阅读说明：本技术 一种船用舵系高强度锻件锻造及热处理工艺 (Forging and heat treatment process for high-strength forging of marine rudder system ) 是由 张晶 于 2021-06-29 设计创作，主要内容包括：本发明公开了一种船用舵系高强度锻件锻造及热处理工艺,其技术方案要点是包括以下步骤：S1：对原材料进行熔炼；S2：原材料锻造加热,得到钢锭；S3：锻造,得到锻件；钢锭锻造包括三个火次；S4：锻件热处理；S5、对锻件进行调质处理,本发明具有产品强度和韧性高、良好的冷热变形能力和优良的性能稳定性,使用寿命长的优点。(The invention discloses a forging and heat treatment process of a high-strength forging of a marine rudder system, which has the technical scheme main points that the forging and heat treatment process comprises the following steps: s1: smelting the raw materials; s2: forging and heating the raw materials to obtain a steel ingot; s3: forging to obtain a forged piece; the steel ingot forging comprises three heating times; s4: carrying out heat treatment on the forged piece; s5, quenching and tempering are carried out on the forged piece, and the invention has the advantages of high product strength and toughness, good cold and hot deformation capability, excellent performance stability and long service life.)

1. A marine rudder system high-strength forging and heat treatment process is characterized by comprising the following steps:

s1: smelting the raw materials;

s2: forging and heating the raw materials to obtain a steel ingot;

s3: forging to obtain a forged piece; the steel ingot forging comprises three heating times:

(1) the first fire time: the steel ingot is sequentially drawn out and upset, and the forging temperature is 1180-1205 ℃;

(2) the second fire time: the steel ingot is sequentially drawn out and upset and formed, and the forging temperature is 1180-1200 ℃;

(3) the third fire time: drawing and forming the steel ingot, wherein the forging temperature is 1150-1180 ℃;

s4: heat treating a forging, comprising:

(1) air cooling treatment after forging: placing the forging in air for cooling; (ii) a

(2) Normalizing and tempering the forging: 1. the forging piece is sent into a furnace for normalizing and heat preservation, the normalizing temperature is 920-930 ℃, the heat preservation time is positively correlated with the thickness of the forging piece, and the heat preservation time is 1.5-1.7 min for each 1mm of the forging piece; after the heat preservation is finished, discharging from the furnace, air cooling the forge piece, and after the air cooling is less than 500 ℃, feeding into the furnace for tempering; 2. feeding the forge piece into a furnace for tempering and heat preservation, wherein the tempering temperature is 660-680 ℃, the heat preservation time is positively correlated with the thickness of the forge piece, and the heat preservation time is 2.3-2.5 min for each 1mm of forge piece; cooling the forgings to below 400 ℃ along with the furnace after heat preservation is finished, discharging the forgings out of the furnace and air cooling the forgings;

(3) roughly machining a forged piece;

s5, quenching and tempering the forging, including:

(1) quenching the forged piece: putting a forged piece into a furnace for heating, preserving heat at the quenching temperature of 910-920 ℃, discharging the forged piece out of the furnace after heat preservation is finished, and putting the forged piece into a water-soluble medium pool for cooling;

(2) primary tempering: heating the forge piece in a furnace, preserving heat at the tempering temperature of 530-550 ℃, cooling the forge piece to below 400 ℃ along with the furnace after heat preservation is finished, and then discharging the forge piece from the furnace and air-cooling to room temperature;

(3) secondary tempering: and (3) heating the forge piece in a furnace, preserving heat at the tempering temperature of 500-530 ℃, cooling the forge piece to below 400 ℃ along with the furnace after heat preservation is finished, and then discharging the forge piece from the furnace and air-cooling to room temperature.

2. The marine rudder system high-strength forging and heat treatment process according to claim 1, characterized in that: the forging comprises the following chemical elements in percentage by weight: c: 0.13 to 0.19%, Mn: 0.3-0.6%, P: not more than 0.020%, S not more than 0.020%, Si: less than or equal to 0.17-0.37 percent, Cr: 1.35-1.65%, Ni: 4.0-4.5%, W: 0.8 to 1.2 percent; cu: less than or equal to 0.20 percent, and the balance of Fe and impurities.

