4.2.1.2 Inspection Method
Each specification of the pre-spheroidized beads produced every day is a batch, and the inspector samples and inspects. The appearance inspection is based on visual inspection. The weight inspection uses a standard container filled with 1000ml of material and weighed on an electronic scale with a division of 1% gram. Each specification is sampled no less than 3 times a day, and the average value is obtained after weighing.
4.2.1.3 Handling of unqualified products
After the unqualified products have been inspected, the inspector reports to the head of the quality inspection department or the process engineer of the wax mold workshop for review. In the case where the density does not exceed 10% of the standard, the unqualified products can be adjusted in specification or conditionally accepted. If it exceeds the range, it will be scrapped.
4.2.1.4 Inspection Record: The inspector fills in the inspection record truthfully and clearly states the inspection conclusion.

4.2.2 Mold Inspection
4.2.2.1 Inspection standards and judgment criteria
a) Appearance inspection, the overall mold is intact, the grain size is uniform, and there should not be too many large voids;
b) There should be no over-burning or under-burning phenomena;
c) After the mold is dried, it should weigh the weight shown on the mold weight table. The tolerance range is ±5%.
4.2.2.2 Inspection method: The inspector inspects it piece by piece. The appearance inspection is based on visual inspection, and the weight detection is weighed on a 1% gram electronic scale after the mold has been dried for 24 hours.
4.2.2.3 Handling of unqualified products
The inspector confirms the unqualified samples after inspection and discards them.
4.2.2.4 Inspection Record
The inspector fills in the inspection record truthfully and clearly states the inspection conclusion.

4.2.3 Mold Sample Inspection
4.2.3.1 Inspection standards and judgment criteria
a) The dimensions and positions of the molds should meet the requirements of GB/T13295-2008 “Ductile iron pipes, fittings and accessories for water and gas pipelines” or the requirements of the drawings;
b) The seams are firmly bonded, the adhesive tapes are flat and firm, and there are no seams or warping;
c) The surface of the mold should be flat and smooth, and the unevenness should not exceed 0.5mm.
d) The mold should have clear and complete cast marks, including at least: the name or factory mark of the production plant, the year of production, the cast iron material, the nominal diameter, wall thickness K value, flange PN value, standard number, and product batch number.
4.2.3.2 Inspection method
The inspector inspects it piece by piece. The appearance and identification inspection are based on visual inspection, the dimensional inspection is inspected with calipers, straight edges, bending rulers, and angle rulers.
4.2.3.3 Handling of unqualified products
After the inspector has confirmed that the molds do not meet the requirements, they should be returned to the production team for rework. If rework is not possible, the molds should be scrapped. The reworked molds should be inspected again.
4.2.3.4 Inspection Record
The inspector fills in the inspection record truthfully, and clearly states the inspection conclusion.

4.2.4 Coating Inspection
4.2.4.1 Inspection standards and judgment criteria
a) The surface coating is uniform and leak-free, and the coating thickness meets the process requirements;
b) The coating layer is thoroughly dried;
c) After the coating is dried, the dimensional accuracy of the mold should meet the requirements of the standard drawings.
4.2.4.2 Inspection Method
a) Coating thickness inspection:
A sample is taken from the model group where the paint is completely dry and can be modeled. A 10×10 equilateral triangle is drawn at a specific location with a blade, drawn to the surface of the model, and then the paint piece is pried off with a blade. The thickness of the coating at that location is measured with a caliper. The location where the sample is taken should be touched up with quick-drying paint. One large, medium, and small piece should be taken from each kiln and measured.
b) The methods for checking uniformity and dryness are based on visual inspection and tapping.
c) The dimensional accuracy is inspected with a platform, straight edge, and bending ruler.
4.2.4.3 handling of unqualified products
For the models that are not dry, continue to dry them. The rest of the unqualified products should be reworked and re-inspected after rework.
4.2.4.4 Inspection Record
The inspector fills in the inspection record truthfully, and records the reworked products separately.

4.2.5 Molten Iron Inspection
4.2.5.1 Iron inspection standards
a) Chemical composition
C 3.65-3.88% Si 1.4-1.8% JD-D001 “Chemical Composition Test of Iron” is used for chemical analysis, and the iron temperature is detected by the smelting worker with a digital thermometer.
4.2.5.3 Control points
Carbon, silicon, and carbon equivalent detection are carried out by smelting workers during the smelting process. A rapid thermal analyzer is used for rapid thermal analysis before the furnace. Based on the results of the thermal analyzer, the iron composition is adjusted to meet the iron standard requirements. The foundry responsible engineer is responsible for supervising and reviewing.
4.2.5.4 Quality records
The smelting work record is reviewed by the director of the foundry workshop, and the chemical composition analysis is carried out by the physical and chemical inspector. The head of the physical and chemical room reviews it.

