Multi-layer rapid solidification rotary casting method for steel-high-strength aluminum alloy composite pipe

Abstract

The invention relates to a multi-layer rapid solidification rotary casting method for a steel-high-strength aluminum alloy composite pipe, which specifically comprises the following steps: S1, horizontally arranging a steel pipe, and mounting sealing plugs with central sprue gates at the two ends of the steel pipe; s2, inert gas is continuously introduced, the steel pipe is heated to 700 + / -10 DEG C, and heat preservation is conducted; s3, the steel pipe is driven to rotate at the rotating speed of 100 + / -10 rpm; molten aluminum alloy liquid is poured into an inner cavity of the steel pipe at the speed of 0.5-2 kg / s, and inert gas is kept being introduced in the process; s4, heating is stopped, the steel pipe is driven to rotate at the rotating speed of 1000 + / -50 rpm, and in the process, inert gas introduction is maintained till the temperature is reduced to 300 DEG C or below; and the steel-high-strength aluminum alloy composite pipe is obtained. According to the method, interface bonding strengthening and composite layer homogenization of the steel and the aluminum alloy are achieved; the whole method is simple and efficient, and the obtained composite pipe has the characteristics of high strength, high wear resistance and corrosion resistance of outer side steel and high specific strength and light weight of aluminum alloy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal composite material preparation, in particular to a multi-layer rapid solidification rotary casting method for steel-high strength aluminum alloy composite pipe. BACKGROUND

[0002] The high-strength aluminum alloy drilling rod has a series of advantages such as light weight, high strength, energy saving, deep well and special-shaped well drilling, low temperature resistance, easy manufacturing and maintenance, convenient transportation and recycling, and has significant economic and social benefits, especially in deep well, inclined well and offshore drilling.

[0003] At present, the production of high-strength aluminum alloy drill pipe, especially for 7 series ultra-high strength aluminum alloy, is generally difficult to form due to low plasticity and toughness, and is not resistant to acid and alkali corrosion and wear, which limits its use. The preparation of steel-high strength aluminum alloy composite pipe is mostly by thermal spraying, explosive welding or rolling composite process, but there are the following problems:

[0004] 1. Low interfacial bonding strength: thermal spraying or rolling process easily leads to too thick intermetallic compound layer (such as FeAl3), reducing the toughness of the composite layer;

[0005] 2. Low production efficiency: explosive welding requires complex charging and safety protection, and is difficult to produce continuously;

[0006] 3. Organizational defects: rolling composite easily introduces pores, cracks and other defects, affecting the density of the material;

[0007] 4. High cost: existing processes require high-temperature and high-pressure equipment or noble metal additives, increasing production cost.

[0008] Therefore, it is urgent to develop a casting method for steel-high strength aluminum alloy composite pipe which is efficient, low cost and can realize controllable interfacial bonding. SUMMARY

[0009] To solve the above technical problems, the present application provides a multi-layer rapid solidification rotary casting method for steel-high strength aluminum alloy composite pipe, which realizes the interfacial bonding strengthening of steel and aluminum alloy and the homogenization of the composite layer by inert gas protection, high-temperature pouring and multi-layer rapid solidification rotary casting forming. The overall method is simple and efficient, and the obtained composite pipe has high strength, high wear resistance and corrosion resistance on the outside, and high specific strength and light weight characteristics of aluminum alloy.

[0010] The technical scheme adopted by the present application to solve the technical problems is: a multi-layer rapid solidification rotary casting method for steel-high strength aluminum alloy composite pipe, which is specifically performed according to the following steps:

[0011] S1, horizontally placing a base steel pipe, and installing a sealing plug with a central pouring port at both ends of the base steel pipe;

[0012] S2, continuously feeding inert gas into the base steel pipe from the center pouring gate; heating the base steel pipe to 700±10℃ and maintaining the temperature;

[0013] S3, driving the base steel pipe to rotate at a speed of 100±10 rpm; at the same time, pouring the molten aluminum alloy into the inner cavity of the base steel pipe through the center pouring gate at a rate of 0.5-2 kg / s; during the pouring process, the inert gas is maintained to be fed;

[0014] S4, stopping heating after pouring is completed, driving the base steel pipe to rotate at a speed of 1000±50 rpm, and maintaining the inert gas to be fed until the temperature drops to below 300℃; thus obtaining a composite pipe material with a steel outer layer and an aluminum alloy inner layer.

[0015] Further, in step S2, the inert gas is argon or nitrogen, and before step S3, the oxygen content in the base steel pipe is controlled to be not more than 50 ppm.

[0016] Further, in step S2, during heating and maintaining the temperature, the base steel pipe is driven to rotate at a speed of 10-50 rpm.

[0017] Further, in step S3, the pouring temperature of the aluminum alloy liquid is 690-710℃.

[0018] Further, in step S3, the gas pressure in the base steel pipe is maintained at 0.15-0.25 MPa.

