JP5872334B2 - Soft magnetic stainless steel fine wire and method for producing the same - Google Patents

Description

  The present invention relates to an inexpensive stainless steel fine wire product excellent in shape stability and soft magnetism, and relates to a high purity ferritic stainless steel fine wire in which the crystal grain size is controlled with respect to the wire diameter by heat treatment conditions and a method for producing the same.

  Conventionally, the thin wire (wire diameter: 0.05mm to 0.5mm) of soft magnetism (maximum relative permeability ≧ 800) with excellent corrosion resistance used for magnetic filters, etc. is repeatedly annealed and drawn with low-carbon carbon steel, and then However, since the annealing temperature is as low as around 700 to 800 ° C., a long time heat treatment is required to completely remove the strain that becomes the domain wall, and the surface treatment is necessary. In addition, since the shape stability such as sagging is poor and the product yield is poor, a large cost is required. Further, the surface treatment sometimes peeled off, and the corrosion resistance was unstable.

  On the other hand, as for stainless steel with excellent corrosion resistance, there are many proposals of ferritic electromagnetic stainless steel with improved magnetic response by adding Al and high purity ferritic electromagnetic stainless steel with excellent cold forgeability with ultra-low C and N. (For example, Patent Documents 1 and 2). However, long-time heat treatment at 850 ° C, 4h or 900 ° C, 2h is required. When manufacturing with a thin wire having a wire diameter of 0.5 mm or less, it is necessary to repeat wire drawing and heat treatment, resulting in enormous costs. In addition, the shape stability such as sagging is poor and the product yield is significantly deteriorated.

  A ferrite stainless steel wire having a diameter of 50 to 200 μm for a magnetic filter is also disclosed (Patent Document 3). However, there is no description regarding dimensional stability such as high magnetic permeability characteristics and sagging of steel wire.

  Furthermore, in recent years, a high-purity ferritic stainless steel wire having magnetism by strand annealing (bright annealing) at about 1050 ° C. for about 3 minutes and a manufacturing method with high productivity have been proposed (Patent Document 4). However, excellent magnetic properties cannot be obtained with fine wires (wire diameter ≦ 0.5 mm) due to the effect of wire drawing distortion, although they are magnetized. Further, even if strand annealing (bright annealing) is performed, excellent magnetic properties cannot be satisfied due to the formation of a martensite structure on the surface due to surface nitriding, and productivity is also problematic.

  For this reason, conventional steel fine wires (wire diameter: 0.05 to 0.5 mm) cannot combine corrosion resistance with excellent shape stability and soft magnetism at low cost.

Japanese Patent Laid-Open No. 2004-27307 Japanese Patent Laid-Open No. 02-15143 JP-A-56-38116 JP 2006-16665 A

  The present invention eliminates the problems of the prior art as described above, provides a high-purity ferritic stainless steel fine wire (wire diameter ≦ 0.5 mm) excellent in soft magnetism, and a low-cost manufacturing method. It is an object to provide a large amount of products that are more excellent in shape stability than magnetic wires at dramatically low cost.

  As a result of various studies to solve the above-mentioned problems, the present inventors have added a stabilizing element such as Nb and Ti to obtain a very low C and N high purity ferritic stainless steel fine wire (wire diameter: 0. 0). Stainless steel fine wires with excellent magnetic properties (maximum relative permeability ≧ 800) by controlling the average crystal grain size with respect to the wire diameter by subjecting strand annealing (bright annealing) at a high temperature for a single time at 05 to 0.5 mm) Has been found to be dramatically cheaper. This invention is made | formed based on the said knowledge, and the place made into the summary is as follows described in the claim.

(1) By mass%, C: 0.03% or less, Si: 1.0% or less, Mn: 1.0% or less, P: 0.04% or less, S: 0.02% or less, Ni: 1 0.0 % or less, Cr: 10.5 to less than 16.2% , Al: 1.5% or less, O: 0.01% or less, N: 0.03% or less, and Nb: 0.00% or less . 05-1.0%, Ti: 0.05-1.0%, V: 0.05-1.0%, W: 0.05-1.0%, Ta: 0.05-1.0% Among them, it contains at least one kind, and is composed of the remaining Fe and inevitable impurities, and has a ferrite single-phase structure. The wire diameter is 0.05 to 0.5 mm, and the average crystal grain size is 0.1 to 0.1. A soft magnetic stainless steel fine wire characterized by being 0.8 times and having a maximum relative permeability of 800 or more.
(2) The soft magnetic stainless steel thin wire according to (1), further containing, by mass%, Mo: 2.5% or less.
(3) The soft magnetic stainless steel thin wire according to (1) or (2), further containing B: 0.0001 to 0.01% by mass%.
(4) Further, by mass%, one or more of Cu: 1.0% or less and Co: 1.0% or less are contained. Any one of (1) to (3) Soft magnetic stainless steel fine wire as described.
(5) Further, by mass%, one or more of Ca: 0.0005 to 0.01%, Mg: 0.0005 to 0.01%, and REM: 0.0005 to 0.05% should be contained. The soft magnetic stainless steel fine wire according to any one of (1) to (4).
(6) The soft magnetic stainless steel according to any one of (1) to (5), which is finished by performing final strand annealing at 900 to 1200 ° C. for 5 to 60 seconds after the final wire drawing. Thin wire manufacturing method.

