Method for detecting uniformity of metal powder injection molding feeding

Abstract

The invention relates to the technical field of metal injection molding, in particular to a method for detecting uniformity of metal powder injection molding feed, which comprises the following specific steps: randomly extracting a plurality of samples from the same batch of metal powder injection molding feed at different positions, weighing a plurality of groups of samples from each sample, recording the weight of each group of samples as m1, and recording data, the apparent weight of each group of samples is obtained through a density meter and an electronic balance by utilizing a drainage method and is recorded as m2, data is recorded, the volume and density of the samples are calculated, then the standard deviation of the density of the samples is calculated according to a sample standard deviation calculation formula, then a variable coefficient is calculated, and the feeding uniformity is evaluated according to the variable coefficient. The method is simple in process, convenient to operate and short in consumed time, the uniformity of the feed is evaluated through sampling, weighing and density calculation, the uniformity of the metal powder injection molding feed can be visually and quantitatively detected, and the method is suitable for detecting the uniformity of the metal powder injection molding feed.

Description

Technical Field

[0001] The invention relates to the technical field of metal injection molding, and in particular to a method for detecting uniformity of feeding material for metal powder injection molding. Background Art

[0002] Metal injection molding (MIM) is a new near-net-shape forming technology for metal parts formed by introducing modern plastic injection molding technology into the field of powder metallurgy. It is a high-tech technology that has developed rapidly in the field of powder metallurgy and industry in recent years. In terms of manufacturing high-quality precision parts, MIM has unparalleled advantages over conventional powder metallurgy and machining methods, and has been increasingly used in the national economy. The basic process of powder injection molding includes: uniformly mixing powder with organic binder, forming with an injection molding machine, then removing the binder from the formed blank, and finally obtaining the product through sintering and densification. Among them, preparing uniform feed is one of the prerequisites for obtaining high-precision powder injection molding products.

[0003] At present, the application number "CN102445461 B" discloses a method for detecting the uniformity of feeding, which uses a scanning electron microscope to obtain a uniformity index through image observation, analysis and data statistics, thereby evaluating the uniformity of metal powder injection molding feeding. However, this method is relatively costly and only quantitatively detects the uniformity of metal powder injection molding feeding from a microscopic level, which has certain limitations.

[0004] Therefore, it is necessary to provide a method for detecting the uniformity of metal powder injection molding feeding to solve the above technical problems. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for detecting the uniformity of metal powder injection molding feeding.

[0006] The present invention provides a method for detecting the uniformity of metal powder injection molding feeding, which specifically comprises the following steps:

[0007] S1. Multiple samples were randomly selected from different positions of the same batch of metal powder injection molding feedstock;

[0008] S2. Weigh multiple groups of samples in each batch, record the weight of each group of samples as m1, and record the data;

[0009] S3. Use a density meter and an electronic balance to obtain the apparent weight of each group of samples using the displacement method, record it as m2, and record the data;

[0010] S4. The volume of the sample can be calculated using the data obtained from S2 and S3 according to the formula: v = (m1-m2) / ρwater (where ρwater is 1.0 g / cm3), and the density of all samples can be obtained using the formula ρ = m / v, where ρ is the sample density, m is the sample mass, and v is the sample volume;

[0011] S5. Calculate the standard deviation of the sample density according to the sample standard deviation calculation formula. The sample standard deviation calculation formula is: Where s is the standard deviation, xi is the density value, and n is the number of tests. is the average value;

[0012] S6. Calculate the coefficient of variation CV:

[0013] S7. Evaluate the uniformity of the feed. The uniformity of the feed product can be evaluated based on CV.

[0014] Compared with the related art, the method for detecting the uniformity of metal powder injection molding feeding provided by the present invention has the following beneficial effects:

[0015] The method of the invention has simple process, convenient operation and short time consumption. The uniformity of the feed is evaluated by sampling, weighing and density calculation, and the uniformity of the feed for metal powder injection molding can be detected very intuitively and quantitatively. The method is suitable for uniformity detection of the feed for metal powder injection molding. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention provides a flow chart of a preferred embodiment of a method for detecting uniformity of metal powder injection molding feed material. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The following describes in detail a method for detecting the uniformity of metal powder injection molding feeding material in combination with a specific embodiment.

