A steel alloy metal material for shafting and its preparation method and application

Abstract

The present invention belongs to the technical field of low temperature steel, and specifically relates to a steel alloy metal material for shafting, and a preparation method and application thereof. The method comprises the following steps: 1) preparing a steel billet through raw materials according to the composition of the steel alloy metal material for shafting; 2) sequentially forging, hydrogen expansion, heat treatment and oil quenching the steel billet obtained in step 1), and then tempering; 3) annealing the steel material in the temperature range of Ac1 and Ac3, then high temperature tempering, and finally low temperature tempering. The present invention reasonably adds metal elements to the ferroalloy metal material to smelt a ferroalloy material with good fatigue performance. The ferroalloy material can be applied to production environments such as high strength, high hardness, low temperature, and corrosiveness, and has a wide range of applications.

Description

Technical Field

[0001] The invention belongs to the technical field of low-temperature steel, and in particular relates to a steel alloy metal material for a shaft system and a preparation method and application thereof. Background Art

[0002] Material fatigue refers to the behavior of materials that are locally damaged under cyclic loads, and the damage accumulates as the cycle progresses, leading to material failure. In recent decades, accidents caused by material fatigue failure have occurred frequently. Components designed according to traditional conventional design methods are far from meeting the needs of modern industrial development in areas requiring high reliability, which has made people pay more and more attention to the impact of equipment fatigue failure. In addition, with the gradual depletion of conventional exploitable energy, the development and utilization of marine resources has become an inevitable trend in future energy utilization; the polar and deep sea regions have rich energy reserves and are receiving more and more attention. At the same time, with the gradual opening of the Arctic route, the exploitation of marine resources has gradually developed from shallow seas to deep sea areas and polar high-cold areas, which will greatly promote the demand and development of high-ice-class icebreakers.

[0003] The natural conditions in the polar regions are harsh, with challenges such as low temperature tests, sea ice obstacles, iceberg attacks, blizzard attacks, fragile ecological environment, polar night troubles, and poor visibility, which place high demands on the performance of related equipment and materials. The ultra-low temperature environment in the polar regions places demands on key technologies such as low temperature resistance, corrosion resistance, wear resistance, easy welding, and high toughness. According to a 40-year follow-up survey of nearly 700 polar ships by Lloyd's Register of Shipping, 57% of polar ships had cracks or fractures in their hull steel structures after an average age of 13 years. High-ice-grade high-power shafting steel usually uses special low-temperature steel, which must have sufficient low-temperature toughness, strength, fatigue strength and other comprehensive properties. Summary of the invention

[0004] In order to solve the deficiencies of the prior art, the present invention provides a steel alloy metal material for a shaft system and a preparation method and application thereof.

[0005] The technical solution provided by the present invention is as follows:

[0006] A steel alloy metal material for shafting, comprising the following components in mass fractions:

[0007] Carbon 0.3-0.38%;

[0008] Silicon 0.17-0.37%;

[0009] Manganese 0.5-0.8%;

[0010] Chromium 1.3-1.7%;

[0011] Nickel 1.3-1.7%;

[0012] Molybdenum 0.2-0.3%;

[0013] Copper less than or equal to 0.25%;

[0014] Phosphorus less than or equal to 0.025%;

[0015] Sulfur is less than or equal to 0.025%;

[0016] Iron is the balance.

[0017] In the above technical solution:

[0018] The above technical solution adopts the design concept of medium carbon low alloy steel with a carbon content of ≤0.45%. The reduction of carbon can significantly increase the phase transformation temperature, which is beneficial to the formation of acicular ferrite; reducing carbon can effectively reduce segregation to ensure the uniformity of thick sample rod structure and reduce harmful structures caused by later solid-state phase transformation; reducing carbon content increases weldability, which can ensure that no pretreatment and post-treatment are required when welding in cold areas.

