steel has poor descaling properties and difficulty in forming a lubricating film, and therefore cannot be subjected to high-performance cold wire drawing or cold drawing.

In view of the above-mentioned current situation, the present inventors have proposed that Mn5 to 30
% and has a composition of ±-"(C)+2(Mn)≧25c%), as well as its hot working conditions. 5
No. 2-150721), No. 51-68312 (No. 52
-150720), No. 51-68313 (No. 52-
No. 150722).

The above-mentioned non-magnetic steel has low magnetic permeability and is inexpensive, and depending on the composition adjustment and the combination of hot working and cooling conditions, it has high strength even after hot working, and is superior to conventional N
It has many excellent properties not found in i-Cr austenitic steel.

The present invention was made as a result of subsequent research on this 5-30% Mn-based nonmagnetic steel. This makes it possible to manufacture non-magnetic steel wire and steel bars that have extremely high strength and resistance to luxation while maintaining strong non-magnetic properties.

The present invention is characterized by containing 1.5% or less of C, 0.1-1.5% of Si, 5-3% of Mn, and 15% or less of N0 (C-1-N).
The gist of the present invention is a method for manufacturing non-magnetic steel, which is characterized in that steel with +2Mn≧25% is processed by 90% or less in a temperature range of 600°C or less.

First, the composition of the steel that is the object of the present invention is C1.5%.
Hereinafter, 0.1 to 1.5% of Si and 5 to 30% of Mn are essential components.

C contributes to stabilizing the austenite structure of steel and is an essential component for improving strength.

However, when it exceeds 1.5%, carbide precipitation increases at grain boundaries and the steel becomes brittle.

Si is essential to contain 0.1% or more as a deoxidizing agent,
If more than this amount is present, it also contributes to raising the yield point of steel.

However, if the content exceeds 1.5%, problems arise in making it stably non-magnetic.

Mn is the main component that austenitizes steel and makes it non-magnetic.

Not only is Mn significantly cheaper than Ni, but Mn austenitic steel is
r It has various excellent properties not found in austenitic steel.

5% is the lower limit at which such an effect can be expected, and 30
% is an upper limit value that does not cause problems in steel manufacturing.

N (nitrogen) is also a component that stabilizes the austenite phase of steel.

N is unavoidably mixed in to about 0.005% in normal atmospheric melting, but in the non-magnetic steel of the present invention,
It is sometimes actively added to stabilize the austenite phase and improve strength.

That is, NO, 5% or less as used in the present invention means both cases in which N is actively added and cases in which it is not.

When N is actively added, other austenite stabilizing components can be reduced, and for example, workability can be improved by lowering C and cost can be reduced by lowering Mn.

However, if the amount of N exceeds 0.5%, notifications such as the formation of bubbles in the steel will occur.

00 Between the contents of C-N and Mn, T(C+N)+2
It is important to ensure the relationship (Mn≧25c%).

When this relationship is satisfied, the austenite phase of the steel is stable and μ≦1 even when subjected to severe cold working as described below.
02 non-magnetism can be ensured.

In addition to the above four components, the target steel of the present invention may contain the following components.

The first group elements Cu 5% or less, Ni 5% or less, and Cr 9% or less are effective components for stabilizing the austenite phase.

The upper limit of Cu is set to 5%, and the upper limit of Ni is set to 5% mainly from the viewpoint of cost.

In addition, addition of 1.0% or more of Cr prevents the occurrence of cracking during heating of the ingot and the embrittlement of hot rolled products by preventing the precipitation of carbides at grain boundaries and embrittlement of the steel. It is also effective for

00 When adding Cu and Ni, -A (C+N)
It is necessary to adjust each component so that +2(Mn+Cu+2Ni)≧25c%).

Group 2 elements P, V, Nb, Ti, Zr, W, AA: These components are added to increase the yield strength of the nonmagnetic steel of the present invention.

When higher yield strength is required, such as in high-tensile reinforcing bars, bolts, and bottles, the addition of the above-mentioned components can improve yield strength without adversely affecting nonmagnetism.

P strengthens the base by solid solution strengthening and increases the yield strength, but this effect becomes obvious at a content of 0.05% or more.

However, if it exceeds 0.5%, the embrittlement of the steel becomes severe.

