Method for improving impact toughness of A694 F65 seabed forging

Abstract

The invention discloses a method for improving the impact toughness of an A694 F65 submarine forging, which comprises the following steps: forging and heating: forging the A694 F65 forging at the heating temperature of 1180-1250 DEG C, carrying out stepped heating, at least upsetting twice and drawing twice in the forging process, and ensuring that the forging ratio is not less than 4; preheating treatment: austenitizing at 930 + / -10 DEG C, then cooling to 650 + / -10 DEG C along with a furnace, preserving heat for 2-3 hours, and then air-cooling to room temperature; and the heat treatment mode comprises quenching and tempering treatment, and the A694 F65 forge piece with good impact toughness is obtained. The invention discloses a method for improving the impact toughness of A694 F65 submarine forgings, which solves the problem of unstable impact toughness caused by non-uniform microstructure, adjusts and uniformizes the microstructure of the forgings and improves the impact toughness of the A694 F65 forgings.

Description

Technical Field

[0001] The invention relates to the technical field of production of submarine forgings, and in particular to a method for improving the impact toughness of A694 F65 submarine forgings. Background Art

[0002] With the increasingly tense global energy supply and demand, the gradual depletion of terrestrial oil and gas resources and the continuous development of offshore oil development, offshore oil and gas development is constantly moving from shallow water to deep water, even ultra-deep water. As a commonly used forging material for underwater devices, the stability of A694 F65 product quality, especially impact toughness, is particularly important.

[0003] At present, underwater forgings are usually manufactured in accordance with DNV-ST-F101 or DNV-RP-0034, which has strict regulations and requirements on the sampling location and sampling quantity of products. In actual applications, A694 F65 forgings will be subjected to -46℃ low-temperature impact tests, but "two highs and one low" or even unqualified phenomena often occur. This instability of impact toughness has caused many troubles in the use of products. There are many reasons for the instability of the impact toughness of A694 F65, such as organizational segregation, non-metallic inclusions, and organizational unevenness. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for improving the impact toughness of A694 F65 submarine forgings, solves the problem of unstable impact toughness caused by uneven microstructure, and performs preheating treatment through isothermal annealing to adjust the microstructure of the forging to be uniform, thereby laying a foundation for improving the A694 F65 forgings to obtain high and stable impact toughness.

[0005] To solve the above technical problems, a technical solution adopted by the present invention is: a method for improving the impact toughness of A694 F65 submarine forgings, selecting A694 F65 forgings as the main body, and the A694 F65 forgings include the following components in mass percentage: C≤0.12%; Si≤0.35%; Mn: 1.0%-1.4%; P≤0.015%; S≤0.015%; Ni: 0.7%-1.0%; Cr≤0.30%; Al≤0.055%; Ti≤0.15%; Mo≤0.5%; Cu≤0.3%; V≤0.03%; N≤0.012%; CE: 0.42%-0.48%, wherein: CE=C+Mn / 6+(Cr+Mo+V) / 5+(Cu+Ni) / 15.

[0006] In a preferred embodiment of the present invention, the A694 F65 forging includes the following components by mass percentage: C: 0.10%; Si: 0.22%; Mn: 1.18%; P: 0.010%; S: 0.002%; Ni: 0.93%; Cr%: 0.22%; Mo: 0.28%; Al: 0.027%; Cu: 0.05%; Ti: 0.0011%; Nb: 0.014%; V: 0.02%; B: 0.0004%; N: 0.0056%; CE: 0.47%.

[0007] A method for improving the impact toughness of A694 F65 subsea forgings, comprising the following steps: (1) Forging heating: Forging A694 F65 forgings, the heating temperature is 1180℃-1250℃, and step heating is performed. During the heating process, the temperature is kept at 650℃±10℃ for 2-3 hours, and then the temperature is raised to the heating temperature for keeping; (2) Forging: Forging shall be performed through at least two upsettings and two drawing operations, and the forging ratio shall not be less than 4; (3) Preliminary heat treatment: isothermal annealing treatment is adopted, austenitizing is carried out at 930℃±10℃, and the holding time is calculated as 30min-60min / 25.4mm, and then the temperature is lowered to 650℃±10℃ with the furnace, and then air-cooled to room temperature after holding for 2-3 hours; (4) Heat treatment method: quenching and tempering treatment, the quenching holding temperature is 890℃±10℃, the holding time is calculated as 30min-60min / 25.4mm, and water cooling is used for cooling after quenching; the tempering holding temperature is 630℃±8℃, the holding time is calculated as 30min-60min / 25.4mm, and air cooling is used for cooling after tempering to obtain A694 F65 forgings with good impact toughness.

[0008] In a preferred embodiment of the present invention, in step (4), the furnace temperature does not exceed 300°C, and the heating rate does not exceed 150°C / hour.

[0009] In a preferred embodiment of the present invention, in step (4), the temperature of the cooling medium selected for water cooling is controlled within 40°C.

[0010] In a preferred embodiment of the present invention, the method further includes the steps of sampling and mechanical property testing of the A694 F65 forgings obtained in step (4).

