重量法快速測定硅鐵中硅的誤差及校正方法

1、文章編號(hào):1000-7571(200205-0038-03重量法快速測定硅鐵中硅的誤差及校正方法關(guān)志中(廣州出入境檢驗(yàn)檢疫局,廣東廣州510623摘要:研究了快速法測定硅鐵中硅的誤差和校正問題,重點(diǎn)研究了硅鐵中可溶性雜質(zhì)元素、可揮發(fā)物和不溶物對(duì)結(jié)果準(zhǔn)確性的影響,推導(dǎo)出減少誤差的校正公式,指出了鋁和碳是造成誤差的主要元素,驗(yàn)證了校正公式對(duì)常見硅鐵的適用性。關(guān)鍵詞:快速法;硅鐵;誤差;校正方法中圖分類號(hào):O65511文獻(xiàn)標(biāo)識(shí)碼:B收稿日期:2001-10-26硅鐵是我國主要的鐵合金產(chǎn)品,通常含硅量較高。若采用堿熔高氯酸二次脫水法測定硅量,檢驗(yàn)結(jié)果較準(zhǔn)確,但操作繁瑣,檢驗(yàn)時(shí)間較長;若采用酸溶高溫灼燒

2、快速法測定硅量1,工作量少,檢驗(yàn)時(shí)間短,操作容易,但結(jié)果的準(zhǔn)確性難保證。本文研究了快速法測硅的誤差及校正辦法,采用快速法測定硅含量,同時(shí)測定某些雜質(zhì)含量,運(yùn)用校正公式計(jì)算結(jié)果,可獲得既快速又準(zhǔn)確的檢驗(yàn)效果。1實(shí)驗(yàn)部分111快速法要點(diǎn)試樣經(jīng)硝酸及氫氟酸處理后,硅轉(zhuǎn)化為SiF 4揮發(fā)掉,除去過量的酸,蒸干,高溫灼燒使殘?jiān)浞盅趸?從樣品和殘?jiān)姆Q量按下式計(jì)算出硅含量:Si =m -0170m 1m=1-Fe 2O 3%×0170(1式中:m ,m 1為試樣及其殘?jiān)|(zhì)量,0170為Fe 2O 3換算成Fe 的換算系數(shù)。112誤差的來源及校正如果硅鐵中只含有硅和鐵兩種元素,公式(1是完全正確

3、的,然而,硅鐵中不可避免地含有其它物質(zhì),這些物質(zhì)不同程度地影響測定結(jié)果的準(zhǔn)確性,使方法帶來誤差。綜合地,這些物質(zhì)可歸納為可溶性雜質(zhì)元素、可揮發(fā)物和不溶物。下面詳細(xì)介紹這些物質(zhì)引起的誤差和校正辦法。11211可溶性雜質(zhì)元素引起的誤差和校正:可溶性雜質(zhì)元素是指硅鐵中存在的少量元素,它能隨試樣的分解而溶解,高溫灼燒變成氧化物,如Al ,Ca ,Mn ,Cr ,P 等。假定硅鐵中含有一種可溶性雜質(zhì)元素M ,其氧化物MO (不考慮價(jià)態(tài),則高溫灼燒的殘?jiān)蠪e 2O 3和MO 兩種成分,若用式(1計(jì)算,測定值為:Si (測=m -0170×(Fe 2O 3+MO m=1-Fe 2O 3%017

4、0-MO %0170=1-Fe 2O 3%0170-M %K -10170式中:K MO 換算成M 的換算系數(shù)。正確的計(jì)算方法為:Si (正=1-Fe %-M %=1-Fe 2O 3%0170-M %兩者之間的誤差為:Si =Si (測-Si (正=M %K -1(K -0170如此類推,若有n 個(gè)可溶性雜質(zhì)元素存在于硅鐵中,方法誤差為:Si =ni =1M i %K -1i (K i -0170(2i =1,2,3,n式中:K i 第i 個(gè)雜質(zhì)元素由M i O 換算成M i 的換算系數(shù)?？扇苄噪s質(zhì)元素的誤差及校正與兩個(gè)因素有關(guān):(1K 值與0170差的大小,K 值與0170相差愈大,其影響愈

5、大,(2雜質(zhì)元素含量。表1列出了硅鐵中常見可溶性雜質(zhì)元素的K 值。11212可揮發(fā)物引起的誤差和校正:可揮發(fā)物(A 是指硅鐵中伴隨著SiF 4揮發(fā)而揮發(fā)掉或經(jīng)高溫?fù)]發(fā)的物質(zhì),如試樣的水分,S ,C 元素等,水分加熱蒸發(fā),S ,C 生成SO 2和CO 2揮發(fā)。這些物質(zhì)在按式(1計(jì)算時(shí)常被誤作Si 含量處理,使測定結(jié)果偏高,正確的計(jì)算方法是從測定結(jié)果中扣除83表1可溶性雜質(zhì)元素的K 值(換算系數(shù)T able 1K values of the soluble impurities (conversion coeff icients元素ElementAl Ca Mn Cr P Cu Ni K 值K v

