阅读说明：本技术 一种中频感应焊接接头热处理方法 (Heat treatment method for medium-frequency induction welded joint ) 是由 王岳军 于 2020-11-18 设计创作，主要内容包括：本发明属于热处理技术领域,具体为一种中频感应焊接接头热处理方法,其步骤为根据带处理管件的规格选取合适的中频电源功率和加热宽度对其采取感应加热方式进行焊接后热处理,其有益效果在于,中频感应加热方式通过绕制感应线圈在待测管件上工作,其方法安装简易且对位置的要求性不高,适用于施工环境复杂的现场施工焊接接头的热处理,且其加热方式升温速度快,局部加热热效率高,管件内外温差小。(The invention belongs to the technical field of heat treatment, and particularly relates to a heat treatment method for a medium-frequency induction welding joint.)

1. A heat treatment method for a medium-frequency induction welded joint is characterized by comprising the following specific steps:

step 1: measuring the specification of the pipe fitting to be treated, wherein the specification comprises an outer diameter and a wall thickness;

step 2: calculating a theoretical power value and a theoretical heating width value according to the measured outer diameter and wall thickness;

and step 3: selecting proper intermediate frequency power supply power and heating width according to the field condition;

and 4, step 4: polishing a welding line, fixing the hot end of the thermocouple on a welding joint of a pipe fitting to be treated, wrapping a layer of heat-insulating cotton on the thermocouple, wrapping a layer of asbestos cloth on the thermocouple, and binding and fixing the thermocouple; the heat insulation cotton is wrapped around the welding line by taking the welding line as a center; the cold end of the thermocouple is arranged on the outer side of the heat insulation cotton;

and 5: winding the electromagnetic induction coils on the welding seam, wrapping the electromagnetic induction coils on two sides of the welding seam by taking the welding seam as a center, wherein the winding length is the selected heating width, and the coils are spaced by 1.5 cm;

step 6: carrying out heat treatment on the butt joint, wherein the constant temperature of the heat treatment is 750-770 ℃, and the constant temperature time is 2-3 h;

and 7: and naturally cooling, and carrying out nondestructive inspection and hardness detection on the pipe fitting, wherein the result is qualified.

2. The heat treatment method of claim 1, wherein the theoretical power value is calculated as (outer diameter ÷ wall thickness)^1/2X outer diameter x thickness ÷ 17.

3. The method of claim 2, wherein the power of the medium frequency power source is selected such that the power must be greater than a theoretical power value calculated from the outside diameter and the wall thickness.

4. The heat treatment method for medium frequency induction welded joint as claimed in claim 1, wherein said theoretical calculation formula of heating width is (outer diameter ÷ wall thickness)^1/2X 4.5+ wall thickness x 5.3.

5. The heat treatment method for the medium-frequency induction welded joint as claimed in claim 4, wherein the heating width is in a range of 0.7 to 1.4 times of a theoretical heating width.

6. The method of claim 1, wherein the thermocouple is a ceramic-insulated K-index thermocouple.

7. The heat treatment method for the medium frequency induction welded joint as recited in claim 1, wherein the thermocouple is fixed by spot welding.

8. The heat treatment method for the medium frequency induction welded joint as claimed in claim 1, wherein the electromagnetic induction coil is wound in parallel without twinning.

9. The method of claim 1, wherein the banding fixture material is fiberglass tape.

Technical Field

The invention belongs to the technical field of heat treatment, and particularly relates to a heat treatment method for a medium-frequency induction welded joint.

Background

The welding residual stress is caused by uneven temperature distribution of a weldment caused by welding, expansion and contraction of weld metal, and the like, and all the welding construction is accompanied by the residual stress. The post-weld heat treatment is a heat treatment performed to remove residual stress of the welded joint and improve the structure and properties of the welded joint. The most common method for eliminating residual stress is high-temperature tempering, namely, a weldment is heated to a certain temperature and is kept for a certain time, plastic flow is generated at a place with high internal stress by utilizing the reduction of the yield limit of a material at a high temperature, the elastic deformation is gradually reduced, and the plastic deformation is gradually increased to reduce the stress, and the general process flow is as follows: installing a thermocouple → arranging a heating device → setting heat treatment parameters → wrapping heat preservation cotton → carrying out heat treatment.

The existing method for post-welding heat treatment of welded joints adopts far infrared ceramic electric heating, but the far infrared ceramic electric heating has low heat transfer efficiency, can cause the phenomenon of overlarge temperature difference of the local inner wall and the local outer wall of a pipe fitting, is complex to install and is not suitable for application in a construction site, and adopts an induction heating process to improve the heat treatment quality of the post-welding joints, ensure that the post-welding joints reach higher hardness indexes and prolong the service life of welded junctions, so that the method is a novel process method which has the advantages of simple installation, high heating efficiency and uniform heating effect.

Disclosure of Invention

The invention aims to improve and innovate the defects and problems of the prior art in the background art, provides a heat treatment method for a medium-frequency induction welding joint, and solves the problems of low electric heating efficiency and large temperature difference of far infrared ceramics.