  The high purity ferritic stainless steel fine wire (wire diameter ≦ 0.5 mm) with controlled crystal grain size relative to the wire diameter according to the present invention is excellent in the material itself in the wire drawing / heat treatment process with high productivity (high product yield). Because it has both corrosion resistance and soft magnetism with maximum relative permeability ≧ 800, it can provide a large amount of fine wire products with excellent corrosion resistance, shape stability and soft magnetism at a great price, and has a remarkable industrially useful effect. .

  First, the reason for limitation described in (1) of the present invention will be described.

  C and N combine with Nb, Ti and the like to form carbides, but when added in excess of 0.03%, coarse carbonitrides are formed, soft magnetism and toughness deteriorate, and productivity is reduced. to degrade. Therefore, each upper limit is made 0.03%. A preferred range is 0.005 to 0.02%.

  Si is added for deoxidation, but if added over 1.0%, the toughness of the fine wire deteriorates and the productivity deteriorates. Therefore, the upper limit is limited to 1.0%. A preferable range is 0.1 to 0.5%.

  Mn is added for deoxidation. However, addition exceeding 1.0% not only deteriorates the magnetic properties, but also deteriorates toughness and productivity. Therefore, the upper limit is limited to 1.0%. A preferable range is 0.1 to 0.5%.

  P is an unavoidable impurity and is limited to 0.04% or less in order to deteriorate soft magnetism. Preferably, it is 0.025% or less.

  S is an unavoidable impurity and is limited to 0.02% or less in order to deteriorate soft magnetism. Preferably, it is 0.005% or less.

  Ni is added as necessary in order to improve corrosion resistance and toughness. However, Ni is limited to 1.0% or less because soft magnetism is deteriorated when excessively added. Preferably, Ni: 0.05 to 0.5%.

  Cr is basically added to ensure corrosion resistance. However, if it is less than 9.0%, an austenite phase is generated during high-temperature strand annealing, and martensitic transformation occurs during cooling, thereby degrading soft magnetism. On the other hand, if added over 17.0%, the magnetic flux density is lowered and soft magnetism is deteriorated. Therefore, it is limited to 9.0 to 17.0%. A preferable range is 10.5% to 16.5%.

  Al is added for deoxidation. However, if it exceeds 1.5%, productivity deteriorates. Therefore, the upper limit is limited to 1.5%. A preferable range is 0.002% or more and less than 0.05%.

  O is an unavoidable impurity and is limited to 0.01% or less in order to ensure soft magnetism. Preferably, it is 0.008% or less.

  Nb, Ti, V, W, and Ta form carbonitride and fix C and N, thereby suppressing the formation of martensite structure and improving soft magnetism. However, if added excessively, coarse carbonitrides are produced and soft magnetism is deteriorated. Therefore, Nb: 0.05-1.0%, Ti: 0.05-1.0%, V: 0.05-1.0%, W: 0.05-1.0%, Ta: 0. It is limited to containing 1 or more types in 05-1.0%. Preferably, Nb: 0.2-0.6%, Ti: 0.05-0.2%, V: 0.1-0.5%, W: 0.1-0.5%, Ta: 0.1 It contains at least one of ˜0.5%.

  When the metal structure is mixed with 5% by volume or more of a metal structure other than a ferrite structure such as a martensite structure or an austenite structure, the soft magnetism rapidly deteriorates. Therefore, it is limited to a ferrite single phase structure excellent in soft magnetism.

    The control of the wire diameter and the average crystal grain size is the greatest characteristic of the present invention. When the wire diameter exceeds 0.5 mm, there is no problem of martensite generation due to sagging or surface nitriding, and shape stabilization is possible even with a conventionally known manufacturing method. Steel wire excellent in properties and soft magnetism can be produced, and the superiority of the present invention is lost. Therefore, the wire diameter is limited to 0.5 mm or less. On the other hand, when the wire diameter is less than 0.05 mm, the shape stability is poor even when the present invention is applied. Therefore, the wire diameter is limited to 0.05 to 0.5 mm. A preferable wire diameter range is 0.1 to 0.4 mm.

