CN101440461A - Casinghead gas corrosion resistant pumping rod steel and manufacturing method thereof - Google Patents

Abstract

The invention provides steel for a pumping rod resisting casinghead gas corrosion and a manufacture method thereof. The steel comprises the following chemical compositions by mass percentage: 0.05 to 0.25 percent of carbon, 0.50 to 2.00 percent of silicon, 1.10 to 2.50 percent of manganese, 0.02 to 0.50 percent of molybdenum, 0.02 to 0.50 percent of nickel, 0.50 to 1.50 percent of chromium, 0.01 to 0.10 percent of vanadium, 0.005 to 0.050 percent of aluminum, 0.02 to 0.10 percent of niobium, 0.05 to 0.50 percent of copper, 0.01 to 0.10 percent of titanium, less than or equal to 0.015 percent of sulphur, less than or equal to 0.020 percent of phosphorus, and the balance being ferrum. The method is to manufacture a pumping rod wire through a design of adding the niobium and other trace alloy elements and corresponding compositions into steel, and controlled rolling and controlled cooling organization control technology. The pumping rod manufactured by the wire has excellent oilwell medium corrosion resistance, proper strength, excellent plastic tenacity and excellent welding performance, thereby improving the service life and reliability of the pumping rod, and improving the whole stability of pumping equipment, and further solving the problem that the prior pumping rod has repeated stress failure caused by endurance of complex casinghead gas corrosion.

Description

A kind of oil well gas corrosion-resistant sucker rod steel and its manufacturing method

technical field

The invention relates to compositional design and manufacturing method of structural steel in the metallurgical industry, in particular to an oil well gas corrosion-resistant sucker rod steel and its manufacturing technology.

Background technique

Mechanical oil recovery is the main means of oilfield development, and the rod pumping system plays an important role in mechanical oil recovery. The sucker rod is an important part of rod pumping equipment. Its function is to transmit the power of the pumping unit to the downhole pump and extract oil through the oil well pipe.

Sucker rods are generally made of steel wire rods, which can be divided into D-grade rods and H-grade rods according to their strength levels, of which the latter has higher strength. The steel types used to manufacture D-grade rods include 35Mn2, 35CrMo, 42CrMo steel, etc. The D-grade sucker rods recommended by the American Petroleum Institute are: 1536 and 4142 (equivalent to 35Mn2 and 42CrMo steel respectively). 12Mn2SiCr, 16Mn2SiCr, 20Cr2MoNi steel and so on are mainly used in the manufacture of H-class rods. Although H-grade sucker rods have higher strength, their service life is not necessarily higher than that of D-grade rods. The reason is that although the strength and wear resistance of the sucker rod increase as the strength of the steel increases, the increase in the strength of the sucker rod is often accompanied by a decrease in toughness as a price.

At present, in the process of oil and gas development, the corrosion of sucker rods by CO ₂ +H ₂ S+CL ^- and other gases and media has become the main problem of oil well gas corrosion resistance. It not only caused huge economic losses to oil fields, but also And it often brings some disastrous consequences, such as casualties, shutdown, production shutdown and environmental pollution. At present, China's Tarim, Changqing, Sichuan, Huabei, Jianghan and other oilfields all have serious CO2 corrosion, while Sichuan, Changqing and other oilfields also have more serious CO ₂ +H ₂ S+CL ^- comprehensive corrosion. Research literature at home and abroad shows that the use of stainless steel containing high Cr, Ni, Mo and other alloying elements is considered to be an ideal material for CO ₂ +H ₂ S+CL ^- resistance, but it contains a large amount of Cr, Ni, Mo and other expensive Strategic elements greatly increase the manufacturing cost of oil field extraction equipment, which is generally not accepted by the oil extraction industry. Especially for my country's oil mining industry, most of the oil fields are lean ore and low permeability oil fields, and the one-time investment of expensive oil field mining equipment is too large and the economy is poor. At present, due to the increasing difficulty of exploration and development, the exploration and development environment is getting worse and worse, and users have higher and higher requirements for oil well sucker rods.

