Duplex stainless steel and large-diameter duplex stainless steel liquid slip ring forge piece and preparation method thereof

Abstract

The application provides a kind of duplex stainless steel and large diameter duplex stainless steel liquid slip ring forge piece and its preparation method, relate to metal material technical field.Duplex stainless steel, component is according to mass percentage, including:C:0.01-0.03%, Si:0.30%~0.60%, Mn:1.0%~1.5%, Cr:22.0%~23.0%, Mo:2.5%~3.5%, Ni:4.5%~5.5%, N:0.08%~0.20%, P≤0.025%, S≤0.02%, the rest component is Fe and inevitable impurity.The duplex stainless steel provided by the application improves the strength, plasticity and corrosion resistance of the material, reduces the risk of harmful brittle phase precipitation, and the preparation method of the large diameter duplex stainless steel liquid slip ring forge piece provided by the application maximally suppresses the precipitation of brittle phase, prevents forging cracking, and obtains maximum impact performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal materials, and particularly relates to a duplex stainless steel and a large-diameter duplex stainless steel liquid sliding ring forge piece and a preparation method thereof. BACKGROUND

[0002] Compared with land oil and gas exploitation, the ocean current is violent, the sea temperature and pressure change greatly with depth, and the seabed rock structure is quite different from that of land wells.

[0003] The content of H2S, CO2 and Cl - , etc. in marine oil and gas is generally high, the types of seabed microorganisms are complex, and the chemical corrosion and microbial corrosion are very strong. Therefore, special steel materials such as stainless steel for marine oil and gas exploitation platforms generally require high corrosion resistance, high strength and high toughness, etc.

[0004] Large liquid sliding ring forgings are key components of single point mooring systems for marginal offshore oil fields, and the current liquid sliding ring forgings have a small diameter, basically below 1m, which cannot meet the needs of large single point mooring systems. In addition, in the preparation process of large-diameter forgings, the risk of cracking of the forgings is high, and the manufacturing difficulty is great. Therefore, it is urgent to develop a high-corrosion-resistant, high-strength and high-toughness large-diameter duplex stainless steel liquid sliding ring forging and a preparation method thereof. SUMMARY

[0005] In view of the above analysis, the present application aims to provide a duplex stainless steel and a large-diameter duplex stainless steel liquid sliding ring forging and a preparation method thereof, to solve at least one of the following technical problems: reducing the cracking risk of large ring forgings during manufacturing, and ensuring high corrosion resistance, high strength and high toughness of the forgings.

[0006] The purpose of the present application is mainly achieved by the following technical solutions:

[0007] On the one hand, the present application provides a duplex stainless steel, the components of the duplex stainless steel include, by mass percentage: C: 0.01-0.03%, Si: 0.30%-0.60%, Mn: 1.0%-1.5%, Cr: 22.0%-23.0%, Mo: 2.5%-3.5%, Ni: 4.5%-5.5%, N: 0.08%-0.20%, P≤0.025%, S≤0.02%, and the rest is Fe and inevitable impurities.

[0008] Preferably, the Ni equivalent / Cr equivalent is in the range of 0.35-0.45.

[0009] Preferably, the duplex stainless steel component comprises, in mass percentage: C: 0.01-0.03%, Si: 0.40%-0.50%, Mn: 1.0%-1.2%, Cr: 22.0%-22.5%, Mo: 2.8%-3.3%, Ni: 4.8%-5.3%, N: 0.10%-0.20%, P≤0.025%, S≤0.02%, and the rest is Fe and inevitable impurities.

[0010] In another aspect, the present application provides a preparation method of a large-diameter duplex stainless steel liquid slip ring forging, comprising:

[0011] Step 1: obtaining raw materials according to the alloy proportion, and performing secondary smelting on the raw materials to obtain an ingot;

[0012] Step 2: annealing the ingot obtained in step 1, and then performing processing skinning treatment, temperature rising and homogenizing treatment at high temperature to obtain a blank;

[0013] Step 3: performing a forging process of blooming and elongating on the blank obtained in step 2, and then dividing the blank into at least two rough forging pieces to obtain at least two forging blank pieces;

[0014] Step 4: performing forging forming on the at least two forging blank pieces obtained in step 3 to obtain at least two annular rough forging pieces;

[0015] Step 5: performing heat treatment on the at least two annular rough forging pieces obtained in step 4 at a temperature of 1000-1100℃ and maintaining for 10-15h, and then water cooling;

[0016] Step 6: performing rough machining and flaw detection on the at least two annular rough forging pieces obtained in step 5, and performing performance heat treatment after passing the inspection.

[0017] Preferably, step 1 comprises: S101: smelting and pouring the raw materials into electrode bars in a vacuum induction furnace, and the tapping temperature is 1500-1600℃; S102: performing electroslag remelting smelting on the electrode bars or remelting smelting on the electrode bars in a vacuum consumable manner.

[0018] Preferably, step 2 comprises: S201: annealing treatment: maintaining in a heat treatment furnace at 1000-1100℃ for 10-15h, and then furnace cooling to room temperature; S202: performing processing skinning treatment on the surface of the ingot; S203: temperature rising and homogenizing: rising the temperature of the ingot to 1000-1050℃ and maintaining for 10-15h for homogenizing; S204: high-temperature homogenizing treatment of the ingot at 1150-1300℃, and maintaining for 10-20h.

[0019] Preferably, the initial forging temperature in step 3 is 1150-1300°C, the final forging temperature is 950-1050°C, and the reduction rate is less than 0.01s each time. -1 .

[0020] Preferably, in step 4, the initial forging temperature is 1150-1300°C, the final forging temperature is 950-1050°C, and the reduction rate is less than 0.01s each time. -1 .

[0021] Preferably, in step 6, the heat treatment process is: heating to 1000-1100°C in a heat treatment furnace at a heating rate of ≤80°C / h, keeping the temperature for 10-15h, and then cooling with water to below 200°C.

[0022] On the other hand, the present invention provides a large diameter duplex stainless steel slip ring forging, the diameter of the slip ring forging is The above includes the above duplex stainless steel or is prepared by the above preparation method.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] A) The duplex stainless steel provided by the present invention, wherein Mo and Cr are ferrite-promoting elements, which will increase the strength of the material, and Ni, Mn, and N are austenite-stabilizing elements, which play a role in expanding the austenite region, which will improve the plasticity and corrosion resistance of the material. The elements and proportions of the duplex stainless steel provided by the present invention can maintain the high corrosion resistance, high strength and high toughness of the duplex stainless steel, while reducing the risk of precipitation of the harmful brittle phase σ, effectively preventing cracking in the subsequent forging process, and can produce a diameter of Large diameter duplex stainless steel slip ring forgings.

