NXF UNS S30400 ASTM 304/JIS 304/EN 1.4301 DN6-1200 Class3000-9000 Stainless Steael 304 Forged Fitting Threaded Hexagonal Nipple

1. Product Overview

A stainless steel 304 threaded hexagonal nipple is a pipe fitting with male threads on both ends and a hexagonal middle section. It is used to connect two threaded components — pipes, valves, instruments, or equipment — and the hex flats make it easy to tighten with a standard wrench. Common sizes range from 1/8" to 4" (DN6 to DN100), and the fitting is typically specified for water, steam, oil, and food or beverage service where 304's corrosion resistance is sufficient.

2. Material Properties — Stainless Steel 304

Grade 304 (AISI 304 / EN 1.4301 / 06Cr19Ni10) is the most widely used austenitic stainless steel, often called "18/8" for its nominal composition of 18% chromium and 8% nickel. It delivers a strong balance of corrosion resistance, formability, and weldability, and is essentially non magnetic in the annealed condition. 304 resists corrosion well in atmospheric, fresh-water, and mildly chemical environments, but it is vulnerable to chloride-induced pitting — so it is not recommended for marine, coastal, or high-salt service, where 316 should be used instead. Mechanically, 304 offers tensile strength of at least 515 MPa and yield strength of at least 205 MPa, with hardness held to HB ≤ 187.

3. Raw Material Preparation

Production starts with selecting 304 stainless steel round bar in diameters typically between Φ10 mm and Φ110 mm, sized to the fitting. Each batch is checked against its Mill Test Certificate to confirm chemical composition and mechanical properties. The bar is then saw-cut to blank length with a 2 to 3 mm machining allowance on each side. Finally, blanks are surface-cleaned by pickling or shot-blasting to remove oxide scale, oil, and other contaminants.

4. Manufacturing Process

The blank is first heated to 1100–1200 °C in a medium-frequency furnace and upset-formed into the hexagonal middle section, which improves grain flow and mechanical strength. The part is then solution-treated at approximately 1050 °C and quenched to relieve forging stress and restore corrosion resistance. After that, a CNC lathe machines the outer diameter, end faces, and chamfers to drawing tolerance, and a milling machine or CNC center cuts the hex flats to the specified across-flats dimension. Threads are then cut or rolled on both ends — the most critical operation, where thread profile, pitch, and taper must be held precisely. Finally, the part is deburred by hand or vibratory finishing to remove thread burrs and protect sealing surfaces.

5. Surface Treatment & Quality Inspection

After machining, the fitting is pickled in a nitric-hydrofluoric acid bath to remove surface contamination and form a dense chromium-oxide passive film that restores full corrosion resistance. Threads are then coated with food-grade silicone oil or a rust-preventive film for storage. Every fitting undergoes100% inspection: chemical composition is verified by portable spectrometer (PMI), mechanical properties are batch-tested for tensile ≥ 515 MPa and yield ≥ 205 MPa, hardness is held to HB ≤ 187, threads are checked with Go / No-Go ring gauges, and every piece passes a hydrostatic test at 1.5× working pressure held for 30 seconds with no leakage allowed.

6. Packaging & Applications

Each piece is sealed in a PE bag or bubble wrap, with plastic thread protectors fitted on both ends. Pieces are packed into cartons and consolidated onto pallets, accompanied by the Mill Test Certificate, Certificate of Conformity, and packing list. Export packaging follows ISPM 15 fumigation rules. Stainless steel 304 threaded hexagonal nipples are widely used in food and beverage processing lines, dairy equipment, brewery and winery piping, water treatment and HVAC systems, chemical containers, architectural and sanitary plumbing, and general industrial machinery — anywhere a reliable threaded pipe connection is needed and chloride exposure is limited.