CN102814436B

CN102814436B - Method for performing roll forming on screw thread by medium-high frequency induction heating and axial feed

Info

Publication number: CN102814436B
Application number: CN201210303574.7A
Authority: CN
Inventors: 张大伟; 赵升吨; 李泳峄; 范淑琴
Original assignee: Xian Jiaotong University
Current assignee: Shaanxi Gezhi Jingcheng Intelligent Manufacturing Co ltd
Priority date: 2012-08-24
Filing date: 2012-08-24
Publication date: 2014-07-02
Anticipated expiration: 2032-08-24
Also published as: CN102814436A

Abstract

A method for rolling and forming threaded parts with medium and high-frequency induction heating in axial direction. Firstly, the workpiece is clamped, and the surface of the end area of the formed thread section on the workpiece is heated. The thread lead angle on the surface of the roll forming die is different from the thread lead angle of the threaded part of the rolled part. The roll forming workpiece is fed axially. After the axial feed roll forming starts, it enters the middle and high frequency induction heating under the axial feed motion. The forming area of the device is continuously heated, and the rolling die completes the rolling forming of the thread on the workpiece. The medium and high frequency induction heater is between the rolling forming mold and the clamping position of the workpiece, and the medium and high frequency induction heater is only used for rolling deformation that is about to start. In the part of the forming area, the local area of the surface where plastic deformation occurs is heated. The invention has the advantages of small thread forming force, less heat loss, and energy saving.

Description

A kind of method of medium-high frequency eddy-current heating axial feed rollforming screw element

Technical field

The invention belongs to advanced material forming technique field, be specifically related to a kind of method of medium-high frequency eddy-current heating axial feed rollforming screw element.

Background technology

Screw element is connection and driving parts crucial in machinery manufacturing industry, and at space flight machinery, lathe, instrument and meter, automobile and the application of various vehicle are very extensive.Conventionally, need the part of machining screw to account for the more than 60% of machine part quantity.

The processing of thread part, the problem such as ubiquity labour intensity is large, production efficiency is low, cost is high and Product Precision is low.Along with developing rapidly of Aeronautics and Astronautics, automobile and mechanical industry, the demand of all kinds of thread parts increases day by day, constantly appears at the demand of working under high speed, large load, moving load condition, and intensity, the precision of this double thread part are had higher requirement.Traditional cutting working method not only efficiency is low, and owing to cutting off metallic fiber, has reduced the quality of part, is difficult to be suitable for this needs.Thread rolling processing method be a kind of high-quality, efficiently, advanced chipless process cheaply, the accurate thread part that high efficiency and high-mechanical property are required, demonstrates great superiority.But current screw thread cold rolling method has strict requirement to moulding material hardness and percentage elongation, be difficult to moulding material hardness and be greater than the screw element that HRC37, percentage elongation are less than 8%; Material for material percentage elongation between 8% ~ 12%, is difficult to into the high-quality screw element of rollforming.And for the large material of resistance of deformation under room temperature, not only shaping load is large for its screw thread cold rolling shaping process, material flow difficulties, and former transmission system and integral rigidity also face great challenge.

Warm working has been concentrated the advantage of cold forming and heat forming technology, not only can effectively reduce resistance of deformation, reduce material hardness, improves metal material plastic forming ability; And avoided hot forming energy consumption large, easily produced overheated, oxidation, decarburization, and the shortcoming such as allowance is large; Can obtain good product surface quality and higher dimensional accuracy.At present, due to the plurality of advantages of warm working, numerous scholars have carried out research widely to this technique, be applied to a lot of production occasions and obtained satisfied effect, such as warm drawing and forming, warm-extrusion forming, Warm forging precise forming etc., but also Warm Forming Technology is not applied in the plastic working technique of axial feed rollforming screw element.

Summary of the invention

In order to overcome the shortcoming of above-mentioned prior art, the object of the present invention is to provide a kind of method of medium-high frequency eddy-current heating axial feed rollforming screw element, screw element shaping load is little, material flowability can be good, can rapidoprint resistance of deformation large, hardness is large and thin and long shafts screw element, has advantages of that forming accuracy and surface quality are high, production efficiency is high, the range of work is wide, highly versatile.

In order to achieve the above object, the technical scheme that the present invention takes is:

A method for medium-high frequency eddy-current heating axial feed rollforming screw element, comprises the steps:

Step 1, clamping workpiece 2, workpiece 2 by front top 1 and back centre 3 clamp, the axis that makes workpiece 2 is with the axis of two rolling dies 5 in same level, two rolling die 5 axis are parallel, are symmetrically distributed in workpiece 2 both sides;

Step 2, the thread segment end regions surface local that is shaped on workpiece 2 heating, is specially:

2.1, workpiece 2 is to rolling die 5 direction feedings, the thread segment that is shaped on workpiece 2 enters in medium-high frequency induction heater 4, medium-high frequency induction heater 4 is configured between rolling die 5 and workpiece 2 clamping positions, the thread segment that is shaped on workpiece 2 aligns near rolling die 5 one end with medium-high frequency induction heater 4 near rolling die 5 one end

