WO2019019100A1

WO2019019100A1 - Welding method for large cylinder segment

Info

Publication number: WO2019019100A1
Application number: PCT/CN2017/094691
Authority: WO
Inventors: 张东辉; 吕军; 谢桂芝
Original assignee: 乔治洛德方法研究和开发液化空气有限公司; 张东辉; 吕军; 谢桂芝
Priority date: 2017-07-27
Filing date: 2017-07-27
Publication date: 2019-01-31

Abstract

A easy-to-operate welding method for a large cylinder segment, the method comprising: performing, according to a predetermined inner diameter of a large cylinder, a cutting operation; machining by means of a beveling machine, welding along a longitudinal seam, performing pre-bending and rolling to obtain a cylinder section, and optionally combining at least two cylinder sections into a cylinder segment and performing circumferential welding along a circumferential seam. A contraction compensation length for the longitudinal seam welding is calculated and reserved by means of an empirical formula, and a welding order for the circumferential seam welding is adjusted to control welding contraction and deformation. For different web thicknesses, customized welding orders are adopted to perform welding at a circumferential seam, thus effectively reducing contraction of the inner diameter of a cylinder segment caused by circumferential welding while ensuring welding quality, guaranteeing that the inner diameter of a large cylinder segment meets a specified size requirement after welding, and effectively controlling the size error of the inner diameter of the cylinder segment.

Description

Welding method of large cylinder segment

Technical field

The invention relates to a welding method for a large cylinder segment, in particular to a welding method capable of regulating welding shrinkage deformation. It is suitable for the preparation process with high requirements on the uniformity of the inner diameter of the cylinder segment.

Background technique

Modern welding structures are developing in the direction of large-scale and complicated, and the specifications required for various types of components are becoming larger and larger, and the requirements for welding are becoming more and more strict. During the welding process, the process of preheating, welding, etc. will cause deformation of various parts of the large component, causing changes in the relative position and shape relationship between the components. In order to ensure the design requirements of the product, it must be tested and regulated during the welding manufacturing process. It is more and more difficult to monitor and correct the welding deformation of large thick-walled pipes, which has become the main reason that affects the stability of welded components, reduces the service life of weldments, and causes damage to welded structures. Conventional welding deformation monitoring methods generally use equipment such as dial gauges and reference comparison or displacement sensors. There are many deficiencies in actual measurement, especially when detecting large parts. In the assembly process with high precision, large components generally adopt optical alignment methods to meet the installation accuracy requirements. Optical centering requires the production of center tooling, which is installed in a central axis to meet the accuracy requirements, while the production and installation of center tooling is bound to increase costs.

The welding process is actually a thermal process of cooling and solidifying after heating in a local area of the weldment, but due to the uneven temperature field, the weldment is unevenly expanded and contracted, thereby causing welding stress inside the weldment to cause welding deformation. The main factors controlling the degree of shrinkage and deformation are: 1 the restraining effect of the external fixture; 2 the internal restraint of the large weldment; 3 the rigidity of the weldment itself; 4 the welding heat input and the welding speed; 5 the cooling speed. The interaction of these factors is very complicated, and it is difficult to calculate and predict the shrinkage and deformation of the simplest welds, but some measures and process steps can be taken to control the shrinkage and deformation. Common welding deformations are: (1) longitudinal shrinkage deformation; (2) transverse shrinkage deformation; (3) angular deformation; (4) bending deformation; (5) distortion; (6) wave deformation.

At present, the manufacturing process of large cylinder segments is usually: steel plate marking, cutting processing, bevel machining, Pre-bending, curved steel plate rolling, tile correction, tile platform group circle, longitudinal seam welding, deformation correction, stiffening ring installation, welding, cylinder section pairing into cylinder section, ring seam welding, inspection, anti-corrosion, etc. . Due to the limitation of steel plate size and transportation conditions, large cylinders often need to be welded multiple times during the manufacturing process. When the diameter of the cylinder section is large, there may be more than one longitudinal weld; when the length of the cylinder section is large, It is necessary to calibrate the longitudinally welded barrel sections, and then assemble the two or more barrel sections on the roller frame to weld the barrel wall joints into a cylinder section. In the welded joint of thick steel plates, the weld requires multiple layers of welding. Therefore, in addition to the longitudinal and transverse weld stresses, there are weld stresses along the thickness of the steel sheet, which will greatly reduce the plasticity of the joint. During the welding process, uneven heating and cooling, the weld zone shrinks in the longitudinal and transverse directions, causing localized bending, bending, distortion and torsion of the component. Welding deformation includes longitudinal and transverse contraction, bending deformation, angular deformation and distortion, and is usually a combination of several deformations. Especially for thick steel plates, the weld depth is very deep, and the welding adopts the multi-pass welding method. During the welding process, each welding will produce a certain angular deformation. After multiple welding, the transverse shrinkage deformation will accumulate, resulting in welding. Large angle deformation of the rear steel plate. In order to reduce the shrinkage deformation of the tank wall during the welding process, certain technological measures should be taken to reduce the weld shrinkage. Under the existing conditions, the most effective process measure is the rigid fixing method, which increases the local rigidity of the structure to limit the shrinkage of the weld wall of the tank wall and the heat affected zone.

