Highly corrosion resistant, economical stainless steel and method of making same

Abstract

The application provides an economic stainless steel with high corrosion resistance and a manufacturing method thereof, and belongs to the technical field of stainless steel manufacturing.The stainless steel comprises the following chemical components in percentage by mass: C: 0.001-1.20%, Si: 0.01-1.0%, Mn: 0.01-5.0%, N: 0.001-0.50%, Cr: 10.5-20.0%, Ni: 0.05-0.30%, Mo: 0.05-0.30%, Cu: 0.05-0.20%, Sn: 0.10-0.50%, Al: 0.05-0.50%, B: 0.001-0.005%, P: less than or equal to 0.03%, S: less than or equal to 0.01%, and the balance of Fe and inevitable impurities.The application successfully develops the economic stainless steel with high corrosion resistance through component design and heat treatment process innovation, and has certain guiding significance for iteration and upgrading of stainless steel products.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel manufacturing technology, and in particular relates to a high corrosion-resistant and economical stainless steel and its manufacturing method. Background Technology

[0002] Stainless steel is characterized by its rust-proof and corrosion-resistant properties. It typically contains more than 10.5% chromium and no more than 1.2% carbon. Because a continuous, dense, and complete passivation film forms on the surface of stainless steel, isolating the metal from the solution, it is generally difficult for it to corrode through chemical reactions with the medium. However, in actual use, stainless steel materials may corrode due to service conditions, surface quality, and delivery condition. Therefore, improving the corrosion resistance of the material without significantly increasing costs is a pressing technical challenge.

[0003] To improve the corrosion resistance of stainless steel, current technologies, from a material design perspective, increase the proportion of elements such as Ni, Mo, and Cu to make the passivation film of stainless steel denser. However, the current addition of these elements is generally above 0.5 wt.%, which significantly increases production costs. Therefore, it is necessary to invent a new composition system for stainless steel that can reduce the increase in production costs while improving corrosion resistance. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a highly corrosion-resistant and economical stainless steel and its manufacturing method.

[0005] To achieve the above objectives, the present invention provides a highly corrosion-resistant and economical stainless steel comprising the following chemical composition by mass percentage: C: 0.001–1.20%, Si: 0.01–1.0%, Mn: 0.01–5.0%, N: 0.001–0.50%, Cr: 10.5–20.0%, Ni: 0.05–0.30%, Mo: 0.05–0.30%, Cu: 0.05–0.20%, Sn: 0.10–0.50%, Al: 0.05–0.50%, B: 0.001–0.005%, P ≤ 0.03%, S ≤ 0.01%, with the balance being Fe and unavoidable impurities.

[0006] Further, it includes the following chemical composition by mass percentage: C: 0.038%, Si: 0.28%, Mn: 0.32%, N: 0.042%, Cr: 16.21%, Ni: 0.18%, Mo: 0.10%, Cu: 0.08%, Sn: 0.18%, Al: 0.28%, B: 0.002%, P: 0.026%, S: 0.003%, with the balance being Fe and unavoidable impurities.

[0007] This invention achieves excellent corrosion resistance in stainless steel by adding trace amounts of alloying elements such as Ni, Mo, Cu, Sn, Al, and B, while controlling the content of impurity elements such as S and P in the steel. Unlike existing stainless steel composition systems, the threshold for adding elements that improve corrosion resistance is further lowered, and the influence of other elements such as Sn and B on the material's corrosion resistance is also considered. This significantly improves the corrosion resistance of stainless steel materials with a slight increase in production costs, providing guidance for the iterative upgrading of stainless steel products.

[0008] This invention also proposes a method for preparing the above-mentioned high corrosion-resistant and economical stainless steel, comprising the following steps:

[0009] The molten iron prepared according to the stated mass percentage is cast into a billet. The billet is heated, rough rolled, finish rolled, and coiled to obtain a hot-rolled steel coil. The hot-rolled steel coil is subjected to a first annealing, pickling, cold rolling, a second annealing, pickling, and cooling to obtain the high corrosion-resistant and economical stainless steel.

