CN115758665A - Method for simulating flash butt welding by adopting thermal simulation testing machine - Google Patents
Method for simulating flash butt welding by adopting thermal simulation testing machine Download PDFInfo
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- CN115758665A CN115758665A CN202211274315.6A CN202211274315A CN115758665A CN 115758665 A CN115758665 A CN 115758665A CN 202211274315 A CN202211274315 A CN 202211274315A CN 115758665 A CN115758665 A CN 115758665A
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Abstract
The invention discloses a method for simulating flash butt welding by adopting a thermal simulation testing machine, which comprises the following steps: 1) Processing and preparing a sample for a thermal simulation test; 2) Welding a thermocouple on a sample; 3) The test parameters comprise flash allowance, flash speed, upset allowance and upset speed, and a welding heat simulation curve in the actual flash butt welding process is taken as a heating system; 4) According to the temperature and the stress measured by the welding thermal simulation, obtaining a temperature-time curve and a stress-time curve of the sample under the simulation condition; 5) And carrying out tissue and performance tests on the simulated samples, and determining the relationship between the process parameters and the performance results. The method simulates the flash butt welding process of the steel plate by adopting various key process parameters in the actual flash butt welding process on a thermophysical simulation experiment machine; the influence of various key process parameters in the actual flash butt welding process on the welding quality can be evaluated, and technical support is provided for simulation of the flash butt welding process.
Description
Technical Field
The invention belongs to the technical field of metal welding, and particularly relates to a method for simulating flash butt welding by using a thermal simulation testing machine.
Background
The wheel mainly comprises a rim and a spoke, wherein the rim is a non-bearing part rotating at high speed and is an important component of the wheel, and the rim and a tire jointly support and buffer the force transmitted on the ground, so the performance of the whole wheel is determined by the performance of the rim to a great extent, and the quality of the rim has great influence on the stability and the safety of a vehicle body in the running process. The flash butt welding process has the characteristics of high welding efficiency, good forming, low cost and the like, and becomes a main method for producing the rim. Combining research and development and production conditions, because the post-welding rim undergoes subsequent processing, including: in the processes of flaring, roll forming, bulging and the like, if the key processes in the flash butt welding process have problems, mainly the flash and top forging processes, the welded joint is easy to have microcracks and even cracking in the whole subsequent processing process. The problems caused during the welding process are more serious as the strength grade of the steel for wheels is improved.
Flash butt welding is a resistance butt welding method, in which resistance heat generated by current passing through workpiece and end face is used as heat source to assemble the workpiece into butt joint mode, and the whole end face is quickly connected under the combined action of heat, electricity and mechanical force. In the flash butt welding process, after two end faces of a workpiece to be welded are contacted, resistance heat is generated under the action of current, and a contact point of the metal end face is quickly burnt to form flash. The flashing process is terminated when a plastic layer of appropriate depth is formed across the joint. Then, the upsetting force is applied rapidly to extrude out liquid metal and other inclusions between the metal end faces, and high-temperature metal at the interface forms common connection to complete the whole welding process.
At present, a method is not disclosed, which can systematically and inexpensively embody various key parameters in the actual flash butt welding process in the welding thermal simulation process.
Chinese patent application No. CN113165101A discloses "a flash butt welding member and a flash butt welding method having excellent formability of a rim weld", which improve weld strength and formability of a high-strength hot-rolled steel material having a tensile strength of 780MPa or more and a steel thickness of 6mm or less, which is applied to an automobile light steel wheel or the like. The method aims to research how to improve the structure and the performance of the flash butt welding joint in a simulation mode in the actual engineering application process and effectively improve the strength and the formability of a welding part; however, the method does not provide a systematic and low-cost thermal simulation method for various key parameters in the actual flash butt welding process.
Disclosure of Invention
The invention aims to provide a method for simulating flash butt welding by adopting a thermal simulation testing machine, which carries out thermal simulation in a systematic and low-cost way.
In order to solve the technical problem, the technical scheme adopted by the invention comprises the following steps: 1) Processing and preparing a sample for a thermal simulation test;
2) Welding a thermocouple on a sample;
3) The test parameters comprise flash allowance, flash speed, upset allowance and upset speed, and a welding heat simulation curve in the actual flash butt welding process is taken as a heating system;
4) According to the temperature and the stress measured by the welding thermal simulation, obtaining a temperature-time curve and a stress-time curve of the sample under the simulation condition;
5) And carrying out tissue and performance tests on the simulated samples, and determining the relationship between the process parameters and the performance results.
In the step 1), the thickness of the sample is larger than the thickness of the notch of the thermal simulation experiment fixture, a gap which is not smaller than 0.5mm is ensured to be left after the two fixtures are assembled, the width of the sample is 5-15 mm, and the length of the sample is not more than 3.5 times of the equivalent circle diameter of the sectional area.
In the step 2), the distance between the welding point of the thermocouple and the top end of the sample is 10mm.