[0025] B) This invention applies a post-annealing peeling treatment to the steel ingot, effectively removing surface defects such as slag grooves and preventing forging cracking. This treatment is followed by a high-temperature homogenization treatment at 1150-1300°C for 10-20 hours. This reduces the degree of elemental segregation within the electroslag ingot, eliminates harmful phases in the casting structure, and improves the overall structural uniformity of the electroslag ingot. Specifically, during the heating process, the ingot is held at 1000-1050°C for 5 hours to achieve uniform temperature and prevent thermal cracking caused by excessive internal and external temperature differences.

[0026] C) The electroslag ingot is blanked and drawn as a whole, and then divided into at least two forging blanks. One electroslag ingot can produce at least two finished products, and the total forging ratio can be greater than 6 to ensure the final performance; the initial forging temperature is 1150~1300℃, the final forging temperature is 950~1050℃, and the reduction rate is less than 0.01s each time. -1 ;Thereby avoiding forging cracking to the greatest extent.

[0027] D) the annular forging is annealed after forging, in particular, the annealing needs to be heat treated in a 1000-1100 DEG C heat treatment furnace for 10-15 hours and then water cooled, the temperature range can effectively eliminate the forging stress, and can play the role of dehydrogenation heat treatment, and can ensure that the volume ratio of ferrite and austenite is 1:1. Subsequently, the cooling method of water cooling is also used to avoid the precipitation of brittle phases such as sigma, and prevent cracking in the subsequent processing process; after annealing, continue to perform performance heat treatment, at a heating rate of ≤80 DEG C / h, to 1000-1100 DEG C heat treatment furnace for 10-15h and then water cooled to below 200 DEG C. The above two solid solution treatments can fully and uniformly organize and improve the tensile strength of the duplex stainless steel. The cooling method of water cooling can maximize the inhibition of the precipitation of brittle phases, and obtain the maximum impact performance.

[0028] In the present application, the above technical solutions can be combined with each other to realize more preferred combination solutions. Other features and advantages of the present application will be described in the subsequent specification, and some advantages will become apparent from the specification, or will be understood by implementing the present application. The purposes and other advantages of the present application can be realized and obtained from the contents specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application.

[0030] Figure 1 A schematic diagram of the liquid sliding ring forging provided by the present application is shown in the figure;

[0031] Figure 2 A performance heat treatment process diagram in step 6 provided by the present application is shown in the figure;

[0032] Figure 3 A liquid sliding ring forging microstructure morphology diagram in example 1 provided by the present application is shown in the figure;

[0033] Figure 4 An annealed microstructure morphology diagram in comparative example 5 provided by the present application is shown in the figure;

[0034] Figure 5 A performance heat treatment microstructure morphology diagram in comparative example 6 provided by the present application is shown in the figure. DETAILED DESCRIPTION

[0035] The preferred embodiments of the present application will be specifically described below in combination with the drawings, wherein the drawings constitute a part of this application, and together with the embodiments of the present application serve to explain the principles of the present application, and are not used to limit the scope of the present application.

[0036] The application provides a duplex stainless steel, which comprises the following components in percentage by mass: C: 0.01-0.03%, Si: 0.30%-0.60%, Mn: 1.0%-1.5%, Cr: 22.0%-23.0%, Mo: 2.5%-3.5%, Ni: 4.5%-5.5%, N: 0.08%-0.20%, P≤0.025%, S≤0.02%, and the rest is Fe and inevitable impurities, wherein the Ni equivalent / Cr equivalent is in the range of 0.35-0.45, so as to ensure the requirements of the structure and performance.

[0037] The following specifically describes the effects and dosage selection of the components contained in the application:

[0038] The element C is not conducive to the pitting resistance and weldability of the stainless steel. Therefore, in order to ensure that the duplex stainless steel of the application has good strength and toughness matching, the content of the element C in the application is controlled to be 0.01%-0.03%.

[0039] The element Si has a great influence on the content of austenite and ferrite phases and the precipitation temperature of harmful phases, and can play a good solid solution strengthening effect in the steel. If the content of the element Si is too high, the toughness and plasticity will be reduced, and if the content of the element Si is too low, it is not conducive to ensuring good comprehensive mechanical properties. Therefore, the content of the element Si in the application is controlled to be 0.30%-0.60%.

[0040] The element Mn is an austenite stabilizing element, cooperates with Ni and N to expand the austenite region, and appropriately increasing the content of the element Mn can replace part of the element Ni to reduce the cost, but too high content of the element Mn will increase the risk of cavitation corrosion. In the application, the content of the element Mn is in the range of 1.0%-1.5%.

[0041] The element Cr is a ferrite promoting element, promotes the precipitation of the sigma phase, and increasing the content of the element Cr will increase the precipitation temperature of the harmful sigma phase. The higher the precipitation temperature of the harmful sigma phase is, the narrower the forging temperature range is, and the higher the cracking risk is. Too low content of the element Cr will reduce the corrosion resistance and affect the duplex phase ratio. In the application, the content of the element Cr is in the range of 22.0%-23.0%.

[0042] The element Mo is a ferrite promoting element, promotes the precipitation of the sigma phase, and increasing the content of the element Mo will increase the precipitation temperature of the harmful sigma phase. The higher the precipitation temperature of the harmful sigma phase is, the narrower the forging temperature range is, and the higher the cracking risk is. Too low content of the element Mo will reduce the corrosion resistance and affect the duplex phase ratio. In the application, the content of the element Mo is in the range of 2.5%-3.5%, and the content of the elements Cr and Mn is appropriately increased, so as to increase the ferrite ratio and machining performance.

[0043] Ni element is an austenite stabilizing element, which plays a role in expanding the austenite region, and too high will increase the austenite proportion, too low will reduce the austenite proportion, according to the simulation calculation result, Ni increases by 1%, the austenite content in the microstructure after heat treatment increases by 10%, the Ni content in the application is 4.5%~5.5%.

[0044] N element is an austenite stabilizing element, which plays a role in expanding the austenite region, and too high will increase the austenite proportion, too low will reduce the austenite proportion, according to the simulation calculation result, N increases by 0.1%, the austenite content increases by 13%, the N content in the application is 0.08%~0.20%.

[0045] P element is a harmful element, the P content in the application is controlled to be ≤0.025 %.

[0046] S element is a harmful element, the S content in the application is controlled to be ≤0.02 %.

[0047] Specifically, the calculation formula of Ni equivalent and Cr equivalent is:

[0048] Ni equivalent = [Ni] + 30[C+N] + 0.5[Mn],

[0049] Cr equivalent = [Cr] + 1.5[Mo] + 1.5[Si],

[0050] Wherein, [Ni] is the mass percentage content of Ni element, [C+N] is the sum of mass percentage content of C element and N element, [Mn] is the mass percentage content of Mn element, [Cr] is the mass percentage content of Cr element, [Mo] is the mass percentage content of Mo element, [Si] is the mass percentage content of Si element.

