CN111270068A - Surface strengthening process for prolonging fatigue life of intersecting line position of inner cavity of pump head body of fracturing pump - Google Patents
Surface strengthening process for prolonging fatigue life of intersecting line position of inner cavity of pump head body of fracturing pump Download PDFInfo
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- CN111270068A CN111270068A CN202010298320.5A CN202010298320A CN111270068A CN 111270068 A CN111270068 A CN 111270068A CN 202010298320 A CN202010298320 A CN 202010298320A CN 111270068 A CN111270068 A CN 111270068A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D10/00—Modifying the physical properties by methods other than heat treatment or deformation
- C21D10/005—Modifying the physical properties by methods other than heat treatment or deformation by laser shock processing
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Abstract
In order to solve the problems of insufficient fatigue strength of the intersecting line position of the inner cavity of the pump head body of the fracturing pump treated by the prior art, complex treatment process, high energy consumption and the like, the invention provides a surface strengthening process for prolonging the fatigue life of the intersecting line position of the inner cavity of the pump head body of the fracturing pump, which comprises the following steps: performing surface strengthening treatment on the weak position of the 4330 steel pump head body by adopting a laser shock strengthening technology, wherein the power density of laser is (2-9) multiplied by 109W/cm2The laser pulse width is 8-20ns, the absorption protective layer is black adhesive tape or black paint, and the restraint layer is water. The laser shock peening technology can at least improve the fatigue life by more than 2.05 times. After laser shock strengthening treatment, the maximum value of the residual compressive stress is 618.7MPa at the position of 0.2mm of the subsurface layer, and the residual compressive stress is in a state within 1.5mm away from the surface; microhardness of 354.7HV0.2Is lifted to 421.8HV0.2And the improvement is 18.9 percent.
Description
Technical Field
The invention belongs to the field of anti-fatigue manufacturing of metal parts, and particularly relates to a process for strengthening treatment of a metal surface and prolonging the fatigue life of a material of a pump head body of a fracturing pump.
Background
The fracturing equipment provides hardware support for fracturing operation, the core equipment is a fracturing pump, the pump head body is used as a core component of the fracturing pump, the inner cavity structure is complex, and the fracturing pump is generally composed of three groups or five groups of through inner holes. The pump body is used as an expensive wearing part in the fracturing equipment, the inner cavity bears a pulsating circulation high-pressure load in the field service process, and stress concentration at the intersecting line can influence a stress strain field of a crack tip, so that fatigue cracking occurs at the intersecting line of the plug cavity, the discharge cavity and the plunger hole of the pump body. Because the working environment is severe, the average service life of the ultra-high pressure pump head body in China is usually less than 100h and far lower than that of other conventional components in fracturing equipment, and the development efficiency and the economic benefit of an oil-gas field are seriously influenced. Therefore, it is necessary to study the strengthening process for increasing the lifetime of the pump head body.
At present, fatigue sources of a pump head body of a fracturing pump are all located at the position of an intersecting line, and the service life of the pump head body of the fracturing pump is prolonged mainly by focusing on a surface treatment method at the intersecting line.
(1) Shot peening
Shot peening is a surface strengthening process which utilizes a fine shot of high-speed shot to impact a intersecting line region of a pump head body to enable a metal surface layer in the intersecting line region to generate elastic and plastic deformation and enable the surface layer to be in a residual compressive stress state.
The shot peening has the advantages that: the process is mature and the equipment is simple. However, the reinforcing layer is usually about 0.3mm, the effect of improving the fatigue performance is limited, and the consumption of consumables and the environmental pollution are serious.
(2) Chemical heat treatment
The chemical heat treatment process is to carburize the specific medium carbon alloy structural steel, control the depth of the carburized layer and the carbide level, and then directly quench and temper to obtain higher surface hardness. The strengthening process can generate high pressure stress on the surface or subsurface of the workpiece through heat treatment, so that the surface of the workpiece forms uniform and complete martensite, and the fatigue performance of the pump head body is further improved.
The chemical heat treatment process has the advantages that: the strengthening effect is obvious. However, the pump head body has a large size, so that the requirement on heat treatment equipment is high, and the heat treatment cost and the energy consumption are greatly increased.
(3) Self-enhancing treatment
The self-reinforcing treatment technology is that the inner wall of a pump head body before use is loaded with ultrahigh pressure plum, so that a plastic deformation layer with a certain thickness is formed on a component from inside to outside, then the loaded ultrahigh pressure is unloaded, at the moment, the elastic part of the outer layer is recovered, and the plastic layer of the inner layer is compressed, so that residual compressive stress is generated.
The self-enhancement treatment technology has the advantages that: the pressure distribution of the inner cavity of the treated component is more uniform, partial working pressure can be offset, and the whole pressure level of the inner cavity is reduced. Due to the variety of types of pump head bodies and the difference of the structures of the pump head bodies, the cost for selecting a proper self-reinforcing process for a manufacturer is increased. Meanwhile, the mechanical extrusion may cause damage to the outer surface of the inner wall in the operation process, the direct static pressure method often encounters the problems of pressure source, pipeline and sealing of ultrahigh pressure, the explosive expansion method cannot ensure the consistency of the treatment state in the cavity, and the implementation difficulty of the solid self-reinforcing process is high.
