A ship shaft material and its post-forging heat treatment process

Abstract

The invention discloses a ship shaft material and a post-forging heat treatment process thereof, comprising the following steps: after mixing the ship shaft materials in proportion and forging and forming, immediately blowing air to cool the ship shaft surface temperature to 250-350°C, then loading the material into a furnace and performing a first heat preservation treatment; after the heat preservation treatment is completed, heating the material to 900-930°C and performing a second heat preservation treatment; after the second heat preservation treatment is completed, cooling the material to 250-350°C by air cooling and performing a third heat preservation treatment; after the third heat preservation treatment is completed, heating the material to 820-860°C and performing a fourth heat preservation treatment; after the fourth heat preservation treatment is completed, cooling the material to 250-350°C by oil cooling and performing a fifth heat preservation treatment; after the fifth heat preservation treatment is completed, heating the material to 550-600°C and performing a sixth heat preservation treatment; after the sixth heat preservation treatment is completed, cooling the material out of the furnace.

Description

Technical Field

[0001] The invention relates to the technical field of large forging preparation, in particular to a ship shaft material and a post-forging heat treatment process thereof. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The ship shaft is one of the most important parts of large ships. Its function is to carry the weight of the entire ship while taking into account the task of ship power transmission. It is an important part of the ship's power plant. It is mainly composed of large forgings such as thrust shafts, intermediate shafts, propeller shafts, and stern shafts. Such products are collectively referred to as ship shaft forgings. The characteristics of such forging products are: a large flange is contained at one end or both ends or in the middle of the shaft body, and the diameter difference between the shaft body and the flange is large. At the same time, the length is large, generally more than 7-8 meters, and even more than 13 meters. The material of the ship shaft is generally C45E, 45Mn-like carbon manganese steel. With the development of ocean-going ships, the specifications and sizes of ship shaft forgings are getting larger and larger, and the required steel ingots are constantly increasing. The carbon manganese steel material is essentially easy to coarse-grained steel. At the same time, the Mn element also aggravates the segregation degree of the steel ingot, especially the C element. The C segregation in the center of the steel ingot can even reach more than 14%, and the C content in the center of the riser is about 0.55%. After the forging of the ship shaft forging is completed, when the surface final forging temperature is 750℃, the center temperature is still high, which causes the central grain to grow rapidly at a higher temperature, resulting in coarse grains and mixed grains, affecting the flaw detection effect and mechanical properties of the forging. In addition, in the actual production process, multiple austenitization treatments are required during the post-forging heat treatment, generally 4-5 times of conventional normalizing, which increases energy consumption and prolongs the production cycle. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention aims to provide a ship axle material and a post-forging heat treatment process thereof.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] In a first aspect, the present invention provides a ship axle material, consisting of the following components: C 0.4-0.45%, Si 0.2-0.4%, Mn 1-1.2%, P≤0.01%, S≤0.005%, Cr0.25-0.35%, Mo 0.1-0.15%, Ni≤0.4%, Al 0.015-0.025%, Nb0.015-0.06%, Zr, and the remainder is Fe and unavoidable impurities.

[0007] Compared with traditional materials, the content of C and Mn elements is controlled to reduce the coarse grain and segregation degree of the material; a small amount of Cr and Mo elements are added to improve the hardenability and mechanical properties of the material; trace amounts of Al and Nb elements are added to effectively control the grain size of the forgings and the purity of the molten steel.

[0008] In some embodiments, in the ship shaft material, the mass percentage of Al is 0.015-0.02%.

[0009] In some embodiments, in the ship shaft material, the mass percentage of Nb is 0.02-0.05%.