[0019] Excessive addition of Mn will lead to the formation of M / A structure caused by Mn segregation in the steel grade, so the Mn content is controlled at 0.5-0.8%.

[0020] Too high Si content is not good for the toughness of the welding heat affected zone, therefore, the Si content in the steel is controlled to ≤0.37%.

[0021] Cr can significantly improve the corrosion resistance of the alloy and form a dense chromium oxide film to protect the alloy surface.

[0022] Ni can increase the low-temperature toughness and strength of the alloy, and improve the corrosion resistance and wear resistance of the alloy.

[0023] Mo and V can significantly improve the strength and hardness of the alloy, and can improve the corrosion resistance of the alloy, and help inhibit intergranular corrosion and stress corrosion cracking.

[0024] The metal material has a yield strength greater than 480 MPa.

[0025] Furthermore, 0.7-0.9% Zr element is added to the alloy, preferably 0.8%, to further improve the fatigue resistance performance.

[0026] Furthermore, 0.11%-0.13% Ti element is added to the alloy, preferably 0.12%, to further improve the fatigue resistance performance.

[0027] The present invention also provides a method for preparing a steel alloy metal material for a shaft system, comprising the following steps:

[0028] 1) preparing a steel billet from raw materials according to the composition of the shaft steel alloy metal material;

[0029] 2) The steel billet obtained in step 1) is subjected to forging, hydrogen expansion, heat treatment and oil quenching in sequence, and then tempering;

[0030] 3) The steel is first annealed in the temperature range of Ac1 to Ac3, then subjected to high temperature tempering, and finally subjected to low temperature tempering.

[0031] In the above technical solution:

[0032] In step 3), annealing treatment is performed in the temperature range between phase transition points Ac1 and Ac3, and then low-temperature tempering treatment is performed to make the structure more uniform and refined.

[0033] In step 3), high temperature tempering makes the retained austenite volume distribution more uniform with moderate stability, thus improving ductility and impact toughness, while additional tempering compensates for the decrease in strength by controlling the secondary precipitation of precipitates.

[0034] In step 3), the lowering of the low temperature tempering temperature increases the tensile strength and yield strength of the experimental steel, and the austenite tempering temperature has a significant effect on the energy absorbed by the impact. In particular, as the austenite heating temperature decreases, the energy absorbed by the impact increases significantly.

[0035] In step 3), after high temperature tempering, the morphology of the tempered carbides precipitated at the boundaries is controlled by the matrix carbon content and the size of the lath martensite substructure. Higher matrix carbon content and boundary density increase the nucleation rate and promote the formation of spherical carbides.

[0036] The quenching and tempering in step 2) and the low-temperature tempering smelting in step 3) improve the cleanliness of the material so as to inhibit the formation of fatigue cracks. At the same time, the micro-alloying method is used to refine the grains of the carburized layer and improve the resistance to fatigue crack initiation and expansion.

[0037] The quenching and tempering in step 2) and the low-temperature tempering heat treatment in step 3) result in a lower content of retained austenite in the surface layer of the sample than in the original sample, and a more uniform distribution, which is conducive to obtaining better fatigue performance.

[0038] In the above steps, the tempering is the annealing treatment and high temperature tempering in step 3).

[0039] Specifically, in step 1), the forging conditions are: forging at a temperature of 840-860°C, preferably at 850°C.

[0040] Forging based on the above conditions can cause the material to undergo plastic deformation to obtain materials with certain mechanical properties, shapes and sizes.

[0041] Specifically, in step 2), the conditions for hydrogen expansion are: keeping warm at a temperature of 650-670° C. for 20-40 minutes, preferably keeping warm at 660° C. for half an hour.

[0042] Hydrogen expansion based on the above conditions can eliminate white spot defects in forgings.

[0043] Specifically, in step 2), the heat treatment conditions are: keeping at 860-880°C for 20-40 minutes, and then quenching by oil cooling. Preferably, keeping at 870°C for half an hour, and then oil cooling to room temperature.