Disclosure of Invention
In summary, the technical problems to be solved in the invention are that the fatigue strength of the pump head body of the fracturing pump treated by the prior art is not high enough, the treatment process is complex, and the energy consumption is high. Therefore, the surface of the intersecting line of the inner cavity of the pump head body of the fracturing pump is strengthened by adopting a laser shock strengthening technology, so that a residual compressive stress layer is formed on the surface layer of the metal, and the fatigue strength and the microhardness of the metal material of the pump head body are improved.
The laser shock peening technology is a relatively advanced surface peening technology in recent years, and the principle is shown in fig. 1. The power density reaches (2-9) multiplied by 109W/cm2The high-energy laser with the pulse width of 8-20ns is irradiated on the metal surface to absorb a protective layer (black adhesive tape or black paint), after the protective layer absorbs the laser energy, part of the protective layer is rapidly gasified and further absorbs the laser energy to generate plasma explosion, a water restraint layer can generate a restraint effect on plasma explosion waves, then the plasma explosion induces the generation of shock waves with the pressure of 10GPa on the metal surface, and a residual pressure stress layer with the thickness of more than 1.5mm can be introduced into the metal surface layer, so that the surface of a part is strengthened, and the fatigue performance is greatly improved.
Compared with shot peening, chemical heat treatment and self-reinforcing treatment, the laser shock peening technology has obvious advantages in equipment requirement, process complexity, strengthening effect and processing cost.
Shot peening: the equipment usually handles the surface of metal parts, handles the inner chamber and needs the special shower nozzle of customization, along with the increase of the pipeline of sending by ease, and some accessories such as supporting air compressor machine, pressure storage tank can improve thereupon, and the equipment volume has extremely increased. Because the participating pressure stress layer is shallow, the fatigue improvement effect after treatment is limited. And the consumption of the pill material can obviously increase the cost.
Chemical heat treatment; because the whole pump head body is placed in a heat treatment furnace, the inner cavity is treated according to requirements in the chemical heat treatment process, and the outer wall and the connecting part are additionally treated, the connecting part is possibly hardened, and the subsequent sealing problem is brought.
Laser shock peening: the movable equipment is adopted, the strengthening process parameters are adjustable, the telescopic tool is customized at the laser light outlet, and the strengthening requirements of inner cavity intersecting lines with different specifications and sizes can be met. Fig. 2 is a schematic diagram of the strengthening of the pump head body of the fracturing pump.
Therefore, the technical scheme adopted by the invention comprises the following steps: surface strengthening treatment is carried out on the metal material part of the 4330 steel pump head body by adopting a laser shock strengthening technology, and the power density of laser is (2-9) multiplied by 109W/cm2The laser pulse width is 8-20ns, the absorption protective layer is black adhesive tape or black paint, and the restraint layer is water.
When the laser shock peening technology is adopted for processing, the off-line programming is adopted according to the characteristic appearance of the intersecting line of the inner cavities of the pump head bodies of the fracturing pumps with different specifications, the to-be-processed positions are modeled in real time, the optimal peening parameters are ensured to be injected into each shock point, and finally the fatigue life is greatly prolonged.
The energy of the laser is 5J, the diameter of a light spot is 2.6mm, the pulse width is 18 ns, and the lap joint rate is 50%.
The invention has the beneficial effects that:
the process has the characteristics of simple treatment mode, obvious fatigue improvement effect, low processing cost and the like.
Drawings
FIG. 1 is a schematic diagram of laser shock peening;
FIG. 2 is a schematic diagram of laser shock peening of a pump head body of a fracturing pump
FIG. 3 laser shock peening effect (a) gradient residual stress; (b) micro-hardness.
Detailed Description
The invention is further illustrated by the following examples.
Example 1
A surface strengthening process for prolonging the fatigue life of a metal material of a pump head body of a fracturing pump and effect verification are mainly disclosed.
15-5ph steel and 4330 steel are two common brands of fracturing pump head bodies, 4330 steel belongs to low-alloy high-strength steel, the cost is lower, and the pump head body belongs to a vulnerable part, so the proportion of 4330 steel is higher. Therefore, the pump head body 4330 steel material is used as a laser shock peening object to verify the anti-fatigue effect of the laser shock peening technology. Taking the laser shock peening parameters listed in table 1 as an example, the steel material of the pump head body 4330 is strengthened.
According to experience, the fatigue strength of the material is usually 0.55-0.6σ 0.2In order to quickly verify the anti-fatigue effect of laser shock peening, 0.8 test load is selectedσ 0.2. Meanwhile, after the strengthening treatment is finished, the gradient residual stress and microhardness are measured.
