CN109182896B - 175MPa movable elbow material and heat treatment process - Google Patents

Abstract

A175 MPa movable elbow material comprises the following elements in percentage by weight: 0.12 to 0.20 weight percent of C, 0.4 to 0.7 weight percent of Cr0, 1.4 to 2.0 weight percent of Nis, 0.6 to 1.2 weight percent of Mns, 0.55 to 0.8 weight percent of Mos, less than or equal to 0.25 weight percent of Si, less than or equal to 0.15 weight percent of (Nb + V + Ti), less than or equal to 0.2 weight percent of Cu, less than or equal to 0.015 weight percent of P, less than or equal to 0.010 weight percent of S, less than or equal to 0.010 weight percent of Sn, less than or equal to 0.005 weight percent of Sb, less than or equal to 0.005 weight percent of As, less than or equal to 2 ppm. The heat treatment process comprises normalizing, tempering, carburizing, quenching, tempering, and finally cooling and tempering. The invention can meet the construction requirement of large-scale fracturing operation under 175MPa pressure at most.

Description

175MPa movable elbow material and heat treatment process

Technical Field

The invention belongs to the field of material science, and particularly relates to a movable elbow material capable of being used under the pressure of 175MPa of oilfield fracturing construction operation pressure and a heat treatment processing technology thereof.

Background

Because of the factors such as special geological structures in China, the average value and the maximum value of the required fracturing construction operation pressure are far higher than the foreign level when oil and gas development is carried out, and particularly, along with the increasing of the development strength of unconventional energy sources, deep wells and ultra-deep wells in China are increased continuously in recent years, and more severe performance requirements are provided for a high-pressure manifold system of fracturing equipment. The movable elbow is a product capable of accurately controlling the flow direction of a fracturing medium, and due to the special structure of the movable elbow, the inner wall is often corroded and eroded, so that the movable elbow further leaks or cracks to lose efficacy, and the movable elbow is the weakest link of a high-pressure manifold system. At present, companies at home and abroad can produce 140MPa movable elbow products.

In patent CN201810029961, in order to improve the safety of the movable elbow of 140MPa or above, a carbon fiber composite material reinforced ultrahigh pressure movable elbow is disclosed, the inner wall adopts conventional alloy steel, and the outer surfaces of the elbow and the straight head are covered with carbon fiber material.

The 175MPa movable elbow product is not reported abroad, and the metal material and the manufacturing method are not reported at home. The existing movable elbow metal materials with the pressure of 140MPa and below comprise carburizing alloy steel (such as 20CrNiMo, 20CrMnTi, 15CrNiMo, 18CrMnNiMo and the like) and quenched and tempered steel (such as 35CrMo, 42CrMo, 40CrNiMo, 40CrNi2Mo and the like), and because the toughness, the hardenability, the erosion resistance and the stress corrosion resistance of the materials are limited, the materials are difficult to perfectly match, and the construction requirements of fracturing operation with the pressure of 175MPa cannot be met. In the current alloy structural steel standard GB/T3077-.

Disclosure of Invention

The invention aims to provide a novel movable elbow material which can meet the construction requirement of large-scale fracturing operation under 175MPa at most after being subjected to heat treatment.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a175 MPa movable elbow material is characterized in that:

the weight percentages of the elements in the material are as follows: 0.12 to 0.20 weight percent of C, 0.4 to 0.7 weight percent of Cr0, 1.4 to 2.0 weight percent of Nis, 0.6 to 1.2 weight percent of Mns, 0.55 to 0.8 weight percent of Mos, less than or equal to 0.25 weight percent of Si, less than or equal to 0.15 weight percent of (Nb + V + Ti), less than or equal to 0.2 weight percent of Cu, less than or equal to 0.015 weight percent of P, less than or equal to 0.010 weight percent of S, less than or equal to 0.010 weight percent of Sn, less than or equal to 0.005 weight percent of Sb, less than or equal to 0.005 weight percent of As, less than or equal to 2ppm of H, less than or equal to.

