Marine atmospheric corrosion resistant steel and preparation method and application thereof

Abstract

The invention provides marine atmosphere corrosion resistant steel and a preparation method and application thereof, and belongs to the technical field of corrosion resistant steel. The invention provides steel resistant to marine atmosphere corrosion. The steel resistant to marine atmosphere corrosion comprises C, Si, Mn, Ni, Cu, Mo, Nb, V, Ti, Als, N, P, O, S and Fe according to a certain mass content. The contents of all the elements in the weathering resistant steel meet the following conditions that the carbon equivalent Ceq is smaller than or equal to 0.17, the eta is 1.3-1.6, the alpha is 0.2-0.4, and the coast atmospheric environment corrosion resisting index I is larger than or equal to 1.2. By adopting specific components and component proportions, the low-temperature toughness of a welding heat affected zone of a steel material is effectively improved. The result of the embodiment shows that the weather-resistant steel provided by the invention has the advantages that under the welding condition that the heat input quantity is 15-35kJ / cm, the Charpy impact of a welding heat affected zone at-40 DEG C under typical welding heat input is greater than or equal to 150J, and the weather-resistant steel has good low-temperature toughness.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion-resistant steel, and in particular to marine atmosphere corrosion-resistant steel and a preparation method and application thereof. Background Art

[0002] In order to promote the comprehensive and coordinated development of the Bohai Rim regional economy, it is necessary to build cross-sea bridges to alleviate the transportation pressure of railway trunk lines. The marine atmospheric environment is characterized by high humidity, high chloride ions and high radiation intensity, which seriously threatens the construction, operation and maintenance of infrastructure such as bridges in this environment. Therefore, a weathering steel with excellent corrosion resistance is needed to resist the threat of the marine atmospheric environment.

[0003] At present, more and more scholars are focusing on the research and development of steel resistant to marine atmospheric corrosion. For example, Japan has developed a high-Ni system weathering steel for coastal atmospheric environment, but in order to improve the corrosion resistance of the steel, a large amount of Cu, Si, Mo and other elements are added to the formula of the weathering steel. The excessive addition of these elements deteriorates the performance of the welding area of ​​the weathering steel, reduces the low-temperature toughness of the welding heat-affected zone, is not conducive to the application of welding technology in steel manufacturing, and creates safety hazards for construction facilities such as cross-sea bridges.

[0004] In order to simultaneously improve the corrosion resistance of weathering steel and the low-temperature toughness of the welding heat affected zone, people have done a lot of research. For example, CN104046898A discloses a high-performance marine climate-resistant steel plate and a manufacturing method thereof. The steel plate has excellent corrosion resistance, and the Charpy impact energy of the welding heat affected zone at -40°C is ≥100J. The yield strength of the weathering steel is 386~423MPa, and the tensile strength is 511~556MPa. The strength of the weathering steel is Q355 level, which cannot meet the high-load use environment, and the low-temperature toughness of the welding heat affected zone of the weathering steel is low, which cannot meet the needs of practical applications. Summary of the invention

[0005] The object of the present invention is to provide a marine atmosphere corrosion resistant steel and a preparation method and application thereof. The marine atmosphere corrosion resistant steel provided by the present invention has high strength and good low-temperature toughness of the welding heat affected zone obtained when used for welding.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The invention provides a marine atmosphere corrosion resistant steel, which comprises, by weight percentage, 0.03-0.08% C, 0.05-0.19% Si, 0.91-1.25% Mn, 1.2-1.5% Ni, 0.15-0.55% Cu, 0.21-0.40% Mo, 0.010-0.019% Nb, 0.02-0.04% V, 0.01-0.03% Ti, 0.02-0.05% Als, 0.003-0.006% N, 0.001-0.015% P, ≤0.004% O, ≤0.005% S, and the balance Fe;

[0008] The contents of the elements in the marine atmosphere corrosion resistant steel meet the following conditions:

[0009] Carbon equivalent C eq ≤0.17, weather resistance η1.3~1.6, the number and size of precipitated phase α0.2~0.4, coastal atmospheric environment corrosion resistance index I≥1.2;

[0010] The C eq ={25[C]+0.56*(1.5[Mn]+[Si]+1.25[Ni]+1.7[Cu]+5[Mo]+5[Nb]+5[V])} / 25;

[0011] The η=3([Ni]*[Mo])+[Ni]*[Cu];

[0012] The α=([V] / 51+[Ti] / 48+[Nb] / 93) / ([C] / 12+[N] / 14);

[0013] The I=1 / {(1.0-0.16[C])*(1.05-0.05[Si])*(1.04-0.016[Mn])*(1.0-0.5[P])*(1 .0+1.9[S])*(1.0-0.1[Cu])*(1.0-0.12[Ni])*(1.0-0.3[Mo])*(1.0-1.7[Ti])}.