Chinese patent application No. 200410079237.X is a corrosion-resistant sucker rod and its manufacturing method, and its carbon content is 0.40 to 0.45%. Chinese patent application No. 200410062593.0 is a sucker rod steel and a process for manufacturing an ultra-high-strength sucker rod , its carbon content is 0.25-0.30%, which is unfavorable to the welding performance of the sucker rod; and the strength of Chinese patent application No. 90104471.7, 200410062593.0, and Japanese patent Zhao 60-238416 can no longer meet the requirements of high strength and toughness of the sucker rod; The patents No. 92102405.3, 96101923.9, and 01106092.1 are non-quenched and tempered steels, which contain high carbon and manganese contents, which are not good for toughness and welding performance; Chinese patent application No. 200410024409.3 is the only continuous sucker rod steel with relatively Excellent toughness, but it does not have corrosion resistance; the Cr content in Japanese patents Sho 60-238418 and Sho 61-295319 is 8.0-15.0%, which has certain corrosion resistance from the composition design, but its precious alloy composition is too high And the cost is generally not adopted by petroleum equipment factories.

Table 1

Patent Application No C (wt%) Si(wt%) Mn(wt%) Cr(wt%) Mo (wt%) Other elements (wt%) 200410062593.0 0.25～0.30 0.20～0.40 0.40～0.70 0.80～1.10 0.15～0.25 / 200410079237.X 0.40-0.45 0.15-0.35 0.65-1.10 0.80-1.10 0.15-0.25 P0.010-0.035S0.015-0.040Ni0.015-0.045 95111888.9 0.27～0.35 0.90～1.20 1.20～1.50 / / V: 0.10～0.20 90104471.7 0.36～0.44 0.31～0.40 1.20～1.80 / / Nb: 0.02～0.05 92102405.3 0.10～0.24 0.40～1.40 2.00～3.00 0.40～1.10 0.15～0.35 V: 0.05～0.20Ti: 0.01～0.03 96101923.9 0.08～0.20 0.50～1.00 1.60～2.10 0.80～1.20 / Ti0.04～0.10B0.0005～0.0030 01106092.1 0.26～0.35 0.80～1.05 1.30～1.50 / ≤0.04 Cr+Ni≤0.02Cu≤0.25V: 0.08～0.15Ti: 0.02～0.05

200410024409.3 0.18～0.23 0.15～0.30 0.40～0.60 1.80～2.00 0.17～0.25 Al: 0.02～0.05Cu≤0.30 Zhao 60-238416 0.25～0.35 0.20～0.40 0.40～0.60 0.80～1.20 0.30～0.50 Nb≥0.015 Zhao 60-238418 0.10～0.30 0.10～0.80 0.30～1.20 8.0～15.0 Al: 0.001～0.050 Zhao 61-295319 0.10～0.30 0.10～0.80 0.30～1.20 8.0～15.0 0.05～2.0 Al: 0.001～0.050

To sum up, the existing steel for sucker rods still has the following disadvantages: (1) General sucker rod steels generally do not meet the requirements of oil well gas corrosion resistance. Even though 200410079237.X has the characteristics of corrosion resistance, its welding Poor performance; (2) It has good oil well gas corrosion resistance in high-grade sucker rod steel. For example, the Cr content in Zhao 61-295319 is 8.0-15.0%, but its high alloy ratio cannot be determined by the petroleum equipment factory. Accepted; (3) The strength and plasticity matching of the existing sucker rod steel is not very ideal, especially the elongation of the tensile test is low (generally the tensile strength of the sucker rod is 740-900Mpa, and the elongation is 12- 19%, and the reduction of area is 50-70%; the strength level meets the requirements, but the plasticity index is poor); (4) the impact resistance of existing sucker rods is generally low (generally between 70-100J in Aku), It is easy to cause the tendency of fatigue fracture of the sucker rod under the complex stress conditions under the complex working environment.