[0044] Heat treatment based on the above conditions can avoid the formation of hardened structure and reduce stress and deformation, obtain certain mechanical properties, and is an effective way to prevent cracks.

[0045] Specifically, in step 2), the tempering treatment conditions are: tempering at a temperature of 570-590° C., keeping the temperature for 1.5-2.5 hours, and then cooling to room temperature. Preferably, keeping the temperature at 580° C. for 2 hours.

[0046] Tempering treatment based on the above conditions can reduce stress and deformation and obtain certain mechanical properties.

[0047] Specifically, in step 3):

[0048] The value of Ac1 is 681-690℃;

[0049] The value of Ac3 is 782-793°C;

[0050] The annealing conditions are: first heating to 840-860°C, keeping warm for 20-40 minutes, then cooling to 740-760°C, keeping warm for 20-40 minutes, performing subcritical annealing, and then water cooling to room temperature. Preferably, first heating to 850°C, keeping warm for 30 minutes, then cooling to 750°C, keeping warm for 30 minutes, performing subcritical annealing, and then water cooling to room temperature.

[0051] Annealing treatment based on the above conditions can improve machinability, eliminate residual stress and stabilize size.

[0052] Specifically, in step 3), the high temperature tempering condition is: keeping the temperature at 590-610° C. for 1.5-2.5 hours. Preferably, keeping the temperature at 580° C. for 2 hours.

[0053] Based on the high temperature return under the above conditions, good comprehensive mechanical properties are obtained.

[0054] Specifically, in step 2), the low temperature tempering condition is: keeping the temperature at 290-310° C. for 20-40 minutes. Preferably, keeping the temperature at 300° C. for half an hour.

[0055] Low temperature tempering based on the above conditions can eliminate the internal stress generated by quenching to obtain the expected mechanical properties.

[0056] The present invention also provides a steel alloy metal material for shafting prepared according to the above preparation method. A micro-laminated microstructure in which ferrite phase and martensite phase are alternately arranged in the thickness direction is found in the steel. Martensite ensures a high tensile strength of the steel, while ferrite ensures good toughness. The alternating arrangement can hinder dislocation, thereby obtaining a better strengthening effect.

[0057] The impact value of 34CrNiMo steel at -10℃ is not less than 27J, and the single impact value is greater than 19J, which meets the industry requirements of the ship industry standard CB / T4312-2013 for ships sailing in ice areas, propeller shafts, rudder shafts (rods) and rudder pintles in low-temperature impact toughness.

[0058] After 180° bending deformation, the specimen of 34CrNiMo steel was intact without any cracks, and had good cold bending plasticity.

[0059] The average Poisson's ratio of 34CrNiMo steel is 0.277, the average Young's modulus is 201.8775 GPa, and the average shear modulus is 79.836 GPa. It has good stiffness and toughness as well as resistance to shear deformation.

[0060] The present invention also provides the application of the steel alloy metal material for shafting as the steel for shafting working in low temperature environment.

[0061] The beneficial effects of the present invention are:

[0062] The ferroalloy material of the present invention reasonably adds metal elements to smelt a ferroalloy material with good fatigue performance. The ferroalloy material can be applied to production environments with high strength, high hardness, low temperature, corrosion, etc. and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 This is a surface microscopic morphology diagram of the 34CrNiMo metal material provided for implementation 1 of the present invention.

[0064] Figure 2 This is a SEM image of the 34CrNiMo metal material provided in embodiment 1 of the present invention.

[0065] Figure 3 The fatigue performance test results of the 34CrNiMo metal material provided in embodiment 1 of the present invention.

[0066] Figure 4 The CCT diagram of the 34CrNiMo metal material provided in embodiment 1 of the present invention.

[0067] Figure 5 The TTT diagram of the 34CrNiMo metal material provided in embodiment 1 of the present invention.

