Marine atmosphere corrosion resistant rare earth steel and preparation method and application thereof

Abstract

The invention provides marine atmosphere corrosion resistant rare earth steel and a preparation method and application thereof, and belongs to the technical field of corrosion resistant steel. The invention provides rare earth steel resistant to marine atmosphere corrosion. The rare earth steel resistant to marine atmosphere corrosion comprises C, Si, Mn, Ni, Cu, Mo, Nb, V, Ti, Ce, Als, N, P, O, S and Fe according to a certain mass content. The content of each element in the weathering resistant steel meets the following conditions: alpha is 50-110, eta is 4-6, and I is greater 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 results of the embodiment show that the marine atmosphere corrosion resistant rare earth steel is excellent in corrosion resistance, the Charpy impact of a welding heat affected zone at-40 DEG C under typical welding heat input is larger than or equal to 100 J under the welding condition that the heat input is 15-35 kJ / cm, and the marine atmosphere corrosion resistant rare earth 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 a rare earth steel resistant to marine atmospheric corrosion, and a preparation method and application thereof. Background Art

[0002] The climate environment in coastal areas 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. Traditional weathering steel cannot form a stable protective rust layer. 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, which ensures the corrosion resistance of the steel material through a high content of Ni, but Ni will lead to poor welding performance of the steel material; CN104046898A discloses a high-performance marine climate resistant steel plate and its manufacturing method, which has excellent corrosion resistance, and the Charpy impact energy of the welding heat affected zone at -40°C is ≥100J; but the low-temperature toughness of the welding heat affected zone of the prepared weathering steel still cannot meet the actual use requirements, and the content of precious metal Ni is relatively high, the weldability of the steel plate is poor, and the molten pool fluidity is low, which increases the difficulty of the welding process. Summary of the invention

[0004] The object of the present invention is to provide a rare earth steel resistant to marine atmospheric corrosion and a preparation method and application thereof. The rare earth steel resistant to marine atmospheric corrosion provided by the present invention has good corrosion resistance and effectively improves the low-temperature toughness of the welding heat affected zone.

[0005] The invention provides a marine atmosphere corrosion resistant rare earth steel, which comprises, by weight percentage, C0.03-0.08%, Si 0.05-0.19%, Mn 0.5-0.9%, Ni 1.00-1.19%, Cu 0.15-0.55%, Mo 0.21-0.40%, Nb 0.035-0.100%, V 0.02-0.04%, Ti 0.01-0.03%, Ce 0.003-0.008%, Als 0.02-0.05%, N 0.006-0.008%, P 0.001-0.015%, O≤0.004%, S≤0.005%, and the balance Fe;

[0006] The contents of the elements in the marine atmosphere corrosion resistant rare earth steel meet the following conditions:

[0007] The mass and size of inclusions are α50~110, the number and size of precipitates are η4~6, and the corrosion resistance index of coastal atmospheric environment is I≥1.2;

[0008] The α=([Mn] / 55+[Ce] / 140+[Al] / 27) / ([S] / 32+[O] / 16);

[0009] Said η=[V] / ([C]+[N])+[Ti] / [N]+[Nb] / ([C]+[N]);

[0010] 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])}

[0011] Preferably, the marine atmosphere corrosion resistant rare earth steel comprises, by weight percentage, C0.03-0.06%, Si0.08-0.19%, Mn 0.6-0.9%, Ni 1.0-1.1%, Cu 0.20-0.55%, Mo0.25-0.40%, Nb0.05-0.10%, V 0.02-0.03%, Ti 0.015-0.030%, Ce 0.003-0.006%, Als 0.02-0.04%, N 0.0060-0.0075%, P 0.001-0.010%, O≤0.003%, S≤0.003%, and the balance Fe.

[0012] Preferably, the marine atmosphere corrosion resistant rare earth steel comprises, by weight percentage, C0.040-0.045%, Si 0.10-0.15%, Mn 0.75-0.90%, Ni 1.03-1.08%, Cu 0.30-0.45%, Mo 0.3-0.4%, Nb 0.050-0.085%, V 0.024-0.030%, Ti 0.020-0.025%, Ce0.0030-0.0045%, Als 0.02-0.03%, N 0.006-0.007%, P 0.002-0.003%, O≤0.002%, S≤0.002%, and the balance Fe.