Contents of the invention

The purpose of the present invention is to design a sucker rod steel resistant to oil well gas corrosion, that is, to manufacture sucker rod wire rods by adding trace alloy elements such as niobium and corresponding composition design into the steel, and by controlling rolling and cooling structure control technology. The sucker rod made of this wire has good oil well medium corrosion resistance, appropriate strength, excellent plasticity and toughness, and good welding performance, thereby improving the service life and reliability of the sucker rod and improving the overall stability of the pumping equipment , to further solve the problem of fatigue fracture of existing sucker rods due to complex oil well gas corrosion.

The technical scheme of the present invention is,

An oil well gas corrosion-resistant sucker rod steel, the mass percentage of its chemical composition is: carbon 0.05-0.25, silicon 0.50-2.00, manganese 1.10-2.50, molybdenum 0.02-0.50, nickel 0.02-0.50, chromium 0.50-1.50, vanadium 0.01 ～0.10, aluminum 0.005～0.050, niobium 0.02～0.10, copper 0.05～0.50, titanium 0.01～0.10, sulfur ≤0.015, phosphorus ≤0.020, and the balance is iron and unavoidable impurities.

The role of its main chemical elements in steel is as follows:

Carbon: It is generally believed that the carbon content of 0.08-0.40% has no obvious effect on the hydrogen sulfide corrosion cracking sensitivity of steel. Carbon is the main element to improve the strength of steel. To ensure a certain strength, a certain carbon content is necessary, but carbon element is not good for plasticity, and at the same time, a carbon content greater than 0.30% is not good for welding performance. Controlling the C content of 0.05-0.25% can ensure sufficient strength, and at the same time make the steel have good toughness and weldability.

Manganese: As a solid solution strengthening element, it can also reduce the austenite-ferrite transformation temperature and effectively improve the hardenability of steel. However, manganese has the disadvantage of promoting the growth of austenitic grains in steel and is not conducive to welding performance. The content of manganese controlled at 1.10-2.50% can play a good role in the steel of the present invention.

Silicon: It is the main alloying element in steel, but there is no clear conclusion on the susceptibility of silicon to hydrogen sulfide corrosion cracking in steel. Silicon can significantly improve the strength of ferrite, change the shape, quantity and size of carbide precipitation during tempering, improve the tempering stability of steel, and indirectly promote precipitation strengthening. Silicon has adverse effects on the plasticity and toughness of steel to a certain extent, but silicon can promote the redistribution of carbon elements during the phase transformation process, improve the stability of retained austenite, and thus improve toughness. Controlling the silicon content of 0.50-2.00% can achieve solid solution strengthening and improve toughness at the same time.

Molybdenum: In low-alloy steel, it can improve the resistance to sulfide cracking of the steel, and at the same time it can strongly delay the ferrite transformation and significantly improve the hardenability of the steel. It can reduce the temper brittleness of steel, improve the performance of heat treatment process, and improve the fatigue performance of steel. Molybdenum can reduce the activity of hydrogen in steel and greatly reduce the hydrogen absorption tendency of steel. It can strongly hinder the nucleation and growth of carbides and reduce the hydrogen storage traps in steel. Adding 0.02-0.50% molybdenum to the steel of the present invention is the most economical and effective content.

Chromium: It can significantly improve the resistance to sulfide cracking of steel and significantly improve the hardenability of steel. The combined use of chromium and Mn has a good effect. Because Cr reduces the carbon activity in steel, it is also a carbide forming element and improves the diffusion of carbon. Activation energy, so it can reduce the decarburization tendency of steel. It can change the electrode potential of steel and improve the corrosion resistance. 0.50-1.50% chromium is the most economical and effective content.

Copper: It can improve the stability of austenite, without increasing the hardness of martensite, but can form a copper-rich phase through precipitation strengthening to increase the secondary hardening hardness and improve corrosion resistance. Generally, the added and residual copper in the steel of the present invention is: 0.05-0.50%.

