Titanium U-shaped heat exchange tube heat treatment method

Abstract

The invention discloses a heat treatment method for a titanium U-shaped heat exchange tube. The heat treatment method comprises the following steps that S1, a first heat exchange tube is bent and formed, and the minimum bending radius of the first heat exchange tube is 50 mm; s2, dirt and rust on the surface of the first heat exchange tube are removed, and iron ion detection is conducted on the surface of the first heat exchange tube; s3, the two vertical parts of the first heat exchange tube are clamped on the positive electrode and the negative electrode of the medium-frequency induction heating furnace correspondingly; s4, covering the bent pipe part of the first heat exchange pipe with a protective gas hood, continuously introducing argon through one port of the first heat exchange pipe, and continuously introducing argon into the protective gas hood; s5, controlling the medium-frequency induction heating furnace to heat to 560 + / -10 DEG C at the heating rate of 50 DEG C per second; the invention can solve the problems of low temperature rise speed, incapability of accurately controlling the heat treatment temperature, incapability of completely replacing air in the furnace, low efficiency and the like when a box-type resistance heat treatment furnace is used for heat treatment of the heat exchange tube.

Description

Technical Field

[0001] The invention relates to the field of heat exchangers, and in particular to a heat treatment method for a titanium U-shaped heat exchange tube. Background Art

[0002] Shell and tube heat exchangers are widely used in the fields of petrochemical, biomedicine, thermal power generation, etc. U-tube heat exchanger is a type of shell and tube heat exchanger. Its characteristics are that the tube bundle can be freely expanded and contracted, and no thermal stress will be generated due to the temperature difference between the tube and shell, and the thermal compensation performance is good; the tube bundle can be pulled out from the shell, which is convenient for maintenance and cleaning; but it is inconvenient to clean the tube, and the heat exchange tube in the middle of the tube bundle is difficult to replace after it is damaged, resulting in a decrease in heat exchange effect and energy loss.

[0003] For titanium U-shaped heat exchangers, the national standard NB / T 11270-2023 "Titanium Pressure Vessels" stipulates that for workpieces formed by room temperature forming or room temperature preforming followed by heat correction, when the TA2 deformation rate exceeds 3.0%, a recovery performance heat treatment is required after the titanium tube is formed. The ф19.05*1.245t heat exchange tube is bent into a U-shaped tube with R=50mm. The deformation rate of the titanium tube after bending is = 100×9.525 / 59.525=15.89%, which is much higher than the 3% deformation rate required by the standard. After forming, a recovery performance heat treatment is required. At present, the common practice is to use a box-type resistance heat treatment furnace to perform a recovery performance heat treatment on the bent part. However, the use of a box-type resistance heat treatment furnace for heat treatment has the problem of a relatively slow heating rate, which causes the heat exchange tube to stay in the high temperature area for too long, and there are problems such as the inability to accurately control the heat treatment temperature, the inability to completely replace the air in the furnace, and low efficiency. Summary of the invention In order to overcome the above disadvantages, the object of the present invention is to provide a heat treatment method for a titanium U-shaped heat exchange tube.

[0004] In order to achieve the above objectives, the technical solution adopted by the present invention is used to restore the performance of the first heat exchange tube after the U-bend, including the following steps: S1: bending the first heat exchange tube into shape, wherein the minimum bending radius of the first heat exchange tube is 50 mm; S2: removing stains and rust from the surface of the first heat exchange tube and performing iron ion detection on the surface of the first heat exchange tube; S3: clamping the two vertical parts of the first heat exchange tube on the positive and negative electrodes of the medium frequency induction heating furnace respectively; S4: placing a protective gas hood on the curved portion of the first heat exchange tube, continuously introducing argon gas through a port of the first heat exchange tube, and continuously introducing argon gas into the protective gas hood; S5: Control the medium frequency induction heating furnace to heat to 560°C ± 10°C at a heating rate of 50°C per second.

[0005] In the preferred technical solution of the above-mentioned titanium U-shaped heat exchange tube heat treatment method, the heat treatment method further comprises: S6: After heating the first heat exchange tube to 560° C.±10° C., stop heating the first heat exchange tube and allow the first heat exchange tube to cool naturally.