[0014] Preferably, the marine atmosphere corrosion resistant steel comprises, by weight percentage, C 0.03-0.05%, Si 0.10-0.19%, Mn 0.91-1.20%, Ni 1.20-1.35%, Cu 0.15-0.40%, Mo 0.21-0.30%, Nb 0.010-0.016%, V 0.020-0.035%, Ti 0.01-0.02%, Als 0.020-0.040%, N 0.003-0.005%, P 0.001-0.010%, O≤0.003%, S≤0.003%, and the balance Fe.

[0015] Preferably, the marine atmosphere corrosion resistant steel comprises, by weight percentage, C 0.035-0.045%, Si 0.15-0.18%, Mn 0.98-1.10%, Ni 1.22-1.30%, Cu 0.20-0.35%, Mo 0.25-0.28%, Nb 0.013-0.015%, V 0.025-0.03%, Ti 0.014-0.017%, Als 0.025-0.030%, N 0.0034-0.0040%, P 0.002-0.003%, O≤0.002%, S≤0.002%, and the balance Fe.

[0016] The present invention also provides a method for preparing the marine atmosphere corrosion resistant steel described in the above technical solution, comprising the following steps:

[0017] (1) melting the raw materials and then casting to obtain a steel ingot;

[0018] (2) hot rolling the steel ingot obtained in step (1) to obtain a steel plate;

[0019] (3) The steel plate obtained in step (2) is subjected to tempering treatment to obtain marine atmosphere corrosion resistant steel.

[0020] Preferably, the steel billet is heated and kept warm in sequence before the hot rolling in step (2), the keeping temperature is 1150-1200° C., and the keeping time is 2-3 hours.

[0021] Preferably, the hot rolling in step (2) includes rough rolling and finish rolling performed sequentially.

[0022] Preferably, the starting rolling temperature of the rough rolling is 1100-1120° C., and the finishing rolling temperature is 1000-1080° C.; and the cumulative reduction ratio of the rough rolling is above 35%.

[0023] Preferably, the start rolling temperature of the finish rolling is 870-930° C., and the final rolling temperature is 830-850° C.; and the cumulative reduction ratio of the finish rolling is above 30%.

[0024] Preferably, the tempering temperature in step (3) is 400-550° C., and the tempering time is (h+40) min; h is the thickness of the steel plate obtained in step (2), and the unit of h is mm.

[0025] The present invention also provides the use of the marine atmosphere corrosion resistant steel described in the above technical solution or the marine atmosphere corrosion resistant steel prepared according to the preparation method described in the above technical solution in a marine atmosphere environment.

[0026] The invention provides a marine atmosphere corrosion resistant steel, which comprises, by weight percentage, 0.03-0.08% C, 0.05-0.19% Si, 0.91-1.25% Mn, 1.2-1.5% Ni, 0.15-0.55% Cu, 0.21-0.40% Mo, 0.010-0.019% Nb, 0.020-0.040% V, 0.010-0.030% Ti, 0.020-0.050% Als, 0.0030-0.0060% N, 0.001-0.015% P, O≤0.0040%, S≤0.005%, and the balance Fe; the contents of the elements in the marine atmosphere corrosion resistant steel meet the following conditions: the carbon equivalent C eq≤0.17, weather resistance η1.3~1.6, the number and size of precipitated phases α0.2~0.4, and the coastal atmospheric environment corrosion resistance index I≥1.2. The marine atmospheric corrosion resistant steel provided by the present invention reduces the welding crack sensitivity, reduces the MA component brittle phase of the welding heat affected zone, and improves the low-temperature toughness of the welding heat affected zone by controlling the contents of C and Si; improves the welding hot crack tendency caused by the Cu element and the poor low-temperature toughness of the welding heat affected zone caused by excessive Mo element through the composite action between Ni, Cu and Mo; an appropriate amount of Ti element can form TiN particles with high-temperature stability with N, pin the original austenite grain boundary of the welding heat affected zone, control the growth of the original austenite grain, refine the grain, and improve the low-temperature toughness of the welding heat affected zone; an appropriate amount of V element can combine with C and N to fix free [N] to form dispersed V (C, N) particles, which can be used as heterogeneous nucleation particles to promote the nucleation of block / acicular ferrite in the grain and grain boundary in the welding heat affected zone, refine the structure and inhibit coarse granular bainite, and improve the low-temperature toughness of the welding heat affected zone of the steel material. The results of the examples show that the marine atmospheric corrosion resistant steel provided by the present invention has good low temperature toughness under the welding conditions of heat input of 15-35 kJ / cm, and the Charpy impact of the welding heat affected zone at -40°C under typical welding heat input is ≥150J. In addition, the marine atmospheric corrosion resistant steel provided by the present invention has excellent corrosion resistance, and the weight loss of the steel material after corrosion at 360h is 118 mg / cm 2 The corrosion weight loss rate is 0.33 mg / cm 2 *h, the corrosion resistance is 3 to 4 times higher than that of ordinary C-Mn steel materials, the yield strength is 486 to 515MPa, the tensile strength is 590 to 624MPa, the elongation is 23 to 25%, the yield strength ratio is 0.81 to 0.83, the -40℃ Charpy V-notch impact energy is ≥280J, and the fiber section rate of the impact fracture is ≥85%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a microstructure diagram of the marine atmosphere corrosion resistant steel of Example 1 of the present invention;

