阅读说明：本技术 一种检测弹簧中碳、硫含量的方法 (Method for detecting carbon and sulfur contents in spring ) 是由 胡乐明 邢文青 郝志奎 黄合生 黄波 吴红兵 吴超超 梁小红 尚聪亚 于 2021-09-24 设计创作，主要内容包括：一种检测弹簧中碳、硫含量的方法,包括以下步骤S1、盐酸、硝酸、无水乙醇、丙酮、去离子水按照一定的比例配置酸蚀溶液；S2、将弹簧置于盛有上述酸蚀溶液的容器中,进行加热处理；S3、将加热处理后的弹簧取出,进行清洗处理之后,将弹簧拉直、打磨、剪切,获得弹簧段；S4、将弹簧段置于超声波清洗液中,进行超声震荡处理；S5、将超声震荡处理后的弹簧段冲洗后,进行烘干处理；S6、取烘干处理后弹簧段,进行碳、硫含量的检测。该方法可充分有效去除弹簧表面防腐保护层,满足检测要求,检测结果稳定准确。(A method for detecting the contents of carbon and sulfur in a spring comprises the following steps of S1, preparing an acid etching solution by hydrochloric acid, nitric acid, absolute ethyl alcohol, acetone and deionized water according to a certain proportion; s2, placing the spring in a container containing the acid etching solution, and heating; s3, taking out the spring after the heating treatment, cleaning, straightening, polishing and shearing the spring to obtain a spring section; s4, placing the spring section in an ultrasonic cleaning solution, and performing ultrasonic oscillation treatment; s5, washing the spring section after ultrasonic oscillation treatment, and drying; and S6, taking the spring section after drying treatment, and detecting the content of carbon and sulfur. The method can fully and effectively remove the anticorrosive protection layer on the surface of the spring, meets the detection requirements, and has stable and accurate detection results.)

1. A method for detecting the contents of carbon and sulfur in a spring is characterized by comprising the following steps:

s1, preparing an acid etching solution;

s2, placing the spring in a container containing the acid etching solution, and heating;

s3, taking out the spring after the heating treatment, cleaning, straightening, polishing and shearing the spring to obtain a spring section;

s4, placing the spring section in an ultrasonic cleaning solution, and performing ultrasonic oscillation treatment;

s5, washing the spring section after ultrasonic oscillation treatment, and drying;

s6, taking the spring section after drying treatment, and detecting the content of carbon and sulfur;

in step S1, the acid etching solution is prepared from hydrochloric acid, nitric acid, absolute ethyl alcohol, acetone, and deionized water in a volume ratio of 10-20: 5-10: 10-20: 20-30: 20-55, wherein the concentration of the hydrochloric acid is 36-40 wt%, and the concentration of the nitric acid is 63-67 wt%.

2. The method according to claim 1, wherein the heating treatment is performed at 55 to 65 ℃ for 25 to 35min in step S2.

3. The method of claim 1, wherein the step S3, straightening the spring, and performing a rough grinding process using 100# sandpaper.

4. The method according to claim 1, wherein in step S4, the ultrasonic cleaning solution is prepared from hydrochloric acid, nitric acid and absolute ethyl alcohol according to a volume ratio of 5-10: 5-10: 80-90 configuration; the concentration of the hydrochloric acid is 36-40 wt%, and the concentration of the nitric acid is 63-67 wt%.

5. The method according to claim 4, wherein in step S4, the ultrasonic oscillation time is 25-30 min.

6. The method according to claim 1, wherein in step S5, the drying temperature is 100-110 ℃ and the drying time is 8-10 min.

7. The method according to claim 1, wherein in step S6, the carbon and sulfur content is detected by infrared absorption spectroscopy, and the detecting step comprises: placing a fluxing agent and a spring section in a crucible, and then detecting by adopting an infrared carbon sulfur instrument; the fluxing agent comprises tin particles, iron particles and tungsten particles.

