LU500705B1 - Rare Earth Steel Spectral Standard Sample and Preparation Method thereof - Google Patents

Abstract

The invention provides a rare earth steel spectral standard sample and a preparation method thereof. Firstly, placing a basis material in a magnesium crucible, adding rare earth after heating and melting, confirming the molten state, and then pouring the obtained molten steel into a casting mold to obtain a steel ingot; then, heating the obtained steel ingot, forging, slowly cooling to room temperature, homogenizing and annealing. Compared with the prior art, through the magnesium crucible and the preparation process design of the invention, the prepared rare earth steel sample has good chemical composition uniformity and high hit rate of rare earth content, and meets the requirements of rare earth steel spectral standard samples.

Description

DESCRIPTION LUS00705 Rare Earth Steel Spectral Standard Sample and Preparation Method thereof

TECHNICAL FIELD The invention belongs to the field of metallurgical analysis and testing, and particularly relates to a rare earth steel spectral standard sample and a preparation method thereof.

BACKGROUND Rare earth elements have the characteristics of intensive chemical activity, variable valence state of 4f shell and large atomic size, so they are important additives in metallurgical industry, and can be used as deep purificant of steel, modifier of inclusions as well as important microalloy elements of high value-added steel materials. In short, it is not only an effective method to improve the quality of steel, but also one of the important measures to develop new varieties of steel.

With the increasingly prominent role of rare earth elements in molten steel, the results show that the strength, toughness and corrosion resistance of steel can be improved by adding rare earth elements. Rare earth elements are expected to become an important element in the development of new high value-added steel materials in the 21st century, and one of the important ways to realize the upgrading of steel materials. Therefore, the application of rare earth in steel has been paid more and more attention by scholars and enterprises.

Accurate assignment of rare earth content in steel is one of the core technologies in the application research and production practice of rare earth in steel. Therefore, how to assign rare earth content in steel quickly and accurately is an important factor restricting rare earth steel. On-line analysis and testing methods in iron and steel production are mainly Cremation Direct Reading Spectrometry, but Cremation Direct Reading Spectrometry is a relative measurement method, which must be compared with corresponding standard samples. However, rare earth elements are extremely active in chemistry, have strong affinity for non-metallic elements such as oxygen and sulfur in steel and are easily burned during the preparation of standard samples, so they lead to poor uniformity of rare earth elements and low hit rate of rare earth 7500705 content in steel.

At present, there are relatively few standard samples for metallurgical analysis containing rare earth elements in China, moreover, they are temporarily unavailable in the market and have not been reported in domestic and foreign data. Therefore, it is imperative to develop rare earth steel spectral standard samples with good uniformity and high content hit rate.

SUMMARY In order to solve the above technical problems, the objective of the present invention is to provide a rare earth steel spectral standard sample and its preparation method, which can achieve good uniformity of chemical components in rare earth steel samples and high hit rate of rare earth content, and meet the requirements of rare earth steel spectral standard sample.

The specific technical scheme of that invention is as follow: The invention provides a preparation method of a rare earth steel spectral standard sample, which comprises the following steps: 1) placing a basis material in a magnesium crucible, adding rare earth after heating and melting, confirming the molten state, and then pouring the obtained molten steel into a casting mold to obtain a steel ingot; 2) heating the steel ingot obtained in step 1), forging, slowly cooling to room temperature, homogenizing and annealing.

Further, the magnesium crucible in step 1) comprises the following components in mass percent: Mg0>975%, Si0,<0.70%, Al03<0.10%, Ca0<1.10% and Fe»03<0.46%, and the balance is inevitable impurities.

Due to the active chemical properties of rare earth, it is easy to react with metallic and nonmetallic elements. As can be seen from figure 1, the AG of MgO is the smallest and has the best stability, which is far less than Y»0, CezO; and LarOs. At steelmaking temperature, Are203>Amgo. Therefore, when smelting rare earth steel, adopting Mg crucible can effectively prevent rare earth reaction and improve the yield of rare earth in steel.

After preparing the magnesium crucible, baking it at 800-1000°C for 30-40 min. 7500705 After baking the magnesia crucible, before preparing the rare earth steel spectrum standard sample, according to the composition requirements of the prepared rare earth steel spectrum standard sample, the furnace is washed with the steel of the steel grade without rare earth.

Preferably, the invention adopts an intermediate frequency induction melting furnace to refine the rare earth steel spectral standard sample, and in order to prevent the rare earth and rare earth compounds in the steel from reacting with the crucible and better control the rare earth yield, the magnesium crucible is adopted to smelt the rare earth steel spectral standard sample; baking the prepared crucible at 800-1000 °C for 30-40 min and cooling naturally. According to the requirements of the prepared steel grade, the furnace is washed with the steel of the steel grade without rare earth.

In step 1), the basis material refers to the collection of all other raw materials from which rare earth raw materials required by the prepared spectral standard sample are removed according to the steel grade of the rare earth steel.

In step 1), during adding rare earth, the yield of rare earth in steel is closely related to the kind and target content of rare earth. In a certain range, the yield of rare earth increases with the addition of rare earth. There are also some differences between light rare earth and heavy rare earth. For example, adding La, Ce, etc. in steel according to the yield corresponding to the target content of rare earth in steel, while calculating the yield of heavy rare earth according to the requirements of steel grade, and calculating the addition of other alloy components and pure iron. The purity of rare earth is required to be>99.5%.

