Superfine stainless steel microfilament and preparation method thereof

Abstract

The invention provides a superfine stainless steel microwire. The superfine stainless steel microwire comprises the following chemical components in percentage by mass: 0.01%-0.03% of C, 3.0%-4.0% of Ni, 22%-26% of Cr, 0.1%-0.3% of Ti and the balance of stainless steel. 0.1% to 0.3% of N, 0.15% to 0.20% of Mo; the steel comprises the following components in percentage by weight: 0.60%-0.70% of W, 0.15%-0.20% of V and the balance of Fe and inevitable impurities. By optimizing the stainless steel rolling process and exploring the bundling and drawing process, the wire breakage rate is reduced, the stainless steel microwires with high strength, corrosion resistance and excellent impact toughness are prepared, and the stainless steel microwires have market popularization prospects. Under preferable conditions, when the drawing strength reaches 1800MPa and the wire diameter is 0.01 mu m, the corrosion resistance is excellent, and the impact toughness is 30J.

Description

Technical Field

[0001] The invention relates to the technical field of metal materials, and in particular to a high-strength heat-resistant ultrafine stainless steel microwire and a preparation method thereof. Background Art

[0002] The unique preparation process of stainless steel microwires has brought about significant changes in the product structure and performance in many aspects, such as electrical conductivity, thermal conductivity, corrosion resistance, high wear resistance, stable surface performance, high strength and high ductility, excellent radiation protection, super shielding effect against electromagnetic interference, good sound absorption effect, etc., making stainless steel microwires widely used in modern industries such as petrochemicals, textiles, metallurgy, automobile manufacturing, construction, medicine, biochemicals, national defense, military and aerospace, as well as modern civil industries, to produce high-precision filter screens, shielding and sound-absorbing equipment, microwave absorption devices, battery electrodes, fiber composite reinforced materials, protective clothing, etc., and even because of the significant changes in its microstructure and the nano-scale grain size effect, some new additional characteristics that the raw materials do not have have emerged. All of this provides a broad space for expanding the application of stainless steel metal microwires.

[0003] At present, the raw materials used to produce microwires are mainly low-carbon and ultra-low-carbon stainless steel. Generally, stainless steel wires are based on 304, 304L or 316, 316L stainless steel. However, there are few stainless steel microwires made of duplex stainless steel on the market. Duplex stainless steel wire can provide better mechanical strength. The traditional rolling process is prone to wire breakage.

[0004] However, the existing alloying schemes have some defects, such as improper selection of alloying elements leading to limited performance improvement, or too high alloy costs affecting industrial applications. Therefore, it is urgent to develop a new type of high-strength heat-resistant ultra-fine stainless steel microwire, which can significantly improve strength and elongation while ensuring good corrosion resistance by optimizing the type and content of alloying elements, so as to meet the actual needs of industrial production. Summary of the invention

[0005] In view of the deficiencies in mechanical properties, impact toughness and corrosion resistance of existing stainless steel microwires, the defects of the alloying scheme optimized in this application and the high cost.

[0006] On the one hand, the present invention provides an ultrafine stainless steel microwire, the chemical composition of the ultrafine stainless steel microwire includes, by mass percentage: C: 0.01%-0.03%, Ni: 3.0%-4.0%, Cr: 22%-26%, Ti: 0.1%-0.3%; N: 0.1%-0.3%, Mo: 0.15%-0.20%; W: 0.60%-0.70%, V: 0.15%-0.20%, the balance is Fe and unavoidable impurities; The diameter of the stainless steel wire is less than 50 μm; The ultrafine stainless steel microwires are prepared by the following preparation method, which comprises the following steps: Step 1: Prepare ingredients according to the composition of ultrafine stainless steel wires, obtain ingots through smelting and casting; homogenize the ingots; then continuously roll the ingots after heat preservation until the target diameter; anneal according to conventional processes after hot rolling to finally obtain semi-finished wire rods; Step 2: Load the semi-finished wire rod into the copper tube, compact it, then draw it, and then anneal it to soften the stainless steel wire and prepare for the next drawing process; through repeated drawing and annealing to reach the required fiber diameter, ultra-fine stainless steel microwires are obtained.

