CN113073265A - 301 superhard precision stainless steel with greatly improved strength and service life and application thereof - Google Patents
301 superhard precision stainless steel with greatly improved strength and service life and application thereof Download PDFInfo
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/30—Stress-relieving
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
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- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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Abstract
The invention discloses a 301 superhard precision stainless steel with greatly improved strength and service life and application thereof, wherein the 301 superhard precision stainless steel is prepared by a steel strip blank through semi-finished product cogging rolling, finished product rolling and stress relief processes in sequence; the total rolling reduction rate of the semi-finished product cogging rolling is 55-65%, the rolling speed of the first two passes of the semi-finished product cogging rolling is less than or equal to 60 m/min, the rolling speed of the rest passes is less than or equal to 100 m/min, and instantaneous jump of acceleration and deceleration is avoided when the rolling speeds are switched. Through comprehensive adjustment of chemical components, semi-finished cogging rolling, finished product rolling and stress relief of a steel strip blank, 301 superhard precise stainless steel with high strength, high hardness and long service life compared with the prior art is obtained, and the stainless steel can be applied to various precise coil springs, precise elastic gaskets and various precise elastic elements, meets the requirements of the market on superhard stainless steel materials, solves the technical bottleneck of domestic 301 precise stainless steel strips, and replaces imported products.
Description
Technical Field
The invention belongs to the technical field of stainless steel precision steel strip manufacturing, and particularly relates to a method for greatly improving the strength and service life of 301 superhard precision stainless steel, 301 superhard precision stainless steel and application thereof.
Background
The 301 stainless steel is metastable austenite stainless steel, and the 301 precision cold-rolled stainless steel band has the characteristics of high hardness, high strength, high fatigue resistance, wide use industry, high added value, less unit dosage and the like, and is used for automobiles, electronic products, spring steel sheets, railway carriages or other fields needing high hardness and high strength. Among stainless steels, austenitic stainless steel has cold deformation strengthening characteristics, and precision cold-rolled stainless steel strips are steel strips with various hardness and strength (mechanical properties) obtained by controlling cold deformation (cold rolling reduction) by utilizing the characteristics. The production process of the austenite precision cold-rolled stainless steel strip comprises the following steps: (1) smelting qualified stainless steel in a steel plant; (2) hot rolling, or cold rolling, or "hot rolling + cold rolling"; (3) rolling the stainless steel billet into a stainless steel precision steel strip blank with the thickness of less than 1.5 mm; (3) the precision cold rolling process design is carried out, the steel belt blank is processed into a stainless steel precision steel belt finished product blank (namely a semi-finished product), and then the stainless steel precision steel belt finished product blank is processed into a stainless steel precision steel belt finished product. The precision cold-rolled stainless steel strip has high production technical requirements, not only has accurate size, but also can ensure the required mechanical performance index. Important factors for ensuring the mechanical property index of the precision cold-rolled stainless steel strip include the chemical composition of the steel strip blank for finish rolling and the precision cold-rolling process.
Due to the micro-fluctuation of chemical components, the steel strip blanks provided by the same supplier still have the errors of Vickers hardness smaller than +/-8 units by adopting the same precision cold rolling process, so the selection of the chemical components of the steel strip blanks for finish rolling has great influence on the mechanical properties of the finish rolled steel strip. The composition (chemical composition) range of 301 stainless steel in the disclosed data is defined as including, in weight percent: c: less than or equal to 0.15; si is less than or equal to 1.0; mn is less than or equal to 2.0; p is less than or equal to 0.045; s is less than or equal to 0.03; cr: 16.0 to 18.0; ni: 6.0-8.0; the balance being Fe and other unavoidable impurity elements. Stainless steel billets with corresponding mechanical properties can be obtained through adjustment of components and improvement of processes, for example, Chinese patent application No. CN201910546793.X, application No. 2019.06.24, No. CN110218852B, No. 2020.12.22 discloses a 301 stainless steel production method, 301 stainless steel and application, and the patent application discloses 301Si stainless steel which comprises the following chemical components in percentage by weight: c: 0.1 to 0.12; 1.15-1.35% of Si; 1.3-1.6 parts of Mn; p is less than or equal to 0.035; s is less than or equal to 0.004; cr: 16.2 to 16.7; ni: 6.5-6.7; n: less than or equal to 0.03; mo is less than or equal to 0.3, and the balance is Fe and other inevitable impurity elements; the 301SiMo stainless steel comprises the following chemical components in percentage by weight: c: 0.1 to 0.12; 1.15-1.35% of Si; 1.3-1.6 parts of Mn; p is less than or equal to 0.035; s is less than or equal to 0.004; cr: 16.2 to 16.7; ni: 6.5-6.7; n: less than or equal to 0.03; 0.5-0.8% of Mo, and the balance of Fe and other inevitable impurity elements; the above chemical components are combined with the production process of the scheme to obtain 301Si stainless steel with Vickers Hardness (HV) of 206 and 301SiMo stainless steel with Vickers Hardness (HV) of 202, and the 301 precision cold-rolled stainless steel band with Vickers Hardness (HV) of more than 500HV is obtained by precision rolling and tempering treatment.