6、alues0153017101630168014401800179可揮發(fā)物含量,即:Si (正=Si (測-ni =1A i %i =1,2,3,n兩者誤差為:Si =n i =1A i %(3i =1,2,3,n11213不溶物引起的誤差和校正:不溶物(N 是指酸分解試樣時(shí)不溶解、高溫灼燒不分解、不揮發(fā)的物質(zhì),如SiC 、硅渣、某些礦物等,這些物質(zhì)存在于低質(zhì)量的硅鐵中。測定時(shí)灼燒殘?jiān)黰 1為:m 1=Fe 2O 3+N 測定值為:Si (測=m -0170(Fe 2O 3+N m=1-Fe 2O 3%0170-N %0170正確的計(jì)算方法為:S (正=1-Fe 2O 3%0170-N %兩者

7、之差為:Si =N %0130(4硅鐵溶解完全時(shí),這部分可省略,若不溶物較明顯,需測定不溶物的總百分含量N %。11214方法誤差的整體校正公式:由式(1結(jié)合式(2,(3,(4得整體校正公式:Si =Si (測-SiSi =m -0170m 1m+ni =1M i %K -1i (K i -0170+ni =1A i %+N %0130(5113雜質(zhì)元素的影響程度我國國標(biāo)G B/T2272-19872規(guī)定了硅鐵雜質(zhì)元素的種類和含量,按式(2計(jì)算Al ,Ca ,Mn ,Cr 和P 引起的誤差;按式(3計(jì)算S 和C 引起的誤差,結(jié)果見表2。表2雜質(zhì)元素引起的誤差T able 2E rrors ca

8、used by the impurity elements%牌號(hào)Brands Si 含量Si content 雜質(zhì)元素的誤差Errors of the impurity elements Al Ca Mn Cr P S C FeSi90Al11587109510-01480103-0104-01005-010*FeSi90Al387109510-01970103-0104-01005-010*FeSi75Al015-A 74108010-01160102-0104-01007-010*FeSi75Al015-B 72108010-01160102-0105-0101-010*FeSi75Al1

9、10-A 74108010-01320102-0104-01007-010*FeSi75Al110-B 72108010-01320102-0105-0101-010*FeSi75Al115-A 74108010-01480102-0104-01007-010*FeSi75Al115-B 72108010-01480102-0105-0101-010*FeSi75Al210-A 74108010-01640102-0104-01007-010*FeSi75Al210-B74108010-01640102-0104-01007-01020102011從表2可知:Al ,Mn ,Cr 和P 引起負(fù)

10、誤差,使測定結(jié)果偏低;Ca ,S ,C 引起正誤差,使測定結(jié)果偏高。Al 和C 引起的誤差較大,其余元素引起的誤差較小,因此,式(5可化簡化為:Si =m -0170m 1m+Al %×0132-C %(62樣品測定選取8個(gè)不同硅含量的硅鐵樣品,測定每個(gè)樣品的鋁和碳含量,用快速法測定樣品中硅含量,按公式(1計(jì)算校正前測定值(B ,按公式(6求得校正后的值(C ,把校正前測定值(B 和校正后的值(C 與堿熔高氯酸二次脫水法測得硅量(A 作比較,計(jì)算結(jié)果誤差,見表3。93表3樣品測定結(jié)果T able3Determination results of samples%樣品Sample 測得

11、鋁量Al found測得碳量C found測得硅量Si found其他方法3(A本法校正前(B校正后(C偏差Deviation(B-(A(C-(A121350110761977615177116-01460119 211130108751607513375161-01270101 311180109751507510875137-0142-0113 401130104741707416574165-0105-0105 511270111741077317874108-01290101 611340112731307310673137-01240107 711410114721537210772

12、138-0146-0115 821310107701146915070117-016401033堿熔、高氯酸二次脫水法測定3結(jié)論試驗(yàn)結(jié)果表明,用快速法測定硅鐵中的硅,需同時(shí)測定樣品的鋁和碳含量,按校正公式計(jì)算出硅量,檢測結(jié)果的準(zhǔn)確性得到明顯的提高,方法適合于常見牌號(hào)的硅鐵測定。參考文獻(xiàn):1衡興國,黃按佑1實(shí)用快速化學(xué)分析新方法M1北京:國防工業(yè)出版社,1996115812G B/T2272-1987,硅鐵S1E rror and correction for the rapid determination of silicon in ferro2silicon by gravimetryGUA

13、N Zhi2zhong(Guangzhou Entry2Exit Inspection&Quarantine Bureau,Guangzhou510623,ChinaAbstract:In this paper,the error and correction for rapid determination of silicon in ferro2silicon by using gravimetry were investigated1The ef2 fect of the soluble impurities,volatiles and insoluble materials in

14、 ferro2silicon on the accuracy of the results was mainly discussed1The formula of correction was presented1It was shown that aluminium and carbon were the main elements causing error1The applicability of the formula for the common ferro2silicon was validated1K ey w ords:rapid analysis;ferro2silicon;error;correctio