Dual-phase steel maritime work liquid slip ring forge piece and forging method thereof

Abstract

The invention discloses a dual-phase steel maritime work liquid slip ring forge piece and a forging method thereof, belongs to the technical field of liquid slip rings, and aims at solving the problems that in the prior art, in the maritime work liquid slip ring forging process, cracks are prone to occurring, and the yield is low. The liquid slip ring forge piece for the dual-phase steel maritime work comprises the following components in percentage by mass: 0.01%-0.03% of C, 0.30%-0.60% of Si, 1.0%-1.6% of Mn, 22.0%-23.0% of Cr, 2.5%-3.5% of Mo, 4.5%-6.0% of Ni, 0.08%-0.20% of N, 0.01%-0.04% of Cu, 0.01%-0.05% of V, less than or equal to 0.025% of P, less than or equal to 0.02% of S, less than or equal to 0.01% of Sn, less than or equal to 0.012% of As, less than or equal to 0.004% of Sb and the balance of Fe and inevitable trace impurities. When the dual-phase steel liquid slip ring forge piece for maritime work is forged, cracks are few.

Description

Technical Field

[0001] The invention relates to the technical field of liquid slip rings, and in particular to a dual-phase steel marine liquid slip ring forging and a forging method thereof. Background Art

[0002] In recent years, with the advancement of technology, marginal oil and gas fields and other sea areas with increasingly mature development have attracted more and more attention. The new single-point mooring SCM system is a key equipment for marginal oil fields. The core forging liquid sliding ring is made of duplex stainless steel. The special duplex structure makes it have the strength and corrosion resistance of ferrite and the toughness and processing performance of austenite. However, some process and technical problems in production restrict its application.

[0003] Due to the narrow forging temperature range, strong thermal sensitivity, high resistance and low plasticity of dual-phase steel liquid slip ring, cracks are very easy to occur during the forging process. Statistical analysis of cracks found that the direction of cracks is both longitudinal and transverse, and some cracks are located on the surface of the forging, while others are deeper; some cracks appear in the process of roughening the steel ingot, while others appear in the process of drawing. The time when cracks appear is in the early stage of the forging process, while others are in the later stage. The generation of cracks reduces the yield rate and good product rate of the product, affects the production process, causes rework and repair, increases production costs, and becomes an important problem in the manufacturing process. Forging cracks have always been a key issue restricting the hot processing performance of dual-phase steel liquid slip ring forgings, and therefore have become a hot and difficult issue in discussion and research in this field. In order to avoid the generation of forging cracks, corresponding measures must be taken according to different causes to eliminate this problem. Summary of the invention

[0004] In view of the above situation, the present invention aims to provide a duplex steel marine fluid slip ring forging and a forging method thereof, so as to solve the problems of easy cracking and low yield rate in the existing marine fluid slip ring forging.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions:

[0006] On the one hand, the present invention provides a duplex steel marine engineering liquid slip ring forging, and the components of the duplex steel marine engineering liquid slip ring forging include, by mass percentage: C: 0.01% ~ 0.03%, Si: 0.30% ~ 0.60%, Mn: 1.0% ~ 1.6%, Cr: 22.0% ~ 23.0%, Mo: 2.5% ~ 3.5%, Ni: 4.5% ~ 6.0%, N: 0.08% ~ 0.20%, Cu: 0.01% ~ 0.04%, V: 0.01% ~ 0.05%, P ≤ 0.025%, S ≤ 0.02%, Sn ≤ 0.01%, As ≤ 0.012%, Sb ≤ 0.004%, and the balance is Fe and inevitable trace impurities.

[0007] Furthermore, A / F is between 0.35 and 0.45, wherein A=Ni+30(C+N)+0.5Mn, F=Cr+Mo+1.5Si+5V, and Ni, C, N, Mn, Cr, Mo, Si, and V refer to the mass percentages of the elements.

[0008] Furthermore, the components of the duplex steel marine engineering liquid slip ring forging include, by mass percentage: C: 0.01% ~ 0.025%, Si: 0.40% ~ 0.50%, Mn: 1.3% ~ 1.6%, Cr: 22.1% ~ 22.8%, Mo: 2.8% ~ 3.3%, Ni: 5.0% ~ 5.5%, N: 0.10% ~ 0.20%, Cu: 0.01% ~ 0.03%, V: 0.01% ~ 0.03%, P ≤ 0.025%, S ≤ 0.02%, Sn ≤ 0.01%, As ≤ 0.012%, Sb ≤ 0.004%, and the balance is Fe and inevitable trace impurities.