[0028] Figure 2 The microstructure of the heat affected zone of the marine atmospheric corrosion resistant steel of Example 1 of the present invention under the condition of a welding heat input of 35 kJ / cm;

[0029] Figure 3 The microstructure of the heat affected zone of the marine atmospheric corrosion resistant steel of Comparative Example 1 of the present invention under the condition of a welding heat input of 35 kJ / cm;

[0030] Figure 4 The weight loss of the marine atmospheric corrosion resistant steel of Example 1 of the present invention, the marine atmospheric corrosion resistant steel of Comparative Example 2 and Q235 steel;

[0031] Figure 5 The corrosion weight loss rates of the marine atmosphere corrosion resistant steel of Example 1 of the present invention, the marine atmosphere corrosion resistant steel of Comparative Example 2 and Q235 steel. DETAILED DESCRIPTION

[0032] The invention provides a marine atmosphere corrosion resistant steel, which comprises, by weight percentage, 0.03-0.08% C, 0.05-0.19% Si, 0.91-1.25% Mn, 1.2-1.5% Ni, 0.15-0.55% Cu, 0.21-0.40% Mo, 0.010-0.019% Nb, 0.02-0.04% V, 0.010-0.030% Ti, 0.020-0.050% Als, 0.0030-0.0060% N, ≤0.0040% O, ≤0.015% P, ≤0.005% S, and the balance Fe;

[0033] The contents of the elements in the marine atmosphere corrosion resistant steel meet the following conditions:

[0034] Carbon equivalent C eq ≤0.17, η1.3~1.6, α0.2~0.4, coastal atmospheric environment corrosion resistance index I≥1.2;

[0035] The C eq ={25[C]+0.56*(1.5[Mn]+[Si]+1.25[Ni]+1.7[Cu]+5[Mo]+5[Nb]+5[V])} / 25;

[0036] The η=3([Ni]*[Mo])+[Ni]*[Cu];

[0037] The α=([V] / 51+[Ti] / 48+[Nb] / 93) / ([C] / 12+[N] / 14);

[0038] The I=1 / {(1.0-0.16[C])*(1.05-0.05[Si])*(1.04-0.016[Mn])*(1.0-0.5[P])*(1 .0+1.9[S])*(1.0-0.1[Cu])*(1.0-0.12[Ni])*(1.0-0.3[Mo])*(1.0-1.7[Ti])}.

[0039] The marine atmospheric corrosion resistant steel provided by the present invention comprises 0.03-0.08% C, preferably 0.03-0.05%, and more preferably 0.035-0.045% C by weight percentage. In the present invention, by controlling the content of the C element, the welding crack sensitivity can be reduced, the MA component brittle phase in the welding heat affected zone can be reduced, and the low-temperature toughness of the welding heat affected zone can be improved; at the same time, the harsh steelmaking conditions are avoided, resulting in a decrease in the strength and yield strength ratio of the steel material, and the mechanical properties of the steel material are improved.

[0040] The marine atmospheric corrosion resistant steel provided by the present invention comprises Si in an amount of 0.05-0.19%, preferably 0.10-0.19%, and more preferably 0.15-0.18% by weight. In the present invention, Si can improve the strength of the steel material, improve the compactness of the rust layer, reduce the electrochemical corrosion reaction, and improve the corrosion resistance of the steel material; by controlling the content of the Si element, the MA component in the welding heat affected zone is reduced, and the size of the MA component is reduced to make it uniformly distributed, thereby improving the low-temperature toughness of the welding heat affected zone of the steel material.

[0041] The marine atmospheric corrosion resistant steel provided by the present invention comprises 0.91-1.25% Mn, preferably 0.91-1.20%, and more preferably 0.98-1.10% Mn by weight percentage. In the present invention, Mn can expand the austenite phase region, reduce the temperature of the phase transformation point Ar3, refine the ferrite grains, and improve the toughness of the steel; by controlling Mn, defects such as central segregation and looseness of the continuous casting billet can be avoided, the plastic toughness of the parent material and the welded joint can be improved, and the sensitivity of welding cracks can be reduced.

[0042] The marine atmospheric corrosion resistant steel provided by the present invention comprises 1.20-1.50% Ni, preferably 1.20-1.35%, and more preferably 1.22-1.30% Ni by weight percentage. In the present invention, the composite addition of Ni, Cu and Mo can significantly enhance the corrosion resistance of the steel material, improve the welding hot crack tendency caused by Cu and adjust the degree of reduction in low temperature toughness of the welding heat affected zone caused by excessive Mo; by controlling the content of Ni, the composite effect of Ni, Cu and Mo is improved.