The precision cold rolling process is the key for ensuring the quality of stainless steel precision steel strips, and the key of the precision cold rolling process design in the prior art is the final rolling deformation (the final rolling deformation is the most main cold rolling process parameter; the final rolling deformation refers to the stainless steel precision steel strip finished blank thickness → the finished product thickness cold rolling deformation). Chinese patent application, application No. CN200810038105.0, application date 2008.05.27, grant No. CN101320031B, grant No. 2012.09.26, discloses a model for predicting the performance of austenitic stainless steel precision steel strip and its cold rolling process design, which is an introduction to the cold rolling process of 301 precision cold-rolled stainless steel strip, and the technical scheme discloses the chemical components of stainless steel strip: 0.01-0.30% of carbon, 0-2.0% of silicon, 0-2% of manganese, less than or equal to 0.045% of phosphorus, less than or equal to 0.030% of sulfur, 0-42.0% of nickel, 10.0-26.0% of chromium, 0-4.0% of molybdenum, 0-0.3% of nitrogen, 0-0.5% of titanium and 0-0.5% of niobium; the rolling mode is as follows: 1-10 rolling passes, 30-360 m/min rolling speed and 5-80% of final rolling deformation; the product performance is as follows: the tensile strength is 350-2100 MPa, the yield strength is 250-1900 MPa, the elongation is 0-70%, and the Vickers hardness is 135-600 units; product thickness: 0.03-1.1 mm. This patent application discloses a precision rolling process for 300 series and 400 series stainless steel strip which can achieve a vickers hardness of up to 600 HV.
The disadvantages are that: the Vickers Hardness (HV) obtained by CN201910546793.X and CN200810038105.0 patent applications is below 600HV, and the chemical compositions (including 300 series and 400 series stainless steel) and performance data disclosed by the latter are only summarized by the experience of the technicians in the field on new stainless steel series, and the technical scheme that the Vickers hardness can reach above 600 in the production practice is not reported; in addition, the strength and the service life of the 301 stainless steel precision steel band provided by the prior art can not be considered at the same time, some 301 stainless steel precision cold-rolled bands have high strength but low service life, and other 301 stainless steel precision cold-rolled bands have high service life but low strength, so that the market high-end requirements on the 301 stainless steel precision steel band with high hardness, high strength and long bending service life in the fields of various precision coil springs, precision elastic gaskets and various precision elastic elements are difficult to meet.
Therefore, the technical problem to be solved by those skilled in the art is how to design a 301 superhard precision stainless steel which has both high strength and long bending life.
Disclosure of Invention
1. Technical problem to be solved
Aiming at the problems that the Vickers hardness of the 301 stainless steel precision steel strip disclosed in the prior art can reach up to 600HV, the strength and the service life can not be simultaneously considered, and the market high-end requirements of the 301 stainless steel precision steel strip with high hardness, high strength and long bending service life in the fields of various precision coil springs, precision elastic gaskets and various precision elastic elements are difficult to meet, the invention aims to provide a method for greatly improving the strength and the service life of 301 superhard precision stainless steel, 301 superhard precision stainless steel and application thereof, through improving the chemical components of a steel strip blank for precision rolling and a precision cold rolling process, the hardness and the strength of the 301 precision stainless steel strip are greatly improved, the service life of the 301 precision stainless steel strip is prolonged, the 301 precision stainless steel strip can be applied to various precision coil springs, precision elastic gaskets and various precision elastic elements, the market requirements of the superhard stainless steel material are met, and the technical bottleneck of the domestic 301 precision stainless steel strip is solved, replacing imported products.
2. Technical scheme
In order to achieve the purpose and achieve the technical effect, the invention adopts the following technical scheme:
the 301 superhard precision stainless steel with greatly improved strength and service life is characterized in that the 301 superhard precision stainless steel is prepared by a steel strip blank through the processes of semi-finished cogging rolling, finished rolling and stress relief in sequence; the total rolling reduction rate of the semi-finished product cogging rolling is 55-65%, the rolling speed of the first two passes of the semi-finished product cogging rolling is less than or equal to 60 m/min, the rolling speed of the rest passes is less than or equal to 100 m/min, and instantaneous jump of acceleration and deceleration is avoided when the rolling speeds are switched.
