High-cleanliness cleaning device and process for die-casting aluminum parts

Abstract

The high-cleanliness cleaning device comprises a cleaning basin, a plurality of ultrasonic transducers are annularly arranged on the side wall of the cleaning basin, the bottom face of the cleaning basin is connected with the bottom face of a vibration excitation plate through a spring seat, the vibration excitation plate is provided with a vibration exciter, and the center of the vibration excitation plate is rotationally connected with a leakage disc. The bottom surface of the drain plate is connected with the output end of a rotating motor through a universal joint A, the rotating motor is mounted below the cleaning basin, and a spraying mechanism is arranged above the cleaning basin; the technology comprises the five steps of pre-spraying cleaning, ultrasonic cleaning, neutral liquid cleaning, purified water cleaning and workpiece multi-stage drying. The cleaning equipment has the full-automatic rotary spraying function, ultrasonic excitation cleaning can be conducted on workpieces on the drain disc, the problems that the number of particles of the aluminum die-casting workpieces is out of tolerance, and the aluminum die-casting workpieces become yellow after being cleaned can be solved by combining two specially-made cleaning agents, the corrosion speed of elements such as silicon, copper and iron is increased while aluminum corrosion is slowed down, and the cleaning efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of workpiece cleaning equipment, and in particular to a high-cleanliness cleaning device and process for die-cast aluminum parts. Background Art

[0002] With the rapid development of the new energy vehicle industry, electric vehicles have become the choice of more and more people. The core of electric vehicles is the three-electric system including batteries, electronic controls and motors. Their shells and other parts are usually made of aluminum die-castings. The cleanliness of these components is crucial to the stability of the car. When they are not cleaned up to standard, particulate contamination will have a serious impact on the initial operation and subsequent use of the car system, which can greatly increase the wear rate between components, or even cause failures and dangers. At present, the cleanliness of aluminum die-castings is still a major challenge facing the industry, and there are only a few manufacturers who can truly and effectively solve this problem. The main problems are: excessive particle quantity, excessive weight, yellowing of parts after cleaning, etc. A new type of equipment and process is needed to solve the above problems. Summary of the invention

[0003] In order to solve the above problems, the present invention proposes a high-cleanliness cleaning device for die-cast aluminum parts, including a cleaning basin, a plurality of ultrasonic transducers are arranged around the side walls of the cleaning basin, the bottom surface of the cleaning basin is connected to the bottom surface of an exciting plate through a spring seat, the exciting plate is equipped with an exciter, the center of the exciting plate is rotatably connected to a drain plate, the bottom surface of the drain plate is connected to the output end of a rotating motor through a universal joint A, the rotating motor is installed below the cleaning basin, and a spray mechanism is arranged above the cleaning basin.

[0004] Furthermore, the spray mechanism includes a lifting seat, a lifting groove in the lifting seat is vertically slidably connected to the slide at the top of the spray seat, a lifting motor is provided on the top of the lifting seat, the output shaft of the lifting motor is threaded through the slide and then rotated to connect to the bottom surface of the lifting groove, a distribution chamber is provided at the bottom of the spray seat, the top of the distribution chamber is connected to the delivery pump through a telescopic tube, a heating wire is built-in in the distribution chamber, the side wall of the distribution chamber is connected to the distribution ring through a number of delivery pipes, the distribution ring body is provided with a number of control valves, and the output end of the control valve is connected to the spray nozzle.

[0005] Furthermore, the output end of the control valve is connected to the spray nozzle through a plastic hose, and threaded barrels are provided on both sides of the top of the lifting seat. The threaded barrels are transversely threadedly connected to the output screw of the horizontal adjustment motor, and the horizontal adjustment motor is installed on the gantry.

[0006] Furthermore, the eccentric block of the exciter is rotatably connected to the ear seats on both sides of the bottom surface of the excitation plate, and the central axis of the eccentric block is connected to the output end of the excitation motor through a universal joint B, and the excitation motor is installed outside the cleaning basin.