[0043] The marine atmospheric corrosion resistant steel provided by the present invention comprises 0.15-0.55% Cu, preferably 0.15-0.40%, and more preferably 0.20-0.35% Cu by weight. In the present invention, the Cu and P elements form a dense amorphous layer on the surface of the steel plate, which inhibits the Cl - It can reduce the corrosion of steel plates, prolong the rust peeling time, and improve the corrosion resistance of steel plates; compounding with Ni elements can reduce the tendency of hot cracking of welds; by controlling the content of Cu elements, the corrosion resistance can be further improved and the tendency of hot cracking of welds can be reduced.

[0044] The marine atmospheric corrosion resistant steel provided by the present invention comprises 0.21-0.40% Mo, preferably 0.21-0.30%, and more preferably 0.25-0.28% Mo by weight percentage. In the present invention, Mo can refine austenite crystals, form fine bainite, improve the strength of the steel plate, significantly improve the density of the rust layer of the steel material, improve the corrosion resistance of the steel, and at the same time improve the toughness of the steel plate; the composite of Mo element and Ni element can improve the stability of the amorphous layer and generate high concentration MoO4 2- Ion blocking Cl - By controlling the Mo content, it further promotes the improvement of the mechanical properties and corrosion resistance of the steel plate, while avoiding excessive Mo content that reduces the low-temperature toughness of the heat-affected zone of weathering steel welding.

[0045] The marine atmospheric corrosion resistant steel provided by the present invention comprises Nb 0.010-0.019%, preferably 0.010-0.016%, and more preferably 0.013-0.015%, by weight percentage. In the present invention, Nb can be precipitated in the form of Nb(C,N) around TiN particles formed by Ti and N to improve the strength and toughness of the steel base material; by controlling the content of Nb, the formation of coarse upper bainite and large-sized blocky MA islands is avoided, which deteriorates the plastic toughness of the welding heat affected zone.

[0046] The marine atmospheric corrosion resistant steel provided by the present invention comprises V in an amount of 0.020-0.040%, preferably 0.020-0.035%, and more preferably 0.025-0.030%, by weight percentage. In the present invention, V can be combined with C and N to fix free [N] to form dispersed V (C, N) particles, which can be used as heterogeneous nucleation particles to promote the nucleation of block / acicular ferrite in the grain and grain boundary in the welding heat affected zone, refine the structure, inhibit coarse granular bainite, and improve low temperature toughness; by controlling the V content, the improvement of the low temperature toughness of the welding heat affected zone is further promoted.

[0047] The marine atmospheric corrosion resistant steel provided by the present invention comprises Ti in an amount of 0.01-0.03%, preferably 0.01-0.02%, and more preferably 0.014-0.017% by weight. In the present invention, Ti can be combined with N to generate TiN particles, which have the characteristics of high temperature stability, pin the original austenite grain boundaries of the welding heat affected zone, control the growth of the original austenite grains, refine the grains, and improve the toughness of the welding heat affected zone; by controlling the Ti content, it is avoided that the number of TiN particles is too small and the size is too small to effectively inhibit the growth of the original austenite crystals, and it is also avoided that the number of TiN particles is too large and the size is too large to become a crack source, but the toughness of the steel base material and the welding heat affected zone is reduced.

[0048] The marine atmospheric corrosion resistant steel provided by the present invention comprises 0.02-0.05% Als, preferably 0.02-0.04%, and more preferably 0.025-0.030% Als by weight percentage. In the present invention, Als is used as the main deoxidizer, mainly plays a deoxidation role in the steelmaking process, and can fix free [N] to improve welding low temperature toughness; by controlling the content of Als, the generation of a large number of Al2O3 inclusions is avoided, and at the same time, [N] is promoted to effectively combine with Ti and V, thereby improving the toughness and weldability of the steel plate.

[0049] The marine atmospheric corrosion resistant steel provided by the present invention comprises 0.003-0.006% N, preferably 0.003-0.005%, and more preferably 0.0034-0.0040% N by weight percentage. In the present invention, by controlling the N content, the precipitation of TiN and V (C, N) particles is promoted, and the weldability of the steel plate and the low temperature toughness of the welding heat affected zone are improved.

[0050] In terms of weight percentage, the marine atmosphere corrosion resistant rare earth steel provided by the present invention comprises P 0.001-0.015%, preferably 0.001-0.010%, and more preferably 0.002-0.003%. In the present invention, by controlling the content of P element, P element and Cu element are further promoted to form a dense amorphous layer on the surface of the steel plate, thereby inhibiting Cl - Further corrosion of the steel plate improves the corrosion resistance of the steel material.

[0051] In terms of weight percentage, the marine atmospheric corrosion resistant steel provided by the present invention comprises O≤0.004%, S≤0.005%, preferably O≤0.003%, S≤0.003%, and more preferably O≤0.002%, S≤0.002%. In the present invention, O and S are impurity elements, and by controlling their contents within the above range, the purity of the weathering steel can be improved, and the low-temperature toughness of the heat-affected zone of the weathering steel welding can be further improved.

[0052] The marine atmosphere corrosion resistant steel provided by the present invention includes the balance of Fe in terms of weight percentage. In the present invention, the Fe element is a matrix element of the marine atmosphere corrosion resistant steel.