[0051] It should be noted that too high Ni equivalent / Cr equivalent will result in too high austenite phase content, and too low will result in too high ferrite phase content, and the Ni equivalent / Cr equivalent is in the range of 0.35-0.45.

[0052] Specifically, the Ni equivalent / Cr equivalent is in the range of 0.35-0.45, so that the volume ratio of ferrite and austenite is 1:1, and this ratio can maintain the high corrosion resistance, high strength and high toughness performance of duplex stainless steel. If the ferrite content is relatively high, the strength will be improved, but the toughness and corrosion resistance are poor, and if the austenite content is relatively high, the toughness and corrosion resistance are improved, but the strength is poor.

[0053] It should be noted that the duplex stainless steel provided by the present application adopts the above-mentioned element composition with the above-mentioned proportion, wherein Mo and Cr are ferrite promoting elements, which can improve the strength of the material, Ni, Mn and N are austenite stabilizing elements, which play a role in expanding the austenite region, and can improve the plasticity and corrosion resistance of the material. In addition, Mo and Cr elements promote the precipitation of harmful sigma phase, and Mo element has a more significant effect on the precipitation of the harmful sigma phase. The precipitation of brittle phases such as sigma will cause cracking during processing. Therefore, the Mo content is appropriately controlled, and the Cr and Mn contents are appropriately increased to improve the ferrite proportion and machining performance. The present application controls the precipitation temperature of the harmful sigma phase below 950 DEG C through the above-mentioned elements and proportions.

[0054] Preferably, in order to further improve the comprehensive performance of the duplex stainless steel, the above-mentioned duplex stainless steel component comprises, in mass percentage: C: 0.01-0.03%, Si: 0.40%-0.50%, Mn: 1.0%-1.2%, Cr: 22.0%-22.5%, Mo: 2.8%-3.3%, Ni: 4.8%-5.3%, N: 0.10%-0.20%, P≤0.025%, S≤0.02%. The rest is Fe and inevitable impurities, wherein the Ni equivalent / Cr equivalent is in the range of 0.35-0.45.

[0055] The present application also provides a large-diameter duplex stainless steel liquid slip ring forging. For example, 3.25m, 3.3m, 3.5m, etc. can comprise the above-mentioned duplex stainless steel.

[0056] The present application also provides a large-diameter duplex stainless steel liquid slip ring forging preparation method, comprising:

[0057] Step 1: obtain raw materials according to the alloy proportion, and perform secondary melting on the raw materials to obtain an ingot;

[0058] Step 2: annealing treatment is performed on the ingot obtained in step 1, and then processing, peeling, temperature rising, temperature equalization and high-temperature homogenization treatment are performed to obtain a blank;

[0059] Step 3: the blank obtained in step 2 is subjected to a forging process of cogging, elongating and then dividing into at least two rough forging pieces to obtain at least two forging blank pieces;

[0060] Step 4: the at least two forging blank pieces obtained in step 3 are subjected to forging forming to obtain at least two annular rough forging pieces;

[0061] Step 5: the at least two annular rough forging pieces obtained in step 4 are subjected to heat treatment at a temperature of 1000-1100 DEG C and then water-cooled after holding for 10-15h;

[0062] Step 6: rough machining and flaw detection are performed on the at least two ring-shaped blank forgings obtained in step 5, and after passing the inspection, performance heat treatment is performed;

[0063] Step 7: machining, flaw detection and performance testing are performed on the at least two ring-shaped blank forgings obtained in step 6.

[0064] It should be noted that the large-diameter duplex stainless steel liquid slip ring forging preparation method provided by the present application can effectively prevent forging cracking, one electroslag ingot can produce at least two finished products, the total forging ratio can be greater than 6, the final performance is guaranteed, the forging stress can be effectively eliminated, harmful phases such as sigma cannot be generated, the volume ratio of ferrite and austenite can be guaranteed to be 1:1, the structure can be fully and uniformly distributed, the tensile strength of duplex stainless steel can be improved, the precipitation of brittle phases can be maximally inhibited, and the maximum impact performance can be obtained.

[0065] For step 1:

[0066] Specifically, in step 1, the first melting in the secondary melting can be melted in a vacuum induction furnace, and the second melting can be electroslag remelting smelting or vacuum consumable remelting smelting. Specifically, step 1 can include:

[0067] S101: melt and cast the raw materials into electrode bars in a vacuum induction furnace, and the tapping temperature is 1500-1600 DEG C.

[0068] S102: electroslag remelting smelting or vacuum consumable remelting smelting is performed on the electrode bars to obtain a more pure steel ingot, and the total weight of the steel ingot is more than 70 tons.

[0069] It should be noted that the tapping temperature of the vacuum induction furnace in step S101 is 1500-1600 DEG C. If the temperature is too high or too low, the melting degree of the molten steel and the pouring effect cannot be guaranteed.

[0070] Specifically, when step S102 adopts electroslag remelting smelting, the melting speed is required to be 1-2 t / h, and the total smelting time is 60-70 h.

[0071] It should be noted that when the secondary melting in step 1 adopts vacuum induction furnace melting and electroslag remelting smelting respectively, the electrode bar is first melted and cast by using the vacuum induction furnace, and then the electrode bar is re-melted and solidified by using the electroslag remelting. The steel ingot has very good inclusion and segregation control. The electroslag remelting re-melts the smelted electrode bar, collects the molten metal into droplets, and drops through the slag layer into the metal pool. Then, the molten metal is crystallized and solidified into a steel ingot in a water-cooled crystallizer. Since the pool becomes shallower, the crystallization tends to be axial, and the solidification segregation problem is improved, and the internal quality of the ingot is improved.

[0072] Specifically, when the electrode rod is remelted by the vacuum consumable method in step S102, the melting speed is 0-100 mm / min. If the melting speed is too high, the molten pool is too deep, and macrosegregation is high. If the melting speed is too low, the molten pool is too shallow, and the feeding is insufficient, and defects such as a loose core are prone to occur.

[0073] It should be noted that when the secondary melting is performed by the vacuum induction furnace melting and the vacuum consumable remelting, the electrode rod is first melted by the vacuum induction furnace melting and then remelted by the vacuum consumable method, so that the gas and other impurities in the raw material are removed, and a uniform and dense ingot with higher purity is formed. The vacuum consumable arc melting is to make the raw material to be melted into a standard columnar consumable electrode. In a vacuum environment, the electric arc generated between the consumable electrode and the base material converts electric energy into heat energy in the arc light. The metal is heated and melted by the direct action of radiation and electric arc, and then cooled and crystallized in the crucible. The material is subjected to ultra-high temperature of the electric arc in the vacuum, the gas and other impurities in the raw material are removed, and a uniform and dense ingot with higher purity is formed, which meets the requirements of further processing.