3. The marine rudder system high-strength forging and heat treatment process according to claim 1, characterized in that: the step S2 specifically includes: (1) charging; the charging temperature is less than or equal to 400 ℃; (2) heating; heating at 400-800 ℃ at the heating speed of less than or equal to 100 ℃/h; (3) preserving heat; carrying out heat preservation by stages, wherein the heat preservation temperature of the first stage is 850 ℃; the second stage heat preservation temperature is 1200 ℃; the heat preservation time of each heat preservation stage is positively correlated with the thickness of the steel ingot, and the heat preservation time of each steel ingot with the thickness of 200mm is 1.2-1.5 hours.

4. The marine rudder system high-strength forging and heat treatment process according to claim 1, characterized in that: in the first heating time of the step S3, the finish forging temperature of the steel ingot is more than or equal to 900 ℃, and after the first heating time is finished, the steel ingot is placed into a forging heating furnace to be heated, wherein the heating temperature is 1180-1200 ℃; the heating time is positively correlated with the thickness of the steel ingot, and the steel ingot with the thickness of 200mm is heated for 1.2-1.5 hours.

5. The marine rudder system high-strength forging and heat treatment process according to claim 1, characterized in that: in the second firing of the step S3, the finish forging temperature is more than or equal to 900 ℃; after the second firing, putting the steel ingot into a forging heating furnace for heating, wherein the heating temperature is 1150-1180 ℃; the heating time is positively correlated with the thickness of the steel ingot, and the steel ingot with the thickness of 200mm is heated for 1.2-1.5 hours.

6. The marine rudder system high-strength forging and heat treatment process according to claim 1, characterized in that: in the third firing of the step S3, the finish forging temperature is more than or equal to 900 ℃; and after the third firing, cooling the forge piece in air to 600 ℃ and then putting the forge piece into a furnace for post-forging heat treatment.

7. The marine rudder system high-strength forging and heat treatment process according to claim 1, characterized in that: in the first fire of step S3, the total draft ratio is > 2.2; the total upsetting ratio is more than 2.2; in the second fire, the total drawing length ratio is more than 2.2, and the total upsetting ratio is more than 2.2; in the third fire, the total draw ratio is greater than 2.2.

8. The marine rudder system high-strength forging and heat treatment process according to claim 1, characterized in that: in the normalizing and tempering treatment of step S4: loading the forging into a furnace for tempering at the temperature of 500-600 ℃; and (3) loading the forge piece into a furnace and tempering at the temperature of 680 ℃.

9. The marine rudder system high-strength forging and heat treatment process according to claim 1, characterized in that: in step S5: 1. in quenching, the heat preservation time is positively correlated with the thickness of the forged piece, and the heat preservation time is 1.5-1.7 min for each forged piece with the thickness of 1 mm; 2. in primary tempering, the heat preservation time is positively correlated with the thickness of the forge piece, and the heat preservation time is 2.3-2.5 min for each forge piece with the thickness of 1 mm; 3. in secondary tempering, the heat preservation time is positively correlated with the thickness of the forged piece, and the heat preservation time of the forged piece with the thickness of 1mm is 2.3-2.5 min.

10. The marine rudder system high-strength forging and heat treatment process according to claim 1, characterized in that: in step S5: 1. in the quenching process, the quenching heat preservation temperature is 910 ℃, the cooling temperature is less than 40 ℃, and then the quenching process is carried out in a furnace for tempering, wherein the repetition times of the quenching process is less than or equal to 2; 2. in primary tempering, the tempering heat preservation temperature is 540 ℃; 2. in the secondary tempering, the tempering heat preservation temperature is 500 ℃.

Technical Field

The invention relates to the field of forging heat treatment processes, in particular to a forging and heat treatment process of a high-strength forging of a marine rudder system.

Background

The 18Cr2Ni4W is a common alloy carburizing steel for high-strength steel, has high strength, toughness and hardenability, can be used under the condition of quenching and tempering without carburizing, and is generally used as an important part with larger section, higher load, good toughness and low notch sensitivity. With the rapid development of the construction level of special ships in China, the requirements on the functionality of the ships are more and more. Because the material has high strength, wear resistance and good hardenability. Therefore, the application of the steel in the field of marine forgings is more and more extensive. As the sea is a special environment with high salt and high humidity, the performance requirements for the forgings are more severe.