A heat treatment process of a 175MPa movable elbow material comprises the following steps:

the method is characterized in that: the process comprises the following specific steps:

(1) normalizing the movable elbow material firstly and then tempering: the normalizing treatment process parameters are as follows: charging the blank at the temperature of below 400 ℃, heating to 920-960 ℃ at the heating speed of less than or equal to 100 ℃/h, preserving heat for 0.5-2 h, discharging and cooling, and cooling to below 200 ℃ in an air cooling, air flow or fog cooling mode; the tempering treatment process parameters are as follows: charging the normalized blank at the temperature of below 400 ℃, heating to 620-680 ℃, preserving heat for 4-8 hours, discharging and cooling, and cooling to room temperature by adopting an air cooling, air flow or fog cooling mode;

(2) and then carrying out carburizing, quenching and tempering treatment: the carburizing technological parameters are as follows: performing strong carburization at 920-940 ℃ by adopting a pit-type carburizing furnace or a multi-purpose furnace, keeping the temperature for 4-8 hours, and controlling the carbon potential to be 1.10-1.25%; performing carbon diffusion at 920-940 ℃, keeping the temperature for 3-6 hours, and controlling the carbon potential to be 0.85-1.05%; the carburizing and quenching process parameters are as follows: after carburization and diffusion are finished, furnace cooling is carried out to 820-860 ℃, heat preservation is carried out for 0.5-2 h, carbon potential is controlled to be 0.80-0.95%, then quenching treatment is carried out, and the quenching cooling mode is oil cooling; the tempering technological parameters after carburizing and quenching are as follows: after cooling the product to below 80 ℃, tempering in time at 180-220 ℃ for 3-5 h;

(3) and finally performing cold treatment and tempering treatment: the cold treatment process parameters are as follows: adopting liquid nitrogen as a refrigerant, placing the product after carburized quenching and tempering at-60 to-120 ℃ for 1-3h, then slowly heating the product to room temperature, and then carrying out tempering treatment, wherein the tempering treatment process parameters are as follows: the tempering temperature is 180-220 ℃, and the heat preservation time is 3-5 h.

The invention has the positive effects that:

1. compared with the 20CrNiMo alloy which is a common material for movable elbows, the alloy obtained by the invention has high strength and toughness, the strength is improved by more than 20 percent, the impact toughness is improved by more than 100 percent, the stress corrosion resistance is strong, the erosion weight loss under unit conditions is reduced by more than 50 percent, and the requirement of fracturing construction operation under 175MPa can be met to the maximum extent.

2. Under the working condition of fracturing operation of 140MPa or below, the service life of the movable elbow prepared by the material can be prolonged by more than 50%.

Detailed Description

The present invention will be further described with reference to the following specific examples.

Example one

Smelting in an electric arc furnace, vacuum refining, die casting, rolling and preparing into a movable elbow blank. The weight percentage of each component in the obtained material is as follows: c0.13wt%, Cr0.65wt%, Ni1.46wt%, Mn1.12wt%, Mo 0.64wt%, Si 0.16wt%, Nb 0.077wt%, V0.028 wt%, Ti 0.011wt%, Cu 0.081wt%, P0.011 wt%, S0.004 wt%, Sn 0.005wt%, Sb 0.005wt%, As 0.005wt%, H1.2 ppm, O13 ppm, N55 ppm, and the balance of Fe and unavoidable impurities.

The heat treatment steps of the movable elbow material blank are as follows:

(1) normalizing the movable elbow material firstly and then tempering; the normalizing treatment process parameters are as follows: charging the blank at the temperature of below 400 ℃, heating to 920 ℃ at the heating speed of less than or equal to 100 ℃/h, preserving heat for 2h, discharging and cooling, and cooling to below 200 ℃ in an air cooling mode; the tempering treatment process parameters are as follows: and charging the normalized blank at the temperature of below 400 ℃, heating to 620 ℃, preserving heat for 8 hours, discharging from the furnace, cooling, and cooling to room temperature by adopting an air cooling mode.

