Method of fusion welding of steel structures and device for its implementation

FIELD: machine building.

SUBSTANCE: invention relates to the machine building, and can be used during the fusion welding of the complex steel structures. Under the suggested method the welding is combined with heat treatment with use for this of the heating element in form of the ceramic pad-heated connected via the current switch to the welding power source. Besides, the device contains the electronic and bypass switches, programmable regulator, and thermoelectric converter located on the welded structures.

EFFECT: invention reduces power consumption during post-welding heat treatment, increases strength and reliability of the critical welded structures.

3 cl, 3 dwg

The invention relates to mechanical engineering, mainly to the fusion welding of steels and alloys, and can be used in the manufacture of complex components.

Currently, almost all technological processes of creating weldments share the operation of welding and heat treatment, the only exception is pre-heating, which is usually held oxy-fuel burners with subjective control and maintain the setpoint temperature. This adversely affects the quality of the resulting welds (Heat treatment in mechanical engineering: a Handbook / ed. by Y. M. M., A. G. Radstadt - M., "engineering", 1980 p. 422-423). In addition, welding is often the canopy, without the use of forming devices, with unsatisfactory formation of the root.

Known technology of heat treatment of welds, including welding, the weld cooling in air to ambient temperature, the subsequent heating to a temperature of AU₃, shutter speed, cooling at a controlled rate (RD 153-34.1-003-01. Welding, heat treatment and control of piping systems boilers and pipelines during installation and repair of energy equipment, item 17. Heat treatment of welded joints of pipes.). But in this method, after welding, rapid cooling, which leads to appearance�of a large temperature gradient over the cross section details, the occurrence of thermal stresses of the first kind, in reduction of mechanical properties (strength and ductility), and subsequent heat treatment does not guarantee to repair surface micro - and submicrometer. In addition, this technology is energy intensive and requires additional equipment.

It is known that exposure of the alloy at a temperature of austenization allows you to control the properties of the metal, including to increase simultaneously the characteristics of strength and plasticity (Frolov A.V. Influence of phase transformations on the substructure and properties of medium-alloy steels. / Frolov A. V., Murav'ev V. I., Martynyuk, A. M., A. V. Kirikov, Zhao Litao // metallurgy engineering No. 2. - 2012. - P. 6-10). But this technology provides cooling with re-heat, which also has the disadvantage of the above method.

Method of preheating and subsequent heat treatment with the use of flexible ceramic heating mats, under which the registration and regulation of the temperature is carried out by placing on the surface of the parts being clamped thermocouple with connection to the temperature loggers on the principle of feedback (RD 153-34.1-003-01. Welding, heat treatment and control of piping systems boilers and pipelines during installation and repair of energy equipment, item 17. Heat treatment of welded joints of pipes.) has the following drawbacks:

1. Not possible to form the weld root.

2. High economic costs when carrying out heat treatment, so as to heat use a separate power source.

The same disadvantages of the method of induction heating, in which the inductor is placed on the surface connected products.

Formative devices (copper bolsters, copper-fluxing pillows, ceramic pads) allows the reverse roller one-pass unilateral weld, but implies additional equipment for operations prior, concurrent heating and subsequent heat treatment.

To address the shortcomings we propose a method of welding, combined with the heat, including welding, metal is cooled to a temperature of austenization, holding at this temperature until the beginning of the polymorphic transformation and subsequent cooling.

In the proposed method, the operation of welding, pre-heating and immediate cooling and the formation of root welds combined. For this purpose, a power source for welding, the circuit of which is embedded proportional-integral-differential (PID) controller and a system allowing pre-heating and maintaining the desired temperature during periods of inactivity with�arched arc (coated electrode, sweep from the slag, etc.). This will increase the mobility of the equipment, efficiency and economic efficiency of operations of heat treatment and the quality of welded joints by forming them on ceramic pad-heater, which is located on the reverse side of the seam.

The device for preliminary heat treatment of workpieces and final heat treatment of the weld (Fig. 1) comprises: a welding transformer (Tr), electronic switch (EK), bypass switch (BC), the switch current ceramic heater (It), software controller (P), control panel (CP), ceramic heater (KN), a thermoelectric Converter (TC). Structurally, BK and EK are placed in the vicinity of the welding transformer. Ceramic heater is placed directly on the welding workpieces. Thermoelectric Converter is fixed on the welding workpieces in the vicinity of the weld. Control panel, switch To controller and P are accommodated in a separate building close to the welding station.

Technological process of welding is carried out as follows. After turning the unit controls PU translated to "IT" (heat treatment). PU disables the bypass commute�PR BC and connects the ceramic heaters KN through the switch K. Controller R controls the operation of the switch EC based on the PID algorithm, providing heating of billets to the desired temperature at the required algorithm. Information about the temperature of the workpiece is supplied to the regulator from thermoelectric Converter TP. After heating the billets to the desired temperature program controller R stops, the PU authorities are transferred in mode "C" (welding). PU disables the switch and pass switch includes BC. In this mode welding. After welding, the PU authorities are translated into "WE" and the regulator R is translated into the work programme 2 - heat treatment of the weld. Then switch BC is disabled and the switch To turn on. Controller R controls the heating of the ceramic heater via the controller EC and controls the temperature of the metal by means of a thermoelectric Converter.

