The plot clues of how steel was forged mainly included the following aspects: 1. The protagonist's growth experience: The protagonist, Pavel Kochagin, began to grow from a worker to an excellent steel worker and leader through his own efforts and opportunities during the Soviet Union's industrial period. 2. Description of the social environment: The novel described the social background of the Soviet Union during the industrial period, including political system, economic system, cultural style, etc., showing the social reality and historical characteristics of that era. 3. Individual struggle and teamwork: Pavel Kochagin constantly encounters difficulties and challenges in the novel, but he always insists on self-struggle and continuous learning. At the same time, he actively collaborates with the people around him to achieve his goals. 4. Thematic discussion: The novel discussed some issues in the process of industrialization, including labor efficiency, talent cultivation, production relations, etc. It also discussed philosophical issues such as individuals and collectives, tradition and modern times, struggle and success. 5. War background and plot setting: There are war scenes in the novel, including World War II and the Battle of Stalingrid. These plot settings help to promote the development of the story and reveal the theme.