Nodular cast iron manhole cover of Xushui cement manhole cover manufacturer is the most mainstream manhole cover in the manhole cover market. It has good pressure resistance and high strength. It has even reached the technical strength of cast steel on some indicators. More than ten years of in-depth research, summing up a unique set of production processes and processes, the following introduces sharing and communication with everyone.
Production process of nodular cast iron manhole cover
A. Raw material control:
a. pig iron:
Each batch of pig iron must be inspected when entering the factory.
C% SI% Mn% P% S%
＞ 3.33 ≤1.4 ≥0.20 ≤0.08 ≤0.04
You can only enter the warehouse if you pass the test.
b. Detection frequency: three samples per batch below 30 tons
More than 30 tons of five samples per batch
c. Reheating material: In order to ensure the stable product quality, the input of reheating material is strictly controlled within 30%.
d. Rare earth magnesium silicon iron alloy
Grade: FeSiMg (T-II) RE
RE% Si% Mn% Ca% Ti%
3-4 40 8-9 2-3 <2
3) Smelting and control methods
A. Smelting method (nodular cast iron manhole cover, well ring)
a. 1.5 ton dual frequency electric furnace melting: the temperature of the furnace is 1400--1500 ℃
b. Weight of each molten iron: 1500kg / bag
c. The amount of rare earth magnesium alloy added 1.4% -1.6%
B. Control method
a. Before each ball of molten iron spheroidizing, measure the temperature of the furnace once, the control range is 1400-1500 ℃.
b. After the spheroidization of each package of molten iron is completed, the temperature of the molten iron is measured once, and the control range is above 1360 ° C.
c. The five-element testing of 1-2 samples of raw molten iron is performed daily to control the stability of the casting material and the use of furnace charge.
d. The longest pouring control time for each package of molten iron is 10 minutes (after nodularization reaction). If this time is exceeded, it shall be treated as scrap.
e. After pouring each package of molten iron, insert a pre-made label (the serial number of the package is engraved on it) into the pouring cup of the casting of the package to prevent confusion between different packages.
f. The tensile test rod blank is made at the end of pouring of each package of molten iron. As a test batch, the mechanical properties, metallographic structure and hardness are tested.
g. When falling sand, stack them separately according to the number plate. Different packages cannot be confused. Wait for the test results of the test rod and metallography.
h. After the mechanical properties of the test rod are qualified, notify the workshop to clean up. Unqualified packages are discarded one by one according to the number on the sign.
4) Inspection standards
A. Inspection of manhole cover: strictly in accordance with inspection standards.
a. Appearance: No obvious casting defects, clear pattern and clear handwriting.
b. Flatness inspection: Check the flatness of the manhole cover with special tires.
Make a diameter of the product size and a depth of 37mm. The above dimensions are machined. The manhole cover is placed in the tire. There must be no shaking and noise. The manhole cover must not be higher than the tire.
c. The load is checked by sampling
The pressure test is performed on the press, and the manhole cover pressure is 360KN or 210KN to confirm the qualified batch.
B. Well ring inspection
a. Appearance: No obvious casting defects.
b. Use special tools to detect the diameter of the well circle. The diameter of the control range is the size of the well cover and the depth is 40mm. The bolt holes must be inspected one by one with a special inspection tool.
C. Coordination and spray paint inspection
The aT rubber ring is matched with the well ring. The rubber ring should be flat in the T-shaped groove, not too long or too short, firmly bonded, and the fit gap should not be greater than 1mm.
b. The assembly and assembly of the manhole cover and the well frame should be flat, without shaking and sound, and the height of the cover and the frame should not exceed 1mm.
The cT rubber ring is adhered firmly before painting, and the manhole cover (ring) is painted uniformly without rust spots.