Further, the yield of rare earth in steel is closely related to the kind and target content of rare earth. The most widely used rare earths in steel are light rare earths (lanthanum) La, cerium (Ce) and heavy rare earths yttrium(Y), the melting point and density of light rare earth lanthanum (La), cerium (Ce) and yttrium (Y) are 325°C,

6.187 g/em*, 757°C, 6.65 g/cm’ and 1478°C, 4.28 g/cm’ respectively. The melting point of heavy rare earth yttrium (Y) is much higher than that of light rare earth Lanthanum (La) and Cerium (Ce), but its density p is lower than that of light rare earth Lanthanum (La) and Cerium (Ce), which makes the oxidation burning loss of HUS00705 heavy rare earth yttrium (Y) greater than that of light rare earth lanthanum (La) and cerium (Ce) when the target content Wre of rare earth in the design steel is small (the addition amount of rare earth is also small), so as to leads to the yield of heavy rare earth yttrium (Y) being less than that of light rare earth lanthanum (La) and cerium (Ce). With the increase of target content Wre of rare earth in steel (adding amount of rare earth), due to the reaction speed and oxygen concentration, the burning loss of rare earth reaches a certain value, which is no longer increased with the increase of target content Wre of rare earth in steel (adding amount of rare earth), resulting in that the yields of heavy rare earth yttrium (Y), light rare earth lanthanum (La) and cerium (Ce) tend to be similar. Generally speaking, the yield of rare earth in steel increases with the increase of target content Wrg of rare earth in steel, and the yield of light rare earth is greater than that of heavy rare earth at the same Wre time of target content of rare earth in steel. For heavy rare earth, when the target content of rare earth in steel Wre<0.01%, the yield of rare earth in steel is 20-32%; when 0.01%<Wre<0.04%, the yield of rare earth in steel is 33-40%; then, when 0.04%<Wre<0.08%, the yield of rare earth in steel is 50-62%. For light rare earth, when the target content of rare earth in steel Wre<0.01%, the yield of rare earth in steel is 20-35%; when

0.01%<Wre<0.08%, the yield of rare earth in steel is 49-63%. The above-mentioned yield refers to the yield of rare earth elements after adding the rare earth with the purity>99.5% into molten steel.

According to the component design of the invention, the target component can be better hit, and the hit rate is high.

In step 1), heating and melting means: after adding and vacuumizing the furnace charge, smelting under the protective atmosphere of argon, and keeping vacuumizing during the smelting process; during smelting, firstly, heating with low current and low power of 2.5-5 KW/h, keeping the temperature for 15-20 min, drying moisture to prevent liquid droplets from splashing during melting; and then increasing the smelting power to 10-15 KW/h, so that the raw materials are heated and turn red; continuing to increase the power to 15-25 KW/h until the raw materials are melted. In the smelting process, if the upper furnace burden is difficult to melt due to the HUS00705 "bridging" phenomenon, the power can be continuously increased to eliminate the "bridging" phenomenon until it is completely melted; wherein the melting frequency is 3000-4000Hz, and the homogeneity of the standard sample is ensured by high temperature homogenization and electromagnetic stirring.

In step 1), the operation is as follows: firstly, cleaning the inner wall of the intermediate frequency induction melting furnace to ensure that the whole furnace body is clean and pollution-free, and placing a baked and washed magnesium crucible inside the furnace; then calculating the mixtures according to the experimental design, weighing the materials, putting the basis material into the crucible, and putting the rare earth into the silo. After vacuumizing, smelting under the protective atmosphere of argon, and keeping vacuumizing during the smelting process; during smelting, firstly, heating with low current and low power of 2.5-5 KW/h, keeping the temperature for 15-20 min, drying moisture to prevent liquid droplets from splashing during melting; and then increasing the smelting power to 10-15 KW/h, so that the raw materials are heated and turn red; continuing to increase the power to 15-25 KW/h until the raw materials are melted; keeping the vacuum degree at

5.0x102-6.67x10"'Pa, observing the melting turntable of the basis material, adding rare earth in the silo after the basis material is completely melted, keeping the temperature for 1.5-2.5 min, confirming the molten state, and pouring the molten steel into the corresponding mold.

In step 2), the forging specifically comprises following steps: firstly, cutting off risers at both ends of the head and tail of the steel ingot prepared in step 1), heating the steel ingot with the risers cut off in a heating furnace, and then forging.

In step 2), the heating specifically comprises as follows: the heating process is divided into three stages, that is, 750-800 °C, 950-1000°C and 1150-1200 °C respectively; and then the temperature is kept for 2-3 hours after reaching each temperature gradient.

In step 2), the specific technological parameters of forging are as follows: HUS00705 carrying out forging at 1100-1150°C in several times to prevent splitting until the thickness is 30-40 mm.

In step 2), after forging, sand is covered up in order to cooling slowly.

In step 2), in order to fully diffuse all elements in austenite, slow cooling to room temperature and then homogenizing annealing; In step 2), the homogenization annealing means: heating to 1100-1200°C at 5-10°C/s, keeping the temperature for 10-12 h, and cooling to room temperature along with the furnace. After homogenization heat treatment, eliminating dendritic segregation and regional segregation produced during solidification, and homogenizing the composition and structure.

Furthermore, after annealing, processing the forged and rolled test steel with qualified quality into block samples with the size of 38x30 mm by cutting, chamfering, polishing and ultrasonic cleaning (alcohol environment), which can be used for uniformity test.

The rare earth steel spectrum standard sample provided by the invention is prepared by the above method.

Compared with the prior art, through the magnesium crucible and the preparation process design of the invention, the prepared rare earth steel sample has good chemical composition uniformity and high hit rate of rare earth content, and meets the requirements of rare earth steel spectral standard samples.

BRIEF DESCRIPTION OF THE FIGURES Fig. 1 is the comparison of Gibbs free energy between MgO and rare earth.

DESCRIPTION OF THE INVENTION The invention provides a preparation method of a rare earth steel spectral standard sample, which comprises the following process flows: crucible preparation, baking, ingredient calculation and material preparation, smelting, adding rare earth, heat preservation, pouring, forging and rolling, sampling and processing, uniformity test, and analysis and determination of standard sample characteristic value; The specific steps are as follows:

1) Preparing and baking crucible: adopting an intermediate frequency induction HUS00705 melting furnace to refine the rare earth steel spectral standard sample, and in order to prevent the rare earth and rare earth compounds in the steel from reacting with the crucible and better control the rare earth yield, the magnesium crucible is adopted to smelt the rare earth steel spectral standard sample; baking the prepared crucible at 800-1000°C for 30-40 min and cooling naturally. According to the requirements of the prepared steel grade, the furnace is washed with the steel of the steel grade without rare earth. The crucible composition is shown in table 1, and the balance not shown in table 1 is inevitable impurities.