[0074] It should be noted that the large-diameter duplex stainless steel liquid slip ring forging provided by the present application has a high product weight, so the ingot is large, and it is a large forging. Therefore, the total weight of the steel ingot in step 1 is more than 70 tons.

[0075] For step 2:

[0076] Specifically, step 2 can include:

[0077] S201: annealing treatment: heat preservation for 10-15h in a 1000-1100℃ heat treatment furnace, and then furnace cooling to room temperature;

[0078] S202: processing and skinning treatment on the surface of the steel ingot to remove surface defects such as slag grooves;

[0079] S203: temperature rising and temperature equalization: the steel ingot is heated to 1000-1050℃ and temperature equalized for 5-10h;

[0080] S204: the steel ingot is heated to 1150-1300℃ for homogenization treatment, and temperature equalized for 10-20h;

[0081] S205: furnace discharge and forging to obtain a blank.

[0082] It should be noted that the step 2 is to perform skinning treatment after annealing the ingot, which can effectively remove surface slag groove and other defects, and effectively prevent forging cracking. Then, high temperature homogenization treatment is performed at 1150-1300°C for 10-20h, so as to reduce the segregation degree of each element in the electroslag ingot, eliminate harmful phases in the casting structure, and improve the overall uniformity of the electroslag ingot. In particular, during the heating process, the temperature is kept at 1000-1050°C for 5-10h for temperature equalization, so as to prevent thermal cracking caused by too large temperature difference between the inside and the outside.

[0083] Specifically, in step S201, the annealing treatment is kept in a heat treatment furnace at 1000-1100°C for 10-15h, which can effectively eliminate forging stress, and can play the role of dehydrogenation heat treatment, without generating harmful phases such as sigma, and can ensure that the proportion of ferrite and austenite is 1:1. If the temperature is too high, the content of ferrite phase is too high, and the cost is increased. If the temperature is too low, it is insufficient to eliminate harmful phases generated in the forging process and adjust the morphology of the two-phase structure. Therefore, the holding temperature is controlled at 1000-1100°C. If the holding time is too short, it is insufficient for heat penetration and two-phase transformation, and if the holding time is too long, it is a waste of resources. Therefore, the holding time is controlled at 10-15h.

[0084] Specifically, in step S202, the skinning treatment ensures that the surface of the ingot is free of defects such as subcutaneous bubbles, surface cracks, surface inclusions, skin peeling, pitting, folding, scarring, slag groove, flow steel, porosity, etc. to effectively prevent forging cracking.

[0085] Specifically, in step S203, the temperature equalization function is to prevent thermal cracking caused by too large temperature difference between the inside and the outside. The temperature is selected to be higher than the temperature range in which harmful phases are precipitated. If the temperature is too high, the temperature difference is large and thermal cracking is easy to occur. If the temperature is too low, harmful phases are precipitated. Therefore, the temperature is controlled at 1000-1050°C. If the holding time is too long, it is a waste of resources and increases the cost. If the holding time is too short, it is insufficient for heat penetration. Therefore, the holding time is controlled at 5-10h.

[0086] Specifically, in step S204, the high temperature homogenization treatment is used to reduce the segregation degree of each element in the electroslag ingot, eliminate harmful phases in the casting structure, and improve the overall uniformity of the electroslag ingot. If the temperature is too high, there is a risk of overburning and overheating. If the temperature is too low, the forging temperature range is too narrow, which is not conducive to subsequent forging. Therefore, the temperature is controlled at 1150-1300°C. If the holding time is too long, too much is burned. If the holding time is too short, it cannot guarantee heat penetration and eliminate casting defects such as segregation. Therefore, the holding time is controlled at 10-20h.

[0087] For step 3:

[0088] As shown in Figure 1 , one ingot produces at least two ring-shaped forgings.

[0089] Specifically, in step 3, the steel ingot breakdown and the forging of the forging piece are both performed on a 10000-ton water press, the initial forging temperature is 1150-1300℃, the final forging temperature is 950-1050℃, and the rate of each pressing is less than 0.01S -1 If cracking occurs, heat the wound at a temperature above 900℃ in time, and then return to the furnace to be uniform.

[0090] It should be noted that in step 3, the electroslag ingot is subjected to overall breakdown and elongation, and then divided into at least two forging blanks, and at least two finished products are obtained from one electroslag ingot, so that the total forging ratio is greater than 6, and the final performance is ensured; the initial forging temperature is 1100-1300℃, the final forging temperature is 950-1050℃, and the rate of each pressing is less than 0.01S -1 , so as to avoid forging cracking to the greatest extent. It should be noted that the total forging ratio has an effect on the elimination of as-cast defects, the uniformity of the structure, the grain size, and the proportion of phases, and a large forging ratio is beneficial to the performance.

[0091] Specifically, in step 3, the initial forging temperature is too high, which has the risk of overburning and overheating, and the forging temperature range is too narrow if the forging temperature is too low, which is not conducive to subsequent forging, so the initial forging temperature is controlled to be 1150-1300℃.

[0092] Specifically, in step 3, the final forging temperature is too high, the temperature range is too narrow, the number of heating times is increased, the cost and the construction period are increased, and cracking occurs if the temperature is too low, so the final forging temperature is controlled to be 950-1050℃.

[0093] Specifically, in step 3, the rate of pressing is too high, which may cause cracking, so the rate of each pressing is controlled to be less than 0.01S -1 , for example, 0.001S -1 , 0.005S -1 .

[0094] Specifically, in step 3, the heat wound temperature is too high, which is difficult to operate on site, and harmful phases are precipitated and cracks are expanded if the temperature is too low. Therefore, if cracking occurs, the wound must be heated above 900℃ in time, and then returned to the furnace to be uniform, for example, 950℃, 1000℃.

[0095] In addition, it should be noted that the forging cracking of the dual-phase steel is greatly affected by the matching of the two phases. At high temperatures, the thermal deformation behavior of the entire material is not uniform due to the different flow stress levels of the two phases. Due to the complexity of the as-cast structure, the deformation is concentrated in certain local areas. At the initial stage of deformation, when the strain is low, the softer ferrite phase bears most of the strain, and at this time the strengthening of the material is controlled by the recovery of the ferrite. As the strain increases, the stress gradually transfers to the harder austenite phase, and when the strain reaches the driving force for recrystallization of the austenite, recrystallization occurs, causing the austenite bundles to soften and elongate and narrow. However, during the process of stress transfer to the austenite phase, in order to maintain the coordination of the interface deformation, the interface slips and the ferrite shears. When the deformation is too large and the two-phase interface cannot be coordinated, cracks will be initiated and expanded. The softening mechanism of the dual-phase stainless steel is mainly related to the deformation rate. The slower the deformation rate, the more sufficient the dynamic recovery and dynamic recrystallization of the austenite and ferrite in the stainless steel, the smaller the peak stress, and the more significant the softening effect. Therefore, the rate of each pressing is required to be less than 0.01 s -1 In addition, the presence of harmful phases during deformation will greatly reduce the plasticity of the steel and cause cracking. Therefore, the initial forging temperature and the final forging temperature in step 3 should be higher than the temperature range in which harmful phases are precipitated.

