Method for assembling welded large-size thick-sheet orthotropic plates of carbon low-alloy steels for automatic welding

FIELD: processes for making large-size thick-sheet orthotropic plates of carbon low-alloy steels in different branches of industry, particularly for bridge building.

SUBSTANCE: method comprises steps of relative orienting members of orthotropic plates; tack welding oriented members by means of non-consumable tungsten electrode in mixture of shield gases Ar (95 - 97)% + (3 - 5%) CO2 ; performing automatic continuous-seam welding and then trimming surface of welded seam. It allows simplify method for making welded large-size thick-sheet orthotropic plates of carbon low-alloy steels.

EFFECT: lowered labor consumption, shortened time cycle for making enhanced-quality plates, improved reliability of welded structures.

6 dwg, 1 ex

 

The invention relates to welding, in particular to a method for manufacturing large-sized plate of orthotropic plates, and can be used in various industries and especially in the bridge.

Fabrication of large thick-walled structures using welding requires a preliminary orientation of its elements in space with the help of additional tools and devices.

So, there is a method of manufacturing large-sized plate designs, which is as follows.

Take the structural members being welded. On the appropriate equipment to produce edging on the elements for welding. The booth shall be welded Assembly of structural elements and fix them in position by means of Assembly jigs, take welding collected items and remove the jigs, and then do the final welding a continuous bead (1).

The disadvantage of this method is that it requires the edges to be connected planar elements for welding, and this requires considerable additional effort. In addition, welding the “butt” is the most common connection elements, in practice, often required when the Orc parts t-connection “in the corner”.

A known method of making t-joints using arc welding fusing electrode, which is that on the wall, perform a one-way cutting edge under varying from weld root angle equal to 45 to 60°at the height of 5 to 6 mm and then at an angle equal to from 25 to 45°. When performing welding spot heat have on the shelf behind the line of intersection of the vertical plane of symmetry of the wall with a shelf at a distance equal to 0.7 to 0.8 half the thickness of the wall, and move it in the welding process with a rate equal to from 1.7 to 8.0-magnitude gap between the wall and shelf. For manual arc welding, the gap between the wall and shelf set equal to from 3 to 4.5 mm, and the spot heating move at a rate of from 1.7 to 3.0 magnitude of the gap between the wall and shelf (2). This method is as follows. Produce weld corner weld Tauri connection of low-alloy high-strength steel brand HAT thickness of 20 mm using a manual welding electrodes UONI-13/55 diameter of 3 mm and the automatic welding in carbon dioxide - wire SV-08G2S diameter of 1.2 mm

The disadvantage of this method Tauri connection elements also lies in the need to handle complex profile of the weld for metal-working machines that Tr is require significant additional costs and increases the cost of manufactured products.

Also known technology for manufacturing large-sized plate of orthotropic plates, which consists in conducting a preliminary orientation in the conductor plate and the longitudinal ribs, their mutual fixing and tighten using jacks mobile portal. Then in the docked position with the two sides carry out potholders ribs to a plate with a length of 50 mm each, maintaining between them a distance of 300-500 mm, the Tack conduct manual arc or semi-automatic welding consumable electrode in a mixture of shielding gases argon and carbon dioxide, and the percentage ratio between them is 80 and 20 respectively.

After potholders automatic continuous welding seam are also consumable electrode, but under a layer of flux an-348A (3).

The manufacture of heavy plate t-joints with this technology is accompanied by the occurrence of repetitive welding defects: high gain and leg weld, its bumpy in places productions tack, which necessitates cleaning such a surface abrasive wheels. A large amount of Stripping increases the complexity of manufacturing of finished products by 20%on average, leads to additional energy consumption, abrasive wheels and tools, as well as deals on their surface risks from the abrasive is s circles, that reduces the reliability of welded structures, in the case of the inevitability of such Stripping the risks of abrasive should be directed along the efforts of the current in the element.

The closest in technical essence and the achieved result claimed is a method of manufacture of welded large-plate t-joints, which is taken as a prototype(4).

The method includes the relative orientation of elements Tauri connection, prior to their intermittent tack seam, and the final welding carry out high-speed rotation of the arc by rotation of the electrode, thus continuously monitors the arc voltage or the magnitude of the welding current through the tracking system. The method provides a contactless real-time determination of the presence and magnitude of the tack weld and allows you to optimize the management of welding.

However, this method is not without flaw, which is the complexity of its implementation, in particular the need for a fairly complex tracking systems determine the location of the seams of the mitts.

The goal is to simplify the method of manufacturing it welded large, plate t-joints of low-alloy steels, in particular of orthotropic plates without uslojnennye hardware implementation.

The technical result is a simplification of the method is due to the fact that the tack oriented elements perform non-consumable electrode shielding gas without additives, and continuous welding seam automatically consumable electrode under a layer of flux or shielding gas. The shielding gases for potholders form of a mixture of argon and carbon dioxide in the ratio of AG(95-97)%, CO2(3-5)%, and the non-consumable electrode made of tungsten.

1 shows a diagram potholders ribs and plates nalawadi electrode; figure 2 - cross section along a-a in figure 1; figure 3 shows a diagram of the final welding of the ribs and plates, figure 4 - cross section b-B figure 3.

