论文总字数：20251字

摘 要

乙烯裂解炉是乙烯生产装置的最重要的组成部分，也是石化工业的重要设备。乙烯裂解炉炉管在渗碳、高温、结焦和热疲劳的作用下容易损坏，渗碳损伤是导致炉管失效的重要因素之一。乙烯裂解炉炉管早期损坏失效，严重影响企业的安全生产。乙烯裂解炉炉管的失效和损坏将导致裂解炉的非计划停炉，延误企业的正常生产。同时，裂解炉炉管成本昂贵，更换炉管会增加生产企业的投资成本，极大地影响生产企业的经济效益，后果更为严重，对人们的生命安全构成威胁。因此，国内外对乙烯裂解炉管渗碳损伤的研究一直受到重视。

辐射段炉管是裂解炉使用温度最高、使用环境最恶劣的区域，是裂解炉的核心部件。因此，人们常说裂解炉炉管是指裂解炉炉管的辐射段。HP40和HK40合金是我国应用最广泛的裂解炉管材料。研究HP40炉管的各种损伤对保证裂解炉的安全运行具有重要意义。虽然国内外学者对裂解炉炉管进行了大量的研究，但对裂解炉炉管的整体损伤和碳化物转变的研究还不够，需要进一步的分析。

经过多年的使用，HP40炉管的各个部位都发生了渗碳。炉管直翼凸点渗碳层厚，温度分布不均匀，导致炉管渗碳程度不同。服役后，碳化物在晶界和晶体中析出，M₂₃C₆碳化物在非渗碳区析出，M₂₃C₆碳化物先在渗碳区析出，随碳含量的增加逐渐转变为M₇C₃碳化物，随着碳含量的增加，晶界碳化物逐渐转变为粗大的链状，并在晶体中逐渐形成块状碳化物。

本研究主要针对使用多年的HP40乙烯裂解炉炉管进行研究。研究内容包括不同管段渗碳检测分析、炉管结构变化规律及高温服役后力学性能的变化。本研究基于碳化物特征，对不同寿命阶段的材料中的碳化物性能进行表征，从而尝试开发出一种能够较快速研究寿命的新方法。首先对试验材料—乙烯裂解炉管HP40Nb介绍；然后介绍了乙烯裂解炉管碳化物的渗碳过程；最后阐述了可行的解决方法。

关键词： 乙烯裂解炉 碳化物特征 渗碳

A study on as cast structure degradation based on characterization of carbide properties

Abstract

Ethylene cracking furnace is not only the core unit of ethylene production unit, but also the important equipment of petrochemical industry. The working condition of ethylene cracking furnace is very poor. The furnace tube of ethylene cracking furnace is easy to be damaged under the joint action of carburizing, high temperature, coking and thermal fatigue. Carburizing damage is one of the important factors leading to the failure of furnace tube. The early damage and failure of ethylene cracking furnace tube seriously affect the safety of production. The failure and damage of ethylene cracking furnace tube will lead to unplanned shutdown of cracking furnace and delay the normal production of the enterprise. At the same time, the cost of cracking furnace tube is expensive. Replacing furnace tube will increase the investment cost of production enterprises, greatly affect the economic benefits of production enterprises, with more serious consequences, and pose a threat to people's life safety. Therefore, the research on Carburizing damage of ethylene cracking furnace tube has been paid more attention at home and abroad.

Radiation section furnace tube is the area with the highest service temperature and the most severe service environment in cracking furnace, and it is the core component of cracking furnace. Therefore, it is often said that the cracking furnace tube refers to the radiation section of the cracking furnace tube. HP40 and HK40 alloys are the most widely used cracking furnace tube materials in China. It is very important to study all kinds of damages of HP40 furnace tube to ensure the safe operation of cracking furnace. Although researchers have done a lot of research on the cracking furnace tube, the research on the overall damage and carbide transformation of cracking furnace tube is not enough, and more analysis is needed.

After years of use, carburization has taken place in all parts of HP40 furnace tubes. The thickness of carburizing layer and uneven temperature distribution in the straight wing convex point of furnace tube lead to different carburizing degree of furnace tube. After service, the carbide precipitates in the grain boundary and crystal, M₂₃C₆ carbide precipitates in the non cemented area, M₂₃C₆ carbide precipitates in the cemented area first, and gradually transforms into M₇C₃ carbide with the increase of carbon content. With the increase of carbon content, the carbide in the grain boundary gradually transforms into coarse chain shape, and gradually forms massive carbide in the crystal.

This research mainly focuses on HP40 ethylene cracking furnace tube which has been used for many years. The research contents include the carburizing detection and analysis of different pipe sections, the change rule of furnace tube structure and the change of mechanical properties after high temperature service.Based on the characteristics of carbides, the properties of carbides in materials with different life stages are characterized in this study, so as to try to develop a new method to study life more quickly. Firstly, the experimental material, HP40Nb, is introduced; then the carburizing process of carbide in ethylene cracking furnace tube is introduced; finally, the feasible solutions are described.

Key Words:Ethylene cracking furnace; Carbide characteristics;Carburization

目录

摘要 I

Abstract II

目录 IV

第一章 绪论 1

1.1 引言 1

1.2乙烯裂解炉管 2

1.2.1乙烯裂解炉管概述 2

1.2.2 乙烯裂解炉材料的发展 3

1.2.3 乙烯裂解炉管的工作条件 4

1.3本文主要研究内容 7

第二章 试验材料与研究方法 8

2.1 试验材料 8

2.2 试验方法 10

2.2.1.利用光学显微镜检测 10

2.2.2 利用扫描电镜检测 11

2.3力学性能试验 11

2.3.1 显微硬度试验 11

2.3.2 拉伸试验 12

2.4 本章小结 13

第三章 镍基合金碳化物特征劣化研究 14

3.1 引言 14

3.2 试验结果与讨论 16

3.2.1 实际服役材料微观形貌 16

3.2.2 碳化物形貌 17

3.3服役材料力学性能 23

3.3.1硬度试验 23

3.3.2拉伸试验 23

3.4 本章小结 24

第四章 总结与展望 26

第五章 经济性分析 27

5.1 单个试验成本预估 27

5.2 经济性分析小结 27

致谢 27

参考文献 28

第一章 绪论

引言

石化行业是推动世界经济发展的支柱产业，乙烯产品作为石化行业的主导产品具有很高的地位^[1]。乙烯是生产各种有机原料的基础，是石油化工最重要的基础原料之一。目前，世界上约75%的石化产品^[2]是乙烯。乙烯工业的发展总体上反映了一个国家石化工业的实力水平。乙烯产品直接关系到各个行业的发展，包括纺织、化工、橡塑制品、机械制造等行业。乙烯与人们的生活和国民经济息息相关。2003年，我国乙烯产量分别占亚洲和世界的17%和4.6%，居世界第四位。

20世纪90年代以来，世界乙烯生产设施不断加快。设备规格越来越大，技术水平和产业集中度也越来越高^[3]。乙烯装置规模来看，目前世界上以化工轻油为原料的裂解装置规模已达到110万吨/年^[4]，并在不断提高，如图1所示。

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