[0007] Furthermore, the spring seat includes a base cylinder, which is installed on the bottom surface of the cleaning basin, into which a spring is inserted, and into which a pin on the bottom surface of the excitation plate is inserted.

[0008] The present invention also proposes a cleaning process for the cleaning device, comprising the following steps: Pre-spray cleaning: Pump the acid spray liquid mixed with 5-7% acid cleaning agent A and PH3.0-5.5 into the distribution chamber and heat it to 58-62℃. Set the spray pressure at 9-11kgf / cm through the control valve. 2 , clean the workpiece on the drain pan for 150-160 seconds. During the cleaning process, start the rotating motor to drive the workpiece on the drain pan to rotate 360 ​​degrees, and the waste liquid is discharged from the drain port at the bottom of the cleaning basin; Ultrasonic cleaning: Close the drain port, continue to spray the acidic spray liquid until it covers the top of the rotating workpiece, set the power of the ultrasonic transducer to 2700-2800W, the frequency to 28-30KHz, and the speed of the excitation motor to 970-980r / min. Vibrate and clean the rotating workpiece for 160-180S and then drain the waste liquid; Neutral liquid cleaning: Pump the neutral spray liquid mixed with 5-7% neutral detergent B and PH6-8 into the distribution chamber and heat it to 58-62℃. Set the spray pressure at 9-11kgf / cm2 through the control valve. 2 , clean the rotating workpiece for 150-160 seconds, and the waste liquid is discharged from the drain port at the bottom of the cleaning basin; Cleaning with pure water: Close the drain port, pump in tap water at 60℃ and PH5.0-7.0 to cover the top of the workpiece, vibrate and clean the rotating workpiece for 150-160S, and then drain all the waste liquid; then inject ultrapure water at 60℃ and PH6.0-7.0 to cover the top of the workpiece, vibrate and clean for 150-160S, then open the drain port and continue to spray ultrapure water for 150-160S, with a spraying pressure of 10kgf / cm 2 ; During the two vibration cleanings, the power of the ultrasonic transducer is 2700-2800W, the frequency is 28-30KHz, and the speed of the excitation motor is 970-980r / min; Multi-stage drying of workpieces: Dry and clean compressed air is pumped into the rotating workpiece surface to blow water, and the pumping pressure is 5-7kgf / cm 2 , time 60-65S, then put the workpiece into the wind box for circulating hot air drying for 120-140S, the drying temperature is 65-70℃, and finally the workpiece is vacuum dried for 150S, the drying temperature is 70-75℃.

[0009] Furthermore, the acid cleaning agent A includes 23-27wt% of inorganic acid, 4-6wt% of chelating agent, 2-3wt% of surfactant, 5-7wt% of corrosion inhibitor, 7-12wt% of sodium nitrate, 1-2wt% of sodium silicate, 0.1-0.12wt% of diisobutyl carbinol, and the balance is deionized water.

[0010] Furthermore, the ratio of concentrated sulfuric acid to aminosulfonic acid in the inorganic acid is 3:1; the chelating agent is one or more of thioglycolic acid and triethylenetetramine; the corrosion inhibitor is one or more of sodium thiocyanate and aniline; and the surfactant is benzalkonium chloride.

[0011] Furthermore, the neutral cleaning agent B contains 3-4wt% rust inhibitor, 2-3wt% penetrant, 6-8wt% surfactant, 6-8wt% emulsifier, 20-24wt% alcohol ether compound, 0.6-0.8wt% corrosion inhibitor, 22-24wt% sulfated castor oil, 5-7wt% sodium fluoride, and the balance is N,N-dimethylacetamide.

[0012] Furthermore, the rust inhibitor is one or more of ammonium borate and strontium molybdate; the penetrant is fatty alcohol polyoxyethylene ether; the surfactant is benzalkonium bromide; the emulsifier is one or more of sodium stearoyl lactylate, polyoxyethylene ether, and sodium alkylbenzene sulfonate; the alcohol ether compound is dipropylene glycol butyl ether; and the corrosion inhibitor is one or more of hexamethylenetetramine and diethylthiourea.