However, the conventional materials have the following problems: the material has poor thermal conductivity and large linear expansion coefficient, so the forging performance is poor, the overheating sensitivity is high, crystal grains can be quickly coarsened when the forging process is improperly controlled, and the later-stage heat treatment quality is seriously influenced. Therefore, the production yield of the material is low, and the performance and the service life of the product are uniform, so that the strict requirements of offshore use cannot be met.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide the forging and heat treatment process for the high-strength forging of the marine rudder system, which has the advantages of high product strength and toughness, good cold and hot deformation capability, excellent performance stability and long service life.

The technical purpose of the invention is realized by the following technical scheme:

a marine rudder system high-strength forging and heat treatment process comprises the following steps:

s1: smelting the raw materials;

s2: forging and heating the raw materials to obtain a steel ingot;

s3: forging to obtain a forged piece; the steel ingot forging comprises three heating times:

(1) the first fire time: the steel ingot is sequentially drawn out and upset, and the forging temperature is 1180-1205 ℃;

(2) the second fire time: the steel ingot is sequentially drawn out and upset and formed, and the forging temperature is 1180-1200 ℃;

(3) the third fire time: drawing and forming the steel ingot, wherein the forging temperature is 1150-1180 ℃;

s4: heat treating a forging, comprising:

(1) air cooling treatment after forging: placing the forging in air for cooling; (ii) a

(2) Normalizing and tempering the forging: 1. the forging piece is sent into a furnace for normalizing and heat preservation, the normalizing temperature is 920-930 ℃, the heat preservation time is positively correlated with the thickness of the forging piece, and the heat preservation time is 1.5-1.7 min for each 1mm of the forging piece; after the heat preservation is finished, discharging from the furnace, air cooling the forge piece, and after the air cooling is less than 500 ℃, feeding into the furnace for tempering; 2. feeding the forge piece into a furnace for tempering and heat preservation, wherein the tempering temperature is 660-680 ℃, the heat preservation time is positively correlated with the thickness of the forge piece, and the heat preservation time is 2.3-2.5 min for each 1mm of forge piece; cooling the forgings to below 400 ℃ along with the furnace after heat preservation is finished, discharging the forgings out of the furnace and air cooling the forgings;

(3) roughly machining a forged piece;

s5, quenching and tempering the forging, including:

(1) quenching the forged piece: putting a forged piece into a furnace for heating, preserving heat at the quenching temperature of 910-920 ℃, discharging the forged piece out of the furnace after heat preservation is finished, and putting the forged piece into a water-soluble medium pool for cooling;

(2) primary tempering: heating the forge piece in a furnace, preserving heat at the tempering temperature of 530-550 ℃, cooling the forge piece to below 400 ℃ along with the furnace after heat preservation is finished, and then discharging the forge piece from the furnace and air-cooling to room temperature;

secondary tempering: and (3) heating the forge piece in a furnace, preserving heat at the tempering temperature of 500-530 ℃, cooling the forge piece to below 400 ℃ along with the furnace after heat preservation is finished, and then discharging the forge piece from the furnace and air-cooling to room temperature.

Further, the forging comprises the following chemical elements in percentage by weight: c: 0.13 to 0.19%, Mn: 0.3-0.6%, P: not more than 0.020%, S not more than 0.020%, Si: less than or equal to 0.17-0.37 percent, Cr: 1.35-1.65%, Ni: 4.0-4.5%, W: 0.8 to 1.2 percent; cu: less than or equal to 0.20 percent, and the balance of Fe and impurities.

Further, the step S2 specifically includes: (1) charging; the charging temperature is less than or equal to 400 ℃; (2) heating; heating at 400-800 ℃ at the heating speed of less than or equal to 100 ℃/h; (3) preserving heat; carrying out heat preservation by stages, wherein the heat preservation temperature of the first stage is 850 ℃; the second stage heat preservation temperature is 1200 ℃; the heat preservation time of each heat preservation stage is positively correlated with the thickness of the steel ingot, and the heat preservation time of each steel ingot with the thickness of 200mm is 1.2-1.5 hours.

Further, in the first heating of the step S3, the finish forging temperature of the steel ingot is more than or equal to 900 ℃, and after the first heating is completed, the steel ingot is placed into a forging heating furnace to be heated, wherein the heating temperature is 1180-1200 ℃; the heating time is positively correlated with the thickness of the steel ingot, and the steel ingot with the thickness of 200mm is heated for 1.2-1.5 hours.