[0009] The present invention also provides a forging method of the above-mentioned dual-phase steel marine engineering hydraulic slip ring forging, comprising the following steps:

[0010] Step S1: Clean the surface of the steel ingot and load it into the furnace;

[0011] Step S2: subjecting the steel ingot to 4-stage gradient heating and heat preservation;

[0012] Step S3: preheating the forging tool;

[0013] Step S4: forging the steel ingot; the initial forging temperature is controlled at 1180°C to 1200°C, and the final forging temperature is controlled at 950°C to 1050°C;

[0014] Step S5: firstly perform post-forging heat treatment on the forged forging blank, and then perform performance heat treatment.

[0015] Furthermore, in step S1, a shim is used to raise the steel ingot when it is heated, and the height of the shim is greater than 250 mm.

[0016] Furthermore, in step S2, the four-stage gradient heating and heat preservation includes:

[0017] S201, slowly heating the steel ingot from room temperature to 300-350°C, and keeping the temperature;

[0018] S202, slowly heat to 600-650°C, keep warm;

[0019] S203, heating to 1000-1100°C, keeping warm;

[0020] S204. Heat to 1150-1200°C and keep warm.

[0021] Furthermore, the heating rates in S203 and S204 are greater than the heating rates in S201 and S202.

[0022] Furthermore, in step S3, the forging tool is preheated to 150°C to 200°C.

[0023] Furthermore, the post-forging heat treatment includes: hot delivery and hot charging of the forgings into a furnace after forging, annealing at a temperature of 650-670°C, keeping the temperature for more than 15 hours, and then air cooling to room temperature.

[0024] Furthermore, the performance heat treatment includes the following steps:

[0025] S501, slowly heating the steel ingot from room temperature to 300-350°C, and keeping the temperature;

[0026] S502, slowly heat to 600-650°C, keep warm;

[0027] S503. Heat to 1000-1100°C, keep warm, and then water cool to the forging surface temperature <80°C.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] a) The dual-phase steel marine hydraulic slip ring forging of the present invention ensures comprehensive performance by optimizing the types of alloy elements and accurately controlling the content of each element. In addition, the content of S element that is prone to hot brittleness during forging is controlled, and the content of some low melting point elements (such as Sn, As, Sb) that are prone to cause cracks during forging is controlled, which is conducive to reducing the occurrence of forging cracks.

[0030] b) In the forging method of the present invention, the surface of the steel ingot is cleaned before loading into the furnace, so as to prevent the further expansion of surface scars, cracks, heavy skin and other defects during the forging process, which may cause cracks; the forging tools are required to have smooth rounded corners to prevent them from scratching the forgings. In addition, the forging tools must be preheated to prevent cracks caused by uneven contact with the forgings.

[0031] c) The forging method of the present invention adopts 4 stages of heating and heat preservation in total, and adopts 2 stages of gradient heating and heat preservation in the low temperature stage. The low temperature stage has poor plasticity to prevent the temperature from unevenly generating thermal stress in the structure; the high temperature stage adopts 2 stages of heating and heat preservation to prevent grain growth and overburning. In addition, the low temperature stage is heated slowly, and the strict heating system can reduce the thermal stress of the forging and prevent cracks.

[0032] d) The forging method of the present invention helps to reduce the occurrence of forging cracks by strictly controlling the initial forging and final forging temperatures; and helps to reduce the occurrence of cracking by combining the control of forging deformation and deformation rate.

[0033] e) The present invention adopts post-forging hot delivery and hot charging into the furnace for post-forging heat treatment to prevent cracks from occurring during the high-temperature cooling process of the forgings after forging.

[0034] f) The forgings prepared by the forging method of the present invention have a low tendency to crack, few surface cracks, are smooth after processing, and have a high yield rate. The forgings have excellent performance and can meet the use requirements. For example, the tensile strength is above 712MPa (for example, 712-746MPa), the yield strength is above 465MPa (for example, 465-485MPa), the elongation is above 39% (for example, 39%-45%), the surface reduction is above 76% (for example, 76%-81%), the impact energy (-29°C) is an average of 37J or more (for example, 37-60J), and the corrosion resistance is ≥720h without breaking.

[0035] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the contents particularly pointed out in the written description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0037] Figure 1 A heating process in the forging method of the present invention;

[0038] Figure 2 The forging blank performance heat treatment process of the present invention;

[0039] Figure 3 This is a physical picture of the marine fluid slip ring forging of the present invention;

[0040] Figure 4 This is the crack diagram of the marine fluid slip ring forging of comparative example 1. DETAILED DESCRIPTION

[0041] Preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used to explain the principles of the present invention together with the embodiments of the present invention.

[0042] The invention provides a dual-phase steel marine engineering liquid slip ring forging. The components of the dual-phase steel marine engineering liquid slip ring forging include, by mass percentage, C: 0.01%-0.03%, Si: 0.30%-0.60%, Mn: 1.0%-1.6%, Cr: 22.0%-23.0%, Mo: 2.5%-3.5%, Ni: 4.5%-6.0%, N: 0.08%-0.20%, Cu: 0.01%-0.04%, V: 0.01%-0.05%, P≤0.025%, S≤0.02%, Sn≤0.01%, As≤0.012%, Sb≤0.004%, and the balance is Fe and inevitable trace impurities.