Nickel: It is harmful to the resistance to sulfide cracking of low alloy steel. The hydrogen evolution overpotential on nickel-containing steel is the lowest, and hydrogen ions are easy to discharge, thus strengthening the hydrogen evolution process and increasing the susceptibility of steel to sulfide cracking. However, it can inhibit Cu embrittlement during thermal processing, reduce the degree of solid solution of carbon in the matrix, reduce the cooling transition temperature, and promote the precipitation of Cr and Mo carbides. Adding 0.02-0.50% nickel in the present invention can achieve expected alloy effect.

Niobium: It can significantly improve the resistance to sulfide cracking of steel, significantly improve the hardenability of steel, and can form fine NbCN particles in steel types. When the billet is reheated, undissolved NbCN particles can prevent the growth of austenite grains; Nb It can significantly increase the recrystallization temperature of steel, so that steel can be subjected to non-recrystallization controlled rolling in a relatively high and large thermal deformation temperature range, promote the refinement of grains, and improve the strength and toughness of steel. 0.02-0.50% niobium can play the above role.

Titanium: The effect is similar to that of niobium, but it is a stronger carbonitride forming element, and the fine TiCN particles can effectively prevent the growth of austenite grains when the billet is reheated. 0.01-0.10% titanium has a beneficial effect on resistance to sulfide cracking.

Vanadium: It can produce strong dispersion and precipitation strengthening, improve the strength of steel, and has the effect of preventing austenite grain growth and increasing the recrystallization temperature of steel similar to Ti and Nb. Considering the matching of other elements, 0.01-0.10% vanadium is an ideal content.

Aluminum: belongs to grain refinement element. The combination of aluminum and the above elements can further refine the grain, increase the hardenability, and improve the strength and toughness. Aluminum significantly reduces the solubility of carbon in ferrite, slows down the diffusion of hydrogen, and makes the distribution of carbides more uniform, thereby improving the ability to resist sulfide damage. But too much aluminum will easily increase the chance of inclusions in the steel, so 0.005-0.050% aluminum is the suitable content of the steel of the present invention.

Sulfur, phosphorus: Sulfur is very harmful to hydrogen sulfide cracking resistance, because sulfide inclusions in steel can not only be the starting point of hydrogen-induced cracking, but also easily cause stress corrosion cracking along the sulfide inclusion boundary. Therefore, it is necessary to control sulfur below 0.015%. Phosphorus, which is also detrimental to hydrogen sulfide crack resistance, is an accelerator for hydrogen absorption. Phosphorus can block hydrogen atomization to synthesize molecules, thereby increasing the degree of hydrogen permeation and reducing the hydrogen sulfide crack resistance of steel, so phosphorus should be controlled below 0.020%.

At the same time, lead, antimony, and bismuth are impurity elements in steel, and their content should be reduced as much as possible if technical conditions permit.

In the present invention, carbon, manganese, silicon, chromium and molybdenum are the main elements, and one or more of niobium, vanadium, molybdenum, aluminum and titanium are used as trace alloy elements. Appropriate carbon content can ensure sufficient strength, and at the same time make the steel have good toughness and weldability. At the same time, the solid solution strengthening effect of silicon and manganese must be considered.

If it is necessary to limit the hardenability, consider reducing the carbon and manganese content and increase the silicon element to compensate for the loss of strength; if it is necessary to increase the hardenability and reduce the temper brittleness of the steel, increase the manganese content and reduce the silicon content, but consider the brittleness It will increase and toughness, and the stability of retained austenite will decrease; Cr can significantly improve the hardenability and corrosion resistance of steel, and at the same time it is more beneficial to strength and toughness, but considering the content and performance requirements of carbon, silicon and manganese It can be added between 0.50 and 1.50%; molybdenum and manganese are highly correlated and have a significant impact on hardenability. When controlling the upper limit of 1.10 to 2.50% of manganese, consider controlling the lower limit of 0.02 to 0.50% of molybdenum One or more of niobium, vanadium, molybdenum, aluminum and titanium are used as trace alloying elements. These trace alloying elements can form very strong carbonitrides. The fine carbonitride particles can effectively prevent the austenitic steel billet from reheating. The growth of solid grains can increase the recrystallization temperature of steel, so that steel can be rolled without recrystallization in a relatively high and large thermal deformation temperature range, which can promote the refinement of grains and improve the strength and toughness of steel; copper can Improve the stability of austenite, produce precipitation strengthening, and improve corrosion resistance. However, if copper is added to prevent copper embrittlement, nickel is generally added to prevent copper embrittlement, but nickel is unfavorable to corrosion resistance; sulfur and phosphorus are in steel. The impurity elements in the steel will significantly reduce the plasticity and toughness of the steel, and must be controlled below a certain content.