[0020] The present invention provides a method for detecting the uniformity of metal powder injection molding feeding, which specifically comprises the following steps:

[0021] S1. Multiple samples of the same batch of metal powder injection molding feedstock were randomly selected at different locations, each of which was about 200g;

[0022] S2. Weigh several groups of samples each time. The weight of each group is about 20g, recorded as m1, accurate to 0.001, and record the weight of each group of samples.

[0023] S3. Use a density meter and an electronic balance to obtain the apparent weight of each group of samples using the water displacement method, record it as m2, and record the data.

[0024] S4. The volume of the sample can be calculated using the data obtained from S2 and S3 according to the formula: v = (m1-m2) / ρwater (where ρwater is 1.0 g / cm3), and the density of all samples can be obtained using the formula ρ = m / v, where ρ is the sample density, m is the sample mass, and v is the sample volume;

[0025] S5. Calculate the standard deviation of the sample density according to the sample standard deviation calculation formula. The sample standard deviation calculation formula is: Where s is the standard deviation, xi is the density value, and n is the number of tests. is the average value.

[0026] S6. Calculate the coefficient of variation CV:

[0027] S7. Evaluate the uniformity of the feed. The uniformity of the feed product can be evaluated based on CV.

[0028] During operation, three iron-based alloy feeds were selected, namely, Examples 1-3, and samples were prepared according to the above steps. The samples were weighed in groups, and the coefficient of variation of each example was calculated. Combined with the dimensional shrinkage ratio of the injection molded product before and after degreasing and sintering,

[0029] Tables 1-3 are detailed test values ​​of density of each sample of the iron-based alloy feed material examples 1-3, and Table 4 is the coefficient of variation of each example and the dimensional shrinkage ratio of the injection molded product before and after degreasing and sintering.

[0030] sample <![CDATA[Mass (m1)]]> <![CDATA[Apparent weight (m2)]]> Density (ρ) 1 20.012 14.66 3.7392 2 20.012 14.494 3.6267 3 20.028 14.688 3.7506 4 20.055 14.726 3.7634 5 20.059 14.708 3.7486 6 20.072 14.704 3.7392 7 20.006 14.532 3.6547 8 20.036 14.723 3.7711 9 20.034 14.729 3.7764 10 20.041 14.695 3.7488 11 20.068 14.674 3.7204 12 20.028 14.627 3.7082 13 20.056 14.713 3.7537 14 20.045 14.744 3.7814 15 20.003 14.635 3.7263 16 20.011 14.756 3.8080

[0031] Table 1

[0032] sample Mass(m1) Apparent weight(m2) Density (ρ) 1 20.022 14.762 3.8065 2 20.071 14.597 3.6666 3 20.048 14.698 3.7473 4 20.055 14.729 3.7655 5 20.062 14.741 3.7703 6 20.045 14.684 3.7390 7 20.018 14.538 3.6529 8 20.049 14.724 3.7651 9 20.024 14.746 3.7939 10 20.061 14.497 3.6055 11 20.059 14.685 3.7326 12 20.055 14.766 3.7918 13 20.076 14.533 3.6219 14 20.035 14.753 3.7931 15 20.033 14.642 3.7160 16 20.051 14.756 3.7868

[0033] Table 2

[0034] sample <![CDATA[Mass (m1)]]> <![CDATA[Apparent weight (m2)]]> Density (ρ) 1 20.078 14.752 3.7698 2 20.079 14.597 3.6627 3 20.065 14.488 3.5978 4 20.051 14.619 3.6913 5 20.053 14.911 3.8998 6 20.024 14.709 3.7675 7 20.011 14.547 3.6623 8 20.064 14.724 3.7573 9 20.026 14.806 3.8364 10 20.024 14.648 3.7247 11 20.026 14.595 3.6874 12 20.011 14.697 3.7657 13 20.082 14.743 3.7614 14 20.060 14.922 3.9042 15 20.011 14.619 3.7112 16 20.077 14.541 3.6266

[0035] Table 3

[0036]

[0037] Table 4

[0038] Among them, the standard deviation of iron-based alloy feeding example 1 is s=0.046, the average density is ρ=3.379g / cm3, and the coefficient of variation CV=1.220%; it is measured that the dimensional shrinkage ratio of this batch of injection molded products before and after degreasing and sintering is in the range of 1.162 to 1.168, and the fluctuation difference is 0.006.