In a specific embodiment of the invention, the total reduction rate of the semi-finished cogging rolling is 56-60%.
In a specific embodiment of the invention, the total reduction rate of the finished product rolling is 70-75%, 8-10 passes of rolling are adopted, the first pass reduction rate is less than or equal to 20%, the reduction rates of other passes are sequentially decreased progressively, the reduction rates of the last two passes are respectively less than or equal to 8% and less than or equal to 6%, wherein the rolling speed of the first four passes is less than or equal to 60 m/min, and the rolling speed of the remaining passes is less than or equal to 90 m/min.
In a specific embodiment of the invention, the working oil temperature of the finished product rolling is 47-53 ℃, and preferably 50 ℃.
In a specific embodiment of the invention, the temperature of the stress relief process is about 300 ℃, the speed is 1.0TV value, the TV value is thickness speed, i.e. 0.1mm steel strip is subjected to stress relief production at 10 m/min, 0.2mm steel strip is subjected to stress relief production at 5 m/min; the cooling mode is slow cooling, and the tapping temperature of the strip steel is 50-60 ℃.
In a specific embodiment of the invention, the steel strip blank comprises the following chemical components in percentage by weight: c: 0.100-0.110; mn: 0.700-0.800; s: 0.001-0.004; p: 0.02-0.04; si: 0.600-0.800; cr: 16.100-16.400; ni: 6.500-6.800; mo: 0.06-0.09; n: 0.01-0.015; cu: 0.100-0.200; the balance being Fe.
In a specific embodiment of the invention, the steel strip blank comprises the following chemical components in percentage by weight: c: 0.103-0.107; mn: 0.750-0.800; s: 0.001-0.004; p: 0.02-0.04; si: 0.650-0.750; cr: 16.200-16.400; ni: 6.700-6.800; mo: 0.070-0.080; n: 0.011-0.013; cu: 0.100-0.150; the balance being Fe.
The invention adopts the following optimized analysis of the functions and components of various elements:
carbon is an element that strongly forms and stabilizes austenite and expands the austenite region in austenitic stainless steels. Carbon forms 30 times as much austenite as nickel. Carbon is used as an interstitial element, and the strength of the austenitic stainless steel can be remarkably improved through solid solution strengthening. Therefore, the strength of austenitic stainless steel is improved as the C content in the steel increases, and the C content is preferably 0.103 to 0.107.
Cr is an element necessary for ensuring the corrosion resistance of the stainless steel, and increasing the Cr content can improve the corrosion resistance of the stainless steel, but too much Cr content can cause too much ferrite to be formed in the stainless steel, so that the stainless steel cannot be ensured to have sufficient tensile elongation, and the service life of the stainless steel can be influenced. Therefore, the invention preferably has the Cr content of 16.200-16.400 on the premise of not changing the corrosion resistance of the stainless steel, and ensures that the precision stainless steel strip has higher elongation.
Ni: nickel is an alloying element that forms austenite, but the role of nickel is fully exerted only when it is combined with chromium. When nickel and chromium are combined, the effect of nickel on improving the corrosion resistance of steel is remarkably exhibited. The mechanical property of the precision stainless steel band is improved by adding a small amount of nickel into the ferritic stainless steel, so that the metallographic structure is changed from single-phase ferrite to ferrite and austenite, and the Ni content is preferably 6.700-6.800.
Si: silicon is an element for forming ferrite, has a certain solid solution strengthening effect, has a certain optimization effect on the oxidation resistance of the material, and simultaneously enhances the pitting corrosion resistance of the precision stainless steel strip, wherein the content of Si is preferably 0.650-0.750.
Mn: manganese is one of the substitute elements for nickel, and manganese, like nickel, is an alloying element that forms austenite. However, manganese does not play a role in forming austenite, but rather, it reduces the critical quenching speed of steel, increases the stability of austenite upon cooling, inhibits the decomposition of austenite, and maintains austenite formed at high temperature to normal temperature, and the Mn content is preferably 0.750 to 0.800.
N is an austenite stabilizing element and can improve the strength. The art generally considers that the tensile strength of the 301 superhard material can be improved by increasing the content of N, but in practice, the content of N is too high, the toughness of the 301 superhard material is sacrificed although the tensile strength of the superhard material is increased, and the superhard material is more susceptible to brittle fracture while the strength of the superhard material is greatly improved, so that the service life of the superhard material is not up to the standard. The invention theoretically sacrifices certain strength but improves the service life of the product by micro-adjusting the N content, wherein the N content is preferably 0.011-0.013.
