JP4519543B2 - Low cost stainless steel wire having magnetism with excellent corrosion resistance, cold workability and toughness, and method for producing the same - Google Patents

Description

The present invention relates to an inexpensive stainless steel wire that is required to have magnetism and corrosion resistance and a manufacturing method thereof , such as fasteners, machine forged parts, electromagnetic parts, ropes, wire mesh / mesh, flat wires , etc., and conventional austenitic stainless steels. The present invention relates to a ferritic stainless steel wire that can be manufactured by the same general-purpose manufacturing process and a manufacturing method thereof .

  So far, products such as fasteners that require cold workability, corrosion resistance, and toughness have been manufactured by drawing, strand annealing, cold working, and the like of austenitic stainless steel wires such as SUS304 and SUSXM7.

  However, a product of austenitic stainless steel has a drawback of high product price despite an inexpensive manufacturing process because a large amount of expensive Ni is added.

  Also, since austenitic stainless steel is not magnetized, it is not workable because it does not attach to the tool when fastening fasteners. If the material is missing due to a wire mesh / mesh (especially a food conveyor), it is mixed with food. Inconvenient due to lack of magnetism, such as being unable to check contamination by a magnetic sensor.

  On the other hand, for products manufactured from ferritic stainless steel wires and requiring magnetism, corrosion resistance and toughness, ferritic stainless steel wires with low C, N and Nb added have been proposed (Patent Document 1). .

  In particular, in the stainless steel to which Nb or the like is added, it has also been proposed to improve the toughness by controlling the rolling heating temperature to 1200 ° C. or more and the size of carbonitride to 20 μm or less (Patent Document 2).

  However, since these ferritic stainless steel wires are different from the normal wire rolling conditions, surface wrinkles such as wrinkles and seizure flaws are generated, so that they cannot be manufactured at low cost.

  Furthermore, conventionally, since these ferritic stainless steel wires are batch annealed at a temperature of 850 ° C. or lower and pickled, they are manufactured more than austenitic stainless steel wires that are subjected to strand annealing (bright annealing) at about 900 ° C. or higher. There was a problem of high costs.

  As described above, the conventional ferritic stainless steel wires require a high production cost for the use of inexpensive raw materials, so austenitic stainless steel that has excellent cold workability unless it requires magnetism, especially for products that require corrosion resistance and toughness. Steel wire has been used.

Japanese Patent No. 2906445 Japanese Patent No. 2817266

An object of the present invention is to provide an inexpensive ferritic stainless steel wire having excellent cold workability, corrosion resistance, and toughness, having magnetism, and a method for producing the same . Further, by producing a product by a general-purpose manufacturing process, austenitic stainless steel Is to significantly reduce the manufacturing cost of a conventional product that has been used and to provide magnetism.

As a result of various studies to solve the above-mentioned problems, the present inventors have found that, based on a ferritic stainless steel wire having low C magnetism added with Nb, AlN and V-based carbonitriding that affect the crystal grain size. Corrosion resistance is controlled by controlling coarse inclusions by controlling S and O that affect cold workability, corrosion resistance, and toughness, and by controlling Cr, Si, and Mn, which affect surface defects. It has been found that toughness and cold workability can be improved and surface flaws can be suppressed. Further, it was found that annealing can be performed under the same general-purpose conditions as austenitic stainless steel wires by suppressing Cr and controlling carbonitride (see Table 1). The present invention has been made based on the above findings.

  That is, the gist of the present invention is as follows.

