JPS6184324A - Manufacture of nonmagnetic steel wire - Google Patents

Abstract

PURPOSE:To manufacture a high-strength high-Mn nonmagnetic steel wire at a low cost by hot rolling a steel contg. specified percentages of C, Si, Mn, Ni, Cr and N under specified conditions and by cold drawing the resulting wire rod. CONSTITUTION:A steel consisting of, by weight, 0.01-0.50% C, <=1.0% Si, 10-25% Mn, 0.1-5% Ni, 10-20% Cr, 0.01-0.5% N and the balance Fe with inevitable impurities or further contg. one or more among 0.005-0.30% Se, 0.005-0.30% Te, 0.05-0.20% Pb, 0.0005-0.02% Ca and 0.03-0.15% S is hot rolled at >=70% reduction of area, 900-1,000 deg.C coiling temp. and >=5 deg.C/sec cooling rate after coiling. The resulting wire rod is directly cold drawing at >=55% reduction of area without carrying out soln. heat treatment. A nonmagnetic steel wire having high strength such as >=180kg/mm<2> tensile strength and superior corrosion resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides high Mn materials for use as parts of communication devices, audio products, computer-related equipment, and precision electronic equipment.
The present invention relates to a method of manufacturing non-magnetic steel wire.

(Prior Art) In recent years, the field of electrical and electronic equipment, such as double-barrel wires, has made remarkable progress, and with this, so-called non-magnetic steel, which has low magnetic permeability and does not feel magnetic, has become popular as a structural material. It has come to be used in large quantities for many purposes such as bolts, nuts, springs, and shafts.

Generally, austenitic steel is often used as the non-magnetic H material for such applications due to its low magnetic permeability.

By the way, in order to obtain an austenite I structure that is stable at room temperature, it is necessary to add relatively large amounts of two or three of Ni, Cr and Mn. A typical example thereof is austenitic stainless steel such as S II S 304.5 US316. Furthermore, in recent years, development of non-magnetic steel, which is a high Mn-based austenitic steel that uses a large amount of Mn instead of expensive Ni, has been actively conducted.

These austenitic stainless steels or high Mn
Non-magnetic steel, which is a type of steel, is used for thick plates, tubes, and long steel, but it is also used in a considerable amount in the form of wire + A. In that case, the wire i, lGj is rarely used as hot-rolled, and in many cases, after softening heat treatment, cold processing such as cold wire drawing, cold rolling, and cold heading, and surface cutting, drilling, and grooves are performed. It is subjected to cutting pressure such as cutting to become the final product.

When these processes are carried out, the stability of the austenite silk weave of the austenite 1 series stainless steel mentioned above becomes a problem (1).
N-type austenitic steel has high austenitic silk weave stability but poor corrosion resistance. In addition, all of these steels are generally poor in cold working (71), and secondly, there are limitations in securing strength due to wire drawing. In addition, the conventional manufacturing method /J: does not take special consideration and therefore requires a softening heat treatment during heating, so it is not preferable from the viewpoint of energy saving.

In this way, non-magnetic steel used in precision electronic devices and their parts as described above is desired to have high strength, wear resistance, good corrosion resistance, and low cost. A material that satisfies all of the above has not yet appeared.

(Problems to be Solved by the Invention) Therefore, in order to improve the problems and drawbacks of conventional steels, the present inventors focused on the inherent characteristics of Mn-Cr-N-based austenitic steel, and achieved stable non-contamination. Magnetism and processability,
We have conducted a basic thorough examination of the component system that can provide even better corrosion resistance, and as a result, we have found that high Mn is required to achieve this objective.
It has been found that the system is advantageous, and that by adjusting the contents of Crt-, old, and N, the desired purpose can be achieved in combination with these. Furthermore, the present inventors have learned that even more irregular properties can be obtained by making the crystal grains finer in terms of metallographic structure, and that controlled rolling is advantageous for this purpose. I summarized the contents and filed a patent application (Japanese Patent Application No. 159022/1982).