In order to reduce the welding stress and welding deformation, a reasonable welding sequence is adopted, and the thick welding seam is layered in the thickness direction. When welding, you should select the welding sequence that will make each weld seam free to shrink. The weld with the largest length of compensation should be welded first, because the rigidity of the structure is gradually increased during the welding process, so the weld of the first weld will be less resisted when contracted, and the stress after welding will be small. some.

Among the several welding methods commonly used in engineering equipment and steel structure welding, the submerged arc welding heat input is the largest except for electroslag, and the shrinkage deformation is the largest under other conditions such as the weld cross-sectional area. However, the quality of submerged arc welding is stable, the welding productivity is high, there is no arc, and there is little smoke, which is still widely used.

Chinese invention patent CN104148773B discloses a method for controlling the tailoring deformation of large metal tube sheets, the diameter of the large metal tube sheets is 5000mm ~ 10000mm, the thickness is 60mm ~ 400mm; the material is the welding of GB150.2 steel sheets; The slab material is welded by 2 to 3 steel plates, and the welded groove type adopts an asymmetric narrow gap U-shaped groove. The invention controls the tailor welding deformation of the tube sheet and reduces the metal consumption of the tube sheet blank.

Disclosure of invention

The object of the present invention is to provide a large-sized cylinder segment welding method with simple operation, calculate the reserved welding shrinkage compensation length and adjust the welding sequence through the empirical formula, regulate the welding shrinkage deformation, and reduce the ring welding under the premise of ensuring the welding quality. The welding deformation of the seam and the longitudinal weld seam reduces the dimensional deviation of the inner diameter of the cylinder section to meet the design requirements of the cylinder section.

In order to achieve the above object, the technical solution adopted by the present invention is as follows: a welding method of a large cylindrical section, wherein the large cylindrical section is welded by a plurality of plates, wherein the welding method comprises the following steps in sequence: According to the preset diameter of the large cylinder D _i cutting, bevel machining, welding along the longitudinal weld, and pre-bending into a cylinder section, the length of the plate L = (Di + △ D + T) * π + S * N Where ΔD is the diameter dimension tolerance, T is the plate thickness, N is the number of longitudinal welds, S is the shrinkage compensation length, 1.0 mm ≤ S ≤ 2.0 mm; alternatively, at least two barrel sections are formed into a cylinder section, and Ring welding along the ring seam.

Preferably, when the thickness of the plate is greater than or equal to 5 mm to less than 12 mm, the outer ring seam is welded first, and the inner ring seam is welded.

Preferably, when the thickness of the plate is greater than or equal to 12 mm to less than or equal to 20 mm, the inner ring seam is welded first, then the outer ring seam is welded, and finally the inner ring seam is welded.

Preferably, the welding method is submerged arc welding.

Preferably, the shrinkage compensation length S is preferably 1.5 mm.

Preferably, the material of the large cylindrical section includes, but is not limited to, carbon structural steel, austenitic stainless steel, low alloy structural steel, heat resistant steel, composite steel, nickel base alloy, copper base alloy.

Preferably, the material of the large cylindrical section is preferably austenitic stainless steel.

The beneficial effects of the invention are mainly embodied in: calculating the welding shrinkage compensation length of the reserved longitudinal weld seam and adjusting the welding sequence of the weld seam by the empirical formula, adjusting the welding shrinkage deformation, and ensuring the welding quality.

(1) The invention is simple in operation and utilizes an original empirical formula: the overall length of the plate L = (Di + ΔD + T) * π + S * N (where ΔD is the dimensional tolerance of the diameter, T is the thickness of the plate, and N is the longitudinal The number of welds, S is the shrinkage compensation length, 1.0mm ≤ S ≤ 2.0mm, preferably, the submerged arc welding, S = 1.5mm) adjusts the inner diameter of the prepared large cylinder section, and regulates the welding shrinkage of the longitudinal weld to the circle The effect of the inner diameter of the barrel.

(2) The invention is widely applicable, and according to different plate thicknesses, a unique welding sequence is used to weld the girth welds, thereby effectively reducing the inner diameter shrinkage of the cylinder segments caused by the girth welds, and ensuring the large cylinder segments after welding. The inner diameter meets the requirements of the set size, effectively controlling the size of the inner diameter of the barrel section. difference.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic view showing the structure of a cylindrical section having a circumferential weld.

