Ultrasonic impact device based method for high-energy composite modification of inner layer of small hole

Abstract

The present invention relates to the technical field of small hole strengthening. Disclosed is an ultrasonic impact device based method for high-energy composite modification of an inner layer of a small hole. An ultrasonic impact device is comprised; the ultrasonic impact device comprises an amplitude-change pole, an ultrasonic transducer and an ultrasonic generator; the ultrasonic generator is connected to the ultrasonic transducer; a punching machine fixture is provided at the top of the ultrasonic transducer; the lower portion of the ultrasonic transducer is connected to the amplitude-change pole; and an ultrasonic vibration punch is provided at the bottom of the amplitude-change pole. The high-energy composite modification method comprises the following steps: S1, carrying out carburizing heat treatment on the inner wall of a small hole to form a carburized layer; S2, carrying out nitriding heat treatment on the inner wall of the small hole to form a nitrided layer; and S3, carrying out ultrasonic impact modification treatment on the inner wall of the small hole to form effective nanocrystals. In the present invention, by using the structure and the method, an ultrahigh-hardness gradient field, an ultrahigh residual compressive stress field and the effective nanocrystals are constructed on the inner surface layer of the small hole by means of a composite surface modification technology which combines phase change strengthening and strain strengthening.

Description

A high-energy composite modification method for the inner layer of a small hole based on an ultrasonic impact device Technical Field

[0001] The invention relates to the technical field of small hole strengthening, in particular to a high-energy composite modification method of a small hole inner layer based on an ultrasonic impact device. Background Art

[0002] Small holes are a key feature of mechanical equipment, providing connection and support for parts. During machining, discontinuous tool marks can form on the inner walls of small holes, creating stress concentrations that can lead to fatigue failure. When small holes contact and slide against shafts, the inner walls of small holes are susceptible to wear. These issues can generally be overcome by strengthening the inner walls of small holes and increasing their hardness.

[0003] At present, the strengthening processes for small holes mainly include cold extrusion strengthening of slotted bushings, laser shock strengthening, ultrasonic shock strengthening, etc. Patent CN112662965B introduces a process for strengthening assembly holes by cold extrusion of slotted bushings. This process extrudes the slotted bushing, and the extrusion force is evenly transmitted to the hole wall through the slotted bushing, forming a uniform residual stress on the hole wall. Patent CN102517413 first uses a large-spot, high-energy laser, and then uses a small-spot, low-energy laser to impact strengthen the surface of the small hole component to be opened twice, so that better residual compressive stress is generated from the surface to a deeper depth, and finally punching is performed. Patent CN113977190B introduces an ultrasonic vibration-assisted hole extrusion strengthening process, which combines ultrasonic vibration technology with hole extrusion strengthening technology, and improves the surface quality of the hole wall by increasing the number of times the extrusion core rod extrudes the hole wall. However, these technologies use plastic deformation processes to strengthen the inner wall of the small hole, which has limited effect on strengthening the inner wall of the small hole.

[0004] Therefore, it is necessary to provide a high-energy composite modification method for the inner layer of a small hole based on an ultrasonic impact device to solve the above problems.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to provide a high-energy composite modification method for the inner layer of a small hole based on an ultrasonic impact device, and to construct an ultra-high hardness gradient field, an ultra-high residual compressive stress field, and effective nanocrystals in the inner surface layer of the small hole through a composite surface modification technology that combines phase change strengthening with strain strengthening.

[0007] To achieve the above-mentioned objectives, the present invention provides a high-energy composite modification method for the inner layer of a small hole based on an ultrasonic impact device, comprising an ultrasonic impact device, wherein the ultrasonic impact device comprises a horn, an ultrasonic transducer, and an ultrasonic generator, wherein the ultrasonic generator is connected to the ultrasonic transducer, a stamping machine fixture is provided on the top of the ultrasonic transducer, the bottom of the ultrasonic transducer is connected to the horn, and an ultrasonic vibration punch is provided at the bottom of the horn;

[0008] The high-energy composite modification method comprises the following steps:

[0009] S1: Carburizing heat treatment is performed on the inner wall of the small hole to form a carburized layer;

[0010] S2: Performing nitriding heat treatment on the inner wall of the small hole to form a nitriding layer;

[0011] S3: The inner wall of the pore is subjected to ultrasonic impact modification treatment to form effective nanocrystals.