8. The method of claim 7, wherein the mass ratio of the spring segments, the tin particles, the iron particles and the tungsten particles is as follows: 0.18-0.22: 0.15-0.25: 0.4-0.6: 1-2.

9. The method of claim 7, wherein the sequence of placing the flux, spring segments in the crucible is: and mixing tin particles and iron particles, placing the mixture at the bottom of a crucible, then placing the mixture into a spring section, and finally covering the spring section by adopting tungsten particles.

10. The method according to any one of claims 1 to 9, wherein the spring stock has a carbon content of: 0.24-0.9 wt% and sulfur content 0.002-0.030 wt%.

Technical Field

The application relates to the technical field of metallurgical analysis, in particular to a method for detecting carbon and sulfur contents in a spring.

Background

Spring steel is a steel which is used exclusively for the manufacture of springs and elastic elements, the elasticity of which depends on its ability to deform elastically, i.e. within a specified range, so that it withstands a certain load without permanent deformation after the load has been removed. The spring steel is required to have high tensile strength, elastic limit and high fatigue strength because the spring needs to be used under impact, vibration or long-term alternating stress, wherein the spring steel is required to have certain hardenability, difficult decarburization, good surface quality and the like in process, the content of carbon and sulfur in the spring steel is required to be in a specified range in composition, namely, the content of carbon and sulfur in the spring steel is an important parameter of the spring steel, the detection of the content of carbon and sulfur is a common detection item of the detection of the spring steel, and the detection result is one of important judgments of material quality and performance.

The method for detecting the carbon and sulfur contents in the spring steel comprises the following steps: volumetric method of combustion gas, infrared absorption spectroscopy, iodometry, gravimetric method, etc.; the infrared absorption spectrometry has the characteristics of high detection speed, wide measurement range, accurate detection result and the like, and is a common detection method in the field.

When the spring steel has quality objection, the inspection sample is often made into a spring finished product, the requirement of directly reading the spectrum sample cannot be met, the sample cannot be drilled, and the spring steel is processed into chips, particles and powder and is difficult to detect by a carbon-sulfur instrument. The detection can be carried out only after the material is processed into a segment shape after being drawn. However, the inventor finds that the carbon and sulfur data measured by the method are unstable in the experimental process, and the detection result is often greatly different from the actual component content in the spring steel.

The analysis shows that in order to protect the spring from being corroded, the surface layer of the spring is provided with an anticorrosive protective layer, the components of the anticorrosive protective layer generally comprise a metal coating, antirust oil and an organic polymer coating, wherein the metal coating also comprises a small amount of organic and non-polar chemical components besides metal components, and when the spring is galvanized, a brightener, a displacement agent, a softening agent, an impurity resisting agent, a stabilizer, a pinhole resisting agent, an inhibitor and the like are also added besides zinc salt; the organic polymer coating is generally formed by dipping or spraying organic substances such as paint, asphalt, plastics, rust-proof oil, etc. on the spring to protect the spring from corrosion. That is, due to the presence of the corrosion-resistant protective layer, especially, carbon and sulfur are contained therein, which leads to inaccuracy of the detection result.

For the anticorrosion protective layer, the anticorrosion protective layer is mostly removed by a sand paper grinding mode in the prior art, but because the spring cannot be completely straightened, a plurality of parts which cannot be ground exist during grinding, and the anticorrosion protective layer of the parts cannot be removed; in addition, if the sanding is too deep for a long time, fine mineral sand in the sand paper or the sand belt can be embedded into the sample, so that the sample is polluted, and the detection result is influenced.

Therefore, in order to solve the problems in the prior art, it is urgently needed to invent a method suitable for detecting the contents of carbon and sulfur in a spring.

Disclosure of Invention

Aiming at the defects in the prior art, the application aims to provide the method for detecting the carbon and sulfur contents in the spring, and by the method, the anti-corrosion protective layer on the surface of the spring can be sufficiently and effectively removed, the detection requirement is met, and the detection result is stable and accurate.

