A method for assisting hydrogen expansion of a forging based on ultrasonic-direct current energy field

Abstract

The present application relates to a kind of based on ultrasonic-dc energy field auxiliary forging hydrogen expansion method, utilize additional ultrasonic-dc energy field to assist metal hydrogen expansion, comprising: S1, after heat treatment, workpiece is placed in the support frame in water tank inside;S2, metal workpiece both sides are connected with electric wire, the other end of electric wire is connected with DC power supply, and power supply is opened;S3, inject salt solution medium to immerse workpiece;S4, in water tank both sides fixed ultrasonic transducer, open ultrasonic transducer, and carry out hydrogen removal.It can effectively remove most of the hydrogen atom inside metal in short time after being treated by the method, so that the original elongation of metal is restored, and the strength after hydrogen charging is retained, while the heat treatment time is reduced, and the defects such as crack and temper brittleness of metal caused by heat treatment are avoided, and the service life of metal is prolonged.The method uses the mode of two energy field superposition, compared with the current hydrogen removal heat treatment, can save time, and more efficient hydrogen removal.

Description

Technical Field

[0001] This invention relates to the field of metal material processing technology, and in particular to a method for hydrogen diffusion of forgings based on ultrasonic-DC energy field assisted by an ultrasonic-DC energy field. Background Technology

[0002] Hydrogen is one of the major hazards affecting the safe service of metallic materials. The hazards of hydrogen atoms to metals are widespread in industries such as aerospace, oil and gas, and metallurgy. From giant forgings to small screws and nuts, hydrogen embrittlement of metals can occur.

[0003] Hydrogen atoms in metals can be categorized into endogenous and exogenous hydrogen based on their origin. Endogenous hydrogen refers to hydrogen atoms introduced into the metal material during processing, such as smelting, machining, pickling, electroplating, and heat treatment, where hydrogen from the air or liquids permeates into the material through various means. Exogenous hydrogen refers to hydrogen atoms acquiring hydrogen from their surrounding environment during service, such as in special environments like gas pipelines, high-temperature and high-pressure containers, and steam turbines, which accelerate hydrogen absorption. The harmful effects of endogenous hydrogen on metals range from affecting material quality to rendering the finished parts unusable. For large forgings, the impact of endogenous hydrogen is even more devastating. If hydrogen is not removed before processing, the finished part is like a time bomb, constantly vulnerable to destruction by the hydrogen present inside.

[0004] Forgings are key components in the machinery manufacturing industry, especially for heavy equipment such as rotors for nuclear and thermal power generators, thick plate rolling mill rolls, and crankshafts for large ships. Hot forming is a crucial process in their production. Due to their enormous size and weight, large parts are susceptible to severe defects such as segregation, shrinkage cavities, and porosity defects within the forgings, significantly impacting the forging quality. In particular, equipment damage caused by hydrogen hazard is difficult to predict and assess. Despite the adoption of vacuum melting and heat treatment hydrogen diversion technologies in engineering, the problem of hydrogen hazard cannot be completely eliminated. Typically, the solubility of hydrogen in solid steel is much lower than that in liquid steel. During the solidification of steel ingots, hydrogen precipitates from the steel. Some precipitates as singlet bubbles, some remains in various defects in the crystals, and some diffuses into high-temperature regions, forming hydrogen molecules in heterogeneous areas of large forgings. Once hydrogen atoms form hydrogen molecules, they will no longer diffuse, inducing the formation of white spots. This is because the diameter of a hydrogen atom is only 0.1 nm, but after recombination into a hydrogen molecule, the diameter is 0.29 nm, and the volume is 16 times that of a hydrogen atom, larger than the voids in the most common typical metallic crystal structures of face-centered cubic, body-centered cubic, and hexagonal close-packed structures. This ultimately leads to local enrichment of hydrogen and causes a loss of material mechanical properties. Therefore, dehydrogenation treatment of large forgings has always been an important step in their hot working process and a key factor leading to long manufacturing cycles and high production costs. The presence of hydrogen, even in small amounts, can have a significant impact on the plasticity and toughness of forgings, leading to the formation of white spots. Hydrogen dissolved in steel is the main cause of white spots, which can cause internal cracks to suddenly appear in forgings during processing or use, thus scrapping the forgings and causing major accidents or damage.

[0005] To reduce the hydrogen content in steel, it can be achieved either through vacuum degassing of molten steel or through dehydrogenation annealing of billets or forgings. The latter method is traditional and still widely used. In production, the hot hydrogen diffusion annealing process, based on traditional methods and experience, consumes a lot of energy and time. Some newer heat treatment processes can reduce the hydrogen content inside forgings by increasing specific holding times and temperatures; however, these heat treatment processes are all time-consuming, and the temperature and time ranges are subject to significant fluctuations due to material limitations. Summary of the Invention

[0006] The purpose of this invention is to provide a method for hydrogen diffusion in forgings based on ultrasonic-DC energy field assistance, so as to solve the hydrogen embrittlement problem caused by hydrogen in metals, such as white spots, and to provide an effective solution for removing hydrogen from inside metals in actual production.

