CN111229905B

CN111229905B - Hot stamping and quenching integrated processing method based on hydraulic forming device

Info

Publication number: CN111229905B
Application number: CN202010029221.7A
Authority: CN
Inventors: 王会廷; 吴琦; 孔建非; 陈其伟; 沈晓辉; 曹杰; 潘红波
Original assignee: Anhui University of Technology AHUT
Current assignee: Anhui University of Technology AHUT
Priority date: 2020-01-09
Filing date: 2020-01-09
Publication date: 2021-06-11
Anticipated expiration: 2040-01-09
Also published as: CN111229905A

Abstract

The invention discloses a hot stamping and quenching integrated processing method based on a hydraulic forming device, belonging to the technical field of hot stamping, and the method comprises the following steps: placing the blank in a heating furnace for heat preservation to enable the blank to become austenitized; then quickly moving the blank onto a die, keeping the liquid level of liquid in a liquid pool of the hydraulic die at a certain height and ensuring that the liquid does not contact a forming part after the die is pressed; the die is quickly closed, meanwhile, a hydraulic press connected with the liquid pool is started, the piston moves downwards, so that liquid in the liquid pool contacts a high-temperature forming piece, a certain pressure is quickly formed and maintained, and quenching is carried out; and after quenching is finished, keeping the pressure for a period of time, moving the piston upwards, and opening the die to finally obtain a formed piece. The invention can realize the quenching of a high-temperature forming piece in the die, so that the forming piece can obtain a complete martensite structure, the high strength of the forming piece is ensured, and the dimensional accuracy of the forming piece is improved.

Description

Hot stamping and quenching integrated processing method based on hydraulic forming device

The technical field is as follows:

the invention belongs to the technical field of metal hot working, relates to a hot stamping method controlled by quenching, and particularly relates to a hot stamping and quenching integrated treatment method based on a hydraulic forming device. The method realizes the integration of hot stamping and quenching by using the hydraulic forming device, and ensures the strength uniformity of the final formed piece.

Technical background:

in recent years, the safety performance of passenger cars can be obviously improved by adopting advanced high-strength steel plate to form car body parts, thereby realizing the light weight of the car body and reducing the oil consumption. For the forming of high-strength steel by traditional cold stamping, a vehicle body part is easy to break in the forming process and easy to rebound, and the subsequent vehicle body assembly is influenced. For high-strength steel with the strength exceeding 1000MPa, the traditional cold stamping process is usually not free from the heart, so that the hot stamping technology is generated due to transportation, and the limitation that the ultrahigh-strength steel plate is difficult to form at normal temperature can be solved.

The hot stamping technology is an effective way for obtaining ultrahigh-strength stamped parts, and the principle of the technology is that a high-strength plate is heated to the temperature range of austenite, the high-strength plate is rapidly moved to a die and rapidly stamped, the parts are quenched and cooled (and certain cooling speed is ensured) after being held and pressed for a period of time, and finally the microstructure of a formed part is converted from austenite to martensite, so that the formed part with the strength of more than 1500MPa is obtained.

The purpose of quenching is to make the super-cooled austenite transform into martensite or bainite to obtain martensite or bainite structure, during the quenching process, the cooling speed must be higher than the critical cooling speed of the steel, not only the cooling speed is ensured to meet the quenching requirement to ensure the transformation from austenite to martensite, but also the temperature of each part during the cooling process of the high-temperature formed part cannot be greatly different, if the difference is too large, the part which is higher than the critical cooling speed can be transformed into a martensite, and the core which is lower than the critical cooling speed can not be transformed into the martensite. However, if the cooling rate is too high, the inside of the formed article is subjected to internal stress due to uneven expansion and contraction with heat, and the formed article may be distorted or cracked when the internal stress is so high that an appropriate cooling method must be selected.

Most of the ultrahigh-strength hot stamping processes developed at present complete stamping on a traditional stamping machine or a hydraulic machine, and the subsequent quenching process is mainly realized by utilizing a solid conduction quenching mode of a hot steel plate in contact with a die and ensuring the die temperature by introducing cooling water into the die in order to prevent the die temperature from rising. By adopting the solid contact quenching mode, some high-strength steels can not reach the critical cooling speed, so that complete martensite structures can not be obtained after quenching, and the final formed piece has the defects of uneven strength and the like.

The invention content is as follows:

the invention aims to provide a hot stamping and quenching integrated processing method based on a hydraulic forming device. The hydraulic forming liquid pool and female die is communicated with a hydraulic cylinder with a piston through a pipeline, liquid for quenching is filled in the hydraulic cylinder, when the piston moves downwards to the bottom, the liquid in the liquid pool is filled, the piston moves upwards, and the liquid in the liquid pool and the hydraulic cylinder is restored to the initial state. The invention can realize the integrated functions of hot stamping and quenching of the high-strength plate in the die, and the strength is more uniform while the high strength of the final formed part is maintained.

The invention provides a hot stamping and quenching integrated processing method based on a hydraulic forming device, which comprises the following specific steps:

(1) placing the blank in a heating furnace, and austenitizing the blank at a certain heat preservation temperature for a certain heat preservation time. The austenitizing temperature of the blank is 20-50 ℃ higher than that of Ar3, the time for rapidly moving the blank onto a die is 3-8s, and the temperature is reduced by about 10-20 ℃; ensuring that the temperature for starting stamping of the blank is not lower than Ar3+10 ℃.