[0068] Figure 6 It is a heat treatment process diagram for implementation 1 of the present invention. DETAILED DESCRIPTION

[0069] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0070] Example 1

[0071] The chemical composition and weight percentage are: carbon 0.36%; silicon 0.27%; manganese 0.59%; chromium 1.63%; nickel 1.59%; molybdenum 0.25%; copper 0.10%; phosphorus 0.003%; sulfur 0.005%; iron is the balance.

[0072] The preparation method is as follows:

[0073] 1) preparing a steel billet from raw materials according to the composition of the shaft steel alloy metal material;

[0074] 2) The steel billet obtained in step 1) is subjected to forging, hydrogen expansion, heat treatment and oil quenching in sequence, and then tempering;

[0075] 3) The steel is first annealed in the temperature range of Ac1 to Ac3, then subjected to high temperature tempering, and finally subjected to low temperature tempering.

[0076] In step 2), the forging conditions are: forging at 850°C.

[0077] In step 2), the conditions for hydrogen expansion are: keeping the temperature at about 660° C. for half an hour.

[0078] In step 2), the heat treatment conditions are: keeping at 870° C. for half an hour, and then quenching by oil cooling.

[0079] In step 2), the tempering treatment conditions are: tempering at 580° C. and keeping the temperature for two hours.

[0080] In step 3), the value of Ac1 is 690°C; the value of Ac3 is 793°C; the annealing conditions are: firstly heat to 850°C, keep warm for 30 minutes, then cool to 740°C, keep warm for 30 minutes, perform subcritical annealing, and then water cool to room temperature.

[0081] In step 3), the high temperature tempering condition is: keeping at 600° C. for 2 hours.

[0082] In step 3), the low temperature tempering condition is: keeping the temperature at 300° C. for half an hour.

[0083] Heat treatment process such as Figure 6 shown.

[0084] The measured performance data are as follows:

[0085]

[0086]

[0087] Example 2

[0088] The chemical composition and weight percentage are: carbon 0.34%; silicon 0.26%; manganese 0.58%; chromium 1.61%; nickel 1.57%; molybdenum 0.25%; copper 0.10%; phosphorus 0.003%; sulfur 0.005%; iron is the balance.

[0089] The preparation method is as follows:

[0090] 1) preparing a steel billet from raw materials according to the composition of the shaft steel alloy metal material;

[0091] 2) The steel billet obtained in step 1) is subjected to forging, hydrogen expansion, heat treatment and oil quenching in sequence, and then tempering;

[0092] 3) The steel is first annealed in the temperature range of Ac1 to Ac3, then subjected to high temperature tempering, and finally subjected to low temperature tempering.

[0093] In step 2), the forging conditions are: forging at 850°C.

[0094] In step 2), the conditions for hydrogen expansion are: keeping the temperature at about 660° C. for half an hour.

[0095] In step 2), the heat treatment conditions are: keeping at 870° C. for half an hour, and then quenching by oil cooling.

[0096] In step 2), the tempering treatment conditions are: tempering at 580° C. and keeping the temperature for two hours.

[0097] In step 3), the value of Ac1 is 688°C; the value of Ac3 is 791°C; the annealing conditions are: first heat to 850°C, keep warm for 30 minutes, then cool to 750°C, keep warm for 30 minutes, perform subcritical annealing, and then water cool to room temperature.

[0098] In step 3), the high temperature tempering condition is: keeping at 600° C. for 2 hours.

[0099] In step 3), the low temperature tempering condition is: keeping the temperature at 300° C. for half an hour.

[0100] The measured performance data are as follows:

[0101]

[0102]

[0103] Example 3

[0104] The chemical composition and weight percentage are: carbon 0.32%; silicon 0.25%; manganese 0.57%; chromium 1.59%; nickel 1.55%; molybdenum 0.25%; copper 0.10%; phosphorus 0.003%; sulfur 0.005%; iron is the balance.

