JB/T 6887-2004Technical requirements for iron castings for fans, blowers and compressors (English PDF)

3.1 Materials

All types of cast irons in this Standard shall use the material designations which comply with the provisions of GB/T 9439, GB/T 1348, GB/T 9437, GB/T 8491,

GB/T 3180.

3.2 Production method and heat treatment

Casting should be annealed or use vibration aging method to eliminate internal stress. The production method and heat treatment of castings shall be decided by the supplier. However, it must satisfy the designation specified in this

Standard and relevant technical performances. The repeated heat treatment of adjusting mechanical properties and processing properties must not exceed twice. If it uses vibration aging, it shall strictly follow the provisions of JB/T 5926.

When there are special requirements for heat treatment and internal stress elimination, it shall indicate in drawing or order agreement.

3.3 Mechanical properties and chemical composition

3.5.1 General

The geometrical shape and dimensions of castings shall comply with the pattern or appearance when ordering and relevant agreement. The wood mold should be implemented according to the second grade of precision of JB/T 7699.

The pattern draft not specified in the process shall comply with the provisions of Annex A.

3.5.2 Casting machining allowance

3.5.2.1

If there is no special requirements for drawing, order agreement, casting bottom and side machining allowance shall be implemented according to H grade provisions of GB/T 6414-RMA (see Annex B). The top surface machining allowance is 0.25 times of the corresponding bottom surface.

3.5.2.2

The purchaser shall specify on the drawings the surface to be pre- machined by the foundry and the machining allowance required for the final machining, in order to achieve the machining allowance required by the pre- machined state or meet requirements of re-finished casting after secondary aging. The machining allowance is 1.2 ~ 1.5 times of the grade H value of GB/T 6414-RMA.

3.5.3 Unnoted dimensional tolerance

The general dimensional tolerance not specially noted in the drawings shall be implemented according to CT12 of GB/T 6414. See Annex C for its tolerance value. General tolerance zone should be symmetrical distributed, i.e., half of the tolerance is positive and the other half is negative. For some special cases, based on agreement of the designer and the casting producer, the tolerance can be partially or wholly positive or negative.

3.5.4

Dimensional tolerance of special parts of cast iron for fans blower and compressors

3.5.4.1

The dimensional tolerance of casting wall thickness, rib thickness, web thickness and back room, diffuser blade thickness, when the basic size is less than 20 mm, shall be implemented according to CT11 of GB/T 6414; when the basic size is equal to or greater than 20 mm, it shall be implemented according to CT13 of GB/T 6414.

3.5.4.2

The thickness tolerance of facetted flanges and fluid inlet and outlet flanges in chassis, bearing body, gearbox and oil pump, shell and other castings shall be implemented according to CT13 of GB/T 6414.

3.5.4.3

Because the wrong box eccentric wheel, shaft and other rotating castings produce coaxial deviation, when ensuring sufficient processing capacity of the shaft hole and the outside of rim, the tolerance of concentricity […]

3.9.2

small pores, trachoma, slag, shrinkage and shrinkage and other defects

which do not require repairing on other castings other than 3.9.1, the specific provisions on defects which do not require repairing are as follows:

a) small defects not exceeding the limits specified in Table 4 do not require repairing;

b) each dense pore area shall not exceed 300 mm

2

; see Table 4 for other parts and scope;

c) the depth of shrinkage defect of static casting, parts which do not store thin oil and non-pressure-bearing parts must not exceed 6 mm and half of the wall thickness; the defect area shall not exceed 15% of this shrinkage area (hot section) but the maximum does not exceed Phi 25mm;

d) for hubs, pulleys, semi-couplings and other rotating parts, after machining, on shaft hole surface, within the range of which the distance to both ends is radius length, no defects are allowed: the defect depth of other parts on shaft hole inner surface does not exceed 3 mm; the diameter does not exceed 1/5 of shaft diameter. When the circumferential distance between two defect edges is greater than the shaft diameter, its defects are allowed.

Table 4 Range of defects which require no repairing mm

Casting type

Part

Hole name

Hole size

Hole depth

Pitch

Distance from the edge of the face

The number of hole at per

100 cm

2 […]

3.11.1

The leakage test brushed with kerosene should be carried out for

gearbox of thin oil storage, bearing box, fuel tank and chassis of which the working pressure is less than or equal to 0.25 MPa (gage pressure), pump, shell, flesh, before priming (preferably prior to annealing). After cleaning the inner and outer surface of the casting wall, it shall apply kerosene evenly to one side of the test surface (at least three times), so as to make the surface sufficiently infiltrated. After 30 min, observe the other side. It would be qualified if it has no oil stain. If there is no special requirements for kerosene filling test, it shall be indicated in the drawing or order agreement.

3.11.2

The hydraulic test should be carried out for water-cooled bearing runner section under pressure and various chassis of which the working pressure is greater than 0.25 MPa (gage pressure), pump housing, valve body.

