Shandong Engineering Research Center for Clean Foundry, Jinan , China

Transcription

1 Applied Mechanics and Materials Online: ISSN: , Vol. 597, pp doi: / Trans Tech Publications, Switzerland Research on Performance of Foundry Sand under the Effect of Chemical Binder Qingzhou Sun 1,2,a, Jingguang Yan 1,2,b, Puqing Zhang 1,2,c Zhongkui Zhao 1,2,d, Hang Du 1,2e 1 School of Materials Science and Engineering, Shandong Jianzhu University, Jinan , China 2 Shandong Engineering Research Center for Clean Foundry, Jinan , China a qingzhousun@126.com, b @qq.com, c zhangpuqing777@sina.com, d jorezhk@sdjzu.edu.cn, eduhang9008@163.com Keywords: Raw sand, Chemical binder, Molding sand, Property Abstract. This paper makes an experiental research on the performance of foundry sand under the effect of chemical binder. It discoveries the raw sand with different origin will have different properties even though they have the same particle size. The properties of their molding sand are also obviously different. For the raw sand that in the same particle size with similar acid demand value and four-screen distribution, the better grain shape will earn them a higher molding sand strength even though they have higher clay content. Under the effect of liquid binder, compared to the molding sand mixed from the sand of three-screen distribution, the molding sand mixed from those of four-screen distribution sand with other properties similar will have a higher tensile strength While under the effect of solid phenolic resin adhesive, the three-screen sand with good grain shape will have a high sand strength. Introduction Sand casting is not limited to the shape, size, complexity degree, alloy composition of the parts. And it is popular among foundryman for its low cost, short production cycles, and easy access to raw materials, so it has become the most popular casting way in production[1,2]. Along with the higher demand of the quality of casting products and of sand mould accordingly, chemical binder is used widely. As the chemical binder molding sand gets its tensile strength by chemical reactions and the binder is added with a small quantity, which makes proper choice of raw sand especially important[3,4,5,6]. Therefore, the experimental research on the performance of molding sand under the effect of chemical binder has been carried out to offer a theory basis for the rational choice of raw sand. Experimental Materials The raw sand comes from Weichang sand, Dalin sand and Zhangwu sand, of which the relevant performance indications are as shown in table 1. The solidim silicate with foundry grade is produced in Yanzhou, Shandong Province. Its modulus is 2.26, and Baume degree is 43º Be. Hardened ester is the slow ester produced in Shandong Yanzhou. The resin used in precoated sand is granular thermoplastic phenolic resin produced by Jinan Shengquan Group Co., Ltd(SQ) and with saturated aqueous solution with urotropine as curing agent, calcium stearate as lubricant. 808 Furan resin produced by SQ will be used as mixed resin for self-hardening sand, with toluenesulfonic acid as curing agent. GP201 phenolic resin and GP202 isocyanates produced by SQ will be applied as the resin for mixed cold box sand, with triethylamine as curing agent. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-09/05/16,14:49:18)

2 Applied Mechanics and Materials Vol Instruments and Equipment The main instruments and equipment for experiment include high efficiency rotor sand mixer, precoated sand mixer, cold box sand sampling device, DGG-9070B electro-thermostatic blast oven, SQY type of hydraulic strength tester, quick balance, platform scale, and stopwatch and so on. Type of raw sand Table 1 The main performance indications of raw sand Concentration Concentration Angular for three for four screen coefficient screen [%] [%] Particle size Clay content [%] Acid demand value [ml] Dalin sand 50/ Zhangwu sand 50/ Weichang sand 50/ Methods and procedures Prepare some Dalin sand, Zhangwu sand and Weichang sand respectively, GP201 phenolic resin and GP202 isocyanates with the proportion of 100:1:1. Firstly, mull the sand and GP201 phenolic resin in the high efficiency rotor sand mixer for 50s; secondly, add GP202 isocyanates into them to be mulled for 50s. Finally, bring them out as cold box resin sand. Intensify the cold box sand in 8 shape of sample mold for tensile strength slightly, harden these samples through amine blowing process in cold box sand sampling device with blowing pressure of 0.25MPa, blowing time of 8s, washing pressure of 0.2MPa, and washing time of 20s. After that, take the samples out and test their instant tensile strength and 24h tensile strength. The results are as shown in table 2. Table 2 The properties of cold box sand mixed by different raw sand Type of sand Instant tensile strength [ Mpa] 24h Tensile strength [Mpa] Dalin sand Zhangwu sand Weichang sand Prepare some Dalin sand, Zhangwu sand and Weichang sand respectively, sodium silicate and organic ester with the proportion of 100:4:0.48. Firstly mull the sand and organic ester in the high efficiency rotor sand mixer for 15s; secondly add the sodium silicate to be mulled together for 45s; finally, bring the sand out as sodium silicate bonded sand. Put the molding sand in sealed plastic bags, take out some every 1 minute and make them as 8 shape of samples, and test their tensile strength respectively after 24h. The experimental results are as shown in table 3 Table 3 The properties of sodium silicate sand mixed by different raw sand Sampling time [min] h Tensile Dalin sand strength Zhangwu sand [Mpa] Weichang sand Prepare some Dalin sand, Zhangwu sand and Weichang sand respectively, granular thermoplastic phenolic resin, saturated aqueous solution with urotropine, calcium stearate with the proportion of 100:3:0.36:0.3. Heat the sand to around 200 and then put them in coated sand mixer, which has been preheated to around 160. When the sand temperature drops to around 160, add the resin in the mixer and stir them fast; when it drops to around 110, add the saturated solution with urotropine in the mixer; when it drops to around 80, add the calcium stearate. Take them out when it drops to around 70 and the precoated sand comes out after being crushed and sieved when it is cooled to