[0053] In the present invention, the contents of the elements in the marine atmospheric corrosion resistant steel satisfy the following conditions at the same time: carbon equivalent C eq≤0.17, weather resistance η1.3~1.6, the number and size of the precipitated phase α0.2~0.4, and the coastal atmospheric environment corrosion resistance index I≥1.2; preferably Ceq≤0.16, η1.3~1.5, α0.2~0.35, I≥1.28; more preferably Ceq≤0.16, η1.3~1.5, α0.25~0.3, I≥1.3. In the present invention, by controlling the range of carbon equivalent Ceq, the welding performance of the steel plate is effectively improved, and the low-temperature toughness of the welding heat affected zone is further improved; by controlling the range of η, the welding performance of the steel plate is improved while ensuring the corrosion resistance of the steel plate; by controlling the range of α, the number and size of the second phase particles are controlled, thereby improving the low-temperature toughness of the welding heat affected zone and the toughness of the steel plate; by controlling the range of I, the corrosion resistance of the steel plate material is guaranteed.

[0054] The present invention improves the low-temperature toughness of the welding heat-affected zone of the marine atmospheric corrosion resistant steel by controlling the components and content of the steel material, and simultaneously improves the corrosion resistance and mechanical properties of the marine atmospheric corrosion resistant steel.

[0055] The present invention also provides a method for preparing the marine atmosphere corrosion resistant steel described in the above scheme, comprising the following steps:

[0056] (1) melting the raw materials and then casting to obtain a steel ingot;

[0057] (2) hot rolling the steel ingot obtained in step (1) to obtain a steel plate;

[0058] (3) The steel plate obtained in step (2) is subjected to tempering treatment to obtain marine atmosphere corrosion resistant steel.

[0059] The present invention melts the raw materials and then casts them to obtain steel ingots.

[0060] The present invention has no particular limitation on the type of the raw materials, and any raw materials for steelmaking known to those skilled in the art may be used.

[0061] In the present invention, the smelting temperature is preferably 1550-1600°C, more preferably 1560-1575°C; the smelting time is preferably 70-90°C, more preferably 75-80°C; the smelting vacuum is preferably 10-20 Pa, more preferably 10-15 Pa. In the present application, by controlling the smelting process parameters, the raw materials can be fully melted and uniformly mixed, and the performance of the steel material is further improved.

[0062] The present invention has no special limitation on the casting operation, and the technical scheme for casting steel materials well known to those skilled in the art may be adopted.

[0063] After obtaining the steel ingot, the present invention hot-rolls the steel ingot to obtain a steel plate.

[0064] The present invention preferably heats and holds the steel billet in sequence before the hot rolling, the heating rate is preferably 10-15°C / s, more preferably 10-12°C / s; the holding temperature is preferably 1150-1200°C, more preferably 1160-1180°C; the holding time is preferably 2-3h, more preferably 2-2.5h. In the present invention, by limiting the heating temperature, heating rate and holding time of the steel ingot, the internal structure of the steel ingot is further improved, the steel ingot is completely austenitized, and the low-temperature toughness of the heat-affected zone of the steel material is further improved.

[0065] In the present invention, the hot rolling preferably includes rough rolling and finish rolling performed sequentially. In the present invention, uniform rolling of the steel plate material is ensured by sequentially performing rolling stages, thereby further improving the performance of the steel plate material.

[0066] In the present invention, the starting rolling temperature of the rough rolling is preferably 1100-1120°C, more preferably 1105-1110°C; the final rolling temperature of the rough rolling is preferably 1000-1080°C, more preferably 1040-1060°C; the cumulative reduction ratio of the rough rolling is preferably 35% or more, more preferably 40% or more. In the present invention, by controlling the process parameters of the rough rolling process, the austenite is fully recrystallized in the rough rolling stage, the grain refinement of the steel material is achieved, the microstructural defects of the steel material are eliminated, and the mechanical properties of the steel material are further improved.

[0067] In the present invention, the start rolling temperature of the finishing rolling is preferably 870-930°C, more preferably 890-910°C; the final rolling temperature of the finishing rolling is preferably 830-850°C, more preferably 835-845°C; the cumulative reduction ratio of the finishing rolling is preferably above 30%, more preferably above 35%. In the present invention, by controlling the process parameters of the finishing rolling process, the grain refinement of the steel material is further achieved, the microstructural defects of the steel material are eliminated, and the mechanical properties of the steel material are further improved.

[0068] After hot rolling, the hot rolled product is preferably cooled to obtain a steel plate. The cooling is preferably to first cool the steel billet with an initial cooling temperature of 765-785°C to a final cooling temperature of 450-600°C at a cooling rate of 10-20°C / s, and then air-cool to room temperature. In the present invention, by controlling the parameters of the cooling process, the grains are further refined, and the mechanical properties of the steel material and the low-temperature toughness of the welding heat affected zone are improved.

[0069] After obtaining the steel plate, the present invention performs a tempering treatment on the steel plate to obtain marine atmosphere corrosion resistant steel.

