Deep hole welding method for heat exchange tube and tube plate in waste heat boiler

Abstract

The invention relates to a deep hole welding method for a heat exchange tube and a tube plate in a waste heat boiler. The method comprises the following steps that (1) the joint of the heat exchange tube and the tube plate is preprocessed; (2) carrying out base metal fusion welding on the pre-processed heat exchange tube and the tube plate; (3) performing manual argon arc welding TIG on the melted and welded part of the base metal in the step (2) to form a fillet weld in the hole; and (4) after welding is completed, whether welding is sealed completely or not is checked through an airflow or water inlet test. According to the deep hole welding method, the heat exchange tube and the tube plate are welded, the welding quality of the heat exchange tube and the tube plate is improved, the thermal stress resistance strength of a weld joint is greatly improved, the technological operation is simple, the welding performance is excellent, the product quality is greatly improved, and the service life of the product is greatly prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of heat exchange tube and tube sheet welding technology, and relates to a deep hole welding method for heat exchange tube and tube sheet in a waste heat boiler. Background Art

[0002] Waste heat boiler refers to a boiler that uses waste heat from industrial production to produce steam. It is a high-temperature, high-pressure heat exchanger. The welding of heat exchange tubes and tube sheets is an important process in the manufacture of waste heat boilers, so the welding quality of heat exchange tubes and tube sheets directly determines the quality and service life of waste heat boilers.

[0003] The welding of heat exchange tubes and tube sheets in traditional waste heat boilers is as follows: Figure 1 As shown in the figure, the fillet weld structure is mainly used, that is, the heat exchange tube is inserted into the front end of the tube sheet and welded to form a fillet weld, including three types of joints: flat fillet weld, extended fillet weld and internal fillet weld, and generally an expansion type is added. This welding method may cause the weld to crack easily due to the gap between the heat exchange tube and the tube sheet, and the degree of fusion between the weld and the parent material is not enough, which will affect the service life of the equipment.

[0004] Therefore, a deep hole welding method for heat exchange tubes and tube sheets in a waste heat boiler is designed to overcome the above problems. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a deep hole welding method for heat exchange tubes and tube sheets in waste heat boilers. The method designed by the present invention welds heat exchange tubes and tube sheets, improves the welding quality, greatly improves the strength of the weld seam against thermal stress, and with the deep hole welding method, the process operation is simple, the welding performance is excellent, and the product quality and service life are greatly improved.

[0006] The present invention is implemented by the following technical solution: a deep hole welding method for heat exchange tubes and tube sheets in a waste heat boiler, the method comprising the following steps: 1) Pre-process the connection between the heat exchange tube and the tube sheet; 2) Perform base material melting welding on the pre-processed heat exchange tubes and tube sheets; 3) The place where the base material is melted and welded in step 2) is welded by manual argon arc welding (TIG), that is, a fillet weld in the hole is formed; 4) After welding is completed, perform airflow or water inlet test to check whether the welding is sealed completely.

[0007] As a preference: the specific method of pre-processing in step 1) is: First, a circular hole and a first positioning step are machined on the tube sheet, and then a second positioning step matching the first positioning step is machined on the heat exchange tube, so that the first positioning step and the second positioning step on the tube sheet and the heat exchange tube correspond to each other and are accurately positioned.

[0008] As a preferred method: the method of melting welding of the base material in step 2) is: During the entire process of base metal melting welding, it is necessary to ensure that the tungsten needle of the welding gun is accurately positioned and that the tungsten needle of the welding gun always maintains a consistent distance from the circumference of the positioning joint. Otherwise, the weld on the side where the tungsten needle is close to the weld may be too thick, and the weld on the side far from the weld may not be fused.

[0009] Preferably, the welding gun and the tungsten needle are in a vertical 90-degree structure, which facilitates accurate positioning of welding.

[0010] The beneficial effects of the present invention are as follows: The deep hole welding method for heat exchange tubes and tube sheets in a waste heat boiler designed by the present invention is used to weld the heat exchange tubes and tube sheets, thereby improving the welding quality and greatly improving the strength of the welds against thermal stress. In addition, the deep hole welding method has simple process operation and excellent welding performance, thereby greatly improving product quality and service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a conventional fillet weld type 1 between a tube sheet and a heat exchange tube in the prior art.

[0012] Figure 2 This is the conventional fillet weld type 2 between the tube sheet and the heat exchange tube in the prior art.

[0013] Figure 3 It is a schematic diagram of the deep hole welding method of the present invention.

[0014] Figure 4 It is a schematic diagram of fusion welding in the present invention.

