CN112903497A - Steel constant-load stress corrosion test device and method under periodic infiltration condition - Google Patents
Steel constant-load stress corrosion test device and method under periodic infiltration condition Download PDFInfo
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- CN112903497A CN112903497A CN202110057346.5A CN202110057346A CN112903497A CN 112903497 A CN112903497 A CN 112903497A CN 202110057346 A CN202110057346 A CN 202110057346A CN 112903497 A CN112903497 A CN 112903497A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/56—Investigating resistance to wear or abrasion
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
- G01N17/002—Test chambers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
- G01N17/006—Investigating resistance of materials to the weather, to corrosion, or to light of metals
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
- G01N3/04—Chucks
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/022—Environment of the test
- G01N2203/0236—Other environments
- G01N2203/024—Corrosive
Abstract
The invention discloses a steel constant-load stress corrosion test device and method under a periodic infiltration condition. The stress loading unit in the test device comprises a steel test piece, a horizontal loading reaction frame, an L-shaped pull rod, a guide sleeve, a force sensor and a loading nut; the periodic infiltration unit in the test device comprises a master control system, a corrosion test groove, a solution supply box, a hydraulic lifting table, a liquid level control switch, a heating lamp group and a temperature measurement sensor. After the stress loading unit finishes constant load loading on the steel test piece, the periodic infiltration unit realizes periodic circulation of the steel test piece between the infiltration of the corrosion solution and the high-temperature drying by adjusting the relative height difference between the solution supply tank and the corrosion test tank and the switch of the heating lamp group. The test device is definite in stress, the principle of the test method is simple, the constant load stress corrosion test and the periodic infiltration corrosion test of steel are combined, and the corrosion environment of the steel structure under the action of constant tensile stress working in the ocean splash zone environment can be simulated.
Description
Technical Field
The invention relates to the field of metal corrosion protection, in particular to a steel constant-load stress corrosion test device and method under a periodic infiltration condition.
Background
Stress corrosion of steel refers to the behavior of steel to corrode under the combined action of stress (especially tensile stress) and a specific corrosion medium, and ultimately to cause brittle fracture of the steel. The stress corrosion cracking of steel is different from ordinary tensile failure and pure steel corrosion: when the steel contacts sensitive corrosive media, the steel can be broken under the condition of lower stress; in the sensitive corrosive medium with lower concentration, the corrosion rate of the steel is obviously improved due to the stress action. In particular for stainless steels, such as austenitic stainless steels, which have good corrosion resistance in the absence of stress, stress corrosion is prone to occur in chloride ion corrosive media. Stress corrosion cracking is a brittle fracture which occurs without any warning sign and which rapidly propagates once the microcracks propagate to critical cracks, resulting in sudden fractures, seriously threatening the safety of the structure.
The periodic infiltration corrosion test is one of the most effective test methods for simulating the corrosion environment of an ocean splash zone, and can realize periodic dry-wet circulation of a steel test piece in a corrosion medium. However, most of the conventional periodic infiltration corrosion test devices are designed for unstressed test pieces, and load monitoring equipment required for performing a constant-load stress corrosion test cannot be directly placed in a conventional periodic infiltration test box. At present, a test device and a test method which combine a constant load stress corrosion test and a periodic infiltration corrosion test of steel are lacked. The invention provides a device and a method for testing stress corrosion of steel under a periodic infiltration condition, which can be used for carrying out stress corrosion test research on the steel under the periodic infiltration condition.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a steel constant-load stress corrosion test device and method under the periodic infiltration condition, which can simulate the dry-wet cycle state of an ocean splash zone by periodically infiltrating a steel test piece under the action of constant tensile stress in a corrosion medium, thereby further researching the stress corrosion phenomenon of the steel in the corrosion medium.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the invention provides a steel constant-load stress corrosion test device under a periodic infiltration condition, which comprises a periodic infiltration unit and at least one stress loading unit;
each stress loading unit comprises a steel test piece, a horizontal loading reaction frame, a force sensor, an L-shaped pull rod, a guide sleeve and two loading nuts; the short-edge ends of the two L-shaped pull rods respectively hook one end of the steel test piece, the long edges of the two L-shaped pull rods respectively penetrate through the corresponding sides of the horizontal loading reaction frame through the guide sleeves arranged in the horizontal loading reaction frame, the L-shaped pull rods on one side are sequentially sleeved with the force sensor and one loading nut after penetrating out of the horizontal loading reaction frame, and the L-shaped pull rods on the other side are sleeved with the other loading nut and fix the positions of the loading nuts; the loading nut on one side of the force sensor is screwed and fixed to load the steel test piece under constant tensile stress, and the load is read by the force sensor;
the periodic infiltration unit comprises a master control system, a solution supply box containing a corrosion solution, a hydraulic lifting table, corrosion test grooves, a liquid level control switch, a heating lamp group and temperature measurement sensors, wherein the number of the corrosion test grooves is the same as that of the stress loading units; each heating lamp group is respectively arranged above one corresponding horizontal loading reaction frame, each steel test piece after being loaded is respectively suspended in one corresponding corrosion test groove, each corrosion test groove is respectively communicated with the solution supply box through a guide pipe, the solution supply box is placed on the hydraulic lifting table, the hydraulic lifting table is controlled by the master control system to periodically lift and lower, and the heating lamp groups are periodically switched off and switched on, so that the corrosion solution periodically flows into and flows out of the corrosion test grooves, and the periodic circulation of the steel test pieces between corrosion solution infiltration and high-temperature drying is realized; each liquid level control switch is arranged on the inner wall of one corresponding corrosion test groove, and the liquid level height of the corrosion solution in the corrosion test groove is monitored and fed back to the master control system; the temperature sensor is arranged above the corrosion test groove, monitors the environmental temperature after the heating lamp set is started and feeds back the environmental temperature to the master control system.