Further, in the second firing of the step S3, the finish forging temperature is more than or equal to 900 ℃; after the second firing, putting the steel ingot into a forging heating furnace for heating, wherein the heating temperature is 1150-1180 ℃; the heating time is positively correlated with the thickness of the steel ingot, and the steel ingot with the thickness of 200mm is heated for 1.2-1.5 hours.

Further, in the third firing of the step S3, the finish forging temperature is more than or equal to 900 ℃; and after the third firing, cooling the forge piece in air to 600 ℃ and then putting the forge piece into a furnace for post-forging heat treatment.

Further, in the first fire of step S3, the total draft ratio is > 2.2; the total upsetting ratio is more than 2.2; in the second fire, the total drawing length ratio is more than 2.2, and the total upsetting ratio is more than 2.2; in the third fire, the total draw ratio is greater than 2.2.

Further, in the normalizing and tempering treatment of step S4: loading the forging into a furnace for tempering at the temperature of 500-600 ℃; and (3) loading the forge piece into a furnace and tempering at the temperature of 680 ℃.

Further, in step S5: 1. in quenching, the heat preservation time is positively correlated with the thickness of the forged piece, and the heat preservation time is 1.5-1.7 min for each forged piece with the thickness of 1 mm; 2. in primary tempering, the heat preservation time is positively correlated with the thickness of the forge piece, and the heat preservation time is 2.3-2.5 min for each forge piece with the thickness of 1 mm; 3. in secondary tempering, the heat preservation time is positively correlated with the thickness of the forged piece, and the heat preservation time of the forged piece with the thickness of 1mm is 2.3-2.5 min.

Further, in step S5: 1. in the quenching process, the quenching heat preservation temperature is 910 ℃, the cooling temperature is less than 40 ℃, and then the quenching process is carried out in a furnace for tempering, wherein the repetition times of the quenching process is less than or equal to 2; 2. in primary tempering, the tempering heat preservation temperature is 540 ℃; 2. in the secondary tempering, the tempering heat preservation temperature is 500 ℃.

In conclusion, the invention has the following beneficial effects:

1. by adopting multi-fire-number temperature-control forging, larger deformation can be obtained as far as possible, the generation of forging piece cracks can be prevented, the problem of easy overheating is overcome, the grain size can be ensured, the structural uniformity of the material can be improved, a fine-grain matrix can be obtained, the fine-grain strengthening effect can be fully exerted, the comprehensive mechanical property of the product is greatly strengthened, and the service life of the product under severe sea conditions is further prolonged;

2. by adopting the post-forging normalizing and tempering mode, the crystal grains can be homogenized and refined, the non-uniformity of the structure is further eliminated, the residual stress in the material is eliminated, and the final heat treatment effect is effectively improved;

3. by adopting a heat treatment mode of quenching and double tempering, the existence of residual austenite can be reduced, the residual stress in the material can be eliminated, and the deformation resistance and the performance stability of the product are effectively improved.

4. By reasonably adjusting the content range of alloy elements in the steel, the forgeability of the material is improved, so that the deformation of the material is increased when forging is facilitated, the forged piece obtains uniform fine grains after forging, and the effect of fine grain strengthening is further exerted.

Drawings

FIG. 1 is a schematic step diagram of a marine rudder system high-strength forging and heat treatment process;

FIG. 2 is a gold phase diagram of sample 1;

FIG. 3 is a gold phase diagram of sample 2;

FIG. 4 is a gold phase diagram of sample 3.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the following detailed description of the present invention is provided with reference to the accompanying drawings and the detailed description. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are all used in a non-precise scale for the purpose of facilitating and distinctly aiding in the description of the embodiments of the present invention. To make the objects, features and advantages of the present invention comprehensible, reference is made to the accompanying drawings. It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the implementation conditions of the present invention, so that the present invention has no technical significance, and any structural modification, ratio relationship change or size adjustment should still fall within the scope of the present invention without affecting the efficacy and the achievable purpose of the present invention.

