D0I:10.13374/j.issn1001-053x.1989.06.026 第11卷第G期 北京科技大学学报 Vol.11 No.6 1989年11月 Journal of University of Science and Technology Beijing Nov,1989 Some Factors Affecting on the Structure- formation and Mechanical Properties of As-Cast High Toughness Nodular Cast Iron' Enoukidze Nodar A**,Lian Jinjiang(连金江)， Zhong Weizhen(钟作珍)，Rong Yu(戎獠)* ABSTRACT:Using sand moulds for step-shape casting tests and different silicon percentage of nodular cast iron it was possible to separate structural variations produced during freezing from those occurring at Ac:transformation temperature.The results show that an increasc in silicon content leading to di- fferent variation in the matrix structure,leads to a changing mechanical prope- rties of nodular cast irons.Tensile strength and elongation of obtained as-cast nodular cast iron with the composition of 3.9%C,3.2%Si,0.5%Mn are ma- ximum of about 524.5N/mm2 and 19.8%accordingly.In the same nodular cast iron,but only with 0.1%Mn the silicon addition first increases after decreases elongation,impact toughness and hardness.But tensile strength changes to the opposite side. KEY WORDS:cast iron,ferritic structure,thin-wall casting By varying the compesilion within the deformation limits,the wide variation in the microstructure and in mechanical propertics of nodular cast irons can be obtained.Further structural changes for a fixed iron composition can be readily brought about by heat treatment.But this technology becomes more expensive. Relating the compsition of these alloys to their mechanical properties is there- fore arbitrarily selected melt and solidification treatment,as well as for the cooling conditions during freezing(1.But there is the problem about selecting the chemical composition of as-cast nodular cast iron for production of thin-walled castings with ferritic structure and high elongation [2). Manuscript Received March 1,1989 ..Doctor,Ass.Prof.of Foundary Dept.of Gcorgian Polytechnic Institute, Tbilisi USSR ···Dcpt.of Metallurgy 544
第 卷第 期 年 刀 匕 写可 科 。 、 一 少 技 大 学 学 报 了 产 一 ’ 侧 月 一 夕 才 ’ 乍中伟珍 连 金 江 ， 夕 戎 像 一 “ · ， · ℃ 一 、、 一 ， ， 写 皿石 · 。 ， 、 、 ， ，· 二 ， ， 一 叭 · 尸 、 ， 手 ， 。 · 一 、 〕 · ‘ · 。 ， 川 · 一 一 一 ， 从 一 、 护 ， 二 ， ， … DOI ：10．13374／j ．issn1001－053x．1989．06．026
It was our task to select suitable composition of as-cast nodular cast iron for production thin-walled castings of ferritic struclure (more than 80%ferrite) with high mechanica!properties,especially high elongation. 1 Experimental Methods The alloy compositions were selected to examine the effects of silicon on the structure formation and mechanical properties of as-cast nodular cast iron with ordinary manganese content (0.5%).Master alloys were melted in acid lined induction furnace of the capacity 20kg.Silicon and magnesium alloy were added in a ladle,stirred,and the alloy poured in sand moulds for making of wedge-shape and step-shape castings with different thicknesses of 7,12,30,45, 60mm.All alloys were bypereutectic.The alloy compositions are given in Table 1. Table 1 Chemical Compositien of As-cast nocular cast iron Chemical composition, No. C Si Mn s P Mg C.E 1 3.9 2.8 0.5 0.010 0.058 0.062 4.83 2 3.9 3.2 0.5 0.010 0.058 0.055 4.97 3 3.9 3.4 0.5 0.011 0.045 0.051 5.03 3.9 2.8 0.1 