[0010] Furthermore, the raw materials for smelting and preparing molten iron can be ores, or finished steel products, semi-finished products, scrap steel, etc. Smelting equipment includes, but is not limited to, BOF converters, EAF electric arc furnaces, K-OBM-S converters, AOD converters, VOD converters, LF furnaces, etc., and billets can be produced through continuous casting, die casting, etc. Depending on the surface quality, the billets may be ground or left unground.

[0011] Furthermore, the process of hot rolling the cast billet into hot-rolled steel coils can be carried out using a continuous rolling mill or a furnace rolling mill.

[0012] Furthermore, the temperature of the heating homogenization zone is 1150–1250°C, and the total heating time is 200–240 min.

[0013] Furthermore, the exit temperature of the roughing mill is 1000-1100℃, the final rolling temperature of the finishing mill is 800-980℃, and the coiling temperature is 600-700℃.

[0014] Furthermore, the first annealing is performed using either a shroud annealing or continuous annealing.

[0015] Furthermore, the first annealing is performed using a bell-type furnace annealing or a continuous annealing in a raw material annealing and pickling line.

[0016] Furthermore, the annealing temperature of the bell-type annealing is 750–880°C, and the holding time is 15–35 h.

[0017] Furthermore, the annealing temperature for continuous annealing is 800–900°C, and the wire speed is 20–50 m / min.

[0018] Furthermore, the hot-rolled coils after the first annealing and pickling are cold-rolled on a continuous cold rolling mill or a single rolling mill to the target thickness of the finished product.

[0019] Furthermore, the second annealing and pickling are carried out on the finished product annealing and pickling line.

[0020] Furthermore, the annealing temperature for the second annealing is 800–900°C, and the routing speed is 20–50 m / min.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] This invention, through component design and combined with relevant heat treatment processes, successfully developed a highly corrosion-resistant and economical stainless steel. Compared with existing steel grades, the stainless steel prepared by this invention can reduce the uniform corrosion rate by more than 20%, reduce the pitting corrosion rate by more than 20%, and increase the steel production and manufacturing cost by no more than 15%. This invention has certain guiding significance for the iterative upgrading of stainless steel products. Detailed Implementation

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0027] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0028] This invention provides a highly corrosion-resistant and economical stainless steel, comprising the following chemical composition by mass percentage: C: 0.001–1.20%, Si: 0.01–1.0%, Mn: 0.01–5.0%, N: 0.001–0.50%, Cr: 10.5–20.0%, Ni: 0.05–0.30%, Mo: 0.05–0.30%, Cu: 0.05–0.20%, Sn: 0.10–0.50%, Al: 0.05–0.50%, B: 0.001–0.005%, P≤0.03%, S≤0.01%, with the balance being Fe and unavoidable impurities.

[0029] In a preferred embodiment of the invention, the high corrosion-resistant, economical stainless steel comprises the following chemical composition by mass percentage: C: 0.038%, Si: 0.28%, Mn: 0.32%, N: 0.042%, Cr: 16.21%, Ni: 0.18%, Mo: 0.10%, Cu: 0.08%, Sn: 0.18%, Al: 0.28%, B: 0.002%, P: 0.026%, S: 0.003%, with the balance being Fe and unavoidable impurities.

[0030] This invention achieves excellent corrosion resistance in stainless steel by adding trace amounts of alloying elements such as Ni, Mo, Cu, Sn, Al, and B, while controlling the content of impurity elements such as S and P in the steel. Unlike existing stainless steel composition systems, the threshold for the content of these corrosion-enhancing elements is further lowered, and the influence of other elements such as Sn and B on the material's corrosion resistance is also considered. This significantly improves the corrosion resistance of stainless steel with a slight increase in production costs, providing guidance for the iterative upgrading of stainless steel products.

[0031] This invention also proposes a method for preparing the above-mentioned high corrosion resistance and economical stainless steel, comprising the following steps:

[0032] The molten iron prepared according to the stated mass percentage is cast into a billet. The billet is heated, rough rolled, finish rolled, and coiled to obtain a hot-rolled steel coil. The hot-rolled steel coil is subjected to a first annealing, pickling, cold rolling, a second annealing, pickling, and cooling to obtain the high corrosion-resistant and economical stainless steel.

