Low-contact potential difference high-strength high-corrosion-resistance stainless steel-carbon steel composite reinforcing steel bar and manufacturing method therefor

Abstract

A low-contact potential difference high-strength high-corrosion-resistance stainless steel-carbon steel composite reinforcing steel bar and a manufacturing method therefor. The composite reinforcing steel bar comprises: a carbon steel reinforcing steel bar and a stainless steel layer wrapping the surface of the carbon steel reinforcing steel bar, and the carbon steel reinforcing steel bar comprises the following components in percentage by weight: C: 0.01-0.08%, Si: 0.05-0.4%, Mn: 0.50-1.70%, Al: 0.020-0.040%, Cr: 0.25-0.8%, Cu, 0.18-0.6%, Ni: 0.2-0.8%, Ti: 0.001-0.02%, and the balance being Fe and other inevitable impurities; and the self-corrosion potential difference between the carbon steel reinforcing steel bar and the stainless steel layer is less than 0.25 V. The potential difference (less than 0.25 V) between the carbon steel reinforcing steel bar and the stainless steel layer is reduced, thus the end face galvanic corrosion is greatly reduced, and the galvanic corrosion rate of the carbon steel at the end of the composite reinforcing steel bar is similar to that of a common reinforcing steel bar, so that good corrosion resistance is achieved. Moreover, the stainless steel and the carbon steel are effectively composited in a metallurgical bonding manner, so that the problem of difficulty in connection is solved.

Description

A low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar and its manufacturing method Technical Field

[0001] The present invention relates to the technical field of composite steel bar manufacturing, and in particular to a stainless steel carbon steel composite steel bar with low contact potential difference, high strength and high corrosion resistance, and a manufacturing method thereof. Background Art

[0002] Among the existing steel materials, there are many types of composite materials, most of which are composite plates composed of carbon steel and stainless steel, including explosive composite plates, rolled composite plates, mechanically bonded or brazed composite plates. In recent years, stainless steel carbon steel composite steel bars have a stainless steel outer layer and a carbon steel inner layer. Because they have the corrosion resistance of stainless steel and the strength of carbon steel as well as the cost advantage, they have very broad application prospects in oceans and coastal areas.

[0003] However, contact between carbon steel and stainless steel creates a potential difference, leading to galvanic corrosion. It's well known that a corrosion potential difference indicates the tendency toward galvanic corrosion. The greater the difference in corrosion potential between the two metals in their operating environment, the greater the likelihood that the anode metal will suffer accelerated corrosion damage when forming a galvanic pair. While the difference in self-corrosion potential between carbon steel and stainless steel is not significant, the corrosion current of carbon steel increases exponentially when the service environment is an ion-rich solution.

[0004] CN106964649A discloses a method for preparing highly corrosion-resistant bimetallic composite rebar. This application uses carbon steel round bars as the core, which, after surface treatment, are assembled into corrosion-resistant alloy tubes. The process is then heated and rolled to produce the bimetallic composite rebar. The process disclosed in this application is similar to that disclosed in CN107933013A, though the latter is more specific in its implementation. This improved process alone yields rebar with improved strength and corrosion resistance, but does not address the difference in self-corrosion potential between carbon steel and stainless steel.

[0005] CN104910509B discloses a method for continuously producing composite steel bars formed by wrapping polypropylene tape around steel bars, producing a polypropylene-steel composite, wherein the polypropylene tape is wound circumferentially to completely wrap the steel bars in an inner layer, the polypropylene is heated to melt, and after cooling, the polypropylene completely wraps the steel bars. The composite steel bars are wrapped with organic materials, which are significantly different from composite steel bars metallurgically bonded with stainless steel and carbon steel.

[0006] CN104357745A discloses a composite steel bar with a yield strength of 600 MPa or greater and a production method. While the name "composite steel bar" suggests it's a standard steel bar, it's not a composite of stainless steel and carbon steel and therefore doesn't involve corrosion potential differences. Furthermore, the carbon content in the steel bar exceeds national standards.

