A rare-earth-containing ultrahigh strength collapse-resistant
petroleum casing and a production method thereof belong to the technical fields of
ferrous metal smelting and
metal press working. The
petroleum casing comprises the following raw materials by weight percent: 90% of
blast furnace molten iron and 10% of high quality steel
scrap. The casing blank comprises the following chemical components by weight percent: 0.18-0.35% of C, 0.10-0.35% of Si, 0.55-1.10% of Mn, less than or equal to 0.025% of P, less than or equal to 0.020% of S, 0.60-1.10% of Cr, 0.15-0.50% of Mo, 0.01-0.03% of Al, 0.0005-0.0100% of RE ( RE is the mixed
rare earth metals of Ce and La and the weight percents of Ce and La are 67% and 33% respectively), less than 0.10% of Cu, less than 0.10% of Ni and the balance of Fe and trace elements. The process flow of the production method is as follows: pretreating molten iron,
smelting in a top-bottom blowing converter, refining in a
ladle furnace (LF), performing VD vacuum treatment, performing
continuous casting of round billets, performing
flame cutting, heating the casing blanks, boring, performing
continuous rolling, performing
sizing and
diameter reducing, cooling, performing saw
cutting, performing heat treatment, straightening, performing flaw inspection and lathing screw threads. The mechanical properties of the
petroleum casing are as follows: the strength is no less than 140000PSI, the
residual stress is no more than 80MPa, the
impact power is no less than 80J and the grain size is no less than the grade 8. The product is characterized in that the
residual stress is low, the content of harmful elements is low, the
impact toughness is high, the grains are small, and the product resists
extrusion and is difficult to damage.