Furthermore, the steel test piece is an integrally formed structure formed by cutting an original steel to form a plurality of clamping sections and calibration sections which are alternately arranged, a small test piece is formed by one calibration section and the clamping sections at two ends of the calibration section, and the small test pieces in the steel test piece are connected in series.
According to the invention, the steel constant-load stress corrosion test device under the periodic infiltration condition has the following advantages and beneficial effects: firstly, the testing device principle is simple, and the atress is clear and definite, and steel test piece and loading reaction frame all receive the effect of axle center pulling force and pressure in the test process, and the biography power route is clear and definite. Secondly, the device is small in size, a plurality of longitudinal square steel tube spaces can be additionally arranged, a plurality of test groups can be tested at the same time, and the test time is saved; thirdly, the stress loading unit and the periodic infiltration unit which work independently work cooperatively are adopted, the problem that the electrified working equipment (such as a force sensor) cannot be directly placed into a traditional periodic infiltration corrosion test box is solved through the design of the L-shaped pull rod and the guide sleeve, and the stress state of the steel test piece can be monitored in real time in the test process. Fourthly, through different combination modes between the stress loading unit and the periodic infiltration unit, corrosion test researches of various types of steel can be carried out, if the periodic infiltration unit is closed after the steel test piece is loaded, the corrosion test groove is filled with corrosion solution, and then the steel stress corrosion test under the full-infiltration condition can be carried out; if the periodic infiltration unit is started without loading the steel test piece, the conventional steel corrosion test under the periodic infiltration condition can be carried out. Fifthly, the steel test piece is integrally cut into a plurality of small test pieces which are connected in series longitudinally, and after the test is finished, each small test piece is cut and separated. Sixth, the traditional serial loading mode needs to arrange connecting devices among the small test pieces, the steel test piece form provided by the invention can omit such complicated connecting devices, and the influence of corrosion of a corrosive solution on the connecting devices on test results is reduced.
The invention provides a steel constant load stress corrosion test method under a periodic infiltration condition, which comprises the following steps:
assembling the device: after the horizontal loading reaction frame, the corrosion test groove, the solution supply box and the heating lamp group are placed and positioned, the height of the hydraulic lifting table is adjusted, so that no corrosion solution exists in the corrosion test groove, and the heating lamp group is in a closed state; installing the guide sleeves, and enabling long edges of the two L-shaped pull rods to penetrate through the corresponding guide sleeves from the inner side of the horizontal loading reaction frame and penetrate out of the horizontal loading reaction frame; installing the corresponding force sensor and the corresponding loading nut on the outer side of one L-shaped pull rod, and after adjusting the distance between the two L-shaped pull rods, sleeving round holes at two end positions of the steel test piece on the short edge ends of the two L-shaped pull rods, and fixing the steel test piece with the short edge ends of the two L-shaped pull rods after adjusting the steel test piece to be horizontal;
loading: keeping the height of the hydraulic lifting platform unchanged and keeping the heating lamp group switched off; screwing the loading nut on one side provided with the force sensor, applying tension to the steel test piece, monitoring a load value in real time through the force sensor, and fixing the loading nut on one side provided with the force sensor after loading to a designed load to enable the steel test piece to reach a constant load state;
periodic infiltration test: setting the infiltration period and the drying temperature of the test design in the master control system; wherein, the infiltration stage: the master control system controls the hydraulic lifting platform to ascend and the heating lamp set to be closed, corrosive solution flows into the corrosion test groove from the solution supply box, and the hydraulic lifting platform stops ascending when the corrosive solution touches the liquid level control switch, so that the steel test piece under the action of tensile stress is soaked in the corrosive solution; and (3) a drying stage: the master control system controls the hydraulic lifting platform to descend to the lowest level and the heating lamp group to be started, corrosive solution flows back to the solution supply box from the corrosion test groove, the steel test piece under the action of tensile stress is dried, and the heating lamp group performs temperature adjustment according to the feedback of the temperature measuring sensor in the drying process; and the infiltration stage and the drying stage are circulated according to a preset infiltration period, so that the constant-load stress corrosion test of the steel test piece under the periodic infiltration condition is realized.