[0006] In the preferred technical solution of the above-mentioned titanium U-shaped heat exchange tube heat treatment method, in S2, the solvent for removing stains and rust on the surface of the first heat exchange tube is acetone or ethanol.

[0007] In the preferred technical scheme of the above-mentioned titanium U-shaped heat exchange tube heat treatment method, in S2, the reagent for detecting iron ions on the surface of the first heat exchange tube is prepared by dissolving 7g of potassium ferrocyanide and 4.5ml of 65% nitric acid in 214ml of distilled water or deionized water.

[0008] In the preferred technical solution of the above-mentioned titanium U-shaped heat exchange tube heat treatment method, in S4, the purity of the argon gas introduced into the first heat exchange tube and into the protective gas hood is 99.99%.

[0009] In the preferred technical solution of the above-mentioned titanium U-shaped heat exchange tube heat treatment method, in S4, the argon gas flow rate continuously introduced into the first heat exchange tube is 15 L / min, and the argon gas flow rate continuously introduced into the protective gas hood is 25 L / min.

[0010] In the preferred technical solution of the heat treatment method for the titanium U-shaped heat exchange tube, in S6, when the first heat exchange tube is naturally cooled, argon gas is still introduced into the first heat exchange tube and the protective gas hood.

[0011] The beneficial effect of the present invention is that the present application utilizes a medium frequency induction heating furnace to perform electromagnetic heating on the bent portion of the first heat exchange tube, which has the characteristics of fast heating and high heat treatment efficiency. Before and after the heat treatment of the first heat exchange tube, argon gas needs to be introduced into the first heat exchange tube and into the protective gas hood that covers the first heat exchange tube, so as to expel the air around the bent portion of the first heat exchange tube in turn, thereby avoiding the problem of oxidation of the bent portion of the first heat exchange tube during heat treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a flow chart of the heat treatment method of titanium U-shaped heat exchange tube; Figure 2 is the metallographic diagram of the first heat exchange tube; Figure 3 is the metallographic diagram of the second heat exchange tube; Figure 4 This is the metallographic diagram of the third heat exchange tube. DETAILED DESCRIPTION

[0013] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0014] It should be noted that in the description of the present invention, the terms "upper", "lower", "left", "right", "front", "rear" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are only for the convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0015] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "disposed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0016] Embodiment 1: like Figures 1 to 4 As shown, the heat treatment method of the titanium U-shaped heat exchange tube of the present invention is used to restore the performance of the first heat exchange tube after the U-shaped bend, and comprises the following steps: S1: bending the first heat exchange tube, the minimum bending radius of the first heat exchange tube is 50 mm; See also Figure 1 After the first heat exchange tube is bent and formed, the first heat exchange tube has a first vertical portion, a bent portion and a second vertical portion that are connected to each other. According to the GB151 heat exchanger composition standard, the minimum bending radius of the bent portion is 50 mm. In this application, only the bending radius of the bent portion of 50 mm is used as an exemplary explanation. Specifically, the bending radius of the bent portion can also be 100 mm, 150 mm, or 200 mm. There is no specific limitation. It is only necessary to adopt the heat treatment method of this application to heat treat the first heat exchange tube.

[0017] S2: removing stains and rust from the surface of the first heat exchange tube and performing iron ion detection on the surface of the first heat exchange tube; the solvent for removing stains and rust from the surface of the first heat exchange tube is acetone or ethanol; the reagent for detecting iron ions on the surface of the first heat exchange tube is prepared by dissolving 7g of potassium ferrocyanide and 4.5ml of 65% nitric acid in 214ml of distilled water or deionized water; See also Figure 1Before heat treating the first heat exchange tube, the first heat exchange tube needs to be pre-treated, that is, the first heat exchange tube needs to be decontaminated and derusted to reduce the problem that the first heat exchange tube is easily oxidized when heated and affects the performance of the first heat exchange tube.