[0013] The present invention also provides a method for preparing the marine atmosphere corrosion resistant rare earth steel described in the above technical solution, comprising the following steps:

[0014] (1) melting the raw materials and then casting to obtain a steel ingot;

[0015] (2) hot rolling the steel ingot obtained in step (1) to obtain rare earth steel resistant to marine atmosphere corrosion.

[0016] Preferably, the smelting temperature in step (1) is 1550-1600° C., the smelting time is 60-90 min, and the smelting vacuum is 10-20 Pa.

[0017] Preferably, the steel billet is heated and kept warm in sequence before hot rolling in step (2), the keeping temperature is 1150-1200° C., and the keeping time is 3-5 hours.

[0018] Preferably, the hot rolling in step (2) includes rough rolling and finish rolling performed sequentially.

[0019] Preferably, the starting rolling temperature of the rough rolling is 1100-1120° C., and the finishing rolling temperature is 1020-1080° C.; and the cumulative reduction ratio of the rough rolling is above 35%.

[0020] 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%.

[0021] The present invention also provides the use of the marine atmosphere corrosion resistant rare earth steel described in the above technical solution or the marine atmosphere corrosion resistant rare earth steel prepared according to the preparation method described in the above technical solution in a marine atmosphere environment.

[0022] The invention provides a rare earth steel resistant to marine atmospheric corrosion, which comprises, by weight percentage, 0.03-0.08% C, 0.05-0.19% Si, 0.5-0.9% Mn, 1.00-1.19% Ni, 0.15-0.55% Cu, 0.21-0.40% Mo, 0.035-0.100% Nb, 0.02-0.04% V, 0.01-0.03% Ti, 0.003-0.008% Ce, 0.02-0.05% Al, 0.006-0.008% N, 0.01-0.03% Pb, 0.02-0.04% Ti, 0.01-0.03% Ce, 0.006-0.008% Al, 0.01-0.03% Pb, 0.02-0.04% Ti, 0.01-0.03% Ce, 0.006-0.008% Pb, 0.02-0.04% Pb, 0.02-0.04% Ti, 0.01-0.03% Ce, 0.006-0.008% Al, 0.01-0.03% Pb, 0.02-0.04% Pb, 0.02-0.04% 0.001~0.015%, O≤0.004%, S≤0.005%, and the balance Fe; the contents of each element in the marine atmospheric corrosion resistant rare earth steel meet the following conditions: the mass and size of inclusions α50~110, the number and size of precipitates η4~6, and the coastal atmospheric environment corrosion resistance index V≥1.2; the α=([Mn] / 55+[Ce] / 140+[Al] / 27) / ([S] / 32+[O] / 16); the η=[V] / ([ C]+[N])+[Ti] / [N]+[Nb] / ([C]+[N]); 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])}. The marine atmosphere corrosion resistant rare earth steel provided by the present invention reduces the welding crack sensitivity by controlling the contents of C and Si, reduces the brittle phase of the MA component in the welding heat affected zone, and improves the low-temperature toughness of the welding heat affected zone; through the composite action between Ni, Cu and Mo, 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 are improved, and the corrosion resistance of the steel material is improved; the Cu element and the P element will form a dense amorphous layer on the surface of the steel plate, inhibiting the Cl - Further corrosion of the steel plate prolongs the rust layer peeling time and improves the corrosion resistance of the steel material; the stability of the amorphous layer is improved through the composite action of Mo and Ni, and high-concentration MoO4 is generated. 2- Ion blocking Cl -Permeability, improve corrosion resistance; an appropriate amount of Ti element can form TiN particles with high temperature stability with N, pin the original austenite grain boundary in the welding heat affected zone, control the growth of the original austenite grains, refine the grains, 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 the free [N], forming dispersed V (C, N) particles as heterogeneous nucleation particles, promoting the nucleation of block / acicular ferrite in the grain and grain boundary in the welding heat affected zone, refining the organization and inhibiting coarse granular bainite, and improving the low temperature toughness of the welding heat affected zone of the steel material; through the rare earth element Ce, the segregation of P is reduced, the atmospheric corrosion resistance of the steel is improved, and at the same time, the morphology of inclusions is controlled, the lattice mismatch is reduced, the nucleation of acicular ferrite is promoted, the plastic toughness of the steel is improved, the steel material has better weldability, and the low temperature toughness of the welding heat affected zone is improved. The results of the embodiment show that the corrosion resistance of the marine atmospheric corrosion resistant rare earth steel provided by the present invention is excellent, and the corrosion weight loss of the steel material is 122mg / cm at 360h. 2 The corrosion weight loss rate is 0.34 mg / cm 2 *h, the corrosion resistance is 3 to 4 times higher than that of ordinary C-Mn steel materials; and under the welding condition of heat input of 15-35kJ / cm, the Charpy impact of the welding heat affected zone at -40°C under typical welding heat input can reach 171J, and it has good low-temperature toughness; in addition, the rare earth steel resistant to marine atmospheric corrosion provided by the present invention has excellent mechanical properties, yield strength ≥345MPa, tensile strength ≥490MPa, yield strength ratio of 0.7 to 0.71, -40°C Charpy V-notch impact energy ≥200J, and impact fracture fiber section rate ≥85%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a microstructure diagram of the marine atmosphere corrosion resistant rare earth steel of Example 1 of the present invention;