In the step 3), the welding thermal simulation curve comprises the processes of heating, heat preservation and cooling.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: the method can simulate the flash butt welding process of steel plates, especially steel plates for wheels on a thermophysical simulation experiment machine by adopting various key process parameters in the actual flash butt welding process; in the welding heat simulation process, recording temperature-time and stress-time curves in the welding simulation process through a thermocouple and a stress sensor; meanwhile, the influence of various key process parameters in the actual flash butt welding process on the process is accurately mastered by representing the structure and the performance of the sample after the welding heat simulation process. The invention can evaluate the influence of each key process parameter in the actual flash butt welding process on the welding quality, and can provide technical support for the simulation of the flash butt welding process.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a schematic structural view of the relationship between the thickness of a test piece according to the present invention and the thickness of a notch of a jig;
FIG. 2 is a photograph of a thermocouple welding site according to the present invention;
FIG. 3 is a graph of a weld heat simulation during an actual flash butt weld;
FIG. 4 is a graph of thermal cycling during a thermal simulation for determining a weld based on a change in flash hold;
FIG. 5 is a graph of stress versus time during flash butt welding;
FIG. 6 is a photograph of a joint specimen after a flash butt welding simulation;
FIG. 7 is an interface diagram of the thermal simulation tester Quiksim software;
FIG. 8 is a heat affected zone of each sample of the examples;
FIG. 9 is a graph of flash hold versus heat affected zone width for an embodiment;
FIG. 10 is a graph of the flash retention vs. hardness profile for the examples;
FIG. 11 is a graph of flash retention versus intensity for an example.
Detailed Description
The thermophysical simulation experiment machine (thermal simulation test machine) can simulate the thermal deformation behavior of the material and accurately reproduce the thermal processing phenomenon of the material. Specifically, different temperatures and deformation rates can be set in the simulation process, and the lifting temperature and the deformation degree of different rates are controlled; meanwhile, recording the relation between the temperature, stress and other key process parameters and time in the whole test process. In the process of simulating flash butt welding, the process of quickly heating and simulating welding and the process of applying pressure are provided, and in addition, the quick deformation rate is also necessary in the process of flash butt welding. Therefore, it is effective to study the flash butt welding process of steel for wheels by using a low-cost and effective method, i.e., a thermal physical simulation method.
The method for simulating flash butt welding by adopting the thermal simulation testing machine comprises the following steps: 1) Processing and preparing a sample for a thermal simulation test; as shown in fig. 1, the thickness of the sample is greater than the notch thickness of the thermal simulation experiment fixture, and a gap not less than 0.5mm is ensured to be left after the upper fixture and the lower fixture are assembled, the width of the sample is 5-15 mm, and the length of the sample is not more than 3.5 times of the equivalent circle diameter of the cross-sectional area; the surface roughness of the sample was less than 0.8 μm.
2) Selecting a proper thermocouple, selecting an R-type thermocouple if the test temperature is more than or equal to 1350 ℃, and selecting a K-type thermocouple otherwise; as shown in fig. 2, a thermocouple is welded on a sample by adopting a spot welding method, and the welding position of the thermocouple is located at a position 10mm away from the top end of the sample; after the thermocouple is spot-welded, checking welding spots and confirming that the welding spots are good in quality; the thermocouple can accurately measure the temperature change of the sample in the whole simulation process.
3) Inputting parameters on an interface of a thermal simulation testing machine Quiksim software to compile a related thermal simulation system, setting required testing parameters, and performing a welding thermal simulation test as shown in figure 7; the test parameters comprise flash allowance, flash speed, upset allowance and upset speed, the related thermal simulation system takes a welding thermal simulation curve in the actual flash butt welding process as a heating system, and the welding thermal simulation curve comprises the processes of temperature rise, heat preservation and temperature reduction, as shown in FIG. 3. Fig. 7 shows the set test parameters for a certain test, and it can be seen that the set test parameters are: 5s to 30 degrees; 5.6s, raising the temperature to 1150 ℃, namely, heating the temperature to 200 ℃ per second; the flash retention is 6mm, and the flash speed is 5mm/s; the top end allowance is 6.5mm, and the top end speed is 10mm/s; and then cooled from 1150 degrees to 30 degrees in 10 seconds.
4) Performing welding thermal simulation according to the thermophysical simulation testing machine to obtain the temperature of the outer surface of the sample under the simulation condition and a set temperature and welding thermal simulation curve (temperature rise, heat preservation and temperature reduction); and meanwhile, according to a temperature change curve determined by a test, checking the difference between a thermal cycle curve in a welding thermal simulation process and an actual flash butt welding process, mainly performing the processes of temperature rise, heat preservation, temperature reduction and the like, and adjusting and optimizing.
5) Measuring and collecting temperature-time and stress-time curves simulating a flash butt welding process by using a thermocouple and a pressure sensor in a thermal simulation testing machine; therefore, the change of the temperature and the stress of a certain process parameter along with the change of time can be accurately mastered in the simulation process.
