Import Alloy Round Bars — Buy in wholesale FOB from Supplier in China

Alloy round bars from Big Co., Ltd. are high-performance steel bars manufactured from chrome-molybdenum, manganese, and nickel-chromium grades of alloy steel. The stated diameter range spans 10 mm to 500 mm, with lengths extending to 6000 mm, though the listing does not specify whether these represent stock sizes or maximum production capabilities. The bars are supplied to meet AISI, ASTM, DIN, GB, and JIS international standards, with common grades including 4140, 4340, and 8620 referenced for applications demanding elevated strength and wear resistance. The source material indicates these are hot-rolled products, which improves mechanical properties through controlled deformation and grain refinement during processing.

The 4140 grade (AISI 4140, EN 19A, SCM440) is a chromium-molybdenum steel with typical composition of 0.38-0.43% carbon, 0.80-1.10% chromium, and 0.15-0.25% molybdenum, offering balanced strength, toughness, and fatigue resistance. Grade 4340 (AISI 4340, EN 24, SNCM439) adds nickel at 1.65-2.00% alongside chromium and molybdenum, providing deeper hardenability and higher fracture toughness for heavy-section components. Grade 8620 (AISI 8620) is a nickel-chromium-molybdenum case-hardening steel with lower carbon (0.18-0.23%), designed for carburised surfaces with tough cores. Big Co., Ltd. does not specify which of these grades are held in stock versus available on mill order, so buyers should confirm grade availability and minimum order quantities directly.

Primary applications span automotive transmission shafts,connecting rods, and axle components; machinery spindles, gears, and couplings; construction equipment pivot pins and hydraulic cylinders; and energy sector drill collars and wellhead components. The 10-500 mm diameter range covers both small machined components and large forged press shafts. Buyers in automotive and aerospace sectors typically require vacuum-degassed or vacuum-arc-remelted material for critical applications, a specification not mentioned in the listing. Trade terms, actual MOQ, and lead time from Big Co., Ltd. must be confirmed directly, as the source description contains marketing language without committed figures. The supplier's profile shows harbour trust verification with zero response rate, so establishing reliable communication is a priority before procurement planning.

Big Co., Ltd. is registered in Tongzhou District, Beijing 101100, China, with its operational headquarters in the capital region. The supplier holds harbour-level trust verification on the platform, though the response rate is recorded at 0.00 percent with no average response time data. The company profile does not disclose establishment date, number of employees, annual turnover, manufacturing certifications, or quality management systems. No factory ownership or exclusive supply agreements are mentioned in the available data.

The listing positions Big Co., Ltd. as a supplier of alloy round bars to automotive, machinery, construction, and energy sectors, with reference to ISO and SGS certifications in the source material. However, buyers should independently verify the validity and scope of any claimed certifications, as the listing does not provide certificate numbers, accreditation bodies, or audit dates. The company's geographic location in Beijing suggests potential trading or headquarters functions rather than primary steel manufacturing, which is concentrated in provinces such as Jiangsu, Hebei, and Shandong. Buyers should clarify whether Big Co., Ltd. operates as manufacturer, trader, or agent, and request direct factory audit opportunities before committing to volume contracts.