[0007] Preferably, in step 1, the homogenization temperature is controlled at 1100° C.-1150° C., and the treatment time is 3-5 hours.

[0008] Preferably, in step 1, the starting rolling temperature is controlled at 1000°C-1200°C, and the final rolling temperature is controlled at 900°C-960°C.

[0009] Preferably, in step 1, the target diameter is 0.01 mm-0.05 mm; and the annealing temperature is controlled at 800° C.-900° C.

[0010] Preferably, in step 2, the diameter of the copper tube is 50 mm, and the number of cores in the copper tube is controlled to be 800-900 cores.

[0011] Preferably, in step 2, the annealing temperature is 700° C.-800° C., and the annealing speed is 10 m / min-20 m / min.

[0012] Preferably, the deformation amount in step 2 is 40%-50%.

[0013] Preferably, the chemical composition of the ultrafine stainless steel wire includes, by mass percentage: C: 0.025%, Ni: 3.8%, Cr: 25%, Ti: 0.25%; N: 0.17%, Mo: 0.17%; W: 0.68%, V: 0.17%, and the remainder is Fe and unavoidable impurities.

[0014] Preferably, the diameter of the stainless steel wire is less than 10 μm.

[0015] In a second aspect, the present application provides an application of the above-mentioned ultrafine stainless steel micro-particles in the fields of medical equipment, aerospace, automobiles and electronic products.

[0016] The ultra-fine stainless steel microwires provided in this application have the following functions: 1) The ultrafine stainless steel microwire prepared by the present invention can prepare stainless steel microwires with a wire diameter of 50 μm or less by controlling the component content and preparation process of the alloy; the synergistic effect of the Ni-Cr-Ti elements in the formula can ensure that the intergranular corrosion is reduced while ensuring the stability of the grains, thereby reducing the cost of raw materials; the addition of WV can prevent the abnormal growth of austenite grains and refine the grains during solution treatment, which is in line with the production process of stainless steel fine wires; at the same time, it can make up for the reduction in corrosion resistance and increase the elongation; tungsten is a corrosion-resistant element, and the appropriate addition of tungsten can replace part of the corrosion-resistant effect of molybdenum, thereby reducing the cost of the alloy.

[0017] 2) This application reduces the wire breakage rate by optimizing the stainless steel rolling process and exploring the bundle drawing process, and prepares stainless steel microwires with high strength, corrosion resistance and excellent impact toughness, which has market promotion prospects. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] In order to illustrate the technical solution of the present invention, specific embodiments are provided below for illustration.

[0020] In a first aspect, the present application provides an ultrafine stainless steel microwire having a chemical composition, by mass percentage, comprising: C: 0.01%-0.03%, Ni: 3.0%-4.0%, Cr: 22%-26%, Ti: 0.1%-0.3%; N: 0.1%-0.3%, Mo: 0.15%-0.20%; W: 0.60%-0.70%, V: 0.15%-0.20%, and the remainder is Fe and unavoidable impurities; In ultrafine stainless steel wires, C is an austenitizing element. Adding an appropriate amount of C to less than 0.01% will reduce the tensile strength and impact toughness of the stainless steel wire. When the C content exceeds 0.03%, carbides of elements such as Cr and C carbon are easily formed at the grain boundaries, increasing the tendency of intergranular corrosion cracking. Therefore, the C content is controlled in the range of 0.01% to 0.03%.

[0021] Ni is an austenite stabilizing element. It has a strong passivation effect. When combined with chromium, it can significantly improve corrosion resistance, tensile strength and impact toughness. However, too high a Ni content will increase the alloy cost. Therefore, the Ni content is controlled within the range of 3.0%-4.0%. While reducing costs, a reduction in the nickel content will lead to a decrease in the corrosion resistance of stainless steel wire.

[0022] Cr is the main corrosion-resistant element. Properly increasing the Cr content can improve corrosion resistance. However, too high a Cr content will reduce the stability of austenite, so the Cr content is controlled within the range of 22%-26%.

