EQUIPMENT-MANUFACTURING TECHNOLOGY

MECHANIZED REMOVAL OF WELDING FLASH AND THICKENING OF SEAM

IN THE WELDING OF ROD COLUMNS

A. P. Strel'nikov, P. I. Yastrebov, UDC 621.791.14.053.092:622.276.054.4(088.8) and G. I. Razvalov

At the Tatar Research Institute of Petroleum Machinery a technology was worked out and an experimental division set up for producing continuous rod columns (CRC) from rod or coiled rolled material by flash-butt welding with subsequent upsetting. ~en such a welding method is applied, a welding flash and a thickening of the welding seam form on the surface of the joint, and afterwards they have to be removed.

For the mechanical removal of the flash, when pipes with large diameter, 10-20 m long, are welded together, a device was worked out [i] which uses the effect of centrifugal force applied to an angle lever carrying a cutting tool and rotating around the machined object. Among the shortcomings of such a device is the lack of rigidity of the system consisting of the machined object and the cutting tool: this causes considerable radial wobble of the cutter because of the ridges and depressions on the machined surface, and it is also impossible to control the radial feed of the cutter (the radial feed being dependent on the rotational speed of the arbor with the lever). This device therefore cannot be used for removing welding flash- es and thickening of the seam on welded CRC.

Devices are known for removing the flash in friction welding [2]. The flash is removed during the welding process by a cutter mounted in the housing and obtaining the required cut- ting force from the rotating semiproduct through intermediate rollers. Since in this device the flash is removed in the plastic state during the welding process, the device cannot be used for removing the flash from CRC: the shifting of the continuous column entails the ap- plication of large axial and bending loads, and to avoid pulling the joint apart and shearing the welded ends of the CRC, the welded joint has to be cooled while it is gripped by the jaws of the welding machine.

In the device [3] the flash is first cut up into half-rings by additional cutters, and then it is completely cut away by the main tool. A similar method of removing the flash is also used in installations for welding comparatively short objects; the device for removing the flash is mounted directly on the welding machine, and the flash is removed immediately after the welding process is completed; at that time the metal is still plastic. This instal- lation therefore cannot be used either for machining ~RC.

At the Tatar Research Institute of Petroleum Machinery a device (see Fig. i) was designed and made; it is suitable for removing the flash from very long objects, and it is free of the shortcomings of the installations examined above. At the end face of the rotating spindle i there is the tool holder 4 with the cutting tool 5 which is tipped with a hard alloy tip 2142-0105 VK8 (GOST 9795--84). The CRC 8 is mounted in the slide block 7 and held by grip 6. The second support for the CRC is the split conical teflon collar 2 which rotates together with the spindle. By shifting the slide block the CRC is set in such a way that the roll formed by the flash lies in front of the tool whose position can be radially adjusted by screw 3 in accordance with the diameter of the machined welded joint. The flash and the thickening of the seam are removed from the CRC while the spindle rotates together with the tool and longitud- inal feed is provided with the slide block. The required surface smoothness of the welded joint is attained by grinding it with a grinding wheel until the transverse marks disappear. The rotational frequency of the spindle is 200-300 rpm, cutting depth is 5-6 mm (the flash and the thickening are removed in one cut), longitudinal feed is 0.05-0.1 mm/rev. After having machined 25-30 welded joints, the tool has to be ground. The efficiency of the suggested device was checked in machining more than 150 welded joints of rolled rods with diameters of 19 and 22 mm and made of steels 40 and 20N2M.

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 12, pp. 20-21, December, 1986.

614 0009-2355/86/1112-0614512.50 �9 1987 Plenum Publishing Corporation

1 2 . . - ~ 3 4 5 67 w \ \ /

Fig. I. Device for removing weld- ing flash and thickening of the seam from long objects.

The suggested device may also be used for removing the outside flash from long tubes with small diameter in the production of spiral tubes for once-through steam generator installa- tions requiring densely packed coils.

LITERATURE CITED

1. Inventor's Certificate 446376, USSR, MKI B 32 k 19/00; B 23 k 31/06. Device for Removing the External Flash in Friction Welding.

2. Inventor's Certificate No. 489609. USSR, MKI B 23 k 19/00. Device for Removing the Flash in Friction Welding.

3. Inventor's Certificate No. 557891, USSR, MKI B 23 k ll/04; B 23 k 19/00; B 23 D 35/00. Device for Removing the External Flash.

KINETICS OF THE CALCINATION PROCESS OF SHELL MOLDS IN FLUIDIZED BED

E. N. Prozorov, N. N. Varygin, UDC 621.744.3:621.785.6.062:66.096.5 L. K. Gordienko, and M. F. Maslovskii

The calcination of ceramic shell molds determines on the whole the duration of the tech- nological process of investment casting, and also the quality of the obtained castings [i].

In large-batch and mass production calcination is effected in machines models 675, 675-A, and 41-28. Such machines cannot be used to advantage in departments and casting sections with small capacity (up to 500 tons of serviceable castings per year) because of the considerable size of the machines and theirlarge power requirement. In production shops with small capacity shell forms are therefore calcined in continuous or compartment-type gas or electric furnaces in a layer of bearing disperse filler or without it. Such a process lasts 3 to 10 h in depend- ence on the calcination method.

Calcination of the molds in a fluidized bed of disperse heat carrier makes it possible to shorten the duration of the process considerably and to eliminate scrap in production caused by nonuniform heating of the shells throughout their bulk [2-4].

For the calculation of the specified capacity of calcination equipment it is necessary to know the time of heat treatment of shell molds which depends on the hydrodynamic and tempera- ture regimes of the process. The authors of [2, 3] studied the heat exchange between the flu- idized bed and the surface of the shell molds in the calcination process. However, we estab- lished that the factor limiting theduration of the process is the evaporation of the residues of the pattern compound from the porous ceramic shell, i.e., the process of mass transfer. It was pointed out in [5] that heat exchange plays but a secondary role.

The kinetics of calcination was investigated on an experimental installation (Fig. i) containing the cylindrical apparatus 3 of 250-mm diameter with a fluidized bed of quartz sand with equivalent particle diameter 0.25 mm, the incollapsible gas distributing grid 1 with free

1986. Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 12, pp. 21-22, December,

0009-2355/86/ii12-0615512.50 �9 1987 Plenum Publishing Corporation 615