Table 1 Crucible composition (wt%) Chemical ; 2) Proportioning calculation and material preparation: the yield of rare earth in steel 1s closely related to the kind and target content of rare earth. In a certain range, the yield of rare earth increases with the addition of rare earth. There are also some differences between light rare earth and heavy rare earth. For example, adding La, Ce, etc. in steel according to the yield corresponding to the target content of rare earth in steel, while calculating the yield of heavy rare earth according to the requirements of steel grade; the yield of rare earth in steel is closely related to the kind and target content of rare earth. The most widely used rare earths in steel are light rare earths (lanthanum) La, cerium (Ce) and heavy rare earths yttrium (Y); for heavy rare earth, when the target content of rare earth in steel Wre<0.01%, the yield of rare earth in steel is 20-32%; when 0.01%<Wre<0.04%, the yield of rare earth in steel is 33-40%; then, when 0.04%<Wre<0.08%, the yield of rare earth in steel is 50-62%. For light rare earth, when the target content of rare earth in steel Wre<0.01%, the yield of rare earth in steel is 23-35%; when 0.01%<Wre<0.08%, the yield of rare earth in steel is 49-63%. The above-mentioned yield refers to the yield of rare earth elements after adding the rare earth with the purity>99.5% into molten steel.

3) Smelting: firstly, cleaning the inner wall of the intermediate frequency 7500705 induction melting furnace to ensure that the whole furnace body is clean and pollution-free, and placing a baked and washed magnesium crucible inside the furnace; then calculating the mixtures according to the experimental design, weighing the materials, putting the basis material into the crucible, and putting the rare earth into the silo. After vacuumizing, smelting under the protective atmosphere of argon, and keeping vacuumizing during the smelting process; during smelting, firstly, heating with low current and low power of 2.5-5 KW/h, keeping the temperature for 15-20 min, drying moisture to prevent liquid droplets from splashing during melting; and then increasing the smelting power to 10-15 KW/h, so that the raw materials are heated and turn red; continuing to increase the power to 15-25 KW/h until the raw materials are melted; in the smelting process, if the upper furnace burden is difficult to melt due to the "bridging" phenomenon, the power can be continuously increased to eliminate the "bridging" phenomenon until it is completely melted; wherein the melting frequency is 3000-4000Hz, and the homogeneity of the standard sample is ensured by high temperature homogenization and electromagnetic stirring; keeping the vacuum degree at 5.0x107-6.67x10"! Pa, observing the melting turntable of the basis material, adding rare earth in the silo after the basis material is completely melted, keeping the temperature for 1.5-2.5 min, confirming the molten state, and pouring the molten steel into the corresponding mold; after cooling, taking samples at 1/4 thickness, and measuring the rare earth content in steel by ICP-AES.

4) Forging and heat treatment: cutting off risers at both ends of the head and tail of the steel ingot prepared, heating the steel ingot with the risers cut off in a heating furnace, the heating process is divided into three stages, that is, 750-800 °C , 950-1000C and 1150-1200°C respectively; and then the temperature is kept for 2-3 hours after reaching each temperature gradient; carrying out forging at 1100-1150°C in several times to prevent splitting until the thickness is 30-40 mm; after forging, sand is covered up in order to cooling slowly. In order to fully diffuse all elements in austenite, slow cooling to room temperature and then homogenizing annealing;

heating to 1100-1200°C at 5-10°C/s, keeping the temperature for 10-12 h, and cooling 7500705 to room temperature along with the furnace. After homogenization heat treatment, eliminating dendritic segregation and regional segregation produced during solidification, and homogenizing the composition and structure.

5) Sampling and processing: processing the forged and rolled test steel with qualified quality into block samples with the size of 38x30 mm by cutting, chamfering, polishing and ultrasonic cleaning (alcohol environment), which can be used for uniformity test.

6) Uniformity test: According to the requirements of relevant standards of Carbon and low-alloy-steel-Determination of multi-element contents-Spark discharge atomic emission spectrometric method (routine method) (GB/T4336-2016), using the full spectrum spark direct reading spectrometer to dot and scan the surface of standard samples, marking each standard sample with 8 points, and taking the average value (x) after measuring the intensity ratio respectively, and judging the uniformity of the samples by the standard deviation (S) and relative standard deviation (RSD) of yttrium intensity ratio in the samples (such as formula 1 and formula 2); at the same time, inspecting the repeatability of yttrium intensity ratio in standard samples determined by spark direct reading spectroscopy, and checking the stability of data by calculating the standard uncertainty Ua 1) and relative standard uncertainty Urel(a 1) of repeatability test data (such as formula 3 and formula 4). During measuring, ensuring that the sample completely covers the electrode hole of spark table according to the test specification; if it is found that there is flame leakage or abnormal sound from the instrument during the excitation, it may lead to inaccurate data, so choose to discard it and try again. After the dotting test, if the color of the excitation point on the steel sample is abnormal, the source of the problem should be considered, and the dotting test should be carried out again after adjustment.

> (x, — x)” Standard deviation: S = (= (1)

Relative standard deviation: RSD = 5 x100% (2) x Standard uncertainty of repeatability test {J U = = (3) Relative standard uncertainty of repeatability test: gory Ü ren T = (4) In which: S: determination standard deviation of standard sample; N: determination times of a single sample, xi: single measurement value of rare earth intensity ratio; x : average value determined by standard sample.

The specific implementation process of that invention is as follows: Example 1 A preparation method of rare earth steel spectral standard sample comprises the following steps: 1) Preparing, baking crucible and washing furnace: adopting an intermediate frequency induction melting furnace to refine the rare earth steel spectral standard sample, and in order to prevent the rare earth and rare earth compounds in the steel from reacting with the crucible and better control the rare earth yield, the magnesium crucible is adopted to smelt the rare earth steel spectral standard sample; baking the prepared crucible at 800-1000°C for 30-40 min and cooling naturally. According to the requirements of the prepared steel grade, the furnace is washed with the steel of the steel grade without rare earth. The crucible composition is shown in table 2, and the balance not shown in table 2 is inevitable impurities.