[0023] The addition of Ti element is mainly to prevent the chromium content from increasing too much, which will easily form Cr23C6 grain boundary precipitation and inhibit intergranular corrosion. Therefore, the Ti content is controlled at 0.1%~0.3%.

[0024] N is a strengthening element. Adding a proper amount of nitrogen can significantly improve the strength of the material. However, too high a nitrogen content will reduce corrosion resistance, so the nitrogen content is controlled within the range of 0.1%-0.3%.

[0025] Mo is the main corrosion resistant element, and proper addition of molybdenum can improve corrosion resistance. However, too high a molybdenum content will increase the alloy cost, so the Mo content is controlled within the range of 0.15%-0.20%, and the synergy of molybdenum and tungsten can increase the elongation.

[0026] The addition of W and V can prevent the abnormal growth of austenite grains and refine the grains during solution treatment, which is in line with the production process of stainless steel wires; at the same time, it can make up for the reduction of corrosion resistance and increase the elongation; therefore, the vanadium content is controlled at 0.05% to 0.25%; W is a corrosion-resistant element, and the appropriate addition of tungsten can replace part of the corrosion resistance of molybdenum, thereby reducing the cost of the alloy. However, too high a tungsten content will affect the stability of austenite, so the tungsten content is controlled within the range of 0.60%-0.70%.

[0027] The ultrafine stainless steel microwires are prepared by the following preparation method, which comprises the following steps: Step 1: Prepare ingredients according to the composition of ultrafine stainless steel wires, obtain ingots through smelting and casting; homogenize the ingots; then continuously roll the ingots after heat preservation until the target diameter; anneal according to conventional processes after hot rolling to finally obtain semi-finished wire rods; Specifically, according to the alloy composition, excess raw materials of each alloy element are weighed and added into a high-temperature converter, and then the ingot is formed through converter smelting, LF refining, RH or VD degassing, electromagnetic stirring, and continuous casting. By controlling the relevant parameters of converter smelting, LF refining, RH or VD degassing, and real-time sampling and analysis of the molten steel in the furnace, when the components of each element reach the preset value / range, the molten steel is poured out for electromagnetic stirring and continuous casting.

[0028] Step 2: Load the semi-finished wire rod into the copper tube, compact it, then draw it, and then anneal it to soften the stainless steel wire and prepare for the next drawing process; through repeated drawing and annealing to reach the required fiber diameter, ultra-fine stainless steel microwires are obtained.

[0029] Cluster drawing Metal fiber itself is an important functional material. Bundle drawing is the main method for the engineering preparation of micron-level metal fibers. It wraps dozens or even tens of thousands of metal wires in a cylinder for drawing, achieving simultaneous diameter reduction of multiple wires. When the fibers are drawn to the required diameter, the coating tube is peeled off to separate the fibers.

[0030] In some embodiments, the homogenization temperature in step 1 is controlled at 1100° C.-1150° C., and the processing time is 3-5 hours.

[0031] In a preferred embodiment, the homogenization temperature in step 1 is controlled at 1100° C. and the processing time is 5 hours.

[0032] In some embodiments, in step 1, the starting rolling temperature is controlled at 1000°C-1200°C, and the final rolling temperature is controlled at 900°C-960°C.

[0033] In a preferred embodiment, in step 1, the starting rolling temperature is controlled at 1180°C and the final rolling temperature is controlled at 960°C.

[0034] In some embodiments, the target diameter in step 1 is 0.01 mm-0.05 mm; and the annealing temperature is controlled at 800° C.-900° C.

[0035] In a preferred embodiment, the target diameter in step 1 is 0.01 mm; and the annealing temperature is controlled to be 900°C.

[0036] Through the exploration of the rolling process in step one, it is found that the reasonable performance of temperature and time in homogenization treatment leads to a more uniform distribution of alloy elements, especially in the high chromium system, which can eliminate component segregation and microstructural unevenness, achieve grain stabilization and grain refinement, and obtain semi-finished wire rods of specified wire diameter, which provides the possibility for the next step of bundle drawing to prepare ultra-fine wires.

