RU2714279C1 - Method of butt fusion of common link of mooring chain of class r6 - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention is intended for butt fusion of common link of R6 mooring chain. Proposed method comprises welding machine with four electrodes. Pre-heating is carried out with intermittent fusion followed by stable continuous fusion process. Drain is performed, at the same time power is switched off after a certain period of time during settling. During settling, pressure of fixed electrodes (1), movable electrodes (2) and settling cylinder is maintained during cooling time. Weld seam (4) in joint has sufficient resistance to deformation to prevent cracking of welded port caused by annular elastic recovery.

EFFECT: method ensures production of chain links meeting the requirement of mechanical properties for R6.

2 cl, 2 dwg

Description

FIELD OF TECHNOLOGY

The present invention relates to marine mooring chains, and in particular, to a flash butt welding method suitable for an ordinary link of a mooring chain of class R6, ∅84 mm.

BACKGROUND OF THE INVENTION

Marine mooring chains are widely used in large marine engineering structures and are survivability chains used in extremely adverse marine conditions to ensure safety. As marine engineering evolves toward the deep ocean, various equipment has increasingly increasing requirements for mooring chains. To increase the working load of the mooring chain, it is necessary to improve the technical characteristics of the chain, and it is also necessary to increase the class of chain strength. However, despite the increase in size and specialization of marine equipment, the increase in chain diameter is limited by many factors, and a mooring chain with a higher strength class is usually required to overcome impacts caused by adverse conditions, for example, extremely adverse marine conditions. Mooring chains can be classified into several classes, for example, R3, R3S, R4, R4S and R5, according to the mechanical characteristics of the mooring chains. As an indispensable safety device for offshore oil exploration rigs and fixed assembly plants, consumers have increasingly high requirements for the operation and reliability of mooring chains. Over several decades of development, mooring chains have been upgraded from R3 and R3S to R4 and R4S, and even to the existing R5, achieving faster development. At present, mooring chains are no longer a simple product in heavy industry, but a high-tech product that has a predetermined industrial limit and is in line with new marine engineering.

Compared to R5 mooring chains, the strength of R6 mooring chains is increased by 10%. To increase the strength of the product, from one aspect, you need to change the heat treatment procedure, and from another aspect, you need to add a certain amount of alloying elements. However, such a change in composition may adversely affect welding performance. The mooring chain has a relatively high requirement for constancy of operation, and a defect in a link can lead to a failure of the entire chain. Therefore, a large number of tests are required to select the optimal welding method parameter from a narrow strength range, so a class R6 mooring chain has better mechanical properties.

SUMMARY OF THE INVENTION

The objective of the present invention is to solve the above technical problems.

The objective of the present invention is achieved by using the following apparatus: apparatus for flash butt welding of an ordinary link of a mooring chain of class R6, including an ordinary link of a mooring chain, where the middle section of the upper link of an ordinary link of a mooring chain is provided with a weld, fixed electrodes are placed on the left side of the welded seam, fixed electrodes include the upper fixed electrode and the lower fixed electrode, the movable electrodes are placed on the right side non-weld, the movable electrodes include the upper movable electrode and the lower movable electrode, the upper stationary electrode and the upper movable electrode - both located behind the ordinary link of the mooring chain, and the lower stationary electrode and the lower movable electrode - both placed in front of the ordinary link of the mooring chain.

The fusion welding method includes the following steps:

A) preparation for welding: after the manufacture of R6 class mooring chain links, the location of an ordinary mooring chain link between four electrodes, where four electrodes are classified into two groups, the upper fixed electrode and the lower fixed electrode form one group of stationary electrodes, the upper movable electrode and the lower movable the electrode form one group of movable electrodes, and an ordinary link of the mooring chain is attached to the welding machine by sharing four electrodes;

B) pre-heating with reflow: individually connecting the stationary electrodes and movable electrodes to the secondary side of the welding transformer, and the formation of intermittent reflow when the welded end faces quickly contact each other and quickly separate from each other one or more times after applying voltage;

C) a stable continuous process of melting: pushing the movable electrodes at a given speed until the control of the fusion value is over, where the fusion value is a decrease in the gap between the stationary electrodes and the movable electrodes, and is from 16 mm to 18 mm;

D) upset: applying sufficient upset pressure to the welded end faces, quickly reducing the gap at the butt, stopping the jumper rupture, displacing the molten metal and oxide inclusion from the end faces, achieving the specified upset, and causing a specific degree of plastic deformation in the joint area to facilitate repeated crystallization, the formation of co-crystalline particles and obtaining a hard butt joint;

E) continued upsetting with power on: skipping the power off immediately after reflowing, and turning off the power after a period of time during precipitation; and

F) maintaining pressure during upsetting: maintaining the pressure of the stationary electrodes, movable electrodes, and the cylinder for upsetting for a certain period of time, i.e., cooling time, so the weld at the joint has sufficient deformation resistance to prevent cracking of the weld port caused by the annular elastic recovery.