The steel constant-load stress corrosion test method under the periodic infiltration condition provided by the invention has the following advantages and beneficial effects: the constant load stress corrosion test of steel and the periodic infiltration corrosion test of steel are combined, so that the corrosion environment of a steel structure under the action of constant tensile stress working in the environment of a sea splash zone can be well simulated, and the research on the stress corrosion rule of steel has practical significance.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above, additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the drawings, in which:
fig. 1 is a schematic view of the overall operation of a steel constant-load stress corrosion test apparatus under a periodic infiltration condition according to a first aspect of the present invention.
Fig. 2 (a) and (b) are a top view and a right side view, respectively, of a stress applying unit in the test apparatus shown in fig. 1.
FIG. 3 (a), (b), and (c) are a front view, a right side view, and a plan view, respectively, of the horizontal loading reaction frame in the test apparatus shown in FIG. 1.
FIG. 4 is a schematic view of the structure of the guide sleeve and the L-shaped pull rod in the experimental apparatus shown in FIG. 1.
Fig. 5 (a) and (b) are a front view and a plan view of the hydraulic elevating platform in the test apparatus shown in fig. 1, respectively.
FIG. 6 is a schematic view showing a process of forming a steel material test piece in the test apparatus shown in FIG. 1.
FIG. 7 is a flowchart of a constant-load stress corrosion test method for steel under periodic infiltration conditions according to a second aspect of the present invention.
Reference numerals:
a stress loading unit: 1-steel test piece; 2-horizontal loading reaction frame; 3-an L-shaped pull rod; 4, a guide sleeve; 5-a force sensor; 6, loading a nut; 15-high platform;
wherein, 1-original steel; 1-2-a clamping section; 1-3-calibration section, 1-4-small test piece; 2-1-longitudinal square steel tube; 2-transverse square steel tube; 2-3-foot support; 3-1-long screw; 3-2-solid steel bar; 3-stiffening rib plate; 3-4-test piece positioning nut;
a periodic infiltration unit: 7, a master control system; 8, corrosion test groove; 9-solution supply tank; 10-a catheter; 11-hydraulic lifting platform; 12-liquid level control switch; 13-heating lamp set; 14-a temperature sensor;
wherein, 11-1-hydraulic jack; 11-2-steel platform; 11-3-a guide track; 11-4-pulley.
Detailed Description
The present invention is described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
The following describes a constant-load stress corrosion test device for steel under periodic infiltration conditions according to a first aspect of the present invention with reference to fig. 1 to 5.
As shown in fig. 1, the constant-load stress corrosion test apparatus for steel under periodic infiltration condition according to the first aspect of the present invention includes a periodic infiltration unit and at least one stress loading unit. The stress loading units have the same structure and respectively comprise a steel test piece 1, a horizontal loading reaction frame 2, an L-shaped pull rod 3, a guide sleeve 4, a force sensor 5 and a loading nut 6; the periodic infiltration unit comprises a master control system 7, a corrosion test tank 8, a solution supply box 9, a guide pipe 10, a hydraulic lifting table 11, a liquid level control switch 12, a heating lamp group 13 and a temperature measurement sensor 14.
