CN106018728A - Quantitative evaluating method for square billet center macrosegregation - Google Patents

Abstract

A quantitative evaluating method for square billet center macrosegregation belongs to the technical field of metallurgical analysis. The quantitative evaluating method comprises the steps of finding out a solidifying physical center of a casting blank through a hot acid etching method; taking samples of 5 points through drilling, taking 3-5g per point and measuring the soluble element concentration of different positions to serve as evaluating basis of macrosegregation; using a data analyzing method to evaluate a center segregation average value and standard deviation according to segregation data of different samples and reflecting the quality controlling level and the controlling stability in a billet. The quantitative evaluating method has the advantages of accurately finding out the actual solidifying physical center of the casting blank, avoiding casting blank center segregation analysis result deviation caused by sampling position factors and providing accurate reference for quality monitoring or technique improvement.

Description

A kind of method for quantitatively evaluating of square billet center gross segregation

Technical field

The invention belongs to metallurgical analysis technical field, particularly to the quantitative assessment side of a kind of square billet center gross segregation Method.

Background technology

Due to molten steel choosing point crystallization and dendritic solidification characteristic, strand will gather because of solute in the centre line zone of final set It is inevitably generated center segregation defect with MOLTEN STEEL FLOW feeding difficulty.

The method of the control level evaluating the gross segregation of strand center is divided into qualitative evaluation and quantitative assessment, qualitative evaluation master Macrostructure to be passed through and fault detection, the most employing hot acid etching methods, cold acid corrosion method or electrolytic etching method carry out strand The qualitative evaluation of low multiple quality.The examined standard of this qualitative evaluating method, the impact of testing staff's subjective judgment factor, it is evaluated Result is more rough, only can be as casting blank defect or the monitoring means of production stability, it is impossible to provide center macroscopic view accurately Segregation is evaluated, it is impossible to the raising for continuous casting process or mill bar quality provides accurate reference.

Quantitative assessment includes the means such as drilling chemical analysis, in-situ study, electron probe.Wherein, in-situ study, electronics are visited Stitch means is the most more and more applied in the evaluation of continuous casting slab segregation, is then subjected to testing cost, ageing and detection The impact of accuracy, further popularization and application are by a definite limitation.

The chemico-analytic application of drilling is the most ripe, has an advantage in that detection accuracy is high, cost is relatively low, but there is also Certain problem, such as sample position are more random, at present and have no unified regulation.Wherein, for square billet, in strand The drill position of the heart is particularly important to the evaluation result of center gross segregation, and the geometric center of the most employing strands is as drilling Sample point, and do not take into account the situation that actual solidification physical centre is inconsistent with geometric center.

Under the conditions of preferably cooling technique, the geometric center of strand should should be consistent with the physical centre of reality solidification 's.Then, in actual production process, unreasonable, quality of cooling water, casting are set by spray nozzle clogging, spraying rack deformation, cooling technique The impact of the factors such as base off-square, the actual physics center of casting blank solidification is often inevitable and geometric center produces deviation.If Do not consider the impact of sample position, the reliability of check analysis result certainly will be affected.

Summary of the invention

It is an object of the invention to provide the method for quantitatively evaluating of a kind of square billet center gross segregation, solve current little side During base Central Carbon Segregation detection by quantitative, sample position there may be deviation, drilling chemical analysis with actual solidification physical centre The problem that result may be forbidden.Square billet section includes small billet and bloom.

A kind of method for quantitatively evaluating of square billet center gross segregation, concrete steps and parameter are as follows:

1) the solidification physical centre of strand, the i.e. concrete position of final set in cross section is found out by hot acid etching method Put.First strand is processed into 10～20mm thickness coarse micro-grain samples, uses volume ratio 1:1 technical hydrochloric acid aqueous solution to carry out etch examination Testing, aqueous hydrochloric acid solution temperature need to be heated to 60～80 DEG C, the etch time 15～30min, then washes down with water and dries up.The most available The macrostructure situation of strand, finds final set position in the solidification physical centre of strand cross section, i.e. strand cross section.

2) carrying out drilling sampling on strand cross section, 3～5g/ every point, totally 5 sample points, sampling particular location is respectively Be the 1st at strand cross section wherein one article of diagonal inner arc side 1/4, the 2nd in line of symmetry inner arc side, slab thickness direction At 1/4, the 3rd in casting blank solidification physical centre, the 4th at line of symmetry inner arc side, slab thickness direction 1/4, the 5th with At first same diagonal outer arc side 1/4.Infrared carbon sulfur analyzer is used to measure various location solute element concentration, every point Detect 3 times, average, be respectively As grand Seeing the Appreciation gist of segregation, solute element during wherein i is steel, j is strand coarse micro-grain sample block number.For ensureing precision of analysis and subtracting Little more bit change number of times, uses the φ 5mm drill bit heart to carry out drilling sampling, for avoiding surface oxidation corrosion layer to dividing in sampling process Analysis result impact, first drills through casting billet surface oxide etch layer 1～2mm and removes, and sample position parent metal color need to occurs, and clear up Further drilling analysis sample after Gan Jing.