[0105] The preparation method is as follows:

[0106] 1) preparing a steel billet from raw materials according to the composition of the shaft steel alloy metal material;

[0107] 2) The steel billet obtained in step 1) is subjected to forging, hydrogen expansion, heat treatment and oil quenching in sequence, and then tempering;

[0108] 3) The steel is first annealed in the temperature range of Ac1 to Ac3, then subjected to high temperature tempering, and finally subjected to low temperature tempering.

[0109] In step 2), the forging conditions are: forging at 850°C.

[0110] In step 2), the conditions for hydrogen expansion are: keeping the temperature at about 660° C. for half an hour.

[0111] In step 2), the heat treatment conditions are: keeping at 870° C. for half an hour, and then quenching by oil cooling.

[0112] In step 2), the tempering treatment conditions are: tempering at 580° C. and keeping the temperature for two hours.

[0113] In step 3), the value of Ac1 is 681°C; the value of Ac3 is 782°C; the annealing conditions are: firstly heat to 850°C, keep warm for 30 minutes, then cool to 750°C, keep warm for 30 minutes, perform subcritical annealing, and then water cool to room temperature.

[0114] In step 3), the high temperature tempering condition is: keeping at 600° C. for 2 hours.

[0115] In step 3), the low temperature tempering condition is: keeping the temperature at 300° C. for half an hour.

[0116] The measured performance data are as follows:

[0117]

[0118]

[0119] The above embodiments adopt the design concept of medium carbon alloy steel, which can effectively reduce segregation to ensure the uniformity of thick sample rod structure and reduce harmful structures caused by late solid phase transformation; the carbon content is reduced and the weldability is increased, which can ensure that no pretreatment and post-treatment are required when welding in cold areas. The addition of manganese can make up for the loss of strengthening effect caused by reducing carbon, but excessive addition of manganese will cause the generation of M / A structure caused by manganese segregation in steel, so the addition of manganese should not be too high. Si is a commonly used deoxidation and alloying element in steel. Too high Si content is not good for the toughness of the welding heat affected zone. Therefore, the Si in the steel is controlled to ≤0.37%. At the same time, different heat treatments on this basis can also have different effects on it. High-temperature intercritical annealing accelerates the dissolution of cementite particles, promotes the formation of reduced austenite, and then increases the total elongation and impact energy. The dense precipitation of precipitates in martensite is promoted in additional tempering. The precipitates are fine, uniform in size, high in density, and have a significant strengthening effect. Strengthening compensates for the softening of high-temperature annealing, so that the yield strength of steel is improved. The maximum stress range of axial cyclic load before heat treatment was 450MPa~550MPa, and the stress range increased to 700MPa~800MPa after heat treatment. The fatigue stress of the heat treated specimens exceeded 10 7 The fatigue specimens were subjected to cycles without fracture. The cycle period of the fatigue specimens at the stress level of 700MPa to 750MPa was close to 10 7 The specimen was subjected to cycles without fracture. When the stress level reached 800 MPa, the cycle period of the specimen showed a significant downward trend, and the fatigue life at this time was still more than 10 5 The fatigue strength of the heat-treated 34CrNiMo alloy was significantly improved after the heat treatment.

[0120] By comparing the examples, it can be seen that the cycle period of the fatigue specimen at the stress level of 700MPa to 750MPa is close to 10 7 The specimen was subjected to cycles without fracture. When the stress level reached 800 MPa, the cycle period of the specimen showed a significant downward trend, and the fatigue life at this time was still more than 10 5 The fatigue strength of the heat-treated 34CrNiMo alloy was significantly improved after the heat treatment.

[0121] Figure 1This is a surface microscopic morphology of the 34CrNiMo metal material provided in Embodiment 1 of the present invention. As can be seen from the figure, the microstructure is a composite structure of ferrite and pearlite, the black area in the figure is the pearlite structure, and the white area is the polygonal ferrite structure.