V, Nb, 'ri, Zr, W and AA refine the grains of steel and contribute to increasing the yield strength.

Carbides, nitrides, etc. of V, Nb, Ti, Zr, and W precipitate during hot working or during aging treatment after solution treatment, and exhibit a remarkable strengthening effect.

Such an effect is shown in ■, from 0.01% in the case of Nb to T
In the case of i, Zr, and W, it becomes clear from 0.05%,
The higher the content, the greater the effect.

However, if it exceeds 4% in any case, the austenite structure of the matrix becomes unstable, making it difficult to obtain the properties of non-magnetic steel.

The crystal grain refining effect of Al becomes noticeable from 0.02%.

However, since Al is also a ferrite stabilizing element, adding a large amount of Al destabilizes the austenite phase.

Therefore, this content is preferably up to 1%.

Group 3 elements S, Pb, Se, Te These are components that improve the machinability of non-magnetic steel.

These components can be used alone or in combination of two or more, but the content needs to be selected as shown below.

S: When 0.05% or more of S is added, cutting with high-speed steel becomes possible in turning and milling, and tool life is extended as the S content increases.

In carbide tools, the tool life is significantly extended as the amount of S increases.

When the S content exceeds 1%, the steel becomes brittle and the elongation area decreases.
Cracks are more likely to occur during hot working.

Pb: Adding Pb greatly improves workability in turning, milling, and drilling.

The effect of improving tool life in turning and milling is significant, but especially in drilling, it becomes possible to drill with a carbide drill what conventional steel cannot be drilled with a carbide drill.

The effect is weak unless the amount of Pb is added at 0.05% or more.
Processability improves as the amount of Pb increases.

If the amount of Pb exceeds 1%, the elongation reduction decreases, which is not preferable.

Se: Se shows the same effect as S, 0.0
The effect is recognized at 5% or more.

The amount added is preferably 1.0% or less from the viewpoint of reducing ductility.

Te: When Te is added in an amount of 0.01% or more, drilling with a drill made of carbide becomes possible, and chip breakability during turning is improved.

If the amount added exceeds 0.5%, the tensile strength will decrease, and the elongation and area of area will decrease accordingly, so the upper limit should be set to 0.
．． It was set at 5%.

Steel containing or not containing one or more of the elements of Groups 1 to 3 as described above is subjected to warm and/or cold working at a working rate of up to 90% at 600°C or less. Add.

Of course, the steel with the above composition has excellent properties not found in conventional non-magnetic steel even when subjected to normal hot rolling.
Strength can be improved by a processing method such as that proposed in No. 168313 (Japanese Unexamined Patent Publication No. 52-150722).

However, the present inventor has found that regardless of the hot working method, by performing warm working or cold working at 600°C or less, or a combination thereof, the strength can be further improved significantly. Contrary to the conventional wisdom regarding non-magnetic steel, it was confirmed that the magnetic permeability (D) hardly increases even after such processing.

Processing may be of any type, such as rolling, drawing, wire drawing, forging, etc.

However, the working temperature must be below the temperature at which recrystallization begins, that is, 600° C. for the steel targeted by the present invention.

Even if processed at a temperature higher than this temperature, the strength cannot be improved to the intended extent.

The processing rate may be appropriately selected up to 90% depending on the desired strength level and the size of the material and product, and even a small amount of processing can achieve a corresponding improvement in strength.

When cold processing is performed, products with beautiful surface texture and excellent dimensional accuracy can be obtained.

There is a limit to the processing rate in one cold processing, and processing exceeding 30% requires two or more passes, warm processing, or a combination of warm and cold processing. .

The total amount of processing should be limited to 90%; adding processing exceeding this will result in significant deterioration of ductility.

Note that if the total amount of processing is less than 10%, the effect of processing will not reach the center of the steel material, which may cause non-uniformity in the structural strength and residual stress, so it is desirable that the processing rate be 10% or more.

Lubricity is very important when cold working.

Stainless steel such as SUS 304 has very poor descaling properties and cannot be descaled by ordinary pickling treatment.

In addition, it is necessary to apply a coating to the surface of the steel in order to transport the lubricant to the steel surface and prevent the tool from seizing the skin of the steel, but a normal phosphate coating is not possible with 5US304, etc. However, it is unavoidable to create a film using oxalate, or to create a film by applying a resin.