[0096] For step 4:

[0097] Specifically, step 4 deforms and shapes at least two pieces of the forged blank obtained in step 3 by methods such as upsetting, piercing, mandrel pre-holing, and hole expansion, and each forging process is performed on a water press of more than 10,000 tons. The initial forging temperature is 1150-1300°C, the final forging temperature is 950-1050°C, and the rate of each pressing is less than 0.01 s -1 ,

[0098] Alternatively,

[0099] Step 4 deforms and shapes at least two pieces of the forged blank obtained in step 3 by methods such as upsetting and piercing; each forging process is performed on a water press of more than 10,000 tons. The initial forging temperature is 1150-1300°C, the final forging temperature is 950-1050°C, and the rate of each pressing is less than 0.01 s -1 ; and the at least two rough blank forgings are ring-rolled on a 8,000-ton ring mill to obtain ring-shaped forged blank pieces.

[0100] It should be noted that in step 4, the initial forging temperature is too high, which poses the risk of overburning and overheating, and the forging temperature range is too narrow if it is too low, which is not conducive to subsequent forging. Therefore, the initial forging temperature is controlled to be 1150-1300°C.

[0101] It should be noted that in step 4, the final forging temperature is too high, the temperature range is too narrow, the number of heating times is increased, the cost and construction period are increased, and cracking occurs, therefore, the final forging temperature is controlled to be 950-1050℃.

[0102] Specifically, in step 4, if the pressing rate is too high, cracking occurs, therefore, the pressing rate is controlled to be less than 0.01S -1 , 0.001 S -1 , 0.005S -1 .

[0103] For step 5:

[0104] Step 5 is annealing after forging of the ring-shaped forging, specifically, the annealing needs to be heat treated in a heat treatment furnace at 1000-1100℃ for 10-15h and then water cooled, this temperature range can effectively eliminate the forging stress, and can play the role of dehydrogenation heat treatment, at the same time, σ and other harmful phases are not generated, and the volume ratio of ferrite and austenite two phases is ensured to be 1:1.

[0105] Specifically, in step 5, if the temperature in the heat treatment furnace is too high, the ferrite content is too high, if it is too low, it is insufficient to eliminate the harmful phase morphology generated by forging, and the structure is balanced, therefore, the temperature is controlled to be 1000-1100℃.

[0106] Specifically, in step 5, if the heat preservation time is too long, energy is wasted, the cost is increased, if it is too short, it is insufficient to heat and balance the structure, therefore, the heat preservation time is controlled to be 10-15h.

[0107] It should be noted that the water cooling treatment of step 5: avoids the precipitation of σ and other brittle phases, and prevents cracking in the subsequent processing process. With the decrease of temperature, ferrite is transformed into austenite, the solubility of Cr, Mo elements in austenite phase is less than that in ferrite, therefore, Fe, Cr, Mo elements mainly intermetallic compounds are precipitated at the boundary of the two phases, such intermetallic compounds have extremely poor toughness, significantly deteriorate the plasticity and toughness of the material, and cause forging cracking. If the corresponding temperature range is quickly passed, the formation of such brittle phases can be effectively avoided, therefore, water cooling treatment is recommended.

[0108] For step 6:

[0109] Specifically, as shown in Figure 2 , the heat treatment process of step 6 is: with a heating rate of ≤80℃ / h, the temperature is raised to 1000-1100℃ in a heat treatment furnace, heat preservation is carried out for 10-15h, and then water cooling is carried out to below 200℃. As an optimization, the heat treatment process can also include a uniform temperature process before heating, specifically, it can be uniformed at 80-150℃ for 5 hours.

[0110] It should be noted that the heating rate of step 6 is ≤80℃ / h, for example 50, 80℃ / h, and the temperature difference between the inside and outside of the large forging is too large, and the thermal stress is too large, which causes thermal cracking.

[0111] It should be noted that the ferrite content is too high when the temperature of step 6 is too high, and the temperature is too low to eliminate the harmful phase morphology generated by forging, and the balanced structure, so the temperature is raised to 1000-1100℃.

[0112] It should be noted that the holding time of step 6 is too long, which wastes energy and increases cost, and is too short to heat and balance the structure, so the holding time in the heat treatment furnace is 10-15.

[0113] It should be noted that the water cooling temperature of step 6 is below 200℃, for example 150, 200℃, and the temperature is too high to ensure that the core surface avoids the harmful phase precipitation temperature range, and the temperature is too low to cause stress cracking.

[0114] It should be noted that step S5 is annealing after forging of the annular forging, and then the water cooling cooling method is used; after annealing, step S6 continues to perform performance heat treatment, and the water cooling cooling method is used to cool to below 200℃. The two solid solution treatments of step S5 and step S6 can fully and uniformly organize and improve the tensile strength of the duplex stainless steel. The water cooling cooling method can maximize the inhibition of the precipitation of brittle phases and obtain the maximum impact performance.

[0115] It should be noted that the room temperature yield strength of the duplex stainless steel liquid slip ring prepared by the above method is greater than 480MPa, the tensile strength is greater than 680MPa, the elongation is greater than 40%, the reduction of area is greater than 70%, and the impact energy is greater than 70J.

[0116] The preferred embodiments of the present application will be described in detail below to illustrate the principles of the present application, and are not intended to limit the scope of the present application.

[0117] Example 1

[0118] The present embodiment provides a duplex stainless steel and a large-diameter duplex stainless steel liquid slip ring forging, and a preparation method thereof. The diameter of the large-diameter duplex stainless steel liquid slip ring forging is 3.25m.

[0119] The duplex stainless steel includes, by mass percentage: C: 0.02%, Si: 0.45%, Mn: 1.2%, Cr: 22.5%, Mo: 3%, Ni: 5%, N: 0.15%, P: 0.020%, S: 0.015%, and the remaining components are Fe and unavoidable impurities, wherein the Ni equivalent / Cr equivalent is 0.39.