Cu: the copper element is properly added, so that the service life of the steel strip is prolonged, the bending effect is improved, the second precipitation amount during stress relief at about 300 ℃ is increased, and the product forming is facilitated, but the copper element is too much, so that the service life of the steel strip is prolonged, the bending effect is improved, and the use strength of the steel strip is reduced. The copper content of the invention is preferably 0.100-0.150, theoretically sacrificing a certain strength, but improving the service life thereof.
Mo: n and Cu can theoretically greatly improve the service life of the 301 superhard material, but sacrifice and reduce the strength of the 301 superhard material. The invention limits the content of Mo while limiting the content of N and Cu. Mo not only can obviously improve the strength and the hardness, make up the strength deficiency caused by limiting the content of N and the content of Cu, but also can enhance the secondary hardening effect so as to further improve the use strength of the alloy, and is especially obvious when the alloy is subjected to stress relief tempering at about 300 ℃. The Mo content is preferably from 0.070 to 0.080.
In a specific embodiment of the invention, the steel strip blank steel mill smelts qualified stainless steel, the tensile strength of the steel strip blank is more than 1050MPa, the yield strength is more than 300MPa, and the hardness is more than 200 HV; the tolerance of the length direction and the width of the steel strip blank is less than 0.15 mm.
It is another object of the present invention to provide the use of the above 301 superhard precision stainless steel with greatly improved strength and life in precision coil springs and precision elastomeric shims and precision elastomeric elements.
3. Advantageous effects
Compared with the prior art, the invention has the following beneficial effects:
1) through the adjustment of the components of the steel strip blank, the content proportion of Mo, N, Cu and Cr is optimized, the secondary hardening effect is enhanced, and the tensile strength, toughness, hardness, service life and bending effect of the 301 superhard precision stainless steel strip are remarkably improved.
2) By optimizing the cogging process of the semi-finished product, reasonably selecting the cogging reduction rate of the semi-finished product and strictly controlling the cogging speed of the semi-finished product, the tensile strength, toughness, hardness, service life and bending effect of the finished product are obviously improved, and the stability of the performance of the finished product is ensured.
3) The finished product rolling process fully considers the sensitivity of cold working of a 301 material to temperature, and the first pass does not adopt large reduction rate, so that the tensile strength, toughness, hardness, service life and bending effect of the finished product are obviously improved again on the basis of the original process; the final two passes of reduction rate is as small as possible, and is controlled within 8% and 6% to ensure that good thickness precision and uniform internal grain structure are obtained, otherwise product forming and service life are affected.
4) The stress relief process focuses on the furnace temperature and speed, and meanwhile, the cooling mode is deeply researched, so that the related influence of the cooling mode on the performance of the superhard material is determined; through the control of the cooling mode, products with special requirements can be customized in a targeted manner.
5) Through comprehensive adjustment of chemical components, semi-finished cogging rolling, finished product rolling and stress relief of a steel strip blank, 301 superhard precise stainless steel with high strength, high hardness and long service life compared with the prior art is obtained, and the stainless steel can be applied to various precise coil springs, precise elastic gaskets and various precise elastic elements, meets the requirements of the market on superhard stainless steel materials, solves the technical bottleneck of domestic 301 precise stainless steel strips, and replaces imported products.
Detailed Description
In order to make the object, technical solution and technical effect of the present invention more apparent, the present invention will be further described with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Comparative example 1
Chinese patent application, application No. CN200810038105.0, application No. 2008.05.27, grant No. CN101320031A, grant No. 2008.12.10, disclose a prediction model of austenitic stainless steel precision steel strip performance and its cold rolling process design, this technical scheme discloses the chemical composition of the raw materials: 0.096% of carbon, 0.87% of silicon, 1.12% of manganese, less than or equal to 0.024% of phosphorus, less than or equal to 0.002% of sulfur, 9.94% of nickel, 16.99% of chromium, 0.035% of nitrogen and 0.31% of molybdenum; the thickness of the raw material is 1.5mm, the thickness after rolling is 0.5mm, the deformation of final rolling is 66.7%, the width of the raw material is 628mm, and the Vickers hardness is 329.
Comparative example 2
Chinese patent application, application No. CN200810038105.0, application No. 2008.05.27, grant No. CN101320031A, grant No. 2008.12.10, disclose a prediction model of austenitic stainless steel precision steel strip performance and its cold rolling process design, this technical scheme discloses the chemical composition of the raw materials: 0.12 percent of carbon, 0.54 percent of silicon, 0.57 percent of manganese, less than or equal to 0.029 percent of phosphorus, less than or equal to 0.007 percent of sulfur, 6.68 percent of nickel and 16.62 percent of chromium; the thickness of the raw material is 1.2mm, the thickness after rolling is 0.245mm, the deformation of the final rolling is 79.6 percent, the width of the raw material is 628mm, and the Vickers hardness is 554.