The present inventors further continued research and development to improve the prior invention as described above, and found that the solution treatment process prior to cold wire drawing, which had been considered indispensable in the past, was omitted, resulting in a high M
Even though it is an n-type steel wire, by directly cold drawing the hot rolled material, i! 7, and completed the present invention.

As is already known to those skilled in the art, high Mn austenitic steels generally have very poor cold workability and are said to be difficult to wire-draw. However, the manufacturing cost was high, and the strength of the final wire rod was not necessarily satisfactory.

(Means for Solving the Problems) Thus, the present invention focuses on the characteristics of the hot-rolled material having the above-mentioned composition and obtained by the above-mentioned method. In fact, by omitting the solution treatment prior to cold wire drawing, the strength is unexpectedly improved.

Here, the characteristics of the present invention are as follows: C: 0.01 to 0.50%, Si: 1.0% or less, Mn = 10 to 25%, Old: o, i - 5% ,Cr
: 10~20%, N: 0.01~0.5%,
Including ¥1, and if necessary, Se: 0.005-0.30%, Te: 0.0
05-0.30%, Pb: 0.05-0.20%,
Ca: 0.0005-0.02% and S:
Steel containing one or more of 0.03 to 0.15% and having a composition consisting of Fe and unavoidable impurities is rolled at an area reduction of 70% or more and a rolling temperature of 900 to 1000°C. It is characterized by hot rolling under conditions of a subsequent cooling rate of 5°C/sec or more, and then directly cold drawing the obtained wire without solution treatment at an area reduction rate of 55% or more. This is a method for producing a non-magnetic steel wire with high tensile strength of 180 kg/mf% or more and excellent corrosion resistance.

(Function) Here, the reason why the steel composition and rolling conditions are limited as described above in the present invention will be described.

C (Carbon) C is an element that stabilizes austenite and at the same time contributes to solid solution strengthening, and must be contained in an amount of 0.01% or more. On the other hand, if it exceeds 0.50%, a large amount of carbides will precipitate at the austenite grain boundaries, which will deteriorate the ductility of the wire and lead to a decrease in cold workability and corrosion resistance. Therefore, in the present invention, the C content is set to 0.01
It was limited to ~0.50%.

Si (Silicon) Si is normally added to molten steel as a deoxidizing agent during refining, but even if it is added in excess of 1.0%, its deoxidizing effect will be adversely affected. Rather, the number of nonmetallic inclusions increases and the cleanliness of C steel deteriorates, so the upper limit is set to 1.
It was set as 0%.

Mn (Manganese) Mn has the effect of stabilizing the austerite silk weave at a low cost, and is an element necessary to make the steel non-magnetic.

For that purpose, is it necessary to contain 10% or more?
- On the other hand, if it exceeds 25%, stress corrosion cracking may occur, so in the present invention, the Mn content is set at 10 to 25%.

A more desirable range for satisfying both non-magnetism and corrosion resistance is 15 to 20%.

(Ni) Ni is an effective element for stabilizing the austenite structure and improving corrosion resistance.
It is necessary to add 1% or more. However, if it exceeds 5%, it is not only excessive for stabilizing the austenite structure, but also causes an increase in cost, which is undesirable. Therefore, in the present invention, the upper limit of the Ni content is set at 5%.

Preferably it is 1.0 to 3.0%.

Cr (Chromium) Cr has the effect of significantly stabilizing the austenite structure of steel containing Mn-Ni and increasing the degree of work hardening by reducing stacking fault energy. In addition to these effects, to improve corrosion resistance, 10% or more
Containment is necessary. However, when it exceeds 20%, no further improvement in the above effect is observed, and instead of the inverted L austenite structure, a δ ferrite structure is generated, and the magnetic permeability μ is reduced.
As a result, the non-magnetic properties are damaged. Therefore, in the present invention, the Cr content is set at 10 to 20%. More preferably, the Cr content is 13-17%.