[0120] A preparation method of a large-diameter duplex stainless steel liquid slip ring forging, comprising:

[0121] Step 1: Obtain raw materials according to the alloy proportion, and perform secondary melting on the raw materials to obtain an ingot;

[0122] Specifically, step 1 includes:

[0123] S101: Obtain raw materials according to the alloy component proportion, and melt and cast the raw materials into electrode bars in a vacuum induction furnace;

[0124] S102: Perform electroslag remelting smelting on the electrode bars to obtain a more pure ingot with a total weight of more than 70 tons.

[0125] Step 2: Perform annealing treatment on the ingot obtained in step 1, and then perform skinning treatment, temperature rising and homogenization treatment at high temperature;

[0126] Specifically, step 2 includes:

[0127] S201: Annealing treatment, heat preservation in a 1030℃ heat treatment furnace for 10h, and furnace cooling to room temperature;

[0128] S202: Perform skinning treatment on the surface of the ingot to remove surface defects such as slag grooves;

[0129] S203: Temperature rising and homogenization: heat the ingot to 1050℃, and homogenize for 8h;

[0130] S204: Homogenization treatment at high temperature of 1200℃ for the ingot, and heat preservation for 12h;

[0131] S205: Furnace discharge and forging to obtain a billet.

[0132] Step 3: Perform the forging process of opening and elongating the billet obtained in step 2, and then dividing it into two rough forging pieces. The ingot opening and forging of the forging piece are both performed on a 10000-ton water press. The initial forging temperature is 1200℃, the final forging temperature is 1000℃, and the pressing rate is 0.005S -1 per time. If cracking occurs, heat cleaning must be performed at 1000℃ in time, and then the billet is homogenized.

[0133] Step 4: Form the two forging pieces obtained in step 3 into two ring-shaped rough forging pieces. The deformation modes such as upsetting, punching, mandrel pre-hole expanding, and hole expanding are used for the forging forming. The initial forging temperature is 1200℃, the final forging temperature is 1000℃, and the pressing rate is less than 0.01S -1 per time.

[0134] Step 5: Directly place the two ring-shaped rough forging pieces obtained in step 4 into a 1000℃ heat treatment furnace for heat preservation for 10h, and then water cooling.

[0135] Step 6: rough machining and flaw detection are performed on the two ring-shaped blank forgings obtained in step 5, and after passing the detection, performance heat treatment is performed; wherein, the heat treatment process is: the temperature is raised to 1050℃ at a temperature rising rate of 50℃ / h, and after holding in the heat treatment furnace for 10h, water cooling is performed to 200℃, and the heat treatment process is completed.

[0136] Step 7: machining, flaw detection and performance testing are performed on the two ring-shaped blank forgings obtained in step 6.

[0137] By Figure 3 It can be seen that the microstructure of the ring-shaped forgings prepared in the embodiment is uniform, and the volume ratio of ferrite and austenite is 1:1.

[0138] Example 2

[0139] The embodiment provides a dual-phase stainless steel and a large-diameter dual-phase stainless steel liquid sliding ring forging and a preparation method thereof, and the diameter of the large-diameter dual-phase stainless steel liquid sliding ring forging is 3.5m.

[0140] The dual-phase stainless steel includes, in terms of mass percentage, C: 0.01%, Si: 0.40%, Mn: 1.4%, Cr: 22.3%, Mo: 2.8%, Ni: 5.5%, N: 0.18%, P: 0.015%, S: 0.01%, and the remaining components are Fe and inevitable impurities. Among them, the Ni equivalent / Cr equivalent is 0.44.

[0141] A preparation method of a large-diameter dual-phase stainless steel liquid sliding ring forging, comprising:

[0142] Step 1: obtaining raw materials according to the alloy proportion, and performing secondary smelting on the raw materials to obtain a steel ingot;

[0143] Specifically, step 1 includes:

[0144] S101: obtaining raw materials according to the alloy component proportion, and smelting and pouring the raw materials into electrode bars in a vacuum induction furnace;

[0145] S102: performing electroslag remelting smelting on the electrode bars to obtain a more pure steel ingot with a total weight of 75 tons.

[0146] Step 2: annealing the steel ingot obtained in step 1, and then performing skinning treatment, temperature rising and homogenizing treatment at high temperature;

[0147] Specifically, step 2 includes:

[0148] S201: annealing treatment, holding in a 1050℃ heat treatment furnace for 13h and furnace cooling to room temperature;

[0149] S202: The surface of the ingot is processed by skinning treatment to remove surface defects such as slag grooves;

[0150] S203: Temperature rising and homogenizing: the ingot is heated to 1050℃ and kept for 10h for homogenizing;

[0151] S204: The ingot is heated to 1230℃ for high temperature homogenizing treatment and kept for 15h;

[0152] S205: The ingot is forged out of the furnace to obtain a blank.

[0153] Step 3: The blank obtained in step 2 is subjected to a forging process of opening and elongating and then divided into two pieces of forged blank. The ingot opening and the forging of the forged piece are both carried out on a 15000-ton hydraulic press. The initial forging temperature is 1230℃, the final forging temperature is 1050℃, and the pressing rate is 0.001S -1 ; if cracking occurs, the hot wound cleaning must be carried out at 1000℃ in time, and then the ingot is homogenized.

[0154] Step 4: The two pieces of forged blank obtained in step 3 are subjected to a forging process to obtain two pieces of ring-shaped blank forgings. The upsetting and piercing deformation methods are used for the forging process. The forging process is carried out on a 15000-ton hydraulic press. The initial forging temperature is 1230℃, the final forging temperature is 1050℃, and the pressing rate is 0.005S -1 ; then the two pieces of blank forgings are subjected to ring rolling on an 8000-ton ring rolling machine to obtain ring-shaped forged blank pieces;

[0155] Step 5: The two pieces of ring-shaped blank forgings obtained in step 4 are directly placed in a 1070℃ heat treatment furnace for 13h and then water-cooled.

[0156] Step 6: The two pieces of ring-shaped blank forgings obtained in step 5 are subjected to rough machining and flaw detection, and then subjected to performance heat treatment after passing the test. Specifically, the heat treatment process is as follows: the temperature is raised to 1070℃ at a rate of 80℃ / h, kept in the heat treatment furnace for 13h, and then water-cooled to 150℃ to complete the heat treatment process.

[0157] Step 7: The two pieces of ring-shaped blank forgings obtained in step 6 are subjected to machining, flaw detection and performance testing.

[0158] Example 3

[0159] The present embodiment provides a duplex stainless steel and a large-diameter duplex stainless steel liquid sliding ring forging and a preparation method thereof. The diameter of the large-diameter duplex stainless steel liquid sliding ring forging is 3.3m.