0.011 0.045 0.054 4.83 5 3.9 3.0 0.1 0.012 0.045 0.056 4.90 6 3.9 3.2 0.1 0.010 0.045 0.053 4.97 2 Experimental Results and Discussion 2.1 Structure Photographs of the microstructures of step-shape castings sections of 12mm and 7 mm with different composition of silicon and manganese are shown in Fig.1.The graphite structure of the nodular cast iron in all cases was entirely spherulitic. Castings section of 12mm with the ordinary composition of manganese (0.5%) and silicon of about 2.8%solidifies as ferrite-pearlitic structure (60%ferrite, Fig.1,a).In spite of high cooling rate,due to low percentage of manganese (0.1%)the graphitization rate of similar to cast iron for castings section of 7mm is almost the same (65%ferrite).In both case,with the increasing of silicon content the process of ferritic structure formation is highly developed. 545
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Castings sections of 12mm and 7 mm with the composition of 3.2%Si,0.5%Mn and 3.0%Si,0.1%Mn accordingly represent the ferritic structure of about 80% or more (Fig.1,b).The results obtained in further investigation show that mechanical properties (especially elongation)of these compositions of as-cast nodular cast irons are maximums. The amount of ferritic structure according to the wall-thicknesses in different sections of castings is tabulated in Table 2.The effect of cooling rate on the formation of ferritic structure is illustrated in Fig.2. In nodular cast iron with 0.5%Mn (Fig.2),by the increase of silicon content and thicknesses of castings the amount of ferritic structure is increased also. But for the cast iron with 3.4%Si a slight decreasing ferritic structure within 30-60 mm of casting thicknesses is observed.When silicon contents are 2.8% and 3.2%and thicknesses of castings section is more than 30mm such a reduction of the amount of ferritic structure is observed also for nodular cast iron with low manganese content (Fig.3).This phenomenon is probably connected with reverse segregation of chemical elements present in nodular cast iron. Fig.1 MIcrostructure of step-shape castings section of 12mm a,2.8%Si;b.3.2%Si,c,3.4%Si(Mn=0.5%) 100 90 70 0,5%Mn 50 40 121824303642485460 Thickness of casting,mm Fig.2 Effect of cooling rate on formation of ferritic structure(0.5%Mn) (1)2.8%Si,(2)3.2%Si,(3)3.4%Si 546
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100 90 80 70 60 50 0.1%Mn 40h 6 12182430364245460 Thickness of casting,mm Fig.3 Effect of cooling rate on formation of ferritic structure (0.1%Mn) (1)2.8%Si, (2)3,0%Si, (3)3.2%Si Table 2 Microstructural results Nodular cast iron with Nodular cast iron with manganese content of 0.5% manganese content of 0.1% Speci- Silicon Thick- Fer- Speci- Silicon Thick- Fer- ness of rite. ness of rite men conlen casting men conten casting % mm % % mm % 2.8 7 45 16 2.8 7 65 2 2.8 12 60 17 2.8 12 85 3 2.8 30 85 18 2.8 30 78 4 2.8 45 90 19 2.8 45 82 5 2.8 60 95 2) 2.8 60 95 6 3.2 7 65 21 3.0 7 80 7 3.2 12 85 22 3.0 12 90 8 3.2 30 85 23 3.0 30 98 9 3.2 45 90 24 3.0 45 95 10 3.2 60 97 25 3.0 60 95 11 3.4 90 26 3.2 7 95 12 3.4 12 95 27 3.2 12 98 13 3.4 30 99 28 3.2 30 98 14 3.4 45 98 29 3.2 45 99 15 3.4 60 98 30 3.2 60 100 Comment:metallographic examinations carried out according to Chinese JB 1802-76 Fig.4 and Fig.5 show how the ferritic structure is changed in difference thicknesses of step-shape castings with the increasing of silicon content in nodular 547