[0024] Figure 2 The microstructure of the heat affected zone of the marine atmosphere corrosion resistant rare earth steel of Example 1 of the present invention under the condition of a welding heat input of 35 kJ / cm;

[0025] Figure 3 The microstructure of the heat affected zone of the marine atmosphere corrosion resistant rare earth steel of Comparative Example 1 of the present invention under the condition of a welding heat input of 35 kJ / cm;

[0026] Figure 4 The weight loss of the marine atmosphere corrosion resistant rare earth steel of Example 1 of the present invention, the marine atmosphere corrosion resistant rare earth steel of Comparative Example 2 and Q235 steel;

[0027] Figure 5 The corrosion weight loss rates of the marine atmosphere corrosion resistant rare earth steel of Example 1 of the present invention, the marine atmosphere corrosion resistant rare earth steel of Comparative Example 2, and Q235 steel. DETAILED DESCRIPTION

[0028] The invention provides a marine atmosphere corrosion resistant rare earth steel, which comprises, by weight percentage, C0.03-0.08%, Si 0.05-0.19%, Mn 0.5-0.9%, Ni 1.00-1.19%, Cu 0.15-0.55%, Mo 0.21-0.40%, Nb 0.035-0.100%, V 0.02-0.04%, Ti 0.01-0.03%, Ce 0.003-0.008%, Als 0.02-0.05%, N 0.006-0.008%, P 0.001-0.015%, O≤0.004%, S≤0.005%, and the balance Fe;

[0029] The contents of the elements in the marine atmosphere corrosion resistant rare earth steel meet the following conditions:

[0030] The mass and size of inclusions are α50~110, the number and size of precipitates are η4~6, and the corrosion resistance index of coastal atmospheric environment is I≥1.2;

[0031] The α=([Mn] / 55+[Ce] / 140+[Al] / 27) / ([S] / 32+[O] / 16);

[0032] Said η=[V] / ([C]+[N])+[Ti] / [N]+[Nb] / ([C]+[N]);

[0033] 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])}.

[0034] The marine atmosphere corrosion resistant rare earth steel provided by the present invention comprises 0.03-0.08% C, preferably 0.03-0.06%, and more preferably 0.040-0.045% 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.

[0035] The marine atmosphere corrosion resistant rare earth steel provided by the present invention comprises Si 0.05-0.19%, preferably 0.08-0.19%, and more preferably 0.10-0.15%, by weight percentage. 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.

[0036] The marine atmosphere corrosion resistant rare earth steel provided by the present invention comprises 0.5-0.9% Mn, preferably 0.6-0.9%, and more preferably 0.75-0.90% Mn by weight percentage. In the present invention, Mn can improve the strength of the steel, 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.

