阅读说明：本技术 局部温差调控残余应力热处理方法 (Heat treatment method for regulating residual stress by local temperature difference ) 是由 蒋文春 谷文斌 金强 罗云 王金光 涂善东 于 2020-07-29 设计创作，主要内容包括：本发明公开了一种局部温差调控残余应力热处理方法,具体涉及热处理调控残余应力领域。本发明基于常规加热方法对设备进行热处理升温保温操作,热处理保温操作后,针对设备外壁保留覆盖于其上的保温棉,使其缓慢降温,同时对设备内壁进行水冷处理,根据设备类型设置喷洒体积范围,利用喷淋装置喷洒设备内壁或焊缝进行降温,直至设备冷却至室温,基于设备内外壁间存在的巨大温差形成畸变温度场调控残余应力,控制设备变形情况。本发明降低了设备的残余应力,实现了热处理后设备应力的均匀分布,将设备表面产生的拉应力转变为压应力,提高了设备的耐应力腐蚀开裂性能和疲劳性能,延长了设备的使用寿命,操作方便、经济高效,具有重要的工程应用价值。(The invention discloses a heat treatment method for regulating and controlling residual stress by local temperature difference, and particularly relates to the field of regulating and controlling residual stress by heat treatment. The equipment is subjected to heat treatment temperature rise and heat preservation operation based on a conventional heating method, after the heat treatment and heat preservation operation, heat preservation cotton covered on the equipment is reserved aiming at the outer wall of the equipment, the equipment is slowly cooled, meanwhile, the inner wall of the equipment is subjected to water cooling treatment, a spraying volume range is set according to the type of the equipment, the inner wall of the equipment or a welding line is sprayed by a spraying device for cooling until the equipment is cooled to room temperature, a distortion temperature field is formed based on the huge temperature difference between the inner wall and the outer wall of the equipment to regulate and control the residual stress. The invention reduces the residual stress of the equipment, realizes the uniform distribution of the equipment stress after heat treatment, converts the tensile stress generated on the surface of the equipment into the compressive stress, improves the stress corrosion cracking resistance and the fatigue resistance of the equipment, prolongs the service life of the equipment, is convenient to operate, is economic and efficient, and has important engineering application value.)

1. A thermal treatment method for regulating and controlling residual stress by local temperature difference is characterized in that thermal treatment heating and heat preservation operation is carried out on equipment based on a conventional heating method, after the thermal treatment heat preservation operation of the equipment is finished, heat preservation cotton covered on the equipment is reserved for the outer wall of the equipment, the outer wall of the equipment is slowly cooled, meanwhile, water cooling treatment is carried out on the inner wall of the equipment, and a spraying device is adopted to spray the inner wall or a welding line of the equipment for cooling until the equipment is completely cooled to room temperature.

2. The thermal treatment method for regulating residual stress by local temperature difference as claimed in claim 1, wherein the thermal treatment heating and maintaining operation is performed according to the heat treatment standard specified by the country.

3. The thermal treatment method for regulating residual stress by local temperature difference as claimed in claim 1, wherein in the water cooling treatment process, if the equipment is rotary equipment, the spraying volume range of the spraying device is not less than

4. The thermal treatment method for regulating residual stress according to claim 1, wherein the spraying time in the water cooling treatment process is the time from the beginning of the water cooling treatment of the equipment to the cooling of the equipment to room temperature.

5. The thermal treatment method for local temperature difference regulation and control of residual stress as claimed in claim 1, wherein the water cooling treatment causes a higher temperature difference between the inner wall and the outer wall of the equipment, and the pre-shrinking resistance generated by the inner wall of the equipment is greater than the force generated by the shrinkage of the outer wall of the equipment during the cooling of the equipment to room temperature, thereby controlling the deformation of the equipment.

Technical Field

The invention relates to the field of residual stress regulation and control by heat treatment, in particular to a residual stress regulation and control heat treatment method by local temperature difference.

Background

Since the 21 st century, with the gradual advance of large-scale, high-yield and large-scale increase of industrial product demand in the fields of petrochemical industry and the like, more and more pipelines and pressure vessels are used in high-temperature and high-pressure environments, and the medium is rich in corrosive elements such as sulfur, hydrogen and the like, so that the inner walls of the pipelines and the pressure vessels are corroded, particularly nearby welding seams. The inner wall of the welding seam has larger tensile stress due to the failure of effectively reducing the welding residual stress, and the problem of more severe stress corrosion is caused after the welding seam is in the severe environment for a long time, so that the service life of equipment is shortened, and major accidents and economic losses are caused.

How to reduce the residual stress of the equipment and reduce the probability of stress corrosion cracking is always a problem of great concern in the engineering field, which is directly related to the structural integrity of the equipment. The current method for preventing stress corrosion mainly comprises the following steps: avoiding using materials sensitive to stress corrosion, improving corrosion environment, adding corrosion inhibitor into medium, adopting metal or non-metal protective layer in equipment and heat treatment method to reduce tensile stress. The construction cost brought by the method is higher, but the stress reduction of the inner wall of the equipment is smaller after the heat treatment by the conventional integral or local heat treatment method at present, larger tensile stress still exists after the heat treatment, and the equipment is still easy to generate stress corrosion cracking under the action of corrosive media. Therefore, it is necessary to provide a new heat treatment process, so that the tensile stress of the inner wall of the treated equipment is significantly reduced, even in a compressive stress state, thereby improving the stress corrosion resistance of the equipment and prolonging the service life.