The application example provides a method for detecting the content of carbon and sulfur in a spring, which comprises the following steps:

s1, preparing an acid etching solution;

s2, placing the spring in a container containing the acid etching solution, and heating;

s3, taking out the spring raw material after the heating treatment, cleaning, straightening, polishing and shearing the spring to obtain a spring section;

s4, placing the spring section in an ultrasonic cleaning solution, and performing ultrasonic oscillation treatment;

s5, washing the spring section after ultrasonic oscillation treatment, and drying;

s6, taking the spring section after drying treatment, and detecting the content of carbon and sulfur;

in step S1, the acid etching solution is prepared from hydrochloric acid, nitric acid, absolute ethyl alcohol, acetone, and deionized water in a volume ratio of 10-20: 5-10: 10-20: 20-30: 20 to 55 (e.g., 11:8:12:23:25, 12:9:15:22:35, 15:7:17:27:45, 17:6:11:28:50, 19:6:18:26:40, etc.), the hydrochloric acid concentration being 36 to 40 wt% (e.g., 36.5 wt%, 37 wt%, 37.5 wt%, 38 wt% 38.5 wt%, 39 wt%, or 39.5 wt%, etc.), and the nitric acid concentration being 63 to 67 wt% (e.g., 63.5 wt%, 64 wt%, 64.5 wt%, 65 wt%, 65.5 wt%, 66 wt%, or 66.5 wt%, etc.).

In the acid etching solution, the acidity and strong oxidizing property of hydrochloric acid and nitric acid are fully utilized to react with and remove the metal in the coating, wherein if the content of the acid in the acid etching solution is lower than the ratio range, the reaction speed is too slow, and the metal in the coating cannot be effectively removed, and if the content of the acid is higher than the ratio range, particularly if the content of the nitric acid is too high, the metal surface in the coating is passivated, so that the reaction is prevented from being carried out; in addition, the acid etching solution also contains ethanol and acetone in a certain proportion, wherein the ethanol is a protic solvent and has active hydrogen, molecules of the ethanol contain O-H bonds, and the ethanol is a hydrogen bond donor and a hydrogen bond acceptor in chemical reaction, so that polar solute molecules can form unstable active intermediates, the hydrogen bond donor and the hydrogen bond acceptor have a catalytic action, the formation of ions can be promoted, and the single-molecule reaction is facilitated. Acetone is an aprotic solvent, and since the molecules of the aprotic polar solvent have polarity, the acetone has an influence on solute molecules, produces a solvation effect, and has stronger dissolving capacity. In chemical reactions, nonpolar protic solvents are favored for the SN1 reaction mechanism, while polar aprotic solvents are favored for the SN2 reaction mechanism. The two are added into the acid etching solution in a matching way, so that the dissolving capacity of the acid etching solution on organic matters can be fully utilized to remove organic components in the anticorrosion protective layer; in the acid etching solution, if the content of the organic solvent (particularly the content of acetone) is too low, the reaction rate is too low, the dissolution rate of organic matters is too low, and the problem that the anticorrosive layer is not fully reacted and organic components in the acid etching solution are volatilized occurs; if the content of the organic solvent (particularly the content of acetone) is too high, the vapor content of the organic solvent in the air is too high, slight damage is caused to the human body, and the use safety and environmental protection of the reagent need to be considered.

In a possible embodiment, because the density of the hydrochloric acid and the nitric acid is greater than that of the deionized water, the ethanol and the acetone, when the acid etching solution is prepared, the deionized water, the absolute ethanol and the acetone are mixed in a container, and then the acid is slowly poured into the container along the wall of the container to prevent violent reaction and splash out to hurt people; the container is preferably a beaker, flask, or the like.