[0037] The marine atmosphere corrosion resistant rare earth steel provided by the present invention comprises Ni 1.00-1.19%, preferably 1.0-1.1%, and more preferably 1.03-1.08%, by weight percentage. In the present invention, Ni is added in combination with Cu and Mo, which can significantly enhance the corrosion resistance of the steel material, improve the welding hot crack tendency caused by Cu and the degree of reduction in low temperature toughness of the welding heat affected zone caused by excessive Mo; and by controlling the content of Ni, the composite effect of Ni, Cu and Mo is improved.

[0038] The marine atmosphere corrosion resistant rare earth steel provided by the present invention comprises 0.15-0.55% Cu, preferably 0.20-0.55%, and more preferably 0.30-0.45% Cu. In the present invention, 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.

[0039] In terms of weight percentage, the marine atmosphere corrosion resistant rare earth steel provided by the present invention includes Mo0.21-0.40%, preferably 0.25-0.40%, and more preferably 0.3-0.4%. 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.

[0040] The marine atmosphere corrosion resistant rare earth steel provided by the present invention comprises Nb 0.035-0.100%, preferably 0.05-0.10%, and more preferably 0.050-0.085%, 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, thereby improving 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, thereby deteriorating the plastic toughness of the welding heat affected zone.

[0041] In terms of weight percentage, the marine atmospheric corrosion resistant rare earth steel provided by the present invention includes V0.020-0.040%, preferably 0.02-0.03%, and more preferably 0.024-0.030%. 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, it is further promoted to improve the low-temperature toughness of the welding heat affected zone.

[0042] The marine atmosphere corrosion resistant rare earth steel provided by the present invention comprises Ti0.010-0.030%, preferably 0.015-0.030%, and more preferably 0.020-0.025%, by weight percentage. 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.

[0043] The marine atmosphere corrosion resistant rare earth steel provided by the present invention includes 0.003-0.008% Ce, preferably 0.003-0.006%, and more preferably 0.0030-0.0045% Ce by weight percentage. In the present invention, Ce can control the morphology of inclusions, reduce the lattice mismatch, promote the nucleation of acicular ferrite, improve the plasticity and toughness of steel, especially the transverse performance, and also make the steel have better stamping and weldability, reduce the segregation of P, improve the corrosion resistance of steel and improve toughness and plasticity; by controlling the content of Ce, it is avoided that the inclusion morphology grows abnormally, but seriously deteriorates the performance of the steel plate.

[0044] The marine atmosphere corrosion resistant rare earth steel provided by the present invention comprises 0.02-0.05% Als, preferably 0.02-0.04%, and more preferably 0.02-0.03% 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.

[0045] The marine atmosphere corrosion resistant rare earth steel provided by the present invention comprises N0.006-0.008%, preferably 0.0060-0.0075%, and more preferably 0.006-0.007%, 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.

[0046] 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.

[0047] In terms of weight percentage, the marine atmosphere corrosion resistant rare earth 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.

[0048] In terms of weight percentage, the marine atmosphere corrosion resistant rare earth steel provided by the present invention includes the balance of Fe. In the present invention, the Fe element is a matrix element of the marine atmosphere corrosion resistant rare earth steel.

[0049] In the present invention, the content of each element in the rare earth steel resistant to marine atmospheric corrosion satisfies the following conditions at the same time: the mass and size of inclusions are α50~110, the number and size of precipitates are η4~6, and the marine atmospheric environment corrosion resistance index I≥1.2; preferably α50~100, η4~5.5, I≥1.28; more preferably α75~95, η4.5~5.5, I≥1.3. In the present invention, by controlling the range of α, the number of inclusion forms in the steel plate is regulated, so that the size of the inclusions modified by rare earth can promote the nucleation ability of acicular ferrite and refine the structure, thereby improving the low-temperature toughness of the welding heat affected zone and the toughness of the steel plate; by controlling the range of η, the number and size of the second phase particles are controlled, and the low-temperature toughness of the welding heat affected zone and the toughness of the steel plate are further improved. If the η value is too small, the number of second phase particles is small and the size is small, which cannot play a role in pinning the original austenite grain boundary and cannot provide sufficient heterogeneous nucleation particles, which is not good for improving the formation of acicular ferrite in the welding heat affected zone. If the η value is too large, the number of second phase particles (Ti, Nb, V) (C, N) is large and the size is large. The large-sized second phase particles may become the starting point of impact fracture cracks, and will also seriously damage 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.