Oil well gas corrosion-resistant sucker rod steel manufacturing method of the present invention, it comprises the steps:

1) Electric arc furnace smelting, ladle refining, continuous casting pouring,

1.1 Smelting and tapping conditions: T≥1620℃; [P]≤0.010%, [C]≥0.05%;

1.2 Ladle refining, to ensure that [O]≤0.0025%, [H]≤0.00015%; all components enter the required range;

1.3 Cast continuous casting slab; tundish superheat ≤35℃;

2) rolled into lumber,

2.1 Heating in the heating furnace, the soaking temperature is 1150-1250°C, and the heating and holding time is >2 hours. Due to the action of fine NbCN particles in the steel, the austenite grain growth of the steel at high temperature is inhibited, so that the billet obtains a smaller initial grain size;

2.2 Controlled rolling, after the evenly heated slab comes out of the furnace, after descaling, it enters the rough rolling unit in the temperature range of 1050-1150°C; it enters multi-pass finish rolling between 900-980°C, Rolling in the recrystallization zone, the cooling speed of the wire rod is controlled during the rolling process, so that it is finished rolling in the temperature range of 780-850 °C, and enters the reducing and sizing unit for rolling in the temperature range of 780-850 °C; The heating temperature is 1070-1200°C, the holding time is 2 hours, and the furnace temperature is 1050-1180°C. Compared with the prior art, the soaking temperature of the present invention is increased by 50°C to implement controlled rolling.

2.3 Control cooling. After rolling to meet the specified wire diameter, the wire is slowly cooled on-line on the roller table. The cooling rate is 40-80°C/h, and the temperature drops below 500°C by air cooling to room temperature. A large number of fine proeutectoids are precipitated in the deformed austenite, and the rest of the austenite is transformed into bainite in the subsequent cooling.

Also, in step 2), the temperature of the billet out of the furnace is 1130-1230°C;

The temperature of the billet out of the blooming unit is controlled at 1030-970°C;

During the rough rolling process, on the one hand, the billet is uniformly deformed, and on the other hand, the cooling rate of the billet is controlled, so that the temperature of the billet leaving the blooming unit is controlled at 1030-970°C. Control the cooling rate of the steel billet before it enters the finishing rolling unit, and complete the recrystallization of the deformed austenite in the steel during this process.

In addition, the online slow cooling of the wire on the roller table can be delayed by using a covered heat preservation cover.

In the manufacturing process of the present invention,

(1) Controlled rolling and controlled cooling technology to control the hardenability of sucker rod wire

The sucker rod steel billet is rough-rolled in the temperature range of 1050-1150°C, and finished-rolled in the temperature range of 780-950°C, and the cooling speed of the steel is controlled during the rolling process so that the finish rolling is controlled within the temperature range of steel. unrecrystallized region.

(2) Strain-induced ferrite precipitation technology for controlling hardenability sucker rod

After the steel is rolled in the non-recrystallization zone, it is slowly cooled online on the roller table, and ferrite is precipitated in the high-strain austenite, and in the subsequent cooling process (air cooling), the supercooled austenite transforms into bainite body tissue.