In one possible embodiment, in step S2, the temperature of the heat treatment is 55 to 65 ℃ (e.g., 56 ℃, 57 ℃, 58 ℃, 59 ℃, 60 ℃, 61 ℃, 62 ℃, 63 ℃ or 64 ℃, etc.) and the time is 25 to 35min (e.g., 26min, 27min, 28min, 29min, 30min, 31min, 32min, 33min or 34min, etc.).

In one possible embodiment, the spring is placed in an acid etching solution, which is submerged in the spring; for better control of the heating temperature, heating by means of electric hot plates is preferred.

The spring is placed in acid etching solution for heating treatment, on one hand, the surface of a coating is prevented from being passivated when the spring is placed in cold strong acid; another aspect is to speed up the reaction rate. However, if the reaction temperature is higher than the above range, the volatilization rate of ethanol and acetone is too high, which is not favorable for dissolving organic components in the anticorrosion protective layer, and if the temperature is lower than the above range, the plating layer has a risk of passivation, and the reaction speed is too low, which is not favorable for improving the detection efficiency.

In one possible embodiment, in step S3, the heat-treated spring is rinsed with deionized water to remove residual acid etching solution and the like on the surface of the spring.

In one possible embodiment, in step S3, the spring is straightened as much as possible by holding the two ends of the spring by the vise during the straightening operation.

In one possible embodiment, in step S3, the straightened spring is roughly ground with 100# sandpaper to roughly remove the remaining protective layer on the surface of the spring, and the surface of the spring is observed, at which time most of the protective layer is removed except for a small amount of the protective layer on the un-straightened portion of the spring, and then the spring is cut into small segments using a shearing machine to obtain spring segments, preferably with a length of less than 1cm, to meet the requirements of the subsequent tests.

In one possible embodiment, in step S4, the ultrasonic cleaning solution is prepared from hydrochloric acid, nitric acid, and absolute ethyl alcohol in a volume ratio of 5-10: 5-10: 80-90 (e.g., 6:7:85, 7:6:84, 8:9:89, 9:7:88, etc.); the hydrochloric acid concentration is 36 to 40 wt% (e.g., 36.5 wt%, 37 wt%, 37.5 wt%, 38 wt% 38.5 wt%, 39 wt%, 39.5 wt%, etc.), and the nitric acid concentration is 63 to 67 wt% (e.g., 63.5 wt%, 64 wt%, 64.5 wt%, 65 wt%, 65.5 wt%, 66 wt%, 66.5 wt%, etc.).

In a possible embodiment, in step S4, the ultrasonic oscillation time is 25-30 min (e.g., 26min, 27min, 28min, or 29min, etc.).

The surface of the spring section after coarse grinding treatment only has a small amount of protective layer residues, the protective layer residues can be thoroughly removed through ultrasonic oscillation treatment in ultrasonic cleaning liquid, the acid concentration in the ultrasonic cleaning liquid cannot be too high at the moment, so that surface passivation is prevented, acetone does not need to be added, and residual organic components can be removed through ethanol.

In one possible embodiment, the spring segments treated by ultrasonic vibration in step S5 are washed with absolute ethanol.

In a possible embodiment, in step S5, the spring segment after the rinsing treatment is placed in an oven for drying treatment at a temperature of 100 to 110 ℃ (e.g., 102 ℃, 105 ℃, 107 ℃ or 109 ℃, etc.) for 8 to 10min (e.g., 8.5min, 9min or 9.5min, etc.).

In a possible embodiment, in step S6, the detection of the carbon and sulfur content is performed by infrared absorption spectroscopy, and the detection step includes: placing a fluxing agent and a spring section in a crucible, and then detecting by adopting an infrared carbon sulfur instrument; the fluxing agent comprises tin particles, iron particles and tungsten particles.