[0043] The following is a detailed description of the effects and dosage of the components in the present invention:

[0044] C: C is a strong austenite-forming element. C will cause sensitization corrosion and intergranular corrosion problems after welding of duplex stainless steel, affecting the weldability and corrosion resistance of stainless steel. The present invention adopts ultra-low carbon control. In order to ensure that duplex stainless steel has good strength and toughness matching, the present invention limits the C content to 0.01% to 0.03%.

[0045] Si: Si has a good solid solution strengthening effect, which can improve the passivation ability of the material, thereby improving the corrosion resistance. However, too high Si element will reduce the plasticity and toughness of the steel and increase the temper brittleness, so the present invention limits the Si content to 0.30% to 0.60%.

[0046] Mn: Mn is an element that stabilizes austenite and can increase the solubility of nitrogen in steel, thus exerting the effect of nitrogen. Mn will reduce the corrosion resistance of duplex stainless steel, promote the precipitation of brittle phases such as σ in stainless steel, and be detrimental to impact toughness. Therefore, the present invention limits the Mn content to 1.0% to 1.6%.

[0047] Cr: Cr is an element that can stabilize ferrite and reduce the austenite zone. Cr can increase the corrosion resistance of stainless steel and improve the oxidation resistance of steel. An increase in Cr content will promote the precipitation temperature of the harmful σ phase, resulting in a narrow forging temperature range and an increased risk of cracking; a too low Cr content will reduce corrosion resistance and affect the ratio of the two phases. The addition amount of Cr in the present invention is generally controlled at: 22.0% to 23.0%.

[0048] Ni: Ni plays a role in solid solution strengthening and stabilizing austenite, and regulating the ratio of ferrite to austenite. Too much Ni will reduce the ferrite phase, making it easier for the σ phase to precipitate, which is not good for the structure. Too little Ni will expand the ferrite phase and reduce the toughness and weldability of the dual-phase steel. The Ni content of the present invention is controlled at 4.5% to 6.0%.

[0049] Mo: Mo is a ferrite-forming element that can expand the ferrite phase region. Mo can improve the corrosion resistance, pitting resistance, and crevice corrosion resistance of duplex stainless steel. The increase in Mo content promotes the precipitation of metal interstitial phases σ and χ, causing the precipitation temperature to move up and the forging temperature range to narrow, thereby increasing the embrittlement tendency. If the Mo content is too low, the corrosion resistance is insufficient. Therefore, the Mo content of the present invention is controlled at 2.5% to 3.5%.

[0050] N: N is an element that stabilizes and expands austenite, and can replace Ni to save costs and improve the strength and corrosion resistance of stainless steel. Too high a Ni content will cause shrinkage and looseness in the ingot, while too low a Ni content is not conducive to improving strength and corrosion resistance. The N content of the present invention is controlled at 0.08% to 0.20%.

[0051] Cu: Cu is an austenite forming and stabilizing element. A small amount of copper is beneficial to improving the strength and corrosion resistance of stainless steel. However, an increase in Cu will reduce plasticity and welding performance. The Cu content of the present invention is controlled at 0.01% to 0.04%.

[0052] V: V can refine grains and improve material strength, but too high a V content reduces the plasticity of dual-phase steel and affects its hot working properties. The V content of the present invention is controlled at 0.01% to 0.05%.

[0053] P: P is a harmful element. The P content in the present invention is controlled to be ≤0.025%.

[0054] S: S is a harmful element. A high content of S easily leads to hot brittleness during forging. Therefore, the S content in the present invention is controlled to be ≤0.02%.

[0055] Sb, Sn and As: They are low melting point elements and tend to segregate at grain boundaries. When these elements segregate at grain boundaries, they reduce the binding energy of grain boundaries and the strength of grain boundaries. Therefore, the present invention controls Sn≤0.01%, As≤0.012%, and Sb≤0.004%.

[0056] A: The ability of each element to form austenite, A=Ni+30(C+N)+0.5Mn, where Ni, C, N, and Mn refer to the mass percentage of the elements.

[0057] F: The ability of each element to form ferrite, F = Cr + Mo + 1.5Si + 5V, where Cr, Mo, Si, and V refer to the mass percentage of the elements.

[0058] It should be noted that a high A / F represents a high austenite content, and a too low A / F represents a high ferrite content. When the present invention controls A / F within the range of 0.35 to 0.45, the volume ratio of austenite and ferrite can be about 1:1. This ratio can maintain the comprehensive properties of duplex steel such as high corrosion resistance, high strength and high toughness. If the ferrite content is high, the strength will be improved, but the toughness and corrosion resistance are poor. If the austenite content is high, the toughness and corrosion resistance are improved, but the strength is deteriorated.