Table 2 Crucible composition (wt%) | Mg0 | SiO: | ARO; | CaO | FeO: | mw [em [wn 2) Proportioning calculation and material preparation: the yield of rare earth in steel is closely related to the kind and target content of rare earth. In a certain range, the yield of rare earth increases with the addition of rare earth. There are also some differences between light rare earth and heavy rare earth. In this example, smelting 7 furnaces of rare earth steel containing yttrium, each furnace being 25 Kg; the chemical composition of the steel matrix of these 7 furnaces is shown in table 4. Preparing 7 kinds of spectral standard samples with different rare earth contents, in which the target components and rare earth addition amount are shown in table 3. The purity of rare earth should be>99.5%. Chemical composition of matrix (parent metal) and chemical composition of rare earth additive are shown in tables 4 and 5. The balance not listed in table 4 is Fe and inevitable impurities, and the balance not listed in table 5 is inevitable impurities. Table 3 Target Y content and rare earth Y addition amount in rare earth steel containing yttrium T t itl ECT COmPOSTOR | 0.003 | 0.005 | 001 | 002 | 0.04 0.08 (wt%) Additi t (8) The addition amount in table 3 refers to the addition amount of rare earth containing Y. Table 4 Chemical composition of basis material (wt%) Flem i ; ; ‘ C|Mn| Si |S Nb | V | Als | Ti | Alt| Cu | Ni |Mo| N | As en Cont 0.00 0.02 0.01 10.0005|0.026

0.11/0.14] 0.28 0.02 10.023/0.036/0.027/0.009 0.07 10.01 ent 3 8 1 6 8 Table 5 Chemical composition of yttrium additive in rare earth (wt%) Metallic ytrium| 999 | 002 | 003 | <001 | <001 | 0013 | 0017 3) Smelting: firstly, cleaning the inner wall of the intermediate frequency induction melting furnace to ensure that the whole furnace body is clean and pollution-free, and placing a baked and washed magnesium crucible inside the furnace; then calculating the mixtures according to the experimental design, weighing the materials, putting the basis material into the crucible, and putting the rare earth into HUS00705 the silo.

After vacuumizing, smelting under the protective atmosphere of argon, and keeping vacuumizing during the smelting process; during smelting, firstly, heating with low current and low power of 3 KW/h, keeping the temperature for 15 min, drying moisture to prevent liquid droplets from splashing during melting; and then increasing the smelting power to 10 KW/h, so that the raw materials are heated and turn red; continuing to increase the power to 15 KW/h until the raw materials are melted; in the smelting process, if the upper furnace burden is difficult to melt due to the "bridging" phenomenon, the power can be continuously increased to eliminate the "bridging" phenomenon until it is completely melted; wherein the melting frequency is 3000 Hz, and the homogeneity of the standard sample is ensured by high temperature homogenization and electromagnetic stirring; keeping the vacuum degree at 6.67x10 Pa, observing the melting turntable of the basis material, adding rare earth in the silo after the basis material is completely melted, keeping the temperature for 2 min, confirming the molten state, and pouring the molten steel into the corresponding mold; after cooling, taking samples at 1/4 thickness, and measuring the rare earth yttrium (Y) content in steel by ICP-AES.

The results are shown in table 6. Table 6 Target rare earth (Y) content and actual yttrium (Y) content in steel (ICP-AES) (wt%) | Target composition (We | 0.003 | 0005 | 001 | 002 | 004 0.06 | 00% | steel (Wacwa) (ICP-AES) [EEE lon ello The method for calculating the hit rate of the invention is as follows: Wiarget = actual Hit rate=1-——)x100% W target

4) Forging and heat treatment: cutting off risers at both ends of the head and tail of the steel ingot prepared, heating the steel ingot with the risers cut off in a heating furnace, the heating process is divided into three stages, that is, 800°C, 1000°C and HUS00705 1200°C respectively; and then the temperature is kept for 2 hours after reaching each temperature gradient; carrying out forging at 1100°C in several times to prevent splitting until the thickness is 30 mm; after forging, sand is covered up in order to cooling slowly; cooling to room temperature and then homogenizing annealing; heating to 1100°C at 10°C/s, keeping the temperature for 12 h, and cooling to room temperature along with the furnace. After homogenization heat treatment, segregation is eliminated.

5) Sampling and processing: processing the forged and rolled test steel with qualified quality into block samples with the size of 38x30 mm by cutting, chamfering, polishing and ultrasonic cleaning (alcohol environment), which can be used for uniformity test.

Uniformity test: According to the requirements of relevant standards of Carbon and low-alloy-steel-Determination of multi-element contents-Spark discharge atomic emission spectrometric method (routine method) (GB/T4336-2016), drawing the standard working curve needs to excite a series of standard samples, and each sample should be excited at least three times, and the average value of the measured results is taken. During measuring, ensuring that the sample completely covers the electrode hole of spark table according to the test specification; if it is found that there is flame leakage or abnormal sound from the instrument during the excitation, it may lead to inaccurate data, so choose to discard it and try again. After the dotting test, if the color of the excitation point on the steel sample is abnormal, the source of the problem should be considered, and the dotting test should be carried out again after adjustment. In this experiment, selecting 7 standard samples prepared in example 1, and taking at least 8 effective points on each standard sample, and taking the average value (x) after measuring the intensity ratio respectively, as shown in table 7; judging the uniformity of the samples by the standard deviation (S) and relative standard deviation (RSD) of yttrium intensity ratio in the samples (such as formula 5 and formula 6), as shown in table 8; at the same time, inspecting the repeatability of