[0015] Figure 5 It is a schematic diagram of cover welding in the present invention. DETAILED DESCRIPTION

[0016] In order to enable those skilled in the art to more clearly understand the objectives, technical solutions and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0017] In the description of the present invention, it is necessary to understand that the orientation or position relationship indicated by the terms such as "up", "down", "left", "right", "inside", "outside", "horizontal" and "vertical" is based on the orientation or position relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or original referred to must have a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0018] The present invention will be described in detail below with reference to the accompanying drawings: Figure 3 As shown, a deep hole welding method for heat exchange tubes and tube sheets in a waste heat boiler is characterized in that the method comprises the following steps: 1) Pre-process the connection between the heat exchange tube and the tube sheet; 2) Perform base material melting welding on the pre-processed heat exchange tubes and tube sheets; 3) The place where the base material is melted and welded in step 2) is welded by manual argon arc welding (TIG), that is, a fillet weld in the hole is formed; 4) After welding is completed, perform airflow or water inlet test to check whether the welding is sealed completely.

[0019] like Figure 4 As shown, the specific method of pre-processing in step 1) is: First, a circular hole 2 and a first positioning step 3 are processed on the tube sheet 1, and then a second positioning step 4 matching the first positioning step 3 is processed on the heat exchange tube 5, so that the first positioning step 3 and the second positioning step 4 on the tube sheet 1 and the heat exchange tube 5 correspond to each other and are accurately positioned.

[0020] In the present invention, the heat exchange tube and the inner hole of the tube sheet can be positioned relatively accurately through the first positioning step 3 and the second positioning step, thereby ensuring the subsequent welding effect.

[0021] like Figure 5 As shown, the method of melting welding of the base material in step 2) is: During the whole process of the base metal melting welding, the tungsten needle of the welding gun must be accurately positioned, and the tungsten needle of the welding gun must always maintain a consistent distance from the circumference of the positioning joint. Otherwise, the weld on the side where the tungsten needle is close to the weld may be too thick, and the weld on the side far from the weld may not be fused. The welding gun and the tungsten needle are vertically 90 degrees, which is convenient for accurate positioning welding.

[0022] It is worth noting that in step 1), the welding is base metal melting welding, and no welding material needs to be added. The tungsten needle must be positioned accurately and its length must be adjusted appropriately. It is imperative that the tungsten needle head and the circumference of the positioning joint always maintain a consistent distance.

[0023] The high-sealing precooler evaporator designed by the present invention is mainly a further improvement on the original evaporator, which improves the heat exchange efficiency, reduces the welding amount, and improves the safety of maintenance. It can achieve the purpose of energy saving and efficiency improvement while reducing the volume and weight of the evaporator, and the welding part has extremely strong tensile and compressive strength. The present invention is mainly to improve the mechanical properties of the welding part, so a new welding method is designed.

[0024] The present invention determines parameters such as welding voltage, current, welding speed, etc. on the basis of trial welding, and conducts mechanical property test, metallographic test, etc. on the welding sample, and forms welding process evaluation on this basis, and then forms a formal welding process card.

[0025] The specific embodiments described herein are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A deep hole welding method for heat exchange tubes and tube sheets in a waste heat boiler, characterized in that: The method comprises the following steps: 1) Pre-process the connection between the heat exchange tube and the tube sheet; 2) Perform base material melting welding on the pre-processed heat exchange tubes and tube sheets; 3) The place where the base material is melted and welded in step 2) is welded by manual argon arc welding (TIG), that is, a fillet weld in the hole is formed; 4) After welding is completed, perform airflow or water inlet test to check whether the welding is sealed completely.

2. The deep hole welding method for heat exchange tubes and tube sheets in a waste heat boiler according to claim 1, characterized in that: The specific method of pre-processing in step 1) is: First, a circular hole (2) and a first positioning step (3) are machined on the tube sheet (1), and then a second positioning step (4) that matches the first positioning step (3) is machined on the heat exchange tube (5), so that the first positioning step (3) and the second positioning step (4) on the tube sheet (1) and the heat exchange tube (5) correspond to each other and are accurately positioned.

3. The deep hole welding method for heat exchange tubes and tube sheets in a waste heat boiler according to claim 1, characterized in that: The method of melting welding of the base material in step 2) is: During the entire process of base metal melting welding, it is necessary to ensure that the tungsten needle of the welding gun is accurately positioned and that the tungsten needle of the welding gun always maintains a consistent distance from the circumference of the positioning joint. Otherwise, the weld on the side where the tungsten needle is close to the weld may be too thick, and the weld on the side far from the weld may not be fused.

4. The deep hole welding method for heat exchange tubes and tube sheets in a waste heat boiler according to claim 3 is characterized in that: The welding gun and the tungsten needle are in a vertical 90-degree structure, which is convenient for accurate positioning of welding.

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