[0010] In a second aspect, the present invention provides a post-forging heat treatment process for the ship shaft material, comprising the following steps:

[0011] After the ship shaft material is melted and poured into steel ingots according to proportion and forged into shape, it is immediately cooled by air (to quickly reduce the internal temperature of the ship shaft) until the surface temperature of the ship shaft reaches 250-350℃, then loaded into the furnace for material waiting, and the first insulation treatment is carried out;

[0012] After the heat preservation treatment is completed, the temperature is raised to 900-930℃ for the second heat preservation treatment;

[0013] After the second heat preservation treatment, the steel is cooled to 250-350℃ by air cooling and then the third heat preservation treatment is carried out;

[0014] After the third heat preservation treatment, the temperature is raised to 820-860°C for the fourth heat preservation treatment;

[0015] After the fourth heat preservation treatment, oil cooling (ordinary engine oil can be used. The purpose of oil cooling here is to increase the cooling speed and increase the low-temperature transformation structure, thereby improving the mechanical properties. Compared with air cooling, oil cooling is faster and safer than water cooling) to 250-350℃, and then the fifth heat preservation treatment is carried out;

[0016] After the fifth heat preservation treatment, the temperature is raised to 550-600°C for the sixth heat preservation treatment;

[0017] After the sixth heat preservation treatment, cool and take out of the oven.

[0018] In some embodiments, the time of the first insulation treatment is T×t1 / 0.1, wherein T is the wall thickness of the ship shaft, in m, and t1 is 0.5-1h.

[0019] In some embodiments, the time of the second insulation treatment is T×t2 / 0.1, wherein T is the wall thickness of the ship axle, in m, and t2 is 0.5-2h.

[0020] In some embodiments, the time of the third insulation treatment is T×t3 / 0.1, wherein T is the wall thickness of the ship axle, in m, and t3 is 0.5-1h.

[0021] In some embodiments, the time of the fourth insulation treatment is T×t4 / 0.1, wherein T is the wall thickness of the ship axle, in m, and t4 is 1-3h.

[0022] In some embodiments, the time of the fifth insulation treatment is T×t5 / 0.1, wherein T is the wall thickness of the ship shaft, in m, and t5 is 0.5-1h.

[0023] In some embodiments, the time of the sixth insulation treatment is T×t6 / 0.1, wherein T is the wall thickness of the ship axle, in m, and t6 is 2-4h.

[0024] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0025] The present invention uses Al and Nb element microalloying treatment, adopts a special post-forging heat treatment process of one high-temperature normalizing and one low-temperature normalizing, and uses air cooling and oil cooling for cooling, which effectively refines the grain size of the ship shaft, improves the mechanical properties of the ship shaft, reduces the number of normalizing times after forging, avoids energy waste, and saves production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 is a simplified structural diagram of the ship shaft in Embodiment 1 of the present invention;

[0028] Figure 2 This is a metallographic photograph of a ship shaft manufactured by Example 1 of the present invention;

[0029] Figure 3 This is a metallographic photograph of a ship shaft manufactured using conventional materials and methods of Comparative Example 1. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0031] The present invention will be further described below in conjunction with the embodiments.

[0032] Example 1

[0033] A ship shaft material and a post-forging heat treatment method thereof include the following steps:

[0034] Based on the total mass of the raw material components of the ship axle material, the ship axle material includes the following raw material components: C 0.45%, Si 0.20%, Mn 1.20%, P 0.008%, S 0.002%, Cr 0.25%, Mo 0.15%, Ni 0.2%, Al 0.015%, Nb 0.02%, and the balance is Fe and unavoidable impurities, and % is mass percentage.

[0035] The heat treatment method of ship axle after forging includes the following processes:

[0036] After the ship shaft is forged, it is immediately cooled by air to a temperature of 300℃ on the surface of the ship shaft, then loaded into the furnace for material and heat-insulated. The heat-insulation treatment is performed for 1 hour for every 100mm wall thickness.

[0037] Then raise the temperature to 900℃ and keep it warm for 0.5h for every 100mm wall thickness.

[0038] After the insulation is completed, the system is cooled by air to 250℃ and then heat-insulated for 1 hour for every 100mm wall thickness.

[0039] After the insulation is completed, the temperature is raised to 820℃ and the insulation treatment is carried out for 3 hours for every 100mm wall thickness.

[0040] After the insulation is completed, oil is added for oil cooling, and the temperature is cooled to 350℃. Then the steel is loaded into the furnace and kept at 350℃ for 0.5h for every 100mm wall thickness.

[0041] After the insulation is completed, the temperature is raised to 550℃ and insulation treatment is carried out for 4 hours for every 100mm wall thickness.

[0042] After the insulation is completed, the furnace is cooled to below 300℃ and then taken out of the furnace.

