中国科学院过程工程研究所机构知识库

目前，国内外科研机构和钢铁企业非常重视钢坯高温防氧化技术，并获得了一定的成果，但在工业应用中还存在一些难题。其中，最为共性的难题是涂料的贮存稳定性差，常常几小时至一天即出现沉降分层，甚至产生硬沉淀，导致无法使用。故钢厂在使用时大都是临时调配。贮存稳定性差会导致一系列问题：涂料颗粒返粗，涂层不均匀，影响防氧化性能；短时间内出现沉淀，容易堵塞应用现场的管道和喷枪；产生硬沉淀导致涂料报废，造成损失；少量分批调配又严重影响到生产效率。因此阻碍了防氧化技术的大范围推广。针对上述问题，改善涂料贮存稳定性具有重要的意义。本文针对镁系钢坯高温防氧化涂料贮存稳定性差的技术难题，从悬浮剂的种类、用量和贮存条件等方面研究了其对涂料稳定性的影响，探讨了贮存时间对防氧化效果的影响和悬浮剂提高贮存稳定性的机理。具体工作如下：分析和探讨了防氧化涂料的稳定性影响因素和稳定机理，应用Stokes沉降模型公式计算沉降速率，得出了从减小粒径、降低颗粒密度、提高粘度等方面可以减缓沉降的措施。探讨了Excelcon 100、ST 3000、301、FP6和HPS等不同种类的改性醚化淀粉对防氧化涂料的贮存稳定性的影响。实验结果表明淀粉类增稠剂作为悬浮剂并不能有效地改善涂料的悬浮性能，一两天即分水变硬，使涂料发生硬化固化反应。研究了羟乙基纤维素、改性羟乙基纤维素和乙基羟乙基纤维素等纤维素醚对防氧化涂料贮存稳定性能的影响。通过研究悬浮剂对涂料稳定性能的影响得出，250 HBR或BR 30000H两种纤维素醚作为悬浮剂的效果较好，贮存14天时仍保持良好的保水性和流动性。探讨了250 HBR和BR 30000H两种纤维素醚用量、贮存温度和其他因素对贮存稳定性的影响，当其用量为0.26~0.33%时，密闭避光保存，储存温度25℃，将涂料保质期由不足1天至少延长14天。同时研究了使用悬浮剂后的防氧化涂料对钢坯的防氧化效果，氧化烧损率减少了70%，贮存14天后氧化烧损仍能够减少50%，并且之后随着贮存时间的延长，防护效果变化不大。利用扫描电镜（SEM）、Zeta电位仪和X射线衍射仪（XRD）等分析测试手段，分析探讨了悬浮剂的悬浮稳定机理。SEM测试结果表明涂料颗粒粘附或嵌入溶胶体系中，从而起到悬浮防沉作用；Zeta电位结果表明增加纤维素用量，可以提高Zeta电位的绝对值，使体系处于稳定状态；含悬浮剂的防氧化涂料XRD测试结果表明纤维素醚或淀粉醚这类悬浮剂不会引起粉体的化学反应，从而保证了防氧化涂料的原有功能。 ;At present, the high-temperature anti-oxidation technology for steel billet has been valued by scientific research institutions and Steel Corp at home and abroad, and some results have been achieved. However, there are still many problems in industrial application. Among them, the poor storage stability of such coatings is a ubiquitous problem. Generally, sedimentation and stratification occur from a few hours to a day, and even hard precipitation appears, resulting in failure to be used normally. Therefore, the temporary deployment is mostly used in Steel Corp. The poor storage stability will lead to a series of problems: The coating particles are coarse and the coating is uneven, which affects the oxidation resistance. Sedimentation occurs in a short time, so that pipes and spray guns are easily blocked. Hard precipitation causes the coatings to be scrapped, resulting in loss. Small batch allocation seriously affects the production efficiency. Therefore, a wide range of anti-oxidation technology has been obstructing. In view of the above problems, it is of great significance to improve the storage stability of coatings.In this thesis, in view of the poor storage stability technical problems of magnesium-based anti-oxidation coatings for steel billet at high temperature, the effects of the types, dosage of the suspension agent and storage condition on the storage stability of the coatings was discussed successively. The effect of storage time on the oxidation resistance and the mechanism of the high storage stability of the suspension agent were discussed. Specific work as follows:The influence factors of stability and stability mechanism of the anti-oxidation coatings was analyzed and discussed. The settlement rate was calculated by using the Stokes settlement model formula, and the measures to reduce the settlement were proposed, such as reducing particle size, reducing particle density and increasing viscosity.The effects of different kinds of modified etherification starch, such as Excelcon 100, ST 3000, 301, FP6 and HPS, on the storage stability of the anti-oxidation coatings were investigated. The experimental results show that the starch thickener as a suspending agent cannot effectively improve the suspending properties of the coatings. One or two days, the coatings moisture and harden, leading to hardening and curing reaction. The effects of hydroxyethyl cellulose, modified hydroxyethyl cellulose and ethyl hydroxyethyl cellulose on the storage stability of the anti-oxidation coatings were studied. Through the study of the influence of suspending agent on the stability of the coatings, two kinds of cellulose ethers, 250 HBR or BR 30000H, as suspending agent have a good effect. After 14 days of storage, they still maintain good water retention and flowability. The effects of the amount of 250 HBR and BR 30000H cellulose ethers, storage temperature and other factors on the storage stability were discussed. When the amount of cellulose is 0.26 ~ 0.33% and the storage temperature is 25 ℃, sealed and kept away from light, the shelf life of the coatings should be extended for at least 14 days from less than one day. At the same time, the anti-oxidation effect of the anti-oxidation coatings after using the suspending agent on the billet was studied. The oxidation burning rate is reduced by 70% and the oxidation burning loss is still reduced by 50% after the storage for 14 days. And then the protective effect has not changed much with storage time.The suspension stability mechanism of suspending agent was analyzed and discussed by means of scanning electron microscope (SEM), Zeta potentiometer and X-ray diffractometer (XRD). SEM test results show that the coating particles are adhered or embedded in the sol system, so as to play a role of suspension and anti sinking. The results of Zeta potential show that increasing the amount of cellulose ether can increase the absolute value of Zeta potential and make the system in stable state. The XRD test results of suspending agent-containing anti-oxidant coatings show that the suspending agent such as cellulose ether or starch ether will not cause the chemical reaction of the powder, thus ensuring the original function of the anti-oxidation coatings.