[0039] The standard deviation of iron-based alloy feeding example 2 is s=0.065, the average density is ρ=3.375g / cm3, and the coefficient of variation CV=1.728%; the dimensional shrinkage ratio of this batch of injection molded products before and after degreasing and sintering is in the range of 1.162 to 1.171, with a fluctuation range of 0.009.

[0040] The standard deviation of the product of iron-based alloy feeding example 3 is s=0.088, the average density is ρ=3.379g / cm3, and the coefficient of variation CV=2.353%; the dimensional shrinkage ratio of this batch of injection molded products before and after degreasing and sintering is in the range of 1.158-1.182, and the fluctuation range is 0.024.

[0041] It can be seen that the larger the coefficient of variation CV value, the more uneven the feeding product is, resulting in greater fluctuations in the shrinkage ratio of the injection molded product, and the more unstable and poorer the uniformity of the product. The coefficient of variation of Example 2 is 1.728%, which is less than 2%, and the shrinkage fluctuation is small; the coefficient of variation of Implementation 3 is 2.35%, which is greater than 2%, and the shrinkage fluctuation is significantly increased. Therefore, the coefficient of variation CV can be taken as 2% as the critical value, and when the coefficient of variation CV is less than 2%, it can be regarded as a product with good uniformity.

[0042] The working principle of a method for detecting the uniformity of metal powder injection molding feeding provided by the present invention is as follows:

[0043] The uniformity of the feed can be evaluated by sampling, weighing and density calculation, which can detect the uniformity of the feed for metal powder injection molding very intuitively and quantitatively. It is suitable for the uniformity detection of the feed for metal powder injection molding.

[0044] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for detecting the uniformity of metal powder injection molding feed, characterized in that: The specific steps are as follows: S1, randomly selecting multiple samples at different positions of the same batch of metal powder injection molding feed; S2. Weigh multiple groups of samples in each batch, record the weight of each group of samples as m1, and record the data; S3. Use a density meter and an electronic balance to obtain the apparent weight of each group of samples using the displacement method, record it as m2, and record the data; S4. The volume of the sample can be calculated using the data obtained from S2 and S3 according to the formula: v = (m1-m2) / ρwater, and the density of all samples can be obtained using the formula ρ = m / v, where ρ is the sample density, m is the sample mass, and v is the sample volume; S5. Calculate the standard deviation of the sample density according to the sample standard deviation calculation formula; S6. Calculate the coefficient of variation CV according to the coefficient of variation calculation formula; S7. Evaluate feeding uniformity based on coefficient of variation CV.

2. A method for detecting uniformity of metal powder injection molding feed according to claim 1, characterized in that: The metal powder in S1 is one of stainless steel, low alloy steel, titanium alloy, and tungsten-molybdenum alloy.

3. A method for detecting uniformity of metal powder injection molding feed according to claim 2, characterized in that: In the S1, the number of samples randomly selected from different positions of the same batch of metal powder injection molding feed is 4, and the number of groups of samples weighed from each batch in the S2 is 4.

4. A method for detecting uniformity of metal powder injection molding feed according to claim 3, characterized in that: The weight of each of the samples randomly selected from different positions of the same batch of metal powder injection molding feed in S1 is 200 g.

5. A method for detecting uniformity of metal powder injection molding feed according to claim 4, characterized in that: The standard deviation calculation formula of the samples in S5 is: Where s is the standard deviation, xi is the density value, and n is the number of tests. is the average value.

6. A method for detecting uniformity of metal powder injection molding feed according to claim 5, characterized in that: The calculation formula of the coefficient of variation in S6 is: Where s is the standard deviation, is the average value.

7. A method for detecting uniformity of metal powder injection molding feed according to claim 1, characterized in that: In S7, when the feeding uniformity is evaluated based on the coefficient of variation C, when CV<2%, the feeding product is considered to be mixed uniformly.

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