4.2.6 Nodularization Inspection
4.2.6.1 Inspection standards and judgment criteria
Triangular test piece: The edges of the shape are rounded, the sides are noticeably constricted, the ends are fine and silver-white, the center has a shrinkage, the corners have clear white mouths, the tapping sound is crisp, and there is a smell similar to calcium carbide acetylene gas.
4.2.6.2 Inspection Method
The nodularization inspector takes a sample in the iron ladle after the nodularization is complete, removes the slag, pours the sample into the sand mold, and waits for the center to solidify and the surface to become dark red. Then, the test piece is quenched in water for observation. The foundry responsible engineer supervises, reviews, and confirms.
4.2.6.2 Handling of unqualified products
If the foundry responsible engineer confirms that the nodularization is unqualified, casting is not allowed, and the iron ladle is scrapped.
4.2.6.3 Inspection Record
The inspector accurately fills in the nodularization inspection record.

4.2.7 Ductile Iron Chemical Composition and Mechanical Property Test
4.2.7.1 Ductile iron inspection standards
a) Chemical composition: C 3.3-4.0% Si 2.3-3.2% Mn ≤0.3% S ≤0.02% P ≤0.06% Mg 0.03-0.07%
b) Nodularity: ≥80%. The matrix ferrite content is greater than 80%, and there is no carbide or phosphorus eutectic.
c) Tensile strength, hardness: Rm ≥420MPa, elongation A% ≥5%, hardness HBW ≤230
4.2.7.2 Inspection method
The foundry worker takes one chemical composition sample for each furnace, and the chemical composition is tested in the furnace. For every 4-5 tons of castings, one mono test piece is poured with the casting. Three test rods are made according to JD-D-001 “Ductile Iron Pipe Fitting Tensile Test Standard” and provided for physical and chemical inspection.
a) Chemical composition test: One spectral analysis specimen is left for each furnace of nodularized iron, and the spectral analysis is performed by the physical and chemical inspector and a report is issued.
b) Nodularity test: One sample is left for each package poured into the last box, and the physical and chemical inspector uses a metallographic microscope to analyze and issue a report according to JD-D-002 “Ductile Iron Structure and Nodularity Test”;
c) Hardness test: The end of the mechanical test rod is used by the physical and chemical inspector with a Brinell hardness tester according to JD-D-004 “Ductile Iron Pipe Fitting Brinell Hardness Test”.
4.2.7.3 Determination and re-inspection
If the first tensile strength test meets the standard, the batch of products is qualified. If the test rod does not meet the standard requirements, a retest should be performed. The retest method is to take another two test rods from the same sample. If both rods are qualified, the batch of products is qualified. If one of the two test rods is unqualified, the batch of products is unqualified and should be traced back.
4.2.7.4 Inspection Record
The inspector accurately fills in the inspection record, and the head of the quality inspection department reviews it.

4.2.8 Casting Inspection
4.2.8.1 Inspection standards
a) The castings should be complete in shape, free from defects such as insufficient meat, cold isolation, slag inclusion, cracks, etc.
b) The casting surface should be flat, free from collapse, iron tumors, and severe adhered sand defects; there should be no sand holes or shrinkage defects on the casting surface, the protrusion of the seam on the surface of the casting should not exceed 2mm, and the area of the surface pit should not exceed 3×3mm, with a depth not exceeding 3mm.
c) The dimensions of the various parts of the casting should meet the requirements of the standard drawings.
d) The castings should be marked clearly and completely, including: factory mark, casting material, nominal diameter, flange PN value, pipe body K value, standard number, product batch number, etc., or according to customer requirements.factory mark, casting material, nominal diameter, flange PN value, pipe body K value, standard number, product batch number, etc., or
4.2.8.2 Inspection Method
The inspector inspects each casting piece by piece.
a) 4.2.8.1-c) are inspected with calipers, internal calipers, gauges, ultrasonic thickness gauges, and thickness gauges;
b) The rest are inspected using visual inspection.
4.2.8.3 Inspection Record
The inspector accurately and truthfully fills in the casting inspection record, and the head of the quality inspection department is responsible for reviewing.

4.2.9 Machining Inspection
4.2.9.1 Inspection standards
The dimensions, angles, precision, and dimensional positions of the flanges and flanges after machining should meet the requirements of GB/T13295-2008 “Ductile iron pipes, fittings and accessories for water and gas pipelines” or the drawings.
4.2.9.2 Inspection Method
The operator performs self-inspection, and the inspector inspects each piece one by one. The dimensional inspection is performed using a vernier caliper, depth gauge, and dimensional position inspection using a platform, angle ruler, and bending ruler.
4.2.9.3 Handling of unqualified products
For machined parts that do not meet the standard requirements, the inspector should mark them if there is a possibility of rework. The workshop should be ordered to rework, and after rework, a re-inspection should be performed. The rest of the unqualified products should be scrapped, and the head of the quality inspection department is responsible for approving the inspection.
4.2.9.4 Inspection Record
The inspector is responsible for accurately and truthfully filling in the inspection record in detail piece by piece, and clearly states the conclusion. The head of the quality inspection department is responsible for reviewing and approving.

4.2.10 Hydraulic and Airtight Test
4.2.10.1 Inspection standards
Execute GB/T13295-2008 “Ductile iron pipes, fittings and accessories for water and gas pipelines” standard a) Hydrostatic test”
b) Iron temperature: Lost wax model 1580-1620℃; Static pressure line 1500-1590℃
4.2.5.2 Inspection Method
Each furnace is tested as a batch, and the chemical composition is sampled by the operator. The physical and chemical inspector is responsible for the physical and chemical analysis.