Metal sample chip pre-freezing sample preparation method

Abstract

The invention discloses a metal sample chip pre-freezing sample preparation method. The method comprises the following steps: S1, pre-freezing treatment; the method comprises the following steps: firstly, uniformly mixing metal sample chips, dividing and putting the metal sample chips into a sample container, then pouring liquid nitrogen into the sample container or putting the sample container into low-temperature refrigeration equipment, and carrying out ultralow-temperature freezing pretreatment on the metal sample chips to obtain a pre-frozen sample; s2, cutting and sieving; starting a sampling machine to idle, and then pouring the pre-frozen sample into the sampling machine for cutting, crushing and screening to obtain an oversize sample and an undersize sample; s3, sample preparation and sealing; uniformly mixing and dividing the sample into four parts according to a quartering method to obtain a metal sample, and sealing and storing the metal sample with aluminum foil bags respectively. According to the method, the metal sample scraps are subjected to ultralow-temperature freezing pretreatment before sample preparation, the dislocation density of the metal sample scraps is increased, dislocation is difficult to move under the ultralow-temperature effect, stress is no longer relieved through plastic deformation when metal is subjected to external force, brittleness is enhanced, brittle fracture is easier to occur, and the sample preparation efficiency and the sample preparation quality are improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal sample sampling and sample preparation, and in particular to a metal sample chip pre-freezing sample preparation method. Background Art

[0002] The collection and preparation of samples are key factors in evaluating raw materials and products. Take crude copper and copper anode plates as examples: crude copper (nickel) and copper (nickel) anode plates are intermediate products of pyrometallurgy and are also one of the important raw materials for wet electrolytic copper products. The obtained lead-bismuth alloy and other additional products are important products and raw materials for smelting production enterprises. As an important basis for guiding production and settlement, the samples obtained need to be representative, so the accuracy of chemical analysis of samples is required to be high. Usually, the sample preparation method of metal samples includes: drilling, iron removal, reduction, grinding and screening. However, due to the high content of the main grade of metal products and their high value, in order to ensure the representativeness of the samples, each step of the sample preparation needs to be strictly weighed to minimize the loss of sample preparation. Therefore, the workload of sample preparation is greatly increased, resulting in a large proportion of the sample preparation process in the total sample preparation time, high cumbersomeness of the work, and low sample preparation efficiency.

[0003] At present, the technical difficulties in preparing metal samples such as copper, nickel, and lead mainly lie in the grinding stage. Poor control of the grinding time or excessive temperature of the sample preparation equipment will affect the representativeness of the sample. In addition, during the grinding process, each sample is repeatedly ground and sieved for at least 25 minutes, which is time-consuming. In addition, the sample bowl itself is heavy (generally 5000-10000g), and manual handling of the sample bowl is labor-intensive. Based on this, the method of grinding solid metal samples was improved. First, the operator reduced the drilled sample chips to the required sample size, and then used a sealed sample preparation machine or cutter to directly grind and cut the sample chips. However, this method has the following problems when preparing samples: (1) Due to the limited volume of the sample bowl of the sample preparation machine, there is a certain limit on the sample injection amount. Usually, the sample injection amount is about 150 to 500 g each time, so each batch of samples needs to be ground several times, which takes a long time; (2) Due to the high hardness of metals such as nickel, copper, lead, and bismuth, it takes a long time to grind to achieve the required fineness. High temperature will be generated during the grinding process, causing high-temperature oxidation of the copper chips. After multiple grindings of the sample bowl, the temperature of the bowl body itself increases. Therefore, during the sample preparation process, an appropriate amount of alcohol needs to be added to assist in cooling and prevent sample oxidation. After grinding, the attached The alcohol on the surface of the sample is naturally dried to avoid the influence of alcohol immersion on the sample. The overall sample preparation process is cumbersome and labor-intensive; (3) The grade content of the metal sample in chip form is relatively high, and it is easy to cause sample oxidation due to the influence of air humidity, temperature and time; (4) During the grinding process, the temperature control of the sample bowl and equipment depends on the work experience of the operator, so there will inevitably be errors in the manual measurement of the sample preparation machine temperature, resulting in problems such as poor control of the sample preparation time and excessive temperature of the sample preparation equipment that affect the representativeness of the sample, thereby increasing the wear rate of the sample preparation equipment; (5) Each sample takes a long time to be repeatedly ground and sieved. If there are many samples to be prepared, in order to prevent the sample from being unable to continue to be prepared after oxidation, it is necessary to wait for the sample preparation machine temperature to drop before continuing to prepare the sample, which further prolongs the sample preparation time and reduces the sample preparation efficiency. Summary of the invention