In one possible embodiment, the tin, tungsten, etc. particles have a size of 0.8 to 1.4mm (e.g., 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, etc.), the iron particles have a size of 0.8 to 1.68mm (e.g., 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, etc.), and the C, S content of each of the tin, iron, and tungsten particles is no greater than 0.0005 wt%

In one possible embodiment, the mass ratio of the spring segment, the tin particles, the iron particles and the tungsten particles is as follows: 0.18-0.22: 0.15-0.25: 0.4-0.6: 1-2.

In one possible embodiment, the sequence of placing the flux, spring segments in the crucible is: and mixing tin particles and iron particles, placing the mixture at the bottom of a crucible, then placing the mixture into a spring section, and finally covering the spring section by adopting tungsten particles.

By selecting the tin particles, the iron particles and the tungsten particles according to a certain proportion as the fluxing agent, the method has the effects of fully combusting the sample and improving the detection precision. Iron particles are added into the fluxing agent, so that the temperature in the furnace body can be instantly increased, and the release of carbon and sulfur in a sample is ensured; wherein, if the adding proportion of the iron particles is too high, the molten material can be splashed too much, and if the adding proportion is too low, the sample can be burnt insufficiently, and the carbon and sulfur release is incomplete. The addition of tin particles to the flux lowers the melting point of the entire combustion system, and the addition of too much tin particles causes the formation of tin dioxide, which is a basic oxide, by oxidation of tin, resulting in a decrease in the measured sulfur value. The tungsten particles are added into the fluxing agent, the tungsten is easy to oxidize and emits a large amount of heat, and the effects of the tungsten particles are not only fluxing, but also multiple effects of heating, medium acid-base regulation, stirring, catalysis, stable combustion, interference resistance and the like. The spring section, the tin particles, the iron particles and the tungsten particles adopt the adding sequence, so that the quartz tube in the combustion chamber can be kept clean after the analysis is finished, no metal splashes on the ceramic thermal protection sleeve, and the analysis result is stable.

In one possible embodiment, the spring stock has a carbon content of: 0.24% to 0.9% by weight (e.g., 0.24%, 0.35%, 0.45%, 0.55%, 0.65%, 0.7%, 0.75%, 0.8%, or 0.85%, etc.), and a sulfur content of 0.002% to 0.030%. The spring steel grades suitable for the detection method are 65Mn, 55Si2M, 60Si2Mn and the like.

Compared with the prior art, the invention has the following effects:

1) the detection method can fully and effectively remove the anticorrosive protection layer on the surface of the spring steel, meets the detection requirement, and has stable and accurate detection result;

2) the acid etching solution fully utilizes the acidity and strong oxidizing property of hydrochloric acid and nitric acid to remove metal in a plating layer; the dissolving capacity of ethanol and acetone to organic matters is fully utilized to remove organic components in the anticorrosion protective layer;

3) in the acid etching process, by controlling the heating temperature, the reaction speed is accelerated while the passivation of the coating metal is prevented, the volatilization of ethanol and acetone is effectively inhibited, and the detection efficiency is improved;

4) the residual protective layer can be thoroughly removed by controlling the component ratio of the ultrasonic cleaning liquid;

5) when the infrared absorption spectrometry is adopted for detecting the content of carbon and sulfur, the composition and the adding sequence of the fluxing agent are controlled, and the adding sequence of the fluxing agent and the sample has great influence on the combustion effect and the splashing degree of the sample, so that the repeatability and the reproducibility of a detection result are influenced. When the sequence of the fluxing agent and the sample is tin particles, pure iron, the sample and tungsten particles, the sample is better wrapped in the fluxing agent, the combustion effect of the sample is good, the splashing is small, the carbon and sulfur in the spring steel sample can be completely released, and the detection result is stable and accurate.

Detailed Description

Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The method for treating the surface of the iron crucible for alkali fusion of the present application will be described in further detail with reference to examples.