1 sample preparation and laser shock peening
A four-point bending fatigue test method is selected to verify the strengthening effect, the fatigue test specification is 10mm multiplied by 100mm, 400#, 600#, 1000# and 1500# metallographic abrasive paper is used for sequentially grinding four 10mm multiplied by 100mm surfaces and then polishing the four 10mm multiplied by 100mm surfaces, and after polishing is completed, laser shock strengthening treatment is carried out on one surface according to the process in the table 1.
2 test for Effect of enhancement
2.1 fatigue test
Four-point bending test conditions, load 0.8σ 0.2The stress R was 0.1 and the frequency was 68 Hz. The surface fatigue life was evaluated without strengthening and after strengthening.
2.2 gradient stress and microhardness test
The gradient residual stress test is carried out on the strengthening area of the 4330 steel by adopting the methods of X-ray diffraction and electrolytic polishing, and the microhardness of the surfaces in two states is tested.
3 reinforcing effect
3.1 fatigue life
4330 the results of the four-point bending fatigue test of the steel in different surface states are shown in table 2. Fatigue fractures occurred in the unreinforced samples for an average cycle of 32.84 million cycles, while the samples after reinforcement were cycled at least 100 million cycles and remained free of fatigue fractures. It can be concluded that the laser shock peening technique can improve the fatigue life by at least 2.05 times under the same stress level.
3.2 gradient residual stress and microhardness test results
The gradient residual stress and microhardness test results are shown in fig. 3(a) and 3(b), respectively. As shown in FIG. 3(a), after the laser shock peening treatment, the residual compressive stress value was at most-618.7 MPa at the 0.2mm position of the subsurface layer, and the residual compressive stress was maintained within 1.5mm from the surface. As can be seen from FIG. 3(b), the microhardness of the steel sheet after the laser shock peening treatment is 354.7Hv0.2Lifted to 421.8Hv0.2And the improvement is 18.9 percent.
COMPARATIVE 1 shot peening vs. laser shock peening Gear machining efficiency and cost comparison
To machine the gear root part 3720 mm2The area is taken as an example, and 20 ten thousand pieces are produced every year. The machining efficiency and machining cost ratio of the heavy shot peening and the laser shock peening are shown in table 3.
As can be seen from Table 3, the laser shock peening can be performed with less personnel, no pollution and extremely low material cost compared to the shot peening, which can also perform 20 ten thousand gear treatments per year.
Comparison 2 enhanced effect comparison
Table 4 shows the mechanical rolling, shot peening, and laser shock peening for strength comparison.
The laser shock peening can significantly improve the depth of the residual compressive stress layer, so the fatigue improvement performance is most obvious in the common surface strengthening means.
Claims (3)
1. A surface strengthening process for prolonging the fatigue life of a intersecting line position in an inner cavity of a pump head body of a fracturing pump is characterized by comprising the following steps of: surface strengthening treatment is carried out on the intersecting line position of the inner cavity of the 4330 steel pump head body by adopting a laser shock strengthening technology, and the power density of laser is (2-9) multiplied by 109W/cm2The laser pulse width is 8-20ns, the absorption protective layer is black adhesive tape or black paint, and the restraint layer is water.
2. The process of claim 1 wherein the laser has an energy of 5J, a pulse width of 18 ns, and a lap ratio of 50%.
3. The process as claimed in claim 1, wherein during the laser shock peening, the position to be treated is modeled in real time to determine the characteristic profile of the intersecting line of the inner cavity of the pump head body of the fracturing pump to be treated, and the peening parameters of each shock point are adjusted according to the characteristic profile to greatly improve the fatigue life.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113088675A (en) * | 2021-03-30 | 2021-07-09 | 三一石油智能装备有限公司 | Strengthening treatment method for fracturing pump element |
| CN114959533A (en) * | 2022-06-22 | 2022-08-30 | 沈阳工业大学 | Laser shock peening method for improving depth and fatigue performance of compressive stress layer on surface of titanium alloy |
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| CN108531711A (en) * | 2018-05-28 | 2018-09-14 | 江苏大学 | A kind of method and apparatus of X-shaped pipe fitting intersection shape seam laser shock peening |
| CN108977640A (en) * | 2018-09-10 | 2018-12-11 | 中石化四机石油机械有限公司 | A kind of stress peening process method of fracturing pump valve chamber |
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2020
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| CN105177273A (en) * | 2015-09-30 | 2015-12-23 | 江苏大学 | Laser shock enchantment method for improving fatigue strength of key and important member |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113088675A (en) * | 2021-03-30 | 2021-07-09 | 三一石油智能装备有限公司 | Strengthening treatment method for fracturing pump element |
| CN114959533A (en) * | 2022-06-22 | 2022-08-30 | 沈阳工业大学 | Laser shock peening method for improving depth and fatigue performance of compressive stress layer on surface of titanium alloy |
| CN114959533B (en) * | 2022-06-22 | 2023-06-23 | 沈阳工业大学 | Laser shock strengthening method for improving depth of compressive stress layer and fatigue performance of titanium alloy surface |
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Application publication date: 20200612 |