Example 1: a marine rudder system high-strength forging and heat treatment process is shown in figure 1 and comprises the following steps:

step S1: smelting the raw materials, which specifically comprises the following steps: the treatment process of electric arc furnace and external refining. The raw materials comprise the following chemical elements in percentage by weight: c: 0.13 to 0.19%, Mn: 0.3-0.6%, P: not more than 0.020%, S not more than 0.020%, Si: less than or equal to 0.17-0.37 percent, Cr: 1.35-1.65%, Ni: 4.0-4.5%, W: 0.8 to 1.2 percent; cu: less than or equal to 0.20 percent, and the balance of Fe and impurities. Because of the wide range of requirements for the alloying elements in the steel, the content range of the alloying elements is partially adjusted according to the requirements, and the malleability of the material is improved.

Step S2: forging and heating the raw materials to obtain a steel ingot. The method specifically comprises the following steps:

(1) charging; the charging temperature is less than or equal to 400 ℃; (2) heating; heating at 400-800 ℃ at the heating speed of less than or equal to 100 ℃/h; (3) preserving heat; carrying out heat preservation by stages, wherein the heat preservation temperature of the first stage is 850 ℃; the second stage heat preservation temperature is 1200 ℃; the heat preservation time of each heat preservation stage is positively correlated with the thickness of the steel ingot, and the heat preservation time of each steel ingot with the thickness of 200mm is 1.2-1.5 hours.

S3: forging to obtain a forged piece; the steel ingot forging comprises three heating times:

(1) the first fire time: the steel ingot is drawn out and upset in sequence, the forging temperature is 1180 ℃, and the final forging temperature is guaranteed to be more than or equal to 900 ℃. The total draw-out ratio is more than 2.2; the total upset ratio is > 2.2. After the first firing, putting the steel ingot into a forging heating furnace for heating, wherein the heating temperature is 1180 ℃; the heating time is positively correlated with the thickness of the steel ingot, and the steel ingot with the thickness of 200mm is heated for 1.2-1.5 hours.

(2) The second fire time: the steel ingot is drawn out and upset and formed in sequence, the forging temperature is 1180 ℃, and the final forging temperature is guaranteed to be more than or equal to 900 ℃. The total draw-out ratio is more than 2.2; the total upset ratio is > 2.2. After the second firing, putting the steel ingot into a forging heating furnace for heating, wherein the heating temperature is 1150 ℃; the heating time is positively correlated with the thickness of the steel ingot, and the steel ingot with the thickness of 200mm is heated for 1.2-1.5 hours.

(3) The third fire time: the steel ingot is drawn and formed, the forging temperature is 1150 ℃, and the final forging temperature is ensured to be more than or equal to 900 ℃. The total draw ratio is more than 2.2. And after the third firing, cooling the forge piece in air to 600 ℃ and then putting the forge piece into a furnace for post-forging heat treatment.

And finishing the treatment of three fire times to obtain the forged piece in the initial state.

S4: the forging heat treatment specifically comprises the following steps:

(1) air cooling treatment after forging: and (5) cooling the forging in the air, and cooling the forging to 500 ℃.

(2) Normalizing and tempering the forging: 1. the forging piece is sent into a furnace for normalizing and heat preservation, the furnace entering temperature is 500 ℃, the normalizing temperature is 920 ℃, the heat preservation time is positively correlated with the thickness of the forging piece, and the heat preservation time is 1.5-1.7 min for each 1mm of the forging piece; after the heat preservation is finished, discharging from the furnace, air cooling the forge piece, and after the air cooling is less than 500 ℃, feeding into the furnace for tempering; 2. feeding the forgings into a furnace for tempering and heat preservation, wherein the tempering temperature is 660 ℃, the heat preservation time is positively correlated with the thickness of the forgings, and the heat preservation time is 2.3-2.5 min for each 1mm of forgings; and after the heat preservation is finished, cooling the forge piece to below 400 ℃ along with the furnace, discharging and air cooling.

(3) And (5) rough machining of the forge piece.

S5, quenching and tempering the forging, which comprises the following steps:

(1) quenching the forged piece: and (3) putting the forged piece into a furnace for heating, preserving heat at the quenching temperature of 910 ℃, wherein the heat preservation time is in positive correlation with the thickness of the forged piece, preserving heat for 1.5-1.7 min for each forged piece with the thickness of 1mm, taking the forged piece out of the furnace after heat preservation is finished, and putting the forged piece into a water-soluble medium pool for cooling, wherein the cooling temperature must be less than 40 ℃ so as to be convenient for subsequent tempering in the furnace. According to the requirement of the forged piece, the quenching can be repeatedly carried out, and the repetition frequency of the quenching process is less than or equal to 2.