[0050] The present invention improves the corrosion resistance of the marine atmosphere corrosion resistant rare earth steel and the low temperature toughness of the welding heat affected zone by controlling the components and content of the steel material, and simultaneously improves the mechanical properties of the marine atmosphere corrosion resistant rare earth steel.

[0051] The present invention also provides a method for preparing the marine atmosphere corrosion resistant rare earth steel described in the above scheme, comprising the following steps:

[0052] (1) melting the raw materials and then casting to obtain a steel ingot;

[0053] (2) hot rolling the steel ingot obtained in step (1) to obtain rare earth steel resistant to marine atmosphere corrosion.

[0054] The present invention melts the raw materials and then casts them to obtain steel ingots.

[0055] 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.

[0056] In the present invention, the smelting temperature is preferably 1550-1600°C, more preferably 1560-1580°C; the smelting time is preferably 60-90 min, more preferably 70-80 min; 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.

[0057] 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.

[0058] After obtaining the steel ingot, the present invention performs hot rolling on the steel ingot to obtain rare earth steel resistant to marine atmospheric corrosion.

[0059] The present invention preferably heats and holds the steel billet in sequence before the hot rolling, and 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 3-5h, more preferably 3.5-4h. In the present invention, by limiting the heating temperature, heating rate and holding time of the steel billet, the internal structure of the steel billet is further improved, the steel billet is completely austenitized, and the low-temperature toughness of the heat-affected zone of the steel material is further improved.

[0060] 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.

[0061] In the present invention, the starting rolling temperature of the rough rolling is preferably 1100-1120°C, more preferably 1110-1115°C; the final rolling temperature of the rough rolling is preferably 1020-1080°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.

[0062] 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.

[0063] 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.

[0064] The preparation method of marine atmospheric corrosion resistant rare earth 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 welding heat affected zone of the steel plate material, so that the marine atmospheric corrosion resistant rare earth steel can meet actual use requirements.

[0065] The present invention also provides the use of the above rare earth steel resistant to marine atmosphere corrosion in marine atmosphere environment. The rare earth steel resistant to marine atmosphere corrosion provided by the present invention can be applied to offshore unpainted bridges and coastal railway construction.

[0066] 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.

[0067] Example 1

[0068] The composition of the marine atmosphere corrosion resistant rare earth steel of this embodiment is shown in Table 1, which is composed of C 0.045%, Si 0.19%, Mn 0.52%, Ni 1.1%, Cu 0.2%, Mo 0.22%, Nb 0.066%, V 0.023%, Ti 0.02%, Ce 0.003%, Als 0.03%, N 0.006%, O 0.0016%, P 0.002%, S 0.003%, and the balance Fe, by weight percentage;

[0069] The contents of the elements in the marine atmosphere corrosion resistant rare earth steel meet the following conditions:

[0070] α=54.6, η=5.1, I=1.22;

[0071] The method for preparing the rare earth steel resistant to marine atmospheric corrosion comprises the following steps:

[0072] (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;

[0073] (2) The steel ingot obtained in the step (1) is heated to 1150°C at a rate of 10°C / s, kept warm for 3 hours to obtain a fully austenitized steel billet material, and then subjected to rough rolling and finish rolling in sequence and cooled to obtain a rare earth steel resistant to marine atmospheric corrosion 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 1053°C, and the cumulative reduction ratio of the rough rolling is 35%; wherein the starting rolling temperature of the finish rolling is 886°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 779°C to a final cooling temperature of 495°C at a rate of 15°C / s, and then air cool to room temperature.

[0074] The base material of the marine atmosphere corrosion resistant rare earth 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 marine atmosphere corrosion resistant rare earth steel obtained in Example 1 has ferrite, pearlite and granular bainite structures, which indicates that the marine atmosphere corrosion resistant rare earth steel obtained in Example 1 has excellent mechanical properties.