[0004] The invention provides a method for pre-freezing and preparing metal sample chips, which pre-treats the metal sample chips with ultra-low temperature freezing before preparing the sample, so that the sample to be prepared reaches a low temperature and brittle state, thereby achieving the purpose of rapid and efficient sample preparation.

[0005] To achieve its purpose, the present invention adopts the following technical solution: A method for pre-freezing metal sample chips comprises the following steps: S1: pre-freezing treatment: firstly, the metal sample chips are mixed and then shrunk, and then the shrunk metal sample chips are placed in a sample container, and then liquid nitrogen is poured into the sample container or the sample container is placed in a low-temperature refrigeration device to perform ultra-low temperature freezing pre-treatment on the metal sample chips to obtain pre-frozen samples; S2: cutting and sieving; start the sample making machine, idle for at least 30 seconds, and then pour the pre-frozen sample obtained in step S1 into the sample making machine for cutting, crushing and sieving to obtain an oversize sample and an undersize sample; S3: preparing samples and sealing them; weigh the sieve-surface sample and the sieve-undersize sample obtained in step S2 respectively, mix them evenly and divide them into 4 parts according to the quartering method to obtain metal samples, and then seal them separately in aluminum foil bags.

[0006] Furthermore, in step S1, when liquid nitrogen is poured into the sample container, the liquid nitrogen must completely cover all metal sample chips, and then the sample container is sealed with a plastic film for freezing. After the freezing is completed, the plastic film is removed and the sample is prepared after the liquid nitrogen is completely vaporized.

[0007] Furthermore, in step S1, after the liquid nitrogen is poured into the sample container, the freezing time is 20 to 30 seconds.

[0008] Furthermore, in step S1, when liquid nitrogen is used for pre-freezing, one sample is prepared first, and then the next sample is pre-frozen using liquid nitrogen.

[0009] Furthermore, in step S1, the temperature of the low-temperature refrigeration equipment is ≤-80°C, and the freezing time is 2 to 4 hours.

[0010] Furthermore, in step S1, when pre-freezing is performed using a low-temperature refrigeration device, after one sample is produced, another sample is taken out of the low-temperature refrigeration device and sent to the sample preparation machine.

[0011] Furthermore, the time interval between taking out the pre-frozen sample in step S1 and sending it into the sample preparation machine in step S2 is less than 10 minutes.

[0012] Furthermore, the reduction in weight of each portion during the pre-freezing treatment in step S1 is ≥1200g, and the reduction in weight of each portion during the sample preparation in step S3 is ≥150g.

[0013] Furthermore, the sample making machine of step S2 includes a feed port arranged at the top of the machine body, and a cutting device and a screening device are connected to the bottom of the feed port in sequence; the cutting device includes a rotating cutter body rotatably connected to its inner cavity, and a plurality of cutting heads are connected to the periphery of the rotating cutter body; the screening device includes a first standard screen arranged along the circumference of the inner wall of the cutting device cabin with the rotating cutter body as the center, and a second standard screen is arranged below the first standard screen; a power switch is provided on the outer wall of the sample making machine.

[0014] Furthermore, the mesh size of the first standard sieve is 10 meshes, and the mesh size of the second standard sieve is 40 meshes.