(1) By mass%, C: 0.003 to 0.04%, Si: 0.05 to 1.0%, Mn: 0.05 to 0.5%, P: 0.04% or less, S: 0.005% or less, Cr : 10.5 to 18.0%, O: 0.010% or less, N: 0.003 to 0.04%, and Nb: 0.1 to 0.8 %, Ti: 0.01 to 0.5% or more, Al: 0.1% or less, V: 0.03 to 1.0% or more, the balance being Fe and inevitable [O] + [S] ≦ 0.010%, [Mn] + [Cr] + [Si] ≦ 18.5%, and [Al] × [N] ≦ 0.0020, [O] + [S] ≦ 0.010% A cold-drawn steel wire with V] × [N] ≦ 0.016 is subjected to strand annealing in a temperature range of 950 ° C. to 1100 ° C., and ferrite average crystal grains are formed according to JIS G 0052. Number is the manufacturing method of inexpensive stainless steel wire having magnetic excellent between corrosion resistance and cold workability, toughness, characterized by a 5-9.
(2) The low-cost stainless steel wire having magnetism excellent in corrosion resistance, cold workability, and toughness according to (1) above, wherein the average grain size of ferrite is JIS G 0052 and the grain size number is 7-9 It is a manufacturing method.
(3) Further, B: 0.0003 to 0.010% by mass% is contained, and the magnetism is excellent in corrosion resistance, cold workability, and toughness as described in (1) or (2) above This is a method for producing an inexpensive stainless steel wire.
(4) The above (1) to (1), further comprising at least one of Ni: 1.0% or less, Cu: 1.0% or less, and Mo: 3.0% or less in terms of mass%. 3) A method for producing an inexpensive stainless steel wire having magnetism with excellent corrosion resistance, cold workability, and toughness.
(5) Ferritic stainless steel wire excellent in corrosion resistance, cold workability, and toughness manufactured by the method according to any one of (1) to (4), characterized in that it is used for fasteners or machine forged parts. is there.
(6) Ferritic stainless steel excellent in corrosion resistance, cold workability, and toughness manufactured by the method according to any one of (1) to (4) above, characterized in that it is used for ropes, wire mesh, and mesh products Is a line.
(7) A ferritic stainless steel wire excellent in corrosion resistance, cold workability, and toughness manufactured by the method according to any one of (1) to (4), characterized in that it is for a flat wire.

  [O], [S], [Mn], [Cr], [Si], [Al], [V], and [N] represent the content of each element in mass%. .

The high cold workability, corrosion resistance, and high toughness ferritic stainless steel wire according to the present invention and the manufacturing method thereof can perform the same general-purpose strand annealing as an austenitic stainless steel wire, although it does not contain much expensive Ni. It is effective in dramatically reducing the manufacturing cost of corrosion-resistant and high-toughness products and imparting magnetism.

  Below, the reason for limitation of Claim 1 of this invention is demonstrated first.

  C and N are added in an amount of 0.003% or more in order to ensure the strength of the steel. On the other hand, it combines with Nb to form Nb carbide, but if added over 0.04%, Cr carbonitride is generated, and corrosion resistance, cold workability, and toughness deteriorate. Therefore, the upper limit is made 0.04%. A preferable range is 0.005 to 0.02% or less.

  Si is added at 0.05% or more for deoxidation. However, if added over 1.0%, cold workability and toughness deteriorate. Therefore, the upper limit is limited to 1.0%. A preferable range is 0.1 to 0.4%.

  Mn is added at 0.05% or more for deoxidation. However, if it exceeds 0.5%, corrosion resistance and cold workability deteriorate. Therefore, the upper limit is limited to 0.5%. A preferable range is 0.1 to 0.3%.

  P is limited to 0.04% or less in order to deteriorate cold workability and toughness. Preferably, it is 0.025% or less.

  S degrades cold workability and toughness or corrosion resistance, so it is limited to 0.005% or less. Preferably, it is 0.003% or less.

  Cr is basically added in an amount of 10.5% or more in order to ensure corrosion resistance, but if added over 18.0%, recrystallization becomes difficult during wire rolling and not only wrinkle wrinkles are likely to occur, but also rolls. As a result, seizure occurs and wire surface flaws occur frequently. Therefore, the upper limit is limited to 18.0%. A preferred range is 12.0% to 17.0%.

  Nb forms carbonitride and fixes C, thereby suppressing the formation of Cr carbonitride and improving corrosion resistance and toughness (particularly improving the corrosion resistance and toughness of the welded portion). Therefore, 0.1% or more is added. However, if added over 0.8%, coarse carbonitrides are formed, so that cold workability and toughness deteriorate. Therefore, the upper limit is limited to 0.8%. Preferred ranges are 0.2% to 0.6%, (Nb + Ti) / (C + N) ≧ 10.

  Ti, like Nb, forms carbonitride and fixes C, thereby suppressing the formation of Cr carbonitride and improving corrosion resistance and toughness. Moreover, fine ferrite grains are obtained from the fine Ti carbonitride to ensure toughness. Therefore, 0.01% or more is added. However, if added over 0.5%, coarse carbonitrides and oxides are formed, and on the contrary, not only cold workability and toughness but also surface defects are deteriorated, so the upper limit is made 0.5%. limit. A preferable range is 0.01 to 0.2%.

  Here, since Nb hardly forms a coarse oxide, it is preferable to add Nb alone from Ti from the viewpoint of surface defects.

  O is limited to 0.010% or less in order to ensure toughness. Preferably, it is 0.008% or less.