(2) Rapidly moving the blank obtained in the step (1) to a die of a hydraulic forming device, wherein the liquid amount in a liquid pool of the die is ensured not to contact with the blank after the die is pressed; the hydraulic forming device comprises a servo press, a press machine control system, a male die, a liquid pool and female die, a blank holder and a stamping die with a piston, wherein the liquid pool and female die and a hydraulic cylinder with the piston which are hydraulically formed are communicated through a pipeline, and liquid for quenching is arranged in the liquid pool and female die.

(3) And (3) rapidly closing the die, starting a hydraulic machine connected with the liquid pool, moving the piston downwards to enable the liquid in the liquid pool to contact the blank, rapidly filling the liquid pool with the liquid in the liquid pool to form a certain pressure, and quenching and shaping the blank.

(4) After maintaining the pressure for a period of time, the piston moves upwards, and the mold is opened to obtain the final formed piece.

Preferably, the heat preservation temperature in the step (1) is 850-980 ℃, and the heat preservation time is 3-7 min; more preferably, the holding temperature is 950 ℃. The heat preservation time is 3-7 min, and more preferably, the heat preservation time is 5 min.

Preferably, the time for rapidly moving the blank to the die of the hydraulic forming device in the step (2) is 3-8s, and more preferably, the transfer time of the blank is 5 s.

Preferably, in the step (4), the blank is cooled to room temperature of 20-25 ℃ during pressure maintaining.

And the temperature of the blank is measured by adopting an infrared temperature measuring instrument.

The method is based on a hydraulic forming device, realizes the quenching of a high-temperature formed part in a die, effectively solves the problem of uneven strength of a high-strength steel hot-stamped part, and improves the quality of the hot-stamped part.

Description of the drawings:

FIG. 1 is a schematic view of a hydroforming apparatus in the process of the present invention;

FIG. 2 is a schematic flow diagram of the process of the present invention;

wherein: FIG. 2(a) is a schematic view of a blank moving onto a die; FIG. 2(b) is a schematic view after the mold is closed; fig. 2(c) is a schematic view of quenching and shaping the billet.

In the figure: 1: a male die; 2: a blank holder; 3: a blank; 4: the liquid pool is also used as a concave die; 5: a piston; 6: and a hydraulic cylinder.

The specific implementation mode is as follows:

(1) and (3) placing the blank in a heating furnace, and austenitizing the blank at the heat preservation temperature of 950 ℃ for 5 min.

(2) Rapidly moving the blank obtained in the step (1) to a die of a hydraulic forming device within 5s, wherein the liquid amount in a liquid pool of the die is ensured not to contact with the blank after the die is pressed; and the temperature of the blank is measured by adopting an infrared temperature measuring instrument.

(3) The die is quickly closed, meanwhile, a hydraulic machine connected with the liquid pool is started, the piston moves downwards to enable liquid in the liquid pool to contact the blank, the liquid in the liquid pool fills the liquid pool and forms a certain pressure, and the blank is quenched and shaped; the temperature of the blank is measured by an infrared temperature measuring instrument.

(4) And cooling the blank to the room temperature of 20-25 ℃ in the pressure maintaining process, moving the piston upwards, and opening the die to obtain a final formed piece.

Claims

1. A hot stamping and quenching integrated processing method based on a hydraulic forming device is characterized by comprising the following specific steps:

(1) placing the blank in a heating furnace, and austenitizing the blank at a certain heat preservation temperature for a certain heat preservation time;

(2) rapidly moving the blank obtained in the step (1) to a liquid pool and female die of a hydraulic forming device, wherein the liquid amount in the liquid pool and female die is ensured not to contact the blank after a male die is pressed; the hydraulic forming device comprises a servo press, a press machine control system, a male die, a liquid pool and female die, a blank holder and a hydraulic cylinder with a piston, wherein the liquid pool and female die and the hydraulic cylinder with the piston which are formed by hydraulic forming are communicated through a pipeline, and liquid for quenching is arranged in the liquid pool and female die;

(3) the male die and the liquid pool and female die are quickly closed, meanwhile, a hydraulic cylinder connected with the liquid pool and female die is started, a piston moves downwards, so that liquid in the liquid pool and female die contacts a high-temperature piece to be formed, the liquid in the liquid pool and female die is quickly filled in the liquid pool and female die to form a certain pressure, and the blank is quenched;

(4) and keeping the pressure for a period of time, moving the piston upwards, and opening the die to obtain a final formed piece.

2. The integrated hot stamping and quenching treatment method based on the hydroforming device according to claim 1, characterized in that the heat preservation temperature in step (1) is 850-980 ℃, and the heat preservation time is 3-7 min.

3. The integrated hot stamping and quenching treatment method based on the hydroforming device according to claim 1, wherein the time for rapidly moving the blank to the die of the hydroforming device in the step (2) is 3-8 s.

4. The integrated processing method for hot stamping and quenching based on the hydroforming device according to claim 1, wherein in the step (4), the blank is cooled to 20-25 ℃ simultaneously during the pressure maintaining process.