[0012] Preferably, the diameter of the small hole is set in the range of 3mm-10mm.

[0013] Preferably, in step S1, the part is made of medium or low carbon steel, the inner wall of the small hole is subjected to carburizing heat treatment, and then quenched, cold treated, and tempered multiple times to eliminate retained austenite, the retained austenite content is less than 3%, and the carburized layer thickness is 1.0 to 1.5 mm;

[0014] The parts are made of high carbon steel and need to be quenched, cold treated and tempered multiple times to eliminate retained austenite and reduce the retained austenite content to less than 3%.

[0015] Preferably, in step S2, after the nitriding heat treatment, the nitrided layer has a thickness of 0.08 to 0.1 mm and a hardness greater than 1000 HV.

[0016] Preferably, in step S3, the following steps are specifically included:

[0017] S31: Based on the properties of the inner surface of the small hole after carburizing heat treatment and nitriding heat treatment, the extrusion interference range of the inner wall of the small hole after phase transformation strengthening is between 0.01% and 0.04%. The expression of the extrusion interference Δd is:

[0018] Where D0 is the diameter of the small hole before ultrasonic impact expansion, and D is the diameter of the small hole after ultrasonic impact expansion;

[0019] S32: Determine the extrusion contact area S between the punch and the inner wall of the small hole based on the extrusion interference Δd and the shape of the ultrasonic vibration punch. The expression is:

[0020] Where r is the transition fillet radius, θ is the angle between L and the hole wall,

[0021] Calculate L, where L is the straight-line distance between the ultrasonic vibration punch and the hole wall at the beginning and end of contact, and the expression is:

[0022] S33: Calculate F1, where F1 is the extrusion force required for the extrusion deformation of the material per unit area, and the expression is:

[0023] F1=ΔSσ S

[0024] Where ΔS is the unit area of ​​the material, σ s It is the surface yield strength of the material after carburizing and nitriding treatment;

[0025] S34: Calculate the total extrusion force F. The total extrusion force F transmitted from the machine tool to the ultrasonic vibration punch is expressed as:

[0026] Where σ s is the surface yield strength of the material after carburizing and nitriding treatment, K1 is the correction coefficient of the total extrusion pressure F, ranging from 0.7 to 1.0, r is the transition fillet radius, Δd is the extrusion interference, and S is the contact area between the ultrasonic vibration punch and the inner wall of the small hole;

[0027] S35: Calculate the transition fillet radius r,

[0028] S36: performing ultrasonic impact modification on the inner wall of the small hole after phase change strengthening based on the ultrasonic impact modification process parameters of steps S31-S35.

[0029] Therefore, the present invention adopts the above-mentioned high-energy composite modification method of the inner layer of the small hole based on the ultrasonic impact device, and constructs an ultra-high hardness gradient field, an ultra-high residual compressive stress field, and effective nanocrystals in the inner surface of the small hole through a composite surface modification technology that combines phase change strengthening and strain strengthening.

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG1 is a diagram of an ultrasonic extrusion modification device for a high-energy composite modification method of a small hole inner layer based on an ultrasonic impact device according to the present invention;

[0032] FIG2 is an enlarged view of a local extrusion contact of a high-energy composite modification method for the inner layer of a small hole based on an ultrasonic impact device according to the present invention;

[0033] FIG3 is a schematic diagram of phase change strengthening of the surface layer of the inner wall of a small hole according to a high-energy composite modification method of the inner layer of a small hole based on an ultrasonic impact device of the present invention;

[0034] The attached drawings are marked with: 1. Ultrasonic vibration punch; 2. Amplitude transformer; 3. Ultrasonic transducer; 4. Ultrasonic generator; 5. Stamping machine fixture. 2. Specific implementation methods