[0007] CN107933013A discloses a stainless steel / carbon steel vacuum composite steel bar and its manufacturing process, which mainly uses a vacuum electron beam to achieve welding of stainless steel and carbon steel and vacuum in the pores between the stainless steel and carbon steel, and then heats and rolls to obtain the stainless steel / carbon steel rolled composite steel bar; this is a general basic rolling composite method and does not involve composition design and material strength design, etc.

[0008] CN112598723B discloses a method, device and storage medium for identifying the thickness of stainless steel coated steel bars; CN111141671A discloses a device and method for simulating galvanic corrosion of composite steel bar coating and core material; the above applications are all patent applications for methods of application or detection of stainless steel and carbon steel composite steel bars.

[0009] Based on the above patent applications, there are few studies on stainless steel / carbon steel in existing composite steel bars, and no one has conducted relevant research on how to reduce the potential difference between stainless steel and carbon steel through composition and process control.

[0010] Summary of the Invention

[0011] The purpose of the present invention is to provide a stainless steel-carbon steel composite steel bar with low contact potential difference and high corrosion resistance and a manufacturing method thereof, which reduces the potential difference between the carbon steel bar and the stainless steel layer (less than 0.25V), greatly reduces the end face galvanic corrosion, and the galvanic corrosion rate of the carbon steel at the end of the composite steel bar is similar to that of ordinary steel bars, and has good corrosion resistance; and through metallurgical bonding, the stainless steel and carbon steel bars are effectively composited, thereby solving the problem of connection difficulties.

[0012] To achieve the above object, the technical solution of the present invention is:

[0013] A low contact potential difference, high strength, and high corrosion resistance stainless steel carbon steel composite steel bar comprises a carbon steel bar and a stainless steel layer wrapped around the surface of the carbon steel bar, wherein the carbon steel bar comprises the following components by weight: C: 0.010-0.080%, Si: 0.05-0.4%, Mn: 0.50-1.70%, Al: 0.020-0.040%, Cr: 0.25-0.80%, Cu: 0.18-0.60%, Ni: 0.20-0.80%, Ti: 0.001-0.020%, and the balance comprises Fe and other unavoidable impurities;

[0014] The self-corrosion potential difference between the carbon steel reinforcement and the stainless steel layer is less than 0.25V.

[0015] Furthermore, the balance of the carbon steel bar is Fe and other inevitable impurities.

[0016] Furthermore, other inevitable impurities in the carbon steel bar include P≤0.015%, S≤0.008%, and N≤0.008%.

[0017] Furthermore, the stainless steel is 316L stainless steel, and its composition by weight is as follows: C ≤ 0.030%, Si ≤ 0.75%, Mn ≤ 2.00%, P ≤ 0.045%, S ≤ 0.030%, Ni: 10.00-14.00%, Cr: 16.00-18.00%, Mo: 2.00-3.00%, N: 0.02-0.20%, with the remainder comprising Al and other unavoidable impurities. In some embodiments, the stainless steel has a C content of 0.010-0.030%, a Si content of 0.50-0.75%, and a Mn content of 1.00-1.50%. In some embodiments, the stainless steel contains ≤ 0.002% Ti.

[0018] In the chemical composition design of the carbon steel described in the present invention:

[0019] Carbon contributes to strength and acts as a solid solution strengthener in steel, significantly improving its strength. However, too high a carbon content can negatively impact the corrosion resistance of the steel. Therefore, the present invention employs a low-carbon design to control the carbon content to between 0.010% and 0.080%. In some embodiments, the carbon content is between 0.020% and 0.075%.

[0020] Si: Adding silicon to steel improves steel purity and deoxidizes it, while also contributing to its strength. Silicon acts as a solid solution strengthener in steel, but excessive silicon levels can negatively impact weldability. Therefore, the present invention limits the Si content to 0.05-0.40%.

[0021] Mn: It improves the strength of steel through solid solution strengthening and is the most important and economical strengthening element in steel to compensate for the strength loss caused by the reduction of C content. Therefore, the Mn content in the present invention is controlled to be 0.50-1.70%.

