ELECTRICAL CONTACT UNIT FOR HEAT TREATMENT AND STRETCH STRAIGHTENING OF PIPES, RODS AND SHAPED SECTIONS Russian patent published in 2012 - IPC C21D1/42 C21D9/08 

FIELD: metallurgy.

SUBSTANCE: unit for electric contact heating contains a transformer, a frame with longitudinal guides, current-carrying contacts mounted on the frame, movable contacts mounted on the support of longitudinal movement, a hydraulic cylinder for movement of the movable contacts and a controlled hydraulic drive. Between the support of the moving contacts and a hydraulic cylinder a pneumatic plunger-type piston is mounted coaxially with the hydraulic cylinder on the platform. The pneumatic cylinder plunger is rigidly connected to the piston rod of the hydraulic cylinder and has a length L_H of stroke not less than the value of thermal elongation of the heated workpieces, while the length L_H of stroke is limited by controlled stops, fixed on a platform of the hydraulic cylinder, and is determined by the expression: where is a relative force of the axial tension of the workpieces before heating at a temperature of t₀; is a relative force of the axial tension of the workpieces at the end of heating to a specified temperature t_K; F is cross-sectional area of the pneumatic cylinder working cavity, P₀ is force of the axial tension of the workpieces before heating, P_k is force of the axial tension of the workpieces the end of heating; Δl=l₀α(t_K-t₀) is lengthening of the workpieces when heated to t_K; α is a coefficient of linear thermal expansion of metal of the workpieces; l₀ is the length of the workpieces heated part; η=p_k/p_a; p_a is the atmospheric pressure, p_k is pressure of air or gas in the pneumatic cylinder working cavity with its length L_H.

EFFECT: expansion of process functionality of electric contact heating units for combining operations of heat treatment and stretch straightening that guarantees increased operational characteristics of the product.

3 cl, 4 dwg