The method of the present invention is appropriate, ensures that the welding of the chain links satisfies the requirement for the mechanical properties of R6, and the distribution and application of the method have good economic and social benefits.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a main view of the installation structure in accordance with the present invention; and

Figure 2 is a top view of the installation structure in accordance with the present invention.

In the figures:

1: Fixed electrodes; 2: Movable electrodes; 3: Ordinary link of the mooring chain; 4: Weld; 101: Upper fixed electrode; 102: lower fixed electrode; 201: Upper movable electrode; 202: Lower movable electrode.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is further described below with reference to the accompanying drawings, but this is not intended to limit the present invention.

Apparatus for flash butt welding of an ordinary link of a mooring chain of class R6 includes an ordinary link of 3 mooring chains. The middle section of the upper link of the ordinary link 3 of the mooring chain is provided with a weld 4. Fixed electrodes 1 are placed on the left side of the weld 4, and the fixed electrodes 1 include the upper fixed electrode 101 and the lower fixed electrode 102. The movable electrodes 2 are placed on the right side weld 4, and the movable electrodes 2 include an upper movable electrode 201 and a lower movable electrode 202. The upper fixed electrode 101 and the upper movable electrode 201 are both located behind the ordinary link 3 of the weld rtovnoy chain, and a lower fixed electrode 102 and the lower movable electrode 202 - the two are placed in front of an ordinary member 3 mooring chain. The method includes the following steps:

A) preparation for welding: after the manufacture of links of a mooring chain of class R6, the location of the ordinary link 3 of the mooring chain between four electrodes, where four electrodes are classified into two groups, the upper fixed electrode 101 and the lower fixed electrode 102 form one group of fixed electrodes 1, the upper movable the electrode 201 and the lower movable electrode 202 form one group of movable electrodes 2, and the ordinary link 3 of the mooring chain is attached to the welding machine by sharing four Electrode;

B) preheating with reflow: individually connecting the fixed electrodes 1 and the movable electrodes 2 to the secondary side of the welding transformer, and the formation of intermittent reflow when the welded end faces quickly contact each other and quickly separate from each other one or more times after applying voltage ;

C) a stable continuous reflow process: pushing the movable electrodes 2 at a predetermined speed until the control of the fusion value ends, where the fusion value is a decrease in the gap between the stationary electrodes 1 and the movable electrodes 2, and is from 16 mm to 18 mm;

D) upset: applying sufficient upset pressure to the welded end faces, quickly reducing the gap at the butt, stopping the jumper rupture, displacing the molten metal and oxide inclusion from the end faces, achieving the specified upset, and causing a specific degree of plastic deformation in the joint area to facilitate repeated crystallization, the formation of co-crystalline particles and obtaining a hard butt joint;

E) continued upsetting with power on: skipping the power off immediately after reflowing, and turning off the power after a period of time during precipitation; and

F) maintaining pressure during upsetting: maintaining the pressure of the stationary electrodes 1, movable electrodes 2, and the cylinder for upsetting for a certain period of time, i.e., cooling time, so the weld 4 in the joint has sufficient deformation resistance to prevent cracking of the weld port caused by ring elastic recovery.

During a specific embodiment, the following welding parameters are used in the present invention.

1) Reflow rate: 16 mm - 18 mm

It is necessary to select a fusion value to ensure that when the fusion process ends, the two end faces of the welded joint are uniformly heated, a sufficient molten metal layer is formed, and the plastic deformation temperature is reached at a specific depth, so that a high-quality connection is obtained during upsetting. R6 class mooring steel contains a relatively large number of Mo elements and a small number of trace elements, such as V, Nb and Ti, and these elements can greatly increase the heat resistance of the material. However, in order to ensure that sufficient plastic deformation is formed during upsetting, it is necessary to properly increase the amount of fusion, and it is necessary to extend the time of fusion.

2) Draft length: 19 mm - 22 mm

When the amount of precipitation is relatively small, residues of liquid metal may be present in the port, and this can easily cause defects, for example, porosity, shrinkage, cracking, cast structure, gray stain, oxide inclusion and through welding, which impair the mechanical properties of the joint. Therefore, a relatively low impact strength is obtained. When the amount of precipitation is relatively large, an excessive amount of ductile metal is displaced, increasing the difficulty of removing the burr of the compound. In addition, the impact strength of the joint is reduced due to partial rupture of the joint and strong curvature of the crystalline pattern. Considering the high strength of R6, the deformation resistance is large during upsetting. Therefore, the draft length is suitably increased to eliminate loose settlement.