[0015] The beneficial effects of the present invention are as follows: 1. Solid metal has good plasticity at room temperature because the atomic arrangement in the local area of ​​the crystal is misaligned. This misalignment is not on the crystal plane, but extends along a straight line to form a linear defect that can move in the crystal. When subjected to external force, the metal can adapt to deformation through the movement of dislocations. The method of the present invention increases the dislocation density of the metal sample by pre-treating the metal sample with ultra-low temperature before sample preparation. Under the action of ultra-low temperature, dislocations are difficult to move, so that metals such as nickel and copper no longer relieve stress through plastic deformation when subjected to external force. On the one hand, its brittleness is enhanced, brittle fracture is more likely to occur, and the sample preparation rate is improved. On the other hand, by effectively controlling the temperature, the sample preparation quality is improved, the accuracy of the analysis of crude copper and copper anode plate samples is enhanced, and the adverse effects of long sample preparation time on the sample are eliminated. In addition, the cut sample chips have uniform particle size and small particle size, which greatly improves the quality of samples for chemical analysis. It can be extended to the sample preparation process of all solid metal samples, with good versatility and strong practicality.

[0016] 2. After the metal sample is pre-frozen, its own temperature has reached a low temperature state. Therefore, when the low-temperature sample enters the sample preparation machine for sample preparation, its own low temperature can offset the high temperature generated by the body during the sample preparation process, so as to achieve the purpose of keeping the sample preparation machine at a low temperature and effectively prevent the oxidation of the sample caused by high temperature. In addition, in order to further improve the sample preparation effect, before the pre-frozen sample begins to be prepared, the time the sample stays at room temperature should be reduced as much as possible to prevent the pre-frozen sample from being exposed to room temperature, causing the temperature to rise and the brittleness to decrease. Specifically, since the liquid nitrogen treatment time is short, when liquid nitrogen is used for pre-freezing, one sample is first made, and then the next sample is pre-frozen with liquid nitrogen. When a low-temperature refrigeration device is used for pre-freezing, the processing time is long, so after one sample is made, the next sample is taken from the low-temperature refrigeration device and sent to the sample preparation machine for sample preparation. During the pre-freezing process, the components contained in the metal sample are not affected by the low temperature, so the composition of the metal sample obtained after the pre-freezing treatment will not fluctuate, and the obtained sample is representative. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a sample preparation flow chart of the present invention; Figure 2 It is a schematic diagram of the structure of the sample making machine of the present invention; In the figure: 1-prototype making machine; 2-feeding port; 3-cutting device; 4-rotating cutter body; 5-cutting cutter head; 6-first standard sieve; 7-second standard sieve; 8-power switch. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with embodiments: In the following embodiments of the present invention, since the processing time of liquid nitrogen instantaneous freezing is relatively short, when liquid nitrogen is used for pre-freezing, in order to ensure the quality of sample preparation, it is necessary to first prepare a sample, then use liquid nitrogen to pre-freeze the next sample, and finally send it to the sample preparation machine for sample preparation. When low-temperature refrigeration equipment is used for pre-freezing, since the freezing processing time is long, it is necessary to freeze the samples in advance, and after one sample is prepared, the next pre-frozen sample is taken out from the low-temperature refrigeration equipment, and finally sent to the sample preparation machine for sample preparation.

[0019] The sample making machine 1 includes a feed port 2 arranged at the top of the machine body, and a cutting device 3 and a screening device are connected to the bottom of the feed port 2 in sequence; the cutting device 3 includes a rotating cutter body 4 rotatably connected in its inner cavity, and a plurality of cutting bits 5 are connected to the outer periphery of the rotating cutter body 4, and the outer side of the cutting device 3 is rotatably connected to a cabin door; the screening device includes a first standard screen 6 arranged circumferentially along the inner wall of the cabin of the cutting device 3 with the rotating cutter body 4 as the center, and a second standard screen 7 is arranged below the first standard screen 6; a power switch 8 is provided on the outer wall of the sample making machine 1.

[0020] When preparing samples, first check that the cutting device 3 cabin of the sample preparing machine 1 is clean, then install the rotating cutter body 4 in the cabin of the cutting device 3, and then close the cabin door of the cutting device 3; then turn on the power switch 8, start the sample preparing machine 1, idle for 30 seconds, pour the pre-frozen sample into the sample preparing machine 1 from the feed port 2, and cut and crush the sample under the rotation of the rotating cutter body 4. The crushed samples all pass through the first standard sieve 6 of the screening device and fall into the second standard sieve 7 for screening to obtain the above-sieve sample and the below-sieve sample.

