The sucker rods use medium frequency induction heating power for medium frequency induction penetration heating and normalizing heat treatment

The sucker rod is a key equipment part for oil extraction. Its material is made of special steel YG42D. Its chemical composition (mass fraction, %) is: 0.43C, 1.00Cr, 0.19Mo, 0.80Mn, 0.25Si, 0.028S, 0.03P. During work, the sucker rod reciprocates up and down in the oil pipe, bears asymmetric cyclic loads, and is immersed in the produced crude oil liquid. It is corroded by the medium H2S, CO2 and salt water in the liquid. The failure of the sucker rod is mostly due to fatigue fracture. , under corrosive conditions, they are mostly weight loss corrosion, corrosion fatigue and sulfide stress damage failure. The traditional heat treatment process of the pumping rod adopts electric furnace heating, normalizing and high-temperature tempering processes. During production, it was found that workpieces using the traditional normalizing process are prone to oxidation and decarburization defects, which reduces the fatigue life of the sucker rod, increases the machining allowance, and the original process cycle is long and energy consumption is high. From the aspects of improving workpiece product quality, improving production efficiency, and reducing costs, it is required to improve the original heat treatment process of the sucker rod. To this end, after production testing and verification, a new process for induction penetration heating and normalizing of the sucker rod using medium-frequency induction heating power was proposed, and good results were achieved.

The sucker rod was subjected to a comparative test between the traditional process and the medium-frequency induction penetrating heating thermal normalizing process. The purpose of normalizing the workpiece is to improve the defective grains of the structure produced during sucker rod rolling and upsetting processing, and improve its mechanical properties; the function of high-temperature tempering is to eliminate the internal stress structure produced during normalizing. Medium frequency induction penetration heating normalizing process parameters: heating temperature is 890°C, workpiece movement is 40mm/s, voltage is 750V, current is 190-210A, power is 120-140kW, power factor is 0.9, inductor size is 80mm in diameter x1200mm. After many comparisons, we can see that after the pumping rod is normalized by medium-frequency induction penetration heating, its mechanical properties are significantly better than those treated by conventional processes.

Analysis suggests that the superior performance of the sucker rod after medium-frequency induction penetration heating and normalizing is the result of tissue refinement. As we all know, the refinement of the workpiece structure has unique advantages. On the one hand, it can improve the strength and toughness of the sucker rod; on the other hand, grain refinement can significantly improve the fatigue strength of the workpiece. After the sucker rod is normalized by medium-frequency induction penetration heating, the grain size is refined to 11-12 levels, and its structure is fine-grained ferrite evenly distributed on pearlite; while after normalizing in the electric furnace, the grain size is clear, only It is grade 6-7, and the structure is composed of relatively coarse massive ferrite and pearlite. On the other hand, the depth of the decarburization layer on the surface of the workpiece heated by the electric furnace is 0.20-0.25mm, while the depth of the decarburization layer of the workpiece heated by the medium frequency induction penetrating heating is less than 0.05mm. Therefore, the mechanical properties of the sucker rod after normalizing by medium frequency induction penetrating heating It is obviously better than the traditional electric furnace normalizing process.

After using improved medium frequency induction penetration heating and normalizing, the energy consumption in sucker rod production has been greatly reduced, and the production cost has been reduced. It has been calculated that the use of the new process can save 31% of electricity. A certain factory can save about 600,000 kW of electricity a year, which is economical. At the same time, the equipment cost and maintenance cost of the new process are lower than that of a resistance heating furnace, so the medium frequency heating power supply has obvious advantages. The prospects for promotion and application are promising.

Today, the editor briefly introduces to you the oxidation and deoxidation defects of the sucker rod, and briefly talks about the new medium-frequency induction penetration heating and normalizing process. I hope you can apply what you have learned to production and produce products that meet the requirements. , high quality sucker rod.