[0059] In order to further improve the comprehensive performance of the above-mentioned duplex steel marine engineering liquid slip ring forgings, the components of the above-mentioned duplex steel marine engineering liquid slip ring forgings can be calculated by mass percentage: C: 0.01%~0.025%, Si: 0.40%~0.50%, Mn: 1.3%~1.6%, Cr: 22.1%~22.8%, Mo: 2.8%~3.3%, Ni: 5.0%~5.5%, N: 0.10%~0.20%, Cu: 0.01%~0.03%, V: 0.01%~0.03%, P≤0.025%, S≤0.02%, Sn≤0.01%, As≤0.012%, Sb≤0.004%, and the balance is Fe and inevitable trace impurities.

[0060] Specifically, A / F is controlled at 0.38-0.45.

[0061] Specifically, the microstructure of the above-mentioned dual-phase steel marine engineering fluid slip ring includes ferrite and austenite, the volume percentage of ferrite is 45% to 55%. Ferrite is rich in elements such as Cr, Mo, and C, and austenite is rich in elements such as Ni.

[0062] The present invention also provides a forging method of the above-mentioned dual-phase steel marine engineering hydraulic slip ring forging, comprising the following steps:

[0063] Step S1: Clean the surface of the steel ingot and load it into the furnace;

[0064] Step S2: subjecting the steel ingot to 4-stage gradient heating and heat preservation for high-temperature homogenization;

[0065] Step S3: preheating the forging tool;

[0066] Step S4: forging the steel ingot; the initial forging temperature is controlled at 1180°C to 1200°C, and the final forging temperature is controlled at 950°C to 1050°C;

[0067] Step S5: firstly perform post-forging heat treatment on the forged forging blank, and then perform performance heat treatment.

[0068] Specifically, in the above step S1, it is required that the surface of the steel ingot is free of defects such as scars, cracks, heavy skin pores and inclusions, and the ingot surface may be peeled if necessary to prevent these defects from further expanding during the forging process and causing cracks.

[0069] Specifically, in the above step S1, the connection on the surface of the steel ingot should be smooth and without edges and corners.

[0070] Specifically, in the above step S1, the iron oxide scale in the heating furnace is cleaned, and the steel ingot is raised by a pad when heated, and the height of the pad is greater than 250mm, so that there is enough space for the furnace gas to enter the lower part of the forging to ensure that the temperature of the forging is uniform.

[0071] Specifically, in the above step S1, the distance between the steel ingot and the burner of the heating furnace is greater than 50 mm, and the distance between the steel ingot and the front and rear walls is greater than 40 mm, so as to prevent the steel ingot from being too close to the burner and the front and rear walls, resulting in poor furnace gas flow and uneven heating of the steel ingot.

[0072] Specifically, Figure 1 As shown, in the above step S2, the 4-stage gradient heating and heat preservation includes:

[0073] S201, slowly heating the steel ingot from room temperature to 300-350°C, and keeping the temperature;

[0074] S202, slowly heat to 600-650°C, keep warm;

[0075] S203, heating to 1000-1100°C, keeping warm;

[0076] S204, heating to 1150-1200°C, and keeping the temperature. The heating rate in S203 and S204 may be greater than the heating rate in S201 and S202.

[0077] Specifically, in the above step S201, the duplex steel marine engineering liquid slip ring forging of the present invention is duplex stainless steel, and its thermal conductivity in the low temperature zone, especially below 650°C, is poor, and needs to be heated slowly to reduce the thermal stress caused by the uneven temperature inside the material. Rapid heating is prone to cracking, so it is necessary to control the heating rate, and the heating rate is ≦40°C / h, for example, 10 to 40°C / h. Taking into account the poor plasticity of the material in the low temperature zone, two temperature platforms are set in the low temperature zone, and the first temperature platform should not be too high so as to keep a distance from the 650°C platform. Therefore, the heating is controlled to 300 to 350°C.

[0078] Specifically, in the above step S201, the insulation time should not be too long, because if it is too long, the fuel consumption will be large and the heating efficiency will be low; if the insulation time is too short, the steel ingot will not be heated through and will not play a role in reducing tissue stress. Therefore, the insulation time is controlled to be ≥10h.

[0079] Specifically, in the above step S202, the material is still in the low temperature zone, and the heating rate should not be too high; therefore, the heating rate is controlled to be ≤40°C / h, for example, 10-40°C / h. This temperature is a watershed between the low temperature zone and the high temperature zone of the material, and this temperature should not be too high. Considering the characteristics of the dual-phase steel of the present invention, the temperature is preferably set at 600-650°C.

[0080] Specifically, the heat preservation time in the above step S202 is greater than the heat preservation time in S201. The heat preservation time in step S202 is ≥ 12 hours.