< example 1>

A method for detecting the contents of carbon and sulfur in a spring comprises the following steps:

s1, preparing an acid etching solution; the acid etching solution is prepared from hydrochloric acid, nitric acid, absolute ethyl alcohol, acetone and deionized water according to a volume ratio of 15: 8: 15: 25: 35, the concentration of the hydrochloric acid is 38wt percent, and the concentration of the nitric acid is 65wt percent

S2, placing the spring in a beaker containing the acid etching solution, and heating at 60 ℃ for 30 min;

s3, taking out the spring after heating treatment, washing the spring by deionized water, straightening the spring by using bench clamp, polishing by using No. 100 abrasive paper, and cutting into small sections with the length of 0.5 cm;

s4, placing the spring section in an ultrasonic cleaning solution, and carrying out ultrasonic oscillation treatment for 28min, wherein the ultrasonic cleaning solution is prepared from hydrochloric acid, nitric acid and absolute ethyl alcohol according to a volume ratio of 8: 7:85 is configured; the concentration of the hydrochloric acid is 38 wt%, and the concentration of the nitric acid is 65 wt%;

s5, washing the spring section subjected to ultrasonic oscillation treatment by using absolute ethyl alcohol, and then placing the spring section in a drying oven for drying treatment at the drying temperature of 105 ℃ for 9 min;

s6, weighing 0.2g of spring section after drying treatment, placing the spring section in a ceramic crucible which is pre-filled with 0.2g of tin particles and 0.5g of iron particles, and covering 1.5g of tungsten particles; placing the crucible in an infrared carbon-sulfur instrument, and detecting the content of carbon and sulfur; the specific detection steps are as follows:

1. and (3) preheating the infrared carbon-sulfur instrument for 30 minutes by turning on a power supply, starting power gas and carrier gas, and detecting the air leakage of the equipment until the air leakage is detected to be passed after the air pressure is stable.

2. And (4) blank value measurement.

Weighing 1.000g +/-0.050 g of blank calibration sample (national certified standard substance with carbon and sulfur contents less than 0.001%), adding a selected amount of cosolvent, and accurately obtaining 5 mg. The analysis was performed on a carbon sulfur analyzer. 3 times of parallel analysis are carried out, and the content deviation of the results of the 3 times of analysis is less than 0.0005%. And performing blank correction on the instrument, wherein the blank value is the average value of the blank calibration samples minus the standard value of the blank calibration samples. The content of the blank carbon is not more than 0.002%.

3. Normalized correction

Weighing 0.2000g +/-0.005 g (accurate to 0.0001g) of carbon-sulfur standardized steel calibration sample, placing the calibration sample in a ceramic crucible which is pre-filled with 0.2g of tin particles and 0.5g of iron particles, and covering 1.5g of tungsten particles; the analysis was performed on a carbon sulfur analyzer. The measurement is carried out 3 times in parallel, the deviation of the measurement result needs to meet the precision requirement, and the average value of the 3 measurements is used for correction.

4. Control sample determination

Weighing 0.2000g +/-0.05 g (accurate to 0.0001g) of carbon-sulfur control sample, placing the carbon-sulfur control sample in a ceramic crucible which is pre-filled with 0.2g of tin particles and 0.5g of iron particles, and covering 1.5g of tungsten particles; the analysis was performed on a carbon sulfur analyzer. The analysis result should meet the accuracy requirement.

5. Measurement of a sample

Weighing 0.2000g +/-0.005 g (to the accuracy of 0.0001g) of sample, placing the sample in a ceramic crucible which is pre-filled with 0.2g of tin particles and 0.5g of iron particles, and covering 1.5g of tungsten particles; the analysis was performed on a carbon sulfur analyzer and 2 replicates were measured. The results of 2 times are reported as an average value if they meet the precision requirement, and the analysis of 3 rd time if they do not meet the requirement. The average value of 2 analyses with the precision meeting the requirement is reported, and if the precision of any 2 points can not meet the requirement, the result is reported as poor sample.