[0018] It should be noted that when removing water, oil and rust from the bent part of the first heat exchange tube and the first vertical part and the second vertical part near the bent part, the solvent used is acetone or ethanol. Specifically, the bent part of the first heat exchange tube can be repeatedly wiped with a decontamination cloth dipped in acetone or ethanol solvent. After wiping, the bent part of the first heat exchange tube can be wiped a second time with a clean decontamination cloth dipped in acetone or ethanol solvent, thereby improving the wiping effect on the surface of the first heat exchange tube and ensuring the surface cleanliness of the first heat exchange tube.

[0019] After the surface cleaning of the bent portion of the first heat exchange tube is completed, it is necessary to perform iron ion detection on the bent portion of the first heat exchange tube to confirm whether the bent portion of the first heat exchange tube is clean. The iron ion detection reagent is prepared by dissolving 7g of potassium ferrocyanide and 4.5ml of 65% nitric acid solution in 214ml of distilled water or deionized water. When performing iron ion detection on the bent part of the titanium first heat exchange tube, first dip the test paper into the above-mentioned iron ion detection reagent, and then attach the test paper with the part dipped in the iron ion detection reagent to the bent part of the first heat exchange tube. When blue dots appear on the test paper, it can be confirmed that there are iron ions in the bent part of the first heat exchange tube, and the bent part of the first heat exchange tube needs to be wiped and cleaned again. When no blue dots appear on the test paper, it can be confirmed that there are no iron ions on the surface of the first heat exchange tube. The present application can effectively ensure that the bent part of the first heat exchange tube will not be oxidized during the heat treatment by cleaning the bent part and performing iron ion detection before heat treating the bent part of the first heat exchange tube, thereby ensuring the heat treatment effect of the present application on the bent part of the first heat exchange tube, so that after the first heat exchange tube is bent and formed, its performance can maintain a high consistency with the performance before bending, and has practicality.

[0020] S3: clamping the two vertical parts of the first heat exchange tube on the positive and negative electrodes of the medium frequency induction heating furnace respectively; It should be noted that when the medium frequency induction heating furnace utilizes electromagnetic induction to heat the first heat exchange tube, it is necessary to place the first vertical portion and the second vertical portion of the first heat exchange tube on the positive and negative poles of the medium frequency induction heating furnace respectively and use the downward pressure structure to press the first vertical portion and the second vertical portion. Through this arrangement, it is possible to ensure that the first heat exchange tube can maintain a relatively fixed position during the heating process of the medium frequency induction heating furnace, ensure the uniformity of heating the bent portion of the first heat exchange tube by the medium frequency induction heating furnace, and improve the quality of the bent portion of the first heat exchange tube after heat treatment and forming.

[0021] S4: a protective gas hood is arranged at the curved part of the first heat exchange tube, argon gas is continuously introduced through one end of the first heat exchange tube, and argon gas is continuously introduced into the protective gas hood; the purity of the argon gas introduced into the first heat exchange tube and the protective gas hood is 99.99%; the flow rate of the argon gas continuously introduced into the first heat exchange tube is 15 L / min, and the flow rate of the argon gas continuously introduced into the protective gas hood is 25 L / min; It can be understood that the protective gas hood is roughly U-shaped, and a accommodating cavity is provided on the top or bottom surface of the protective gas hood. When the protective gas hood is arranged on the bent portion of the first heat exchange tube, the bent portion of the first heat exchange tube is located in the accommodating cavity of the protective gas hood; an air inlet is provided at the tail end of the protective gas hood, and the top of the protective gas hood is the opening of the accommodating cavity. Before the intermediate frequency induction heating furnace heats the bent portion of the first heat exchange tube, argon gas with a purity of 99.99% needs to be introduced into the accommodating space through the air inlet of the protective gas hood to expel oxygen and Other gases can prevent the bent portion of the first heat exchange tube from being oxidized and inhibit grain growth when the bent portion is heat treated, thereby ensuring that the bent portion of the first heat exchange tube can be restored to the state before the first heat exchange tube is bent after the heat treatment, thereby maintaining good performance of the first heat exchange tube. In addition, argon gas is introduced into the containing space of the protective gas hood from the air inlet, which can prevent other impurities from entering the containing space of the protective gas hood again when the bent portion of the first heat exchange tube is heat treated, thereby further ensuring the performance of the bent portion after the heat treatment.