[0081] In addition, to prevent grain coarsening and overburning of dual-phase steel at high temperature, two platforms are set in the high temperature zone. One platform is used for preheating forgings. The temperature is slightly lower, and the grains are not easy to grow. The time can be slightly longer. The other platform is used for homogenization. Due to the higher temperature, overburning and grain coarsening are prevented, and the time is slightly shorter.

[0082] Specifically, in the above step S203, at this time, the temperature of the steel ingot is increased and the plasticity has been improved, so the heating rate can be slightly higher than that of S201 and S202. Considering the poor thermal conductivity of the dual-phase steel of the present invention, the heating rate in the high temperature section should not be too high. Therefore, the heating rate can be set to be controlled to be ≤80°C / h, for example, 40 to 80°C / h, and the holding time is 26 to 28h when the steel ingot is heated through and the temperature is uniform.

[0083] Considering that the main function of S204 is to ensure the uniformity of the initial forging temperature and composition, the temperature should not be too high. If the holding temperature is too high, the forgings are prone to overburning. However, the holding temperature should not be too low, otherwise the plasticity of the forgings will be reduced, and they will be prone to cracking, which is not conducive to forging. The holding time should not be too long to prevent grain growth; but the time should not be too short, otherwise the temperature of the forgings will be uneven. Therefore, the heating is controlled to 1150-1200℃, and the holding time is 22-26h.

[0084] It should be noted that in the above heating steps, the heating specifications must be strictly followed and temperature records must be made every 30 minutes.

[0085] Specifically, in the above step S3, the forging tool is inspected before preheating the forging tool. The flat anvil or V-shaped anvil used should be checked first to see if there are surface defects such as crack pits, protrusions, and stacked burrs. If there are, they must be polished to prevent them from damaging the forging. The R angle must be smooth. The lifting clamp must be polished to ensure smoothness.

[0086] Specifically, in the above step S3, the forging tool includes an upper anvil and a lower anvil used for forging. In order to prevent the forging tool from contacting the forging and causing the forging to cool down, thereby preventing cracks from being generated due to uneven hot and cold, the forging tool needs to be preheated. The preheating temperature should not be too high, otherwise the strength of the forging tool will be reduced. Therefore, it is advisable to preheat the forging tool to 150℃~200℃.

[0087] Specifically, in the above step S4, considering that when the forging temperature of the material of the present invention is higher than 1200°C, the grains are prone to coarsening, the intergranular weakening, the bonding force is reduced, and forging cracks are easily caused; as the forging temperature decreases, the deformation resistance is larger and the forgeability becomes worse; therefore, the present invention controls the initial forging temperature at 1180°C to 1200°C.

[0088] Specifically, in the above step S4, considering that the forgings are hot transported and hot loaded into the furnace after forging, a small amount of σ phase and χ phase are precipitated at the grain boundary between ferrite and austenite during the furnace cooling process. The components of the two phases are not much different, both containing Fe, Cr, Mo, Ni, etc., but the crystal types are different, one is face-centered and the other is body-centered. The precipitation temperature of the σ phase is 940°C, and it precipitates faster in the range of 930-800°C. Therefore, the final forging temperature is controlled at 950°C-1050°C.

[0089] Specifically, in the above step S4, forging includes two stretching, one upsetting, pre-expansion of the horse bar and the expansion of the mandrel, expansion of the special hammer head and other processes. Considering that the material of the present invention is dual-phase steel, its processing performance is poor, large deformation forgings are prone to cracking, too small deformation takes a long time to forge, large temperature drop, reduced plasticity and affects processing efficiency, and the forging deformation needs to be strictly controlled. Therefore, the single roughing is controlled to be ≤50mm (for example, 30-50mm), and the single stretching and expansion is controlled to be ≤30mm (for example, 15-30mm).

[0090] Specifically, in the above step S4, the heating time of the forging process is determined according to the length of the forging time. If the forging time is long, the temperature drop of the forging is large, and the forging needs to be heated for a longer time after the forging is returned to the furnace; if the forging time is short, the temperature drop of the forging is small, and the heating time of the forging after the forging is short.

[0091] Specifically, in the above step S4, considering that when the deformation starts, the deformation rate is too high, the deformation resistance is large, the forging plasticity is low, and it is easy to crack, and the deformation rate is too low, which affects the processing efficiency. Therefore, according to the hot working diagram, the deformation rate at the beginning of deformation is controlled to be 0.01s -1 After the forging completes one round of deformation and the plasticity is improved, the deformation rate will be increased again, but it cannot be greater than 0.1S -1 (For example, 0.01 to 0.1s -1 ).

[0092] Specifically, in the above step S5:

[0093] Post-forging heat treatment includes: hot delivery and hot loading of forgings into furnaces to prevent cracks from occurring during the cooling process of forgings; post-forging heat treatment is annealing at a temperature of 650-670°C, keeping warm for 15-18 hours and then air cooling to room temperature.