[0033] In this embodiment of the invention, the raw materials for smelting and preparing molten iron can be ores, or finished steel products, semi-finished products, scrap steel, etc. Smelting equipment includes, but is not limited to, BOF converters, EAF electric arc furnaces, K-OBM-S converters, AOD converters, VOD converters, LF furnaces, etc., and billets can be produced through continuous casting, die casting, etc. Depending on the surface quality, the billets may be ground or left unground.

[0034] In this embodiment of the invention, the process of hot rolling a billet into a hot-rolled steel coil can be carried out using a continuous rolling mill or a furnace rolling mill.

[0035] In a preferred embodiment of the present invention, the temperature of the heating homogenization zone is 1150-1250°C, and the total heating time is 200-240 min.

[0036] In a preferred embodiment of the present invention, the exit temperature of the roughing mill is 1000-1100°C, the final rolling temperature of the finishing mill is 800-980°C, and the winding temperature of the coiling is 600-700°C.

[0037] In this embodiment of the invention, the first annealing is either bell-type annealing or continuous annealing, and the first annealing is either bell-type furnace annealing or continuous annealing in a raw material annealing and pickling line.

[0038] In a preferred embodiment of the present invention, the annealing temperature of the bell-type annealing is 750-880°C, and the holding time is 15-35 hours.

[0039] In a preferred embodiment of the present invention, the annealing temperature of the continuous annealing is 800-900°C, and the routing speed is 20-50 m / min.

[0040] In this embodiment of the invention, the hot-rolled coil after the first annealing and pickling is cold-rolled on a cold continuous rolling mill or a single rolling mill to the target thickness of the finished product.

[0041] In this embodiment of the invention, the second annealing and pickling are performed on the finished product annealing and pickling line.

[0042] In a preferred embodiment of the present invention, the annealing temperature of the second annealing is 800-900°C, and the routing speed is 20-50 m / min.

[0043] In this embodiment of the invention, the raw materials for smelting and preparing molten iron are magnetite (Fe3O4), hematite (Fe2O3), siderite (FeCO3), scrap steel, and recycled scrap iron. The source is not limited as long as it can meet the mass percentage of stainless steel prepared in the embodiment.

[0044] The technical solution of the present invention will be further illustrated by the following embodiments.

[0045] The processes not described in detail in the following embodiments, such as "smelting" and "pickling", are conventional methods in the field and are not the focus of this invention, so they will not be described in detail.

[0046] Corrosion rate test method:

[0047] A test solution of 5wt% NaCl + 1mol / L HCl was prepared using ultrapure water, sodium chloride, and concentrated hydrochloric acid, and heated to 35℃ in a water bath. After the system stabilized, a sample with a length of 10mm and a width of 10mm was immersed in the test solution for 0.5h. The sample was then removed, cleaned with alcohol, and the weight of the corroded sample was recorded as m2 (g). The weight of the sample before immersion was recorded as m1 (g). The uniform corrosion rate was calculated as (m1 - m2) ÷ (S × t), where S is the surface area of ​​the sample and t is the immersion time. In this experiment, S = 10 × 10 × 10 -6 m 2 , t=0.5h.

[0048] Pitting corrosion rate test method: Prepare the FeCl3+HCl test solution according to GB / T 17897. Use a glass flask as the container and place the test solution in a constant temperature water bath at 35℃. After the solution temperature stabilizes, place a sample with a length of 30mm and a width of 20mm on a support in the test solution and immerse it continuously for 24 hours. During the immersion process, cover the container with a watch glass to prevent the solution from evaporating. After immersion, remove the sample, remove the corrosion products from the sample, ultrasonically clean and dry it, and weigh it as m2 (in g). Weigh the sample before immersion and record it as m1 (in g). Pitting corrosion rate = (m1-m2)÷(S×t), where S is the surface area of ​​the sample and t is the immersion time. In this test, S = 30×20×10 -6 m 2 , t=24h.

[0049] Example 1

[0050] The stainless steel of this embodiment comprises the following chemical composition by mass percentage: C: 0.038%, Si: 0.28%, Mn: 0.32%, N: 0.042%, Cr: 16.21%, Ni: 0.18%, Mo: 0.10%, Cu: 0.08%, Sn: 0.18%, Al: 0.28%, B: 0.002%, P: 0.026%, S: 0.003%, with the balance being Fe and unavoidable impurities.