Disclosure of Invention

In order to solve the problems and improve the stress corrosion resistance of equipment, the invention provides a heat treatment method for regulating and controlling residual stress by local temperature difference.

The invention specifically adopts the following technical scheme:

a heat treatment method for regulating and controlling residual stress by local temperature difference is characterized in that heat treatment heating and heat preservation operation is carried out on equipment based on a conventional heating method, after the heat treatment and heat preservation operation of the equipment is finished, heat preservation cotton covered on the equipment is reserved for the outer wall of the equipment, the outer wall of the equipment is slowly cooled, meanwhile, water cooling treatment is carried out on the inner wall of the equipment, and a spraying device is adopted to spray the inner wall or a welding line of the equipment for cooling until the equipment is completely cooled to room temperature.

Preferably, the operation of heating and holding the temperature by heat treatment is performed according to the heat treatment standard specified by the state.

Preferably, in the water cooling treatment process, if the equipment is rotary equipment, the spraying volume range of the spraying device is not less than

Wherein R is the radius of the shell of the rotary equipment, and T is the thickness of the shell of the rotary equipment; if the equipment is flat plate equipment, the spraying volume range of the spraying device is not less than 4KH, wherein K is the width of a welding line of the equipment, and H is the thickness of a plate of the equipment.

Preferably, the spraying time in the water cooling treatment process is the time taken for the equipment to start the water cooling treatment until the equipment is cooled to room temperature.

Preferably, the water cooling treatment causes a higher temperature difference between the inner wall and the outer wall of the equipment, and the pre-shrinkage resistance generated by the inner wall of the equipment is greater than the force generated by the shrinkage of the outer wall of the equipment during the cooling of the equipment to the room temperature, so that the deformation condition of the equipment is controlled.

The invention has the following beneficial effects:

the invention provides a heat treatment method for regulating residual stress by local temperature difference, which utilizes an external cooling source to cool equipment to generate a distortion temperature field, regulates residual stress based on the temperature difference of the distortion temperature field and controls the deformation condition of the equipment;

the method reduces the residual stress of the equipment, realizes the uniform distribution of the stress of the equipment after heat treatment, converts the tensile stress generated on the surface of the equipment into the compressive stress, improves the stress corrosion cracking resistance and the fatigue resistance of the equipment, and prolongs the service life of the equipment;

the method is convenient to operate, economical and efficient, and has important engineering application value.

Drawings

FIG. 1 is a schematic diagram of a thermal treatment method for regulating residual stress by local temperature difference.

FIG. 2 is a graph showing the stress distribution in the vicinity of the weld of the inner wall of the high-pressure storage tank in example 1; fig. 2(a) is an axial stress distribution diagram near a weld of the inner wall of the high-pressure tank, and fig. 2(b) is a hoop stress distribution diagram near the weld of the inner wall of the high-pressure tank.

Fig. 3 is a schematic view of the spraying device and the spraying range in embodiment 2.

FIG. 4 is a graph showing stress distribution before and after heat treatment in example 2; fig. 4(a) is a transverse residual stress distribution diagram near the weld of the test piece, and fig. 4(b) is a longitudinal residual stress distribution diagram near the weld of the test piece.

Detailed Description

The following description of the embodiments of the present invention will be made with reference to the accompanying drawings:

as shown in fig. 1, a local temperature difference regulation residual stress heat treatment method specifically includes the following steps:

firstly, the equipment is subjected to heat treatment temperature rise and preservation operation based on a conventional heating method, and the heat treatment temperature rise and preservation operation is performed according to the heat treatment standard specified by the state.

Then, after the heat treatment and heat preservation operation of the equipment is finished, preserving the heat preservation cotton covered on the outer wall of the equipment aiming at the outer wall of the equipment, slowly cooling the outer wall of the equipment, simultaneously carrying out water cooling treatment on the inner wall of the equipment, and carrying out spraying cooling on the inner wall of the equipment or a welding line by adopting a spraying device until the equipment is completely cooled to the room temperature; wherein, the spraying volume range of the spraying device is set according to the type of the equipment, ifThe equipment is rotary equipment, such as pipelines, containers, etc., and the spraying volume range of the spraying device is not less thanR is the radius of the shell of the rotary equipment, T is the thickness of the shell of the rotary equipment, if the equipment is flat equipment, the spraying volume range of the spraying device is not less than 4KH, K is the width of a welding seam of the equipment, and H is the thickness of a plate of the equipment.

Because the water cooling treatment causes a higher temperature difference between the inner wall and the outer wall of the equipment, and the outer wall of the equipment is slowly cooled in the process of cooling the equipment to room temperature, the inner wall of the equipment shrinks after the water cooling treatment to generate pre-shrinking resistance, the pre-shrinking force generated by the inner wall of the equipment is greater than the acting force generated by the shrinkage of the outer wall on the inner wall of the equipment, and the pre-shrinking resistance and the acting force are mutually offset, so that the residual stress is regulated and controlled by utilizing the temperature difference between the inner wall; meanwhile, after the whole equipment is cooled to the room temperature state, the stress acting on the inner wall of the equipment is remarkably reduced, and when the temperature difference between the inner wall and the outer wall of the equipment is large enough (the temperature difference is 300-400 ℃), the equipment is in a compressive stress state, so that the residual stress acting on the outer wall of the equipment can be reduced even if the equipment only depends on the conventional cooling shrinkage of the outer wall.