[0070] In the present invention, the temperature of the tempering treatment is preferably 400-550°C, more preferably 450-500°C; the time of the tempering treatment is preferably (h+40) min, where h is the thickness of the steel plate, and the unit of h is mm. In the present invention, by limiting the temperature and time of the tempering treatment, the influence of the rolling process on the steel plate material is eliminated, and the mechanical properties of the steel plate material and the low-temperature toughness of the welding heat affected zone are further improved.

[0071] The preparation method of marine atmospheric corrosion resistant steel provided by the present invention promotes the contact of various elements in the steel plate material, further improves the corrosion resistance, mechanical properties and low-temperature toughness of the steel plate material and the welding heat affected zone, so that the marine atmospheric corrosion resistant steel can meet the actual use requirements.

[0072] The present invention also provides the use of the above marine atmospheric corrosion resistant steel in a marine atmospheric environment. The marine atmospheric corrosion resistant steel provided by the present invention can be used in the construction of cross-sea bridges and the manufacture of equipment such as storage tanks, pipelines and reactors in a marine environment.

[0073] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0074] Example 1

[0075] The composition of the marine atmosphere corrosion resistant steel of this embodiment is shown in Table 1, which is composed of C0.04%, Si0.18%, Mn 0.92%, Ni 1.2%, Cu 0.35%, Mo 0.3%, Nb 0.019%, V 0.023%, Ti 0.014%, Als 0.02%, N 0.003%, P 0.002%, O 0.0012%, P 0.002%, S 0.003%, and the balance Fe, by weight percentage;

[0076] The contents of the elements in the marine atmosphere corrosion resistant steel meet the following conditions:

[0077] C eq =0.16%, eta=1.5, α=0.27, I=1.28;

[0078] The method for preparing the marine atmosphere corrosion resistant steel comprises the following steps:

[0079] (1) Mixing raw materials in a vacuum reactor, smelting them under the conditions of 10 Pa and 1600° C. until the raw materials are melted to obtain molten steel, refining the molten steel for 90 minutes, filling it with argon gas and then casting to obtain a square steel ingot;

[0080] (2) The steel ingot obtained in the step (1) is heated to 1150° C. at a rate of 10° C. / s, kept at this temperature for 2 h, to obtain a completely austenitized steel billet material, and then subjected to rough rolling and finish rolling in sequence and cooled to obtain a steel plate with a thickness of 24 mm; wherein the starting rolling temperature of the rough rolling is 1120° C., the final rolling temperature of the rough rolling is 1050° C., and the cumulative reduction ratio of the rough rolling is 35%; wherein the starting rolling temperature of the finish rolling is 890° C., the final rolling temperature of the finish rolling is 840° C., and the cumulative reduction ratio of the finish rolling is 30%; wherein the cooling is to first cool the steel billet with a starting cooling temperature of 770° C. to a final cooling temperature of 522° C. at a rate of 12° C. / s, and then air cool to room temperature.

[0081] (3) The steel plate obtained in step (2) is tempered at 500° C. for 64 minutes to obtain marine atmosphere corrosion resistant steel.

[0082] The base material of the marine atmosphere corrosion resistant steel obtained in Example 1 was observed using an Axiover-200MAT metallographic microscope, and the microstructure diagram was obtained as shown in FIG. Figure 1 As shown. Figure 1 It can be seen that the structure of the marine atmosphere corrosion resistant steel obtained in Example 1 is mainly granular bainite and a small amount of acicular ferrite, which indicates that the steel plate obtained in Example 1 has excellent mechanical properties.

[0083] Embodiments 2 to 6

[0084] The difference between Examples 2 to 6 and Example 1 lies in the weight percentage of each component in the marine atmosphere corrosion resistant steel and the parameters of rolling, cooling and tempering treatment.

[0085] Comparative Examples 1 to 3

[0086] The difference between Comparative Examples 1 to 3 and Example 1 lies in the weight percentage of each component in the marine atmosphere corrosion resistant steel and the parameters of rolling, cooling and tempering treatment.

[0087] The compositions of the marine atmosphere corrosion resistant steels in Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1.

[0088] Table 1 Composition / % of marine atmosphere corrosion resistant steel in Examples 1 to 6 and Comparative Examples 1 to 3

[0089]

[0090]

[0091] The rolling, cooling and tempering treatment parameters of the marine atmosphere corrosion resistant steel in Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 2.

[0092] Table 2 Rolling, cooling and tempering parameters of marine atmospheric corrosion resistant steel in Examples 1 to 6 and Comparative Examples 1 to 3

[0093]

[0094]

[0095] The mechanical properties of the marine atmosphere corrosion resistant steels in Examples 1 to 6 and Comparative Examples 1 to 3 were tested by a room temperature tensile test at a tensile rate of 3 mm / min on an MTS universal testing machine and a -40°C impact performance test on a JBN-300B impact testing machine. The results are shown in Table 3.

