SU1243925A1 - Method of welding annular joints - Google Patents

Description

1243925

2. The method according to claim 1, 1 and 2 is up to the memorial value in the direction and with the fact that heat input from the heater located the power of the accompanying heating of the welding head to the welding process changes along the length of the joint from zero to the heater located front.

The invention relates to welding, in particular, to methods of welding annular joints of shells with preliminary and concomitant heating, and can be used in various fields of engineering.

The purpose of the invention is to improve the quality of welded joints by ensuring uniform heating of them.

FIG. 1 shows a scheme for the implementation of the proposed method; figure 2 - section aa on fig „1.

The method is carried out as follows.

On the tilter 1 with the drive rollers 2, two shells 3 are mounted to form a joint 4 (Figs 1 and 2). The shells have around the perimeter of the junction 4 thickened zones 5 and thin zones 6. To the junction of 4 shells, blocks 8 and 9 with heaters 10 are brought to trolleys 7. In this case, blocks 8 are fed in front of thickened zone 5, and blocks 9.

Blocks 8 and 9 are installed with a gap, in which a welding head 11 is placed at a given distance from the edges of the blocks. To control the heating temperature, use non-contact sensors 12.

Before the start of welding, the product is preheated, for which the heaters 10 are turned on in blocks 8 and 9. The heat output per unit joint length is determined by the formula

§-j - -,

R to

kW / m

where K - t is the technological coefficient equal to 0.6-1.5 kW / h degree, (which depends on the design of the heater): (Y - thickness of the zone of joint of the shells, m;

Due to the oscillatory movements of the shells with the specified amplitude, the stiros is heated evenly between the heater blocks. Specific oscillation amplitude values are assigned depending on the size of the edge and heater, i.e. from the length of the edge zones in which the nominal heating temperature is not reached due to: heat leakage to the unheated zones of the wall.

It has been established that in the initial stage of heating, when the losses are large, the 45th volume of oscillations should be equal to 3 m from the place of installation

five

0

five

T is the temperature of the heating of the joint, ° C; t - time of heating the joint, h.

It has been established that uniform heating of the junction with the use of commonly used panel electric heaters operating in an economically advantageous mode with regard to power consumption can be achieved at k 0.6 kWh / deg.M. Reduction 1 below this value increases the total energy consumption which makes the heating process economically unprofitable.

Increase K. over 1.5 kW. h / / grad.m leads to a sharp decrease in the resource of heaters and the complexity of the design, which makes it impossible to use in welding real products.

In the process of preheating, the shells 3 use rollers 2 to impart rotational oscillatory movements with an amplitude equal to 2-3 distances between the location of the welding head 11 and the roof of the block 8 or 9 - (If necessary, the welding head with Q preheating are).

Due to the oscillatory movements of the shells with the specified amplitude, the stiros is heated evenly between the heater blocks. Specific oscillation amplitude values are assigned depending on the size of the edge and heater, i.e. from the length of the edge zones in which the nominal heating temperature is not reached due to: heat leakage to the unheated zones of the wall.

welding head to the edge of the block nag-equipment. In this case, the point itself in the gap between them will go beyond the heater 10 under the heater by an amount exceeding the marginal effect zone. As the joint heats up and the heat loss decreases, the oscillation amplitude can be reduced to 2 distances, since in this case the approach of the furthest point to the edge of the heater is ensured.

The heating temperature is monitored by contactless sensors 12 mounted against the heaters of blocks 8 and 9 located in front of the welding head 11.

When the butt of the 4 shells 3 reaches a predetermined temperature, the heaters 10 are turned off, the drive of the rollers 2 of the turn-over device switches to the rotation mode of the shells 3 in the same direction with the welding speed, simultaneously turning 439254

the welding head I1 is also measured, and the welding process is completed.

Since the welding temperature in the zones located directly behind the welding head 11 is high enough, in order to save electricity, the heaters in this zone are switched to the minimum mode or turned off. As you move away from the weld zone to maintain the desired junction temperature, the power of the subsequent heaters is increased, bringing it to nominal on heaters installed directly in front of the welding head.

Thus, with this method, welding the butts of the shells, which have a thickness of pa on the perimeter, ensures uniform heating of the joints along the entire length, which increases the quality of the welded joint by eliminating the formation of cold cracks after welding.

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FIG. 2

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Editor M. Bandura

Compiled by M. Bu New Tehred I. Popovich

Order 3751/15 Circulation 1001Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, Projecto st., 4.

Proofreader E. Sirohman

Claims (2)

1. METHOD FOR WELDING RING JOINTS mainly of variable thickness, at. which along the welded joint at a predetermined distance from each other, place the welding head and heaters, pre-heat the joint and weld with concurrent heating, characterized in that, in order to improve the quality of the welded joints, by ensuring the uniformity of their heating, the heaters are placed at both sides of the welding head, during the preheating process, the product is informed of rotational vibrational movements relative to its longitudinal axis with an amplitude equal to 2-3 distances between the welding head and the heaters, and the linear heat output P of the preliminary and associated heatings is determined by. formula <^ T, K —-—, kW / m, where K is a technological coefficient equal to 0.6-1.5 kW / / h.grade; d is the thickness of the joint, m; T - heating temperature, ° C; heating hours > 2. The method according to π.1, characterized in that the linear thermal power of the concurrent heating is changed along the length of the joint from zero to a nominal value in the direction from the heater located behind the welding head to the heater located at the front ί