(2) Primary tempering: and (3) putting the forge piece into a furnace for heating, keeping the temperature of the forge piece at the temperature of less than 40 ℃ at the tempering temperature of 530 ℃, keeping the temperature for 2.3-2.5 min for each 1mm of the forge piece, cooling the forge piece to below 400 ℃ along with the furnace after keeping the temperature, and then discharging the forge piece from the furnace for air cooling to the room temperature.

(3) Secondary tempering: and (3) putting the forge piece into a furnace for heating, preserving heat at the tempering temperature of 500 ℃, wherein the heat preservation time is in positive correlation with the thickness of the forge piece, preserving heat for 2.3-2.5 min for each forge piece with the thickness of 1mm, cooling the forge piece to below 400 ℃ along with the furnace after the heat preservation is finished, and then discharging the forge piece from the furnace for air cooling to the room temperature.

Example 2: the marine rudder system high-strength forging and heat treatment process is different from that of the embodiment 1 in that:

s3: forging to obtain a forged piece; the steel ingot forging comprises three heating times:

(1) the first fire time: the steel ingot is drawn out and upset in sequence, the forging temperature is 1190 ℃, and the final forging temperature is more than or equal to 900 ℃. The total draw-out ratio is more than 2.2; the total upset ratio is > 2.2. After the first firing, putting the steel ingot into a forging heating furnace for heating, wherein the heating temperature is 1190 ℃; the heating time is positively correlated with the thickness of the steel ingot, and the steel ingot with the thickness of 200mm is heated for 1.2-1.5 hours.

(2) The second fire time: the steel ingot is drawn out and upset to form in sequence, the forging temperature is 1190 ℃, and the final forging temperature is guaranteed to be more than or equal to 900 ℃. The total draw-out ratio is more than 2.2; the total upset ratio is > 2.2. After the second firing, putting the steel ingot into a forging heating furnace for heating, wherein the heating temperature is 1165 ℃; the heating time is positively correlated with the thickness of the steel ingot, and the steel ingot with the thickness of 200mm is heated for 1.2-1.5 hours.

(3) The third fire time: the steel ingot is drawn and formed, the forging temperature is 1165 ℃, and the final forging temperature is guaranteed to be more than or equal to 900 ℃. The total draw ratio is more than 2.2. And after the third firing, cooling the forge piece in air to 600 ℃ and then putting the forge piece into a furnace for post-forging heat treatment.

S4: the forging heat treatment specifically comprises the following steps:

(1) air cooling treatment after forging: and (5) cooling the forging in air, and cooling the forging to 550 ℃.

(2) Normalizing and tempering the forging: 1. the forging piece is sent into a furnace for normalizing and heat preservation, the furnace entering temperature is 550 ℃, the normalizing temperature is 925 ℃, the heat preservation time is positively correlated with the thickness of the forging piece, and the heat preservation time is 1.5-1.7 min for each 1mm of the forging piece; after the heat preservation is finished, discharging from the furnace, air cooling the forge piece, and after the air cooling is less than 500 ℃, feeding into the furnace for tempering; 2. feeding the forgings into a furnace for tempering and heat preservation, wherein the tempering temperature is 670 ℃, the heat preservation time is positively correlated with the thickness of the forgings, and the heat preservation time is 2.3-2.5 min for each 1mm of forgings; and after the heat preservation is finished, cooling the forge piece to below 400 ℃ along with the furnace, discharging and air cooling.

S5, quenching and tempering the forging, which comprises the following steps:

(1) quenching the forged piece: and (3) putting the forged piece into a furnace for heating, preserving heat at the quenching temperature of 915 ℃, wherein the heat preservation time is in positive correlation with the thickness of the forged piece, preserving heat for 1.5-1.7 min for each forged piece with the thickness of 1mm, taking the forged piece out of the furnace after heat preservation is finished, and putting the forged piece into a water-soluble medium pool for cooling, wherein the cooling temperature must be less than 40 ℃, so that the forged piece can be conveniently placed into the furnace for tempering subsequently. According to the requirement of the forged piece, the quenching can be repeatedly carried out, and the repetition frequency of the quenching process is less than or equal to 2.