[0160] Duplex stainless steel, including the following components in percentage by mass: C: 0.03%, Si: 0.6%, Mn: 1.2%, Cr: 22.8%, Mo: 3.5%, Ni: 4.5%, N: 0.15%, P: 0.015%, S: 0.02%, the rest components are Fe and inevitable impurities, wherein, the Ni equivalent / Cr equivalent is 0.37.

[0161] A preparation method of a large-diameter duplex stainless steel liquid slip ring forging, comprising:

[0162] Step 1: obtaining raw materials according to the above alloy proportion, and carrying out secondary melting on the raw materials to obtain a steel ingot;

[0163] Specifically, step 1 comprises:

[0164] S101: obtaining raw materials according to the alloy component proportion, and melting and casting the raw materials into electrode bars in a vacuum induction furnace;

[0165] S102: remelting the electrode bars in a vacuum consumable manner to obtain a more pure steel ingot with a total weight of more than 70 tons.

[0166] Step 2: annealing the steel ingot obtained in step 1, and then carrying out skinning treatment, temperature rising and homogenization treatment at high temperature;

[0167] Specifically, step 2 comprises:

[0168] S201: annealing treatment, holding at 1080℃ in a heat treatment furnace for 15h and then furnace cooling to room temperature;

[0169] S202: skinning treatment on the surface of the steel ingot to remove surface defects such as slag grooves;

[0170] S203: temperature rising and homogenization, rising the steel ingot to 1000℃ and holding for 5h for homogenization;

[0171] S204: high temperature homogenization treatment of the steel ingot at 1300℃, holding for 20h;

[0172] S205: furnace discharge and forging to obtain a blank.

[0173] Step 3: carrying out the forging process of opening and elongating the blank obtained in step 2 and then dividing it into two rough forging pieces. The steel ingot opening and the forging of the forging piece are both carried out on a water press with a capacity of more than 10000 tons. The initial forging temperature is 1300℃, the final forging temperature is 950℃, and the pressing rate is 0.005S -1 ; if cracking occurs, the hot wound treatment at 950℃ must be carried out in time and then the steel ingot is homogenized.

[0174] Step 4: the two pieces of forging blanks obtained in step 3 are subjected to forging forming to obtain two pieces of annular rough forging blanks, wherein upsetting, punching, mandrel pre-boring, and boring are adopted for forging forming; wherein each forging process is carried out on a water press with a capacity of more than 10,000 tons; wherein the initial forging temperature is 1,300 DEG C, and the final forging temperature is 950 DEG C; the pressing rate is less than 0.01 s -1 .

[0175] Step 5: the two pieces of annular rough forging blanks obtained in step 4 are directly placed in a heat treatment furnace at 1,050 DEG C for 15 h and then water-cooled.

[0176] Step 6: the two pieces of annular rough forging blanks obtained in step 5 are subjected to rough machining and flaw detection, and then subjected to performance heat treatment after passing the test; wherein the heat treatment process is as follows: the temperature is raised to 1,000 DEG C at a temperature rising rate of 80 DEG C / h, and then the temperature is kept for 15 h in the heat treatment furnace and then water-cooled to below 150 DEG C, to complete the heat treatment process.

[0177] Step 7: the two pieces of annular rough forging blanks obtained in step 6 are subjected to machining, flaw detection, and performance test.

[0178] Comparative Example 1

[0179] The present comparative example provides a kind of duplex stainless steel and large diameter duplex stainless steel liquid slip ring forging and its preparation method, which are basically same with example 1, and different from example 1 in that the composition of duplex stainless steel includes: C:0.02%, Si:0.56%, Mn:1.2%, Cr:22.2%, Mo:3%, Ni:4.8%, N:0.29%, P:0.022%, S:0.009%, the rest is Fe and inevitable impurities, wherein the Ni equivalent / Cr equivalent is 0.53.

[0180] Compared with example 1, the Ni equivalent / Cr equivalent is 0.53, which is higher than the range defined in the application 0.35-0.45, resulting in too high austenite content, reducing ferrite content and reducing strength.

[0181] Comparative Example 2

[0182] The present comparative example provides a kind of duplex stainless steel and large diameter duplex stainless steel liquid slip ring forging and its preparation method, which are basically same with example 1, and different from example 1 in that there is no annealing treatment step in step 2.

[0183] Specifically, step 2 includes:

[0184] S201: the surface of the ingot is subjected to machining and skinning treatment to remove surface defects such as slag grooves;

[0185] S202: the ingot is heated to 1,050 DEG C and kept for 8 h for temperature equalization;

[0186] S203: The ingot is raised to 1200°C for high-temperature homogenization treatment, and is kept for 12h;

[0187] S204: The furnace is discharged for forging, and a blank is obtained.

[0188] Compared with Example 1, step 2 has no annealing treatment step before peeling, and cracks due to excessive stress in the forging preparation process, so that subsequent processing cannot be performed.

[0189] Comparative Example 3

[0190] This comparative example provides a duplex stainless steel and a large-diameter duplex stainless steel liquid sliding ring forging and a preparation method thereof, which are basically the same as Example 1, and the difference from Example 1 is that there is no peeling treatment step in step 2.

[0191] Specifically, step 2 includes:

[0192] S201: Annealing treatment, kept for 10h in a 1030°C heat treatment furnace, and then furnace-cooled to room temperature;

[0193] S202: Temperature rising and homogenizing: the ingot is raised to 1050°C, and is kept for 8h for homogenizing;

[0194] S203: The ingot is raised to 1200°C for high-temperature homogenization treatment, and is kept for 12h;

[0195] S204: The furnace is discharged for forging, and a blank is obtained.

[0196] Compared with Example 1, there is no peeling treatment step after annealing, and the surface defect is serious, cracks in the forging process, so that subsequent processing cannot be performed.

[0197] Comparative Example 4

[0198] This comparative example provides a duplex stainless steel and a large-diameter duplex stainless steel liquid sliding ring forging and a preparation method thereof, which are basically the same as Example 1, and the difference from Example 1 is that in step 3, if cracking occurs, air cooling to below 200°C is performed for cleaning.

[0199] Compared with Example 1, after cracking in step 3, no hot cleaning is performed at above 900°C, which leads to crack propagation, and the crack propagation leads to the forging being scrapped, so that subsequent processing cannot be performed.

[0200] Comparative Example 5

[0201] This comparative example provides a duplex stainless steel and a large-diameter duplex stainless steel liquid sliding ring forging and a preparation method thereof, which are basically the same as Example 1, and the difference from Example 1 is that in step 5, the two ring-shaped blank forgings obtained in step 4 are directly put into a 650°C heat treatment furnace for 10h, and then water-cooled.

[0202] Compared with Example 1, the temperature of Step 5 is 650℃, which is lower than the range of 1000-1100℃ defined in the application, and the crack propagation after discharging, and a large amount of brittle phase precipitation exists (as shown in Figure 4 , the impact shows brittle fracture.