3) Reflow rate: 1.8 mm / s - 2.0 mm / s

Whether the method of flash butt welding is embodied without problems depends on the choice of the flash speed. Only when the proper welding speed is selected, the intensity and stability of the reflow can be ensured and the optimum heating effect is achieved. If the material to be welded contains a material having a relatively large number of easily oxidizable elements or having good electrical and thermal conductivity, the reflow rate is relatively high.

4) Secondary voltage: 14 V - 16 V.

Secondary voltage can affect the output power and thermal efficiency during welding. From the tests, it can be found that when the secondary voltage is excessively low, the fusion is unstable, and a fusion suspension caused by a short circuit of the weld can easily occur; and when the secondary stress is excessively high, a relatively deep fire cavity may remain at the end face, and the fire cavity cannot completely close up during precipitation, easily causing defects such as slag inclusion and shrinkage, and adversely affecting the quality of the joint.

5) System pressure: 16 MPa - 20 MPa

Since a mooring chain of class R6 has high strength and high resistance to deformation, in comparison with low-chain links with the same technical characteristics, it is necessary to properly increase the system pressure to avoid insufficient precipitation caused by electrode slipping during settlement.

6) Continuous draft with power on:

Continued upsetting with power is implemented to provide additional heat to the weld after the reflow stops to help eliminate liquid metal and perform plastic deformation. A mooring chain of class R6 has a high voltage, and after increasing draft with power supply, the weld can be fully connected, eliminating cracking of the weld after removing the draft force.

7) Cooling time: the high-strength chain has greater deformation resistance, and it is necessary to extend the cooling time after upsetting to prevent elastic recovery.

The above embodiment of the present invention is only an example clearly describing the present invention, but is not intended to limit the scope of protection of the present invention. All equivalent technical solutions also fall within the scope of the present invention, and the scope of protection of the present invention is limited by the claims.

Claims (12)

1. The method of butt welding by fusion of an ordinary link of a mooring chain of class R6, comprising the following stages, which are carried out: A) preparation for welding, in which an ordinary link (3) of the manufactured mooring chain of class R6 is placed between four electrodes containing the upper stationary electrode (101) and the lower stationary electrode (102), which form one group of stationary electrodes (1), and the upper a movable electrode (201) and a lower movable electrode (202), which form one group of movable electrodes (2), and attach an ordinary link (3) of the mooring chain to the four shared electrodes of the welding machine; B) preheating with reflow: individually connecting the stationary electrodes (1) and movable electrodes (2) to the secondary side of the welding transformer, and the formation of intermittent reflow when the welded end faces quickly contact each other and quickly separate one or more times after applying voltage; C) a stable continuous process of reflow: pushing the movable electrodes (2) at a given speed until the control of the amount of fusion is over, and the amount of fusion is a decrease in the gap between the stationary electrodes (1) and the movable electrodes (2); D) upsetting: applying sufficient upsetting pressure to the welded end faces, quickly reducing the gap in the joint, stopping the jumper rupture, displacing the molten metal and oxide inclusion from the end faces, achieving the specified amount of upsetting, and causing a specific degree of plastic deformation in the joint area to facilitate repeated crystallization, the formation of co-crystalline particles and obtaining a hard butt joint; E) ongoing upsetting with power on: skipping power off immediately after reflowing is completed, and turning off the power after a period of time during precipitation; and F) maintaining pressure during upsetting: maintaining the pressure of the stationary electrodes (1), movable electrodes (2), and the cylinder for upsetting for a certain period of time, i.e. cooling time, thus, the weld (4) in the joint has sufficient resistance deformations to prevent cracking of the weld port caused by annular elastic recovery, the following welding parameters are used: the amount of fusion from 16 mm to 18 mm; precipitation length from 19 mm to 22 mm, reflow rate from 1.8 mm / s to 2.0 mm / s, secondary voltage from 14 V to 16 V, system pressure from 16 MPa to 20 MPa. 2. A welding machine for flash butt welding by fusion of an ordinary link of a mooring chain of class R6 by the method of claim 1, comprising: fixed electrodes (1) located on the left side of the weld (4) provided on the middle section of the upper link of the ordinary link (3) of the mooring chain, the fixed electrodes (1) containing the upper stationary electrode (101) and the lower stationary electrode (102) , movable electrodes (2) located on the right side of the weld (4), and the movable electrodes (2) comprise an upper movable electrode (201) and a lower movable electrode (202), the upper stationary electrode (101) and the upper movable electrode (201) are each placed on one side of the ordinary link (3) of the mooring chain, and the lower stationary electrode (102) and the lower movable electrode (202) are each placed on the opposite side of the ordinary link ( 3) mooring chain.

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