[0021] Example 1 The method for preparing a sample by pre-freezing metal sample chips of the present invention is used to process a solid copper anode plate sample (copper content ≥ 98%), comprising the following steps: S1: Pre-freezing treatment; first collect and mix the copper anode plate sample chips and then reduce them into 1200g portions. Then spread the reduced copper anode plate sample chips flat in the sample container. The operator wears anti-freeze protective clothing and gloves, holds the sample spoon handle and scoops 500ml of liquid nitrogen from a 15kg liquid nitrogen barrel and pours it evenly into the sample container. It should be noted that the liquid nitrogen must completely cover all the copper anode plate sample chips. Then seal the sample container with a plastic film and freeze it for 20s. The copper anode plate sample chips are pre-treated with ultra-low temperature freezing. After the freezing is completed, the plastic film is opened to obtain the pre-frozen sample. Sample preparation is carried out after the liquid nitrogen is completely vaporized. S2: cutting and screening; using the sample preparation machine 1 to cut, crush and screen the crude copper sample to obtain the sieve sample and the sieve sample; wherein, the time interval between taking out the pre-frozen sample in step S1 and feeding it into the sample preparation machine in step S2 is 5 minutes; S3: Sample preparation and sealing; After weighing the oversize sample and undersize sample obtained in step S2 respectively, 1086.5g of oversize sample and 102.3g of undersize sample are obtained. Ignoring sample loss, calculation shows that the oversize sample accounts for 91.39% and the undersize sample accounts for 8.61%. Mix and reduce them into 4 portions according to the quartering method to obtain 297.2g of metal samples in each portion, and then seal them in aluminum foil bags respectively.

[0022] Example 2 The method for preparing a metal sample by pre-freezing the metal sample chips of the present invention is used to process a solid crude copper sample (copper content ≥ 95%), comprising the following steps: S1: Pre-freezing treatment; first collect and mix the crude copper sample chips and then reduce them into portions, each portion being 1200 g, and then spread the reduced copper anode plate sample chips flat in a sample container. The operator wears anti-freeze protective clothing and gloves, and puts the sample container into a low-temperature refrigeration device at -80°C for 2 hours to perform ultra-low temperature freezing pretreatment on the crude copper sample chips to obtain pre-frozen samples; S2: cutting and screening; using the sample preparation machine 1 to cut, crush and screen the crude copper sample to obtain the sieve sample and the sieve sample; wherein, the time interval between taking out the pre-frozen sample in step S1 and feeding it into the sample preparation machine in step S2 is 6 minutes; S3: Sample preparation and sealing; After weighing the oversize sample and undersize sample obtained in step S2, 1087.3g of oversize sample and 101.9g of undersize sample were obtained. Ignoring sample loss, calculation shows that the oversize sample accounts for 91.43% and the undersize sample accounts for 8.57%. Mix and reduce them into 4 portions according to the quartering method, and obtain metal samples with a reduced weight of 297.3g each, and then seal them in aluminum foil bags.

[0023] Example 3 The method for preparing a metal sample by pre-freezing the metal sample chips of the present invention is used to process a solid crude copper sample (copper content ≥ 90%), comprising the following steps: S1: Pre-freezing treatment; first collect and mix the crude copper sample chips and then reduce them into portions, each portion being 1200g, and then spread the reduced copper anode plate sample chips flat in a sample container, the operator wears anti-freeze protective clothing and gloves, puts the sample container into a low-temperature refrigeration device at -80°C, freezes for 4 hours, and performs ultra-low temperature freezing pretreatment on the crude copper sample chips to obtain pre-frozen samples; S2: cutting and screening; using the sample preparation machine 1 to cut, crush and screen the crude copper sample to obtain the sieve-surface sample and the sieve-underface sample; wherein, the time interval between taking out the pre-frozen sample in step S1 and feeding it into the sample preparation machine in step S2 is 10 minutes; S3: Sample preparation and sealing; After weighing the oversize sample and undersize sample obtained in step S2 respectively, 1078.2g of oversize sample and 112.4g of undersize sample are obtained. Ignoring sample loss, calculation shows that the oversize sample accounts for 90.56% and the undersize sample accounts for 9.44%. Mix and reduce them into 4 portions according to the quartering method to obtain metal samples with a reduced weight of 297.65g per portion, and then seal them separately in aluminum foil bags.