[0043] The ship shaft products obtained by using the above ship shaft materials and heat treatment methods were subjected to organizational morphology analysis and performance testing. The specific performance is shown in Table 1, and the metallographic photos are shown in Figure 2 ,Depend on Figure 2 It can be seen that the grain size of the ship axle made by this embodiment reaches above level 6.

[0044] Table 1 Mechanical properties test data of the ship shaft product prepared in Example 1

[0045]

[0046] Example 2

[0047] Based on the total mass of the raw material components of the ship axle material, the ship axle material includes the following raw material components: C 0.40%, Si 0.3%, Mn 1.20%, P 0.005%, S 0.001%, Cr 0.35%, Mo 0.13%, Ni 0.1%, Al 0.015%, Nb 0.02%, and the balance is Fe and unavoidable impurities, and % is mass percentage.

[0048] The heat treatment method of ship axle after forging includes the following processes:

[0049] After the ship shaft is forged, it is immediately cooled by blowing until the surface temperature of the ship shaft reaches 250℃, then loaded into the furnace to wait for the material and subjected to insulation treatment; insulation is performed for 0.5h for every 100mm wall thickness.

[0050] Then raise the temperature to 930℃ and keep it warm for 2h for every 100mm wall thickness.

[0051] After the insulation is completed, it is cooled by blowing air to 350℃ and then heat-insulated for 0.5h for every 100mm wall thickness.

[0052] After the insulation is completed, the temperature is raised to 860℃ and the insulation treatment is carried out for 3 hours for every 100mm wall thickness.

[0053] After the insulation is completed, oil is added for oil cooling, and the oil cooling is performed to 300℃. Then the steel is loaded into the furnace and kept at 300℃ for 1h for every 100mm wall thickness.

[0054] After the insulation is completed, the temperature is raised to 550℃ and insulation treatment is carried out for 3 hours for every 100mm wall thickness.

[0055] After the insulation is completed, the furnace is cooled to below 300℃ and then taken out of the furnace.

[0056] Table 2 Mechanical properties test data of the ship shaft product prepared in Example 2

[0057]

[0058] Example 3

[0059] Based on the total mass of the raw material components of the ship axle material, the ship axle material includes the following raw material components: C 0.42%, Si 0.30%, Mn 1.10%, P 0.001%, S 0.001%, Cr 0.25%, Mo 0.10%, Ni 0.2%, Al 0.025%, Nb 0.04%, and the balance is Fe and unavoidable impurities, and % is mass percentage.

[0060] The heat treatment method of ship axle after forging includes the following processes:

[0061] After the ship shaft is forged, it is immediately cooled by blowing until the surface temperature of the ship shaft reaches 350℃, then loaded into the furnace to wait for the material and subjected to heat preservation treatment; the insulation time is 0.7h for every 100mm wall thickness.

[0062] Then raise the temperature to 930℃ and keep it warm for 2h for every 100mm wall thickness.

[0063] After the insulation is completed, it is cooled by blowing air to 350℃ and then heat-insulated for 0.5h for every 100mm wall thickness.

[0064] After the insulation is completed, the temperature is raised to 860℃ and the insulation treatment is carried out for 2 hours for every 100mm wall thickness.

[0065] After the insulation is completed, put it into oil for oil cooling, oil cooling to 250℃, then put it into the furnace and keep it at 250℃ for 0.5h for every 100mm wall thickness.

[0066] After the insulation is completed, the temperature is raised to 600℃ and insulation treatment is carried out for 4 hours for every 100mm wall thickness.

[0067] After the insulation is completed, the furnace is cooled to below 300℃ and then taken out of the furnace.

[0068] Table 3 Mechanical properties test data of the ship shaft product prepared in Example 3

[0069]

[0070] Comparative Example 1

[0071] The traditional ship shaft material is 45Mn. After forging, it is air-cooled to a surface temperature of 400℃ and then loaded into a furnace for waiting and isothermal treatment. It is then normalized twice at 870℃. The cooling is done by air cooling and then loaded into a furnace for tempering to make a traditional ship shaft.