N (Nitrogen) Like C, N is an element that stabilizes the austenite structure and at the same time contributes to solid solution strengthening. N also has the effect of improving stress corrosion cracking resistance, and for this purpose it is necessary to contain it in an amount of 0.01% or more. As a result, Ausnana 41~
It is also possible to avoid multiple additions of expensive elements such as Ni for the purpose of stabilizing the structure, sprinkling corrosion resistance, etc. On the other hand, N is 0
．． It is extremely difficult to melt steel that exceeds 5%.
Moreover, such high N steel is undesirable because it may cause defects due to I-balls in the cast steel ingot. Therefore, the N content was determined to be 0.01 to (), 5%.

One or two of Se, 1'e, , I'l+, Ca, and S: Se, Te, , I'b, Ca, and S are each effective elements for improving the +ll of the material. In order to improve machinability, Se: 0.005% or more, Te
: 0.005% or more”2, pb:
0°05% or more, Ca: 0.0005% or more, S
: 0.03% or more is required. On the other hand, if each element is added in large amounts, it promotes anisotropy in the mechanical properties of steel, and Te, for example, also deteriorates hot workability. Se
: 0.30%, Te: 0.30%, Pb: 0
．． 20%, Ca: 0°02%, and S:O, 15%. S is particularly effective in improving the machinability of steel. Of course, high Mn non-magnetic steel has a high cutting temperature and requires a heat-resistant tool for cutting, but by adding S, the cutting temperature can be lowered, improving machinability. This is because it greatly contributes to However, when added in large amounts, mechanical properties and corrosion resistance deteriorate. Its upper limit is 0.15% as mentioned above.

On the other hand, the degree of working (area reduction rate) in hot working was set at 70% or more because non-magnetic steel wire rods are subjected to cold working such as wire drawing as described in l-. High ductility and strength are achieved by first refining the structure. It is necessary to maintain the full area, and for that purpose, the degree of work in hot rolling is 70
This is because it requires at least 2%.

The winding temperature of non-magnetic steel wire is closely related to its crystal grains. That is, when the winding temperature is less than 900° C., grain growth of the crystals is suppressed, resulting in extremely fine crystals. In addition, a part of processing distortion remains accordingly.

As a result, the cold workability of the wire is impaired.

In addition, if the coiling temperature is less than 900°C, excessive carbides and the like will precipitate at grain boundaries, which will lead to a decrease in cold workability and corrosion resistance, although it also depends on the subsequent cooling rate.

On the other hand, if the coiling temperature exceeds 1000°C, the crystal grains will become coarse, which will also lead to a decrease in cold workability. Therefore, in the present invention, the winding temperature is 900°C or higher, 1
000℃ or less.

By limiting the cooling rate to 5°C/sec Iu, Mn, C
This is because carbides such as R tend to precipitate, and unless forced cooling is performed after winding the wire, precipitation of these carbides is unavoidable. When these carbides precipitate, the increase is +1
1. This leads to a decrease in cold workability and corrosion resistance. In the present invention, although it is related to the above-mentioned coiling temperature, the lower limit cooling rate is set to 5°C/Se (, for example, 900°C or less + noo'r: below) The high-temperature melon was rolled up in a Rusco-Igetsu-2, and then forced cooling was performed using an appropriate refrigerant to ensure a cold melon of 5°C, /see or less, and the carbide analysis 111 was carried out. Avoiding.

According to the invention, the hot-rolled material thus obtained is then subjected to omitting the normally required solution treatment and:
Wire drawing was performed for 76 minutes while trying to reduce the strength from 1 to 1. We aim to

As you can see, according to the present invention, in order to obtain the target strength,
l. Work hardening by cold wire drawing is used, but the strength is increased by rolling, so the wire drawing area reduction rate is 55% or more 1, preferably number 5.
A relatively low value of 5 to 70% can be adopted, and therefore L7,
In this respect as well, the present invention can reduce the wire drawing': 1 s1,
It becomes possible to supply cheap wire moons.