Specifically, as shown in fig. 2, the stress loading unit comprises a loading nut 6, a force sensor 5, an L-shaped pull rod 3, a steel material test piece 1, an L-shaped pull rod 3 and a loading nut 6 which are sequentially connected in series along the longitudinal axis direction of the horizontal loading reaction frame 2, the horizontal loading reaction frame 2 is clamped between the force sensor 5 and the loading nut 6 positioned on the other side of the force sensor, the L-shaped pull rod 3 penetrates through the horizontal loading reaction frame 2 through a guide sleeve 4, and the guide sleeve 4 can ensure that the L-shaped pull rod 3 only displaces along the horizontal direction. The steel material test piece 1 can be a sheet-shaped or bar-shaped test piece, and round holes are respectively formed at the positions of two end heads of the steel material test piece 1. The force transmission path of the stress loading unit is as follows: when the loading nut 6 on one side of the force sensor 5 is screwed, the force sensor 5 on the side and the loading nut 6 on the other side exert pressure on the horizontal loading reaction frame 2, and when the rigidity of the horizontal loading reaction frame 2 is large enough, the pressure exerted by the loading nut 6 on the force sensor 5 is transmitted to the steel material test piece 1 in an equal and reverse mode, so that the steel material test piece 1 bears the tensile force. The load change applied to the steel test piece 1 is monitored constantly through the force sensor 5 in the loading process, and when the load is loaded to the design load, the loading nut 6 arranged on one side of the force sensor 5 is fastened, so that the constant tensile load is applied to the steel test piece 1. In the process of holding the load, the load change in the process of holding the load can still be monitored through the force sensor 5 and the load value can be adjusted in time. The corrosion test tank 8 is arranged below the rectangular frame structure of the horizontal loading reaction frame 2, and the height of the corrosion test tank needs to meet the requirement that when a corrosion solution is filled in the corrosion test tank, the steel test piece 1 after loading can be completely immersed. The bottom of corrosion test groove 8 and the equal trompil in bottom of solution supply tank 9 and through pipe 10 intercommunication, solution supply tank 9 is placed on hydraulic lifting platform 11, according to the linker principle, can realize through the height of adjusting solution supply tank 9 that corrosion solution flows in, flows out corrosion test groove 8. The hydraulic lifting platform 11 and the heating lamp set 13 are uniformly controlled by the master control system 7, and the master control system 7 controls the hydraulic lifting platform 11 to be periodically lifted and lowered and the heating lamp set 13 to be periodically turned off and on, so that the periodic circulation of the steel test piece 1 between the infiltration of the corrosive solution and the high-temperature drying is realized. Liquid level control switch 12 and temperature sensor 14 can feed back the ambient temperature under the liquid level height and the dry condition in corrosion test groove 8 respectively to total control system 7, and liquid level control switch 12 installs at corrosion test groove 8 inner wall, and temperature sensor installs 14 in corrosion test groove 8 top, and total control system 7 can adjust the height of hydraulic elevating platform 11 respectively and heat the quantity that lamp group 13 opened the heating lamp according to feedback between them.
It should be noted that the stress loading unit is placed on a high platform 15, and the height of the stress loading unit is located between the highest point and the lowest point of the solution supply tank 9 lifted by the hydraulic lifting platform 11. The etching solution is exchanged between the solution supply tank 9 and the corrosion test bath 8 by the relative height difference between the solution supply tank 9 and the corrosion test bath 8. When the solution supply tank 9 is lowered to the lowest point, the corrosion solution completely flows back to the solution supply tank 9 under the action of gravity; when the solution supply tank 9 is raised, the etching solution slowly flows into the etching test tank 8 according to the principle of a communicating vessel, and the solution supply tank stops rising when the liquid surface touches the liquid level control switch 12. The heating lamp set 13 is composed of a plurality of heating bulbs, the ambient temperature is monitored by the temperature measuring sensor 14 and fed back to the master control system 7, and the number of the heating bulbs started in the heating lamp set 13 is controlled. When the monitoring temperature is high, part of the heating bulbs in the heating lamp group 13 are turned off, and when the monitoring temperature is low, more heating bulbs in the heating lamp group 13 are turned on, so that stable temperature control in the test process is realized.
As shown in fig. 3, the horizontal loading reaction frame 2 of the steel constant-load stress corrosion test device under the periodic infiltration condition according to the first aspect of the present invention has a main body of a rectangular frame structure formed by welding two transverse square steel tubes 2-2 and two longitudinal square steel tubes 2-1, wherein four corner positions of the rectangular frame are respectively welded with foot rests 2-3, and the rectangular frame is raised to a position slightly higher than a corrosion test tank 8. A round hole is formed in the middle point of the two transverse square steel tubes 2-2 for placing the guide sleeve 4.
As shown in fig. 4, in the L-shaped pull rod 3 and the guide sleeve 4 of the steel constant-load stress corrosion test apparatus provided by the first aspect of the present invention under the periodic infiltration condition, the long side of the L-shaped pull rod 3 is a long screw rod 3-1, and the short side is a solid steel bar 3-2. One end of the solid steel bar 3-2 is welded and fixed with the long screw 3-1, and a stiffening rib plate 3-3 is arranged; the other end of the solid steel bar 3-2 is reduced to the same size as the hole diameter of the end opening of the steel test piece 1 through a variable cross section. The lower end of the small rod diameter section of the solid steel rod 3-2 is provided with threads for placing a test piece positioning nut 3-4 when the steel test piece 1 is stretched, so that the horizontal placement of the steel test piece 1 in the test process is ensured, and the steel test piece 1 is prevented from falling off. The guide sleeve 4 is fixed in the transverse square steel tube 2-2 of the horizontal loading reaction frame 2, the outer diameter of the guide sleeve is the same as the aperture of the opening of the transverse square steel tube 2-2 of the horizontal loading reaction frame 2, and the inner diameter of the guide sleeve is the same as the rod diameter of the long-edge screw 3-1 of the L-shaped pull rod 3.
