NXF UNS S30400 ASTM 304/JIS 304/EN 1.430 DN6-1200 Class3000-9000 Stainless Steel 304 Forged Fitting 90 Deg Socket Welding Elbow

1.Raw Material Inspection

he QC team checks chemical composition and mechanical properties to comply with ASTM standards. Visual inspection is carried out to detect surface defects including cracks, laminations, pits and inclusions. Heat numbers are recorded to achieve full traceability across the whole production cycle. Any non-conforming raw materials will be rejected and returned before blanking starts.

2.Cutting & Closed Die ForgingSteel bars are precisely cut into individual blanks by band saw according to blank dimensions calculated from finished product drawings. Each blank is weighed to guarantee consistent material volume for forming. The cut blanks are sent to the heating furnace and heated within a strict, grade-specific temperature window. Precise temperature control is critical throughout heating. If the blank temperature is too low, metal plasticity drops sharply, restricting metal flow inside the die cavity and causing incomplete filling, folded metal or cold cracks on the elbow body. If overheated, grain boundaries will be burnt, resulting in coarse grains and permanently reduced mechanical strength and impact toughness. Once reaching the target forging temperature, blanks are rapidly transferred into precision closed forging dies. A hydraulic press applies high pressure to shape the elbow body. The excess flash generated during forging is trimmed off afterwards. This closed-die forging process refines internal grain structure and eliminates internal voids to ensure reliable pressure-bearing capacity.

3.Heat Treatment

The forged elbow blanks undergo heat treatment processes including normalizing, tempering or solution annealing based on different material grades. This procedure relieves residual stress produced in forging, optimizes hardness and balances mechanical toughness. After heat treatment, hardness testing is performed to verify the results meet technical specifications. Blanks failing hardness inspection will be reprocessed before moving to machining procedures.

4.Rough Machining

CNC lathes and machining centers carry out rough machining on the elbow body and socket ends. Most redundant material is removed while reasonable machining allowance is reserved for subsequent precision machining. Large burrs and sharp edges are cleared after rough turning. Operators inspect blank dimensions to prevent excessive tolerance deviation that may affect the accuracy of final socket machining.

5.Precision Machining

Precision machining is performed on socket bore, shoulder, end face and outer contour. Socket depth, wall thickness and all dimensional tolerances are strictly controlled in accordance with ASME B16.11. Inner chamfers are machined to facilitate pipe insertion during site installation. Operators use calipers and special gauges to verify key dimensions. Metal chips and cutting fluid are thoroughly cleaned after machining. NDT tests such as MT or PT can be conducted upon customer order requirements to detect hidden surface flaws.

6.Final Inspection, Marking & Packing

QC carries out comprehensive final inspection covering all dimensions, machining quality and surface condition. Permanent marking including material grade, nominal size, pressure class and heat number is stamped on the fitting body. Qualified socket welding elbows are coated with anti-rust oil, wrapped in waterproof plastic bags and packed in fumigated wooden cases. Material certificates and inspection reports are prepared together for shipment.