< example 2>

A method for detecting the contents of carbon and sulfur in springs, wherein the detected springs are in the same batch as in example 1, and the method comprises the following steps:

s1, preparing an acid etching solution; the acid etching solution is prepared from hydrochloric acid, nitric acid, absolute ethyl alcohol, acetone and deionized water according to the volume ratio of 10: 10: 20: 20: 55, the concentration of the hydrochloric acid is 40 wt%, and the concentration of the nitric acid is 63 wt%

S2, placing the spring in a beaker containing the acid etching solution, and heating at 65 ℃ for 25 min;

s3, taking out the spring after heating treatment, washing the spring by deionized water, straightening the spring by using bench clamp, polishing by using No. 100 abrasive paper, and cutting into small sections with the length of 0.5 cm;

s4, placing the spring section in an ultrasonic cleaning solution, and carrying out ultrasonic oscillation treatment for 25min, wherein the ultrasonic cleaning solution is prepared from hydrochloric acid, nitric acid and absolute ethyl alcohol according to a volume ratio of 5: 10: 90 is configured; the concentration of the hydrochloric acid is 40 wt%, and the concentration of the nitric acid is 63 wt%;

s5, washing the spring section subjected to ultrasonic oscillation treatment by using absolute ethyl alcohol, and then placing the spring section in a drying oven for drying treatment at the drying temperature of 100 ℃ for 10 min;

s6, weighing 0.22g of spring section after drying treatment, placing the spring section in a ceramic crucible which is pre-filled with 0.25g of tin particles and 0.6g of iron particles, and covering 2g of tungsten particles; placing the crucible in an infrared carbon-sulfur instrument, and detecting the content of carbon and sulfur; the specific detection procedure was the same as in example 1.

< example 3>

A method for detecting the contents of carbon and sulfur in springs, wherein the detected springs are in the same batch as in example 1, and the method comprises the following steps:

s1, preparing an acid etching solution; the acid etching solution is prepared from hydrochloric acid, nitric acid, absolute ethyl alcohol, acetone and deionized water according to a volume ratio of 20: 5: 10: 30: 20, the concentration of the hydrochloric acid is 36 wt%, and the concentration of the nitric acid is 67 wt%

S2, placing the spring in a beaker containing the acid etching solution, and heating at 55 ℃ for 35 min;

s3, taking out the spring after heating treatment, washing the spring by deionized water, straightening the spring by using bench clamp, polishing by using No. 100 abrasive paper, and cutting into small sections with the length of 0.5 cm;

s4, placing the spring section in an ultrasonic cleaning solution, and carrying out ultrasonic oscillation treatment for 30min, wherein the ultrasonic cleaning solution is prepared from hydrochloric acid, nitric acid and absolute ethyl alcohol according to a volume ratio of 10: 5: 80 are configured; the concentration of the hydrochloric acid is 36 wt%, and the concentration of the nitric acid is 67 wt%;

s5, washing the spring section subjected to ultrasonic oscillation treatment by using absolute ethyl alcohol, and then placing the spring section in a drying oven for drying treatment at the drying temperature of 110 ℃ for 8 min;

s6, weighing 0.18g of spring section after drying treatment, placing the spring section in a ceramic crucible which is pre-filled with 0.15g of tin particles and 0.4g of iron particles, and covering 1g of tungsten particles; placing the crucible in an infrared carbon-sulfur instrument, and detecting the content of carbon and sulfur; the specific detection procedure was the same as in example 1.

< example 4>

The springs were manufactured in the same batch as in example 1, and the detection method was different from that of example 1 in that the heat treatment temperature was 50 ℃ in step S2.

< example 5>

The springs were of the same lot as in example 1, and the detection method was different from that of example 1 in that the heat treatment temperature was 70 ℃ in step S2.

< example 6>

The springs were of the same batch as in example 1, and the detection method was different from that of example 1 in that, in step S4, the ultrasonic cleaning solution was prepared from hydrochloric acid, nitric acid, and absolute ethanol at a volume ratio of 7: 20: 80 are configured.