[0013] The beneficial effects of the present invention are as follows: the cleaning equipment in the invention has a fully automatic rotary spraying function, and can perform ultrasonic excitation cleaning on the workpiece on the leak plate through the joint action of an ultrasonic transducer and an exciter, and further separate fine particles attached to the surface of the workpiece; the equipment combines two special types of cleaning agents and processes to solve problems such as excessive particle count in aluminum die-casting workpieces and yellowing after cleaning. It can slow down aluminum corrosion while accelerating the corrosion rate of elements such as silicon, copper, and iron, thereby improving cleaning efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a front view structural schematic diagram of the present invention; Figure 2 for Figure 1 A partial enlarged view of the middle A area; Figure 3 It is a schematic diagram of the top view of the cleaning basin assembly in the present invention; Figure 4 It is a schematic diagram of the top structure of the spray mechanism in the present invention.

[0015] The description of the accompanying drawings is as follows: 1. Cleaning basin; 2. Ultrasonic transducer; 3. Spring seat; 301. Base cylinder; 302. Spring; 4. Excitation plate; 401. Latch; 5. Exciter; 6. Leakage plate; 7. Universal joint A; 8. Rotating motor; 9. Lifting seat; 901. Lifting slot; 902. Threaded cylinder; 10. Spray seat; 1001. Slide; 1002. Distribution chamber; 1003. Heating wire; 11. Lifting motor; 12. Telescopic tube; 13. Delivery tube; 14. Distribution ring; 15. Control valve; 16. Spray nozzle; 17. Universal joint B; 18. Excitation motor. DETAILED DESCRIPTION

[0016] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to 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", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0017] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "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; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0018] The present invention will be further described below in conjunction with the accompanying drawings: like Figures 1 to 4 As shown, a high cleanliness cleaning device for die-cast aluminum parts includes a cleaning basin 1, a plurality of ultrasonic transducers 2 are arranged around the side wall of the cleaning basin 1, a plurality of latches 401 are arranged on the bottom surface of the cleaning basin 1, the latches 401 are inserted into the spring 302 of the spring seat 3, the lower end of the spring 302 is inserted into the base cylinder 301, and the base cylinder 301 is installed on the bottom surface of the cleaning basin 1. The excitation plate 4 is installed with an exciter 5, the eccentric block of the exciter 5 is rotatably connected to the ear seats on both sides of the bottom surface of the excitation plate 4, the central axis of the eccentric block is connected to the output end of the excitation motor 18 through the universal joint B17, and the excitation motor 18 is installed on the outside of the cleaning basin 1. The center of the excitation plate 4 is rotatably connected to the drain plate 6, the bottom surface of the drain plate 6 is connected to the output end of the rotating motor 8 through the universal joint A7, the rotating motor 8 is installed below the cleaning basin 1, and a spray mechanism is arranged above the cleaning basin 1.

[0019] In this embodiment, the spray mechanism includes a lifting seat 9, and threaded barrels 902 are provided on both sides of the top of the lifting seat 9. The threaded barrels 902 are transversely threaded to connect the output screw of the horizontal adjustment motor, and the horizontal adjustment motor is installed on the gantry. The lifting groove 901 in the lifting seat 9 is vertically slidably connected to the top slide 1001 of the spray seat 10. The top of the lifting seat 9 is provided with a lifting motor 11. The output shaft of the lifting motor 11 passes through the slide 1001 and then rotates to connect to the bottom surface of the lifting groove 901. The bottom of the spray seat 10 is provided with a distribution chamber 1002. The top of the distribution chamber 1002 is connected to the delivery pump through a telescopic tube 12. The distribution chamber 1002 has a built-in electric heating wire 1003. The side wall of the distribution chamber 1002 is connected to the distribution ring 14 through a number of delivery pipes 13. The body of the distribution ring 14 is provided with a number of control valves 15. The output end of the control valve 15 is connected to the spray nozzle 16 through a plastic hose.