[0022] S and P: Sulfur and phosphorus are harmful elements in steel, seriously damaging the plasticity and toughness of steel plates. They are both unavoidable impurity elements. The present invention requires P ≤ 0.015% and S ≤ 0.008%.

[0023] Al: A strong deoxidizing element. In order to ensure that the oxygen content in the steel is as low as possible, the aluminum content in the present invention is controlled at 0.02-0.04%.

[0024] Ti: Ti is a strong carbide-forming element. Adding a small amount of Ti to steel helps fix the N in the steel. The formed TiN can refine the original austenite grain size. The titanium content of the present invention is controlled at 0.001-0.020%.

[0025] Ni: It effectively reduces electrical potential and improves steel corrosion resistance. Adding nickel to quenched and tempered steel significantly improves the steel's low-temperature impact toughness. For economic reasons, the nickel content in this invention is controlled between 0.20% and 0.80%.

[0026] Cr: It can effectively reduce the potential and improve the corrosion resistance of steel; it can form a dense oxide layer and reduce the corrosion rate. The chromium content of the present invention is controlled at 0.25-0.80%.

[0027] Cu: It can effectively reduce the potential and form a dense oxide layer. It is a common additive element for corrosion-resistant steel. The copper content of the present invention is controlled at 0.18-0.80%.

[0028] To ensure the corrosion resistance of the outer layer, 316L stainless steel is used. Its composition range is in accordance with the requirements of the industry standard GB / T4237-2009, and its weight percentages are: C ≤ 0.03%, Si ≤ 0.75%, Mn ≤ 2.0%, P ≤ 0.045%, S ≤ 0.030%, Ni: 10.00-14.00%, Cr: 16.00-18.00%, Mo: 2.00-3.00%, N: 0.02-0.20%, and the remainder includes Al and other unavoidable impurities. To ensure that the composite steel bar has high corrosion resistance, the thickness of the stainless steel layer of the composite steel bar is required to be greater than 0.2mm (the thickness of the stainless steel layer at the longitudinal interface and cross-section must both be greater than 0.2mm). In some embodiments, the thickness of the stainless steel layer is 0.25-1mm.

[0029] Stainless steel carbon steel composite steel bar has an outer layer of stainless steel and an inner layer of carbon steel. In addition, the carbon steel on its end face has no isolation protection. When connected to stainless steel, it will be very difficult to protect it due to electrochemical corrosion. When designing the carbon steel composition, it is necessary to consider adding corrosion-resistant elements and reducing the self-corrosion potential. Since the C element combines with Cr to form CrC, which affects the corrosion resistance, the present invention adopts a low-carbon design with a carbon content similar to that of austenitic stainless steel. In addition, reducing the C content can reduce the carbon gradient between carbon steel and stainless steel, and prevent the accelerated corrosion of carbon steel caused by the large C gradient. In addition, Cr, Cu, and Ni elements are added in a coordinated manner. Cr forms CrO in the early stage of oxidation, which promotes the density of the rust layer and can play an effective anti-corrosion inhibitory role; Cu and Ni are elements that improve the stability of the carbon steel matrix. Ni can effectively reduce the potential and reduce the self-corrosion rate; Cu can promote the density of the rust layer and has a complementary effect on Cr. Its potential reduction effect is worse than that of Ni. The effects of Cr, Cu, and Ni are mainly due to the addition of Cr and Ni. When the amount of Cr and Ni is slightly small, the amount of Cu can be increased to supplement them. The obtained carbon steel has a self-corrosion potential of -0.55V to -0.45V, and the self-corrosion potential difference between carbon steel and stainless steel is less than 0.25V, which reduces the corrosion rate of carbon steel at the end of the composite steel bar, and the galvanic corrosion rate of carbon steel at the end of the composite steel bar is close to that of ordinary steel bars.

[0030] The carbon steel billet raw material for the composite steel bars of the present invention is prepared using conventional methods for producing similar carbon steels, including smelting, continuous casting, forging, hot rolling, and blooming. The production process can be described in accordance with standard YB / T 2011-2014, "Continuously Cast Steel Billets and Rectangular Blooms."