[0122] Figure 2 This is a SEM image of the 34CrNiMo metal material provided for implementation 1 of the present invention. It can be seen from the image that there is a small amount of segregation structure.

[0123] Figure 3 The fatigue performance test results of 34CrNiMo metal material provided for the embodiment 1 of the present invention are shown in the figure. It can be seen from the figure that the maximum stress range of axial cyclic load before heat treatment is 450MPa-550MPa, and the stress range increases to 700MPa-800MPa after heat treatment.

[0124] Figure 4 The CCT diagram of the 34CrNiMo metal material provided for implementation 1 of the present invention. It can be seen from the figure that the final microstructures obtained at different cooling rates are different. When the cooling rate is fast (100K / s-10K / s), martensite and bainite are generated. When the cooling rate is moderate (10K / s-1K / s), in addition to martensite and bainite, a small amount of pearlite is also generated. When the cooling rate is slow (1K / s-0.1K / s), more types of microstructures are generated, and in addition to the above-mentioned microstructures, ferrite is also generated.

[0125] Figure 5 The TTT diagram of the 34CrNiMo metal material provided for the embodiment 1 of the present invention. It can be seen from the figure that different phase changes will occur in different temperature ranges. Pearlite transformation occurs in the range of 1033.6℃-1017℃, and the transformation product is mainly pearlite structure; in the range of 1017℃-812.4℃, not only pearlite transformation occurs, but also austenite to ferrite transformation occurs; in the range of 812.4℃-588.4℃, bainite transformation occurs, and a large amount of bainite structure will be generated; in the range of 588.4℃-469.7℃, martensite transformation occurs.

[0126] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a steel alloy metal material for a shaft system, characterized in that: The following steps are involved: 1) According to the composition of the shaft steel alloy metal material, prepare the steel billet from the raw materials; 2) The steel billet obtained in step 1) is subjected to forging, hydrogen expansion, heat treatment and oil quenching in sequence, and then tempering; 3) The steel is first annealed, then tempered at high temperature, and finally tempered at low temperature; The shaft steel alloy metal material includes the following components in mass fraction: Carbon 0.3-0.38%; Silicon 0.17-0.37%; Manganese 0.5-0.8%; Chromium 1.3-1.7%; Nickel 1.3-1.7%; Molybdenum 0.2-0.3%; Copper less than or equal to 0.25%; Phosphorus less than or equal to 0.025%; Sulfur less than or equal to 0.025% Iron is the balance; In step 3): The annealing conditions are: first heating to 840-860°C, keeping warm for 20-40 minutes, then cooling to 740-760°C, keeping warm for 20-40 minutes, and then water cooling to room temperature; The conditions for high temperature tempering are: keeping at 590-610℃ for 1.5-2.5 hours; The conditions for low temperature tempering are: keeping warm at 290-310℃ for 20-40 minutes.

2. The method for preparing the steel alloy metal material for shafting according to claim 1, characterized in that: In step 2), the forging conditions are: forging at a temperature of 840-860°C.

3. The method for preparing the steel alloy metal material for shafting according to claim 1, characterized in that: In step 2), the conditions for hydrogen expansion are: keeping the temperature at 650-670°C for 20-40 minutes.

4. The method for preparing the steel alloy metal material for shafting according to claim 1, characterized in that: In step 2), the heat treatment conditions are: keeping at a temperature of 860-880° C. for 20-40 minutes, and then quenching by oil cooling.

5. The method for preparing the steel alloy metal material for shafting according to claim 1, characterized in that: In step 2), the tempering treatment conditions are: tempering at a temperature of 570-590° C., keeping the temperature for 1.5-2.5 hours, and then cooling to room temperature.

6. A steel alloy metal material for shafting prepared according to the preparation method according to any one of claims 1 to 5.

7. An application of the steel alloy metal material for shafting according to claim 6, characterized in that: Used as shaft steel for working in low temperature environment.

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