[0020] The cleaning process of the device includes the following steps: Pre-spray cleaning: Pump the acid spray liquid mixed with 5-7% acid cleaning agent A and PH3.0-5.5 into the distribution chamber 1002 and heat it to 58-62℃. Set the spray pressure at 9-11kgf / cm through the control valve 15. 2 , clean the workpiece on the drain pan 6 for 150-160 seconds. During the cleaning process, start the rotating motor 8 to drive the workpiece on the drain pan 6 to rotate 360 ​​degrees, and the waste liquid is discharged from the drain port at the bottom of the cleaning basin 1; Ultrasonic cleaning: close the drain port, continue to spray the acidic spray liquid until it covers the top of the rotating workpiece, set the power of the ultrasonic transducer 2 to 2700-2800W, the frequency to 28-30KHz, set the speed of the excitation motor 18 to 970-980r / min, vibrate and clean the rotating workpiece for 160-180S, and then drain the waste liquid; Neutral liquid cleaning: Pump a neutral spray liquid mixed with 5-7% neutral detergent B and pH 6-8 into the distribution chamber 1002 and heat it to 58-62°C. Set the spray pressure at 9-11 kgf / cm2 through the control valve 15. 2 , clean the rotating workpiece for 150-160 seconds, and the waste liquid is discharged from the drain port at the bottom of the cleaning basin 1; Cleaning with pure water: Close the drain port, pump in tap water at 60℃ and PH5.0-7.0 to cover the top of the workpiece, vibrate and clean the rotating workpiece for 150-160S, and then drain all the waste liquid; then inject ultrapure water at 60℃ and PH6.0-7.0 to cover the top of the workpiece, vibrate and clean for 150-160S, then open the drain port and continue to spray ultrapure water for 150-160S, with a spraying pressure of 10kgf / cm 2 During the two vibration cleanings, the power of the ultrasonic transducer 2 is 2700-2800W, the frequency is 28-30KHz, and the speed of the excitation motor 18 is 970-980r / min; Multi-stage drying of workpieces: Dry and clean compressed air is pumped into the rotating workpiece surface to blow water, and the pumping pressure is 5-7kgf / cm 2 , time 60-65S, then put the workpiece into the wind box for circulating hot air drying for 120-140S, the drying temperature is 65-70℃, and finally the workpiece is vacuum dried for 150S, the drying temperature is 70-75℃.

[0021] In this embodiment, the acid cleaning agent A includes 23-27wt% of inorganic acid, in which the ratio of concentrated sulfuric acid to aminosulfonic acid is 3:1; 4-6wt% of chelating agent, which is one or more of thioglycolic acid and triethylenetetramine; 2-3wt% of surfactant, which is benzalkonium chloride; 5-7wt% of corrosion inhibitor, which is one or more of sodium thiocyanate and aniline; and 7-12wt% of sodium nitrate, 1-2wt% of sodium silicate, 0.1-0.12wt% of diisobutylcarbinol, and the balance is deionized water.

[0022] In this embodiment, the neutral cleaning agent B contains 3-4wt% rust inhibitor, which is one or more of ammonium borate and strontium molybdate; 2-3wt% penetrant, which is fatty alcohol polyoxyethylene ether; 6-8wt% surfactant, which is benzalkonium bromide; 6-8wt% emulsifier, which is one or more of sodium stearoyl lactylate, polyoxyethylene ether, and sodium alkylbenzene sulfonate; 20-24wt% alcohol ether compound, which is dipropylene glycol butyl ether; 0.6-0.8wt% corrosion inhibitor, which is one or more of hexamethylenetetramine and diethylthiourea; and 22-24wt% sulfated castor oil, 5-7wt% sodium fluoride, and the balance is N,N-dimethylacetamide.

[0023] Table 1 and Table 2 below respectively show the removal effects of acidic cleaning agent A and neutral cleaning agent B on various levels of particles at different spraying + vibration cleaning times: Table 1: Cleaning effect of acid cleaning agent A Table 2: Cleaning effect of neutral detergent B Experiments show that acidic cleaning agent A with added inorganic acid and oxidant is very suitable for cleaning die-cast aluminum parts. After 60S spraying and 90S ultrasonic cleaning, the impurity removal rate has reached 95%. If the time is extended further, the effect is no longer obvious. The impurity removal ability of neutral cleaning agent B is weaker than that of acidic cleaning agent A, but it has good rust prevention and solubilization effects. Therefore, acidic cleaning agent A is used in the process to clean and remove impurities first, and then neutral cleaning agent B is used for rust prevention.