Claims

1. A method for preparing metal sample chips by pre-freezing, characterized in that: The following steps are involved: S1: pre-freezing treatment: firstly, the metal sample chips are mixed and then shrunk, and then the shrunk metal sample chips are placed in a sample container, and then liquid nitrogen is poured into the sample container or the sample container is placed in a low-temperature refrigeration device to perform ultra-low temperature freezing pre-treatment on the metal sample chips to obtain pre-frozen samples; S2: cutting and screening; starting the sample preparation machine (1), idling for at least 30 seconds, and then pouring the pre-frozen sample obtained in step S1 into the sample preparation machine (1) for cutting, crushing and screening to obtain an oversize sample and an undersize sample; S3: preparing samples and sealing them; weigh the sieve-surface sample and the sieve-undersize sample obtained in step S2 respectively, mix them evenly and divide them into 4 parts according to the quartering method to obtain metal samples, and then seal them separately in aluminum foil bags.

2. A method for preparing metal sample chips by pre-freezing as claimed in claim 1, characterized in that: In step S1, when liquid nitrogen is poured into the sample container, the liquid nitrogen must completely cover all the metal sample chips, and then the sample container is sealed with a plastic film for freezing. After the freezing is completed, the plastic film is removed and the sample is prepared after the liquid nitrogen is completely vaporized.

3. A method for preparing metal sample chips by pre-freezing as claimed in claim 2, characterized in that: In step S1, after liquid nitrogen is poured into the sample container, the freezing time is 20 to 30 seconds.

4. A method for preparing metal sample chips by pre-freezing as claimed in claim 3, characterized in that: In step S1, when liquid nitrogen is used for pre-freezing, one sample is prepared first, and then the next sample is pre-frozen using liquid nitrogen.

5. A method for preparing metal sample chips by pre-freezing as claimed in claim 1, characterized in that: In step S1, the temperature of the low-temperature refrigeration equipment is ≤-80°C, and the freezing time is 2 to 4 hours.

6. A method for preparing metal sample chips by pre-freezing as claimed in claim 5, characterized in that: In step S1, when pre-freezing is performed using a low-temperature refrigeration device, after one sample is produced, another sample is taken out of the low-temperature refrigeration device and sent to the sample preparation machine.

7. A method for preparing metal sample chips by pre-freezing as claimed in any one of claims 1 to 6, characterized in that: The time interval between taking out the pre-frozen sample in step S1 and sending it into the sample preparation machine in step S2 is less than 10 minutes.

8. A method for preparing metal sample chips by pre-freezing as claimed in claim 7, characterized in that: The reduction in weight of each portion during the pre-freezing treatment in step S1 is ≥1200g, and the reduction in weight of each portion during the sample preparation in step S3 is ≥150g.

9. A method for preparing metal sample chips by pre-freezing as claimed in claim 8, characterized in that: Step S2: the sample making machine (1) comprises a feed port (2) arranged at the top of the machine body, and the bottom of the feed port (2) is connected to a cutting device (3) and a screening device in sequence; the cutting device (3) comprises a rotating blade body (4) rotatably connected in its cabin, and a plurality of cutting blade heads (5) are connected to the outer periphery of the rotating blade body (4); the screening device comprises a first standard screen (6) arranged along the circumferential direction of the inner wall of the cabin of the cutting device (3) with the rotating blade body (4) as the center, and a second standard screen (7) is arranged below the first standard screen (6); and a power switch (8) is arranged on the outer wall of the sample making machine (1).

10. A method for preparing metal sample chips by pre-freezing as claimed in claim 9, characterized in that: The mesh size of the first standard sieve (6) is 10 meshes, and the mesh size of the second standard sieve (7) is 40 meshes.

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