The invention provides a 301 superhard precision stainless steel with greatly improved strength and service life, which is characterized in that the 301 superhard precision stainless steel is prepared by a steel strip blank through the processes of semi-finished cogging rolling, finished rolling and stress relief in sequence; the total rolling reduction rate of the semi-finished product cogging rolling is 55-65%, preferably 56-60%, the rolling speed of the first two passes of the semi-finished product cogging rolling is less than or equal to 60 m/min, the rolling speed of the rest passes is less than or equal to 100 m/min, and instantaneous jump of acceleration and deceleration is avoided when the rolling speeds are switched.
The total reduction rate of the finished product is 70-75%, 8-10 passes of rolling are adopted, the first pass of rolling is less than or equal to 20%, the reduction rates of other passes of rolling are sequentially decreased, the final two passes of rolling are respectively less than or equal to 8% and less than or equal to 6%, wherein the rolling speed of the first four passes of rolling is less than or equal to 60 m/min, and the rolling speed of the rest passes of rolling is less than or equal to 90 m/min; the temperature of the working oil is 47-53 ℃, and preferably 50 ℃.
The temperature of the stress relief process is about 300 ℃, the speed is 1.0TV value, the TV value is thickness speed, namely 0.1mm steel strip is subjected to stress relief production at 10 m/min, and 0.2mm steel strip is subjected to stress relief production at 5 m/min; the cooling mode is slow cooling, and the tapping temperature of the strip steel is 50-60 ℃.
Comparative experiment 1
The steel strip blank is selected from numbers QXM0521A and QWM2007A, the thickness of the steel strip blank is 1.477 and 1.220mm respectively, and the chemical compositions by weight percentage comprise: c: 0.104; mn: 0.714 of the total weight of the mixture; s: 0.0038; p: 0.0282; si: 0.700 of; cr: 16.22; ni: 6.53; mo: 0.08; n: 0.014; cu: 0.103; the balance being Fe. Under the conditions that the thickness of the finished product is 0.18mm, the rolling process and the stress relief process of the finished product are not changed, only the cogging rolling process of the semi-finished product is different, and a comparison test is carried out:
the first scheme is as follows: the semi-finished product is rolled from 1.477mm to 0.60mm, and the reduction rate is 59.38%;
scheme II: the semi-finished product is rolled from 1.220mm to 0.60mm, and the reduction rate is 50.82%; the finished products are rolled from 0.60mm to 0.18mm, and the test data are as follows:
| class of test | Scheme one | Scheme two |
| Hardness of 0.18mm finished product (HV) | 621 | 607 |
| 0.18mm finished product tensile strength (MPa) | 2236.47 | 2049.72 |
| Hand feeling bending test | Does not break when bent by 180 degrees | 180 degree bend fracture |
| Life test (times) | 4100 breaks | 2800 breaks |
Through the comparative analysis of the test results in the table above, the reasonable selection of the cogging rolling reduction of the semi-finished product has great influence on the performance of the semi-finished product, and the cogging rolling process of the semi-finished product in the scheme one is superior to that in the scheme two.
Analyzing test data of a scheme I and a scheme II:
the total rolling reduction rate of the semi-finished product cogging rolling is accurately controlled to be 55-65%. For example, if the thickness of the raw material is 1.5mm, the thickness of the semi-finished product is controlled between 0.525mm and 0.675mm, preferably about 56% to 60%. When the rolling deformation (reduction) is less than 30%, the inside of the metal only slips on the surface layer, that is, the crystals on the surface layer inside are damaged to generate slip. When the cogging deformation is more than 30% and less than 55%, the crystal in the metal slides unevenly, so that the internal crystal grain structure is uneven during annealing and recrystallization, the grain size grade is lower than 5 grade, and the service life and the tensile strength of a finished product are seriously influenced; the rolling deformation is more than 65 percent, the internal crystal is fully damaged, but the deformation texture is easily generated, and the influence of the texture is difficult to eliminate during intermediate annealing recrystallization, so that the abnormal forming of products is caused, and the service life is relatively short. In addition, the rolling speed of the semi-finished cogging rolling needs to be properly controlled, the rolling speed of the first two passes of the semi-finished cogging rolling is less than or equal to 60 m/min, and the rolling speed of the rest passes is less than or equal to 100 m/min, so that the thickness precision of the finished product is ensured. The heat of the steel strip in the length direction and the width direction is uneven due to too high speed, the steel strip and related equipment expand with heat and contract with cold unevenly, and the thickness jump is easy to cause to be large; meanwhile, the acceleration and the deceleration are stable, and the thickness instant jump caused by the over-rapid acceleration and the deceleration (the over-large instant acceleration) is avoided.