[0051] The raw materials of each element are smelted according to the above mass percentages to prepare molten iron. The molten iron is then pretreated → AOD → LF → continuous casting → billet (conventional technical means can be used, which is not the focus of this invention and will not be described in detail) to obtain the billet.

[0052] The obtained billet was heated (heating zone temperature of the heating furnace was 1180℃, total furnace time was 224min) by continuous rolling mill, rough rolling (exit temperature 1055℃), finish rolling (final rolling temperature 845℃) and coiling (coiling temperature 640℃) to obtain a hot-rolled steel coil with a thickness of 4.5mm.

[0053] The obtained hot-rolled steel coils were subjected to bell-type annealing in a bell-type furnace, i.e., the first annealing (the annealing temperature of the bell-type annealing was 870℃, and the holding time was 20h). After the first annealing, the coils were pickled. The pickled hot-rolled coils were then cold-rolled on a single rolling mill to the target thickness of 1.0mm. After that, the coils were subjected to a second annealing (annealing temperature was 875℃, and the line speed was 35m / min) and pickling in the finished product annealing and pickling line to obtain stainless steel.

[0054] Comparison: 17% Cr type ferritic stainless steel 10Cr17 was produced using the same process as in Example 1, the only difference being the chemical composition, specifically including the following chemical components by mass percentage: C: 0.038%, Si: 0.28%, Mn: 0.32%, N: 0.042%, Cr: 16.21%, Ni: 0.18%, P: 0.026%, S: 0.003%, with the balance being Fe and unavoidable impurities.

[0055] Uniform corrosion rate: Test results show that the uniform corrosion rate of the stainless steel prepared in Example 1 of this invention is 82 g / (m²). 2 The uniform corrosion rate of the control sample 10Cr17 was 125 g / (m·h), with a corrosion rate of 125 g / (m·h). 2 (h) The uniform corrosion rate of the stainless steel prepared in Example 1 of this invention decreased by 34.4%.

[0056] Pitting corrosion rate: Test results show that the pitting corrosion rate of the stainless steel prepared in Example 1 of this invention is 24 g / (m²). 2 The pitting corrosion rate of the control sample 10Cr17 was 32 g / (m·h). 2 (h) The pitting corrosion rate of the stainless steel prepared in Example 1 of the present invention decreased by 25%.

[0057] Compared to the 17% Cr type ferritic stainless steel 10Cr17 used as a control, the stainless steel product of Example 1 of the present invention has additional Mo, Cu, Sn, Al and B, which increases the cost by about 832 yuan / ton. Based on the base price of 17% Cr type ferritic stainless steel 10Cr17 of 9,500 yuan / ton, the cost increase is 832 ÷ 9,500 = 8.76%. Therefore, the embodiment of the present invention improves the corrosion resistance of stainless steel with a very small increase in cost.

[0058] Example 2

[0059] The stainless steel of this embodiment comprises the following chemical composition by mass percentage: C: 0.23%, Si: 0.23%, Mn: 0.25%, N: 0.085%, Cr: 13.11%, Ni: 0.12%, Mo: 0.07%, Cu: 0.08%, Sn: 0.21%, Al: 0.23%, B: 0.003%, P: 0.024%, S: 0.001%, with the balance being Fe and unavoidable impurities.

[0060] Raw materials will be prepared according to the above mass percentages, and molten iron will be obtained by smelting the raw materials of each element. The smelting process route is as follows: scrap steel → blast furnace smelting → molten iron pretreatment → AOD → LF → continuous casting → billet casting.

[0061] The obtained billet was heated by a continuous rolling mill (heating furnace soaking section temperature was 1210℃, total furnace time was 235min), rough rolling (exit temperature 1072℃), finish rolling (final rolling temperature 890℃), and coiling (coiling temperature 685℃) to obtain a hot-rolled steel coil with a thickness of 4.0mm.