(2) Carburizing, quenching and tempering the product, wherein the carburizing technological parameters are as follows: strong carburization is carried out at 920 ℃ by adopting a well type carburizing furnace, the heat preservation time is 8 hours, and the carbon potential is controlled to be 1.15%; carbon diffusion is carried out at 920 ℃, the heat preservation time is 3 hours, and the carbon potential is controlled at 0.9%; the carburizing and quenching process parameters are as follows: after carburization and diffusion are finished, furnace cooling is carried out to 820 ℃, heat preservation is carried out for 2 hours, the carbon potential is controlled to be 0.80%, then quenching treatment is carried out, and the quenching cooling mode is oil cooling; the tempering technological parameters after carburizing and quenching are as follows: after the product is cooled to below 80 ℃, tempering is carried out in time, the tempering temperature is 180 ℃, and the heat preservation time is 5 hours;

3. performing cold treatment and tempering treatment; the cold treatment process parameters are as follows: adopting liquid nitrogen as a refrigerant, placing the product after carburized quenching and tempering at-60 ℃, keeping the temperature for 3h, then slowly heating the product to room temperature, and then carrying out tempering treatment, wherein the tempering treatment process parameters are as follows: the tempering temperature is 180 ℃, and the heat preservation time is 5 hours.

Example two

Smelting in an electric arc furnace, vacuum refining, die casting, rolling and preparing into a movable elbow blank. The weight percentage of each component in the obtained material is as follows: 0.19wt% of C, 0.53wt% of Cr, 1.63wt% of Ni, 0.88wt% of Mn, 0.59wt% of Mo, 0.18wt% of Si, 0.063wt% of Nb, 0.027wt% of V, 0.016wt% of Ti, 0.09wt% of Cu, 0.012wt% of P, 0.004wt% of S, 0.005wt% of Sn, 0.005wt% of Sb, 0.005wt% of As, 1.1ppm of H, 12ppm of O, 53ppm of N, and the balance of Fe and inevitable impurities.

The heat treatment steps of the movable elbow material blank are as follows:

(1) normalizing the movable elbow material firstly and then tempering; the normalizing treatment process parameters are as follows: charging the blank at the temperature of below 400 ℃, heating to 960 ℃ at the heating speed of less than or equal to 100 ℃/h, preserving heat for 0.5h, discharging and cooling, and cooling to below 200 ℃ in a fog cooling mode; the tempering treatment process parameters are as follows: and charging the normalized blank at the temperature of below 400 ℃, heating to 680 ℃, preserving heat for 4 hours, discharging from the furnace, cooling, and cooling to room temperature by adopting a fog cooling mode.

(2) Carburizing, quenching and tempering the product, wherein the carburizing technological parameters are as follows: strong carburization is carried out at 940 ℃ by adopting a multipurpose furnace, the heat preservation time is 4 hours, and the carbon potential is controlled to be 1.25%; performing carbon diffusion at 940 ℃, keeping the temperature for 6 hours, and controlling the carbon potential to be 1.0%; the carburizing and quenching process parameters are as follows: after carburization and diffusion are finished, furnace cooling is carried out to 860 ℃, heat preservation is carried out for 0.5h, carbon potential is controlled to be 0.90%, and then quenching treatment is carried out, wherein the quenching cooling mode is oil cooling; the tempering technological parameters after carburizing and quenching are as follows: after the product is cooled to below 80 ℃, tempering in time at 220 ℃ for 3 h;

3. performing cold treatment and tempering treatment; the cold treatment process parameters are as follows: adopting liquid nitrogen as a refrigerant, placing the product after carburized quenching and tempering at-120 ℃, keeping the temperature for 1h, then slowly heating the product to room temperature, and then carrying out tempering treatment, wherein the tempering treatment process parameters are as follows: the tempering temperature is 220 ℃, and the heat preservation time is 3 hours.