[0011] The beneficial effects of the present invention are: solving the problem of unstable impact toughness caused by uneven microstructure, adjusting the microstructure of the forging to be uniform by preheating through isothermal annealing, improving the impact toughness of the A694 F65 forging, and obtaining higher stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which: Figure 1 It is an impact work test diagram of a method for improving the impact toughness of A694 F65 seabed forgings of the present invention; Figure 2 This is a test diagram of the impact function of A694 F65 seabed forgings obtained after normalizing. DETAILED DESCRIPTION

[0013] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] See also Figure 1-2 The embodiment of the present invention includes: a method for improving the impact toughness of A694 F65 submarine forgings, selecting A694 F65 forgings as a main body, and the A694 F65 forgings include the following components by mass percentage: C≤0.12%; Si≤0.35%; Mn:1.0%-1.4%; P≤0.015%; S≤0.015%; Ni:0.7%-1.0%; Cr≤0.30%; Al≤0.055%; Ti≤0.15%; Mo≤0.5%; Cu≤0.3%; V≤0.03%; N≤0.012%; CE:0.42%-0.48%, wherein: CE=C+Mn / 6+(Cr+Mo+V) / 5+(Cu+Ni) / 15.

[0015] A method for improving the impact toughness of A694 F65 subsea forgings, comprising the following steps: (1) Forging heating: Forging A694 F65 forgings, the heating temperature is 1180℃-1250℃, and step heating is performed. During the heating process, the temperature is kept at 650℃±10℃ for 2-3 hours, and then the temperature is raised to the heating temperature for keeping; (2) Forging: Forging shall be performed through at least two upsettings and two drawing operations, and the forging ratio shall not be less than 4; (3) Preliminary heat treatment: austenitizing at 930℃±10℃, holding time is 30min-60min / 25.4mm, then cooling to 650℃±10℃ with furnace, holding for 2-3 hours, and then air cooling to room temperature; (4) Heat treatment method: quenching and tempering treatment, the quenching holding temperature is 890℃±10℃, the holding time is calculated as 30min-60min / 25.4mm, and water cooling is used for cooling after quenching; the tempering holding temperature is 630℃±8℃, the holding time is calculated as 30min-60min / 25.4mm, and air cooling is used for cooling after tempering to obtain A694 F65 forgings with good impact toughness. The obtained A694 F65 forgings are sampled and the mechanical properties are tested.

[0016] In a preferred embodiment of the present invention, in step (4), the furnace temperature does not exceed 300°C, and the heating rate does not exceed 150°C / hour.

[0017] In a preferred embodiment of the present invention, in step (4), the temperature of the cooling medium selected in the water cooling is controlled within 40°C. Example 1

[0018] 1. Select raw materials: A694 F65 forgings are selected, which include the following components by mass percentage: C: 0.10%; Si: 0.22%; Mn: 1.18%; P: 0.010%; S: 0.002%; Ni: 0.93%; Cr%: 0.22%; Mo: 0.28%; Al: 0.027%; Cu: 0.05%; Ti: 0.0011%; Nb: 0.014%; V: 0.02%; B: 0.0004%; N: 0.0056%; CE: 0.47%.

[0019] 2. Forging heating: The selected A694 F65 forgings are forged at a heating temperature of 1200°C and step-wise heating is performed. During the heating process, the temperature is kept at 650°C±10°C for 2 hours, then the temperature is raised to 1200°C for 6 hours.

[0020] 3. Forging: Forging must go through at least two upsetting and two drawing passes, and the forging ratio must be greater than 4. The final forging temperature must not be lower than 800°C. Air cooling must be used after forging. The forging process must be a maximum of three times. Multiple upsetting and drawing passes must be performed to ensure uniform internal structure of the forging and eliminate or reduce casting defects such as porosity, segregation, and columnar crystals.

[0021] 4. Preliminary heat treatment: isothermal annealing treatment is adopted, austenitizing is carried out at 930℃, the holding time is 5 hours, and then the temperature is lowered to 650℃ with the furnace, kept for 2 hours, and then air-cooled to room temperature. Among them, the furnace temperature does not exceed 300℃, and the heating rate does not exceed 150℃ / hour.

[0022] 5. Heat treatment method: quenching and tempering treatment, quenching holding temperature is 890℃, holding time is 5 hours, water cooling is used for cooling after quenching, the cooling medium temperature selected in water cooling is 40℃, tempering holding temperature is 630℃, holding time is 9 hours, air cooling is used for cooling after tempering to obtain A694 F65 forgings with good impact toughness, and then the obtained A694 F65 forgings are sampled for -46℃ impact toughness test, such as Figure 1 shown. Example 2

[0023] 1. Select raw materials: A694 F65 forgings are selected, which include the following components by mass percentage: C: 0.10%; Si: 0.22%; Mn: 1.18%; P: 0.010%; S: 0.002%; Ni: 0.93%; Cr%: 0.22%; Mo: 0.28%; Al: 0.027%; Cu: 0.05%; Ti: 0.0011%; Nb: 0.014%; V: 0.02%; B: 0.0004%; N: 0.0056%; CE: 0.47%.