Schematic diagram of the apparatus shown in Fig. 2. Electronic switch made under the scheme triac power control on the elements R1-R3, C1-C2, VS1-VS2, WP1-WP2. Variable resistor R1 regulates the maximum heating power. Filter chain R3-C2 prevents the breakdown of the triac VS2 shots from the mains voltage. Placed on the radiator of the triac VS2 thermal fuse for PR�Iset simister from overheating.

As the bypass switch used contactor K1.

As a software controller used a PID controller ARIES TRM.

The remote control is made on the contactor K2 and the buttons CN-CN under the scheme with latching. Indicator light HL1-HL2 display devices.

When implementing a device used in the scheme the following elements:

- capacitors: C1 = MBM-0.1 µf - 150; C2 = MBM-0.1 µf - 500;

- fuse WP1=WP2-60;

- thermal fuse WP2=TZD-084;

- resistors: R1=CP3-VM - 0,5-220 kOhm; R2=MLT - 0,125-6,8 kω; R3=MLT - 1-68 Ohms;

- dinistor VS1=DB3;

- semestr VS2=part no bta40-600;

transformer Tr;

- contactors: K1; K2;

button KN, KN;

- indicator lights HL1, HL2;

- ceramic heater KN;

software controller: P=ARIES TRM.

Welding on ceramic pad - heater is as follows: on the reverse side of the root pass with minimal clearance is a ceramic heater lining, consisting of serially connected with each other by flat ceramic nichrome wire elements with through holes (Fig.3). In the Central part assembled so Mat are arranged ceramic elements with a groove, the dimensions of which are determined by the necessary geometrical parameters of the root pass weld with�organisations and mounted directly below it in the line of intersection for the purpose of forming back side of the weld. At a distance of 20-25 mm from one of the abutting edges between ceramic Mat and detail install a thermocouple for temperature control. The surface of the front side and root isolate of thermally insulating material. By electrocontact heating nichrome filament disposed within the ceramic element heats the metal parts to be joined to the desired temperature. Upon reaching the desired value of welding. During the period of inactivity of the arc to control the heating temperature makes the analysis of compliance of the set temperature actual value and, if necessary, reheat the abutting edges. After finishing the welding process, the welder immediately translates the heating device to heat treatment and shall, as necessary, additional insulation.

When welding long joints of sheet structures it is necessary to use multiple sources of power, provided with a device for temperature control. In this case, the joints are divided into several sections, the number of which depends on the length of the joint and the welding is carried out simultaneously by several welders scheme obratnoystorone method. The beginning and the end of the process of preheating, welding and heat treatment should�n be carried out synchronously.

When carrying out the heat treatment device temperature regulation (URT) controls and stabilizes the rate of heating and cooling of the welded joint, as well as the temperature and exposure time. After the operation the Ourthe turns off automatically. The welded connection can be transferred to quality control.

The proposed method was tested in the welding of samples of alloy 30KHGSA. Mechanical properties of welded joints are presented in the Table.

The method can be carried out both in the workshop and at Assembly sites, as in welding of steels and alloys and non-ferrous metals, butt joints of sheet structures, and pipe blanks as rectilinear and curvilinear designs. Can be used in automotive, shipbuilding, aviation, rocket production, in the production of objects of oil refining complex in construction and railway transport in combined manufacturing operations, and for carrying out exclusively preheating and heat treatment.

1. Method of fusion welding of steel structures, including preparation of edges for welding, preheating of the welded edges, fusion welding with the formation of the weld root and the heat treatment of the weld seam, wherein said preheating and heat treatment�m is carried out using ceramic heating elements, which are mounted on welded structures, characterized in that the ceramic heating element using ceramic pads-heaters, made with the possibility of regulation of the heating rate by using at least one welding power source in the absence of a welding arc and which have on the reverse side of the root.

2. A method according to claim 1, characterized in that depending on the length of the butt joints the butt joint designs is divided into sections, welding which are simultaneously under the scheme obratnoystorone method using the welding power sources equipped with a device regulating the temperature, and start and end the processes of welding and heat treatment of each plot for a given regime is carried out synchronously.

3. A device for fusion welding of steel structures, containing at least one welding power source with welding transformer, and electronic bypass switch, ceramic heating elements, the switch current of the mentioned elements, software controller and a thermoelectric Converter made of welded constructions, characterized in that the ceramic heating elements made in the form of the ceramic�fir linings of heaters to control the rate of heating by the welding power source in the absence of a welding arc and installation on weld design on the reverse side of the root seam, and programmatic controller is executed in the form of a proportional-integral-differential controller.