[0037] In some embodiments, the diameter of the copper tube in step 2 is 50 mm, and the number of cores in the copper tube is controlled to be 800-900 cores.

[0038] In a preferred embodiment, the number of cores in the copper tube in step 2 is controlled to be 900 cores.

[0039] In some embodiments, the annealing temperature in step 2 is 700° C.-800° C., and the annealing speed is 10 m / min-20 m / min.

[0040] In a preferred embodiment, the annealing temperature in step 2 is 800° C. and the annealing speed is 20 m / min.

[0041] In some embodiments, the deformation amount in step 2 is 40%-50%.

[0042] Through the exploration of the rolling process in step two, the multi-pass drawing process can achieve a wire diameter ranging from 0.05mm to 50μm, improving the single-pass diameter reduction rate; compared with the traditional multi-mode drawing process, the copper tube packaging reduces the number of annealing times; and can reduce the wire breakage rate.

[0043] In a preferred embodiment, the chemical composition of the ultrafine stainless steel wire includes, by mass percentage: C: 0.025%, Ni: 3.8%, Cr: 25%, Ti: 0.25%; N: 0.17%, Mo: 0.17%; W: 0.68%, V: 0.17%, and the remainder is Fe and unavoidable impurities.

[0044] In some embodiments, the chemical composition of the ultrafine stainless steel wire includes, by mass percentage: C: 0.022%, Ni: 3.5%, Cr: 24%, Ti: 0.2%; N: 0.18%, Mo: 0.18%; W: 0.65%, V: 0.18%, and the remainder is Fe and unavoidable impurities.

[0045] In some embodiments, the chemical composition of the ultrafine stainless steel wire includes, by mass percentage: C: 0.03%, Ni: 4%, Cr: 23%, Ti: 0.2%; N: 0.2%, Mo: 0.2%; W: 0.7%, V: 0.17%, and the remainder is Fe and unavoidable impurities.

[0046] In some embodiments, the diameter of the stainless steel wire is less than 10 μm.

[0047] In a preferred embodiment, the diameter of the stainless steel wire is 10 μm.

[0048] In a second aspect, the present application provides an application of the above-mentioned ultrafine stainless steel micro-particles in the fields of medical equipment, aerospace, automobiles and electronic products.

[0049] The present invention is further described below by way of examples. Example 1

[0050] The invention provides a method for preparing ultrafine stainless steel microwires. The chemical components of the ultrafine stainless steel microwires include, by mass percentage, C: 0.025%, Ni: 3.8%, Cr: 25%, Ti: 0.25%, N: 0.17%, Mo: 0.17%, W: 0.68%, V: 0.17%, and the balance is Fe.

[0051] First, the raw materials of the above chemical composition are mixed in proportion and melted in a vacuum induction furnace to form molten steel. Then, the molten steel is continuously cast into billets. The billets are homogenized, that is, the billets are heated to 1100°C and kept warm for 5 hours.

[0052] Then, the billet is hot rolled with a starting rolling temperature of 1180°C, a final rolling temperature of 960°C, and an annealing temperature of 900°C, and rolled into a semi-finished wire rod of 0.01 mm.

[0053] Finally, the semi-finished wire rod is loaded into a copper tube with a diameter of 50mm, and the number of cores in the copper tube is controlled at 900 cores; the drawing process is to compact the installed copper tube and then draw it. When the deformation reaches 50%, annealing is performed to soften the stainless steel wire and prepare for the next drawing process; when the deformation reaches 50% again, annealing is performed again, the annealing temperature is 800℃, and the annealing speed is 20m / min; after 6 drawing and annealing, a stainless steel microwire with a wire diameter of 10μm is obtained. Example 2

[0054] Most of the steps of this embodiment are the same as those of Embodiment 1, except that: C: 0.022%, Ni: 3.5%, Cr: 24%, Ti: 0.2%; N: 0.18%, Mo: 0.18%; W: 0.65%, V: 0.18%. Example 3