[0024] The cleaning equipment in this invention has a fully automatic rotary spraying function, which can perform ultrasonic excitation cleaning on the workpiece on the leak plate 6 through the joint action of the ultrasonic transducer 2 and the vibrator 5, and further separate the fine particles attached to the surface of the workpiece; this equipment combines two special types of cleaning agents and processes to solve the problems of excessive particle quantity in aluminum die-casting workpieces and yellowing after cleaning. It can slow down aluminum corrosion while accelerating the corrosion rate of elements such as silicon, copper, and iron, thereby improving the cleaning efficiency.

[0025] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A high-cleanliness cleaning device for die-cast aluminum parts, comprising a cleaning basin (1), characterized in that: The side wall of the cleaning basin (1) is provided with a plurality of ultrasonic transducers (2). The bottom surface of the cleaning basin (1) is connected to the bottom surface of an excitation plate (4) via a spring seat (3). The excitation plate (4) is provided with an exciter (5). The center of the excitation plate (4) is rotatably connected to a drain plate (6). The bottom surface of the drain plate (6) is connected to the output end of a rotating motor (8) via a universal joint A (7). The rotating motor (8) is installed below the cleaning basin (1). A spray mechanism is provided above the cleaning basin (1).

2. A high cleanliness cleaning device for die-cast aluminum parts according to claim 1, characterized in that: The spray mechanism comprises a lifting seat (9), a lifting groove (901) in the lifting seat (9) vertically slidingly connected to a slide (1001) at the top of the spray seat (10), a lifting motor (11) being provided at the top of the lifting seat (9), an output shaft of the lifting motor (11) being threadedly passed through the slide (1001) and then rotatably connected to the bottom surface of the lifting groove (901), a distribution chamber (1002) being provided at the bottom of the spray seat (10), the top of the distribution chamber (1002) being connected to a delivery pump via a telescopic tube (12), a heating wire (1003) being built into the distribution chamber (1002), a side wall of the distribution chamber (1002) being connected to a distribution ring (14) via a plurality of delivery tubes (13), a body of the distribution ring (14) being provided with a plurality of control valves (15), and an output end of the control valve (15) being connected to a spray nozzle (16).

3. A high cleanliness cleaning device for die-cast aluminum parts according to claim 2, characterized in that: The output end of the control valve (15) is connected to the spray nozzle (16) via a plastic hose. Threaded barrels (902) are provided on both sides of the top of the lifting seat (9). The threaded barrels (902) are transversely threadedly connected to the output screw of the horizontal adjustment motor. The horizontal adjustment motor is installed on the gantry.

4. The high cleanliness cleaning device for die-cast aluminum parts according to claim 1, characterized in that: The eccentric block of the vibration exciter (5) is rotatably connected to the ear seats on both sides of the bottom surface of the vibration plate (4), and the central shaft of the eccentric block is connected to the output end of the vibration motor (18) through a universal joint B (17), and the vibration motor (18) is installed outside the cleaning basin (1).

5. The high cleanliness cleaning device for die-cast aluminum parts according to claim 1, characterized in that: The spring seat (3) comprises a base cylinder (301), the base cylinder (301) is mounted on the bottom surface of the cleaning basin (1), a spring (302) is inserted into the base cylinder (301), and a latch (401) on the bottom surface of the excitation plate (4) is inserted into the spring (302).