  If the average crystal grain size is less than 0.1 times the wire diameter, the proportion of crystal grain boundaries that become domain walls increases and soft magnetism deteriorates. On the other hand, when it exceeds 0.8 times, soft magnetism deteriorates conversely due to the anisotropy of crystal grains. Therefore, the average crystal grain size is limited to 0.1 to 0.8 times the wire diameter. A preferred range is 0.2 to 0.5 times the wire diameter.

  The maximum relative permeability (ratio to the permeability in vacuum. The maximum relative permeability = 1 indicates the permeability in vacuum) is an index of soft magnetism, and can be manufactured by a known manufacturing method as long as it is less than 800. It is. In order to show the superiority of the effect of the present invention, the maximum relative permeability is limited to 800 or more. A preferable range is 1000 or more.

Next, the reason for limitation described in (2) of the present invention will be described.
Mo is an element that improves the corrosion resistance, and if necessary, 2.5% or less is added. However, if added over 2.5%, soft magnetism deteriorates. Therefore, it is limited to 2.5% or less. A preferable range is 0.05 to 1.0% or less.

    Next, the reason for limitation described in (3) of the present invention will be described.

  B is added in an amount of 0.0001% or more as necessary in order to improve the toughness of fine wires and improve the productivity. However, if added over 0.01%, coarse boride not only deteriorates soft magnetism but also deteriorates toughness and productivity, so the upper limit is made 0.01%.

    Next, the reason for limitation described in (4) of the present invention will be described.

  In order to improve the toughness of fine wires and improve productivity, Cu and Co are each added in an amount of 1.0% or less as necessary. However, if added over 1.0%, soft magnetism deteriorates. Therefore, the upper limit is limited to 1.0% each. Preferred ranges are each 0.01 to 0.5%.

    Next, the reason for limitation described in (5) of the present invention will be described.

  Ca, Mg, and REM are effective elements for deoxidation, and are added as necessary. However, when added excessively, soft magnetism is deteriorated, and productivity is deteriorated due to a coarse deoxidation product. Therefore, it is limited to containing one or more of Ca: 0.0005 to 0.01%, Mg: 0.0005 to 0.01%, and REM: 0.0005 to 0.05%.

  Next, the reason for limitation described in (6) of the present invention will be described.

  After the final wire drawing to a wire diameter of 0.05 to 0.5 mm, heat treatment is performed to reduce processing strain and crystal grain boundaries that become domain walls. However, if the temperature is below 900 ° C., soft magnetism is inferior, and if it exceeds 1200 ° C., the wire breaks. It is inferior in shape stability due to thinning of the wire, etc., and the product yield is significantly deteriorated. Therefore, the heat treatment temperature is limited to 900 to 1200 ° C. A preferred range is 1000-1160 ° C.

  In addition, it is necessary to limit the heat treatment time in order to secure shape stability and obtain excellent soft magnetism by controlling the crystal grain size in the thin wire. Single-hour strand annealing is performed, but if the heat treatment time (in-furnace time) is less than 5 seconds, the crystal grain size is small and the soft magnetism is poor. On the other hand, if the heat treatment time exceeds 60 seconds, the crystal grain size becomes coarse and anisotropy occurs, so it is not only inferior in soft magnetism, but also is thin and inferior in shape stability, or the disconnection rate increases. Yield deteriorates. Therefore, it is limited to 5 to 60 seconds. A preferred range is 10 to 40 seconds.

  Since it is desirable that the strand annealing atmosphere does not require pickling after annealing for shape stability, a hydrogen gas atmosphere, a nitrogen gas atmosphere, an Ar gas atmosphere and a mixed gas atmosphere thereof, which are performed in general stainless steel, are used. preferable.

  Examples of the present invention will be described below. Table 1 shows the chemical composition (mass%) of the steels of the examples.

  Assuming AOD melting, which is a cheap melting process for stainless steel, these chemical compositions are melted in a 100 kg vacuum melting furnace, cast into a slab of φ180 mm, and the slab is reduced to φ5.5 mm Hot wire rolling was performed, and the hot rolling was terminated at 1000 ° C. Then, after hold | maintaining at 1050 degreeC as a solution treatment for 30 minutes, it cooled with water, pickled, and was set as the wire. Thereafter, wire drawing and normal annealing were repeated until φ1.0 mm.

After that, in order to investigate the influence of the components, 30 kg was sampled and subsequently cold-drawn to 0.1 mm. Then, as the final annealing, strand annealing (bright annealing) in the furnace at 1100 ° C. for 20 seconds was performed. It was made into a product of stainless steel fine wire that was applied and coiled.
The effects of components on the soft magnetism, metal structure, crystal grain size (ratio to wire diameter), corrosion resistance and product yield of steel fine wire products were evaluated. The evaluation results are shown in Table 2.

  The soft magnetism of steel wire products is obtained by using a DC magnetization characteristic test device and drawing a hysteresis curve using the Epstein method, and calculating the relative maximum permeability (the maximum permeability is obtained and the ratio to the permeability in vacuum is corrected). It was measured. The specific maximum magnetic permeability of the steel wire of the example of the present invention was 800 or more, indicating excellent soft magnetism.