3) according to the segregation data of different samples, means of numerical analysis assessment centers segregation meansigma methods and standard are used Difference, reflection Inner Quality of Billet controls level and control stability.The calculating of coarse micro-grain sample center gross segregation index is concrete Formula is:

${\mathrm{CSI}}_i^j=\frac{{\mathrm{Content}}_{i-3}^j}{Average({\mathrm{Content}}_{i-1}^j,{\mathrm{Content}}_{i-2}^j,{\mathrm{Content}}_{i-4}^j,{\mathrm{Content}}_{i-5}^j)}$

Wherein,It is the 1st, 2,4,5 Point i element meansigma methods.

According to same heat or the center segregation index of the different coarse micro-grain samples of same flow time strand, data statistics is used to divide Analysis software minitab.exe, obtains its strand center gross segregation exponential average, standard deviation.

$\stackrel{\‾}{{\mathrm{CSI}}_i}=\frac{{\mathrm{CSI}}_{i-1}+{\mathrm{CSI}}_{i-2}+\mathrm{...}+{\mathrm{CSI}}_{i-j}}{j}$

${\mathrm{\σ}}_{CSI}=\sqrt{\frac{1}{j}{\mathrm{\Σ}}_{x=1}^j({\mathrm{CSI}}_i-\stackrel{\‾}{{\mathrm{CSI}}_i})}$

Wherein,It is the center segregation exponential average analyzing sample, embodies Inner Quality of Billet and control average water Flat；σ_CSIPoor for analyzing the center segregation standard of index of sample, embody Inner Quality of Billet control stability.

Can be used as index after obtaining above-mentioned center segregation exponential average and standard deviation and weigh under different process in strand The height of portion's quality control level.

It is an advantage of the current invention that: comprehensive utilization strand low power is analyzed and drilling chemical analysis, it is possible to accurately find strand Actual solidification physical centre, it is to avoid the center segregation of casting blank analysis result deviation caused because of sample position factor, for slab quality Monitoring or the improvement of technique reference accurately is provided.

Accompanying drawing explanation

Fig. 1 is square billet solidification physical centre and geometric center schematic diagram.

Fig. 2 is square billet drilling sample position schematic diagram.

Fig. 3 is that carbon content comparison diagram detects with geometric center in physical centre.

Detailed description of the invention

Utilize the method for quantitatively evaluating of the square billet center gross segregation that patent of the present invention provides, be 160mm to cross dimensions The small billet SWRH82B Inner Quality of Billet of × 160mm is evaluated, and is contrasted with geometric center testing result, The concrete main basic parameter of casting machine and casting parameters are as shown in table 1:

Table 1 casting machine basic technological parameters and continuous casting process

Concrete steps and parameter are as follows:

1) the solidification physical centre of strand, the i.e. concrete position of final set in cross section is found out by hot acid etching method Put.First strand is processed into 15mm thickness coarse micro-grain sample, uses volume ratio 1:1 technical hydrochloric acid aqueous solution to carry out etch test, salt Aqueous acid temperature need to be heated to 70 DEG C, etch time 20min, then washes down with water and dries up.I.e. can get the low power group of strand Knit situation, find final set position in the solidification physical centre of strand cross section, i.e. strand cross section.

2) carrying out drilling sampling on strand cross section, the every point of 3.0g/, totally 5 sample points, sampling particular location is respectively 1st at strand cross section wherein one article of diagonal inner arc side 1/4, the 2nd in line of symmetry inner arc side, slab thickness direction 1/4 Place, the 3rd in casting blank solidification physical centre, the 4th at line of symmetry inner arc side, slab thickness direction 1/4, the 5th with first At the same diagonal outer arc side 1/4 of point.Infrared carbon sulfur analyzer is used to measure various location solute element concentration, every some detection 3 times, average, be respectively Inclined as macroscopic view The Appreciation gist of analysis, solute element during wherein i is steel, j is strand coarse micro-grain sample block number numbering, and this inspection amounts to 99 low powers Sample.For ensureing precision of analysis and reducing more bit change number of times, the Ф 5mm drill bit heart is used to carry out drilling sampling, sampling process In for avoid surface oxidation corrosion layer on analysis result affect, first drill through casting billet surface oxide etch layer 1.0mm remove, sample position Put and parent metal color need to occur, and further drilling analysis sample after cleaning out.

3) according to the segregation data of different samples, means of numerical analysis assessment centers segregation meansigma methods and standard are used Difference, reflection Inner Quality of Billet controls level and control stability.The calculating of coarse micro-grain sample center gross segregation index is concrete Formula is:

${\mathrm{CSI}}_i^j=\frac{{\mathrm{Content}}_{i-3}^j}{Average({\mathrm{Content}}_{i-1}^j,{\mathrm{Content}}_{i-2}^j,{\mathrm{Content}}_{i-4}^j,{\mathrm{Content}}_{i-5}^j)}$

Wherein,It is the 1st, 2,4,5 Point i element meansigma methods.