Comparative experiment 2
The components and the thickness of the steel strip blank, the thickness of the semi-finished product after cogging and the thickness of the finished product after stress relief are the same, and only the rolling process of the finished product is different. The thickness of the steel strip blank is 0.450mm, and the target thickness of the finished product is 0.135 mm.
The third scheme is as follows: the rolling total reduction rate of the finished product is about 70 percent. The steel strip blank is rolled from 0.450mm to the target thickness of a finished product of 0.135mm, the rolling is carried out by adopting 8 passes in total, the process speed of the first four passes is less than or equal to 60 m/min, the process speed of the last four passes is less than or equal to 90 m/min, and the rolling oil temperature is controlled between 47-53 ℃. The rolling pass reduction distribution is as follows:
and the scheme is as follows: the selectable range of the total rolling reduction rate of the finished product is 70% -75%, on the premise of ensuring the service life, if the elasticity of the precision elastic element needs to be increased, the total rolling reduction rate is correspondingly increased, but the total rolling reduction rate is not more than 75%, otherwise, the whole brittle failure accident is easy to occur in the rolling process. According to the scheme, the total reduction rate of 70% is adopted, the rolling is carried out for 8 passes, the first pass reduction rate is less than or equal to 20%, the reduction rates of other passes are sequentially decreased, the final two passes reduction rates are respectively less than or equal to 8% and less than or equal to 6%, wherein the rolling speed of the first four passes is less than or equal to 60 m/min, and the rolling speed of the rest passes is less than or equal to 90 m/min. The working oil temperature for finished product rolling is 47-53 ℃, and preferably 50 ℃. The rolling pass reduction distribution is as follows:
and (3) testing the tensile strength, the yield strength and the hardness of the finished stainless steel belts of the third scheme and the fourth scheme, wherein the results are as follows:
| 0.135mm relevant main technical parameter of finished product | Scheme three | Scheme four |
| Tensile strength of finished product | 1932.35MPa | 2187.56MPa |
| Yield strength of finished product | 1809.47MPa | 2083.83MPa |
| Hardness of finished product | 601HV | 617HV |
The comparison shows that the components and the thickness of the steel strip blank, the thickness of the semi-finished product after cogging and rolling and the thickness of the finished product after stress relief are the same, the finished product rolling process is different, the parameters of the 301 precision stainless steel strip have obvious difference, and the finished product rolling process of the scheme four is superior to the scheme three.
On the basis of the fourth scheme, the required strength is further improved, and under the condition that the total reduction rate is not changed, by increasing the pass rolling, for example, eight passes are changed into nine passes, higher hardness and strength can be further obtained.
Comparative experiment 3
Under the condition that the steel strip blank components, the semi-finished cogging rolling process and the finished rolling process are the same and only the stress relief process is different, the method is compared with the existing stress relief process as follows.
And a fifth scheme: the furnace temperature is about 300 ℃, the speed is 1.0TV value, namely 0.1mm steel strip is subjected to stress relief production at a rate of 10 m/min, and 0.2mm steel strip is subjected to stress relief production at a rate of 5 m/min; the cooling speed is controlled to ensure that the tapping temperature of the strip steel is 20 ℃.
Scheme six: the furnace temperature is about 300 ℃ and the speed is 1.0TV value; the cooling speed is controlled to ensure that the tapping temperature of the strip steel is 40 ℃.
The scheme is seven: the furnace temperature is about 300 ℃, the speed is 1.0TV value, the cooling mode is slow cooling, and the strip steel tapping temperature is 50-60 ℃.
Note: under the condition that the speed is the same as the furnace temperature, the cooling speed is reflected by the high and low tapping temperatures, the cooling speed is slow when the tapping temperature is high, and the cooling speed is fast when the tapping temperature is low.
Selecting the same steel coil with the thickness of 0.135mm obtained by the finished product rolling process of the fourth scheme in the comparative experiment 2, and testing the following relevant data by using three different cooling modes:
| class of test | Scheme seven | Scheme six | Scheme five |
| Hardness (HV) | 604 | 609 | 617 |
| Tensile strength (MPa) | 2139.30 | 2159.68 | 2203.47 |
| Bending condition of hand feeling | Does not break when bent by 180 degrees | Does not break when bent by 180 degrees | 180 degree bend fracture |
| Life test (times) | 5100 times of fracture | 4300 breaks | 3400 breaks |
Scheme five, adopting 20 parts of tapping temperature not higher than room temperature℃，The stress-relief cooling speed is high, the tensile strength higher than that of the scheme six and the scheme seven is obtained, and the service life is shortest.
And in the sixth scheme, the drawing temperature is about 40 ℃, the stress-relief cooling speed is moderate, the tensile strength is higher than that in the seventh scheme and lower than that in the fifth scheme, and the service life is medium.
