China Baowu Steel Group has filed a patent for a low-carbon martensitic high hole expansion steel with a tensile strength above 980 MPa. The steel has a chemical composition that includes specific weight percentages of various elements and can be used for high-strength and thinning parts in passenger car chassis. GlobalData’s report on China Baowu Steel Group gives a 360-degree view of the company including its patenting strategy. Buy the report here.

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According to GlobalData’s company profile on China Baowu Steel Group, AI for workflow management was a key innovation area identified from patents. China Baowu Steel Group's grant share as of September 2023 was 69%. Grant share is based on the ratio of number of grants to total number of patents.

Low-carbon martensitic high hole expansion steel manufacturing method

Source: United States Patent and Trademark Office (USPTO). Credit: China Baowu Steel Group Corp Ltd

A recently filed patent (Publication Number: US20230313332A1) describes a low carbon martensitic high hole expansion steel with a tensile strength of 980 MPa or more. The steel is composed of various elements in specific weight percentages, including carbon (0.03-0.10%), silicon (0.5-2.0%), manganese (1.0-2.0%), phosphorus (=0.02%), sulfur (=0.003%), aluminum (0.02-0.08%), nitrogen (=0.004%), molybdenum (0.1-0.5%), titanium (0.01-0.05%), and oxygen (=0.0030%), with the remaining composition being iron and other unavoidable impurities.

The patent claims also provide alternative compositions for the steel, with slightly different weight percentages for some elements. These alternative compositions still maintain a tensile strength of 980 MPa or more. Additionally, the steel may contain additional elements such as chromium, boron, calcium, niobium, vanadium, copper, and nickel, in limited amounts.

The patent further describes the microstructure of the steel, which can be martensite or tempered martensite with residual austenite. The content of residual austenite in the microstructure is limited to =5% by volume.

The steel exhibits excellent mechanical properties, including a yield strength of =800 MPa, a transverse elongation A50 of =8%, and a hole expansion ratio of =30%. It may also have an impact toughness of =60 J at -40°C. The patent provides variations in these properties based on the specific composition of the steel.

The patent also outlines a method for manufacturing the low carbon martensitic high hole expansion steel. The process involves smelting and casting the components, followed by re-heating, hot rolling, and cooling. Additional steps such as annealing, pickling, rinsing, surface drying, and oiling may be included in the manufacturing process.

Overall, this patent describes a low carbon martensitic high hole expansion steel with excellent mechanical properties and provides a detailed method for its manufacturing. The steel's composition and microstructure contribute to its strength and performance in various applications.

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GlobalData Patent Analytics tracks bibliographic data, legal events data, point in time patent ownerships, and backward and forward citations from global patenting offices. Textual analysis and official patent classifications are used to group patents into key thematic areas and link them to specific companies