Corrosion resistant oil well pipeOil Wells and gas Wells steel pipes include the drill pipe for mining, well wall protection pipeinserted inside the well to prevent formation collapse and pipeline system hanged inside the wallprotection tube for production.Based on security considerations, oil well pipe generally adopts seamless steel pipe.As a result of the oil well and gas well mining depth deepening year by year, such high strengthoil well pipes as N80 (yield strength 551 MPa grade) and P110 (yield strength 758 MPa) aredeveloped, these pipes have reached the American petroleum institute standards.However, the sulfide stress cracking accident happened in the 50s in Canada, so sulfide corrosiveenvironment sulfide stress cracking of high strength steel aroused people's concern.Sulfide stress cracking of low alloy steel is a kind of form of hydrogen embrittlement, theproduction fluid with the system of hydrogen sulfide inhibits corrosion reaction in the process ofhydrogen produced by dissipation, to invade the significantly increased the amount of hydrogen insteel. The higher the strength of steel, the greater the sensitivity of sulfide stress cracking, so goodto sulfide stress cracking resistance of high strength steel for development.The sulfide stress cracking resistance of steel is associated with the microstructure of steel.From martensite phase organization view shows the following measures is effective: adding Nband quenching tempering heat treatment can form fine grain structure; Reduce the intergranularsegregation elements such as P and Mn can prevent the grain boundary cracks; Increasingtempering temperature can reduce the internal strain, etc.Since the 60s have developed resistance to sulfide stress cracking of low alloy oil well pipe, andhas made steady development.In the deep well, due to the high bottom hole temperature (5000m class well, downholetemperature about 250 e), so the corrosion environment is very serious.In oil Wells in severe corrosion environment, usually to inject steel rust preventer protection, butno matter technically, or from an economic point of view, anticorrosive agent application is verydifficult, therefore developed suitable for all kinds of corrosive environment, without injectingantifushiji the corrosion resistance of alloy steel.From the perspective of corrosion resistance, corrosion resistant alloy steel can be roughly dividedinto system of martensite stainless steel, duplex stainless steel and austenite system high Ni alloythree kinds. The CO2 corrosion environment is often referred to as low sulfur corrosionenvironment. CO2 and H2S production fluid with together, but can form weak acid after CO2dissolved in water, can be used as consumption due to steel corrosion reaction of the source of H +ions, so compared with the same acid aqueous solution pH, the corrosion rate of carbon steel. Toreduce under the environment of CO2 corrosion rate, effective solution is to add Cr, now good tounder the environment of CO2 corrosion resistance and economy of 13 Cr steel (AISI420) demandincreased rapidly.However, because of 13 Cr steel under the temperature of more than 150e, corrosion speed willincrease, and the traces of H2S environment with sulfide stress cracking sensitivity, thus developeda new type of 13 Cr steel, namely by lowering the content of C, inhibition of Cr carbideprecipitation, ensuring effective amount of Cr, which can improve the application of the criticaltemperature in CO2 environment. In addition, add the Mo can make in the trace H2S environmentpassivity oxide film stability, inhibition of hydrogen in the steel. Especially under the environmentof high temperature, duplex stainless steel containing 22% ~ 25% Cr can be used.

In oil Wells and gas Wells with plenty of H2S, can use the austenite high Ni alloy with goodcorrosion resistance.Its critical temperature and corrosion resistant alloy elements of the content of Mo and W,depending on the use environment, has developed a Mo and W content different alloy series.

Corrosion resistance pipeline tubeOil and gas sea bottom and land transport steel pipe are called pipeline tube.Conveying and flow pipe exposed to corrosive environment generally use thick wall seamlesssteel pipe; While long distance conveying main pipes general use large diameter welded steel pipe.Due to the stress of the pipeline tube is generally lower than that of the oil well pipe, so on thecondition of low strength steel and fluid containing H2S, in addition to sulfide stress crackinghappens, still exists the problem of hydrogen induced cracking.Hydrogen induced cracking is due to the rolling of thick wall center segregation and inclusions inthe hardening of the tissue, thus taking the measures of desulfurization and decalcificationtreatment to control inclusions morphology and reduce the C, P, Mn to reduce the segregation.In the sea bottom oilfield development, from the perspective of lower development costs,underwater finishing well has a tendency to increase, from wellheads to equipped withdehydration, desulfurization processing equipment platform of the flow in the pipe, it is necessaryto take measures to prevent the production of fluid and the corrosion of the water.Ever using carbon steel for this part, and rust preventer is adopted to improve the corrosionresistance, but due to the seabed finishing well with rust preventive treatment cost is high, theenvironmental pollution problems exist, so use limited. Therefore, duplex stainless steel as thematerial has good corrosion resistance and can be used as a kind of welding material has arousedpeople's concern.Composed of ferrite and austenite phase not only high strength, duplex stainless steel and welding,is a kind of cheaper than system of austenite stainless steel steel, and can obtain the same as thebasic system of austenite stainless steel corrosion resistance, so it has the advantages to be suitablefor the pipeline tube.Initial conduit tube is good weldability 22 Cr system duplex stainless steel. Entering the 90sgradually developed super duplex stainless steel containing a lot of Mo, W and N .In recent years, due to the cathodic corrosion protection and coating technology getting improved,so although the water resistance of markov system new 13 Cr steel with good weldability is worsethan duplex stainless steel, under the condition of low CO2 + H2S also has good corrosionresistance, and can greatly reduce the cost of materials.After the new 13 Cr steel reducing C content can prevent the following two kinds of crack: one isthe crack because of the welding heat affected zone of martensite phase hardening; Another kind isthe crack caused by the dissolved hydrogen in the welded metal.Super duplex stainless steel and new 13 Cr steel as newly developed material, its join to thepipeline tube, no matter for seamless steel pipe and welded steel pipe, is surely worthy expectingto improve the corrosion resistance.