Microstructures And Properties Of High-strength 30CrNi3MoV Steel Used For Oil Fracturing Pump

At present, the 30CrNi3 MoV steel is widely used in petroleum industry, which is commonly used to manufacture some important parts. such as fracturing pump and turbine, however oil exploitation become more difficult, and the environment of exploitation is becoming worse, so the mechanical performance of oil-machine steel shoud be better. In this peper, we first compaer the performance of non-electroslag-remelting steel and electroslag remelting steel with diffierent process, and improve their mechanical performance two normalizing +tempering process, we try to achieve the purpose that non-electroslag-remelting steel can instead of electroslag remelting steel, and reduce production cost and the pollution to the environment; and research the influence of multielemental alloying to the microstructures and properties of the electroslag 30CrNi3 MoV steel, study the feature of electromical corrosion of the electroslag 30CrNi3 MoV steel which is in different simulate service conditions using polarization curve and electrochemical impedance test, analysis the microstructures and rust layers of the electroslag 30CrNi3 MoV steel with metalloscope and scanning electron microscope. Major conclusions are as follows:Electroslag remelting had little effects on the chemical component of tested steel. The contents of sulfur and phosphorus in non-electroslag-remelting steel and electroslag remelting steel were both very low. Electroslag remelting had little effects on the impurities of 30CrNi3 MoV steel, there were only little(one class)cyclic oxide inclusion existed in steel, without any other kinds of inclusion. We adopted number of times of normalizing to eliminate the inhomogeneities of microstructures and grains after forged. The tempering microstructures of non-electroslag-remelting steel and electroslag remelting steel were both tempered sorbite, which were small. The lengthways and transverse grains of electroslag remelting steel were a certain mixed crystal. The strength of non-electroslag-remelting steel was a little more than that of electroslag remelting steel, the ratio of lateral mechanical properties and vertical mechanical properties was both above 95%.The content of manganese increased from 0.66% to 1.05%, which had no effect on the grain size and conditioning microstructures of electroslag remelting steel, manganese reduced the size of martensite beams, thined quenching microstructures. The increasing content of manganese had little effect on the extension, yield strength, elongation, percentage of area reduction and hardness of tested steel, but witch could significantly reduce ballostic work by almost 40%. The content of silicon increased from 0.26% to 0.7%, which had no effect on the grain size, the increasing content of silicon reduced the quantites of carbide in conditioning microstructures, increased the quantities of lathed martensites in quenching microstructures, reduced the quantites of martensite beams and acicular martensite; the strength of extension, yield strength and hardness of tested steel respectively increased by 15.9%, 13%, 12% with the content of silicon increasing.In 5%HCl solution, the whole corrosion process was controled by anodic reaction, the corrosion resistance and the corrosion current density Icorr of electroslag remelting steel both increased with the content of silicon increasing and reduced with the content of manganese increasing. In 10%HCl, 15%HCl, 20%HCl solution, the variation trend of anodic reaction constant ?a, corrosion current density Icorr, rust layers resistance Rr and polarization resistance Rs was same as those in 5%HCl solution. The corrosion resistance of the three kinds steel reduced, the anodic reaction constant ?a and corrosion current density Icorr increased with the concentration of HCl solution increasing, the resistance of solution reduced, the thickness of rust layers increased, when strength of solution reached 15%, the thickness of rusty scale reached maximum. When the content of manganese increased, the weight loss increased, the weightlessness of mutations occurred anhead of time; when the content of silicon increased, the weight loss reduced, the weightlessness of mutagenesis time delayed.