[0035] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0036] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0037] The words “include” or “comprising” and similar words used in the present invention mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of also including other elements. The orientation or position relationship indicated by the terms “inside”, “outside”, “upper”, “lower”, etc. is based on the orientation or position relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention. When the absolute position of the described object changes, the relative position relationship may also change accordingly. In the present invention, unless otherwise clearly stipulated and limited, the terms such as “attachment” should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral whole; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0038] As shown in Figures 1 to 3, the present invention provides a high-energy composite modification method for the inner layer of a small hole based on an ultrasonic impact device, including an ultrasonic impact device, which includes a horn 2, an ultrasonic transducer 3 and an ultrasonic generator 4. The ultrasonic generator 4 is connected to the ultrasonic transducer 3, and a stamping machine fixture 5 is provided on the top of the ultrasonic transducer 3. The bottom of the ultrasonic transducer 3 is connected to the horn 2, and an ultrasonic vibration punch 1 is provided at the bottom of the horn 2; the diameter range of the processed small hole is set to 3mm-10mm.

[0039] The high-energy composite modification method comprises the following steps:

[0040] S1: Carburizing heat treatment is performed on the inner wall of the small hole to form a carburized layer;

[0041] In step S1, the part is made of medium or low carbon steel, and the inner wall of the small hole is subjected to carburizing heat treatment, and then quenching, cold treatment, and multiple tempering to eliminate retained austenite. The retained austenite content is less than 3%, and the carburized layer thickness is 1.0 to 1.5 mm.

[0042] The parts are made of high carbon steel and need to be quenched, cold treated and tempered multiple times to eliminate retained austenite and reduce the retained austenite content to less than 3%.

[0043] S2: The inner wall of the small hole is subjected to nitriding heat treatment to form a nitriding layer; in step S2, before the inner wall of the small hole is subjected to gas nitriding, the inner wall of the small hole is exposed, and the remaining parts are coated with anti-nitriding coating, which is removed after the nitriding heat treatment. After the nitriding heat treatment, the nitriding layer has a thickness of 0.08 to 0.1 mm and a hardness greater than 1000 HV.

[0044] S3: Performing ultrasonic impact modification treatment on the inner wall of the small hole to form effective nanocrystals; specifically comprising the following steps:

[0045] S31: Based on the properties of the inner surface of the small hole after carburizing heat treatment and nitriding heat treatment, the extrusion interference range of the inner wall of the small hole after phase transformation strengthening is between 0.01% and 0.04%. The expression of the extrusion interference Δd is:

[0046] Where D0 is the diameter of the small hole before ultrasonic impact expansion, and D is the diameter of the small hole after ultrasonic impact expansion;

[0047] S32: Determine the extrusion contact area S between the punch and the inner wall of the small hole based on the extrusion interference Δd and the shape of the ultrasonic vibration punch. The expression is:

[0048] Where r is the transition fillet radius, θ is the angle between L and the hole wall,

[0049] Calculate L, where L is the straight-line distance between the ultrasonic vibration punch and the hole wall at the beginning and end of contact, and the expression is:

[0050] S33: Calculate F1, where F1 is the extrusion force required for the extrusion deformation of the material per unit area, and the expression is:

[0051] F1=ΔSσ S

[0052] Where ΔS is the unit area of ​​the material, σ s It is the surface yield strength of the material after carburizing and nitriding treatment. In order to extend the service life of the ultrasonic vibration punch, F1 should be as small as possible while meeting the requirements.

[0053] S34: Calculate the total extrusion force F. The total extrusion force F transmitted from the machine tool to the ultrasonic vibration punch is expressed as:

[0054] Where σ s is the surface yield strength of the material after carburizing and nitriding treatment, K1 is the correction coefficient of the total extrusion pressure F, and its value range is 0.7 to 1.0, r is the transition fillet radius, Δd is the extrusion interference, and S is the contact area between the ultrasonic vibration punch and the inner wall of the small hole. The role of the coefficient K1 is to empirically correct the parameters to obtain a more appropriate extrusion force F.

[0055] S35: Calculate the transition fillet radius r,

[0056] S36: performing ultrasonic impact modification on the inner wall of the small hole after phase change strengthening based on the ultrasonic impact modification process parameters of steps S31-S35.

[0057] Specific usage:

[0058] The ultrasonic vibration device is mounted on the punching machine fixture 5. The connection between the ultrasonic vibration punch 1 and the horn 2 allows for replacement of punches of different diameters. During operation, the punch is controlled by the punching machine to press downward with a force F at a constant speed. The ultrasonic vibration device vertically extrudes and expands the inner wall of the small hole, while also ultrasonically vibrating and modifying it, causing plastic deformation and strain strengthening of the inner surface of the small hole, resulting in ultra-high hardness.