[0019] Further, in step S3, the amount of aluminum alloy liquid is determined according to the length and inner diameter of the base steel pipe and the required thickness of the aluminum alloy layer.

[0020] Further, the speed of the base steel pipe from step S3 to step S4 is completed within 5s.

[0021] Further, in step S4, the rotation time is controlled to be: aluminum alloy layer thickness × (0.8-1.2) min / mm; wherein the unit of the aluminum alloy layer thickness is mm.

[0022] Advantages of this invention: This invention provides a multi-layer rapid solidification rotary casting method for steel-high-strength aluminum alloy composite pipes. Through inert gas protection, high-temperature pouring, and multi-layer rapid solidification rotary casting, it achieves enhanced interfacial bonding between steel and aluminum alloys and homogenization of the composite layer. By controlling the rotation speed to 100±10 rpm, the flow of molten aluminum alloy during pouring can be controlled, reducing the thickness of the intermetallic compound layer and improving the toughness of the composite layer. By controlling the rotation speed to 1000±50 rpm, the grain refinement of the aluminum alloy and the smoothness of the inner wall of the composite layer can be controlled during solidification. The overall method is simple and efficient, and the resulting composite pipe combines the high strength, high wear resistance, and corrosion resistance of the outer steel with the high specific strength and lightweight properties of the aluminum alloy. Detailed Implementation

[0023] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0024] Example 1

[0025] This embodiment employs a multi-layer rapid solidification rotary casting method for preparing small-diameter steel-high-strength aluminum alloy composite pipes (steel pipe specifications: Φ30mm×2.5mm seamless steel pipe, target aluminum layer thickness: 1.0mm).

[0026] S1. Steel pipe pretreatment and placement:

[0027] The Φ30mm steel pipe is placed horizontally on the roller frame, and sealing plugs with central pouring ports are installed at both ends;

[0028] S2, Inert gas protection and heating:

[0029] Argon gas (flow rate 10L / min) is introduced through the central pouring port to replace the oxygen content in the steel pipe to no more than 35ppm; the temperature is heated to 700℃ and held, and the steel pipe is driven to rotate at 30rpm to ensure uniform heating;

[0030] S3, Aluminum alloy liquid casting:

[0031] The steel pipe is driven to rotate at 100 rpm, and molten 7075 aluminum alloy at 700℃ is poured into the inner cavity of the steel pipe at a rate of 1.0 kg / s; the air pressure in the inner cavity of the steel pipe is controlled at 0.2 MPa, and the flow of the aluminum alloy liquid is regulated to reduce interfacial reaction.

[0032] S4, Solidification and Shaping:

[0033] After heating is stopped, the steel pipe rotation speed is increased to 1000 rpm within 5 seconds; argon gas is introduced throughout the process, and high-speed rotation casting continues for 1.0 min (1.0 mm × 1.0 min / mm), and the pipe temperature drops below 300℃, forming a composite pipe with an outer layer of steel (Φ30 mm) and an inner layer of 7075 high-strength aluminum alloy (thickness 1.0 mm).

[0034] Example 2

[0035] This embodiment employs a multi-layer rapid solidification rotary casting method for the preparation of large-diameter steel-high-strength aluminum alloy composite pipes (steel pipe specifications: Φ150mm×5mm seamless steel pipe, target aluminum layer thickness: 3.0mm).

[0036] S1. Steel pipe pretreatment and installation:

[0037] The Φ150mm steel pipe is placed horizontally on the roller frame, and sealing plugs with central pouring ports are installed at both ends;

[0038] S2, Inert gas protection and heating:

[0039] Nitrogen gas (flow rate 12L / min) is introduced through the central pouring port to replace the oxygen content in the steel pipe to no more than 40ppm; the temperature is then raised to 705℃ and held, and the steel pipe is driven to rotate at 40rpm to ensure uniform heating.

[0040] S3, Aluminum alloy liquid casting:

[0041] The steel pipe is driven to rotate at 105 rpm, and molten 7075 aluminum alloy at 705℃ is poured into the inner cavity of the steel pipe at a rate of 1.8 kg / s; the air pressure in the inner cavity of the steel pipe is controlled at 0.22 MPa, and the flow of the aluminum alloy liquid is regulated to reduce interfacial reaction.

[0042] S4, Solidification and Shaping:

[0043] After heating is stopped, the steel pipe rotation speed is increased to 1050 rpm within 5 seconds; nitrogen gas is introduced throughout the process, and high-speed rotation casting continues for 3.6 minutes (3.0 mm × 1.2 min / mm), and the pipe temperature drops below 300℃, forming a composite pipe with an outer layer of steel (Φ150 mm) and an inner layer of 7075 high-strength aluminum alloy (thickness 3.0 mm).