爷‘ － 尸户户口 匕二二泊二二二目 三 曰沪尸 尸一 一， 刁卜 、 、 广，浏洲卜 产尸户 一产尸 母 孟 一二 ，， 上 。 呀 一卜乡冰‘ ， 一 一 。 ， 写 ， 写 。 自八工﹁山八勺︼﹄们工︸︸ 斤件，，竹匕八才生任八性︸内了︸浦 。 。 。 。 。 。 。 。 。 。 。 。 。 。 几月了、︺，八了 曰︸八任一‘ 口匕︺八口性刀合拭︵八口尸八︺一。︶比八，︺一口一 自山‘曰夕，，口上，只口︸ 巧 升只一乙任︸月生庄︼︶︸刀雌廿月止刀 … 斤只‘八乃八任尸才，，工月 八八口‘门 几 斗口乙八阳乃 曰土︸月 、 、 人 、 一 。 · 。 一 元 与
cast irons.Changing silicon content in the range of from 2.8%up to 3,4%,the effectiv enes of precipitation ferrile phases in small thicknesses of castings scction (Fig.4,section 7mm and 12mm)is more higher than that in the larges ones (30,45, 60mm).Intensification of ferrilic structure formation for section 30,45,60 mm of cast iron with 0.5%Mn is almost the same within 2.8~3.2%Si (Fig.4). This phenomenon may be explained by thei weak action of low manganese content on the graphitization processes. 100 100 90 80 70 059%Mn 0.1%Mn 50 40 40L 2.83.03.23.43.6 2.83.03.23.43.6 Si,94 Si, Fig.4 Effect of silicon on formation Fig.5 Effect of silicon on formation of ferritic structure:(0.5%Mn) of ferritic structure;(0.1%Mn) (1)7mm,(2)12mm,(3)30mm, (1)7mm,(2)12mm,(3)30mm, (4)45mm,(5)60mm (4)45mm,(5)60mm, 2.2 Mechanical Properties In each case of producing step-shape casting tests of different compositions for determination of structural changes,test bars of 25 mm wall-thicknesses were made simultancously.These wedge-shape were intended for a further machining standard specimens for definition of mechanical properties. The effect of silicon content on mechanical properties of nodular cast irons with 0.5%Mn and 0.1%6 Mn is illustrated in Fig.6 and Fig.7 respectively. The results obtained show that an increase in silicon content which giving rise to different variation in the matrix structure leads to a change of mechanical propertics of nodular cast irons.Increasing ratio ferrite to pearlite in nodular cast irons with 0.5%Mn by addition of silicon from 2.8%up to 3.4%leads first to an increasc,followed by a decrease in elongation,tensile strength and impact toughness,while the hardness changes in the opposite direction (Fig.6). Tensile strength and elongation of this series nodular cast iron with 3.2%Si are maximum of about 524.6N/mm and 19.8%respectively.In the second series nodular cast irons with 0.1%Mn,the silicon addition first increases after the decreases in elongation,impact strength and hardness,while tensile strength changes 548
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to the opposite side.Elongation and tensile strength of nodular cast iron containing 3.0%Si are about 23.6%and 485 N/mm2 accordingly (Fig.7). 24r 530 120 1250 24r 510 140 230 525 115 240 20 505 130 220 520 114 22C 500 120 12 515 105 220 12 495 110 103 21u 40 100 190 95 485 % 180 4190 3.4 480 110 .6 2.83.03.23.