As shown in fig. 5, a hydraulic lifting platform 11 of a steel constant-load stress corrosion test apparatus under a periodic infiltration condition according to a first aspect of the present invention includes a hydraulic jack 11-1, a steel platform 11-2, and a guide rail 11-3 and a pulley 11-4, where the hydraulic jack 11-1 is disposed at a lower center position of the steel platform 11-2, the pulleys 11-4 are respectively disposed at four corners of the steel platform 11-2 and are used to clamp the corresponding guide rail 11-3, and a circular hole is formed at a corresponding position of the steel platform 11-2 and a solution supply tank 9 for a conduit 10 to pass through and then connect to a corrosion test tank 8, so as to achieve inflow and outflow of a corrosion solution. The hydraulic jack 11-1 is controlled by the master control system 7 to realize the ascending and descending of the steel platform 11-2 and the solution supply tank 9 arranged on the steel platform in the vertical direction.
The steel constant-load stress corrosion test device provided by the first aspect of the invention has the following advantages: firstly, the testing device is simple in principle and clear in stress, the steel test piece 1 and the horizontal loading reaction frame 2 are only under the action of axial tension and pressure in the testing process, and a force transmission path is clear. Secondly, the device is small in size, a plurality of longitudinal square steel tube spaces can be additionally arranged, a plurality of test groups can be tested at the same time, and the test time is saved; thirdly, the design of the L-shaped pull rod 3 and the guide sleeve 4 solves the problem that the electrified working equipment (such as the force sensor 5) cannot be directly placed into the traditional periodic infiltration corrosion test box by adopting the form that the stress loading unit and the periodic infiltration unit which work independently work cooperatively work, and can realize the real-time monitoring of the stress state of the steel test piece 1 in the test process. Fourthly, through different combination modes between the stress loading unit and the periodic infiltration unit, corrosion test researches of various types of steel can be carried out, if the periodic infiltration unit is closed after the steel test piece 1 is loaded, the corrosion test groove 8 is filled with corrosion solution, and then the steel stress corrosion test under the full-infiltration condition can be carried out; if the periodic infiltration unit is started without loading the steel test piece 1, a conventional steel corrosion test under the periodic infiltration condition can be carried out.
Furthermore, the invention optimizes the section form of the steel test piece 1, and can realize the serial loading of multiple test pieces in the corrosion test.
As shown in fig. 6, the steel material test piece 1 is an integrally formed structure formed by cutting an original steel material 1-1 to form a plurality of clamping sections 1-2 and calibration sections 1-3 which are alternately arranged, a calibration section and clamping sections at two ends of the calibration section form a small test piece 1-4, and the small test pieces in the steel material test piece 1 are connected in series. The method comprises the steps of directly loading the two ends of a steel test piece 1 in the corrosion test process and placing the steel test piece 1 into a corrosion test groove 8, taking out the steel test piece 1 after the corrosion test is finished, cutting the steel test piece 1 into a plurality of independent small test pieces 1-4 along the central line of each clamping section 1-2, and performing multiple steel material tests when the small test pieces from the same steel test piece 1 are parallel test pieces under the same test condition.
It should be noted that the number of the small test pieces 1-4 connected in series on the integrally cut steel test piece 1 may be 2, 3, 4, 5 or 6. If the number is too large, the elongation ratio of the steel material test piece 1 may become too large, and the test piece may be bent or other initial defects may occur.
The steel material test piece shown in fig. 6 has the following advantages: firstly, the corrosion test piece is integrally cut into a form that a plurality of small test pieces are connected in series, and after the test is finished, each small test piece is cut and separated. Secondly, the traditional serial loading mode needs to arrange connecting devices among the small test pieces, the test piece form provided by the invention can omit such complicated connecting devices, and the influence of corrosion of a corrosive solution on the connecting devices on test results is reduced.
The method for testing the constant-load stress corrosion of steel under the periodic infiltration condition provided by the second aspect of the invention is described below with reference to fig. 7.