[0022] Before the bent portion of the first heat exchange tube is heat treated, argon gas with a purity of 99.99% needs to be introduced through the port of the first vertical portion of the first heat exchange tube and discharged through the port of the second vertical portion. The argon gas can expel oxygen and other gases inside the first heat exchange tube, thereby further avoiding the bending of the bent portion of the first heat exchange tube when the bent portion of the first heat exchange tube is heat treated, thereby improving the performance of the first heat exchange tube after heat treatment. It should be noted that when the argon gas input device is connected to the port of the first vertical portion of the first heat exchange tube, a hose connection can be used to insert it into the port of the first vertical portion, and the connection between the hose and the port of the first vertical portion can be sealed with sealing tape. Through this arrangement, other gases can be further avoided from entering the first heat exchange tube and affecting the heat treatment of the first heat exchange tube.

[0023] It should be noted that the argon flow rate entering the first heat exchange tube is 15L / min, and the argon flow rate entering the protective gas hood is 25L / min. In other possible embodiments, the argon flow rate entering the first heat exchange tube can be 14L / min, 14.5L / min, 15.5L / min, 16L / min; the argon flow rate entering the protective gas hood can be 24L / min, 24.5L / min, 25.5L / min, 26L / min. It is understandable that the argon flow rate entering the first heat exchange tube and the argon flow rate entering the protective gas hood can be selected according to actual production needs.

[0024] S5: Control the medium frequency induction heating furnace to heat to 560℃±10℃ at a heating rate of 50℃ per second; It can be understood that the time required for the medium frequency induction heating furnace to heat the bent part of the first heat exchange tube to 550℃-560℃ at 50℃ per second is 11-12s; when the medium frequency induction heating furnace completes heating the bent part of the first heat exchange tube, the heating of the first heat exchange tube can be stopped immediately.

[0025] S6: After heating the first heat exchange tube to 560°C±10°C, stop heating the first heat exchange tube and allow the first heat exchange tube to cool naturally; when the first heat exchange tube cools naturally, argon gas is still introduced into the first heat exchange tube and the protective gas hood.

[0026] See also Figure 2 When the bent portion of the first heat exchange tube is naturally cooled, argon gas can still be introduced through the port of the first vertical portion of the first heat exchange tube and into the protective gas hood. This arrangement prevents oxygen from entering the first heat exchange tube and the protective gas hood during the natural cooling of the first heat exchange tube, thereby preventing the first heat exchange tube from being oxidized and ensuring the performance of the first heat exchange tube after heat treatment. In addition, the argon gas introduced into the first heat exchange tube and the protective gas hood can speed up the cooling rate of the first heat exchange tube, shorten the heat treatment time of the first heat exchange tube, and improve production efficiency.

[0027] Embodiment 2: See also Figures 2 to 4 The present invention also proposes a method for detecting the heat treatment performance of a heat exchange tube after bending, which is used to detect the microstructure and grain size performance of the first heat exchange tube after bending, comprising the following steps: S201: Select the first heat exchange tube after the heat treatment, select the second heat exchange tube that is not bent, and select the third heat exchange tube that is bent but not treated; S202: removing stains and rust from the surfaces of the first heat exchange tube, the second heat exchange tube, and the third heat exchange tube and performing iron ion detection on the surfaces; the solvent for removing stains and rust is acetone or ethanol; the reagent for iron ion detection is prepared by dissolving 7g of potassium ferrocyanide and 4.5ml of 65% nitric acid in 214ml of distilled water or deionized water; S203: Slice the first heat exchange tube, the second heat exchange tube and the third heat exchange tube, perform inlay polishing and chemical reagent etching on the transverse sections of the sliced ​​first heat exchange tube, the second heat exchange tube and the third heat exchange tube, and observe the microstructure and grain size of the first heat exchange tube, the second heat exchange tube and the third heat exchange tube using an optical microscope.

