In [1], we examined the physical principles governing the effect of one-sided undulations of skelp on the quality of straight-seam electric-welded pipes. It is known that the quality of these pipes is affected most by tendency of the skelp to undergo corrugation during the forming of the pipe. In a number of cases, the corrugation can dismpt the lorming operation (in particular, it can lead to "biting" of the corrugations in closed passes), result in projection of the edges during their welding, and produce incomplete fusion. Other conditions being equal, the probability of the formation of corrugations on the edges of skelp increases under the lollowing conditions: a decrease in the thickness of the pipe wall, i.e., an increase in the ratio of the diameter of the pipe to the wall thickness: Dp/S; the use of skelp with crescent-shaped or wavy edges; the tbrmation of skelp from steel with a low elastic modulus; wide spacing of the stands of the mill; the use of passes not designed with allowance for the need to ensure longitudinal stability of the semifinished product, etc.Other conditions being equal, the longitudinal stability of the semifinished product (its tendency to undergo corrugation) depends mainly on the character of the change in the curvature of its longitudinal neutral axis (along the Z axis of the mill).This dependence can be represented in the form of a curve that connects the centers of gravity of the cross sections of the semifinished product [2]. The character of the curvature of the longitudinal neutral axis of the semifinished product depends in turn on the character of the change in the longitudinal bending moments of different signs that act on the product, as well as on deformation of its cross sections. It has been proposed that the main condition for the absence of corrugations on the semifinished product during continuous forming can be expressed by the following inequality: An increase in the distance between the stands increases the values of Mcz and Mtz. The increase in those values not only increases the above difference, but it also causes the section of the semifinished product in which the critical moment Mcr z has been reached to separate from the tool. Such separation also increases the probability of corrugation. Mcz -Mtz <-
Lately metal welding by high-frequency heating has gained wide recognition. This type of welding possesses a number of advantages over other electric welding technique. The advantages consist in a possibility of creation of high energy concentration in a thin layer of surface to be welded in a short time interval. Welded joints hereat are performed with slight flash and without gas liberation [ 1 1 . Welding by high-frequency heating has found a wide application for production of welded pipes because of its economical efficiency [2].The area of edge heating and flashing is schematically presented in Fig.1. In the section 1, the edges, converging at an angle z , are heated by the current flowing along them. The section II is specified by emergence of some electric contacts between the edges behind the convergent point. Here current is flowing between the edges, heating and blasting the coffer-dams of molten metal. This section is the light source of high brightness, whose spectrum is a linear one, but carries also a powerful background of plasma continuous radiation [3].
The methods and software of' the f'ast-running processes' investigation in van-Otis media (solids, liquids, gas. plasma) and technical objects were developed.The mathematical models of the objects under research were created in the conditions of exposure to the fields possessing different physical nature.The hardware and programming complex of' the i1m-phototelerecording and data processing combining the computer equipment, television-and film technique, was created. permitting to use the advantages of' every type of the technical systems ton the investigation of certain processes, objects and their characteristics. O-8194-2132-4/961$6.OO SPIE Vol. 2751 1159 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/23/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspxthe speed of' the image rendering by the tele-camera; it permits to observe the moving object in any moment of time, with any transfer characteristic in the pseudocolours.
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