[0059] Therefore, the present invention adopts the above-mentioned high-energy composite modification method of the inner layer of the small hole based on the ultrasonic impact device, and constructs an ultra-high hardness gradient field, an ultra-high residual compressive stress field, and effective nanocrystals in the inner surface of the small hole through a composite surface modification technology that combines phase change strengthening and strain strengthening.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-energy composite modification method for the inner layer of a small hole based on an ultrasonic impact device, characterized in that: The ultrasonic impact device comprises an horn, an ultrasonic transducer and an ultrasonic generator, wherein the ultrasonic generator is connected to the ultrasonic transducer, a punching machine fixture is arranged on the top of the ultrasonic transducer, the lower part of the ultrasonic transducer is connected to the horn, and an ultrasonic vibration punch is arranged on the bottom of the horn; The high energy composite modification method comprises the following steps: S1: Carburizing heat treatment is performed on the inner wall of the small hole to form a carburized layer; S2: Perform nitriding heat treatment on the inner wall of the small hole to form a nitriding layer; S3: The inner wall of the small hole is subjected to ultrasonic impact modification treatment to form effective nanocrystals.

2. According to claim 1, a high-energy composite modification method for the inner layer of a small hole based on an ultrasonic impact device is characterized in that: The diameter range of the small hole is set to be 3mm-10mm.

3. According to claim 2, a high-energy composite modification method for the inner layer of a small hole based on an ultrasonic impact device is characterized in that: In step S1, the material of the part is medium or low carbon steel, the inner wall of the small hole is subjected to carburizing heat treatment, and then quenching, cold treatment, and multiple tempering are performed to eliminate residual austenite, the residual austenite content is less than 3%, and the thickness of the carburized layer is 1.0 to 1.5 mm; The parts are made of high carbon steel and need to be quenched, cold treated and tempered multiple times to eliminate residual austenite and reduce the residual austenite content to less than 3%.

4. The high-energy composite modification method of the inner layer of a small hole based on an ultrasonic impact device according to claim 3 is characterized in that: In step S2, after the nitriding heat treatment, the nitriding layer has a thickness of 0.08-0.1 mm and a hardness greater than 1000 HV.

5. The high-energy composite modification method of the inner layer of a small hole based on an ultrasonic impact device according to claim 4 is characterized in that: In step S3, the following steps are specifically included: S31: Based on the performance of the inner surface of the small hole after carburizing heat treatment and nitriding heat treatment, the inner wall of the small hole after phase transformation strengthening The applicable extrusion interference range is between 0.01% and 0.04%, and the expression of extrusion interference Δd is: Where D0 is the diameter of the small hole before ultrasonic impact expansion, and D is the diameter of the small hole after ultrasonic impact expansion; S32: Based on the extrusion interference Δd and the shape of the ultrasonic vibration punch, the extrusion contact area S between the punch and the inner wall of the small hole is determined. The expression is: Where r is the transition fillet radius, θ is the angle between L and the hole wall, Calculate L, where L is the straight-line distance between the ultrasonic vibration punch and the hole wall at the beginning and end of contact. The expression is: S33: Calculate F1, where F1 is the extrusion force required for extrusion deformation of the material per unit area, and the expression is: F1=ΔSσ S In the formula, ΔS is the unit area of ​​the material, σ s It is the surface yield strength of the material after carburizing and nitriding treatment; S34: Calculate the total extrusion pressure F. The total extrusion pressure F transmitted from the machine tool to the ultrasonic vibration punch is expressed as: In the formula, σ s is the surface yield strength of the material after carburizing and nitriding treatment, K1 is the correction coefficient of the total extrusion pressure F, ranging from 0.7 to 1.0, r is the transition fillet radius, Δd is the extrusion interference, and S is the contact area between the ultrasonic vibration punch and the inner wall of the small hole; S35: Calculate the transition fillet radius r, S36: performing ultrasonic impact modification on the inner wall of the small hole after phase change strengthening based on the ultrasonic impact modification process parameters of steps S31-S35.

Images