3 264 Advance Materials Development and Applied Mechanics room tempreture. Put precoated sand into 8 shape of sampling mould for tensile strength, keeping the temperature of 255 for 210s, and get the 8 shape samples for tensile strength. Test the thermal tensile strength,1h tensile strength and 24h tensile strength for each sample respectively. Their experimental results are as shown in Table 4. Table 4 The properties of prcoated sand mixed by different raw sand Type of sand Thermal tensile 1h Tensile strength 24h Tensile strength strength [Mpa] [Mpa] [Mpa] Dalian sand Zhangwu sand Weichang sand Prepare some Dalian Sand, Zhangwu Sand and Weichang Sand respectively, 808 Furan resin and toluenesulfonic acid as curing agent with the proportion of 100:1.2:0.42. Mull the sand and curing agent in the high efficiency rotor mixer for 15s, and add resin to be mulled together for 45s, and then bring out them as self-hardening resin sand. Put the molding sand in sealed plastic bags, and take some sand out to make one set of 8 shape of samples for tensile strength every 1 minute waiting to be tested for their tensile strength after 24h respectively. Their experimental results are as shown in table 5. Table 5 The properties of self-hardening resin sand mixed by different raw sand Sampling time [min] h Tensile Dalin sand strength Zhangwu sand [Mpa] Weichang sand Analysis on the experimental results As shown in Table1 to table5, though Dalin sand,zhangwu sand and Weichang sand have similar acid demand value and same particle size of 50/100, their molding sand still have obviously different tensile strength due to the difference on other properties. The four kind of molding sand mixed from Zhangwu sand have the highest tensile strength. The tensile strength of its molding sand, including cold box sand, sodium silicate sand, precoated sand and self-hardening resin sand, is 24.0%,28.6%,29.5 % and 56.7% higher than the lowest one respectively. Compared to Dalin sand and Weichang sand with the same size and similar acid demand value, the Zhangwu Sand with the same size and acid demand value has the highest tensile strength due to its best grain shape with four-screen distribution even though it has a highest content of clay among the three. It shows that the grain shape rather than clay content is the key element in deciding the properties of molding sand in the condition of better size distribution. Cold box sand, ester hardening sodium silicate sand and Furan resin self-hardening sand mixed by Dalin sand have a higher tensile strength than other molding sand from Weichang sand, while the precoated sand mixed from Weichang sand has a higher tensile strength than the molding sand from Dalin sand. It can be found by a comparison that, the grain shape of Dalin sand with the similar clay content and same particle size is not as good as Weichang sand. Dalin Sand is four-screen distribution, while Weichang sand is three screens distribution. It shows that, when the other properties are similar, the grain size distribution of the sand under the effect of liquid binder is the key element deciding the properties of molding sand. The molding sand mixed by Dalin sand with four-screen distribution has a higher tensile strength than those from Weichang sand. However, when the other properties are similar, the grain shape rather than grain size distribution of the sand under the effect of phenolic resin adhesive is the key element deciding the properties of molding sand. Precoated sand mixed by Weichang sand with the better grain shape has a higher tensile strength

4 Applied Mechanics and Materials Vol Conclusion 1) The raw sand with different origin will have different properties even though they have the same particle size and similar acid demand value, and their molding sand have a big difference on tensile strength accordingly. 2) A better grain shape can also earn a high tensile strength for its molding sand of the raw sand with the same particle size of four-screen distribution and similar acid demand value, even with a high clay content. 3) Under the effect liquid binder, compared to the molding sand mixed by the raw sand of three-screen distribution with other properties similar, the molding sand from those of four-screen distribution will have a higher tensile strength. 4) Under the effect of solid phenolic resin adhesive, the molding sand of the raw sand with good grain shape will have a higher tensile strength if their other properties are similar. Acknowledgement This work is financially supported by Programs for Science and Technology Development of Shandong Province under Grant No.2010GSF References [1] Y.C. Li: Foundry Molding Materials Handbook ( Machinery Industry Press, China 2009 ) p.ii ( in Chinese ) [2] Q.D. Shi, L.H. Wang, G.L. Gao and H. Yao: Molding Materials ( Peking University Press, China 2009) p.182 (in Chinese) [3] Y.C. Li: Prcoated sand and core making technology ( Machinery Industry Press, China 2008 ) p.31 ( in Chinese ) [4] C.Z. Meng, Q.Z. Sun and P.Q. Zhang: Foundry Technology, Vol. 27(2006) No. 10, p ( in Chinese ) [5] M.S. Xie and N.L. Jiang: Practical technology of furan resin self hardening sand ( Machinery Industry Press, China 1994 ) p.12 ( in Chinese ) [6] Z.T. Fan, X.P. Dong and X. Lu: The Water Glass Sand Principle and Application ( Machinery Industry Press, China 2003 ) p.148 ( in Chinese )

5 Advance Materials Development and Applied Mechanics / Research on Performance of Foundry Sand under the Effect of Chemical Binder /