(2) Primary tempering: and (3) putting the forge piece into a furnace for heating, keeping the temperature of the forge piece at the annealing temperature of 540 ℃, wherein the heat preservation time is in positive correlation with the thickness of the forge piece, preserving the heat of the forge piece with the thickness of 1mm for 2.3-2.5 min, cooling the forge piece to below 400 ℃ along with the furnace after the heat preservation is finished, and then discharging the forge piece from the furnace and air-cooling to the room temperature.

(3) Secondary tempering: and (3) putting the forge piece into a furnace for heating, preserving heat at the tempering temperature of 515 ℃, wherein the heat preservation time is in positive correlation with the thickness of the forge piece, preserving heat for 2.3-2.5 min for each forge piece with the thickness of 1mm, cooling the forge piece to below 400 ℃ along with the furnace after the heat preservation is finished, and then discharging the forge piece from the furnace for air cooling to the room temperature.

Example 3: the marine rudder system high-strength forging and heat treatment process is different from that of the embodiment 1 in that:

s3: forging to obtain a forged piece; the steel ingot forging comprises three heating times:

(1) the first fire time: the steel ingot is drawn out and upset in sequence, the forging temperature is 1205 ℃, and the finish forging temperature is guaranteed to be more than or equal to 900 ℃. The total draw-out ratio is more than 2.2; the total upset ratio is > 2.2. After the first firing, putting the steel ingot into a forging heating furnace for heating, wherein the heating temperature is 1200 ℃; the heating time is positively correlated with the thickness of the steel ingot, and the steel ingot with the thickness of 200mm is heated for 1.2-1.5 hours.

(2) The second fire time: the steel ingot is drawn out and upset to form in sequence, the forging temperature is 1200 ℃, and the final forging temperature is guaranteed to be more than or equal to 900 ℃. The total draw-out ratio is more than 2.2; the total upset ratio is > 2.2. After the second firing, putting the steel ingot into a forging heating furnace for heating, wherein the heating temperature is 1180 ℃; the heating time is positively correlated with the thickness of the steel ingot, and the steel ingot with the thickness of 200mm is heated for 1.2-1.5 hours.

(3) The third fire time: and (3) drawing and forming the steel ingot, wherein the forging temperature is 1180 ℃, and the finish forging temperature is guaranteed to be more than or equal to 900 ℃. The total draw ratio is more than 2.2. And after the third firing, cooling the forge piece in air to 600 ℃ and then putting the forge piece into a furnace for post-forging heat treatment.

S4: the forging heat treatment specifically comprises the following steps:

(1) air cooling treatment after forging: and (5) cooling the forging in the air, and cooling the forging to 600 ℃.

(2) Normalizing and tempering the forging: 1. the forging piece is sent into a furnace for normalizing and heat preservation, the furnace entering temperature is 600 ℃, the normalizing temperature is 930 ℃, the heat preservation time is positively correlated with the thickness of the forging piece, and the heat preservation time is 1.5-1.7 min for each 1mm of the forging piece; after the heat preservation is finished, discharging from the furnace, air cooling the forge piece, and after the air cooling is less than 500 ℃, feeding into the furnace for tempering; 2. feeding the forgings into a furnace for tempering and heat preservation, wherein the tempering temperature is 680 ℃, the heat preservation time is positively correlated with the thickness of the forgings, and the heat preservation time is 2.3-2.5 min for each 1mm of forgings; and after the heat preservation is finished, cooling the forge piece to below 400 ℃ along with the furnace, discharging and air cooling.

S5, quenching and tempering the forging, which comprises the following steps:

(1) quenching the forged piece: and (3) putting the forged piece into a furnace for heating, keeping the temperature at the quenching temperature of 920 ℃, wherein the heat preservation time is in positive correlation with the thickness of the forged piece, preserving the heat of the forged piece with the thickness of 1mm for 1.5-1.7 min, taking the forged piece out of the furnace after the heat preservation is finished, and putting the forged piece into a water-soluble medium pool for cooling, wherein the cooling temperature is less than 40 ℃, so that the forged piece can be put into the furnace for tempering subsequently. According to the requirement of the forged piece, the quenching can be repeatedly carried out, and the repetition frequency of the quenching process is less than or equal to 2.