[0203] Comparative Example 6

[0204] This comparative example provides a kind of duplex stainless steel and large diameter duplex stainless steel liquid sliding ring forge piece and its preparation method, which is basically the same as Example 1, and the difference from Example 1 is that the two ring blanks obtained in Step 4 are directly placed in a 1000℃ heat treatment furnace for 10h and then furnace cooled.

[0205] Compared with Example 1, Step 5 uses furnace cooling, and harmful phase precipitates. As shown in Figure 5 , the white part is austenite, and the harmful phase in the annealed state will easily nucleate to form austenite during the later performance heat treatment, which will increase the amount of austenite and lead to poor performance.

[0206] Comparative Example 7

[0207] This comparative example provides a kind of duplex stainless steel and large diameter duplex stainless steel liquid sliding ring forge piece and its preparation method, which is basically the same as Example 1, and the difference from Example 1 is that:

[0208] Step 6: The two blank forgings obtained in Step 5 are rough machined and inspected, and after passing the inspection, they are subjected to performance heat treatment, and are heated to a 1050℃ heat treatment furnace at a rate of 50℃ / h, and are oil cooled to below 200℃ after being kept for 10h, to complete the heat treatment process.

[0209] Compared with Example 1, Step 6 uses oil cooling, and the impact performance is poor.

[0210] Comparative Example 8

[0211] This comparative example provides a kind of duplex stainless steel and large diameter duplex stainless steel liquid sliding ring forge piece and its preparation method, which is basically the same as Example 1, and the difference from Example 1 is that, in Step 1, only the first melting in the vacuum induction furnace is included, and the second melting of the electrode bar material by electroslag remelting is not included.

[0212] In this comparative example, since only one melting is used in Step 1, there will be segregation and serious internal defects.

[0213] Comparative Example 9

[0214] The comparative example provides a duplex stainless steel and a large-diameter duplex stainless steel liquid slip ring forging and a preparation method thereof, which are basically the same as those of example 1, and the difference from example 1 is that the composition of the duplex stainless steel includes, by mass percentage: C: 0.02%, Si: 0.45%, Mn: 1.2%, Cr: 22.5%, Mo: 3%, Ni: 3.5%, N: 0.15%, P: 0.020%, S: 0.015%, and the rest is Fe and inevitable impurities, wherein the Ni equivalent / Cr equivalent is 0.33.

[0215] Compared with example 1, the Ni equivalent / Cr equivalent is 0.33, which is lower than the range of 0.35-0.45 defined in the application, resulting in too low austenite content, increasing ferrite content, poor toughness and poor corrosion resistance.

[0216] Specifically, the properties of examples 1-3 and comparative examples 1-9 are shown in table 1.

[0217] Table 1 Room temperature properties of examples and comparative examples

[0218]

[0219] The above is only the preferred specific embodiment of the application, but the protection scope of the application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered within the protection scope of the application.

Claims

1. A method for preparing a large diameter duplex stainless steel liquid slip ring forging, characterized in that: include: Step 1: Obtain raw materials according to the alloy ratio, and perform secondary smelting on the raw materials to obtain steel ingots; The components of the raw materials, calculated by mass percentage, include: C: 0.01-0.03%, Si: 0.30%-0.60%, Mn: 1.0%-1.5%, Cr: 22.0%-23.0%, Mo: 2.5%-3.5%, Ni: 4.5%-5.5%, N: 0.08%-0.20%, P≤0.025%, S≤0.02%, and the remaining components are Fe and unavoidable impurities; Step 2: annealing the steel ingot obtained in step 1, and then performing processing, peeling, heating and high-temperature homogenization to obtain a billet; Wherein, the step 2 specifically includes: S201: Annealing treatment: keep the temperature in a heat treatment furnace at 1000-1100℃ for 10-15h and then cool to room temperature; S202: Processing and peeling the surface of the steel ingot; S203: Heating and evenly balancing the temperature: heating the steel ingot to 1000-1050°C and keeping it at that temperature for 10-15 hours to evenly balance the temperature; S204: Heat the steel ingot to 1150-1300℃ for homogenization and keep it warm for 10-20h; Step 3: The blank obtained in step 2 is subjected to a forging process of splitting, drawing, and then dividing into at least two blank forgings to obtain at least two forging blanks; The initial forging temperature during the forging process is 1150-1300°C, the final forging temperature is 950-1050°C, and the pressing rate is less than 0.01s each time. -1 ; Step 4: Forging the at least two forging blanks obtained in step 3 to obtain at least two annular blank forgings; The initial forging temperature in the forging process is 1150-1300°C, the final forging temperature is 950-1050°C, and the pressing rate is less than 0.01s each time. -1 ; Step 5: heat treating the at least two annular blank forgings obtained in step 4 at 1000-1100° C. and keeping the temperature for 10-15 hours, and then water cooling; Step 6: Rough machining and flaw detection are performed on at least two annular blank forgings obtained in step 5, and after passing the test, performance heat treatment is performed; The heat treatment process is as follows: heating the temperature to 1000-1100°C at a heating rate of ≤80°C / h, keeping the temperature in a heat treatment furnace for 10-15h, and then cooling the temperature with water to below 200°C.

2. The preparation method according to claim 1, characterized in that Step 1 includes: S101: The raw materials are melted and cast into electrode bars in a vacuum induction furnace with a tapping temperature of 1500-1600°C; S102: Electroslag remelting or vacuum consumable remelting is performed on the electrode rod material.

3. A large diameter duplex stainless steel liquid slip ring forging obtained by the preparation method according to claim 1 or 2, characterized in that: The components of the forging include, by mass percentage, C: 0.01-0.03%, Si: 0.30%-0.60%, Mn: 1.0%-1.5%, Cr: 22.0%-23.0%, Mo: 2.5%-3.5%, Ni: 4.5%-5.5%, N: 0.08%-0.20%, P≤0.025%, S≤0.02%, and the remaining components are Fe and unavoidable impurities.

4. The large diameter duplex stainless steel liquid slip ring forging according to claim 3, characterized in that: The Ni equivalent / Cr equivalent is in the range of 0.35-0.

45.

5. The large diameter duplex stainless steel liquid slip ring forging according to claim 3, characterized in that: The components of the forging include, by mass percentage, C: 0.01-0.03%, Si: 0.40%~0.50%, Mn: 1.0%~1.2%, Cr: 22.0%~22.5%, Mo: 2.8%~3.3%, Ni: 4.8%~5.3%, N: 0.10%~0.20%, P≤0.025%, S≤0.02%, and the remaining components are Fe and unavoidable impurities.

6. The large diameter duplex stainless steel liquid slip ring forging according to claim 3, characterized in that: The diameter of the forging is above.

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