[0062] The obtained hot-rolled steel coils were subjected to bell-type annealing in a bell-type furnace, i.e., the first annealing (the annealing temperature of the bell-type annealing was 820℃, and the holding time was 28h). After the first annealing, the hot-rolled coils were pickled. The pickled hot-rolled coils were then cold-rolled on a single rolling mill to the target thickness of 0.8mm. After that, the coils were subjected to a second annealing (annealing temperature was 830℃, and the line speed was 30m / min) and pickling in the finished product annealing and pickling line to obtain stainless steel.

[0063] Comparison: 13% Cr type martensitic stainless steel 20Cr13 was produced using the same process as in Example 1, the only difference being the chemical composition, specifically including the following chemical components by mass percentage: C: 0.23%, Si: 0.23%, Mn: 0.25%, N: 0.085%, Cr: 13.11%, Ni: 0.12%, S: 0.001%, with the balance being Fe and unavoidable impurities.

[0064] Uniform corrosion rate: Test results show that the uniform corrosion rate of the stainless steel prepared in Example 2 of this invention is 232 g / (m²). 2 The uniform corrosion rate of the control sample, 13% Cr type martensitic stainless steel 20Cr13, was 367 g / (m³). 2 (h) The uniform corrosion rate of the stainless steel prepared in Example 2 of this invention decreased by 36.8%.

[0065] Pitting corrosion rate: Test results show that the pitting corrosion rate of the stainless steel prepared in Example 2 of this invention is 61 g / (m²). 2 The uniform corrosion rate of the control sample, 13% Cr type martensitic stainless steel 20Cr13, was 79 g / (m³). 2(h) The pitting corrosion rate of the stainless steel prepared in Example 2 of this invention decreased by 22.8%.

[0066] Compared to 13% Cr-type martensitic stainless steel 20Cr13, the stainless steel product of Example 2 of this invention, with the additional addition of Mo: 0.07%, Cu: 0.08%, Sn: 0.21%, Al: 0.23%, and B: 0.003%, increases the cost by approximately 772 yuan / ton. Based on a base price of 9000 yuan / ton for 13% Cr-type martensitic stainless steel 20Cr13, this represents an 8.58% increase in cost. Therefore, this embodiment of the invention improves the corrosion resistance of stainless steel with a very small increase in cost.

[0067] Example 3

[0068] The stainless steel of this embodiment comprises the following chemical composition by weight percentage: C: 1.20%, Si: 0.08%, Mn: 5.0%, N: 0.25%, Cr: 10.5%, Ni: 0.30%, Mo: 0.12%, Cu: 0.15%, Sn: 0.50%, Al: 0.32%, B: 0.001%, P: 0.03%, S: 0.01%, with the balance being Fe and unavoidable impurities.

[0069] Iron ore will be smelted according to the above mass percentages to obtain molten iron. The smelting process route is as follows: iron ore → blast furnace smelting → molten iron pretreatment → AOD → LF → continuous casting → billet casting.

[0070] The obtained billet is heated by a continuous rolling mill (heating furnace soaking section temperature is 1150℃, total furnace time is 200min), rough rolling (exit temperature 1000℃), finish rolling (final rolling temperature 980℃), and coiling (coiling temperature 655℃) to obtain a hot-rolled steel coil with a thickness of 3.5mm.

[0071] The obtained hot-rolled steel coils are continuously annealed using a raw material annealing and pickling line, namely, the first annealing (the annealing temperature of continuous annealing is 825℃, and the line speed is 30m / min), followed by pickling. The pickled hot-rolled coils are then cold-rolled on a single rolling mill to the target thickness of 0.60mm. After that, a second annealing (annealing temperature is 800℃, and the line speed is 50m / min) and pickling are performed on a finished product annealing and pickling line to obtain stainless steel.

[0072] Comparison: Martensitic stainless steel M1 was produced using the same process as in Example 3, except that the chemical composition was different. Specifically, it included the following chemical components by mass percentage: C: 1.20%, Si: 0.08%, Mn: 5.0%, N: 0.25%, Cr: 10.5%, Ni: 0.30%, Sn: 0.50%, P: 0.03%, S: 0.01%, with the balance being Fe and unavoidable impurities.

[0073] Uniform corrosion rate: Test results show that the uniform corrosion rate of the stainless steel prepared in Example 3 of this invention is 375 g / (m²). 2 The uniform corrosion rate of the control sample, martensitic stainless steel M1, was 544 g / (m·h). 2 (h) The uniform corrosion rate of the stainless steel prepared in Example 3 of this invention decreased by 45.1%.