. . . a . . . LU500705 yttrium (Y) intensity ratio in standard samples determined by spark direct reading spectroscopy, and checking the stability of data by calculating the standard uncertainty Uça,1) and relative standard uncertainty Urela 1) of repeatability test data (such as formula 7 and formula 8), the calculation results are shown in table 9: > (x a x)’ Standard deviation: S = IEP (5) n — . i. S ° Relative standard deviation: RSD =— x100% (6) x . a 3 Standard uncertainty of repeatability test IJ U = — (7)

N . . 24. 5 Relative standard uncertainty of repeatability test: gun: Une = (8) In which: S: determination standard deviation of standard sample; N: determination times of a single sample, xi: single measurement value of rare earth yttrium (Y) intensity ratio; x: average value determined by standard sample. Table 7 Standard deviation (Sy) and relative standard deviation (RSDy) of intensity ratio (xi) and average intensity ratio (x) of yttrium Sampl number 46468 | 48723 | 135919 | 256769 | 518965 | 752349 | 976484 45523 51037 | 145733 | 271436 | 529355 | 756412 | 969670 44938 | 50775 | 138602 | 262961 | 492971 | 749709 | 1013100 45960 | 48753 | 142141 | 268541 | 530070 | 770130 | 1010319 43869 | 48951 | 143021 | 253964 | 518649 | 758195 | 997395 47964 | 49519 | 136541 | 257743 | 529535 | 749091 | 971690 44973 | 48739 | 151171 | 259415 | 530900 | 760953 | 969596 45951 50253 | 141299 | 263643 | 512184 | 741562 | 983379 i 754800.12 | 986454.1 x 45705.75 | 49593.75 141804 261809 520328.625 5 25

Table 8 Standard deviation (Sy) and relative standard deviation (RSDy) of intensity ratio of yttrium Sample 1# 2# 3# 44 5# 6# 7# number S 1136.8222 | 903.27954 5037 5998.7954 | 12208.277 | 8114.46151 | 16926.23 " 98 56 74 51 1 726

2.4872631 | 1.8213576 2.2912869 | 2.3462629 | 1.07504771 | 1.715866 RSDy (%) 3.55 96 22 59 04 7 641 Table 9 Standard uncertainty Uy and relative standard uncertainty Ugeny of yttrium intensity ratio Sample 1# 2# 3# 5# 6# 7# 8# number

401.92737 | 319.35754 | 1780.8484 | 92563.459 | 4316.2779 5984328 Uy 2868.89538 8 6 28 63 06 574 U 0.0087938 | 0.0064394 | 0.0125585 | 0.3510939 | 0.0082952 | 0.00380086 | 0.006066 ey 03 72 2 4 92 8 505 With reference to Carbon and low-alloy-steel-Determination of multi-element contents-Spark discharge atomic emission spectrometric method (routine method) (GB/T4336-2016), the relative standard deviation (RSD) 1s less than 5% and the relative standard uncertainty is less than 1. According to the data in table 8, the uniformity is preliminarily judged, and it can be seen that the relative standard deviation (RSD) is less than 5%, which accords with the requirement that the absolute value between the two test results meets the probability of not exceeding 95% under the conditions of repeatability and reproducibility. The relative standard uncertainty values in table 9 are all small and far less than 1, meeting the condition of less than 1, which shows that the fluctuation of intensity ratio at 8 points on each standard sample is small, that 1s, the refined standard sample has good uniformity and reaches the standard of standard sample. Example 2 A preparation method of rare earth steel spectral standard sample comprises the following steps:

1) Preparing, baking crucible and washing furnace: adopting an intermediate frequency induction melting furnace to refine the rare earth steel spectral standard sample, and in order to prevent the rare earth and rare earth compounds in the steel from reacting with the crucible and better control the rare earth yield, the magnesium crucible is adopted to smelt the rare earth steel spectral standard sample; baking the prepared crucible at 900°C for 35 min and cooling naturally. According to the requirements of the prepared steel grade, the furnace is washed with the steel of the steel grade without rare earth. The crucible composition is shown in table 10, and the balance not shown in table 10 is inevitable impurities.

Table 10 Crucible composition (wt%) | Mg0 | SiO: | ARO; | CaO | FeO: |

M pe 98.4 0.40 0.0870 03 (magnesium) 2) Proportioning calculation and material preparation: the yield of rare earth in steel is closely related to the kind and target content of rare earth. In a certain range, the yield of rare earth increases with the addition of rare earth. There are also some differences between light rare earth and heavy rare earth. In this example, smelting 7 furnaces of rare earth steel containing lanthanum (La), each furnace being 25 Kg; preparing 7 kinds of spectral standard samples with different rare earth contents, in which the target components and rare earth addition amount are shown in table 11. The purity of rare earth should be>99.5%. Parent metal and chemical composition of rare earth additive are shown in tables 12 and 13. The balance not listed in table 12 is Fe and inevitable impurities, and the balance not listed in table 13 is inevitable impurities.

Table 11 Lanthanum (La) content and lanthanum (La) addition in rare earth steel containing lanthanum Tr om [a Jo on (wt%) (8) The addition amount in table 11 refers to the addition amount of rare earth containing La.

Table 12 Chemical composition of parent metal (wt%) "men | [wo |v [5 [wa] v [em [a] onen | 08 3 pr — mp] — Table 13 Chemical composition of lanthanum (La) additive in rare earth (wt%)

3) Smelting: firstly, cleaning the inner wall of the intermediate frequency induction melting furnace to ensure that the whole furnace body is clean and pollution-free, and placing a baked and washed magnesium crucible inside the furnace; then calculating the mixtures according to the experimental design, weighing the materials, putting the basis material into the crucible, and putting the rare earth into the silo.

