Feasibility Study On Utrasonic Rolling Process For Steel Surface Protection Of Gathering Pipeline

In the process of crude oil production,the common surface problems such as corrosion,scaling and wax deposition in gathering pipelines have been a long-term problem for the world's petroleum industry.However,the newly developed ultrasonic surface rolling process(USRP)technology provides a new option to solve the problem of pipeline steel surface.In order to test whether the newly developed ultrasonic surface rolling technology has the feasibility of building good corrosion resistance,wax resistance and scale resistance on the surface of pipeline steel.A3 carbon steel and 316L stainless steel were selected as the research objects.The effects of this surface technology on the surface integrity,corrosion resistance,scale inhibition behavior and wax prevention characteristics of the two types of pipeline steel were investigated by means of surface integrity analysis,weightless corrosion,electrochemical testing,scale inhibition and wax prevention characterization and mechanism.It has proved the direction and application possibility for improving the corrosion resistance,scale inhibition and wax resistance of A3 carbon steel and 316L stainless steel.The results show:(1)After using USRP technology,the plastic deformation layer with thickness of about 50?55?m was successfully obtained on the surface of A3 carbon steel and 316L stainless steel.XRD showed that the surface grains of the processed samples were nanocrystalline.In addition,the surface integrity analysis shows that the surface integrity of A3 carbon steel and 316L stainless steel has been improved to a certain extent after being processed by USRP.Among them,Compared with A3 carbon steel,the microhardness of USRP-A3 sample is increased by 60%,the surface roughness is reduced by 77.44%,and the residual compressive stress of-463 MPa is introduced.However,the microhardness of USRP-316L sample is 50%higher than that of its substrate,the surface roughness is 96.85%lower,and-347 MPa residual compressive stress is introduced.(2)The results of weight-loss corrosion test and electrochemical test show that there are obvious differences between the corrosion resistance of A3 carbon steel and316L stainless steel by USRP.USRP can make 316L stainless steel surface more easily to form compact,uniform and complete passivation film,enhance the barrier ability to Cl~-,and reduce the self corrosion current density by an order of magnitude compared with the base material,so the corrosion resistance of USRP-316Lsample is significantly improved.However,for the active metal A3 carbon steel,USRP processing results in the refinement of surface grains and the enhancement of surface atomic activity,which results in the acceleration of metal dissolution rate,the increase of self corrosion current density by an order of magnitude compared with the substrate,and the corrosion resistance is greatly reduced.(3)Compared with 316L stainless steel substrate,the surface energy of USRP-316L sample is reduced by 27.43%,the average scale is reduced by 73.5%,and the wax prevention rate is as high as 63.24%.However,although the roughness of the USRP-A3sample is significantly reduced after the USRP treatment,due to the increase of dislocations,the surface atomic activity is enhanced and the surface energy is increased,resulting in an increase in its average scale and wax prevention rate.Preliminary research on the scale and wax prevention mechanism shows that the lower surface energy is the main factor to improve the material's scale and wax prevention performance.Secondly,the smooth surface and good corrosion resistance can make the surface of the material less susceptible to corrosion by the corrosive medium,and can maintain relatively good surface integrity,making it difficult for dirt and wax crystals to adhere.(4)The use of USRP technology can protect passive metals(such as 316L stainless steel),and its corrosion resistance,scale inhibition,and wax resistance are significantly improved compared to its substrate.Therefore,it is feasible to apply USRP technology to the protection of gathering pipelines.However,for active metals(such as A3 carbon steel),the USRP technology has not been able to directly provide better protection for this type of metal,and further research and discussion on the USRP process are needed.