Figure 2 is a schematic illustration of one embodiment of the invention.

1-cylindrical section, 2-cylinder section, 3-longitudinal weld, 4-ring weld, 5-tape measuring point, 6-ring weld shrinkage measuring point, 7-round cake filling, T-plate thickness.

The best way to implement the invention

A method of welding a large cylinder of the present invention will now be described with reference to the embodiments.

Rings are widely used in large chemical, metallurgical, aerospace and other industries. Among them, the fractionation towers such as the low-pressure tower, the medium-pressure tower, and the high-pressure tower in the air separation device, and the HYCO hydrogen production device, the liquid nitrogen washing device, the various adsorption towers in the chemical plant, and the cylinder of the fractionation tower are all common large-sized ones. Cylindrical ring. As shown in Figure 1, the large cylinder is often welded by multiple plates, including but not limited to carbon structural steel, austenitic stainless steel, low alloy structural steel, heat resistant steel, composite steel, nickel base alloy. , copper-based alloy. According to the normal procedure, after the longitudinal weld (3) is welded, use the tape measure to measure the outer circumference of the cylinder at the measuring point of the tape (5). It will be found that the outer circumference of the cylinder is shrinking compared with the length of the plate before welding. Reserve the weld shrinkage length, the longitudinal weld shrinkage will reduce the inner diameter of the cylinder; after the weld ring weld, use the tape measure to measure the outer circumference of the cylinder section at the girth shrinkage measurement point (6), and the weld shrinkage will be found. This causes a bottleneck deformation near the girth weld (4) and locally reduces the inner diameter of the cylindrical section. Since the round cake-like filler (7) needs to be filled in the fractionation column in the subsequent preparation process, it is required that the inner diameter of the cylinder section is uniform after welding. The shrinkage of the longitudinal weld and the bottleneck shrinkage deformation near the girth weld make the inner diameter of the cylinder segment difficult to control and uneven, which makes it difficult to install the round cake filler (7) in the fractionation column. Therefore, it is necessary to correct the deformation, but it will cause unnecessary work time loss and reduce production efficiency. Due to the complexity of welding stress and deformation problems, the combination of experimental testing and theoretical analysis and numerical calculation is often used in engineering practice to grasp the law, in order to achieve the purpose of predictive control and adjustment of welding stress and deformation.

In the welding method of a large-sized cylinder segment in the embodiment, the shrinkage of the longitudinal weld seam and the circumferential weld seam can be effectively controlled, and a ring member having a uniform inner diameter can be prepared. As shown in Fig. 2, the predetermined inner diameter Di + ΔD of the large cylindrical ring member (1) is 4900 mm, the height of the cylinder segment is 4000 mm, and the thickness T is 14 mm, wherein ΔD is the diameter dimension tolerance, and the cylinder is in the cylinder. The error allowed in the actual application is determined, and its range is one. Generally, from one millimeter to ten millimeters, when a round cake-shaped filler is placed in the cylinder, ΔD is determined by the allowable size difference between the inner diameter of the cylinder and the round-shaped filler to be loaded in the cylinder. The steel plate material to be rolled is S30408, and T is a plate thickness of 14 mm. According to the obtained maximum length dimension of each steel plate = 8000 mm and the maximum width dimension is 2000 mm, it is known that the finished cylindrical ring member is composed of two tubular segments (2). Each barrel section (2) has two longitudinal welds (3), and the entire finished cylindrical ring part also includes a ring weld (4). If there is no shrinkage compensation length, according to the overall plate length L = (Di + △ D + T) * π = 15438mm, π = 3.1415926, the size of each steel plate can be 8000X width 2000mm, and length 7438mm (by After cutting) X width 2000mm. Firstly, the longitudinal weld (3) is welded by submerged arc welding. The submerged arc welding parameters are current 400-600A, voltage 35.5V, speed 60-70cm/min, then pre-bending and rolling, and then buried with the same welding parameters mentioned above. Arc welding the second longitudinal weld (3). After the welding is completed, by measuring and comparing the sum L of the lengths of the two plates before welding and the outer circumference (5) of the post-weld cylinder segments, it is found that each longitudinal weld seam (3) shrinks by about 1.5 mm.