EXAMPLE III

Smelting in an electric arc furnace, vacuum refining, die casting, rolling and preparing into a movable elbow blank. The weight percentage of each component in the obtained material is as follows: 0.15wt% of C, 0.58wt% of Cr, 1.87wt% of Ni, 0.93wt% of Mn, 0.71wt% of Mo, 0.12wt% of Si, 0.054wt% of Nb, 0.049wt% of V, 0.008wt% of Ti, 0.063wt% of Cu, 0.014wt% of P, 0.005wt% of S, 0.005wt% of Sn, 0.005wt% of Sb, 0.005wt% of As, 1.1ppm of H, 14ppm of O, 52ppm of N, and the balance of Fe and inevitable impurities.

The heat treatment steps of the movable elbow material blank are as follows:

(1) normalizing the movable elbow material firstly and then tempering; the normalizing treatment process parameters are as follows: charging the blank at the temperature of below 400 ℃, heating to 940 ℃ at the heating speed of less than or equal to 100 ℃/h, preserving heat for 1h, discharging and cooling, and cooling to below 200 ℃ in an air cooling mode; the tempering treatment process parameters are as follows: and charging the normalized blank at the temperature of below 400 ℃, heating to 650 ℃, preserving heat for 6 hours, discharging from the furnace, cooling, and cooling to room temperature by adopting an air cooling mode.

(2) Carburizing, quenching and tempering the product, wherein the carburizing technological parameters are as follows: strong carburization is carried out at 930 ℃ by adopting a multipurpose furnace, the heat preservation time is 6 hours, and the carbon potential is controlled to be 1.20%; performing carbon diffusion at 930 ℃, and keeping the temperature for 5 hours, wherein the carbon potential is controlled to be 0.95%; the carburizing and quenching process parameters are as follows: after carburization and diffusion are finished, furnace cooling is carried out to 840 ℃, heat preservation is carried out for 1h, the carbon potential is controlled to be 0.85%, then quenching treatment is carried out, and the quenching cooling mode is oil cooling; the tempering technological parameters after carburizing and quenching are as follows: after the product is cooled to below 80 ℃, tempering is carried out in time, the tempering temperature is 200 ℃, and the heat preservation time is 4 hours;

3. performing cold treatment and tempering treatment; the cold treatment process parameters are as follows: adopting liquid nitrogen as a refrigerant, placing the product after carburized quenching and tempering at-90 ℃, keeping for 2h, then slowly heating the product to room temperature, and then carrying out tempering treatment, wherein the tempering treatment process parameters are as follows: the tempering temperature is 200 ℃, and the heat preservation time is 4 hours.

The 175MPa movable elbow materials of the examples 1-3 are tested for tensile strength, yield strength, elongation, -29 ℃ impact absorption power, stress corrosion resistance and erosion resistance, the test results are shown in the table 1, and the table 1 also lists the mechanical property data of the 20CrNiMo alloy of the common movable elbow material as comparison. The mechanical properties are carried out according to A370 standard. The stress corrosion resistance test is carried out according to the simulated oil field acidizing fracturing working condition, and the specific method comprises the following steps: keeping the material in a 20% HCI solution for 720 hours under the constant load according to the highest actual working stress (the highest stress of a 175MPa movable elbow is 630 MPa) of a designed product, and if the material does not crack, evaluating the material to be qualified through an experiment; if the crack is detected, the crack is judged to fail. The erosion test is also used for simulating an oil field fracturing medium, and the specific method comprises the following steps: the quartz sand is used as a simulated fracturing medium, the particle size is 30 meshes, the erosion angle is 30 degrees, the sand content is 14 percent, the medium flow rate is 20m/s, and the erosion time is 1 hour.