The method is as follows. Take a flat sheet orthotropic plate 1 is placed on the bed of the conductor 2 and press straps (not shown), label productions of the longitudinal ribs 3, put them on the stove, placing each in the safety device of the bar 4 and fixing in position with the screw 5. To hold the ribs in a vertical position at the opposite end of the second set of end yoke 6. Preload ribs 3 to the plate 1 is performed by the portal Jack 7. Then, in the assembled state is tack ribs 3 to the plate 1 a nonconsumable tungsten electrode without additives (figure 1 for milagrodirksen only one edge). Tack the seam 8 is formed only due to the melting of the base material without additional additives from the side, and then submerged arc welding the leg seam 9 and form remain constant throughout (figure 2 and 4).

As a protective environment the selected mixture of argon with carbon dioxide in a ratio of AG(95-97)% CO2(3-5)%, respectively. The ratio of argon and carbon dioxide in the mixture helps to ensure minimal erosion of the tungsten electrode is approximately equal to erosion when welding in argon, and good weld formation (figure 3).

Welding t-joints low-alloy and carbon steels large thickness of the tungsten electrode without additives protected argon impossible due to poor formation of a seam, characterized by chain fistula around the seam (6). Welding in the gas mixture Ar+CO2when the content of CO2more than 5% leads to increased erosion of the tungsten electrode.

Potholders are length L=50 mm with a spacing of L=300 to 400 mm on both sides of the ribs with the following conditions: welding current JSt=270-320S, the arc voltage U=12 to 14, the diameter of the tungsten electrode is 4 mm at a flow rate of the mixture of gases - 8 l/min After the operation potholders ribs to the plate final non-consumable electrode welding is carried out on dogdugum the machine with the two sides of bra under a layer of flux an-348A.

This automatic welding of t-joints with a metal thickness of orthotropic plates from 10 to 40 mm conduct continuous suture in the following modes: amperage JSt=250-300A voltage Uarc=26-28V, welding speed VSt=23-27 m/h, the wire feed speed Ue=135-156 m/h diameter of the consumable electrode is chosen equal to from 2 to 3 mm.

After welding carry out dismantling ready orthotropic plates of the conductor.

Example

In the manufacture of large orthotropic plates of low-alloy steel grades 10HSND and 15HSND for bridge structures grazing leaf width up to 3000 mm up to 15000 mm laid on the bed of the conductor, is firmly fixed and label the positions of installation of the ribs, which have a length of up to 15000 mm, a thickness of 10-40 mm and a height of 150-250 mm

Ribs without the removed edges are installing on a flat sheet with a gap from 0 to 1.5 mm using a traverse on a marking at a distance from each other up to 300 mm and fixed in the conductor as described above.

The number of ribs of orthotropic plates is determined by the load on pavement design. Tack edges is made without additives at the facility for argon-arc welding-type UDSU-302 non-consumable electrode made of tungsten brand EVI-3 with a diameter of 4 mm on the machine or manually. As the protection is based environment is used, the optimum mixture of argon and carbon dioxide in proportions respectively (95-97) - (3-5) percent. Measurement of flow of the protective gas was produced with the help of rotameter PC-3 and amounted to 8 liters per minute.

The optimum flow rate and composition of the gas mixture is determined by the invariance condition of the shiny surface of a tungsten electrode, with the exception of education at the end of the “crown”, and its minimal erosion.

The depth of penetration of the tack in the corner Tauri connection is 2.5-3 mm, which is sufficient for reliable fixation of the ribs relative to the flat sheet orthotropic plate. Perform operations potholders elements orthotropic plate nonconsumable tungsten electrode without additives causes as their internal penetration without the formation of external seams (figure 3), which provides further during the final welding under flux uniformity and high quality Tauri connection, i.e. in this case there is no need to have a complex system that tracks the beginning and the end of the tack weld, and therefore constantly changing modes of welding. The size of the leg of the weld is in the range of 6-8 mm (figure 4).

When selecting execution modes tack non-consumable electrode without additives and consumable electrode submerged arc welding are guided by the principle, the thicker the elements connections orthotropic plate, the bol is the highest shift towards the upper limit value, specified in the description of their tolerances.

Thus, when the maximum thickness of the flat sheet of plate and stiffeners equal to 40 mm will be used and the maximum allowable maximum welding modes, namely the strength of the weld current JSt=300A, the voltage Uin=28V, welding speed 23 m/h, the wire feed speed Ve=135 m/h, the electrode diameter D=3 mm

Because with this method of manufacture of welded large plate of orthotropic plates is formed tuberosity suture, flows, as a consequence of this and do not require abrasive cleaning of the obtained joints, which will reduce the complexity of fabrication of the bridge structure, to reduce manufacturing cycle and to improve the reliability of welded structures.

Sources of information

1. USSR author's certificate No. 806310 23 To 9/00 “Method of manufacture of welded large plate structures.” Published 23.02.81, bull. No. 7.

2. USSR author's certificate No. 1696207 23 To 9/73 “Method for arc welding of t-joints”. Published 07.12.91,

3. Factory standard fabrication structures of bridges STP 012-2000.

4. The Japan patent No. 6071664 “Method detection tack weld”. Published Bulletin “inventions of the world”. VIP No. 11/97 (prototype).

The method of assembling the NVA who were large plate of orthotropic plates of carbon, low-alloy steels under automatic welding, including the relative orientation of their elements, pre-tack with subsequent automatic continuous welding seam, trimming received its surface, characterized in that the tack oriented elements provide a nonconsumable tungsten electrode in a mixture of shielding gases AG 95-97% + 3-5% CO2.



 

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