[0075] Embodiments 2 to 6

[0076] The difference between Examples 2 to 6 and Example 1 lies in the different weight percentages of the components in the marine atmosphere corrosion resistant rare earth steel and the different rolling and cooling parameters.

[0077] Comparative Examples 1-2

[0078] The difference between Comparative Examples 1 to 2 and Example 1 lies in the different weight percentages of the components in the marine atmosphere corrosion resistant rare earth steel and the different rolling and cooling parameters.

[0079] The compositions of the marine atmosphere corrosion resistant rare earth steels in Examples 1 to 6 and Comparative Examples 1 to 2 are shown in Table 1.

[0080] Table 1 Composition of rare earth steel resistant to marine atmospheric corrosion in Examples 1 to 6 and Comparative Examples 1 to 2 (%)

[0081]

[0082]

[0083] The rolling and cooling parameters of the marine atmosphere corrosion resistant rare earth steels in Examples 1 to 6 and Comparative Examples 1 to 2 are shown in Table 2.

[0084] Table 2 Rolling and cooling parameters of marine atmosphere corrosion resistant rare earth steel in Examples 1 to 6 and Comparative Examples 1 to 2

[0085]

[0086]

[0087] The mechanical properties of the marine atmosphere corrosion resistant rare earth steels in Examples 1 to 6 and Comparative Examples 1 to 2 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.

[0088] Table 3 Mechanical properties of marine atmosphere corrosion resistant rare earth steels in Examples 1 to 6 and Comparative Examples 1 to 2

[0089]

[0090] It can be seen from Table 3 that by controlling the composition of the marine atmosphere corrosion resistant rare earth steel, the low-temperature toughness of the marine atmosphere corrosion resistant rare earth steel can be improved and the mechanical properties of the steel material can be effectively improved.

[0091] 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 2, 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 rare earth steel weld resistant to marine atmospheric corrosion are shown in Table 4.

[0092] Table 4 Low temperature toughness of the weld heat affected zone of marine atmospheric corrosion resistant rare earth steel in Examples 1 to 6 and Comparative Examples 1 to 2

[0093]

[0094]

[0095] 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 rare earth steel provided in Examples 1 to 6 of the present invention under simulated typical heat input conditions is greater than 100 J, and can even reach 171 J, and the low-temperature toughness of the welding heat affected zone is good.

[0096] The Axiover-200MAT metallographic microscope was used to observe the welding heat affected zone of the marine atmosphere corrosion resistant rare earth steel obtained in Example 1, and the microstructure of the welding heat affected zone of the marine atmosphere corrosion resistant rare earth steel in Example 1 under the condition of welding heat input of 35 kJ / cm was obtained as follows: Figure 2 As shown. Figure 2It 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 rare earth steel resistant to marine atmospheric corrosion.

[0097] The Axiover-200MAT metallographic microscope was used to observe the welding heat affected zone of the marine atmosphere corrosion resistant rare earth steel obtained in Comparative Example 1, and the microstructure of the welding heat affected zone of the marine atmosphere corrosion resistant rare earth 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 atmosphere corrosion-resistant rare earth 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.

[0098] The marine atmospheric corrosion-resistant rare earth 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 China 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 Immersion 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 in Example 1 and Comparative Example 2 are shown in Table 5.

[0099] Table 5 Corrosion resistance of rare earth steel resistant to marine atmospheric corrosion and Q235 grade steel of Example 1 and Comparative Example 2

[0100]

[0101] It can be seen from Table 5 that the marine atmosphere corrosion resistant rare earth steel of Example 1 reduces Ni by 0.5%, Si by 0.4%, Mo by 0.3% and Cu by 0.5% relative to the marine atmosphere corrosion resistant rare earth steel of Comparative Example 2, thereby saving costs, but the corrosion resistance of the steel material has not decreased significantly; and the marine atmosphere corrosion resistant rare earth 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.