After vacuumizing, smelting under the protective atmosphere of argon, and keeping vacuumizing during the smelting process; during smelting, firstly, heating with low current and low power of 4 KW/h, keeping the temperature for 18 min, drying moisture to prevent liquid droplets from splashing during melting; and then increasing the smelting power to 13 KW/h, so that the raw materials are heated and turn red; continuing to increase the power to 20 KW/h until the raw materials are melted; in the smelting process, 1f the upper furnace burden 1s difficult to melt due to the "bridging" phenomenon, the power can be continuously increased to eliminate the

"bridging" phenomenon until it is completely melted; wherein the melting frequency 7500705 is 3500 Hz, and the homogeneity of the standard sample is ensured by high temperature homogenization and electromagnetic stirring; keeping the vacuum degree at 6.67x10 Pa, observing the melting turntable of the basis material, adding rare earth in the silo after the basis material is completely melted, keeping the temperature for 2 min, confirming the molten state, and pouring the molten steel into the corresponding mold; after cooling, taking samples at 1/4 thickness, and measuring the rare earth lanthanum (La) content in steel by ICP-AES. The results are shown in table

14.

Table 14 Rare earth (La) target content in steel and actual rare earth (La) content in steel (ICP-AES) | Target composition (We _| 0.003 | 0.005 | 001 | 0.02 | 004 0.06 | 008 [ERE os vn oo a oma steel CWactuai) (ICP-AES) [EE elim nlm enon [a 4) Forging and heat treatment: cutting off risers at both ends of the head and tail of the steel ingot prepared, heating the steel ingot with the risers cut off in a heating furnace, the heating process is divided into three stages, that is, 800°C, 1000°C and 1200°C respectively; and then the temperature is kept for 2.5 hours after reaching each temperature gradient; carrying out forging at 1130°C in several times to prevent splitting; after forging, sand is covered up in order to cooling slowly; cooling to room temperature and then homogenizing annealing; heating to 1100°C at 10°C/s, keeping the temperature for 12 h, and cooling to room temperature along with the furnace. After homogenization heat treatment, segregation is eliminated.

5) Sampling and processing: processing the forged and rolled test steel with qualified quality into block samples with the size of 38x30 mm by cutting, chamfering, polishing and ultrasonic cleaning (alcohol environment), which can be used for uniformity test.

Uniformity test: According to the requirements of relevant standards of Carbon HUS00705 and low-alloy-steel-Determination of multi-element contents-Spark discharge atomic emission spectrometric method (routine method) (GB/T4336-2016), drawing the standard working curve needs to excite a series of standard samples, and each sample should be excited at least three times, and the average value of the measured results is taken.

During measuring, ensuring that the sample completely covers the electrode hole of spark table according to the test specification; if it is found that there is flame leakage or abnormal sound from the instrument during the excitation, it may lead to inaccurate data, so choose to discard it and try again.

After the dotting test, if the color of the excitation point on the steel sample is abnormal, the source of the problem should be considered, and the dotting test should be carried out again after adjustment.

In this experiment, selecting 7 standard samples prepared in example 2, and taking at least 8 effective points on each standard sample, and taking the average value (x) after measuring the intensity ratio respectively, as shown in table 15; judging the uniformity of the samples by the standard deviation (S) and relative standard deviation (RSD) of lanthanum (La) intensity ratio in the samples (such as formula 1 and formula 2), as shown in table 16; at the same time, inspecting the repeatability of lanthanum (La) intensity ratio in standard samples determined by spark direct reading spectroscopy, and checking the stability of data by calculating the standard uncertainty Uça,1) and relative standard uncertainty Urela 1) of repeatability test data (such as formula 3 and formula 4), the calculation results are shown in table 17: > (x, — x)” Standard deviation: S = (= (9) Relative standard deviation: RSD = 5 x100% (10) x Standard uncertainty of repeatability test {J U = = (11) Relative standard uncertainty of repeatability test: gory Ü ren T = (12)

a 2, a LU500705 In which: S: determination standard deviation of standard sample; N: determination times of a single sample, xi: single measurement value of rare earth lanthanum (La) intensity ratio; x: average value determined by standard sample. Table 15 Intensity ratio (xi) and average intensity ratio (x ) of lanthanum (La) Sample 1# 2# 3# 4# 5# G# T# number 11824 | 27176 | 44902 X1 30327 | 36013 5 8 1 643125 | 30327 11254 | 28013 | 45926 X2 29578 | 35016 594773 | 29578 0 2 9 11701 | 27523 | 45470 X3 29779 | 33947 > 1 9 677813 | 29779 11283 | 28011 | 45183 X4 31049 | 34394 629237 | 31049 9 7 2 10947 | 27814 | 42456 X5 29298 | 35137 603811 | 29298 7 3 8 11301 | 27501 | 42982 X6 32190 | 36103 619717 | 32190 0 2 6 11107 | 29017 | 44380 X7 29556 | 35095 625321 | 29556 1 2 0 11019 | 27306 | 43967 X8 29328 | 34986 632162 | 29328 3 9 4 _ 30138. | 35086. | 11304 | 27795 | 44408 | 628244. | 30138 X 125 375 8.375 55 7.375 875 125 Table 16 Standard deviation (Sra) and relative standard deviation (RSDL,) of intensity ratio of lanthanum (La) Sample 1# 2# 3# 4# 5# G# T# number

949.9

949.95 | 725.78 | 3113.0 | 5442.1 | 11355. | 23699.6 SLa 50714 07142 | 86228 | 3453 6632 | 47119 8269 5

3.151 RSD1a | 3.1519 | 2.0685 | 2.7537 | 1.9579 | 2.5570 | 3.77236 99009 (%) 90093 | 76827 | 18954 | 27193 | 35356 3872 3

Table 17 Standard uncertainty Ur, and relative standard uncertainty UcrenLa of lanthanum (La) intensity ratio Sample 82959 | 50284 | 63628 | 96354 | 65341 317 82959 43968 | 13524 | 14839 | 22318 | 40485 732 | 43968 With reference to Carbon and low-alloy-steel-Determination of multi-element contents-Spark discharge atomic emission spectrometric method (routine method) (GB/T4336-2016), the relative standard deviation (RSD) 1s less than 5% and the relative standard uncertainty is less than 1. According to the data in table 16, the uniformity is preliminarily judged, and it can be seen that the relative standard deviation (RSD) is less than 5%, which accords with the requirement that the absolute value between the two test results meets the probability of not exceeding 95% under the conditions of repeatability and reproducibility. The relative standard uncertainty values in table 17 are all small and far less than 1, meeting the condition of less than 1, which shows that the fluctuation of intensity ratio at 8 points on each standard sample is small, that is, the refined standard sample has good uniformity and reaches the standard of standard sample.