(3) Control hardenability sucker rod microstructure refinement technology

Through the comprehensive application of the following technologies, the sucker rod wire with fine structure and excellent plasticity and toughness is obtained. During the reheating process of the steel billet at 1150-1250 °C, the tiny titanium and niobium carbonitrides inhibit the growth of austenite grains, so that the steel billets obtain smaller initial grains. The sucker rod steel billet undergoes dynamic recovery and recrystallization during thermal deformation at 1000-1100°C. After hot deformation static recrystallization is completed, due to the effect of titanium and niobium precipitates, the growth of recrystallization is inhibited. Due to the action of niobium and vanadium precipitates, the recrystallization of the billet during rolling at 780°C to 850°C is inhibited, and a large amount of deformation energy is accumulated in the deformed austenite, and a large amount of fine particles are precipitated in the range of cooling to 650°C to 750°C. Ferrite, the grains are greatly refined.

(4) Microstructure performance characteristics and process characteristics of sucker rod wire rod with controlled hardenability

The grain size of the hot-rolled controlled hardenability sucker rod wire produced by the above-mentioned technology is 9-11, and the structure is proeutectoid ferrite and bainite, and the bainite structure is composed of bainitic ferrite, Composed of martensite and retained austenite. The hardness of the hot-rolled wire rod is 210-290HB, has good plasticity and toughness, and does not need annealing for hot-rolling.

Beneficial effects of the present invention

1. The sucker rod steel for oil well medium corrosion resistance produced by the above-mentioned technology can obtain bainite structure in the complete austenitization at 900°C and cooling range of 30-300°C/min, and iron can be obtained at a lower cooling rate. Mixed structure of ferrite and bainite. If the cooling rate is higher than the mixed structure of martensite and bainite, the grain size of sucker rod wire with controlled hardenability is 8-11, and the structure is proeutectoid iron. Ferrite and bainite, in which the bainite structure is composed of bainitic ferrite, martensite and retained austenite. This structure is beneficial to the improvement of oil well gas corrosion cracking resistance.

2. Slowly cool after controlled rolling and cooling to obtain a mixed structure of bainite structure. The hardness of the hot-rolled wire rod is 210-290HB, which has good plasticity and toughness. The hot-rolled wire rod (wire rod) is directly uncoiled ( Exemption from conventional annealing) can be quenched and tempered on continuous induction heat treatment equipment.

3. High purity of steel: low level of inclusions (according to GB/T1056 detection can meet: A≤2, B≤2, C≤1, D≤1); gas content (oxygen≤15ppm, hydrogen≤1.5ppm).

4. The carbon equivalent of the invented steel is suitable, so it has good welding performance, and the mechanical properties of the weld seam of the sucker rod after flash welding are not lower than those of the original rod.

5. The sucker rod made of the steel of the present invention has the characteristics of low cost, easy operation, etc., especially excellent oil well gas corrosion resistance, and excellent comprehensive service life.

Description of drawings

Fig. 1 is the metallographic structure of the sucker rod steel of the present invention after hot rolling and slow cooling, and its metallographic structure is composed of mixed structures such as proeutectoid ferrite and bainite, wherein the bainite structure consists of bainitic ferrite body, martensite and retained austenite.

Detailed ways

Embodiments of the method for manufacturing oil well gas corrosion-resistant sucker rod steel of the present invention,

1. Electric arc furnace smelting, ladle refining, continuous casting pouring,

(1) Initial smelting of molten steel: Low P and S scrap steel, cut ends and high-quality pig iron are used as the furnace charge; low-carbon chromium, low-carbon manganese, ferromolybdenum, aluminum ingots, etc. should be prepared for the alloy; reducing agent: calcium carbide, carbon powder, aluminum powder ;Oxidation period: frequent slag removal of P, decarburization amount ≥ 0.30%; slagging conditions: T ≥ 1650 ℃; P ≤ 0.004%, Al: 0.5Kg/t; tapping conditions: T ≥ 1620 ℃; [P] ≤0.010%, [C]≥0.05%. Add appropriate amount of lime or synthetic slag in the later stage of tapping;