(2) Primary tempering: and (3) putting the forge piece into a furnace for heating, keeping the temperature of the forge piece at the tempering temperature of 550 ℃, keeping the temperature for 2.3-2.5 min, keeping the temperature of the forge piece with the thickness of 1mm for 2.3-2.5 min, cooling the forge piece to below 400 ℃ along with the furnace after the heat preservation is finished, and then discharging the forge piece from the furnace and air-cooling to the room temperature.

(3) Secondary tempering: and (3) putting the forge piece into a furnace for heating, preserving heat at the tempering temperature of 530 ℃, wherein the heat preservation time is in positive correlation with the thickness of the forge piece, preserving heat for 2.3-2.5 min for each forge piece with the thickness of 1mm, cooling the forge piece to below 400 ℃ along with the furnace after the heat preservation is finished, and then discharging the forge piece from the furnace for air cooling to the room temperature.

And (3) product performance detection:

sample preparation: a set of products was randomly sampled from example 1, example 2 and example 3 as samples.

Detecting items: tensile strength Rm (MPa), yield strength Rp0.2(MPa), elongation A%, shrinkage Z%, AKv impact (J) and hardness HB.

The staff respectively carries out comprehensive mechanical experiments on the three groups of samples, and detailed detection results are shown in table 1.

Table 1: comprehensive performance detection meter for forge pieces

And (3) analyzing an experimental result:

1. tensile strength Rm (MPa) and yield strength Rp0.2(MPa) are two important structural strength indexes, the structural strength of the forge piece can be intuitively reflected, the measured values of the samples 1, 2 and 3 all meet the performance requirements, and the yield strength exceeds the standard by about 20%.

2. The elongation A% and the shrinkage Z% are performance indexes reflecting the plasticity of the forged piece, the measured values of the samples 1, 2 and 3 all meet the performance requirements, and the measured value of the shrinkage Z% is nearly doubled over the standard.

3. AKv impact (J) reflects the capability of a forging piece to resist deformation and fracture under the action of impact load, and the ak value is obviously reduced by inclusion, segregation, bubbles, coarsening of internal crack grains and the like in a common material. And (3) performing three times of impact energy tests on each group of samples, wherein the actual measurement result far exceeds the standard, further shows that the internal structure of the forging is uniform and compact, reduces the existence of residual austenite, and eliminates the residual stress in the material.

4. The measured values of the hardness HB, the hardness 1, the hardness 2 and the hardness 3 all meet the performance requirements, and the forgeability of the forge piece is considered on the premise of ensuring the use requirements.

And (3) carrying out microstructure microscopic detection on the forged piece:

detecting items: 1. the grain size is not less than 5 grades according to GB/T6394.

2. The non-metallic inclusion is GB/T10561, the fineness of A is less than or equal to 1.5, and the thickness of A is less than or equal to 1.0; b is not more than 1.5 fine and not more than 1.0 coarse; the fineness of C is less than or equal to 1.5, and the thickness of C is less than or equal to 1.0; the fineness of D is less than or equal to 2.0, and the thickness of D is less than or equal to 1.0.

Samples were randomly selected from example 1, example 2 and example 3, respectively.

And (3) metallographic detection results:

sample 1:

A. the metallographic microscopic result is shown in fig. 2, and it can be seen that the structure is uniform and dense, and no grain boundary fracture occurs.

B. A is fine 0, and A is coarse 0; b is 0.5 thin and B is 0.5 thick; c is 1.0 thin and C is 1.0 thick; d is 1.0 thin and 1.0 thick, and meets the standard.

C. Grain size rating scale: grade 7.5, greater than grade 5, meets the standard.

Sample 2:

A. the metallographic microscopic result is shown in FIG. 3, and it can be seen that the structure is uniform and dense, and no grain boundary fracture occurs.

B. A is 0.5 thin and A is 0.5 thick; b is 0.5 thin and B is 0.5 thick; fine C by 0.5 and coarse C by 0.5; d is 1.0 thin and 1.0 thick, and meets the standard.

C. Grain size rating scale: grade 8, more than grade 5, and meets the standard.

Sample 3:

A. the metallographic microscopic results are shown in FIG. 4, and it can be seen that the structure is uniform and dense, with no grain boundary fracture.

B. A is 1.0 thin and A is 1.0 thick; b is 0.5 thin and B is 0.5 thick; fine C by 0.5 and coarse C by 0.5; d is 1.0 thin and 1.0 thick, and meets the standard.

C. Grain size rating scale: grade 8, more than grade 5, and meets the standard.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.