As shown in FIG. 7, the test method for the constant-load stress corrosion test of steel under the periodic infiltration condition provided by the invention comprises the following test steps:
firstly, a batch of steel test pieces 1 are processed and reasonably stored, and the corrosion prevention of the test pieces in the storage process is noticed. Before the test is started, the horizontal loading reaction frame 2 and the corrosion test groove 8 are placed and positioned, the guide sleeve 4 is installed in an opening of a transverse square steel pipe 2-2 of the horizontal loading reaction frame 2, and then long-side screws 3-1 of the two L-shaped pull rods 3 penetrate through the guide sleeve 4 from the inner side of the horizontal loading reaction frame 2 and penetrate out of the horizontal loading reaction frame 2. And installing a corresponding force sensor 5 and a corresponding loading nut 6 on the outer side of the L-shaped pull rod 3 on one side, installing the loading nut 6 only on the outer side of the L-shaped pull rod 3 on the other side, adjusting the proper distance between the two L-shaped pull rods 3, sleeving round holes at two end positions of the steel test piece 1 on the short-edge end of the L-shaped pull rod 3, and screwing the test piece positioning nuts 3-4 after the steel test piece 1 is adjusted to be horizontal, so that the assembly of the stress loading unit is completed. And then screwing a loading nut 6 on one side of the force sensor 5, applying tension to the steel test piece 1, monitoring a load value in real time through the force sensor 5, and fixing the loading nut 6 to enable the steel test piece 1 to reach a constant load state after loading to a designed load. Furthermore, the periodic infiltration unit is started, the infiltration period and the drying temperature of the experimental design are set in the master control system 7, and the motor is started to enable the periodic infiltration unit to start working: in the infiltration stage, the master control system 7 controls the hydraulic lifting platform 11 to ascend, the heating lamp group 13 is closed, the corrosion solution flows into the corrosion test groove 8 from the solution supply box 9, and when the corrosion solution touches the liquid level control switch 12, the hydraulic lifting platform 11 stops ascending, so that the steel test piece 1 under the action of tensile stress is infiltrated into the corrosion solution; in the drying stage, the master control system 7 controls the hydraulic lifting platform 11 to descend to the lowest level, the heating lamp group 13 is started, the corrosion solution flows back to the solution supply box 9 from the corrosion test groove 8, the steel test piece 1 under the action of tensile stress is dried, and the heating lamp group 13 performs temperature adjustment according to the feedback of the temperature measuring sensor in the drying process. And the infiltration stage and the drying stage are circulated according to a preset infiltration period, so that the constant-load stress corrosion test of the steel test piece 1 under the periodic infiltration condition is realized.
In the test process, if a steel test piece 1 is broken, the test is stopped, the breaking time of the steel test piece 1 is recorded, and metallographic observation is carried out on the broken part. And if the steel test piece 1 is not fractured when the test is finished by the preset time, stopping the test, unloading the steel test piece 1, closing the periodic infiltration system, taking down the steel test piece 1, cutting the steel test piece 1 into a plurality of independent small test pieces along the central line of each clamping section, performing different material performance tests on the small test pieces from the same steel test piece 1, and testing the material performance change of the steel after stress corrosion.
The steel constant-load stress corrosion test method under the periodic infiltration condition provided by the invention has the following advantages: the constant load stress corrosion test of steel and the periodic infiltration corrosion test of steel are combined, so that the corrosion environment of a steel structure under the action of constant tensile stress working in the environment of a sea splash zone can be well simulated, and the research on the stress corrosion rule of steel has practical significance.
The following describes a constant-load stress corrosion test device for steel under periodic infiltration conditions, by using a specific example, which is as follows:
one embodiment of the present invention is a constant load stress corrosion test study performed under periodic infiltration conditions of 316L stainless steel. The steel material test piece 1 is made of 316L stainless steel, the length of each small test piece is 160mm, the length of each calibration section is 24mm, the width of each calibration section is 6mm, and the thickness of each test piece is 3 mm. A steel test piece 1 is processed in a mode that 3 small test pieces are connected in series, the total length of the steel test piece 1 is 480mm, and the hole diameters of holes formed in two ends are 10 mm. The L-shaped pull rod 3 is also made of 316L stainless steel, the rod diameter of the long screw rod 3-1 is 16mm, the diameter of the solid steel rod 3-2 is 20mm, and the diameter is reduced to 10mm after passing through a section of variable cross section. Longitudinal and transverse square steel pipes 3-1 and 3-2 of the horizontal loading reaction frame 2 are welded by Q345 square steel pipes of 80mm multiplied by 60mm, the aperture of an opening on the transverse square steel pipe 3-2 is 24mm, namely the outer diameter of the guide sleeve 4 is 24mm, and the inner diameter of the guide sleeve is 16 mm. The corrosion test tank 8 and the solution supply tank are both made of 304 stainless steel and are connected by a rubber conduit 10. The maximum bearing capacity of the hydraulic jack 11-1 is selected to be 5t, and stable bearing for a long time can be realized. The heating lamp set 13 is provided with 10 heating bulbs, and the temperature can reach 80 ℃ after the heating lamp set is fully opened.