In order to achieve the purpose, the invention provides the following technical scheme:

a heat treatment method for a medium-frequency induction welding joint comprises the following specific steps:

step 1: measuring the specification of the pipe fitting to be treated, wherein the specification comprises an outer diameter and a wall thickness;

step 2: calculating a theoretical power value and a theoretical heating width value according to the measured outer diameter and wall thickness;

and step 3: selecting proper intermediate frequency power supply power and heating width according to the field condition;

and 4, step 4: polishing a welding line, fixing the hot end of the thermocouple on a welding joint of a pipe fitting to be treated, wrapping a layer of heat-insulating cotton on the thermocouple, wrapping a layer of asbestos cloth on the thermocouple, and binding and fixing the thermocouple; the heat insulation cotton is wrapped around the welding line by taking the welding line as a center; the cold end of the thermocouple is arranged on the outer side of the heat insulation cotton;

and 5: winding the electromagnetic induction coils on the welding seam, wrapping the electromagnetic induction coils on two sides of the welding seam by taking the welding seam as a center, wherein the winding length is the selected heating width, and the coils are spaced by 1.5 cm;

step 6: carrying out heat treatment on the butt joint, wherein the constant temperature of the heat treatment is 750-770 ℃, and the constant temperature time is 2-3 h;

and 7: and naturally cooling, and carrying out nondestructive inspection and hardness detection on the pipe fitting, wherein the result is qualified.

Further, the theoretical value of power is calculated by the formula (outer diameter ÷ wall thickness)^1/2X outer diameter x thickness ÷ 17.

Further, the method for selecting the power of the intermediate frequency power supply is that the power of the intermediate frequency power supply is larger than a theoretical power value calculated according to the outer diameter and the wall thickness.

Further, the theoretical calculation formula of the heating width is (outer diameter ÷ wall thickness)^1/2X 4.5+ wall thickness x 5.3.

Further, the heating width range is 0.7-1.4 times of the theoretical value of the heating width.

Further, the thermocouple is a ceramic insulation K-index thermocouple.

Further, the thermocouple is fixed in a spot welding mode.

Further, the electromagnetic induction coil should be wound in parallel and should not be twisted.

Further, the banding fixing material is a glass fiber band.

Compared with the prior art, the invention has the beneficial effects that: the medium-frequency induction heating mode works on the pipe fitting to be measured by winding the induction coil, the method is simple and easy to install, the requirement on the position is low, the method is suitable for heat treatment of the field construction welding joint with a complex construction environment, the heating mode is high in temperature rising speed, the local heating heat efficiency is high, and the temperature difference between the inside and the outside of the pipe fitting is small.

Drawings

FIG. 1 is a schematic view of a heating arrangement of the present invention.

FIG. 2 is a schematic view of the structure of the insulating layer of the present invention.

The names of the parts corresponding to the respective reference numerals are: 1-a pipe fitting to be treated, 2-a welding line, 3-a heat insulation layer, 31-heat insulation cotton, 32-asbestos cloth, 4-an electromagnetic induction coil, 51-a thermocouple hot end and 52-a thermocouple cold end.

Detailed Description

In order to make the technical means, innovative features, objectives and effects of the present invention apparent, the technical solutions of the present invention will be further described in detail with reference to the detailed description.

Example 1

As shown in fig. 1 and 2, the heat treatment method for the medium-frequency induction welded joint is used for treating a pipe fitting with the specification of phi 795mm multiplied by 29mm, and the material is SA335-P91 steel:

step 1: measuring the specification of the pipe fitting to be treated, wherein the specification comprises an outer diameter and a wall thickness;

step 2: calculating a theoretical power value and a theoretical heating width value according to the measured outer diameter and wall thickness; the theoretical value of power is calculated by the formula (outer diameter ÷ wall thickness)^1/2X outer diameter x thickness ÷ 17, the method of choosing the power of the medium frequency power supply is that its power must be greater than the theoretical value of power calculated according to outer diameter and wall thickness; the calculated power is 71kW, so the power of the selected power supply is 80 kW. The theoretical value calculation formula of the heating width is (outer diameter ÷ wall thickness)^1/2The heating width is 0.7-1.4 times of the theoretical value of the heating width, the theoretical value of the heating width is 45.07cm through calculation, and the theoretical value of the heating width is 0.78 times of the theoretical value, namely 35cm through on-site inspection.

And step 3: selecting proper intermediate frequency power supply power and heating width according to the field condition;

and 4, step 4: firstly, polishing a welding seam, fixing the hot end of a ceramic insulation K-index thermocouple on a welding joint of a pipe fitting to be treated through spot welding, wrapping a layer of heat insulation cotton on the hot end, wrapping a layer of asbestos cloth on the hot end, and binding and fixing the asbestos cloth by using a glass fiber tape; the heat insulation cotton is wrapped around the welding line by taking the welding line as a center; the cold end of the thermocouple is arranged on the outer side of the heat insulation cotton;

and 5: winding the electromagnetic induction coils on the welding seam, wrapping the electromagnetic induction coils on two sides of the welding seam by taking the welding seam as a center, wherein the winding length is the selected heating width, and the coils are spaced by 1.5 cm; the electromagnetic induction coil should be wound in parallel and not twisted.

Step 6: carrying out heat treatment on the butt joint, wherein the constant temperature of the heat treatment is 760 ℃, and the constant temperature time is 2 h;

and 7: and naturally cooling, and carrying out nondestructive inspection and hardness detection on the pipe fitting, wherein the result is qualified.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.