Nodular cast iron foundation pile pipe and a method for preparing same

Abstract

The present invention provides a nodular cast iron foundation pile pipe and a method for preparing same, including following steps: (1) preparation before pipe casting: including molten iron preparation, spheroidization and coating spraying on an inner wall of a pipe mold; (2) pipe casting process: including centrifugal casting and pipe drawing; (3) annealing process; (4) finishing process. The present invention further provides the foundation pile pipe manufactured with the above-mentioned method wherein the flange and the foundation pile pipe are integrally cast or welded. In the present invention, the nodular cast iron is used as the material of the foundation pile pipe instead of Q345 steel used in the prior art. As a result, the overall strength is enhanced. The present invention possesses advantages such as corrosion resistance, long service life, low manufacturing cost, low labor intensity, short construction period and being suitable for mechanized construction.

1 . A method for preparing a nodular cast iron foundation pile pipe, the method comprises following steps:
 (1) preparation before pipe casting: including molten iron preparation, spheroidization and coating spraying on an inner wall of a pipe mold,   wherein the molten iron preparation includes heating the molten iron with medium frequency furnace to a temperature of 1460° C.-1500° C., and mass fractions of main chemical compositions in the molten iron are:   C: 2.9-3.2%, Si: 1.4-1.6%, Mn≦0.5%, Ti≦0.04%, P≦0.06%, S≦0.020%;   the spheroidization includes using any of pour-over method, wire feeding spheroidizing method or pure magnesium spheroidizing method to spherize the molten iron, mass fractions of main chemical compositions in the spheroidized molten iron are:   C: 3.0-3.3%, Si: 1.9-2.4%, Mn≦0.5%, P≦0.06%, S≦0.02%, Mg: 0.03-0.06%, Ti≦0.04%; and the spheroidized molten iron is set aside for later use after slag removal;   the coating spraying step includes spraying prepared coating on the inner wall of the pipe mold, and mounting a sand core at a socket part of the pipe mold for casting;   (2) pipe casting process: including centrifugal casting and pipe drawing, wherein the centrifugal casting includes adding a primary inoculant into the molten iron after the slag removal and temperature measurement, pouring the molten iron into a fan-shaped casting ladle, adding a secondary inoculant instantaneously into the molten iron at the time of casting, and carrying out water cooling treatment after the casting is finished; the pipe drawing includes drawing the pipe out of the pipe mold by pipe drawing pliers after the casting is finished, the pipe continuously rotates during and after the drawing process, and the pipe is conveyed to an annealing furnace with a rotary sling;   (3) annealing process: carrying out annealing treatment to the pipe at a temperature of 720° C.-750° C. for 30 minutes;   (4) finishing process: after annealing, carrying out shot blasting treatment to the coating and slag on a surface of the pipe, and carrying out finishing, hydrostatic test and preservative treatment.   
     
     
         2 . The nodular cast iron foundation pile pipe prepared by the method according to  claim 1 , wherein the foundation pile pipe includes a pipe body and a flange disposed at an end portion of the pipe body. 
     
     
         3 . The nodular cast iron foundation pile pipe according to  claim 2 , wherein a diameter of the pipe body is 600-2000 mm and a length thereof is 600-13000 mm, a diameter of the flange is 1000-2400 mm, and a thickness thereof is 15-50 mm. 
     
     
         4 . The nodular cast iron foundation pile pipe according to  claim 2 , wherein the flange and the pipe body are integrally cast or welded.