The dry-wet cycle period of the periodic infiltration test is set to be 10 minutes of infiltration and 50 minutes of drying in each hour, and the ambient temperature of the drying stage is set to be 70 ℃. The load applied to the steel test piece 1 is set as a tensile value when the cross section of the calibration section reaches 50% of the yield strength, namely 2.4kN, and under the action of the load, the cross section stress of the horizontal loading reaction frame 2 and the L-shaped pull rod 3 is small, and the horizontal loading reaction frame and the L-shaped pull rod can be regarded as rigid bodies. When the periodic infiltration unit works, the rising time and the falling time of the hydraulic lifting platform 11 are controlled within 2min, namely, the steel test piece 1 can finish alternation between infiltration and drying within 2 min.
The results of the embodiment show that the invention has smart design and simple and convenient operation, and is suitable for the stress corrosion test research of steel products under the periodic infiltration condition.
Claims (10)
1. A steel constant load stress corrosion test device under a periodic infiltration condition is characterized by comprising a periodic infiltration unit and at least one stress loading unit;
each stress loading unit comprises a steel test piece, a horizontal loading reaction frame, a force sensor, an L-shaped pull rod, a guide sleeve and two loading nuts; the short-edge ends of the two L-shaped pull rods respectively hook one end of the steel test piece, the long edges of the two L-shaped pull rods respectively penetrate through the corresponding sides of the horizontal loading reaction frame through the guide sleeves arranged in the horizontal loading reaction frame, the L-shaped pull rods on one side are sequentially sleeved with the force sensor and one loading nut after penetrating out of the horizontal loading reaction frame, and the L-shaped pull rods on the other side are sleeved with the other loading nut and fix the positions of the loading nuts; the loading nut on one side of the force sensor is screwed and fixed to load the steel test piece under constant tensile stress, and the load is read by the force sensor;
the periodic infiltration unit comprises a master control system, a solution supply box containing a corrosion solution, a hydraulic lifting table, corrosion test grooves, a liquid level control switch, a heating lamp group and temperature measurement sensors, wherein the number of the corrosion test grooves is the same as that of the stress loading units; each heating lamp group is respectively arranged above one corresponding horizontal loading reaction frame, each steel test piece after being loaded is respectively suspended in one corresponding corrosion test groove, each corrosion test groove is respectively communicated with the solution supply box through a guide pipe, the solution supply box is placed on the hydraulic lifting table, the hydraulic lifting table is controlled by the master control system to periodically lift and lower, and the heating lamp groups are periodically switched off and switched on, so that the corrosion solution periodically flows into and flows out of the corrosion test grooves, and the periodic circulation of the steel test pieces between corrosion solution infiltration and high-temperature drying is realized; each liquid level control switch is arranged on the inner wall of one corresponding corrosion test groove, and the liquid level height of the corrosion solution in the corrosion test groove is monitored and fed back to the master control system; the temperature sensor is arranged above the corrosion test groove, monitors the environmental temperature after the heating lamp set is started and feeds back the environmental temperature to the master control system.
2. The steel constant-load stress corrosion test device under the periodic infiltration condition according to claim 1, wherein the steel test piece is a thin plate-shaped or rod-shaped test piece, and round holes are formed at two end heads of the steel test piece for the short-side end heads of the L-shaped pull rods to pass through and hook the steel test piece.
3. The steel constant-load stress corrosion test device under the periodic infiltration condition according to claim 1, wherein the main body of the horizontal loading reaction frame is a rectangular frame structure formed by welding two transverse square steel tubes and two longitudinal square steel tubes, foot supports are welded at four corner positions of the rectangular frame, the rectangular frame is lifted to a position slightly higher than the corrosion test groove, and a round hole is formed in the middle position of the two transverse square steel tubes and used for placing the guide sleeve.
4. The steel constant-load stress corrosion test device under the periodic infiltration condition according to claim 1, wherein the long side of the L-shaped pull rod is a long screw rod, and the short side of the L-shaped pull rod is a solid steel bar; one end of the solid steel bar is welded and fixed with the long screw, and a stiffening rib plate is arranged; the other end of the solid steel bar is reduced in rod diameter through a variable cross-section until the diameter of the other end of the solid steel bar is the same as the diameter of the round holes formed in the two ends of the steel test piece; the lower end of the small rod diameter section of the solid steel rod is engraved with threads and used for placing a test piece positioning nut during the steel test piece tensioning, and the steel test piece is horizontally placed and prevented from falling in the test process.