[0028] Embodiment three: The present invention also provides a method for detecting the hardness of a heat exchange tube bend after heat treatment, which is used to detect the hardness of a first heat exchange tube after bending, and comprises the following steps: S301: Select the first heat exchange tube after the heat treatment, select the second heat exchange tube that is not bent, and select the third heat exchange tube that is bent but not treated; S302: removing stains and rust from the surfaces of the first heat exchange tube, the second heat exchange tube, and the third heat exchange tube and performing iron ion detection on the surfaces; the solvent for removing stains and rust is acetone or ethanol; the reagent for iron ion detection is prepared by dissolving 7g of potassium ferrocyanide and 4.5ml of 65% nitric acid in 214ml of distilled water or deionized water; S303: cutting and grinding the bent portion of the first heat exchange tube, cutting and grinding the second heat exchange tube, and cutting and grinding the bent portion of the third heat exchange tube; S304: placing the first heat exchange tube, the second heat exchange tube and the third heat exchange tube on a microhardness tester, and measuring the Vickers hardness using a test force of 2.92N.

[0029]

[0030] Embodiment 4: The present invention also proposes a chemical composition analysis of a heat exchange tube after heat treatment, comprising the following steps: S401: Select the first heat exchange tube after the heat treatment, select the second heat exchange tube that is not bent, and select the third heat exchange tube that is bent but not treated; S402: The first heat exchange tube, the second heat exchange tube and the third heat exchange tube are subjected to chemical composition analysis using a spectrometer, a hydrogen, oxygen and nitrogen analyzer and a carbon and sulfur analyzer.

[0031] Chemical composition of the first heat exchange tube

[0032] Chemical composition table of the second heat exchange tube

[0033] Chemical composition table of the third heat exchange tube

[0034] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A heat treatment method for a titanium U-shaped heat exchange tube, used to restore the performance of the first heat exchange tube after the U-shaped bend, characterized in that: The following steps are involved: S1: bending the first heat exchange tube into shape, wherein the minimum bending radius of the first heat exchange tube is 50 mm; S2: removing stains and rust from the surface of the first heat exchange tube and performing iron ion detection on the surface of the first heat exchange tube; S3: clamping the two vertical parts of the first heat exchange tube on the positive and negative electrodes of the medium frequency induction heating furnace respectively; S4: placing a protective gas hood on the curved portion of the first heat exchange tube, continuously introducing argon gas through a port of the first heat exchange tube, and continuously introducing argon gas into the protective gas hood; S5: Control the medium frequency induction heating furnace to heat to 560°C ± 10°C at a heating rate of 50°C per second.

2. The heat treatment method for titanium U-shaped heat exchange tube according to claim 1, characterized in that: The heat treatment method further comprises: S6: After heating the first heat exchange tube to 560° C.±10° C., stop heating the first heat exchange tube and allow the first heat exchange tube to cool naturally.

3. The heat treatment method for titanium U-shaped heat exchange tube according to claim 1, characterized in that: In S2, the solvent for removing stains and rust on the surface of the first heat exchange tube is acetone or ethanol.

4. The heat treatment method for titanium U-shaped heat exchange tube according to claim 1 or 2, characterized in that: In S2, the reagent for detecting iron ions on the surface of the first heat exchange tube is prepared by dissolving 7 g of potassium ferrocyanide and 4.5 ml of 65% nitric acid in 214 ml of distilled water or deionized water.

5. The heat treatment method for titanium U-shaped heat exchange tube according to claim 1, characterized in that: In S4, the purity of the argon gas introduced into the first heat exchange tube and into the protective gas hood is 99.99%.

6. The heat treatment method for titanium U-shaped heat exchange tube according to claim 1 or 5, characterized in that: In S4, the flow rate of argon gas continuously introduced into the first heat exchange tube is 15 L / min, and the flow rate of argon gas continuously introduced into the protective gas hood is 25 L / min.

7. The heat treatment method for titanium U-shaped heat exchange tube according to claim 2, characterized in that: In S6, when the first heat exchange tube is cooled naturally, argon gas is still introduced into the first heat exchange tube and the protective gas hood.

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