[0074] Pitting corrosion rate: Test results show that the pitting corrosion rate of the stainless steel prepared in Example 3 of this invention is 138 g / (m²). 2 The uniform corrosion rate of the control sample, martensitic stainless steel M1, was 178 g / (m·h). 2 (h) The pitting corrosion rate of the stainless steel prepared in Example 3 of this invention decreased by 29.0%.

[0075] Compared with martensitic stainless steel M1, the stainless steel product of Example 3 of the present invention, with the addition of Mo, Cu, Al and B, increases the cost by about RMB 1,598 per ton. Based on the base price of martensitic stainless steel M1 of RMB 14,500 per ton, the cost increases by 11.02%. Therefore, the embodiment of the present invention improves the corrosion resistance of stainless steel with a very small increase in cost.

[0076] Example 4

[0077] The stainless steel of this embodiment comprises the following chemical composition by mass percentage: C: 0.001%, Si: 1.0%, Mn: 0.01%, N: 0.15%, Cr: 20.0%, Ni: 0.05%, Mo: 0.25%, Cu: 0.05%, Sn: 0.10%, Al: 0.18%, B: 0.005%, P: 0.01%, S: 0.01%, with the balance being Fe and unavoidable impurities.

[0078] Iron ore will be smelted according to the above mass percentages to obtain molten iron. The smelting process route is as follows: iron ore → blast furnace smelting → molten iron pretreatment → AOD → LF → continuous casting → billet casting.

[0079] The obtained billet is heated by a continuous rolling mill (heating furnace soaking section temperature is 1250℃, total furnace time is 240min), rough rolling (exit temperature 1100℃), finish rolling (final rolling temperature 885℃), and coiling (coiling temperature 675℃) to obtain a hot-rolled steel coil with a thickness of 3.0mm.

[0080] The obtained hot-rolled steel coils were subjected to bell-type annealing in a bell-type furnace, i.e., the first annealing (the annealing temperature of the bell-type annealing was 880℃, and the holding time was 15h). After the first annealing, the hot-rolled coils were pickled. The pickled hot-rolled coils were then cold-rolled on a single rolling mill to the target thickness of 0.5mm. After that, the coils were subjected to a second annealing (annealing temperature was 900℃, and the line speed was 20m / min) and pickling in the finished product annealing and pickling line to obtain stainless steel.

[0081] Comparison: Martensitic stainless steel M2 was produced using the same process as in Example 4, except that the chemical composition was different. Specifically, it included the following chemical components by mass percentage: C: 0.001%, Si: 1.0%, Mn: 0.01%, N: 0.15%, Cr: 20.0%, Ni: 0.05%, Sn: 0.10%, P: 0.01%, S: 0.01%, with the balance being Fe and unavoidable impurities.

[0082] Uniform corrosion rate: Test results show that the uniform corrosion rate of the stainless steel prepared in Example 4 of this invention is 64 g / (m²). 2 The uniform corrosion rate of the control sample, martensitic stainless steel M2, was 81 g / (m·h). 2 (h) The uniform corrosion rate of the stainless steel prepared in Example 4 of this invention decreased by 26.6%.

[0083] Pitting corrosion rate: Test results show that the pitting corrosion rate of the stainless steel prepared in Example 4 of this invention is 18 g / (m²). 2 The uniform corrosion rate of the control sample, martensitic stainless steel M2, was 14 g / (m·h). 2 (h) The pitting corrosion rate of the stainless steel prepared in Example 4 of this invention decreased by 22.2%.

[0084] Compared with martensitic stainless steel M2, the stainless steel product of Example 4 of the present invention has the additional addition of Mo, Cu, Al and B, which increases the cost by about RMB 1,183 per ton. Based on the base price of martensitic stainless steel M2 of RMB 13,100 per ton, the cost increases by 9.03%. Therefore, the present invention improves the corrosion resistance of stainless steel with a very small increase in cost.