And in the seventh scheme, the tapping temperature is 60 ℃, the stress-relief cooling speed is the slowest, and the tensile strength and the service life higher than those of the fifth scheme and the sixth scheme are obtained.
The comparison shows that different cooling modes of the stress relief annealing process have great influence on the tensile strength and the service life of the strip steel, and the seventh scheme can simultaneously give consideration to high strength, high hardness and long service life.
Comparative experiment 4
The steel strip blank comprises the following chemical components in percentage by weight: c: 0.100-0.110; mn: 0.700-0.800; s: 0.001-0.004; p: 0.02-0.04; si: 0.600-0.800; cr: 16.100-16.400; ni: 6.500-6.800; mo: 0.06-0.09; n: 0.01-0.015; cu: 0.100-0.200; the balance being Fe. Preferably, the steel strip blank comprises the following chemical components in percentage by weight: c: 0.103-0.107; mn: 0.750-0.800; s: 0.001-0.004; p: 0.02-0.04; si: 0.650-0.750; cr: 16.200-16.400; ni: 6.700-6.800; mo: 0.070-0.080; n: 0.011-0.013; cu: 0.100-0.150; the balance being Fe. The production process provided by the invention is adopted when the steel strip blanks have different chemical compositions, and the comparative test is as follows:
from the comparative analysis of the components of the test data, it can be seen that:
1. compared with the component of the component A1002563, the component QWM1813C obviously and greatly doubles the contents of Mo and Cu, and properly reduces the contents of Cr and N. The reasonable adjustment and matching of the trace elements play a key role in the strength and the service life of the superhard material.
2. From the above test data, the product having the QWM1813C component has improved tensile strength and hardness before stress relief compared with the product having the A1002563 component, and has an average tensile strength increased by about 70MPa and an average hardness increased by about 13 HV. However, after the stress is relieved at about 300 ℃, the tensile strength and the hardness of the product prepared by the QWM1813C composition are obviously improved, the difference between the tensile strength and the hardness of the product prepared by the A1002563 composition is further widened, and the difference between the tensile strength and the hardness is widened to about 140MPa and 17HV respectively. The reason is that the large increment of Mo not only can obviously improve the strength and the hardness to make up the strength deficiency caused by the reduction of N content and the increase of Cu content, but also can enhance the secondary hardening effect to further improve the service strength, and is particularly obvious when the secondary stress tempering is carried out at about 300 ℃. The practical result is completely consistent with theoretical deduction, and the hardness and the tensile strength are obviously improved on the original basis.
3. In the aspect of use occasions, the product is a domestic highest-end curtain coil spring, the requirement on the service life is very high, otherwise, when the curtain is frequently pulled up and down every day, if the service life of the coil spring is not enough, fatigue fracture occurs, and the curtain directly falls down. Through a life test, the product prepared from the A1002563 composition breaks just at about 3500 times of critical points required by use. The product made of the QWM1813C component is broken only after reaching 5000 times of test, and the service life is greatly prolonged. This is mainly due to the result that the Cu content is greatly increased, while the N content is further finely reduced.
4. Through the composition improvement, the steel strip blank which meets the requirements of tensile strength and service life and is greatly improved is achieved at the source.
Comparative experiment 5
The steel strip blank and the production process are improved by a comparative example, and the test process comprises the following steps: the raw materials have different components, the rolling process of the finished product is different, and the cogging process and the destressing process of the semi-finished product are the same.
Composition No. a0002173 was as follows: c: 0.109; mn: 0.753; s: 0.002; p: 0.025; si: 0.725; cr: 16.429, respectively; ni: 6.781, respectively; mo: 0.008; n: 0.013; cu: 0.022; the balance being Fe. Raw material specification: 1.45 × 1219, weight 10997 kg; and (3) test results: the thickness of the finished product is 0.18mm, and 4 finished steel coils are produced. The existing finished product rolling process is adopted;
the ingredients with the number of QXM0521A are as follows: c: 0.104; mn: 0.714 of the total weight of the mixture; s: 0.0038; p: 0.0282; si: 0.700 of; cr: 16.22; ni: 6.53; mo: 0.08 (10 times larger); n: 0.014; cu: 0.103; the balance being Fe. Raw material specification: 1.477 x 1219, weight 18474 kg; and (3) test results: the thickness of the finished product is 0.18mm, and 8 finished steel coils are produced. The finished product rolling process is adopted; the test data are shown in the following table:
| class of test | Existing sourceMaterial and Process A0002173 | The invention relates to a raw material and a process QXM0521A |
| Hardness (HV) | 593 | 621 |
| Tensile strength (Mpa) | 1902.38 | 2236.47 |
| Bending condition of hand feeling | Does not break when bent by 180 degrees | Does not break when bent by 180 degrees |
| Life test (times) | 3100 fractures | 4100 breaks |
Comparative test 6
The ingredients with the number A2002574 are as follows: c: 0.105; mn: 0.744; s: 0.001; p: 0.035; si: 0.683; cr: 16.44; ni: 6.694, respectively; mo: 0.015; n: 0.013; cu: 0.033; the balance being Fe. Raw material specification: 1.00 x 1219, weight 14642 kg; and (3) test results: the thickness of the finished product is 0.15mm, and 4 finished steel coils are produced. The existing process is adopted.