[0094] like Figure 2 As shown, the performance heat treatment includes the following steps:

[0095] S501, slowly heating the steel ingot from room temperature to 300-350°C, and keeping the temperature;

[0096] S502, slowly heat to 600-650°C, keep warm;

[0097] S503, heating to 1000-1100°C, and keeping warm; the heating rate in S503 may be greater than the heating rates in S501 and S502.

[0098] Specifically, the heating rate of S501 and S502 is ≤40°C / h, for example, 20 to 40°C / h. The heating rate of S503 is ≤80°C / h, for example, 40 to 80°C / h.

[0099] Specifically, considering the size of the forging, the holding time in S501, S502, and S503 is extended in sequence. For example, the holding time in S501 is 8 to 10 hours, the holding time in S502 is 10 to 12 hours, and the holding time in S503 is 15 to 18 hours.

[0100] Specifically, in the above S503, water cooling is then performed until the surface temperature of the forging is less than 80°C.

[0101] Specifically, the S503 is heat-insulated and then water-quenched to inhibit precipitation phase and prevent cracks from occurring.

[0102] Specifically, the microstructure of the above-mentioned dual-phase steel marine engineering fluid slip ring includes ferrite and austenite, the volume percentage of ferrite is 45% to 55%. Ferrite is rich in elements such as Cr, Mo, and C, and austenite is rich in elements such as Ni.

[0103] Specifically, the method for preparing the steel ingot of the present invention comprises:

[0104] Step 1: According to the alloy composition ratio, the alloy is melted in a vacuum induction furnace and cast into electrode rods, and then electroslag remelting is performed to obtain a purer steel ingot;

[0105] Step 2: The electroslag ingot is first annealed to eliminate thermal stress.

[0106] The dual-phase steel marine engineering liquid slip ring forging of the present invention ensures comprehensive performance by optimizing the types of alloy elements and accurately controlling the content of each element, such as controlling the content of the S element that is prone to hot brittleness during forging, and controlling the content of some low-melting-point elements (such as Sn, As, Sb) that are prone to cause cracks during forging, which is beneficial to reducing the occurrence of forging cracks.

[0107] In the forging method of the present invention, the surface of the steel ingot is first cleaned and then loaded into the furnace to prevent the further expansion of surface scars, cracks, heavy skin and other defects during the forging process and the generation of cracks; the forging tool is required to have smooth rounded corners to prevent it from scratching the forging. In addition, the forging tool must be preheated to prevent cracks caused by uneven contact with the forging.

[0108] The forging method of the present invention adopts four-stage gradient heating and heat preservation, and controls the heating rate to prevent thermal stress caused by uneven temperature in the low temperature stage of the material. The strict heating system can reduce the heating stress of the forging and prevent cracks from occurring.

[0109] The forging method of the present invention is beneficial to reducing the occurrence of forging cracks by strictly controlling the initial forging and final forging temperatures; and is beneficial to reducing cracking by combining the control of deformation amount and deformation rate.

[0110] In the forging method of the present invention, hot delivery and hot charging into the furnace are adopted in the post-forging heat treatment process to prevent cracks from being generated in the high-temperature cooling process of the forging after forging.

[0111] Examples 1-4

[0112] The advantages of precise control of ingredients and process parameters of the present invention are demonstrated below with specific examples and comparative examples.

[0113] Embodiments 1-4 of the present invention provide a dual-phase steel marine hydraulic slip ring forging and a forging method thereof. The chemical composition of the marine hydraulic slip ring of Embodiments 1-4 is shown in Table 1.

[0114] The forging method of the marine fluid slip ring of embodiment 1 comprises:

[0115] Step S1: clean the surface of the steel ingot and load it into the furnace; the height of the shim is 270mm, the distance between the steel ingot and the burner of the heating furnace is 60mm, and the distance between the steel ingot and the front and rear walls is 50mm;

[0116] Step S2: subjecting the steel ingot to a 4-stage gradient heat preservation process for homogenization; specifically comprising:

[0117] S201, heating to 300°C at a heating rate of 40°C / h, keeping warm for 10h;

[0118] S202, heating to 600°C at a heating rate of 40 / h, keeping warm for 12h;

[0119] S203, heating to 1050°C at a heating rate of 50°C / h, and keeping warm for 26h;

[0120] S204, heat to 1200°C at a heating rate of 50°C / h and keep warm for 24h.

[0121] Step S3: preheating the forging tool: heating the upper and lower anvils used for forging to 150°C;

[0122] Step S4: Forging the steel ingot after gas cutting the cap and the nozzle; forging includes:

[0123] The steel is stretched once and then returned to the furnace for heating;

[0124] The second fire is to lengthen the furnace and then return to the furnace for heating;

[0125] The steel is upset in three fires and then reheated;

[0126] Pre-expand the hole of the horse bar, flatten the end surface, and heat it in the furnace;

[0127] The core rod is drawn out, the end surface is flattened, and the core rod is returned to the furnace for heating;

[0128] A special hammer is used to expand the hole to produce the finished forging.