[0044] Example 3

[0045] This embodiment employs a multi-layer rapid solidification rotary casting method for preparing high-density steel-high-strength aluminum alloy composite pipes (steel pipe specifications: Φ60mm×3mm seamless steel pipe, target aluminum layer thickness: 2.0mm).

[0046] S1. Steel pipe pretreatment and placement:

[0047] The Φ60mm steel pipe is placed horizontally on the roller frame, and sealing plugs with central pouring ports are installed at both ends;

[0048] S2, Inert gas protection and heating:

[0049] Argon gas (flow rate 8L / min) is introduced through the central pouring port to replace the oxygen content in the steel pipe to no more than 25ppm; the temperature is then raised to 695℃ and held, and the steel pipe is driven to rotate at 25rpm to ensure uniform heating.

[0050] S3, Aluminum alloy liquid casting:

[0051] The steel pipe is driven to rotate at 95 rpm, and molten 7055 aluminum alloy at 705℃ is poured into the inner cavity of the steel pipe at a rate of 1.5 kg / s; the air pressure in the inner cavity of the steel pipe is controlled at 0.18 MPa, and the flow of the aluminum alloy liquid is regulated to reduce interfacial reaction.

[0052] S4, Solidification and Shaping:

[0053] After heating is stopped, the steel pipe rotation speed is increased to 980 rpm within 5 seconds; argon gas is introduced throughout the process, and high-speed rotation casting continues for 2.0 min (2.0 mm × 1.0 min / mm), and the pipe temperature drops below 300℃, forming a composite pipe with an outer layer of steel (Φ60 mm) and an inner layer of 7055 high-strength aluminum alloy (thickness 2.0 mm).

[0054] The parameters and properties of the composite pipes prepared in Examples 1 to 3 are shown in the table below:

[0055]

[0056] The method described in the above embodiments effectively enhances the bonding strength and density of the steel-aluminum interface, and the resulting composite pipe combines the high strength, high wear resistance, and corrosion resistance of the outer steel with the high specific strength and lightweight properties of aluminum.

[0057] The above embodiments should not limit the present invention in any way. All technical solutions obtained by equivalent substitution or equivalent conversion fall within the protection scope of the present invention.

Claims

1. A multi-layer rapid solidification rotary casting method for steel-high-strength aluminum alloy composite pipes, characterized in that: The method is specifically carried out in the following steps: S1. Place the base steel pipe horizontally and install sealing plugs with central pouring ports at both ends of the base steel pipe. S2. Continuously introduce inert gas into the base steel pipe from the central pouring port; heat the base steel pipe to 700±10℃ and keep it at that temperature; S3. Drive the base steel pipe to rotate at a constant speed of 100±10 rpm; at the same time, pour molten aluminum alloy liquid into the inner cavity of the base steel pipe through the central pouring port at a rate of 0.5-2 kg / s; during the pouring process, maintain the inert gas supply. S4. After casting is completed, stop heating and drive the base steel pipe to rotate at a constant speed of 1000±50 rpm. During this process, maintain the inert gas supply until the temperature drops below 300℃; thus, a composite pipe with an outer layer of steel and an inner layer of aluminum alloy is obtained.

2. The multi-layer rapid solidification rotary casting method for steel-high-strength aluminum alloy composite pipes according to claim 1, characterized in that: In step S2, the inert gas is argon or nitrogen. Before step S3, the oxygen content in the base steel pipe is controlled to be no more than 50 ppm.

3. The multi-layer rapid solidification rotary casting method for steel-high-strength aluminum alloy composite pipes according to claim 1, characterized in that: In step S2, during the heating and heat preservation process, the base steel pipe is driven to rotate at a constant speed of 10-50 rpm.

4. The multi-layer rapid solidification rotary casting method for steel-high-strength aluminum alloy composite pipes according to claim 1, characterized in that: In step S3, the pouring temperature of the aluminum alloy liquid is 690-710℃.

5. The multi-layer rapid solidification rotary casting method for steel-high-strength aluminum alloy composite pipes according to claim 1, characterized in that: In step S3, the air pressure inside the base steel pipe is maintained at 0.15-0.25 MPa.

6. The multi-layer rapid solidification rotary casting method for steel-high-strength aluminum alloy composite pipes according to claim 1, characterized in that: In step S3, the amount of aluminum alloy liquid used is determined based on the length and inner diameter of the base steel pipe and the required thickness of the aluminum alloy layer.

7. The multi-layer rapid solidification rotary casting method for steel-high-strength aluminum alloy composite pipes according to claim 1, characterized in that: The process of increasing the rotational speed of the base steel pipe from step S3 to step S4 is completed within 5 seconds.

8. The multi-layer rapid solidification rotary casting method for steel-high-strength aluminum alloy composite pipes according to claim 1, characterized in that: In step S4, the rotation time is controlled as: aluminum alloy layer thickness × (0.8-1.2) min / mm; where the unit of aluminum alloy layer thickness is mm.

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