[0096] Table 3 Mechanical properties of marine atmospheric corrosion resistant steel in Examples 1 to 6 and Comparative Examples 1 to 3

[0097]

[0098] It can be seen from Table 3 that by controlling the components of marine atmospheric corrosion resistant steel, the low-temperature toughness of marine atmospheric corrosion resistant steel can be improved and the mechanical properties of the steel material can be effectively improved.

[0099] Gleeble thermal simulation test specimens of 10.5*10.5*80mm were cut from the steel plates with a thickness of 24mm after finish rolling in Examples 1 to 6 and Comparative Examples 1 to 3, and welding with a typical heat input of 15KJ / cm for manual gas shielded welding and a typical heat input of 35KJ / cm for submerged arc welding was simulated; the thermal simulation test specimens were processed into standard impact specimens of 10*10*55mm, and a -40℃ impact performance test was carried out on a JBN-300B impact testing machine. The low-temperature toughness results of the heat-affected zone of the marine atmospheric corrosion-resistant steel weld are shown in Table 4.

[0100] Table 4 Low temperature toughness of the weld heat affected zone of marine atmospheric corrosion resistant steel in Examples 1 to 6 and Comparative Examples 1 to 3

[0101]

[0102]

[0103] It can be seen from Table 4 that by controlling the composition of the steel material, the -40°C impact energy of the welding heat affected zone of the marine atmospheric corrosion resistant steel provided in Examples 1 to 6 of the present invention under simulated typical heat input conditions is greater than 150 J, thereby improving the low-temperature toughness of the welding heat affected zone.

[0104] The Axiover-200MAT metallographic microscope was used to observe the welding heat affected zone of the marine atmospheric corrosion resistant steel obtained in Example 1, and the microstructure of the welding heat affected zone of the marine atmospheric corrosion resistant steel in Example 1 under the condition of welding heat input of 35 kJ / cm was obtained as follows: Figure 2 As shown. Figure 2 It can be seen that the steel material obtained in Example 1 has a multiphase structure of granular bainitic ferrite, lath bainite, a small amount of acicular ferrite and MA components, which can effectively improve the low-temperature toughness, corrosion resistance and mechanical properties of the welding heat affected zone of the marine atmospheric corrosion-resistant steel.

[0105] The Axiover-200MAT metallographic microscope was used to observe the welding heat affected zone of the marine atmospheric corrosion resistant steel obtained in Comparative Example 1, and the microstructure of the welding heat affected zone of the marine atmospheric corrosion resistant steel in Comparative Example 1 under the condition of welding heat input of 35 kJ / cm was obtained as follows: Figure 3 As shown. Figure 3 It can be seen that the microstructure of the marine atmospheric corrosion-resistant steel of Comparative Example 1 is coarse granular bainite and lath bainite, which is a multiphase structure composed of coarse bainite, ferrite soft phase matrix and MA component hard phase. When this structure is subjected to impact load, microcracks will nucleate at the soft-hard phase interface and extend in the matrix along the coarse bainite and ferrite, eventually leading to brittle fracture and making the low-temperature toughness of the welding heat affected zone poor.

[0106] The marine atmospheric corrosion-resistant steel obtained in Example 1 and Comparative Example 2 and the commercially available Q235 grade steel were subjected to a typical coastal atmospheric environment periodic immersion accelerated corrosion test. According to Part VI of the Chinese Materials and Testing Group Standard T / CSTM 00046.1-2018 / T / CSCP 0035.1-2018: General requirements for simulated dry-wet alternating corrosion tests, a 3.5% NaCl solution was used to simulate the marine atmospheric environment, and five cycles of 24 / 96 / 168 / 216 / 360h dry-wet alternating accelerated corrosion tests simulating a typical marine atmospheric environment were carried out. The standard for the dry-wet alternating accelerated corrosion test is TB / T2375-1993 "Cyclic Infiltration Corrosion Test Method for Weathering Steel for Railways" and GB / T19746-2018 "Corrosive Salt Solution Cyclic Immersion Test for Metals and Alloys". The corrosion weight loss and corrosion weight loss rate of the marine atmospheric corrosion-resistant rare earth steel and the commercially available Q235 grade steel of Example 1 and Comparative Example 2 are shown in Table 5.

[0107] Table 5 Corrosion resistance of marine atmospheric corrosion resistant steel and Q235 grade steel of Example 1 and Comparative Example 2

[0108]

[0109] It can be seen from Table 5 that the marine atmospheric corrosion resistant steel of Example 1 reduces Ni by 0.4% compared with the marine atmospheric corrosion resistant steel of Comparative Example 2, saving costs, but the corrosion resistance of the steel material has not decreased significantly; and the marine atmospheric corrosion resistant steel prepared in Example 1 has a corrosion resistance 3 to 4 times higher than that of the Q235 grade steel in the prior art, and has good corrosion resistance.

[0110] The corrosion weight loss of the marine atmospheric corrosion resistant steel of Example 1, the marine atmospheric corrosion resistant steel of Comparative Example 2 and the Q235 steel is as follows: Figure 4 As shown. Figure 4 It can be seen that the corrosion resistance of the marine atmosphere corrosion resistant steel provided by the present invention is significantly better than that of Q235 steel.