< example 7>

The springs were of the same lot as in example 1, and the detection method was different from that of example 1 in that the flux contained no iron particles in step S6.

Comparative example 1

The springs were of the same lot as in example 1, and the inspection method was different from example 1 in that the processing and inspection methods of steps S3 to S6 were directly adopted for the springs without the processing of steps S1 and S2.

Comparative example 2

The springs were manufactured in the same batch as in example 1, and the difference from example 1 is that, in step S2, the springs were not subjected to heat treatment after being placed in the acid etching solution.

Comparative example 3

The springs were manufactured in the same batch as in example 1, and the difference from example 1 is that the acid etching solution does not contain acetone in step S1.

Comparative example 4

The spring is the same batch as that of the example 1, and the difference from the example 1 is that in the step S1, the acid etching solution is prepared by mixing hydrochloric acid, nitric acid, absolute ethyl alcohol, acetone and deionized water according to a volume ratio of 15: 12: 15: 25: 35 are configured.

Comparative example 5

The spring is the same batch as that of the example 1, and the difference from the example 1 is that in the step S1, the acid etching solution is prepared by mixing hydrochloric acid, nitric acid, absolute ethyl alcohol, acetone and deionized water according to a volume ratio of 15: 8: 15: 35: 35 are configured.

Table 1 shows the results of measuring the C, S content in the springs of examples 1-7; table 2 shows the results of measuring the C, S content in the springs of comparative examples 1 to 5.

TABLE 1 results of C, S content test for examples 1-7

TABLE 2 detection results of C, S content in comparative examples 1 to 5

The detection result shows that:

comparing examples 1-7 with the standards, it can be seen that the C, S content measured by the test method of examples 1-7 is about the same as the C, S content of the standards.

Example 1 measured results closer to the actual content than examples 4-7; compared with example 1, in example 4, the heating temperature is slightly lower, so that the metal in the coating is partially passivated, the coating of the sample cannot be completely dissolved, and the carbon and sulfur measurement results are higher; in example 5, since the heating temperature is relatively high, ethanol and acetone are volatilized in the acid etching process, organic matters in the protective layer are not completely dissolved, the protective layer cannot be cleaned, and the measurement results of carbon and sulfur are relatively high; in example 6, since the acid concentration in the ultrasonic cleaning solution is relatively high, passivation of the metal surface layer is likely to occur to form an oxide film, which results in a reduction in the mass fraction ratio of carbon to sulfur in the same sample, thereby resulting in a relatively low detection result; in example 7, the flux does not contain iron particles, so that carbon and sulfur in the sample cannot be completely released, and the result of carbon and sulfur is slightly low.

Comparing example 1 with comparative examples 1-5, it can be seen that the C, S content measured in comparative examples 1-5 is significantly different from the C, S content in the standard.

Compared with the embodiment 1, the spring in the comparative example 1 is not subjected to acid etching by the acid etching solution, but is directly subjected to polishing treatment, so that the protective layer of the spring is not completely removed, and the measurement result is higher due to the fact that the detection sample contains carbon in the coating. After the spring in the comparative example 2 is placed in the acid etching solution, the metal in the coating is seriously passivated due to no heating treatment, so that the protective layer of the spring is not completely removed, and the measurement results of carbon and sulfur are higher; in comparative example 3, since the pickling solution contained no acetone, a large amount of organic matter in the plating layer was not dissolved, resulting in a high carbon and sulfur measurement result. In comparative example 4, the acid concentration of the acid etching solution was too high, and particularly, the content of nitric acid was too high, so that the metal in the plating layer was partially passivated, the spring protective layer was not removed completely, and the measurement results of carbon and sulfur were too high. In comparative example 5, the spring protection layer was not removed well due to the excessive acetone content in the pickling solution, and the measurement results of carbon and sulfur were high.

The foregoing is merely exemplary of the present application and is not intended to limit the present application, which may be modified or varied by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.