According to same heat or the center segregation index of the different coarse micro-grain samples of same flow time strand, data statistics is used to divide Analysis software minitab.exe, obtains its strand center gross segregation exponential average, standard deviation.

$\stackrel{\‾}{{\mathrm{CSI}}_i}=\frac{{\mathrm{CSI}}_{i-1}+{\mathrm{CSI}}_{i-2}+\mathrm{...}+{\mathrm{CSI}}_{i-j}}{j}$

${\mathrm{\σ}}_{CSI}=\sqrt{\frac{1}{j}{\mathrm{\Σ}}_{x=1}^j({\mathrm{CSI}}_i-\stackrel{\‾}{{\mathrm{CSI}}_i})}$

Wherein,It is the center segregation exponential average analyzing sample, embodies Inner Quality of Billet and control average water Flat；σ_CSIPoor for analyzing the center segregation standard of index of sample, embody Inner Quality of Billet control stability.

As it is shown on figure 3, be the comparison diagram of geometric center and physical centre's gross segregation analysis result.Visible, physical centre Place's carbon element content is higher than carbon element content at geometric center by about 0.10%, and this certainly will accurately determining the gross segregation of strand center Component analysis brings certain impact.Therefore, the method using this patent to relate to can be good at instructing actual production, to strand matter Lasting improvement and the reduction experimentation cost of amount are significant.

To the center segregation index obtained, above-mentioned computing formula is used to obtain, SWRH82B strand under given continuous casting process Center segregation exponential average be 1.016, standard deviation is 0.04612.

Claims (3)

1. the method for quantitatively evaluating of a square billet center gross segregation, it is characterised in that concrete steps and parameter are as follows:

1) the solidification physical centre of strand, the i.e. particular location of final set in cross section is found out by hot acid etching method；First First strand is processed into 10～20mm thickness coarse micro-grain samples, uses volume ratio 1:1 technical hydrochloric acid aqueous solution to carry out etch test, hydrochloric acid Aqueous temperature need to be heated to 60～80 DEG C, the etch time 15～30min, then washes down with water and dries up；I.e. can get strand Macrostructure situation, finds final set position in the solidification physical centre of strand cross section, i.e. strand cross section；

2) on strand cross section, drilling sampling is carried out, 3～5g/ every point, totally 5 sample points；Employing infrared carbon sulfur analyzer is surveyed Amount various location solute element concentration, every is detected 3 times, averages, and is respectively As the Appreciation gist of gross segregation, wherein i is molten in being steel Prime element, j is strand coarse micro-grain sample block number；

3) according to the segregation data of different samples, means of numerical analysis assessment centers segregation meansigma methods and standard deviation are used, instead Reflect Inner Quality of Billet control level and control stability；The concrete formula of calculating of coarse micro-grain sample center gross segregation index For:

${\mathrm{CSI}}_i^j=\frac{{\mathrm{Content}}_{i-3}^j}{Average({\mathrm{Content}}_{i-1}^j,{\mathrm{Content}}_{i-2}^j,{\mathrm{Content}}_{i-4}^j,{\mathrm{Content}}_{i-5}^j)}$

Wherein,Be the 1st, 2,4,5 i units Element meansigma methods；

According to same heat or the center segregation index of the different coarse micro-grain samples of same flow time strand, use data statistic analysis soft Part minitab.exe, obtains its strand center gross segregation exponential average, standard deviation:

$\stackrel{\‾}{{\mathrm{CSI}}_i}=\frac{{\mathrm{CSI}}_{i-1}+{\mathrm{CSI}}_{i-2}+...+{\mathrm{CSI}}_{i-j}}{j}$

${\mathrm{\σ}}_{CSI}=\sqrt{\frac{1}{j}{\mathrm{\Σ}}_{x=1}^j({\mathrm{CSI}}_i-\stackrel{\‾}{{\mathrm{CSI}}_i})}$

Wherein,It is the center segregation exponential average analyzing sample, embodies Inner Quality of Billet and control average level； σ_CSIPoor for analyzing the center segregation standard of index of sample, embody Inner Quality of Billet control stability；Obtain above-mentioned center segregation Can be used as index after exponential average and standard deviation and weigh the height of Inner Quality of Billet control level under different process.

Method for quantitatively evaluating the most according to claim 1, it is characterised in that step 2) described in 5 some particular locations Be respectively the 1st at strand cross section wherein one article of diagonal inner arc side 1/4, the 2nd in the line of symmetry of slab thickness direction At arc side 1/4, the 3rd in casting blank solidification physical centre, the 4th at line of symmetry inner arc side, slab thickness direction 1/4, the 5th point With first same diagonal outer arc side 1/4 at.

Method for quantitatively evaluating the most according to claim 1, it is characterised in that step 2) in for ensureing precision of analysis subtracting Little more bit change number of times, uses the Ф 5mm drill bit heart to carry out drilling sampling, for avoiding surface oxidation corrosion layer to dividing in sampling process Analysis result impact, first drills through casting billet surface oxide etch layer 1～2mm and removes, and sample position parent metal color need to occurs, and clear up Further drilling analysis sample after Gan Jing.