[0007] The technical solution adopted in this invention is as follows:

[0008] The present invention proposes a method for hydrogen diffusion in forgings based on ultrasonic-DC energy field assistance, comprising the following steps:

[0009] S1. Place the heat-treated metal workpiece onto the support frame inside the water tank;

[0010] S2. Connect wires to both sides of the metal workpiece, and connect the other end of the wires to a DC power supply. Turn on the power.

[0011] S3. Pour salt solution into the water tank until it covers the metal workpiece;

[0012] S4. Fix ultrasonic transducers on both sides of the water tank, turn on the ultrasonic transducers, and remove hydrogen.

[0013] Furthermore, in step S2, the current density of the DC power supply is 0-10 A / m2, and the operating time is 1-120 min.

[0014] Furthermore, in step S3, the salt solution medium is an aqueous sodium chloride solution or an alcohol solution.

[0015] Furthermore, the concentration of the sodium chloride aqueous solution is 0-20%.

[0016] Furthermore, in step S4, the ultrasonic frequency of the ultrasonic transducer is 20-100kHz, and the action time is 1-120min.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] This invention can effectively remove most of the hydrogen atoms inside the metal in a short time, while reducing the heat treatment time and avoiding defects such as cracks and temper brittleness in forgings caused by heat treatment. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the wiring in the method of the present invention;

[0020] Figure 2 This is a schematic diagram of the stress-strain curves of the original, hydrogen-filled, and ultrasonic-DC energy field hydrogen-expanded samples of Embodiment 1 of the present invention.

[0021] Figure 3 This is a schematic diagram of the stress-strain curves of the original, hydrogen-filled, and ultrasonic-DC energy field hydrogen-expanded samples of Embodiment 2 of the present invention.

[0022] Figure 4 This is a schematic diagram of the stress-strain curves of the original, hydrogen-filled, and ultrasonic-DC energy field hydrogen-expanded samples of Embodiment 3 of the present invention.

[0023] In the attached drawings, the following labels are used: 1-water tank; 2-support frame; 3-workpiece; 4-salt solution medium; 5-DC power supply; 6-ultrasonic transducer. Detailed Implementation

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] The present invention proposes a method for hydrogen diffusion in forgings based on ultrasonic-DC energy field assisted, such as... Figure 1 As shown, the specific implementation process is as follows:

[0026] S1. Place the heat-treated metal workpiece onto the support frame inside the water tank;

[0027] S2. Connect wires to both sides of the metal workpiece, and connect the other end of the wires to a DC power supply. Turn on the power supply; the current density of the DC power supply is 0-10A / m2, and the operating time is 1-120min.

[0028] S3. Pour salt solution into the water tank until it covers the metal workpiece; the salt solution is an aqueous solution of sodium chloride (concentration of 0-20%) or an alcohol solution.

[0029] S4. Fix ultrasonic transducers on both sides of the water tank, turn on the ultrasonic transducers to remove hydrogen; wherein the ultrasonic frequency of the ultrasonic transducer is 20-100kHz, and the action time is 1-120min.

[0030] This invention accelerates the diffusion of hydrogen atoms within a metal forging placed in a solution by applying a superimposed energy field of ultrasound and direct current, effectively removing most of the hydrogen atoms from the forging's interior in a short time. The principle primarily involves the direct current and ultrasonic energy fields providing energy for hydrogen atoms to escape hydrogen traps, reducing the aggregation and confinement of hydrogen atoms by these traps; the ultrasound waves acting on the forging surface through the liquid medium generate ultrasonic cavitation, creating a high-frequency load on the forging surface and generating a stress gradient within the forging. This causes stress-induced diffusion of hydrogen atoms, thereby accelerating their diffusion out of the forging.

[0031] The present invention will be further illustrated below through specific embodiments:

[0032] Example 1

[0033] Four standard tensile specimens of SA508 were fabricated using wire cutting. One specimen was used for tensile testing as the initial data, while the remaining three were subjected to electrochemical hydrogen charging. The hydrogen charging solution was a 0.5 mol / L H₂SO₄ solution with two drops of Na₂S added as a poisoning agent. The charging current was 200 mA, and the charging time was 1 h. After hydrogen charging, one specimen was directly subjected to slow strain rate tensile testing; the other two specimens underwent ultrasonic-DC energy field assisted hydrogen ablation. One specimen was placed in a 20% sodium chloride aqueous solution with a current i = 200 mA, an ultrasonic frequency f = 40 kHz, and a time t = 30 min, denoted as "Ultrasonic-DC Hydrogen Ablation-1"; the other specimen was placed in a C₂H₅OH solution with an ultrasonic frequency f = 40 kHz and a time t = 40 min, denoted as "Ultrasonic-DC Hydrogen Ablation-2". After hydrogen ablation, the specimens were subjected to slow-rate tensile testing.