Table 1 results of material property tests of examples 1-3

Examples	Tensile strength MPa	Yield strength MPa	-29 ℃ impact absorption work	Stress corrosion resistance test	Erosion weight loss g	Average service life h
							1	1380	1245	87	By passing	0.41	≥900
2	1400	1265	119	By passing	0.32	≥900
							3	1410	1280	128	By passing	0.29	≥900
20CrNiMo	1150	1030	36	Failed through	0.85	≤550

The functions of the elements in the alloy steel obtained by the invention are as follows: c increases the strength of the alloy steel and cannot be too high, otherwise the toughness is reduced. Cr can ensure corrosion resistance of the steel. Ni can improve the hardenability of the material, enhance the obdurability and improve the corrosion resistance to various acids. Mn can deoxidize, form sulfide, increase hardenability and obdurability, and improve the wear resistance and erosion resistance of the alloy steel. Mo can improve hardenability and toughness, and especially can improve stress corrosion resistance; and the wear resistance and the erosion resistance of the alloy steel can be improved. Cu can improve the corrosion resistance of alloy steel to acid and improve the machining performance of steel. Nb, V and Ti are elements which can be selectively added with one or two or three, and form carbide or nitride, thereby inhibiting the growth of alloy steel grains, strengthening the matrix and improving the wear resistance and erosion resistance of the alloy steel. Therefore, the alloy steel alloy has high obdurability, strong stress corrosion resistance and erosion resistance, can improve the safety of the movable elbow product and prolong the service life, and ensures that the highest service pressure of the movable elbow is increased from the prior highest 140MPa to 175 MPa.

Claims (1)

1. A heat treatment process of a 175MPa movable elbow material comprises the following elements in percentage by weight: 0.12 to 0.20wt% of C, 0.4 to 0.7wt% of Cr0.4 to 2.0wt% of Ni1.4 to 2.0wt%, 0.6 to 1.2wt% of Mn0.55 to 0.8wt% of Mo0.55 wt%, less than or equal to 0.25wt% of Si, less than or equal to 0.15wt% of (Nb + V + Ti), less than or equal to 0.2wt% of Cu, less than or equal to 0.015wt% of P, less than or equal to 0.010wt% of S, less than or equal to 0.010wt% of Sn, less than or equal to 0.005wt% of Sb, less than or equal to 0.005wt% of As, less than or equal to 2ppm of H;

the method is characterized in that: the process comprises the following specific steps:

(1) normalizing the movable elbow material firstly and then tempering: the normalizing treatment process parameters are as follows: charging the blank at the temperature of below 400 ℃, heating to 920-960 ℃ at the heating speed of less than or equal to 100 ℃/h, preserving heat for 0.5-2 h, discharging and cooling, and cooling to below 200 ℃ in an air cooling, air flow or fog cooling mode; the tempering treatment process parameters are as follows: charging the normalized blank at the temperature of below 400 ℃, heating to 620-680 ℃, preserving heat for 4-8 hours, discharging and cooling, and cooling to room temperature by adopting an air cooling, air flow or fog cooling mode;

(2) and then carrying out carburizing, quenching and tempering treatment: the carburizing technological parameters are as follows: performing strong carburization at 920-940 ℃ by adopting a pit-type carburizing furnace or a multi-purpose furnace, keeping the temperature for 4-8 hours, and controlling the carbon potential to be 1.10-1.25%; performing carbon diffusion at 920-940 ℃, keeping the temperature for 3-6 hours, and controlling the carbon potential to be 0.85-1.05%; the carburizing and quenching process parameters are as follows: after carburization and diffusion are finished, furnace cooling is carried out to 820-860 ℃, heat preservation is carried out for 0.5-2 h, carbon potential is controlled to be 0.80-0.95%, then quenching treatment is carried out, and the quenching cooling mode is oil cooling; the tempering technological parameters after carburizing and quenching are as follows: after cooling the product to below 80 ℃, tempering in time at 180-220 ℃ for 3-5 h;

(3) and finally performing cold treatment and tempering treatment: the cold treatment process parameters are as follows: adopting liquid nitrogen as a refrigerant, placing the product after carburized quenching and tempering at-60 to-120 ℃ for 1-3h, then slowly heating the product to room temperature, and then carrying out tempering treatment, wherein the tempering treatment process parameters are as follows: the tempering temperature is 180-220 ℃, and the heat preservation time is 3-5 h.