In addition, according to another preferred embodiment of the present invention, prior to the above-mentioned hot rolling process, heating is performed to a temperature of 1150° C. or higher and lower than 1250° C. In hot rolling of alloy steel, it is necessary to re-dissolve precipitates such as carbides into the 7 trix, so it is preferable to heat the alloy steel to a high temperature within the above range.

When heating in this way, there is generally no problem in practical use if the temperature is 1150°C or higher, but these steels have a high resistance to hot deformation, so it is difficult to do so. 1. The higher the temperature, the easier the rolling process. However, when the temperature exceeds 1250°C, the deformability is significantly reduced and problems such as processing cracks may occur.

Next, the present invention will be further explained by examples.

Example - Three types of steel with the compositions shown in Table 1 were prepared, heated to 1200°C, hot rolled at a reduction of area of 80%, and then rolled to 950°C.
After winding the wire rod, it was cooled at a cooling rate of 10° C./second to produce a hot rolled wire rod. The hot rolled wire rods (diameter 5.5 mm) thus obtained were cold drawn as shown in each table, and the mechanical properties, corrosion resistance, etc. of the obtained wire rods were evaluated. In each case, a hot rolled 1lIl wire 1A having a diameter of 5.5 mm was cold drawn to a diameter of 3.2 mm. Specific processing additions (!1 are summarized in Table 2, but if 3L is included in the present invention,
No solution treatment was performed prior to cold l1ll cotton. In the table, high Mn steel of steel type 2 was subjected to cold wire drawing without solution treatment as in the present invention.
．． It broke during wire drawing when the reduction in area was 51%.

4 “Oh, evaluate each characteristic of the preparation in each example 1+ll
The test method adopted for the test was as follows.

Corrosion resistance J'L test: Wire drawing (test) with #500 paper
The l-geriJI polished test pieces were subjected to an exposure test for 60 hours in a humid environment under saturated artificial seawater and atmospheric pressure at 60°C, and the state of rusting was visually observed. Those with no rust were rated as [-good].

I width JIJJ! Measurements were made for products manufactured by the processing industry in Table 2. Therefore, the processing history differs depending on the type of steel.

Drawing-cotton lower circle: There are various methods for evaluating the wire drawing limit, but here we will use The degree of wire drawing at the time when either of the following conditions occurred was defined as the wire drawing limit: ■ If the fracture surface of the tensile test material cracked vertically and the crack progressed to the base material, .

Ichiki Hunger: The evaluation of machinability was classified based on the finish of the cut surface, taking into account its use.

In other words, if there is no peeling at all on the finished surface after peeling on a lathe, it is ``O'', and if there are slight peeling flaws, it can be put into practical use with some modification.''There are no problems. Those with 1' cracks were evaluated as "△", and those with excessive scratches that were judged to be unsuitable for practical use were evaluated as "x".

The influence of the floor plan temperature after hot rolling is shown for the case of the present invention. In this example, hot rolling was performed at a heating temperature of 1200° C., a cooling rate of 5° C./sec, and an area reduction rate of 75% or more.

The wire drawing conditions were the same as in Test No. 3 of Example 1.

The composition of the steel used in this example is shown in Table 4.

The results are summarized in Table 5, and as is clear from these, when the nipping temperature is low, carbides precipitate in the steel, which deteriorates the corrosion resistance and makes the steel unusable.

In addition, the ductility decreases slightly and the wire drawability decreases. On the other hand, if the winding temperature is too high, the crystal grains will intertwine and the ductility will deteriorate. Therefore, +SS layer temperature 900° (: above,
And it is appropriate that 71F L, < is ]000'c or less.

In this example, the influence of the working degree (area reduction rate) of hot rolling was investigated. In this example, the heating temperature is 1200°C11) Quality 100
0゛C1 Under conditions of cooling rate 5℃/sec P! After rolling for 1 hour, the drawn wire (II) had an area reduction rate of 66.1%, which was the same as Test Teeth 3 of Example 1. The composition of the steel used in this example was as shown in Table 6. Ta.

