Design and calculation of welding positioning mode for cross beam*

Jing-yun ZHAO, Xue-li CHENG

Henan Mechanical and Electrical Engineering College, Xinxiang 453002, China

Design and calculation of welding positioning mode for cross beam*

Jing-yun ZHAO?, Xue-li CHENG

HenanMechanicalandElectricalEngineeringCollege,Xinxiang453002,China

In this paper, based the processing method of cross beam used in steel structure factory building as the research object, because the cross beam without special profiles, so we need two profiles spell-welding. The ordinary submerged arc welding equipment cannot normal applied welding, and manual spell-welding cannot guarantee the quality, due to structural constraints. In order to ensure accuracy of cross beam welding, before the design of special welding machine, the error calculation was conducted in view of positioning method of special welding machine, and find out the reasonable positioning mode, provide theoretical support for manufacturing special welding machine.

Cross beam, Spell-welded, Positioning

1.Introduction

In 2001, SETC (the state economic and trade commission) approved the light steel structure residential buildings as the breakthrough point of the steel, and officially listed as national key innovation technology, steel structure factory building can shorten the construction period, especially in metallurgy, electric power, heavy machinery plant, etc. the larger span steel support is needed, at the same time some special venues, in order to highlight the industrial beauty, requires structural design reflects the architectural features, such as the Beijing Olympic Games main stadium is the use of steel structure house, and most of the venues of the Shanghai World Expo is built with steel structure. Chinese steel production reached 8.8 tons, which also provides the material basis for further application of steel structure building.

Although from the outside, steel structure workshop coordinated, but due to the different nature of the various production companies, types of plant layout are different, and therefore it requires more types of steel components to complete the assembly workshop. In the construction of steel structure the beam is an important bearing components, mainly subjected to bending and distortion moment, if divided by function, the type of beam is divided into floor beams, crane beam, tower beams, according to the classified section of the beam, the beam is divided into type steel beams and composite beam, section type is commonly used steel structure component of the beam, as is shown in Figure1.

2.Application and positioning mode of the cross-beam

Cross-beam steel structure factory building is a common building component, which belongs to a combination of cross-section beam. Cross-beam is used as the column of steel structure, and four sides can made a four-way connection structure, as shown in Figure 2. Plant of different structure, different stress conditions, cross-sectional dimensions of the cross-beam, are from 100 mm to 800 mm. Cross-beam yield little, do not belong to the national standard profiles. Production companies are to buy steel, will be one of the beams from the intermediate mesh, to obtain two T steel, welding with the addition of a steel composite. The current standard 工-beam section size height minimum size is 100 mm, the maximum height of 630 mm, therefore the minimum and maximum height of the cross beam are respectively 100 mm, and 630 mm, if the cross-sectional dimension exceeds 630 mm, is the use of multiple pieces of steel plate after cutting welding.

Figure 1. Cross section form of the common steel structure beam

Figure 2. The connection sketch of cross beam

Submerged arc welding only can be flat, T-shaped steel fillet weld easy to collapse, to ensure weld penetration neat appearance but also welding, must adopt ship welding, in order to facilitate welding, before welding machine, cross beam need rotated 45 degrees through indexing machine, making fillet weld symmetrical upward. Because of the cross-beam component longer needs a total of four seam welding, using special welding fixture fixed position.

According to the structural requirements, submerged arc welding trolley moving guide can only be set on the outside of the cross-beams, cross-sectional dimensions of steel structure is large, the cantilever is too long, poor stability. And with the guide translation, the accumulated error due submerged arc welding trolley guide rail and the cross beam are not parallel will produce more and more, and even affect the welding seam offset. Design ideas of special welding machine is position from the internal cross beam, eliminate displacement error of the welding dolly in moving process.

Internal positioning mainly consider the following three waysrespectively, is through the use of unilateral localization of T slots, using the cross outer edge positioning and using cross Inner edge localization, as shown in Figures 3～5.

Figure 3. Unilateral positioning welding

Figure 4. Cross outer edge positioning welding

Figure 5. Cross inner edge positioning welding

Using T-slot edge location, the main advantage of the T-slot of the upper edge and the edge as a positioning surface, the lower edge of an elastic auxiliary support is not disengaged from the positioning surface. This positioning method has the advantages of simple structure, the main problems are: the support of the cantilever tip is too long, the move will generate vibrations, thus affecting the arcing effect. Unilateral positioning accuracy depends on the installation manufacturing errors of T plate, installation and manufacturing errors on the great influence of weld positioning precision. Ship welding, conductive tip relative to the weld pair requirements very strict, to take unilateral positioning can not guarantee pair. So whether it is inside or outside the edge, as long as long while using be considered as the V-grooves, by means of V-grooves on the neutral can easily achieve positioning[1]. Figure 4 shows the cross outer edge location, and Figure 5 shows the cross inner edge location, in what form the specific needs further calculations.