[0129] For the above fires, the initial and final forging temperatures are strictly controlled; the initial forging temperature is 1180℃, and the final forging temperature is 1020℃; the single drawing and hole expansion is 20mm, and the single upsetting is 40mm;

[0130] Step S5: performing post-forging heat treatment on the forging blank, and then performing performance heat treatment to obtain a marine fluid slip ring forging;

[0131] Heat treatment after forging: After forging, the forgings are hot transported and hot loaded into the tempering furnace, the annealing temperature is 660℃, and after keeping warm for 16 hours, they are air-cooled to room temperature;

[0132] Performance heat treatment: heat to 300℃ at a heating rate of 40℃ / h, keep warm for 10h; heat to 600℃ at a heating rate of 40 / h, keep warm for 12h; heat to 1050℃ at a heating rate of 50℃ / h, keep warm for 16h, quench after equalization of temperature.

[0133] The forging method of the marine fluid slip ring of Example 2 is substantially the same as that of Example 1, except that:

[0134] In step S2, the holding time of S201 and S202 is 11h and 13h;

[0135] In step S4, the initial forging temperature is 1200°C and the final forging temperature is 980°C;

[0136] In step S5, the performance heat treatment is performed at a temperature of 1060° C. and kept for 15 hours.

[0137] The forging method of the marine fluid slip ring of Example 3 is substantially the same as that of Example 1, except that:

[0138] In step S201 and S202 of step S2, the heating rate is 35°C / h;

[0139] In step S3, the upper and lower anvils are heated to 200°C.

[0140] The forging method of the marine fluid slip ring of Example 4 is substantially the same as that of Example 1, except that:

[0141] In step S2, the holding time of S201 and S202 is 14h;

[0142] In step S203, the holding time is 28 hours;

[0143] In step S3, the upper and lower anvils are heated to 200°C;

[0144] In step S4, the initial forging temperature is 1200°C and the final forging temperature is 960°C;

[0145] In step S5, the performance is heat treated and kept warm for 18 hours.

[0146] The marine fluid slip ring forgings prepared in Examples 1-4 of the present invention have a low tendency to crack, almost no cracks on the surface, and are smooth after processing. Figure 3 As shown, the yield rate is high.

[0147] The marine fluid slip ring forgings prepared in Examples 1-4 of the present invention have excellent performance and can meet the use requirements. For example, the tensile strength is 712MPa or more (e.g., 712-746MPa), the yield strength is 465MPa or more (e.g., 465-485MPa), the elongation is 39% or more (e.g., 39%-45%), the area reduction is 76% or more (e.g., 76%-81%), the impact energy (-29°C) is 37J or more (e.g., 37-60J) on average, and the corrosion resistance is ≥720h without breaking.

[0148] The main performance test results of Examples 1-4 are shown in Table 2.

[0149] Table 1 Chemical composition, Wt%

[0150] Serial number C Si Mn Cr Mo Ni Cu V N P S A / F Example 1 0.01 0.44 1.54 22.32 3.11 5.10 0.02 0.03 0.16 0.02 0.01 0.42 Example 2 0.02 0.46 1.55 22.57 3.15 5.03 0.02 0.03 0.18 0.02 0.01 0.44 Example 3 0.01 0.42 1.58 22.45 3.20 5.08 0.03 0.03 0.16 0.02 0.01 0.42 Example 4 0.01 0.45 1.53 22.51 3.10 5.11 0.02 0.03 0.15 0.02 0.01 0.40 Comparative Example 1 0.01 0.44 1.54 22.32 3.11 5.10 0.02 0.03 0.16 0.02 0.01 0.42 Comparative Example 2 0.01 0.46 1.52 22.35 3.14 5.07 0.02 0.03 0.15 0.02 0.01 0.40 Comparative Example 3 0.01 0.44 1.47 22.47 3.17 5.09 0.02 0.03 0.19 0.02 0.01 0.45 Comparative Example 4 0.01 0.43 1.45 22.49 3.49 5.05 0.02 0.03 0.08 0.02 0.01 0.32

[0151] Table 2 Some performance test results

[0152]

[0153]

[0154] The inventor has conducted a large number of experimental studies during the research process, and now uses some solutions with poor performance as comparative examples.

[0155] Comparative Example 1

[0156] This comparative example provides a marine fluid slip ring and a forging method thereof, the components of which are shown in Table 1 above. The difference between the preparation method and Example 1 is that, in step S3: the forging tool is not preheated, resulting in a rapid temperature drop after the forging contacts the upper and lower anvils, the color of the forging surface at the contact point with the upper and lower anvils becomes darker, and cracks appear on the surface during the forging and drawing process.

[0157] The marine fluid slip ring forgings of this comparative example produced many cracks during the forging process, such as Figure 3 shown.