The obtained results are summarized in Table 7, and as is clear from these, it is clear that when the working degree is small, the crystal grains intersect with each other, resulting in low ductility and wire drawing becomes impossible.

Length jii Italy/11 In this example, the influence of 10 cooling speeds after winding was investigated.

In this example, the sample used in Example 2 was used, the heating temperature was 1200℃, and the temperature was 10 (10℃1
Hot rolling was performed at a rolling degree of 75%. The wire drawing conditions were the same as in Test No. 3 of Example 1. Cooling was performed using the Stelmore method, and the cooling rate was varied by changing the air volume.

The results are summarized in Table 8, and as can be seen from these data, if the cooling rate is slow, carbides in the steel will precipitate and impair corrosion resistance, so the cooling rate after taking the ta count should be 5°C/sec or more. is necessary.

In this example, we investigated the effects of solution treatment before wire drawing and the degree of wire drawing. In this example, the same steel type as in Example 2 was used, and the hot rolling conditions were a rolling temperature of 1200°C, a tS temperature of 1000°C, and a rolling degree of 75%.

The wire drawing conditions were the same as those for test tooth 3 of Example 1.

The tensile strength and reduction of area of the obtained wire drawn material were evaluated. FIGS. 1 and 2 are graphs showing the tensile strength and the aperture value against the wire drawing area reduction ratio, respectively. In each figure, the graph indicated by mark 1 is data obtained by examining wires that were cold-drawn directly to a diameter of 3°2 mII+ without solution treatment at a cooling rate of 7°C/sec after hot rolling. On the other hand, according to graph t (not shown in No. 2-C), the cooling rate after hot rolling was set to 3°C/sec, and since the solutionization was insufficient as it was, the temperature was further increased to 110°C (by cooling with water after heating for 1'c). This is experimental data for a wire that has been subjected to solution treatment and then cold-drawn to a diameter of 3.2 mm.If the method of the present invention is applied, the hot-rolled material can be used as it is, and in particular, it can be subjected to It can be seen that a strength of 180 kg/m'fa or more can be easily obtained because it is unnecessary and has high strength and good drawability.

(Effect) - As is clear from the above, if the hot rolling conditions are outside the range specified in the present invention, the wire drawability will deteriorate at the same time as the corrosion resistance deteriorates, so the wire drawing area reduction ratio should be set high. In some cases, the required strength cannot be obtained.

In addition, even if the hot rolling conditions are within the range of the present invention, corrosion resistance can be improved if solution treatment is performed in a separate process after rolling, but the solution treatment increases costs and decreases the strength by -F, which reduces wire drawing. It is necessary to have a high area ratio, which is disadvantageous in terms of loss 1, and the effects of the present invention are clear from this point as well.

Table 7 Table 8

[Brief explanation of drawings]

FIG. 1 is a graph showing the tensile strength of the steel wire manufactured by the method according to the present invention, as well as that of a comparative example, against the drawing area reduction ratio; and FIG. 2 is a graph showing the reduction of area. It is. Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent Attorney Akira Hirose - (1 other person) (-shiro) Armored skin distortion'li I& (vo)r-sil

Claims (1)

[Claims] In weight%, C: 0.01 to 0.50%, Si: 1.0% or less, Mn
:10~25%, Ni:0.1~5%, Cr:10~2
0%, N: 0.01 to 0.5%, and if necessary, Se: 0.005 to 0.30%, Te: 0.005 to 0.
．． 30%, Pb: 0.05-0.20%, Ca: 0.0
Steel containing one or more of 0.005 to 0.02% and S: 0.03 to 0.15%, with the balance consisting of Fe and unavoidable impurities, is rolled with an area reduction of 70% or more. Hot rolling is carried out under the conditions of a take-up temperature of 900 to 1000°C and a cooling rate of 5°C/sec or more after winding, and then the obtained wire is directly rolled without solution treatment with an area reduction of 55% or more. A method for producing a non-magnetic steel wire with high tensile strength of 180 kg/mm^2 or more and excellent corrosion resistance, the method comprising cold drawing.