[0034] like Figure 2 As shown, after hydrogen charging, the yield strength increased from 274 MPa to 313 MPa, and the elongation decreased from 22.7% to 13.8%. After using the ultrasonic-DC energy field-assisted hydrogen diffusion method, the yield strength of ultrasonic-DC hydrogen diffusion-1 increased from 274 MPa to 338 MPa, and the elongation increased from 13.8% after hydrogen charging to 21.9%. After using the ultrasonic-DC energy field-assisted hydrogen diffusion method, the yield strength of ultrasonic-DC hydrogen diffusion-2 increased from 274 MPa to 303 MPa, and the elongation increased from 13.8% after hydrogen charging to 24.5%, exceeding the original elongation. Therefore, it can be concluded that this method can effectively recover the plasticity loss of metals.

[0035] Example 2

[0036] Three standard tensile specimens of 20CrMo were fabricated using wire cutting. One specimen was used for tensile testing as the initial data, while the other two were subjected to electrochemical hydrogen charging. The hydrogen charging solution was a 0.5 mol / L H₂SO₄ solution with two drops of Na₂S added as a poisoning agent. The charging current was 200 mA, and the charging time was 1 h. After hydrogen charging, one specimen was directly subjected to slow strain rate tensile testing; the other specimen underwent ultrasonic-DC energy field assisted hydrogen amplification by placing it in a 2% sodium chloride aqueous solution with a current i = 200 mA, an ultrasonic frequency f = 40 kHz, and a time t = 40 min. After 40 min, the specimen was subjected to a slow strain rate tensile test.

[0037] like Figure 3 As shown, after hydrogen filling, the yield strength increased from 398 MPa to 418 MPa, and the elongation decreased from 31.5% to 23.6%. After hydrogen expansion assisted by ultrasonic-DC energy field, the yield strength decreased from 398 MPa to 374 MPa, but the elongation increased from 23.6% after hydrogen filling to 29.3%, which was not much different from the original elongation.

[0038] Example 3

[0039] Three standard tensile specimens of 40 steel were machined using wire cutting. One specimen was used for tensile testing as the initial data, while the other two were subjected to electrochemical hydrogen charging. The hydrogen charging solution was a 0.5 mol / L H₂SO₄ solution with two drops of Na₂S added as a poisoning agent. The charging current was 200 mA, and the charging time was 1 h. After hydrogen charging, one specimen was directly subjected to slow strain rate tensile testing; the other specimen underwent ultrasonic-DC energy field assisted hydrogen amplification by placing it in a 2% sodium chloride aqueous solution with a current i = 200 mA, an ultrasonic frequency f = 40 kHz, and a time t = 30 min. After 30 min, the specimen was subjected to a slow strain rate tensile test.

[0040] like Figure 4 As shown, after hydrogen charging, the yield strength increased from 578 MPa to 611 MPa, and the elongation decreased from 21.9% to 14.7%. After hydrogen expansion assisted by ultrasonic-DC energy field, the yield strength increased from 578 MPa to 593 MPa, and the elongation increased from 14.7% after hydrogen charging to 17.9%, recovering most of the plasticity loss.

[0041] All matters not covered in this invention are common knowledge.

[0042] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for hydrogen diffusion in forgings based on ultrasonic-DC energy field assisted process, characterized in that: Includes the following steps: S1. Place the heat-treated metal workpiece onto the support frame inside the water tank; S2. Connect wires to both sides of the metal workpiece, and connect the other end of the wires to a DC power supply. Turn on the power. S3. Pour salt solution into the water tank until it covers the metal workpiece; S4. Fix ultrasonic transducers on both sides of the water tank, turn on the ultrasonic transducers, and remove hydrogen. In step S2, the current density of the DC power supply is 0-10 A / m. 2 The action time is 1-120 min; In step S3, the salt solution medium is an aqueous sodium chloride solution; In step S4, the ultrasonic frequency of the ultrasonic transducer is 20-100kHz, and the action time is 1-120min.

2. The method for hydrogen diffusion in forgings based on ultrasonic-DC energy field assisted according to claim 1, characterized in that: The concentration of the sodium chloride aqueous solution is 0-20%.

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