Example 3 A preparation method of rare earth steel spectral standard sample comprises the following steps: 1) Preparing, baking crucible and washing furnace: adopting an intermediate frequency induction melting furnace to refine the rare earth steel spectral standard sample, and in order to prevent the rare earth and rare earth compounds in the steel from reacting with the crucible and better control the rare earth yield, the magnesium crucible is adopted to smelt the rare earth steel spectral standard sample; baking the prepared crucible at 1000°C for 40 min and cooling naturally. According to the requirements of the prepared steel grade, the furnace is washed with the steel of the steel grade without rare earth. The crucible composition is shown in table 18, and the balance not shown in table 18 is inevitable impurities.

Table 18 Crucible composition (wt%) Two | so | abo ] Go | reo |

M pe 97.7 0.67 0.092 1.0 0.5 (magnesium) 2) Proportioning calculation and material preparation: the yield of rare earth in steel is closely related to the kind and target content of rare earth. In a certain range, the yield of rare earth increases with the addition of rare earth. There are also some differences between light rare earth and heavy rare earth. In this example, smelting 7 furnaces of rare earth steel containing cerium (Ce), each furnace being 25 Kg; preparing 7 kinds of spectral standard samples with different rare earth contents, in which the target components and rare earth addition amount are shown in table 19. The purity of rare earth should be>99.5%. Parent metal and chemical composition of rare earth additive are shown in tables 20 and 21. The balance not listed in table 20 is Fe and inevitable impurities, and the balance not listed in table 21 is inevitable impurities.

Table 19 Cerium (Ce) content and cerium (Ce) addition in rare earth steel containing cerium Target composition

0.003 0.005 0.01 0.02 0.04 0.1 (Wt%) Addition amount

0.025 0.04 0.05 0.1 0.2 0.5 (2) The addition amount in table 19 refers to the addition amount of rare earth containing cerium (Ce).

Table 20 Chemical composition of parent metal (wt%) eon ] [wa] [+ | s [oo] v [we] 0 [or coon [nr 1 [04 portooefos port —| —

Table 21 Chemical composition of cerium (Ce) additive in rare earth (wt%)

Metallie cern] 99.9 120.01 =0.01/=0.01[=0.01<0.010.014/0.064<0.010.018

3) Smelting: firstly, cleaning the inner wall of the intermediate frequency induction melting furnace to ensure that the whole furnace body is clean and pollution-free, and placing a baked and washed magnesium crucible inside the furnace; then calculating the mixtures according to the experimental design, weighing the materials, putting the basis material into the crucible, and putting the rare earth into the silo.

After vacuumizing, smelting under the protective atmosphere of argon, and keeping vacuumizing during the smelting process; during smelting, firstly, heating with low current and low power of 5 KW/h, keeping the temperature for 20 min, drying moisture to prevent liquid droplets from splashing during melting; and then increasing the smelting power to 15 KW/h, so that the raw materials are heated and turn red; continuing to increase the power to 25 KW/h until the raw materials are melted; in the smelting process, if the upper furnace burden is difficult to melt due to the "bridging" phenomenon, the power can be continuously increased to eliminate the "bridging" phenomenon until it is completely melted; wherein the melting frequency is 4000 Hz, and the homogeneity of the standard sample is ensured by high temperature homogenization and electromagnetic stirring; keeping the vacuum degree at 6.67x10 Pa, observing the melting turntable of the basis material, adding rare earth in the silo after the basis material is completely melted, keeping the temperature for 2 min, confirming the molten state, and pouring the molten steel into the corresponding mold; after cooling, taking samples at 1/4 thickness, and measuring the rare earth cerium (Ce) content in steel by ICP-AES.

The results are shown in table 22.

Table 22 Rare earth cerium (Ce) target content in steel and actual rare earth HUS00705 cerium (Ce) content in steel (ICP-AES) in steel (Wactua) ICP-AES) 4 2 Leg [0 | m [ww [w | 1) 4) Forging and heat treatment: cutting off risers at both ends of the head and tail of the steel ingot prepared, heating the steel ingot with the risers cut off in a heating furnace, the heating process is divided into three stages, that is, 800°C, 1000°C and 1200°C respectively; and then the temperature is kept for 3 hours after reaching each temperature gradient; carrying out forging at 1150°C in several times to prevent splitting until the thickness is 40 mm; after forging, sand is covered up in order to cooling slowly; cooling to room temperature and then homogenizing annealing; heating to 1100°C at 10°C/s, keeping the temperature for 12 h, and cooling to room temperature along with the furnace. After homogenization heat treatment, segregation is eliminated.

5) Sampling and processing: processing the forged and rolled test steel with qualified quality into block samples with the size of 38x30 mm by cutting, chamfering, polishing and ultrasonic cleaning (alcohol environment), which can be used for uniformity test.