[0031] In some embodiments, during the smelting step, the molten steel can be smelted in a converter or an electric furnace and then refined in an IF furnace. If there are special requirements for the steel quality, the molten steel can be injected into a VD or VOD refining furnace for refining, and a crude steel billet can be formed by continuous casting or die casting.

[0032] In some embodiments, the carbon steel billet is formed by heating a bloom or an ingot at a temperature of 1000-1250° C. The groove rolling mill can change the size of the original carbon steel billet and finally produce a billet.

[0033] In some embodiments, during the forging step, the steel billet may be heated to 1000-1250° C., kept at this temperature for more than 40 minutes, and forged into a square billet.

[0034] In some embodiments, during the hot rolling step, the billet may be placed in a heating furnace to be heated and kept warm, and then rolled into a bar billet on a hot rolling mill and air-cooled to room temperature.

[0035] The method for preparing the stainless steel layer raw material plate of the composite steel bar of the present invention may include smelting, continuous casting, hot rolling, solution heat treatment, and other steps. The method is similar to the production method of stainless steel products of the same grade, and reference may be made to the national standard GB / T 20878-2007 Stainless Steel and Heat-Resistant Steel Grades and Chemical Compositions.

[0036] In some embodiments, during the smelting step, an electric furnace can be used to treat the molten steel, and an AOD (argon oxygen refining furnace) and a VOD refining furnace can be used for refining. A crude steel billet can be formed by continuous casting or die casting. The crude steel billet can be electroslag remelted under an argon protective atmosphere to form a steel billet, and finally the steel billet is subjected to homogenization annealing.

[0037] In some embodiments, during the hot rolling step, the stainless steel billet may be fed into a heating furnace for heating and heat preservation, and a stainless steel plate of a certain thickness may be produced by a hot rolling mill or a medium and heavy plate rolling mill;

[0038] In some embodiments, the solution heat treatment step is to perform surface treatment (including sandblasting and grinding) on ​​the stainless steel plate, heat it to 1000-1100° C., quench it in water immediately after it is taken out of the furnace, and then perform pickling and passivation.

[0039] The present invention also provides a method for manufacturing the low contact potential difference, high strength, and high corrosion resistance stainless steel carbon steel composite steel bar, comprising the following steps:

[0040] 1) Assembly

[0041] The surfaces of stainless steel and carbon steel bars are cleaned, and then fixed and assembled, welded to obtain composite billets, and vacuumed to ensure that the vacuum degree of the stainless steel and carbon steel bar bonding surface is ≤0.1Pa;

[0042] 2) Heating

[0043] The composite blank is heated at a temperature of 1080-1250°C and a heating time of 50-120 minutes;

[0044] 3) Rolling

[0045] Rough rolling and finishing rolling are carried out in sequence, with the finishing rolling inlet temperature being 800-1000°C;

[0046] 4) Cooling

[0047] After rolling, water cooling is carried out, and the upper cooling bed temperature is 800-1000℃.

[0048] In the manufacturing method of the present invention:

[0049] Stainless steel and carbon steel composite rebar, with a stainless steel outer layer and a carbon steel inner layer, is a very complex manufacturing process that requires many key technologies, such as outer stainless steel cladding technology, surface cleaning technology, and composite layer homogenization technology. The surfaces of the stainless steel plate and carbon steel billet are cleaned, and at this time, the surfaces of the stainless steel plate and carbon steel are free of non-matrix components such as oxides, water, and grease. Treatment methods include but are not limited to machining, polishing, sandblasting, and laser treatment. After treatment, the billets are fixed and assembled, and then welded into billets that can be rolled into steel bars. The welding methods here include conventional welding methods such as arc welding and laser welding. After welding is completed, vacuum treatment is performed to ensure that the surface of the stainless steel and carbon steel bars is close to a vacuum state, with a vacuum degree of less than or equal to 0.1Pa.