  [O] + [S] is a formation element of coarse inclusions and affects corrosion resistance, cold workability and toughness. Therefore, in order to improve corrosion resistance, cold workability and toughness, the content is limited to 0.010% or less. Preferably it is 0.008% or less. Here, in a low (C + N) ferritic stainless steel, in order to reduce [O] + [S] in a mass production process, for example, it is desirable to perform AOD refining under reduced pressure (100 Torr or less).

  [Mn] + [Cr] + [Si] affects the surface flaws, and if it exceeds 18.5%, wire rod flaws frequently occur due to seizure with hot rolling rolls. On the other hand, if it is 18.5% or less, the seizure property is lowered and surface flaws are reduced. Therefore, the upper limit is limited to 18.5%. Preferably, it is 17.5% or less.

  Al is added to deoxidize and obtain fine ferrite grains by fine nitride (AlN) to ensure toughness, but if added over 0.1%, the toughness deteriorates conversely. Therefore, the upper limit is limited to 0.1%. A preferred range is 0.002% to 0.06%.

  V is added in an amount of 0.03% or more in order to obtain fine ferrite grains from fine carbonitride and ensure toughness, but if added over 1.0%, coarse V-based carbonitride is generated, Conversely, toughness deteriorates. Therefore, the upper limit is limited to 1.0%. Preferably, it is 0.03 to 0.15% of range.

  [Al] × [N] affects the toughness, and if it exceeds 0.0020, coarse AlN is generated and the toughness deteriorates. On the other hand, if it is 0.0020 or less, fine ferrite grains are obtained by precipitation of fine AlN, and toughness can be ensured. Therefore, the upper limit is limited to 0.0020. Preferably, it is 0.0010 or less.

  [V] × [N] affects toughness, and if it exceeds 0.016, coarse V-based carbonitrides are produced, and thus toughness deteriorates. On the other hand, if it is 0.016 or less, fine ferrite grains are obtained by precipitation of fine V-based carbonitrides, and toughness can be ensured. Therefore, the upper limit is limited to 0.016. Preferably, it is 0.010 or less.

Conventionally, ferritic stainless steel wires have been subjected to batch annealing or strand annealing at a low temperature of 850 ° C. or lower because of abnormal grain growth. Therefore, productivity was low and manufacturing cost was high. The ferritic stainless steel wire of the present invention is annealed at the same high temperature as an austenitic stainless steel wire by regulating the amount of Cr and controlling AlN and V carbonitrides in addition to Nb and Ti based precipitates. Is characterized in that abnormal grain growth hardly occurs. On the other hand, when the annealing temperature is 850 ° C. or lower, recrystallization becomes insufficient and cold workability deteriorates. Conversely, if the temperature exceeds 1100 ° C., the ferrite grain size becomes coarse and the toughness deteriorates, so the upper limit is limited to 1100 ° C. If a preferable range is the range of 950-1050 degreeC, it can anneal with the same chance as a general purpose austenitic stainless steel wire, and productivity will improve. In particular, as an annealing process, strand annealing (such as bright annealing) can improve productivity most and is desirable.
When the average crystal grain size of the ferrite of the steel wire is less than 5, the toughness is remarkably deteriorated. On the other hand, the productivity is lowered and the cost is increased, for example, annealing is performed at a low temperature for a long time to obtain fine grains having a crystal grain size exceeding 9. Therefore, the ferrite grain size 5 to 9 is the optimum range from the viewpoint of toughness and cost. A preferred range is a crystal grain size of 6-9. Here, in order to control the crystal grain size, in addition to the regulation of the Cr amount as described above, AlN, V-based carbonitride (appropriate addition of Al, V, C, N) and a strand of more than 850 ° C. and 1100 ° C. This is a combination of annealing (in-furnace time of 10 minutes or less).
  In claim 2 of the present invention, crystal grain sizes of 7 to 9 are defined based on the description of the examples.

The reason for limitation according to claim 3 of the present invention will be described.
B suppresses P segregation at grain boundaries and further improves cold workability, so 0.0003% or more is added as necessary. However, if it exceeds 0.010%, the cold workability and toughness deteriorate due to the coarse boride. Therefore, the upper limit is limited to 0.010%. A preferred range is 0.001 to 0.008%.

  The reason for limitation according to claim 4 of the present invention will be described.

  Ni, Cu, and Mo are effective in improving the corrosion resistance while restricting the addition of Cr. Ni: 1.0% or less, Cu: 1.0% or less, Mo: 3. Add up to 0%. However, if more is added, cold workability deteriorates. Preferably, they are Ni: 0.05-0.8%, Cu: 0.05-0.8%, Mo: 0.1-2.5%.

