• reduction of slag and improved product quality; • reduction of flue and sparks during the spheroid- izing operation. Several metalcasting facilities in China recently have


adopted this method. On-line controls can be used with this method to ensure stable quality. Other spheroidizing methods also exist that can be selected according to the conditions of individual foundries.


3) Proper Inoculation In general, inoculation has been observed to be roughly


controlled in Chinese foundries. Usually, the process is carried out only once after the spheroidizing operation, the inoculation agent size is ignored, and the method by which the agent is added is performed without the proper controls. To use a spheroidizing agent with fewer or no rare earth


metals, the inoculation process must be improved. Generally speaking, inoculation should be performed twice. Te specifi- cation of the inoculation agent and adding method should be optimized through testing. If possible, thermal analysis should not be used only for


the analysis of the silicon and carbon equivalent content. It also should be used to determine cooling curves for the melt sample in order to control metallurgical properties and realize uniform under-cooling and recalescence degree after spheroidizing and inoculation.


4) Selection of Spheroidizing Agents It is difficult to reduce the use of rare earth metals by sim-


ply varying the contents of the agent. Tests and experiments are necessary. For the production of small ductile iron castings, a


spheroidizing agent without rare earth metals can be used because of the parts’ high cooling rate and nodule count. Rare earth ferrosilicon magnesium alloys can be replaced with standard magnesium ferrosilicon alloys, but more of the agent should be used and inoculation should be performed twice to avoid fading. For the production of medium and large-size cast-


ings, it is better to use spheroidizing agents containing rare earth metals to increase nodule count and hinder the negative effects of detrimental elements. However, a lower rare earth metals content can be used when alloys are selected that adhere to the Chinese standard for


“rare earth ferrosilicon magnesium alloys GB/T 4138 －2004.” According to the standard, when 0.025% rare earth metal is added during spheroidizing, the residual of the material will be 0.008%, which will result in greater nodule counts and hinder the interference of detrimental elements. To reduce the use of rare earth metals, inocu- lation can be performed twice, and the amount of the spheroidizing agent can be increased. ■


To receive this digital magazine in the future, go to www.globalcastingmagazine.com.


◆ 球化剂的用量可节省很多； ◆ 可以减少渣量、提高产品质量； ◆ 减少球化处理的产生的烟雾和闪光。 目前，我国铸造行业中采用喂丝球化工艺的厂家很 少，今后应大力推广，条件适当的铸造厂，都可采用喂 丝球化工艺，还可以在此基础上实施在线控制，以确保 产品质量的稳定、一致。


当然，可供选用的球化工艺还很多，不必在此处赘述， 铸造厂也可以根据具体条件，采用最适合自己的工艺。


3．正确地做好育处理


据笔者的管见，在孕育处理方面我国不少铸造厂都过 于粗放，在球化处理后只进行一次孕育处理，而且在孕 育剂粒度的控制、加入方式等方面都不太严格，这是亟 待改进的。


在采用低稀土或不含稀土的球化剂、力求降低球化剂 用量的条件下，必须相应地强化孕育处理工艺。除个别 特殊情况外，一般都应该进行二次孕育，而且，孕育剂 的规格，加入方式等，都应该根据工厂的具体条件，通 过试验予以优化。


有条件的工厂，应该用热分析仪得到铁液的冷却曲 线，从而控制铸铁的冶金质量，力求球化、孕育处理后 的铁液的过冷度、再辉程度稳定一致。热分析仪，如果 只用以测定碳、硅含量和碳当量，就很不妥当了。


4．对球化剂的选用进行试验、研究


为保护资源，减少稀土金属的用量，绝不是简单地改 变料单所能奏效的，必须进行大量的试验研究工作。以 下，提出几点笼统的思路，供参考。


生产小型球墨铸铁件，由于铸件的冷却速率较高，组 织中石墨球数很多，球化剂中可以不含稀土。如果所用 的球化剂是稀土镁硅铁合金，可用镁硅铁合金替代，但 要考虑适当增加球化剂的用量，同时要认真做好二次孕 育，以减缓球化的衰退。


生产中、大型球墨铸铁件，为了使组织中石墨球数增 多，并抑制干扰元素的负面影响，还是以采用稀土镁硅 铁作球化剂为好，但要尽可能地减少稀土的用量，宜选 用GB/T 4138－2004《稀土镁硅铁合金》标准中稀土 含量低的牌号。


根据已经见到的资料，球化处理时往铁液中加入 0.025%的稀土，球墨铸铁中残留的稀土量为0.008%左 右，就可以有较多的石墨球数，并抑制干扰元素的影 响。减少球化剂中稀土的用量，难度并不很大，但有一 个重要的条件，就是必须认真做好二次孕育处理。同 时，也可能要适当增加球化剂用量，以减缓衰退。 ■


请点击www.globalcastingmagazine.com 获取电子版杂志.


44 | FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION Fall 2011


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85