(2) Ladle refining: on the ladle refining furnace (capacity matched with the electric furnace), the molten steel is refined to remove harmful gases and inclusions in the steel, the ladle is seated, the temperature is measured and analyzed, and the argon pressure is adjusted according to the situation; Add Al to 0.05% for the initial deoxidation of LF, stir for ≥5 minutes, and adjust the chemical composition into internal control. When the molten steel temperature T≥1620℃, enter the vacuum position for degassing, and keep the vacuum at 0.5 Torr for ≥15 minutes; ensure [O]≤0.0025%, [H]≤0.00015%; all components enter the range of optimization requirements start bagging;

(3) Continuous casting pouring: The high-temperature molten steel in the ladle passes through the protective sleeve and pours into the tundish, and the superheat of the tundish is ≤35°C. The tundish is completely cleaned before use, and the inner surface is refractory coating without cracks; the molten steel in the tundish passes through the continuous casting crystallizer, and at a reasonable speed, a qualified cross-sectional size of 90×90mm ² to 360×360mm ² is cast. For continuous casting slabs, the casting speed is 0.90~2.10m/min according to different ingot sizes;

2. Wire rolling

1. Heating in the heating furnace, the soaking temperature is 1150-1250°C, the heating and holding time is >2 hours, the temperature of the billet is 1130-1230°C, and the temperature difference between the positive and negative surfaces is ≤30°C; the billet is heated to 1150-1250°C;

2. Rolling, after the evenly heated billet is out of the furnace, it is descaled under high pressure, and the inlet temperature of reducing and sizing rolling is 780-850 ℃. The steel billet is soaked and released from the furnace. After descaling, it enters the roughing rolling unit at a temperature range of 1050-1150°C. Controlled at 970～1030℃. Control the cooling rate of the steel billet before it enters the finishing rolling unit, and complete the recrystallization of the deformed austenite in the steel during this process.

3. Controlled cooling process: online slow cooling after rolling into wire rod, cooling rate is 40-80°C/h. The steel billet enters the multi-pass finishing rolling unit between 980 and 900°C, and is rolled in the austenite non-recrystallized area. Rolling, cooling to 650-750°C on the conveying line, and then entering the slow cooling zone for slow cooling, so that a large number of fine proeutectoids are precipitated in the deformed austenite, and the rest of the austenite is transformed into bainite in the subsequent cooling.

The billet is heated to 1150-1250°C. The billets are soaked and released from the furnace. After descaling, they enter the roughing rolling unit at a temperature range of 1050-1100°C. During the rough rolling process, on the one hand, the billets are uniformly deformed, and on the other hand, the cooling speed of the billets is controlled so that the temperature of the billets exiting the roughing rolling unit Controlled at 1030～1000℃.

The steel billet enters the multi-pass finishing rolling unit between 910 and 980°C, and is rolled in the austenite non-recrystallized area. Rolling, cooling to 660-750°C on the conveying line, and then entering the slow cooling zone for slow cooling.

The diameter of the sucker rod wire is Φ23mm, the hardness is 235HB, the grain size is 9 grades, and the structure is proeutectoid ferrite and bainite, and the bainite structure is composed of bainitic ferrite, martensite and residual Austenite composition, see Figure 1,

The chemical composition of table 2 embodiment steel bar, wt%

Example C mn Si Cr Al Mo Ni S Cu P Nb Ti Fe 1 0.08 1.18 1.98 0.70 0.015 0.50 0.08 0.006 0.12 0.008 0.03 0.02 margin 2 0.05 1.41 1.69 0.50 0.025 0.04 0.18 0.008 0.10 0.010 0.02 0.04 margin 3 0.13 1.65 1.01 1.50 0.035 0.15 0.25 0.002 0.20 0.006 0.04 0.10 margin 4 0.18 1.99 0.79 1.05 0.010 0.20 0.38 0.010 0.35 0.020 0.10 0.07 margin 5 0.25 2.50 0.50 0.58 0.005 0.25 0.50 0.004 0.50 0.006 0.06 0.06 margin 6 0.12 1.15 2.00 1.00 0.035 0.03 0.02 0.003 0.08 0.007 0.02 0.03 margin 7 0.14 1.10 1.89 1.01 0.050 0.02 0.08 0.015 0.09 0.020 0.05 0.01 margin