According to the original empirical formula, the overall plate length L = (Di + △ D + T) * π + S * N, π = 3.1415926; N is the number of longitudinal welds; S is the shrinkage compensation length, where S = 1.5mm, . Substituting N=2 into the above empirical formula, the overall plate length L=15441 mm can be obtained. For example, the size of the two steel plates in each barrel section can be 8000X width 2000mm, and length 7441mm (after cutting) X width 2000mm. Subsequent processes are consistent with the above. After the welding is completed, the outer circumference (5) of the cylinder section after welding is measured. It was found that the shrinkage compensation length S reserved for cutting was 1.5 mm*N (N is the number of longitudinal welds) to offset the weld shrinkage of these longitudinal welds. The difference between the actual inner diameter of the welded cylinder segment and the preset inner diameter D _i after the shrinkage compensation is within the diameter tolerance ΔD, which meets the installation requirements. According to the thickness of the plate, it is necessary to do the groove treatment before welding. For details, please refer to the national standard GB/T 985.2-2008 "Recommended groove for submerged arc welding". The chemical composition of austenitic stainless steel is detailed in the national standard GB 24511-2009 "stainless steel plate and steel strip for pressure equipment".

When the two cylinder sections are formed into the cylinder section, it is necessary to weld along the circumferential weld seam. For the plates of different thicknesses, the order of the original weld ring welds is to weld the inner circumferential joints first, usually one or two; The seams, generally one, are carried out sequentially from the inside to the outside. In the welding procedure of the ring weld in the invention, when the thickness of the plate is 5-12 mm (excluding 12 mm), the side to be welded of the steel plate does not need to be processed into a V-shaped groove, and an outer ring seam is welded first, and then an inner ring seam is welded; When the thickness of the plate is 12-20mm, it is necessary to process the V-shaped groove on the side to be welded of the steel plate, first weld the inner ring joint, then weld the outer ring joint, and finally weld the inner ring joint. In this embodiment, when welding the ring seam (4), since the plate thickness T is 14 mm, it is necessary to process the steel plate to be welded. V-shaped groove, the welding sequence adopts the first way of welding the inner ring seam first, but it is not welded, the current is 400-430A, the voltage is 35.5V, the speed is 65-70cm/min, and then an outer ring seam is welded, the current is 570-600A. The voltage is 35.5V and the speed is 60-70cm/min. Finally, the second inner ring is welded, the current is 550-570A, the voltage is 35.5V, and the speed is 60-70cm/min, so that it is completely welded. At the girth shrinkage measurement point (6), the outer circumference loss of the cylindrical section due to the shrinkage of the girth weld is only 1 mm, which effectively controls the shrinkage of the girth weld and ensures the uniformity of the inner diameter of the cylinder. Under the same submerged arc welding condition, if the original inner and outer ring welding sequence is used, for the 14 mm thick plate, the outer circumference loss of the cylinder segment due to the shrinkage of the girth weld is measured at the girth shrinkage measurement point. It is 11mm.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any simple modifications, alterations, and equivalent structural changes made to the above embodiments in accordance with the technical spirit of the present invention still belong to the technical solutions of the present invention. Within the scope of protection. In the meantime, the terms "upper", "lower", "left", "right" and "one" are used in this specification for convenience of description and are not intended to limit the practice of the invention. The scope, the change or adjustment of the relative relationship, is also considered to be an area in which the invention can be implemented without substantial changes in the technical content.

Claims

A method for welding a large cylindrical section, wherein the large cylindrical section is welded by a plurality of plates, wherein the welding method comprises the following steps in sequence:

a) According to the preset diameter of the large cylinder D i cutting, bevel machining, welding along the longitudinal weld, and pre-bending, rolling into a cylinder section, the length of the plate L = (Di + △ D + T) * π + S*N, where ΔD is the diameter dimension tolerance, T is the plate thickness, N is the number of longitudinal welds, S is the shrinkage compensation length, 1.0 mm ≤ S ≤ 2.0 mm;

b) Optionally, at least two barrel segments are formed into a cylinder segment and circumferentially welded along the circumferential seam.
The welding method according to claim 1, wherein when the thickness of the plate is greater than or equal to 5 mm to less than 12 mm, the outer circumferential seam is welded first, and the inner circumferential slit is welded.
The welding method according to claim 1, wherein when the thickness of the plate is greater than or equal to 12 mm to less than or equal to 20 mm, the inner ring joint is welded first, then the outer ring joint is welded, and finally the inner ring joint is welded.
A welding method according to any one of claims 1 to 3, wherein the welding method is submerged arc welding.
The welding method according to claim 4, characterized in that the shrinkage compensation length S is preferably 1.5 mm.
The welding method according to claim 4, wherein the material of the large cylinder segment comprises, but is not limited to, carbon structural steel, austenitic stainless steel, low alloy structural steel, heat resistant steel, composite steel, nickel base. Alloy, copper based alloy.
The welding method according to claim 6, wherein the material of the large cylindrical section is preferably austenitic stainless steel.