Hot zone length is that the length of medium-high frequency induction heater 4 bringing-up section a is L _a, medium-high frequency induction heater 4 is L near rolling die 5 one end with the length of space section b between adjacent rolling die 5 end faces _b, the length of rolling die 5 squeezing thread section c is L _c, length L _al _band L _cmeet formula L _a=L _b<L _c(1);

2.2, medium-high frequency induction heater 4 is started working, and the surface heating layer depth Δ of thread segment in bringing-up section a that be shaped on workpiece 2 should meet formula

Δ = \frac{d_{Z} - d_{1} + (1.5 ~ 2.5) (d - d_{1})}{2};

In formula: d _zfor blank diameter before the rolling of blank threaded portion; d ₁for shaping screw thread path; D is shaping Major Diam;

2.3, in bringing-up section a, the temperature in the surface heating layer depth Δ of workpiece reaches predetermined forming temperature T, and its heat time is t,

Forming temperature T is more than deformable material blue shortness district temperature, fully carries out the warm working temperature below the temperature of recrystallization; Or the hot forming temperature more than the temperature of fully carrying out recrystallization; Heat time t determines that the method for the shortest heat time is determined when adopting electromagnetic induction heating in forging, and wherein in bringing-up section a, workpiece centre temperature and the poor Δ T of surface layer temperatures select in 200 ℃ ~ (T-50 ℃) scope;

Step 3, workpiece 2 bringing-up section enters space section b between medium-high frequency induction heater 4 and rolling die 5,

Workpiece 2 bringing-up section aligns with rolling die 5 end faces near rolling die 5 one end;

Step 4, continuous medium-high frequency eddy-current heating and axial feed, completed the rollforming of screw thread on workpiece 2 by rolling die 5,

When the thread segment that is shaped on workpiece 2 all departs from after medium-high frequency induction heater 4, medium-high frequency induction heater 4 quits work; Two synchronous rotating in same directions of rolling die 5, two rolling dies 5 are made radial feed simultaneously, and in the time that rolling die 5 completes radially total feed amount S, rolling die 5 stops radial feed, only rotates;

Surface heating layer depth Δ in bringing-up section a should meet formula workpiece 2 axial feed velocity v _ashould meet formula

v_{a} = \frac{ΔL}{t};

In formula: Δ L is that workpiece 2 often turns axial feeding, Δ L is determined by difference and rolling die 5 rotating speeds of the lead angle on rolling die 5 surfaces and the lead angle of the screw element that is formed, rolling die 5 radial feed speed υ _rshould meet formula

Step 5, workpiece 2 by front top 1 and back centre 3 clamp and oppositely exit simultaneously, discharging.

The present invention organically combines medium-high frequency eddy-current heating and axial feed rollforming screw thread, realizes the long screw element of axial feed rollforming high strength, high hardness material; Medium-high frequency induction heater, between rollforming mould and clamping workpiece position, only heats the partially-formed region that is about to beginning rolling distortion; Rollforming die surface lead angle is with the screw element lead angle difference that is rolled part, rollforming workpiece axial feed; Under workpiece axial feed motion, enter the shaped region laser heating of medium-high frequency induction heater; Only to there is the surface local region heating of plastic deformation in medium-high frequency induction heater; Reduce thermal loss, save the energy; Can reduce material deformation drag, improve metal plastic deformation ability; Machinable material resistance of deformation is large, hardness large and thin and long shafts screw element.

Accompanying drawing explanation

Fig. 1 is flow chart of the present invention.

Fig. 2 is equipment therefor connection diagram of the present invention.

Fig. 3 is the front view in medium-high frequency induction heater of the present invention and rolling die region.

Fig. 4 is workpiece 2 of the present invention and rolling die 5 layouts and motion signal.

The specific embodiment

Below in conjunction with drawings and Examples, the present invention is described in detail.

Embodiment

It is 42CrMo high strength steel that the present embodiment adopts the material of workpiece 2, and the yield strength under 25 ° of C of room temperature is 1320MPa, and tensile strength is 1510MPa.

With reference to Fig. 1, a kind of method of medium-high frequency eddy-current heating axial feed rollforming screw element, comprises the steps:

2.1, workpiece 2 is to rolling die 5 direction feedings, the thread segment that is shaped on workpiece 2 enters in medium-high frequency induction heater 4, with reference to Fig. 2, medium-high frequency induction heater 4 is configured between rolling die 5 and workpiece 2 clamping positions, the thread segment that is shaped on workpiece 2 aligns near rolling die 5 one end with medium-high frequency induction heater 4 near rolling die 5 one end

With reference to Fig. 3, hot zone length is that the length of medium-high frequency induction heater 4 bringing-up section a is L _a, medium-high frequency induction heater 4 is L near rolling die 5 one end with the length of space section b between adjacent rolling die 5 end faces _b, the length of rolling die 5 squeezing thread section c is L _c, length L _a, L _band L _cmeet formula L _a=L _b<L _c;