The reasons for limitation according to claims 5 to 7 of the present invention will be described.

  Conventionally, austenitic stainless steel centering on SUS304 has been used for fasteners (screws, bolts, nuts, nails, etc.) having excellent corrosion resistance, machine forged parts, ropes, wire mesh / mesh products (gabion), and flat wires.

  Fasteners and machine forged parts have been manufactured by drawing wire and subjecting it to strand annealing (bright annealing), and then cold forging. In addition, it is desirable that fasteners and machine forged parts have magnetism in installation work.

  The ropes have been manufactured by forming a wire into a thin wire by a combination of wire drawing and strand annealing (bright annealing), and then stranded wire processing. Moreover, it is desirable that the ropes can use a magnetic sensor for detecting breakage / dropping.

  Wire meshes and meshes have been manufactured by forming a wire into a thin wire by a combination of wire drawing and strand annealing (bright annealing), and then wire mesh processing. In addition, it is desirable that the wire mesh / mesh can use a magnetic sensor when dropped.

  The flat wire has been manufactured by thinning a wire by a combination of wire drawing and strand annealing (bright annealing), and then flat rolling. In addition, it is desirable to use automatic handling with a magnet when handling the flat wire from the viewpoint of handling hooks.

  Since these products have a simple manufacturing process, it has been difficult to further reduce the cost. However, if these products can be manufactured from the ferritic stainless steel wire or steel wire of the present invention that can be manufactured in the same process (especially strand annealing) as austenitic stainless steel, not only can the cost of the product be significantly reduced, but also magnetic properties can be reduced. Can also be provided, and particularly the economic effect and convenience are increased. Therefore, the application is limited to these products.

  Examples of the present invention will be described below.

  Tables 2 and 3 show the chemical compositions of the steels of the examples.

  Steels of these chemical compositions are melted in a 100 kg vacuum melting furnace, cast into a slab of φ180 mm, the slab is hot-wire-rolled to φ5.5 mm, and hot rolling is finished at 1000 ° C., Subsequently, continuous annealing was performed at 1000 ° C. for 3 minutes, and then cooled to room temperature by water cooling. And pickling was performed and the surface flaw was investigated. Then, cold drawing was performed to φ3.85 mm.

  Thereafter, strand annealing (bright annealing, rapid cooling) was performed at 1050 ° C. (temperature carried out with an austenitic stainless steel wire), and cold workability (forging workability), toughness, corrosion resistance, and crystal grain size were investigated. The results are shown in Table 4.

  The surface defects of the wire were examined by surface observation of the wire coil after pickling. When there were no wrinkles with a depth of 0.1 mm or more, the evaluation of the surface flaws was ○, and when there were wrinkles, the evaluation of the surface flaws was ×. The evaluation of the surface flaw of the steel of the present invention is ○.

  Cold workability was evaluated by pressing a flat head-shaped pin with a double header at an upsetting rate of 80 to 94%, and using a head limit machining rate (limit upsetting rate). The forging speed was 90 pieces / minute, and machine oil was used as the lubricant. The critical processing rate of the steel of the present invention was 90% or more.

  As for toughness, 10 flat pins with an upsetting ratio of 86% are machined, then threaded by rolling, and JIS B 1055 head toughness test with a 15 ° inclination is performed at room temperature (25 ° C). Judgment was made based on whether or not the neck was broken. When all were not broken, the toughness was evaluated as “Good”. When even one was broken, the toughness was evaluated as “X”. All of the toughness evaluations of the steels of the present invention were ○.

  Corrosion resistance was evaluated by whether the surface layer of the steel wire was polished with # 500, followed by a spray test for 100 hours according to the salt spray test of JIS Z 2371, and whether or not it sprinkled. Corrosion resistance was evaluated as ◯ for non-fogging and spot rust levels, and corrosion resistance was evaluated as x for flow rust and full surface rusting. The evaluations of the corrosion resistance of the steels of the present invention were all good.

  The crystal grain size was measured by JIS G 0552 after embedding and polishing a steel wire in a longitudinal section, etching with aqua regia. The crystal grain size of the examples of the present invention was in the range of 5 to 9 in terms of grain size number.

  On the other hand, Comparative Example No. 27 to 43 were inferior in any of corrosion resistance, toughness, cold workability and wire surface flaws as compared with the present invention.