5. The steel constant-load stress corrosion test device under the periodic infiltration condition according to claim 1, wherein the guide sleeve is fixed in the transverse square steel tube of the horizontal loading reaction frame, the outer diameter of the guide sleeve is the same as the aperture of a round hole formed in the middle point of the transverse square steel tube of the horizontal loading reaction frame, and the inner diameter of the guide sleeve is the same as the rod diameter of the long side of the L-shaped pull rod; the guide sleeve ensures that the L-shaped pull rods only horizontally displace in the loading process.
6. The steel constant-load stress corrosion test device under the periodic infiltration condition according to claim 1, wherein the hydraulic lifting platform comprises a hydraulic jack, a steel platform, and a guide rail and a pulley which are matched with each other, the hydraulic jack is placed at the central position below the steel platform, the pulley is respectively arranged at the four corner positions of the steel platform and is clamped with the corresponding guide rail, and a round hole is formed at the corresponding position of the steel platform and the solution supply tank and is used for penetrating through the conduit to realize the inflow and outflow of corrosive solution; the hydraulic jack is controlled by the master control system to realize the ascending and descending of the steel platform and the solution supply tank arranged on the steel platform in the vertical direction.
7. The steel constant-load stress corrosion test device under the periodic infiltration condition according to claim 1, wherein the heating lamp set comprises a plurality of heating bulbs, and the number of the heating bulbs started in the heating lamp set is controlled by monitoring the ambient temperature through the temperature measuring sensor and feeding back the ambient temperature to the master control system; when the monitoring temperature is higher, part of the heating bulbs in the heating lamp group are closed, and when the monitoring temperature is lower, more heating bulbs in the heating lamp group are opened, so that stable temperature control in the test process is realized.
8. The steel constant-load stress corrosion test device under the periodic infiltration condition according to any one of claims 1 to 7, wherein the steel test piece is an integrally formed structure formed by cutting an original steel to form a plurality of clamping sections and calibration sections which are alternately arranged, one calibration section and the clamping sections at two ends of the calibration section form a small test piece, and the small test pieces in the steel test piece are connected in series.
9. The steel constant-load stress corrosion test device under the periodic infiltration condition according to claim 8, wherein the number of the small test pieces in the steel test piece is 2-6.
10. The test method of the steel constant-load stress corrosion test device under the periodic infiltration condition according to claim 8, characterized by comprising the following steps of:
assembling the device: after the horizontal loading reaction frame, the corrosion test groove, the solution supply box and the heating lamp group are placed and positioned, the height of the hydraulic lifting table is adjusted, so that no corrosion solution exists in the corrosion test groove, and the heating lamp group is in a closed state; installing the guide sleeves, and enabling long edges of the two L-shaped pull rods to penetrate through the corresponding guide sleeves from the inner side of the horizontal loading reaction frame and penetrate out of the horizontal loading reaction frame; installing the corresponding force sensor and the corresponding loading nut on the outer side of one L-shaped pull rod, and after adjusting the distance between the two L-shaped pull rods, sleeving round holes at two end positions of the steel test piece on the short edge ends of the two L-shaped pull rods, and fixing the steel test piece with the short edge ends of the two L-shaped pull rods after adjusting the steel test piece to be horizontal;
loading: keeping the height of the hydraulic lifting platform unchanged and keeping the heating lamp group switched off; screwing the loading nut on one side provided with the force sensor, applying tension to the steel test piece, monitoring a load value in real time through the force sensor, and fixing the loading nut on one side provided with the force sensor after loading to a designed load to enable the steel test piece to reach a constant load state;
periodic infiltration test: setting the infiltration period and the drying temperature of the test design in the master control system; wherein, the infiltration stage: the master control system controls the hydraulic lifting platform to ascend and the heating lamp set to be closed, corrosive solution flows into the corrosion test groove from the solution supply box, and the hydraulic lifting platform stops ascending when the corrosive solution touches the liquid level control switch, so that the steel test piece under the action of tensile stress is soaked in the corrosive solution; and (3) a drying stage: the master control system controls the hydraulic lifting platform to descend to the lowest level and the heating lamp group to be started, corrosive solution flows back to the solution supply box from the corrosion test groove, the steel test piece under the action of tensile stress is dried, and the heating lamp group performs temperature adjustment according to the feedback of the temperature measuring sensor in the drying process; and the infiltration stage and the drying stage are circulated according to a preset infiltration period, so that the constant-load stress corrosion test of the steel test piece under the periodic infiltration condition is realized.
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