2.2, medium-high frequency induction heater is started working; The surface heating layer depth Δ of thread segment in bringing-up section a that be shaped on workpiece should meet formula

In formula: d _z, blank diameter before the rolling of blank threaded portion; d ₁, shaping screw thread path; D, shaping Major Diam;

Forming temperature T is more than deformable material blue shortness district temperature, fully carries out the warm working temperature below the temperature of recrystallization, is specially 700 ℃; Heat time t determines that the method for the shortest heat time is determined when adopting electromagnetic induction heating in forging, and wherein in bringing-up section a, workpiece centre temperature and the poor Δ T of surface layer temperatures select within the scope of 200 ℃ ~ 650 ℃;

When the thread segment that is shaped on workpiece 2 all departs from after medium-high frequency induction heater 4, medium-high frequency induction heater 4 quits work; Two synchronous rotating in same directions of rolling die 5, two rolling dies 5 are made radial feed simultaneously, and with reference to Fig. 4, in the time that rolling die 5 completes radially total feed amount S, rolling die 5 stops radial feed, only rotates;

Surface heating layer depth Δ in bringing-up section a should meet formula

workpiece 2 axial feed velocity v _ashould meet formula

v_{a} = \frac{ΔL}{t};

Claims

1. A method for medium and high frequency induction heating axial feed rolling and forming threaded parts, characterized in that, comprising the steps:

Step 1, clamp the workpiece (2), the workpiece (2) is clamped by the front top (1) and the rear top (3), so that the axis of the workpiece (2) is on the same level as the axes of the two rolling dies (5) , the axes of the two rolling dies (5) are parallel and symmetrically distributed on both sides of the workpiece (2);

Step 2, the surface of the end area of the formed thread section on the workpiece (2) is locally heated, specifically:

2.1. The workpiece (2) is fed in the direction of the rolling die (5), and the formed thread section on the workpiece (2) enters the medium and high frequency induction heater (4), and the medium and high frequency induction heater (4) is arranged in the rolling die ( 5) Between the clamping position of the workpiece (2), the end of the formed thread section on the workpiece (2) close to the rolling die (5) is aligned with the end of the medium-high frequency induction heater (4) close to the rolling die (5),

The length of the heating area is the length of the heating section a of the medium and high frequency induction heater (4), which is L _a , between the end of the medium and high frequency induction heater (4) close to the rolling die (5) and the end face of the adjacent rolling die (5) The length of the gap section b is L _b , the length of the rolling thread section c of the rolling die (5) is L _c , and the lengths L _a , L _b and L _c satisfy the formula L _a =L _b <L _c ;

2.2. The medium and high frequency induction heater (4) starts to work, and the surface heating layer depth Δ of the formed thread section on the workpiece (2) in the heating section a should satisfy the formula

Δ = \frac{d_{z} - d_{1} + (1.5 ~ 2.5) (d - d_{1})}{2};

In the formula: d _Z is the diameter of the billet before rolling in the thread area of the billet; d ₁ is the small diameter of the formed thread; d is the major diameter of the formed thread;

2.3. The temperature within the depth Δ of the surface heating layer of the workpiece in the heating section a reaches the predetermined forming temperature T, and the heating time is t.

The forming temperature T is the warm forming temperature above the blue brittle zone temperature of the deformed material and below the temperature of sufficient recrystallization; or the hot forming temperature above the temperature of sufficient recrystallization; the heating time t is based on the electromagnetic induction used in forging production The method of determining the shortest heating time during heating is determined, wherein the temperature difference between the center temperature of the workpiece and the surface layer temperature ΔT in the heating section a is selected within the range of 200°C to (T-50°C);

Step 3, the heated section of the workpiece (2) enters the gap section b between the medium and high frequency induction heater (4) and the rolling die (5),

One end of the heated section of the workpiece (2) close to the rolling die (5) is aligned with the end face of the rolling die (5);

Step 4, continuous medium and high frequency induction heating and axial feeding, the rolling die (5) completes the rolling forming of the thread on the workpiece (2),

When the formed thread sections on the workpiece (2) are all separated from the medium and high frequency induction heater (4), the medium and high frequency induction heater (4) stops working; the two rolling dies (5) rotate in the same direction synchronously, and the two rolling dies (5) Perform radial feed at the same time. When the rolling die (5) completes the total radial feed S, the rolling die (5) stops radial feeding and only performs rotational movement;

The surface heating layer depth Δ in the heating section a should satisfy the formula

The workpiece (2) axial feed speed v _a should satisfy the formula

v_{a} = \frac{Δ L}{t};

In the formula: ΔL is the axial feed per revolution of the workpiece (2), and ΔL is determined by the difference between the thread lead angle on the surface of the rolling die (5) and the thread lead angle of the threaded part to be formed and the rotational speed of the rolling die (5) Sure,

Rolling die (5) radial feed speed v _r should satisfy the formula

Step 5, the workpiece (2) is clamped by the front center (1) and the rear center (3) and withdraws in reverse at the same time, unloading.