  The metallographic structure of the steel wire product was evaluated by optical microscopic observation after aqua regia etching of the vertical cross-section embedded surface of the steel wire. The metal structure of the steel wire of the present invention was a ferrite single phase.

  The average crystal grain size of the steel wire product is obtained by performing optical aquatic observation after etching the vertical cross-section embedded surface of the steel wire, obtaining the average crystal grain size in the longitudinal direction of the steel wire by a cutting method, and calculating the average crystal grain size / wire diameter. The ratio of was calculated. For the cutting method, a straight line was drawn in the longitudinal direction of the steel wire in the photomicrograph, the number of points where the straight line and the grain boundary intersected was counted, and the average crystal grain size was calculated by (straight line length) / (number of crossings) . The ratio of the average crystal grain size / wire diameter in the inventive examples was in the range of 0.1 to 0.8.

  The corrosion resistance of the steel wire product was evaluated according to whether or not it was sprinkled by carrying out a spray test for 100 hours according to the salt spray test of JIS Z 2371. Corrosion resistance was evaluated as good if it was a non-fogging level, and corrosion resistance was evaluated as poor in the case of red rust such as flowing rust. All the evaluations of the corrosion resistance of the steels of the present invention were good.

  The yield of the steel wire product was determined from the mass% of the non-defective product at the time of the steel wire product with respect to the sampling material of 30 kg. When the wire diameter was 10% or more with respect to the wire diameter, when the wire was broken, or when there was a sag / bend, it was judged as a defective product and the yield was reduced. The product yield of the example of the present invention was 80% or more, indicating a good yield.

  Next, in order to investigate the influence of the wire diameter and the average crystal grain size, 30 kg of a steel wire having a wire diameter of 1.0 mm of the annealed steels A, AG and AL shown in the paragraph [0035] is sampled. The steel wire was cold-drawn to 0.03 to 0.7 mm, subjected to final annealing under various conditions, and then pickled as necessary to obtain a stainless steel fine wire product that was scraped into a coil. Then, the influence of components on the soft magnetism, crystal grain size (ratio to wire diameter) and product yield of steel fine wire products was evaluated. The evaluation results are shown in Table 3.

  The inventive examples showed excellent soft magnetism (maximum relative magnetic permeability) and product yield. On the other hand, in the comparative example, the wire diameter, annealing temperature, and annealing time were out of the present invention, and the soft magnetism (maximum relative permeability) and product yield were inferior. Comparative Example No. 84, 100, and 116 are superior to the present invention in the region where the wire diameter is thicker than the range of the present invention, because excellent soft magnetism and product yield can be obtained even by the conventionally proposed processes (batch annealing and pickling). Is not allowed.

As is clear from each of the above examples, the present invention can produce high-purity ferritic stainless steel fine wires excellent in soft magnetism at low cost, and can reduce the cost of thin wire products such as magnetic filters having excellent corrosion resistance and soft magnetic properties. It can be provided and is extremely useful in industry.

Claims (6)

% By mass
C: 0.03% or less,
Si: 1.0% or less,
Mn: 1.0% or less,
P: 0.04% or less,
S: 0.02% or less,
Ni: 1.0% or less,
Cr: 10.5 to less than 16.2% ,
Al: 1.5% or less,
O: 0.01% or less,
N: 0.03% or less,
Furthermore,
Nb: 0.05-1.0%
Ti: 0.05 to 1.0%,
V: 0.05-1.0%
W: 0.05-1.0%
Ta: 0.05 to 1.0%, containing one or more types, balance Fe and inevitable impurities, ferrite single phase structure, wire diameter 0.05 to 0.5 mm, average crystal A soft magnetic stainless steel fine wire having a particle diameter of 0.1 to 0.8 times the wire diameter and a maximum relative permeability of 800 or more. In addition,
Mo: 2.5% or less is contained, The soft-magnetic stainless steel fine wire of Claim 1 characterized by the above-mentioned. In addition,
B: The soft magnetic stainless steel fine wire according to claim 1 or 2, characterized by containing 0.0001 to 0.01%. In addition,
Cu: 1.0% or less,
The soft magnetic stainless steel fine wire according to any one of claims 1 to 3, wherein Co: 1.0% or less contains one or more types. In addition,
Ca: 0.0005 to 0.01%,
Mg: 0.0005 to 0.01%,
The soft magnetic stainless steel fine wire according to any one of claims 1 to 4, wherein one or more of REM: 0.0005 to 0.05% are contained.   The method for producing a soft magnetic stainless steel fine wire according to any one of claims 1 to 5, wherein the final strand annealing is performed by performing final strand annealing at 900 to 1200 ° C for 5 to 60 seconds.