3.Calculation of positioning error

The errors are mainly due to three factors using both sides of the cross-beam positioning, the first is caused by manufacturing errorδDof the both sides of positioning surface and a conductive tip installation location; second is caused by angle deflectionδathat T-shaped steel welding position is not accurate, third is caused by surface irregularities Φ of T-shaped steel, as shown in Figure 6, the following were calculated, in order to make qualitative analysis, calculated by 40b mode工-shaped steel, the main parameters of 40B for heighth=400, widthb=144, thicknessd=12.5, feet thickt=16.5.

3.1.Positioning error caused by locating surface and welding position machining errorsδD

For the convenience of calculation, the two positioning point of tangency, two locating surface is tangent to a circle, the radius of the circle is simplified as distance of a conductive tip and positioning surface. The manufacturing error of the circle size is positioning error caused by the machining distance error[2]. As can be seen from Figure 6(a), distance ofO1O2can be regarded as the positioning error:

According to the Handbook of mechanical design, welding connection device manufactured using IT7 level accuracy, using the outer edge of the positioning, the basic size of 250 mm, positioning error is 0.052 mm, the positioning using an inner edge, the basic dimensions of 120 mm, the positioning error of 0.040 mm.

3.2.Positioning error caused by T-beam angle inaccurateδa

The theory position of T-shaped steel and H-shaped steel should be straight, but the actual clamping and 工-shaped steel rolling process may produce angular errors, from Figure 6(a)O1O3distance can be regarded as the positioning error.δa=a-90°

(3)

(4)

According to the Ministry of Metallurgical Industry recommended standard YB (T) 56-87 1.1.2.4 requirements, the slope of the outer leg (leg) shall not be more than 0.015b. Theδa=arctg (0.015b/b) =artg0.015=0.34.

3.3.Positioning error caused by the surface irregularities of T-shaped steel

Φ for flatness error,O1O4distance can be regarded as the positioning error as shown in Figure 6(b), leg thickness tolerance of 工-shaped steel is 0.012t(t=16.5). Φ =16.5 × 0.012=0.198.

(5)

(6)

3.4.Positioning the total error

(7)

(8)

Since theydirection welder servo system can automatically compensate, soxdirection is determined weld neutral for welding error sensitive direction, therefore we only need to calculate thexdirection, and take the various parameters into the equation[3].

With the outer edge positioning :

With the inner edge positioning:

Analysis of the calculation results, so the error used outer edge positioning is lager than that of the inner positioning[4-5].

Figure 6. The calculation diagram adopted cross outer edge and inner edge positioning

4.Conclusion

From the calculation process using the above two kinds of location methods can be seen:

1) Angle deviation of T-shaped steel in one direction greatest impact on the quality of welding, so fixed positioner of T-shaped steel should be used the adjustable device, so as to eliminate the influence of the angle error.

2) Locating surface is located inside the V slot, because of the neutral of V slot, manufacturing error of the welding equipment effect only the vertical direction, the wire feeding device can automatically compensate the positioning error in the vertical direction,thus positioning error caused by the device manufacturing can be regarded as 0.

3) The surface irregularities of T-shaped steel for the welding precision also has certain influence, locating surface is closer to the welding point, the error will be decreased in proportion. Therefore, reducing the size of welding device is for improving the precision of welding favorable. But if the special welding device size is too small, it will reduce the overall stability, so it is necessary to add auxiliary support, thereby increasing the contact stiffness.

The calculation results as a guide, designed welding device as shown in Figure 7, the welding positioner is used to fix the relative position of T steel and H steel, in order to ensure the two sections on both sides, on each side of the beam mounting gasket, as adjustment device. In order to reduce the volume of the positioning device, making the positioning surface as close to the welding point, the driving wheel and driving guide rail set outside the welding positioner, the electric welding machine and wire scroll and an hourglass are fixed on the mobile bearing, wire scroll and hourglass are connected with positioning device using a flexible hose connection, since only welded longitudinal displacement effect, will not bring additional error[6]. After reducing the volume of the positioning device, the floating support mechanism is designed to improve the rigidity of the welding positioning device, the lower edge of T-slot for the support, the pressure reliable and accurate positioning during the welding carriage movement process. At present, the device has been put into practical production.

Figure 7. The device structure of special welding

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2014-02-15.

10.3969/j.issn.1001-3881.2014.12.021

*Project supported by the Henan Provincial to Youth Backbone Teachers in Colleges and Universities: Research on Crane U-shaped Girder Integral Molding Process(No.2012GGJS-206)

? Jing-yun ZHAO, Associate professor. E-mail: hncad@163.com