[0050] The composite billet is heated to a temperature of 1080-1250°C for 50-120 minutes. This temperature regime is designed based on two key considerations: the performance of the stainless steel and the mechanical properties associated with the specifications. The heating time is correlated with the heating temperature. Due to the low thermal conductivity of stainless steel, a longer heating time is required. High heating temperatures can reduce the time in the furnace.

[0051] During the rolling process, in order to combine the performance of stainless steel and carbon steel rebars, the finishing rolling entrance temperature and the upper cooling bed temperature need to be strictly controlled. The rolling temperature and the upper cooling bed temperature should not be lower than 800°C to ensure that the stainless steel layer is not in the temperature range that easily produces σ ferrite during rolling. In the temperature range of 800-1000°C, for the same specifications, the lower the temperature control, the higher the strength, but the elongation performance will decrease if the temperature is too low; the rolling temperature of the specifications with small diameters is selected to be higher, and the rolling temperature of the specifications with large diameters requires a slightly lower temperature to ensure that the grains of the carbon steel substrate are not too large and to ensure good mechanical properties. The microstructure of the obtained carbon steel rebar is uniform ferrite + pearlite, and the grain rating is 8-12.

[0052] The composite steel bar has a yield strength of 450-650 MPa, a tensile strength of 560-700 MPa, a total elongation At≥19%, and a maximum elongation≥11%.

[0053] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0054] The present invention is a composite steel bar with a surface layer of stainless steel, which has good corrosion resistance and can withstand chloride ion environments, greatly improving the service life of reinforced concrete. The core structure carbon steel bar adopts a low-carbon component design. On the one hand, it reduces the carbon gradient between carbon steel and stainless steel and prevents the accelerated corrosion of carbon steel caused by the large C gradient. On the other hand, the synergistic addition of micro-alloy corrosion-resistant elements such as Ni, Cr, and Cu effectively reduces the self-corrosion potential and increases the density of the rust layer, thereby solving the problem of severe galvanic corrosion at the ends of the composite steel bar prepared from carbon steel and stainless steel. The galvanic corrosion rate of the carbon steel at its end is similar to that of ordinary steel bars.

[0055] Based on the composition design, the present invention realizes the complete metallurgical bonding of carbon steel and stainless steel through metallurgical technologies such as heating and controlled rolling, and has both the corrosion resistance of stainless steel and the strength of carbon steel. It can solve the essential pain point of easy corrosion of carbon steel, meet the corrosion resistance requirements of reinforced concrete structures in harsh environments, and has the advantages of high corrosion resistance, good mechanical properties, and simple construction, with great economic and social benefits. It can also solve the pain point of severe galvanic corrosion at the ends of composite steel bars during construction. The composite steel bars obtained by the present invention have a yield strength of 450-650MPa, a tensile strength of 560-700MPa, a total elongation At ≥19%, and a maximum force elongation ≥11%. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] FIG1 is a process flow chart of an embodiment of the present invention.

[0057] FIG2 is a cross-sectional view of the composite steel bar according to the present invention.

[0058] FIG3 is a cross-sectional photograph of the composite steel bar according to Example 1 of the present invention.

[0059] FIG4 is a metallographic photograph of the cross-section of carbon steel of the composite steel bar according to Example 1 of the present invention.

[0060] FIG5 is an enlarged cross-sectional view of the composite steel bar according to Example 1 of the present invention. DETAILED DESCRIPTION

[0061] The present invention will be further described below with reference to specific embodiments and drawings. However, this description does not constitute an undue limitation to the technical solution of the present invention.

[0062] The composition of the 316L stainless steel used in the examples of the present invention is shown in Table 1, with the remainder consisting of Fe and other unavoidable impurities. The composition of the carbon steel rebar used in the examples of the present invention and the ordinary threaded steel bar used in the comparative examples is shown in Table 2, with the remainder consisting of Fe and other unavoidable impurities. The production of the carbon steel rebar follows the standard YB / T 2011-2014, "Continuously Cast Steel Billets and Rectangular Blooms." The production method of the stainless steel layer follows the national standard "GB / T 20878-2007, Stainless Steel and Heat-Resistant Steel Grades and Chemical Compositions."