[0055] Most of the steps of this embodiment are the same as those of Embodiment 1, except that: C: 0.03%, Ni: 4%, Cr: 23%, Ti: 0.2%; N: 0.2%, Mo: 0.2%; W: 0.7%, V: 0.17%. Example 4

[0056] Most of the steps of this embodiment are the same as those of embodiment 1, except that after drawing for 5 times, annealing is performed to obtain stainless steel microwires with a wire diameter of 50 μm. Example 5

[0057] Most of the steps of this embodiment are the same as those of embodiment 1, except that after drawing for 5 times, annealing is performed to obtain stainless steel microwires with a wire diameter of 40 μm. Example 6

[0058] Most of the steps of this embodiment are the same as those of embodiment 1, except that the blank is homogenized, that is, the blank is heated to 900° C. and kept warm for 3 hours. Example 7

[0059] Most of the steps of this embodiment are the same as those of embodiment 1, except that the blank is hot rolled with a starting rolling temperature of 1000°C and a final rolling temperature of 900°C. Example 8

[0060] Most of the steps of this embodiment are the same as those of embodiment 1, except that during the cluster drawing process, the annealing temperature is 700° C. and the annealing speed is 30 m / min.

[0061] Comparative Example 1 Most of the steps of this comparative example are the same as those of Example 1, except that V is not added.

[0062] Comparative Example 2 Most of the steps of this comparative example are the same as those of Example 1, except that W is not added.

[0063] Comparative Example 3 Most of the steps of this comparative example are the same as those of Example 1, except that Ti is not added.

[0064] Comparative Example 4 Most of the steps of this comparative example are the same as those of Example 1, except that Ni: 3.5%, Cr: 15%.

[0065] Performance Testing The ultrafine stainless steel microwires prepared in the above-mentioned embodiments and comparative examples were subjected to the following tests.

[0066] 1) Wire diameter After magnification using a high-resolution metallographic microscope (NIS-Elements), the software automatically identified the edge and calculated the diameter.

[0067] 2) Mechanical testing The mechanical properties of the samples were tested for tensile strength and elongation using a SANA CMT8102 electronic universal tensile machine. A computer connected to the electronic universal tensile machine automatically generated a force-displacement curve after taking points during the drawing process. The elongation was also directly generated by the computer. The sample gauge length was 250 mm and the tensile rate was 250 mm / min.

[0068] 3) Impact toughness According to GB / T 1817-2017, the pendulum test is used for testing. The samples must be treated with borax and should not have scratches, cracks, burrs or other dirt. The test is carried out at room temperature. 50 samples are grouped together, and the average value of 5 groups is tested in parallel.

[0069] 4) Corrosion resistance The corrosion resistance was tested by smoke test, with 5% NaCl solution, pH value between 6.5–7.2 and test temperature at 36°C; 10–20 ultra-fine stainless steel wires were arranged in parallel, fixed at both ends with polyimide tape, woven into a 1×1cm² grid (spacing 0.5mm), washed in isopropyl alcohol for 5 minutes to remove surface grease, and rinsed with deionized water 3 times; the mass loss was recorded; The above test results are shown in Table 1.

[0070] Table 1 Group Stainless steel microwire diameter (μm) Tensile strength (MPa) Elongation(%) Impact toughness (J) Corrosion resistance (μg) Example 1 10 1800 25 30 0.38 Example 2 10 1600 26 28 0.43 Example 3 10 1400 29 24 0.51 Example 4 50 1300 35 20 0.39 Example 5 40 1500 30 23 0.47 Example 6 10 1200 20 19 0.95 Example 7 10 1300 21 18 0.73 Example 8 10 1100 20 16 0.63 Comparative Example 1 10 920 10 18 1.20 Comparative Example 2 10 980 13 19 1.50 Comparative Example 3 10 870 20 15 1.60 Comparative Example 4 10 830 16 10 0.63 Combined with Comparative Examples 1-8, it can be seen that Example 1 has stronger mechanical properties and clustering toughness. The alloy formula and preparation process are both optimal. In the preparation process, temperature and time will affect the properties of the finally prepared stainless steel microfilaments.

