%%{init: {
  "theme": "base",
  "themeVariables": {"fontSize":"32px","fontFamily":"Calibri,Quicksand,sans-serif"},
  "flowchart": {
    "nodeSep":25,
    "rankSep":80
  }
}}%%
flowchart LR
    classDef default fill:#ffffff,stroke:#6699cc,stroke-width:2px,padding:24px;

    A["Pipe billets"] --> B["Polishing"]
    B --> C["Cold rolling"]
    C --> D["Degreasing
cleaning"]
    D --> E["Bright
heat treatment"]
    E --> F["Straightening"]
    F --> G["Polishing"]
    G --> H["Physical test 
chemical test"]
    H --> I["UT"]
    I --> J["VT"]
    J --> K["Packing
warehousing"]

    %% 上方回流支路
    D --> L["Cold rolling
(drawing)"]
    L --> M["Polishing"]
    M --> N["Straightening"]
    N --> E

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