The test pressure is 1.5 times the maximum working pressure. There is no leakage within 30 min of pressure holding.

3.11.3

For castings used for fan housing of toxic or flammable gases, it should use an inert gas. After applying pressure to the rated pressure (1.5 times the maximum working pressure of chassis), hold the pressure for 30 min. Use bubbling liquid to examine for no gas leakage.

3.12 Primer

3.12.1

After finishing, heat treatment and examination as qualified for casting, it shall carry out the shot blasting or roller cleaning to non-machined surface according to relevant provisions in JB/T 6886, so as to achieve the cleanliness of Sa21/2 level.

3.12.2

Within 24h of shot peening treatment, the casting should be primed.

Before priming, it should use the water-free compressed air or vacuum cleaner to clean the dusts on the castings.

3.12.3

If the drawing or order agreement has no special requirements, the iron red anti-rust primer should be evenly applied on the non-machined surface of casting.

4.1

The castings shall be inspected and accepted by the technical inspection department of the supplier according to technical requirements of Clause 3. The purchaser has right to inspect the castings. If the purchaser checks the implementation on site, the supplier should provide all reasonable convenience.

4.2

The method of specimen selecting is carried out according to 3.3.3. If castings require heat-treatment, its specimen and casting shall use heat treatment of same furnace. If only the internal stress is eliminated, the specimen may not be subjected to heat treatment.

4.3

Test method for mechanical properties of castings, tensile test on gray iron castings and RT type heat resistant castings, bending test of high-silicon corrosion-resistant pieces shall be carried out according to JB/T 7945. Tensile test of ductile cast iron and heat-resistant ductile cast iron (RQT) shall be carried out according to the provisions of GB/T 228. Impact test of medium manganese nodular cast iron is carried out according to GB/T 229. Its Rockwell hardness test is accordance with GB/T 230. Brinell hardness test of other various castings shall be carried out according to the provisions of GB/T 231.1

~ 3. When the hardness is directly determined on the casting surface, it shall remove a thickness of not less than 2 mm from the casting surface and carefully flatten. The position for determination should be selected at the working surface of which the distance to the casting edge is not less than 10 mm.

4.4

The chemical analysis of castings shall be in accordance with the provisions of GB/T 223. Sample for chemical analysis can be taken from the same batch of hot metal rod (block) or casting body. The sampling site should be at the position 6 mm below the surface layer.

4.5 Batch division

a) Castings cast from the same pack of molten iron are one batch;

b) The maximum weight per batch casting is clear shoveled 2000 kg casting in good condition. If the weight of one casting is greater than 2000 kg, it shall become a batch separately;

c) When it continuously melts a large number of molten iron of same designation, the maximum weight of each batch must not exceed the casting weight cast within 2h. If the volume of one designation of molten iron is very large, and under the fixed raw materials, melting process and stable production conditions, agreed by the supplier and the purchaser, it shall also combine several batches into one group for acceptance;

d) Once a pack of ductile cast iron is treated, it should make this pack of molten iron as a batch;

e) If the casting attached with cast test rod (block), each piece can be determined as a batch separately.

4.6

The material acceptance of castings shall be performed according to the provisions of 3.3. Each batch shall at least take a group (three pieces) of specimens. Carry out relevant mechanical properties tests and chemical composition analysis. In the test, use one specimen to carry out the test at first.

If it meets requirements, this batch of castings shall be qualified in material. If test results cannot meet the requirements, two specimens shall be allowed to extracted from same batch of specimens for re-inspection. If all meet requirements, this batch of castings shall be regarded as qualified in material.

4.7

Visually inspect the surface, appearance of casting piece by piece. For the first piece and the important castings, it shall carry out the size and geometry inspection piece by piece according to 3.5. General castings and castings which are produced by the method ensuring the dimensional stability can be selectively examined. The roughness of casting surface shall be inspected according to GB/T 15056. If it fails to meet requirements, grinding and reworking is permitted.

4.8 Inspection of welding quality

a) It should inspection the preparation of welding defects one by one according to the requirements of 3.10.2.1 b) and 3.10.2.1 d);

b) The welding method and welding rod used shall be in accordance with relevant provisions of 3.10.2.1 c);

c) After defect welding, it shall inspect the quality of each welding area one by one, in accordance with requirements of 3.10.2.3. Use hammer or

Shore hardness tester to inspect the hardness;

d) The number, size and area of the welding defects shall not exceed the provisions of this Standard;

e) It shall use effective method to inspect defects like cracks on the castings.

4.9

For castings which require leakage test according to drawing, technical document or order agreement, it shall carry out the test one by one according to requirements of 3.11. If the specimen test is unqualified, re-working is allowed.

Re-carry out the leakage test after re-working.

5.1

Qualified castings after inspection should have mark of the production technology inspection department. The mark can be printed or painted (in general, it should use white paint to mark the qualified product).

5.2

When castings are delivered or leave factory, it should have product certificate complying with this Standard, including:

a) the supplier's name;