6. A cleaning process according to any one of claims 1 to 5, wherein the cleaning process comprises: The process comprises the following steps: Pre-spray cleaning: Pump the acid spray liquid mixed with 5-7% acid cleaning agent A and pH 3.0-5.5 into the distribution chamber (1002) and heat it to 58-62°C. Set the spray pressure at 9-11 kgf / cm2 through the control valve (14). 2 , cleaning the workpiece on the drain pan (6) for 150-160 seconds. During the cleaning process, the rotating motor (8) is started to drive the workpiece on the drain pan (6) to rotate 360 ​​degrees, and the waste liquid is discharged from the drain port at the bottom of the cleaning basin (1); Ultrasonic cleaning: close the drain port, continue to spray the acidic spray liquid until it covers the top of the rotating workpiece, set the power of the ultrasonic transducer (2) to 2700-2800W, the frequency to 28-30KHz, set the speed of the excitation motor (18) to 970-980r / min, vibrate and clean the rotating workpiece for 160-180S, and then drain the waste liquid; Neutral liquid cleaning: A neutral spray liquid mixed with 5-7% neutral detergent B and pH 6-8 is pumped into the distribution chamber (1002) and heated to 58-62°C. The spray pressure is set at 9-11 kgf / cm2 through the control valve (15). 2 , cleaning the rotating workpiece for 150-160 seconds, and the waste liquid is discharged from the drain port at the bottom of the cleaning basin (1); Cleaning with pure water: Close the drain port, pump in tap water at 60℃ and PH5.0-7.0 to cover the top of the workpiece, vibrate and clean the rotating workpiece for 150-160S, and then drain all the waste liquid; then inject ultrapure water at 60℃ and PH6.0-7.0 to cover the top of the workpiece, vibrate and clean for 150-160S, then open the drain port and continue to spray ultrapure water for 150-160S, with a spraying pressure of 10kgf / cm 2 During the two vibration cleanings, the power of the ultrasonic transducer (2) is 2700-2800W, the frequency is 28-30KHz, and the speed of the excitation motor (18) is 970-980r / min; Multi-stage drying of workpieces: Dry and clean compressed air is pumped into the rotating workpiece surface to blow water, and the pumping pressure is 5-7kgf / cm 2 , time 60-65S, then put the workpiece into the wind box for circulating hot air drying for 120-140S, the drying temperature is 65-70℃, and finally the workpiece is vacuum dried for 150S, the drying temperature is 70-75℃.

7. The cleaning process of the high cleanliness cleaning device for die-cast aluminum parts according to claim 6, characterized in that: The acid cleaning agent A comprises 23-27wt% of inorganic acid, 4-6wt% of chelating agent, 2-3wt% of surfactant, 5-7wt% of corrosion inhibitor, 7-12wt% of sodium nitrate, 1-2wt% of sodium silicate, 0.1-0.12wt% of diisobutyl carbinol, and the balance is deionized water.

8. The cleaning process of the high cleanliness cleaning device for die-cast aluminum parts according to claim 7, characterized in that: The ratio of concentrated sulfuric acid to aminosulfonic acid in the inorganic acid is 3:1; the chelating agent is one or more of thioglycolic acid and triethylenetetramine; the corrosion inhibitor is one or more of sodium thiocyanate and aniline; and the surfactant is benzalkonium chloride.

9. The cleaning process of the high cleanliness cleaning device for die-cast aluminum parts according to claim 6, characterized in that: The neutral cleaning agent B comprises 3-4wt% of rust inhibitor, 2-3wt% of penetrant, 6-8wt% of surfactant, 6-8wt% of emulsifier, 20-24wt% of alcohol ether compound, 0.6-0.8wt% of corrosion inhibitor, 22-24wt% of sulfated castor oil, 5-7wt% of sodium fluoride, and the balance is N,N-dimethylacetamide.

10. The cleaning process of the high cleanliness cleaning device for die-cast aluminum parts according to claim 9, characterized in that: The rust inhibitor is one or more of ammonium borate and strontium molybdate; the penetrant is fatty alcohol polyoxyethylene ether; the surfactant is benzalkonium bromide; the emulsifier is one or more of sodium stearoyl lactylate, polyoxyethylene ether, and sodium alkylbenzene sulfonate; the alcohol ether compound is dipropylene glycol butyl ether; and the corrosion inhibitor is one or more of hexamethylenetetramine and diethylthiourea.

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