[0158] Comparative Example 2:

[0159] This comparative example provides a marine fluid slip ring and a forging method thereof, the components of which are shown in Table 1 above, and the preparation method is different from that of Example 1 in that:

[0160] In step S4, since the rhythm was not well controlled during the forging process, the temperature drop of the forging was large, resulting in a low final forging temperature after completion, which was actually measured to be 920°C.

[0161] After forging, the marine fluid slip ring of this comparative example has many cracks on the surface of the forging.

[0162] Comparative Example 3

[0163] This comparative example provides a marine fluid slip ring and a forging method thereof, the components of which are shown in Table 1 above, and the preparation method is different from that of Example 1 in that:

[0164] In step S4, during the forging process, the single pressing amount of some passes during the drawing process is large, about 60 mm / time, and in some passes during the drawing process, the deformation rate is fast, exceeding 0.1S -1 After drawing, cracks appeared on the forging surface in many places.

[0165] Comparative Example 4

[0166] This comparative example provides a marine fluid slip ring and a forging method thereof, the components of which are shown in Table 1 above, and the preparation method is different from that of Example 1 in that:

[0167] The A / F ratio in this comparative example is lower than 0.35, and the actual value is 0.32. A / F is too low, which means that the ferrite content is high, resulting in high strength, insufficient toughness, and cracks during forging.

[0168] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A dual-phase steel marine hydraulic slip ring forging, characterized in that: The components of the dual-phase steel marine engineering liquid slip ring forging include, by mass percentage, C: 0.01%-0.03%, Si: 0.30%-0.60%, Mn: 1.0%-1.6%, Cr: 22.0%-23.0%, Mo: 2.5%-3.5%, Ni: 4.5%-6.0%, N: 0.08%-0.20%, Cu: 0.01%-0.04%, V: 0.01%-0.05%, P≤0.025%, S≤0.02%, Sn≤0.01%, As≤0.012%, Sb≤0.004%, and the balance is Fe and inevitable trace impurities.

2. The dual-phase steel marine hydraulic slip ring forging according to claim 1 is characterized in that: A / F is between 0.35 and 0.45, where A=Ni+30(C+N)+0.5Mn, F=Cr+Mo+1.5Si+5V, and Ni, C, N, Mn, Cr, Mo, Si, and V refer to the mass percentages of the elements.

3. The dual-phase steel marine hydraulic slip ring forging according to claim 1, characterized in that: The components of the dual-phase steel marine engineering liquid slip ring forging include, by mass percentage, C: 0.01%-0.025%, Si: 0.40%-0.50%, Mn: 1.3%-1.6%, Cr: 22.1%-22.8%, Mo: 2.8%-3.3%, Ni: 5.0%-5.5%, N: 0.10%-0.20%, Cu: 0.01%-0.03%, V: 0.01%-0.03%, P≤0.025%, S≤0.02%, Sn≤0.01%, As≤0.012%, Sb≤0.004%, and the balance is Fe and inevitable trace impurities.

4. A forging method for a dual-phase steel marine hydraulic slip ring forging according to any one of claims 1 to 3, characterized in that: The steps include: Step S1: Clean the surface of the steel ingot and load it into the furnace; Step S2: subjecting the steel ingot to 4-stage gradient heating and heat preservation; Step S3: preheating the forging tool; Step S4: forging the steel ingot; the initial forging temperature is controlled at 1180°C to 1200°C, and the final forging temperature is controlled at 950°C to 1050°C; Step S5: firstly perform post-forging heat treatment on the forged forging blank, and then perform performance heat treatment.

5. The forging method according to claim 4, characterized in that: In the step S1, the steel ingot is raised by using a shim when being heated, and the height of the shim is greater than 250 mm.

6. The forging method according to claim 4, characterized in that: In step S2, the four-stage gradient heating and heat preservation comprises: S201, slowly heating the steel ingot from room temperature to 300-350°C, and keeping the temperature; S202, slowly heat to 600-650°C, keep warm; S203, heating to 1000-1100°C, keeping warm; S204. Heat to 1150-1200°C and keep warm.

7. The forging method according to claim 6, characterized in that: The heating rates in S203 and S204 are greater than the heating rates in S201 and S202.

8. The forging method according to claim 4, characterized in that: In the step S3, the forging tool is preheated to 150°C to 200°C.

9. The forging method according to claim 4, characterized in that: The post-forging heat treatment comprises: hot delivery and hot loading of the forgings into a furnace after forging, annealing at a temperature of 650-670° C., keeping the temperature for more than 15 hours, and then air cooling to room temperature.

10. The forging method according to any one of claims 4 to 9, characterized in that: The performance heat treatment comprises the following steps: S501, slowly heating the steel ingot from room temperature to 300-350°C, and keeping the temperature; S502, slowly heat to 600-650°C, keep warm; S503. Heat to 1000-1100°C, keep warm, and then water cool to the forging surface temperature <80°C.

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