Uniformity test: According to the requirements of relevant standards of Carbon and low-alloy-steel-Determination of multi-element contents-Spark discharge atomic emission spectrometric method (routine method) (GB/T4336-2016), drawing the standard working curve needs to excite a series of standard samples, and each sample should be excited at least three times, and the average value of the measured results is taken. During measuring, ensuring that the sample completely covers the electrode hole of spark table according to the test specification; if it is found that there is flame leakage or abnormal sound from the instrument during the excitation, it may lead to inaccurate data, so choose to discard it and try again. After the dotting test, if the color a . . LU500705 of the excitation point on the steel sample 1s abnormal, the source of the problem should be considered, and the dotting test should be carried out again after adjustment. In this experiment, selecting 7 standard samples prepared in example 3, and taking at least 8 effective points on each standard sample, and taking the average value (x) after measuring the intensity ratio respectively, as shown in table 23; judging the uniformity of the samples by the standard deviation (S) and relative standard deviation (RSD) of cerium (Ce) intensity ratio in the samples (such as formula 13 and formula 14), as shown in table 24; at the same time, inspecting the repeatability of cerium (Ce) intensity ratio in standard samples determined by spark direct reading spectroscopy, and checking the stability of data by calculating the standard uncertainty Uça,1) and relative standard uncertainty Urela 1) of repeatability test data (such as formula 15 and formula 16), the calculation results are shown in table 25: D(x, = x) Standard deviation: S = PTE (13) n — Relative standard deviation: RSD = 5 x100% (14) x . 2 S Standard uncertainty of repeatability test IJ U = — (15)

V i. 5 Relative standard uncertainty of repeatability test: Uran Une = (16) In which: S: determination standard deviation of standard sample; N: determination times of a single sample, xi: single measurement value of rare earth cerium (Ce) intensity ratio; x : average value determined by standard sample.

Table 23 Intensity ratio (xi) and average intensity ratio (x ) of cerium (Ce) Sample 1# 2# 3# 44 5# 6# number 9508 10545 17489 | 57310 | 91874 9508 9250 10799 18369 | 52973 | 92198 9250 9472 10929 17146 | 51873 89729 9472 9727 10297 17683 52940 | 95909 9727 9328 10614 18184 | 54315 89571 9328 9920 10689 17304 | 56013 86431 9920 9186 10508 18198 53736 | 89547 | 9186 9187 10633 17496 | 56851 87196 9187 9447 10627 17734 54501.375 | 90306.875 9447 Table 24 Standard deviation (Sce) and relative standard deviation (RSDce) of intensity ratio of cerium (Ce) Sample 1# 2# 3# 44 5# 6# number

1870.7229 | 2818.8838 Sce 266 191 459 266 18 85

3.4324325 | 3.1214499 RSDce (%) 2.82 1.79 2.59 2.82 17 29 Table 25 standard uncertainty Uce and relative standard uncertainty Utrence of cerium (ce) intensity ratio Sampl number U 94.045201 | 67.528697 | 162.28100 | 661.40043 | 996.62595 | 94.04520 © 89 6 63 03 53 189 U 0.0099550 | 0.0063544 | 0.0091508 | 0.0121354 | 0.0110359 | 0.009955 renee 34 46 41 82 92 034 With reference to Carbon and low-alloy-steel-Determination of multi-element contents-Spark discharge atomic emission spectrometric method (routine method) (GB/T4336-2016), the relative standard deviation (RSD) is less than 5% and the relative standard uncertainty is less than 1. According to the data in table 24, the uniformity is preliminarily judged, and it can be seen that the relative standard deviation (RSD) is less than 5%, which accords with the requirement that the absolute value between the two test results meets the probability of not exceeding 95% under HUS00705 the conditions of repeatability and reproducibility.

The relative standard uncertainty values in table 25 are all small and far less than 1, meeting the condition of less than 1, which shows that the fluctuation of intensity ratio at 8 points on each standard sample is small, that is, the refined standard sample has good uniformity and reaches the standard of standard sample.

Claims (10)

CLAIMS LU500705

1. A preparation method of rare earth steel spectral standard sample is characterized by comprising the following steps: 1) placing a basis material in a magnesium crucible, adding rare earth after heating and melting, confirming the molten state, and then pouring the obtained molten steel into a casting mold to obtain a steel ingot; 2) heating the steel ingot obtained in step 1), forging, slowly cooling to room temperature, homogenizing and annealing.

2. The preparation method according to claim 1 is characterized in that the magnesium crucible in step 1) comprises the following components in mass percent: Mg0>97.5%, Si02<0.70%, Al»03<0.10%, CaO<1.10% and Fe»03<0.46%, and the balance is inevitable impurities.

3. The preparation method according to claim 1 or 2 is characterized in that after preparing the magnesium crucible, baking it at 800-1000°C for 30-40 min.

4. The preparation method according to claim 1 is characterized in that the method of adding rare earth in step 1) is as follows: for heavy rare earth, when the target content of rare earth in steel Wre<0.01%, the yield of rare earth in steel is 20-32%; when 0.01%<Wgrg<0.04%, the yield of rare earth in steel is 33-40%; then, when 0.04%<Wgg<0.08%, the yield of rare earth in steel is 50-62%; for light rare earth, when the target content of rare earth in steel Wre<0.01%, the yield of rare earth in steel is 20-35%; when 0.01%<Wre<0.08%, the yield of rare earth in steel is 49-63%.

5. The preparation method according to claim 1 is characterized in that the heating and melting in step 1) specifically comprises: after adding and vacuumizing the furnace charge, smelting under the protective atmosphere of argon, and keeping vacuumizing during the smelting process; during smelting, firstly, heating with low current and low power of 2.5-5 KW/h, keeping the temperature for 15-20 min, and then increasing the smelting power to 10-15 KW/h, so that the raw materials are heated and turn red; continuing to increase the power to 15-25 KW/h until the raw HUS00705 materials are melted.

6. The preparation method according to claim 1 or 4 is characterized in that the heating in step 2) specifically comprises: the heating process is divided into three stages, that is, 750-800°C, 950-1000°C and 1150-1200°C respectively; then, the temperature is kept for 2-3 hours after reaching each temperature gradient.

7. The preparation method according to claim 1 or 6 is characterized in that the specific technological parameters of forging in step 2) are as follows: carrying out forging at 1100-1150°C in several times to prevent splitting until the thickness is 30-40 mm.

8. The preparation method according to claim 1 is characterized in that the slow cooling is carried out by covering up sand.

9. The preparation method according to claim 1 is characterized in that the homogenization annealing means: heating to 1100-1200°C at 5-10°C/s, keeping the temperature for 10-12 h, and cooling to room temperature along with the furnace.

10. The rare earth steel spectral standard sample prepared by the preparation method according to any one of claims 1 to 9.