The mechanical property of table 3 embodiment steel bar

Example Rp0.2(Mpa) Rm(Mpa) A5(%) Z(%) Aku(J) 1 690 856 twenty three 70 140 2 704 848 25 74 138

3 725 879 twenty two 68 125 4 780 923 twenty three 68 107 5 757 916 twenty two 70 112 6 786 996 25 75 118 7 715 890 26 76 120

It can be concluded from Table 3 that the steel of the present invention has a good combination of strength and toughness, and the product can greatly improve plasticity and toughness while maintaining the strength without decreasing. In addition, the fine and uniform mixed microstructure (including retained austenite) can obtain good Fatigue life and its resistance to oil well gas corrosion.

Implement the wire rod (wire rod) steel that the present invention produces, make sucker rod through domestic certain sucker rod production plant and be applied to domestic certain large-scale oil field, each performance all meets service requirement, has better performance than common sucker rod The performance of resistance to oil well gas corrosion can better solve the problems that cannot be solved by ordinary sucker rods, and has a tendency to replace ordinary sucker rods, especially for corrosion wells and low permeability wells, which have very important practical significance.

Claims (5)

1. Casinghead gas corrosion resistant pumping rod steel, its chemical ingredients mass percent is:

Carbon 0.05～0.25,

Silicon 0.50～2.00,

Manganese 1.10～2.50,

Molybdenum 0.02～0.50,

Nickel 0.02～0.50,

Chromium 0.50～1.50,

Vanadium 0.01～0.10,

Aluminium 0.005～0.050,

Niobium 0.02～0.10,

Copper 0.05～0.50,

Titanium 0.01～0.10,

Sulphur≤0.015,

Phosphorus≤0.020,

Surplus is iron and inevitable impurity.

2. the manufacture method of Casinghead gas corrosion resistant pumping rod steel as claimed in claim 1, it comprises the steps:

1) electric arc furnace smelting, ladle refining, continuous casting,

1.1 smelt the tapping condition: T 〉=1620 ℃; [P]≤0.010%, [C] 〉=0.05%;

1.2 ladle refining guarantees [O]≤0.0025%, [H]≤0.00015%; All the components enters the scope of requirement;

Outpour continuously cast bloom 1.3 water, tundish superheating temperature≤35 ℃;

2) rolling becoming a useful person,

2.1 process furnace heating, 1150～1250 ℃ of soaking temperatures, heat tracing time 〉=2 hour;

2.2 controlled rolling after the steel billet of homogeneous heating is come out of the stove, after de-scaling, enters the roughing unit in 1050～1150 ℃ of temperature ranges; Between 900～980 ℃, enter the finish rolling of multi-pass, the district is rolling at the austenite non-recrystallization, the speed of cooling of control wire rod makes it go out finish rolling in 780～850 ℃ of temperature ranges in the operation of rolling, and it is rolling to enter the reducing sizing mill group in 780～850 ℃ of temperature ranges;

2.3 controlled chilling, be rolled into line up to specification footpath after, wire rod is online slow cooling on roller-way, 40～80 ℃/h of speed of cooling, temperature is reduced to and is adopted air cooling to room temperature below 500 ℃.

3. the manufacture method of Casinghead gas corrosion resistant pumping rod steel as claimed in claim 2 is characterized in that, 1130 ℃～1230 ℃ of steel billet tapping temperatures.

4. the manufacture method of Casinghead gas corrosion resistant pumping rod steel as claimed in claim 2 is characterized in that, steel billet goes out breaking down unit temperature and is controlled at 970 ℃～1030 ℃.

5. the manufacture method of Casinghead gas corrosion resistant pumping rod steel as claimed in claim 2 is characterized in that, wire rod online slow cooling on roller-way is adopted and added a cover the stay-warm case delayed quench.