[0102] The corrosion weight loss of the marine atmosphere corrosion resistant rare earth steel of Example 1, the marine atmosphere corrosion resistant rare earth steel of Comparative Example 2 and Q235 steel is as follows: Figure 4 As shown in the figure, the corrosion weight loss of the marine atmosphere corrosion resistant rare earth steel of Example 1 after 360h is 122mg / cm 2 The corrosion weight loss of the marine atmosphere corrosion resistant rare earth steel of comparative example 2 after 360h is 99.2mg / cm 2 The corrosion weight loss of Q235 steel at 360h is 297mg / cm 2 .Depend on Figure 4 It can be seen that the corrosion resistance of the marine atmosphere corrosion resistant rare earth steel provided by the present invention is significantly better than that of Q235 steel.

[0103] The corrosion weight loss rates of the marine atmosphere corrosion resistant rare earth steel of Example 1, the marine atmosphere corrosion resistant rare earth steel of Comparative Example 2 and Q235 steel are as follows: Figure 5 As shown in Figure 1, the maximum corrosion weight loss rate of the marine atmosphere corrosion resistant rare earth steel of Example 1 is 0.62 mg / cm 2 *h, the maximum corrosion weight loss rate of the marine atmosphere corrosion resistant rare earth steel of comparative example 2 is 0.53 mg / cm 2 *h, the maximum corrosion weight loss rate of Q235 steel is 1.74 mg / cm 2 *h. Figure 5 It can be seen that the corrosion weight loss rate of the marine atmospheric corrosion resistant rare earth 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 rare earth steel of the present invention is significantly better than that of Q235 steel.

[0104] In summary, the marine atmosphere corrosion resistant rare earth steel provided by the present invention provides a weathering steel with good low-temperature toughness and excellent corrosion resistance, as well as excellent mechanical properties.

[0105] 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 rare earth steel, comprising, by weight percentage, C 0.03-0.08%, Si 0.05-0.19%, Mn 0.5-0.9%, Ni 1.00-1.19%, Cu 0.15-0.55%, Mo 0.21-0.40%, Nb 0.035-0.100%, V 0.02-0.04%, Ti 0.01-0.03%, Ce 0.003-0.008%, Als 0.02-0.05%, N 0.006-0.008%, P 0.001-0.015%, O≤0.004%, S≤0.005%, and the balance Fe; The content of each element in the marine atmosphere corrosion resistant rare earth steel meets the following conditions: The number and size of inclusions α50~110, the number and size of precipitates η4~6, and the marine atmospheric corrosion resistance index I≥1.2; The α=([Mn] / 55+[Ce] / 140+[Al] / 27) / ([S] / 32+[O] / 16); Said η=[V] / ([C]+[N])+[Ti] / [N]+[Nb] / ([C]+[N]); 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 rare earth steel according to claim 1, characterized in that: Calculated by weight percentage, it includes C 0.03-0.06%, Si 0.08-0.19%, Mn 0.6-0.9%, Ni 1.0-1.1%, Cu 0.20-0.55%, Mo 0.25-0.40%, Nb 0.05-0.10%, V 0.02-0.03%, Ti 0.015-0.030%, Ce 0.003-0.006%, Als 0.02-0.04%, N 0.0060-0.0075%, P 0.001-0.010%, O≤0.003%, S≤0.003%, and the balance Fe.

3. The marine atmosphere corrosion resistant rare earth steel according to claim 2, characterized in that: Calculated by weight percentage, it includes C 0.040-0.045%, Si 0.10-0.15%, Mn 0.75-0.90%, Ni 1.03-1.08%, Cu 0.30-0.45%, Mo 0.3-0.4%, Nb 0.050-0.085%, V 0.024-0.030%, Ti 0.020-0.025%, Ce 0.003-0.0045%, Als 0.02-0.03%, N 0.006-0.007%, 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 rare earth 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 rare earth steel resistant to marine atmosphere corrosion.

5. The preparation method according to claim 4, characterized in that: The smelting temperature in step (1) is 1550-1600° C., the smelting time is 60-90 min, and the smelting vacuum is 10-20 Pa.

6. 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 3-5 hours.

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

8. The preparation method according to claim 7, characterized in that: The starting rolling temperature of the rough rolling is 1100-1120° C., and the finishing rolling temperature is 1020-1080° C.; the cumulative reduction ratio of the rough rolling is above 35%.

9. The preparation method according to claim 7, 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%.

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

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