6) Testing the structure and performance of the simulated sample, and researching the influence of key process parameters in the flash butt welding process on the microstructure and typical mechanical property of the sample through the welding heat simulation process; the main technological parameters comprise flash allowance, and other three key technological parameters are fixed, namely flash speed, upsetting allowance, upsetting speed, technological parameters in heating, heat preservation and cooling processes and the like.
Example (b): the method for simulating flash butt welding by using the thermal simulation testing machine is specifically described as follows.
1) Processing and preparing 5 samples for thermal simulation test, wherein the samples are respectively #1 to #5; as shown in fig. 1, the thickness of the sample is greater than the notch thickness of the thermal simulation experiment fixture, a gap of 0.5mm is left after the upper fixture and the lower fixture are assembled, the width of the sample is 10mm, and the length of the sample is 3.5 times of the equivalent circle diameter of the cross-sectional area; the surface roughness of the sample was 0.8. Mu.m.
2) Selecting a K-type thermocouple because the test temperature is less than 1350 ℃; as shown in fig. 2, a thermocouple is welded on a sample by adopting a spot welding method, and the welding position of the thermocouple is located at a position 10mm away from the top end of the sample; after spot welding of the thermocouple, the welding spot was checked to confirm that the welding spot was of good quality.
3) Inputting parameters on an interface of a thermal simulation testing machine Quiksim software to compile a related thermal simulation system, setting required test parameters, and performing a welding thermal simulation test; 5 samples respectively adopt different flash reserves, and other three key process parameters, namely flash speed, upsetting reserve and upsetting speed, are fixed; see table 1 for details.
Table 1: process parameter setting
Taking a welding heat simulation curve in the actual flash butt welding process as a heating system, as shown in FIG. 3, a welding heat simulation curve with a flash allowance of 12mm in the actual flash butt welding process; in FIG. 3, TC is an abbreviation of Thermal couple, and TC1-TC6 represent temperature cycling curves tested by different thermocouples respectively.
4) Carrying out welding heat simulation on the set temperature and a welding heat simulation curve (heating, heat preservation and cooling) according to the thermophysical simulation testing machine to obtain the temperature of the outer surface of the sample under the simulation condition; meanwhile, according to the temperature change curve determined by the test, the difference between the thermal cycle curve of the welding thermal simulation process and the actual flash butt welding process is checked, mainly in the processes of temperature rise, heat preservation, temperature reduction and the like, and adjustment and optimization are carried out.
5) The temperature-time curve of 5 samples is shown in figure 4 by measuring and collecting the temperature-time of the simulated flash butt welding process in a thermal simulation testing machine by adopting a thermocouple; the stress-time curves for the simulated flash butt welding process were measured and collected by the pressure sensor, and the stress-time curves for the 5 samples are shown in fig. 5.
6) A photograph of the joint sample after the flash butt welding simulation is shown in fig. 6; and testing the structure and the performance of the simulated sample, and researching the influence of key process parameters in the flash butt welding process on the microstructure and the typical mechanical property of the sample through the welding heat simulation process. As can be seen from FIG. 6, the process parameters of #1 to # 4 are satisfactory, but the joint of #5 is too deformed due to excessive upset allowance, which is not desirable. As can be seen from fig. 8 and 9, as the flash light retention increases, the heat input increases; the distribution of hardness in the heat affected zone decreases with the increase of the flash retention, as shown in fig. 10; in the tensile properties, both the yield strength and the tensile strength decreased with the increase in the amount of flash retention, as shown in fig. 11. As can be seen from the above, the test determined that the value range of the flash reserve is 6mm to 12mm in the flash butt welding process, and the heat input amount increases with the increase of the flash reserve.
Claims (4)
1. A method for simulating flash butt welding by using a thermal simulation testing machine is characterized by comprising the following steps: 1) Processing and preparing a sample for a thermal simulation test;
2) Welding a thermocouple on a sample;
3) The test parameters comprise flash allowance, flash speed, upset allowance and upset speed, and a welding heat simulation curve in the actual flash butt welding process is taken as a heating system;
4) According to the temperature and the stress measured by the welding thermal simulation, obtaining a temperature-time curve and a stress-time curve of the sample under the simulation condition;
5) And carrying out tissue and performance tests on the simulated samples, and determining the relationship between the process parameters and the performance results.
2. The method of claim 1 for flash butt welding simulation using a thermal simulation tester, wherein: in the step 1), the thickness of the sample is larger than the thickness of the notch of the thermal simulation experiment fixture, a gap which is not smaller than 0.5mm is ensured to be left after the two fixtures are assembled, the width of the sample is 5-15 mm, and the length of the sample is not more than 3.5 times of the equivalent circle diameter of the sectional area.
3. The method of claim 1 for flash butt welding simulation using a thermal simulation tester, wherein: in the step 2), the distance between the welding point of the thermocouple and the top end of the sample is 10mm.
4. A method of flash butt welding simulation using a thermal simulation tester according to claim 1, 2 or 3, characterized in that: in the step 3), the welding thermal simulation curve comprises heating, heat preservation and cooling processes.
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