[0085] Comparative Example 1 (Ni, Mo, Cu, Sn, and B are omitted)

[0086] The stainless steel in this comparative example comprises the following chemical composition by mass percentage: C: 0.038%, Si: 0.28%, Mn: 0.32%, N: 0.042%, Cr: 16.21%, P: 0.026%, S: 0.003%, with the balance being Fe and unavoidable impurities.

[0087] The preparation method is the same as in Example 1.

[0088] Corrosion rate test: The test results show that the uniform corrosion rate of Comparative Example 1 is 132 g / (m²). 2 The pitting corrosion rate is 34 g / (m·h). 2 The results (·h) were all higher than those of Example 1.

[0089] As can be seen from the comparison between Comparative Example 1 and Example 1, the addition of elements Ni, Mo, Cu, Sn, Al and B to the steel promotes a denser and more stable surface passivation film structure, thereby improving the corrosion resistance of the substrate.

[0090] Comparative Example 2 (changing the mass percentage of each chemical component, exceeding the scope of protection of the claims)

[0091] The stainless steel of this embodiment comprises the following chemical composition by weight percentage: C: 0.04%, Si: 0.32%, Mn: 0.35%, N: 0.05%, Cr: 25.0%, Ni: 0.57%, Mo: 0.38%, Cu: 0.45%, Sn: 0.68%, Al: 0.65%, B: 0.006%, P: 0.04%, S: 0.03%, with the balance being Fe and unavoidable impurities.

[0092] The preparation method is the same as in Example 1.

[0093] Corrosion rate test: The test results show that the uniform corrosion rate of Comparative Example 1 is 28 g / (m²). 2 The pitting corrosion rate is 12 g / (m·h). 2 The method is similar to Example 1 of the present invention, but due to the large amount of alloying elements added, although the corrosion resistance is greatly improved, the production cost and manufacturing difficulty are greatly increased. According to calculations, the cost increase of adding C, Ni, Mo, Cu, Sn, Al and B is more than 40%, which is too high and not suitable for large-scale production.

[0094] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A highly corrosion-resistant and economical stainless steel, characterized in that, By mass percentage, it consists of the following chemical components: C: 0.001–1.20%, Si: 0.01–1.0%, Mn: 0.01–5.0%, N: 0.001–0.50%, Cr: 10.5–20.0%, Ni: 0.05–0.30%, Mo: 0.05–0.30%, Cu: 0.05–0.20%, Sn: 0.10–0.50%, Al: 0.05–0.50%, B: 0.001–0.005%, P≤0.03%, S≤0.01%, with the balance being Fe and unavoidable impurities; The preparation method of the aforementioned high corrosion-resistant and economical stainless steel comprises the following steps: The molten iron prepared according to the mass percentage is cast into a billet, and the billet is heated, rough rolled, fine rolled and coiled to obtain a hot rolled steel coil. The hot rolled steel coil is subjected to a first annealing, pickling, cold rolling, a second annealing, pickling and cooling to obtain the high corrosion resistant and economical stainless steel. The temperature of the heating homogenization zone is 1150-1250℃, and the total heating time is 200-240 min; The exit temperature of the roughing mill is 1000-1100℃, the final rolling temperature of the finishing mill is 800-980℃, and the coiling temperature is 600-700℃. The first annealing is performed using either a shroud annealing or continuous annealing.

2. The high corrosion-resistant and economical stainless steel according to claim 1, characterized in that, It is composed of the following chemical components: C: 0.038%, Si: 0.28%, Mn: 0.32%, N: 0.042%, Cr: 16.21%, Ni: 0.18%, Mo: 0.10%, Cu: 0.08%, Sn: 0.18%, Al: 0.28%, B: 0.002%, P: 0.026%, S: 0.003%, with the balance being Fe and unavoidable impurities.

3. The high corrosion-resistant and economical stainless steel according to claim 1, characterized in that, The annealing temperature for the bell-type annealing is 750–880℃, and the holding time is 15–35h.

4. The high corrosion-resistant and economical stainless steel according to claim 1, characterized in that, The continuous annealing process involves an annealing temperature of 800–900°C and a trace speed of 20–50 m / min.

5. The high corrosion-resistant and economical stainless steel according to claim 1, characterized in that, The second annealing temperature is 800-900℃, and the routing speed is 20-50m / min.