[0063] Table 1 (Unit: weight percentage)

[0064] Table 2 (Unit: weight percentage)

[0065] The manufacturing process flow of the embodiment of the present invention is shown in FIG1 , and the process parameters are shown in Table 3.

[0066] Table 3

[0067] Comparative Example 1 is an ordinary threaded steel bar, and its typical chemical composition weight percentage is: C: 0.22-0.25%, Si: 0.45-0.55%, Mn: 1.35-1.45%, P≤0.035%, S≤0.035%, V: 0.030-0.045%, Ceq<0.55, and the remainder includes Fe and other unavoidable impurities.

[0068] Comparative Example 2 uses ordinary threaded steel bars as the core and is covered with 316L stainless steel on the outside.

[0069] Figure 2 is a cross-sectional view of the composite rebar of the present invention. Figure 3 is a cross-sectional view of the composite rebar of Example 1 of the present invention. As can be seen from the figure, the carbon steel rebar and stainless steel are well bonded, with no cracks or separation areas. Figure 4 is a photograph of the metallographic structure of the carbon steel rebar in Example 1 of the present invention. The metallographic structure of the carbon steel rebar is ferrite + pearlite, with a grain size of 8 to 12.

[0070] As can be seen from FIG5 , the thickness of the stainless steel layer of the composite steel bar obtained in the present invention is greater than 0.2 mm.

[0071] Corrosion rate measurement experiment: referring to the standard “JB / T7901-1999 Metal Materials Laboratory Uniform Corrosion Full Immersion Test Method”, the simulated solutions used include: NaCl 13000mg / L, KCl 50mg / L, CaCl2 400mg / L, MgCl2 460mg / L, Na2SO4 1000mg / L, NaHCO3 1000mg / L, the pH value of the solution is 6.5±0.3, the solution is static and there is no flow rate.

[0072] Mechanical properties test: Refer to the standards "GB / T228.1-2010 Tensile tests on metallic materials Part 1: Test methods at room temperature" and "GB / T28900-2022 Test methods for steel for reinforced concrete". Turning is not allowed for tensile, bending, and reverse bending test specimens. The testing machine accuracy must reach level 1, and the extensometer accuracy must reach level 1. The gauge length must be greater than 100mm to meet the requirements for calculating Rel and R. p0.2 and maximum force elongation.

[0073] Comparative Example 1 is an ordinary steel bar, whose strength is similar to that of the composite steel bar described in the present invention, but its toughness is worse than that of the present invention. Moreover, the outer layer of the composite steel bar of the present invention has a layer of stainless steel, and its circumferential corrosion resistance is much better than that of Comparative Example 1. Moreover, the corrosion rate of the carbon steel at the end of the composite steel bar of the present invention is even lower than that of the ordinary carbon steel bar, that is, the cross-section corrosion problem can be ignored when using the composite steel bar of the present invention.

[0074] Comparative Example 2 uses ordinary steel bars as the core and is covered with stainless steel as the outer layer. The obtained composite steel bar has mechanical properties close to those of the composite steel bar described in the present invention, but its cross-section corrosion rate is high and the cross-section corrosion is serious.

[0075] As shown in Table 4, the low potential difference design of the carbon steel component resulted in a composite rebar end corrosion rate measurement in which the carbon steel corrosion rate of the composite rebar obtained in the embodiment of the present invention was even lower than that of ordinary carbon steel rebar. In contrast, the carbon steel corrosion rate of the composite rebar end using ordinary carbon steel as the inner core was significantly higher than that of ordinary rebar. This indicates that the low potential difference design of the present invention can effectively reduce the accelerated corrosion of carbon steel due to galvanic corrosion.

[0076] Measurement method: Refer to GB / T 40299-2021 Corrosion of metals and alloys - Corrosion tests - Applicable practice for electrochemical measurement methods. In aqueous solution, a steel sample is clamped with a power supply to form a corrosion potential cell with isolated anode and cathode regions on its surface. The steel sample loses electrons in the solution and becomes positively charged ions, causing current and voltage fluctuations. The electrochemical curve is drawn by detecting the current and voltage fluctuations.