The numbering QWM1706A is as follows: c: 0.104; mn: 0.714 of the total weight of the mixture; s: 0.0038; p: 0.0282; si: 0.700 of; cr: 16.22; ni: 6.53; mo: 0.08; n: 0.014; cu: 0.103; the balance being Fe. Raw material specification: 1.220 x 1219, weight 21295 kg; and (3) test results: the thickness of the finished product is 0.15mm, and 8 finished steel coils are produced. With the process of the invention, the test data are shown in the following table:
| class of test | Existing raw materials and process A2002574 | The invention relates to a raw material and a process QWM1706A |
| Hardness (HV) | 596 | 629 |
| Tensile strength (Mpa) | 1858.28 | 2243.84 |
| Bending condition of hand feeling | Does not break when bent by 180 degrees | Does not break when bent by 180 degrees |
| Life test (times) | 2900 breaks | 4200 times of fracture |
The production process of the invention can obtain the 301 superhard precision stainless steel which has higher strength, high hardness and long service life when the batch chemical components, the semi-finished product cogging process, the finished product rolling process and the stress relief process of the steel strip are different.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (8)
1. 301 superhard precision stainless steel of intensity and life-span is improved by a wide margin, its characterized in that: the 301 superhard precision stainless steel is prepared by a steel strip blank through the processes of semi-finished product cogging rolling, finished product rolling and stress relief in sequence; the total rolling reduction rate of the semi-finished product cogging rolling is 55-65%, the rolling speed of the first two passes of the semi-finished product cogging rolling is less than or equal to 60 m/min, the rolling speed of the rest passes is less than or equal to 100 m/min, and instantaneous jump of acceleration and deceleration is avoided when the rolling speeds are switched.
2. A substantially improved strength and life 301 superhard precision stainless steel as claimed in claim 1, wherein: the total rolling reduction rate of the semi-finished product cogging rolling is 56-60%.
3. A substantially enhanced strength and life 301 superhard precision stainless steel according to claim 1 or 2, characterized in that: the total reduction rate of the finished product is 70-75%, 8-10 passes of rolling are adopted, the first pass reduction rate is less than or equal to 20%, the reduction rates of other passes are sequentially decreased, the final two passes of reduction rates are respectively less than or equal to 8% and less than or equal to 6%, wherein the rolling speed of the first four passes is less than or equal to 60 m/min, and the rolling speed of the rest passes is less than or equal to 90 m/min.
4. A substantially increased strength and life 301 super hard precision stainless steel as claimed in claim 3 wherein: the temperature of the working oil for rolling the finished product is 47-53 ℃.
5. A substantially increased strength and life 301 super hard precision stainless steel as claimed in claim 3 wherein: the temperature of the stress relief process is about 300 ℃, the speed is 1.0TV value, and the TV value is thickness speed; the cooling mode is slow cooling, and the tapping temperature of the strip steel is 50-60 ℃.
6. A substantially improved strength and life 301 super hard precision stainless steel as claimed in claim 5 wherein: the steel strip blank comprises the following chemical components in percentage by weight: c: 0.100-0.110; mn: 0.700-0.800; s: 0.001-0.004; p: 0.02-0.04; si: 0.600-0.800; cr: 16.100-16.400; ni: 6.500-6.800; mo: 0.06-0.09; n: 0.01-0.015; cu: 0.100-0.200; the balance being Fe.
7. A substantially improved strength and life 301 superhard precision stainless steel as claimed in claim 6, wherein: the steel strip blank comprises the following chemical components in percentage by weight: c: 0.103-0.107; mn: 0.750-0.800; s: 0.001-0.004; p: 0.02-0.04; si: 0.650-0.750; cr: 16.200-16.400; ni: 6.700-6.800; mo: 0.070-0.080; n: 0.011-0.013; cu: 0.100-0.150; the balance being Fe.
8. Use of the substantially increased strength and life 301 superhard precision stainless steel of any one of claims 1 to 7 in precision coil springs and precision elastomeric shims and precision elastomeric elements.
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