[0072] The grain size analysis and post-forging performance test of the conventional ship shaft are carried out. The specific performances are shown in Table 4 and the metallographic photos are shown in Table 4. Figure 3 The grain size is 4-5 and part is 1-2, with serious mixed crystal phenomenon, and 2-3 more normalizing are required to complete grain refinement.

[0073] Table 4 Mechanical properties test data of the ship shaft product prepared in Comparative Example 1

[0074]

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A ship shaft material, characterized in that: It is composed of the following components: C 0.4-0.45%, Si 0.2-0.4%, Mn 1-1.2%, P≤0.01%, S≤0.005%, Cr 0.25-0.35%, Mo0.1-0.15%, Ni≤0.4%, Al0.015-0.025%, Nb 0.015-0.06%, and the balance is Fe and unavoidable impurities; The post-forging heat treatment process of the ship shaft material comprises the following steps: After the ship shaft material is melted and poured into steel ingots according to proportion and forged into shape, it is immediately cooled by blowing air until the surface temperature of the ship shaft reaches 250-350℃, and then loaded into the furnace for the first insulation treatment; After the heat preservation treatment is completed, the temperature is raised to 900-930℃ for the second heat preservation treatment; After the second heat preservation treatment, the steel is cooled to 250-350℃ by air cooling and then the third heat preservation treatment is carried out; After the third heat preservation treatment, the temperature is raised to 820-860°C for the fourth heat preservation treatment; After the fourth heat preservation treatment, the oil is cooled to 250-350°C, and then the fifth heat preservation treatment is carried out; After the fifth heat preservation treatment, the temperature is raised to 550-600°C for the sixth heat preservation treatment; After the sixth heat preservation treatment, cool and take out of the oven.

2. The ship shaft material according to claim 1, characterized in that: The mass percentage of Al is 0.015-0.02%.

3. The ship shaft material according to claim 1, characterized in that: In the ship shaft material, the mass percentage of Nb is 0.02-0.05%.

4. The post-forging heat treatment process of the ship shaft material according to any one of claims 1 to 3, characterized in that: The steps include: After the ship shaft material is melted and poured into steel ingots according to proportion and forged into shape, it is immediately cooled by blowing air until the surface temperature of the ship shaft reaches 250-350℃, and then loaded into the furnace for the first insulation treatment; After the heat preservation treatment is completed, the temperature is raised to 900-930℃ for the second heat preservation treatment; After the second heat preservation treatment, the steel is cooled to 250-350℃ by air cooling and then the third heat preservation treatment is carried out; After the third heat preservation treatment, the temperature is raised to 820-860°C for the fourth heat preservation treatment; After the fourth heat preservation treatment, the oil is cooled to 250-350°C, and then the fifth heat preservation treatment is carried out; After the fifth heat preservation treatment, the temperature is raised to 550-600°C for the sixth heat preservation treatment; After the sixth heat preservation treatment, cool and take out of the oven.

5. The post-forging heat treatment process for ship shaft material according to claim 4 is characterized in that: The time for the first insulation treatment is T×t1 / 0.1, where T is the wall thickness of the ship shaft, in m, and t1 is 0.5-1h.

6. The post-forging heat treatment process for ship shaft material according to claim 4, characterized in that: The time for the second insulation treatment is T×t2 / 0.1, where T is the wall thickness of the ship shaft, in m, and t2 is 0.5-2h.

7. The post-forging heat treatment process for ship shaft material according to claim 4 is characterized in that: The time for the third insulation treatment is T×t3 / 0.1, where T is the wall thickness of the ship shaft, in m, and t3 is 0.5-1h.

8. The post-forging heat treatment process for ship shaft material according to claim 4 is characterized in that: The time for the fourth insulation treatment is T×t4 / 0.1, where T is the wall thickness of the ship shaft, in m, and t4 is 1-3h.

9. The post-forging heat treatment process for ship shaft material according to claim 4, characterized in that: The time for the fifth insulation treatment is T×t5 / 0.1, where T is the wall thickness of the ship shaft, in m, and t5 is 0.5-1h.

10. The post-forging heat treatment process for ship shaft material according to claim 4, characterized in that: The time for the sixth insulation treatment is T×t6 / 0.1, where T is the wall thickness of the ship shaft, in m, and t6 is 2-4h.

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