[0077] Table 4

[0078] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therefrom that can be directly derived from or easily conceived by those skilled in the art based on the disclosure of the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. A low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar, comprising a carbon steel bar and a stainless steel layer wrapped on the surface of the carbon steel bar; the weight percentage of the components of the carbon steel bar is: C: 0.010-0.080%, Si: 0.05-0.40%, Mn: 0.50-1.70%, Al: 0.020-0.040%, Cr: 0.25-0.80%, Cu: 0.18-0.60%, Ni: 0.20-0.80%, Ti: 0.001-0.020%, and the balance includes Fe and other inevitable impurities; The self-corrosion potential difference between the carbon steel reinforcement and the stainless steel layer is less than 0.25V.

2. The low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to claim 1, characterized in that: The balance of the carbon steel bar composition is Fe and other inevitable impurities.

3. The low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to claim 1 or 2, characterized in that: Other inevitable impurities in the carbon steel bar include P≤0.015%, S≤0.008%, and N≤0.008%.

4. The low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to claim 1, 2 or 3, characterized in that: The carbon steel bar has a microstructure of uniform ferrite+pearlite, and a grain rating of 8 to 12.

5. The low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to claim 1, 2, 3 or 4, characterized in that: The self-corrosion potential of the carbon steel reinforcement is -0.55V to -0.45V.

6. The low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to any one of claims 1 to 5, characterized in that: The thickness of the stainless steel layer on the surface of the carbon steel bar is greater than 0.2 mm.

7. The low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to claim 1 or 6, characterized in that: The stainless steel layer is 316L stainless steel, and its components by weight percentage are: C≤0.03%, Si≤0.75%, Mn≤2.0%, P≤0.045%, S≤0.030%, Ni: 10.00-14.00%, Cr: 16.00-18.00%, Mo: 2.00-3.00%, N: 0.02-0.20%, and the remainder includes Al and other inevitable impurities.

8. The low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to claim 7, characterized in that: The C content is 0.010-0.030%, the Si content is 0.50-0.75%, and the Mn content is 1.00-1.50%; optionally, the stainless steel contains ≤0.002% Ti.

9. The low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to claim 1, 6, 7 or 8, characterized in that: The self-corrosion potential of the stainless steel layer is -0.4V to -0.3V.

10. The low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to claim 1, characterized in that: The composite steel bar has a yield strength of 450-650 MPa, a tensile strength of 560-700 MPa, a total elongation At≥19%, and a maximum force elongation≥11%.

11. The method for manufacturing a low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to any one of claims 1 to 10, characterized in that: The steps include: 1) Assembly The surfaces of stainless steel and carbon steel bars are cleaned, and then fixed and assembled, welded to obtain composite billets, and vacuumed to ensure that the vacuum degree of the stainless steel and carbon steel bar bonding surface is ≤0.1Pa; 2) Heating The composite blank is heated at a temperature of 1080 to 1250°C and a heating time of 50 to 120 minutes; 3) Rolling Rough rolling and finishing rolling are carried out in sequence, and the finishing rolling inlet temperature is 800-1000°C; 4) Cooling After rolling, water cooling is carried out, and the temperature of the upper cooling bed is 800-1000℃.

12. The method for manufacturing a low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to claim 11, characterized in that: The preparation method of the carbon steel comprises the steps of smelting, continuous casting, forging, hot rolling and blanking.

13. The method for manufacturing a low contact potential difference, high strength and high corrosion resistance stainless steel carbon steel composite steel bar according to claim 12, characterized in that: In the smelting step, the molten steel is smelted in a converter or an electric furnace, then enters an IF furnace for refining, and is formed into a crude steel billet by continuous casting or die casting; In the forging step, the rough steel billet is heated and then cut into billets at a heating temperature of 1000-1250°C, kept at this temperature for more than 40 minutes, and forged into square billets; In the hot rolling step, the square billet is sent to a heating furnace for heating and heat preservation, and then rolled into a rod billet on a hot rolling mill and air-cooled to room temperature.

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