[0071] Combined with Comparative Example 1 and Comparative Example 1, it can be seen that when vanadium element is not added, it will seriously affect the drawing strength and impact toughness of the prepared stainless steel microfilaments, and will also exacerbate intergranular corrosion, with a mass loss of 1.2 μg; and Comparative Example 2 shows that tungsten element mainly affects intergranular corrosion, and will also reduce mechanical properties due to synergistic effect; and Comparative Example 3 shows that titanium element is also the main element affecting mechanical properties and intergranular corrosion, and is essential in the alloy formula; and Comparative Example 4 shows that reducing the content of chromium element mainly affects the mechanical properties of stainless steel microfilaments.

[0072] In summary, the stainless steel microfilaments produced by the alloy formula and preparation method provided by the present invention have a drawing strength of 1800 MPa under preferred conditions, a wire diameter of 0.01 μm, excellent corrosion resistance, an impact toughness of 30 J. On the basis of the original process, by improving the element content, pass deformation amount and solution temperature, a product with excellent properties is obtained. The process is simple and suitable for industrial production.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. An ultra-fine stainless steel microwire, characterized in that: The chemical composition of the ultrafine stainless steel microwire includes, by mass percentage: C: 0.01%-0.03%, Ni: 3.0%-4.0%, Cr: 22%-26%, Ti: 0.1%-0.3%; N: 0.1%-0.3%, Mo: 0.15%-0.20%; W: 0.60%-0.70%, V: 0.15%-0.20%, and the balance is Fe and unavoidable impurities; The diameter of the ultra-fine stainless steel microwire is less than 50 μm; The ultrafine stainless steel microwires are prepared by the following preparation method, which comprises the following steps: Step 1: Prepare ingredients according to the composition of ultrafine stainless steel wires, obtain ingots through smelting and casting; homogenize the ingots; then continuously roll the ingots after heat preservation until the target diameter; anneal according to conventional processes after hot rolling to finally obtain semi-finished wire rods; Step 2: Load the semi-finished wire rod into the copper tube, compact it, then draw it, and then anneal it to soften the stainless steel wire and prepare for the next drawing process; through repeated drawing and annealing to reach the required fiber diameter, ultra-fine stainless steel microwires are obtained.

2. The ultra-fine stainless steel microwire according to claim 1, characterized in that: In step 1, the homogenization temperature is controlled at 1100° C.-1150° C., and the processing time is 3-5 hours.

3. The ultra-fine stainless steel microwire according to claim 1, characterized in that: In step 1, the starting rolling temperature is controlled at 1000°C-1200°C, and the final rolling temperature is controlled at 900°C-960°C.

4. The ultra-fine stainless steel microwire according to claim 1, characterized in that: The target diameter in step 1 is 0.01 mm-0.05 mm; the annealing temperature is controlled at 800° C.-900° C.

5. The ultra-fine stainless steel microwire according to claim 1, characterized in that: The diameter of the copper tube in step 2 is 50 mm, and the number of cores in the copper tube is controlled at 800-900 cores.

6. The ultra-fine stainless steel microwire according to claim 1, characterized in that: In step 2, the annealing temperature is 700° C.-800° C., and the annealing speed is 10 m / min-20 m / min.

7. The ultra-fine stainless steel microwire according to claim 1, characterized in that: The deformation amount in the second pass is 40%-50%.

8. The ultra-fine stainless steel microwire according to claim 1, characterized in that: The chemical composition of the ultrafine stainless steel microwire includes, by mass percentage, C: 0.025%, Ni: 3.8%, Cr: 25%, Ti: 0.25%, N: 0.17%, Mo: 0.17%, W: 0.68%, V: 0.17%, and the remainder is Fe and unavoidable impurities.

9. The ultra-fine stainless steel microwire according to claim 1, characterized in that: The wire diameter of the stainless steel wire is less than 10 μm.

10. An application of the ultrafine stainless steel microwire according to any one of claims 1 to 9 in the fields of medical devices, aerospace, automobiles and electronic products.