￥3,6 Si,% si,9% Fig.8 The effest of silicon senient cn Fig.7 The effe:t of siliccn content on mechanicai p-cperties of nodular mechanical properties cf nodular cast irons wizh 0.5%Mn cast irens with 0.1%Mn The fact that mechanical properlies of nodular cast irons are strongly influ- enced by ths chemica!compositi>n,and consequently,the matrix structure has been well esta!ished.The resuits show that txo compositions of ferritic stru- cture as-cas!nda'ar cast irons with very high mechanical properties were produced.Both of the alloys are convenient for producing thin-walled castings with ferritic structure (about 80%and more ferrite).For obtaining castings with wall-thicknesses of 12 mm or more it is better to use nodular cast iron containing 3.9C,3.2Si,0.5%Mn,(Fig.6)as well as castings of wall thickne- sses of 7-12mm produced from cast iron of 3.9%C,3.0%Si,0.1%Mn (Fig-7). The ratio of ferrite to pearlite in the iron matrixs of these alloys are shown in Fig.8.In both case the amount of ferrite is about 80-85%. 100 7mR0.1in)/ 90 5 Fig.8 The effect of siliccn content on formation of ferritic stru- 12mm (0.5%Mn) 4 60 cture in castings with 7mm and 12 mm wall-thicknesses 50 0/ 2.62.93.03.23.43.6 Si,% 549
五 · ， 气 · · 仃曰乙 氏行‘ 几比 去立 任」介 内 抽三 ，二八乙九︸ 今目心山，一几门 、之 纷科徽翔月竹补斜万 ，，、嘴几，‘，‘ 毛 时任。、均 空 留口 示 ‘ 心 口州工 岁 奢 即吮趁竺已。‘ 肠 丫 尸 呱 八 。 ﹄匀尸公︸︸ 去今︸，‘，勺只心八日或廿 怕之匕三任上 岁色冲 口 ，者土山 八吕八︺曰内 甘欣叮 、 升妊日断 于 日 二 尹尸二 ” 与 又 厂 ‘ 入 阮 ， 丫 一 以 、「 、 下曰卜 旦先 多 ， 言 “ 宁 ，勺盈胜‘里 口口︸乙门人‘户 口﹄，八﹄州 八曰了。︺ 口八 一 口尔 小一 ‘尸， ， 。 。 手 之 。 。 、 乙卜 。 金 、 七 。 城 卜 、 。 七 乞、 手 · 毛 王 ， ， ， 五 ， 。 ’〕 ’ 〕 一 几 上 一， 、 、 一 了 · 一 。 。 从 一 一 〕 飞百 ， 石 ， 。 乡百 ， 一 ， ， · · 五 一 ‘ 、 东 … ， 、 少 止 任护川 之 一 况卜 卜 士 一 卜 任产内户‘‘ 山八︸八 ﹃州‘ 伪‘
3 Conclusions For producing of thin-walled castings two compositions of ferritic structure of nodular cast iron are obtained.Castings with wall-thicknesses 7-12 mm may be produced from alloys containing 3.9%C,3.0%Si,0.1%Mn,as well as castings of wall-thicknesses 12 mm and more from nodular cast iron containing 3.9%C, 3.2%Si,0.5%Mn.The first As-cast nodular cast iron possesses elongation of about 23.6%and tensile strength of about 489 N/mm2,the second one-20%and 525 N/mm2 accordingly.Both of these compositions of as-cast nodular cast iron may be successfully used in practice. Acknowledgements:The authors wist to cxpress their thanks for the assistance of the staff of Foundry Department with the experimental work,and in 'particular to Mr.Liu Fulai,Wang Zigiong,Zhang Lijuan. REFERENCES 1 Sergeant G F,Evans E R.BCIKA Journal,1978;26(3):220 2 Tsunekawa Y,Shirozawa J.J.Japan Foundary Soc.,1982;54(7):423 The Anti-Scoring Lapping Paste for the Gears Rapidly Lapping-in Under Capacity Load Rapidly Lapping-in Under Capacity Load for gears is a difficult problem which is awaiting to solute in the world.This lapping paste with cubic network substance,could lap the gears under the capacity load without any damage.After lapping-in,the degree of tooth surface finish could be attained 78 and the con- tact area could be attained 100%.Otherwise,the degree of other tooth preci- sion index could be arised more than one grade,generally,the numbers for lap- ping-in will not be more than 10.So,It can take tne place of grinding bring about the effect of correction of the blank shape.Meanwhile,it could be lapping the worm-gearing,axe and bush,bolt and nat,and other parts that need rapidly lapping-in under capacity load. Lapping paste are no damage for bearing and equipment:no cnvironment po- llution,harmless for one's health. 550
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