%%{init: {
  "theme": "base",
  "themeVariables": {"fontSize":"30px","fontFamily":"Calibri,Quicksand,sans-serif"},
  "flowchart": {
    "nodeSep":25,
    "rankSep":80
  }
}}%%
flowchart LR
    classDef default fill:#ffffff,stroke:#6699cc,stroke-width:2px,padding:24px;

    A["Hot-rolled
wire rod"] --> B["Heat
treatment"]
    B --> C["Wire
drawing"]
    C --> D["Heat
treatment"]
    D --> E["Pickling"]
    E --> F["Polishing"]
    F --> G["Cold
drawing"]
    G --> H["Hydrogen
annealing"]
    H --> I["Cold
drawing"]
    I --> J["Surface
treatment"]
    J --> K["Inspection"]
    K --> L["Packing
warehousing"]

    %%回流实线，和你参考图片一致
    E --> D
    I --> H

    linkStyle default stroke:#6699cc,stroke-width:1.5px;