[0111] The corrosion weight loss rates of the marine atmospheric corrosion resistant steel of Example 1, the marine atmospheric corrosion resistant steel of Comparative Example 2 and the Q235 steel are as follows: Figure 5 As shown. Figure 5 It can be seen that the corrosion weight loss rate of the marine atmospheric corrosion resistant steel provided by the present invention is significantly lower than that of Q235 steel, that is, the corrosion resistance of the marine atmospheric corrosion resistant steel of the present invention is significantly better than that of Q235 steel.

[0112] In summary, the marine atmospheric corrosion resistant steel provided by the present invention provides weathering steel with good low-temperature toughness, excellent corrosion resistance and excellent mechanical properties.

[0113] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A marine atmosphere corrosion resistant steel, comprising, by weight percentage, C 0.03-0.08%, Si 0.05-0.19%, Mn 0.91-1.25%, Ni 1.2-1.5%, Cu 0.15-0.55%, Mo 0.21-0.40%, Nb 0.010-0.019%, V 0.02-0.04%, Ti 0.01-0.03%, Als 0.02-0.05%, N 0.003-0.006%, P 0.001-0.015%, O≤0.004%, S≤0.005%, and the balance Fe; The content of each element in the marine atmospheric corrosion resistance meets the following conditions: Carbon equivalent C eq ≤0.17, weather resistance η1.3~1.6, the number and size of precipitated phase α0.2~0.4, coastal atmospheric environment corrosion resistance index I≥1.2; The C eq ={25[C]+0.56*(1.5[Mn]+[Si]+1.25[Ni]+1.7[Cu]+5[Mo]+5[Nb]+5[V])} / 25; The η=3([Ni]*[Mo])+[Ni]*[Cu]; The α=([V] / 51+[Ti] / 48+[Nb] / 93) / ([C] / 12+[N] / 14); The I=1 / {(1.0-0.16[C])*(1.05-0.05[Si])*(1.04-0.016[Mn])*(1.0-0.5[P])*(1 .0+1.9[S])*(1.0-0.1[Cu])*(1.0-0.12[Ni])*(1.0-0.3[Mo])*(1.0-1.7[Ti])}.

2. The marine atmosphere corrosion resistant steel according to claim 1, characterized in that: Calculated by weight percentage, it includes C 0.03-0.05%, Si 0.10-0.19%, Mn 0.91-1.20%, Ni 1.20-1.35%, Cu 0.15-0.40%, Mo 0.21-0.30%, Nb 0.010-0.016%, V 0.020-0.035%, Ti 0.01-0.02%, Als 0.020-0.040%, N 0.003-0.005%, P 0.001-0.010%, O≤0.003%, S≤0.003%, and the balance Fe.

3. The marine atmosphere corrosion resistant steel according to claim 2, characterized in that: Calculated by weight percentage, it includes C 0.035-0.045%, Si 0.15-0.18%, Mn 0.98-1.10%, Ni 1.22-1.30%, Cu 0.20-0.35%, Mo 0.25-0.28%, Nb 0.013-0.015%, V 0.025-0.030%, Ti 0.014-0.017%, Als 0.025-0.030%, N 0.0034-0.0040%, P 0.002-0.003%, O≤0.002%, S≤0.002%, and the balance Fe.

4. The method for preparing the marine atmosphere corrosion resistant steel according to any one of claims 1 to 3, comprising the following steps: (1) melting the raw materials and then casting to obtain a steel ingot; (2) hot rolling the steel ingot obtained in step (1) to obtain a steel plate; (3) The steel plate obtained in step (2) is subjected to tempering treatment to obtain marine atmosphere corrosion resistant steel.

5. The preparation method according to claim 4, characterized in that: Before the hot rolling in step (2), the steel billet is heated and kept warm in sequence, the keeping temperature is 1150-1200° C., and the keeping time is 2-3 hours.

6. The preparation method according to claim 4, characterized in that: The hot rolling in step (2) includes rough rolling and finish rolling performed sequentially.

7. The preparation method according to claim 6, characterized in that: The starting rolling temperature of the rough rolling is 1100-1120° C., and the finishing rolling temperature is 1000-1080° C.; the cumulative reduction ratio of the rough rolling is above 35%.

8. The preparation method according to claim 6, characterized in that: The start rolling temperature of the finishing rolling is 870-930° C., and the final rolling temperature is 830-850° C.; the cumulative reduction ratio of the finishing rolling is more than 30%.

9. The preparation method according to claim 4, characterized in that: The temperature of the tempering treatment in the step (3) is 400-550° C., and the time of the tempering treatment is (h+40) min, where h is the thickness of the steel plate obtained in the step (2), and the unit of h is mm.

10. Use of the marine atmosphere corrosion resistant steel according to any one of claims 1 to 3 or the marine atmosphere corrosion resistant steel prepared according to the preparation method according to claims 4 to 9 in a marine atmosphere environment.

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