These coatings have low strength and poor lubrication, resulting in problems such as seizure, local increases in magnetic permeability, and impossibility of cold working.

In the case of the present invention, since the steel has a high C and Mn content and a low Cr content, it not only has extremely excellent descaling properties, but also can form a strong phosphate film with excellent lubricity. , the oxalate film is also much stronger than before.

The effects of the present invention are largely due to this remarkable improvement in lubricity.

Heat treatment after processing is not essential.

In particular, when cold working is used to produce products with good surface texture and high dimensional accuracy, it is best to use them as they are processed.

However, when emphasis is placed on strength and luxation resistance,
It is desirable to perform annealing at 200 to 700°C after processing.

In particular, when the above-mentioned components of the second group are included, precipitation hardening occurs due to this annealing, resulting in a further increase in strength.

Example Table 1 shows the chemical composition of the samples.

The sample is a hot-rolled wire rod of 20 mvtφ.

Table 2 shows examples of manufacturing conditions according to the manufacturing method of the present invention.

Table 3 shows the mechanical properties, relaxation rate, and magnetic permeability of each sample produced by the method of the present invention as shown in Table 2.

Regarding the test method, the tensile test was performed using a JI No. 89 test piece.
It was conducted in accordance with JIS Z2241.

The magnetic permeability was measured using a magnetic balance using a sample taken from the center of the produced steel wire in a magnetic field with a magnetic field strength of 2000 oersted.

The relaxation rate was determined by using an automatically controlled ram type relaxation tester at initial stress = yield strength Xo, 8, test temperature -20℃±0.5℃, test time -10hr
Measured in accordance with ISZ2276.

As seen in Table 3, the permeability is 1.0 in the normal method.
Non-magnetic properties of 2 or less are limited to cases where the solution treatment is performed as is.

In this case, the yield strength is 28.7 kgf/mff1
L is not suitable for use as a high-strength member.

Moreover, relaxation is extremely high at 15.6%.

When cold worked, the strength increases considerably, but the magnetic permeability increases significantly, reaching 1.34 after 20.8% cold working, making it no longer suitable for use as a nonmagnetic material.

The production method of the present invention has a much higher hardenability than the usual case, and has a much higher strength even with the same degree of processing.

A tensile strength of 150 kgf/- was reached after 50% processing, and the low yield strength, which was a drawback of austenitic steel, was significantly improved.

Despite its extremely high strength, its magnetic permeability is extremely low and it maintains the characteristics of a completely non-magnetic material.

In addition, its extremely high yield strength greatly expands its applicability to components that require high strength, and the high yield strength also allows it to be used easily even though it is subjected to extremely high initial stress. The sales rate is around 5%, which is an excellent value.

When warm working is added, the yield strength increases significantly, and relaxation properties are further improved.

Subsequent cold working improves the surface finish, improves dimensional accuracy, and increases strength.

The magnetic permeability is always stable at a value of 1.02 or less.

Claims (1)

[Claims] I C1.5% or less, Si0.1-1.5%, Mn5
~00 Contains 30%, NO, 5% or less (C+N)
)-1+2Mn≧25c%) A method for manufacturing non-magnetic steel wires and steel bars, characterized by subjecting steel with 90% or less processing in a temperature range of 600° C. or less. 2C1, 5% or less, SiO, 1-1.5%, Mn 5-3
0%, NO, 5% or less, further containing one or more of Cu5% or less, Ni5% or less, Cr9% or less,
)+2 (Mn+Cu+2Ni)≧25C%) A method for manufacturing non-magnetic steel wires and steel bars, characterized by subjecting steel to 90% or less processing in a temperature range of 600° C. or less. 3 The material steel is further Po, 05~0.5%, Vo, 01~
4%, Nb0.01-4%, Ti 0.05-4%, Z
r0.05~4%, Wo, 05~4%, A#0.02~
The method for manufacturing non-magnetic steel wires and steel bars according to claim 1 or 2, which contains one or more of 1% or more. 4 The material steel further contains 80.05 to 1.0%, PbO,
05-1.0%, Se O, 05-1.0%, Te 0
．． The method for manufacturing non-magnetic steel wires and steel bars according to claim 1, 2 or 3, which contains one or more of 01 to 0.5%.