[0024] 2. Forging heating: The selected A694 F65 forgings are forged at a heating temperature of 1200°C and step-wise heating is performed. During the heating process, the temperature is kept at 650°C±10°C for 2 hours, then the temperature is raised to 1200°C for 6 hours.

[0025] 3. Forging: Forging must go through at least two upsetting and two drawing passes, and the forging ratio must be greater than 4. The final forging temperature must not be lower than 800°C. Air cooling must be used after forging. The forging process must be a maximum of three times. Multiple upsetting and drawing passes must be performed to ensure uniform internal structure of the forging and eliminate or reduce casting defects such as porosity, segregation, and columnar crystals.

[0026] 4. Preliminary heat treatment: normalizing treatment, austenitizing at 930℃, holding time for 5 hours, then cooling to 650℃ with the furnace, holding for 2 hours, and air cooling to room temperature, wherein the furnace temperature does not exceed 300℃, and the heating rate does not exceed 150℃ / hour; 5. Heat treatment method: quenching and tempering treatment, quenching holding temperature is 890℃, holding time is 5 hours, water cooling is used for cooling after quenching, the cooling medium temperature selected in water cooling is 40℃, tempering holding temperature is 630℃, holding time is 9 hours, air cooling is used for cooling after tempering to obtain A694 F65 forgings, and then the obtained A694 F65 forgings are sampled for -46℃ impact toughness test, such as Figure 2 As shown in the figure, the A694 F65 forgings were pre-heat treated in two different ways, and the results are as follows: Figure 1 and Figure 2 The data of forging impact toughness in the table and experimental test data show that isothermal annealing for preheating can adjust and uniform the microstructure of the forging, thus providing an important guarantee for A694 F65 submarine forgings to obtain high and stable impact toughness.

[0027] The present invention discloses a method for improving the impact toughness of A694 F65 seabed forgings, which has the beneficial effects of solving the problem of unstable impact toughness caused by uneven microstructure, adjusting and homogenizing the forging microstructure by preheating treatment through isothermal annealing, improving the impact toughness of A694 F65 forgings, and obtaining higher stability.

[0028] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for improving the impact toughness of A694 F65 seabed forgings, using A694 F65 forgings as the main body, characterized in that: The A694 F65 forging includes the following components in percentage by mass: C≤0.12%; Si≤0.35%; Mn:1.0%-1.4%; P≤0.015%; S≤0.015%; Ni:0.7%-1.0%; Cr≤0.30%; Al≤0.055%; Ti≤0.15%; Mo≤0.5%; Cu≤0.3%; V≤0.03%; N≤0.012%; CE:0.42%-0.48%, wherein: CE=C+Mn / 6+(Cr+Mo+V) / 5+(Cu+Ni) / 15.

2. A method for improving the impact toughness of A694 F65 seabed forgings according to claim 1, characterized in that: The A694 F65 forging includes the following components by mass percentage: C: 0.10%; Si: 0.22%; Mn: 1.18%; P: 0.010%; S: 0.002%; Ni: 0.93%; Cr%: 0.22%; Mo: 0.28%; Al: 0.027%; Cu: 0.05%; Ti: 0.0011%; Nb: 0.014%; V: 0.02%; B: 0.0004%; N: 0.0056%; CE: 0.47%.

3. A method for improving the impact toughness of A694 F65 seabed forgings according to claim 1, characterized in that: The following steps are involved: (1) Forging heating: Forging A694 F65 forgings, the heating temperature is 1180℃-1250℃, and step heating is performed. During the heating process, the temperature is kept at 650℃±10℃ for 2-3 hours, and then the temperature is raised to the heating temperature for keeping; (2) Forging: Forging shall be performed through at least two upsettings and two drawing operations, and the forging ratio shall not be less than 4; (3) Preliminary heat treatment: isothermal annealing treatment is adopted, austenitizing is carried out at 930℃±10℃, and the holding time is calculated as 30min-60min / 25.4mm, and then the temperature is lowered to 650℃±10℃ with the furnace, and then air-cooled to room temperature after holding for 2-3 hours; (4) Heat treatment method: quenching and tempering treatment, the quenching holding temperature is 890℃±10℃, the holding time is calculated as 30min-60min / 25.4mm, and the quenching is cooled by water; the tempering holding temperature is 630℃±8℃, the holding time is calculated as 30min-60min / 25.4mm, and air cooling is used after tempering to obtain A694F65 forgings with good impact toughness.

4. A method for improving the impact toughness of A694 F65 seabed forgings according to claim 1, characterized in that: In step (4), the furnace temperature does not exceed 300°C and the heating rate does not exceed 150°C / hour.

5. A method for improving the impact toughness of A694 F65 seabed forgings according to claim 1, characterized in that: In step (4), the temperature of the cooling medium selected in the water cooling is controlled within 40°C.

6. A method for improving the impact toughness of A694 F65 seabed forgings according to claim 1, characterized in that: The method also includes the steps of sampling and mechanical property testing of the A694 F65 forgings obtained in step (4).

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