  Next, in order to investigate the influence of the strand annealing temperature of the steel wire on the properties (toughness), the strand annealing (bright annealing) was performed on the φ3.85 mm steel wire (as drawn) having the chemical composition of the steel E of the present invention described above. ) The temperature was changed to 700-1200 ° C. Thereafter, the crystal grain size, cold workability and toughness of the steel wire were evaluated by the method described above. The evaluation results are shown in Table 5.

  Example No. of the present invention in which strand annealing was performed in the range of 850 ° C. to 1100 ° C. Nos. 44 to 47 were excellent in cold workability and toughness. In particular, Invention Example No. 45 and 46 are excellent in productivity because strand annealing can be performed in the same temperature range (highly versatile temperature range) as the austenitic stainless steel wire. On the other hand, Comparative Example No. with strand annealing of less than 850 ° C. 48 and 49 had incomplete recrystallization and were inferior in cold workability. On the contrary, Comparative Example No. in which the strand annealing temperature exceeds 1100 ° C. No. 50 was inferior in toughness because the crystal grain size was coarsened to less than 5.

  Next, in order to confirm the effect of application limitation, fasteners were obtained from the φ5.5 mm wire (having solution treatment) having the chemical composition of the steel E of the present invention and the SUS304 φ5.5 mm wire in the normal manufacturing process described above. (Screw), rope, wire mesh, and flat wire were processed. Thereafter, the corrosion resistance was compared and evaluated with SUS304 by the method described above. The results are shown in Table 6.

  Using the ferritic stainless steel of the present invention, the corrosion resistance evaluation of the above-mentioned products manufactured by the general-purpose process of austenitic stainless steel is all ○, and it can be sufficiently used as an alternative to the SUS304 product, and has a magnetic property. The economic effect is great.

  As can be seen from the above embodiments, the superiority of the present invention is clear.

As is clear from the above examples, according to the present invention, it is possible to provide an inexpensive ferritic stainless steel wire excellent in cold workability, corrosion resistance, and toughness, and a method for producing the same , and magnetic fasteners. , It is extremely useful industrially for applications such as machine forging parts, ropes, wire mesh / mesh products (gabion), flat wire, etc.

Claims (7)

In mass%, C: 0.003-0.04, Si: 0.05-1.0%, Mn: 0.05-0.5%, P: 0.04% or less, S: 0.005% Cr : 10.5 to 18.0%, O: 0.010% or less, N: 0.003 to 0.04%, Nb: 0.1 to 0.8%, Ti: Contains one or more of 0.01 to 0.5%, one or more of Al: 0.1% or less, V: 0.03 to 1.0%, the balance being composed of Fe and inevitable impurities [O] + [S] ≦ 0.010%, [Mn] + [Cr] + [Si] ≦ 18.5%, and [Al] × [N] ≦ 0.0020, [V] × [ N] ≦ 0.016 cold-drawn steel wire is subjected to strand annealing at a temperature range of 950 ° C. to 1100 ° C., and the average grain size of ferrite is JIS G 0052 Method for producing a cheap stainless steel wire having magnetic excellent in corrosion resistance and cold workability, Toughness, characterized in that a to 9.   The method for producing a low-cost stainless steel wire having magnetism excellent in corrosion resistance, cold workability, and toughness according to claim 1, wherein the average grain size of ferrite is JIS G 0052 and the grain size number is 7-9.   Furthermore, B: 0.0003-0.010% is contained by mass%, The manufacture of the cheap stainless steel wire which has the magnetism which is excellent in corrosion resistance, cold workability, and toughness of Claim 1 or 2 characterized by the above-mentioned. Method.   Furthermore, at least 1 type of Ni: 1.0% or less, Cu: 1.0% or less, Mo: 3.0% or less is contained by the mass%, The claim 1 characterized by the above-mentioned. A method for producing an inexpensive stainless steel wire having magnetism with excellent corrosion resistance, cold workability and toughness. A low-cost stainless steel wire having magnetism excellent in corrosion resistance, cold workability, and toughness manufactured by the method according to any one of claims 1 to 4, wherein the wire is used for fasteners or machine forged parts. A low-cost stainless steel wire having magnetism excellent in corrosion resistance, cold workability, and toughness, produced by the method according to any one of claims 1 to 4, wherein the wire is used for a rope or a wire mesh / mesh product.   A low-cost stainless steel wire having magnetism excellent in corrosion resistance, cold workability, and toughness, produced by the method according to any one of claims 1 to 4, wherein the wire is used for a flat wire.