Black Metallurgical Industry Standard of the PRC
4.3 Thermal shock fatigue resistance
4.3.1 The test results of thermal shock resistance are only used as the quality reference for the ductile iron stave cooler, and are not used as the basis for acceptance.
4.3.2 The test block size of testing for the thermal shock fatigue resistance is 300mm X 65mm X 40mm, and the test surface is 300mm X 65mm side. A total of six pieces are inspected and should be cast from six packs of molten iron.
4.3.3 The thermal shock fatigue resistance is tested by special heating-cooling-heated drum testers. The thermal shock fatigue performance parameters’ target value is:
300℃——900℃——300℃cycle 250 times without cracks
100℃——600℃——100℃cycle 1000 times without cracks
4.4 Thermal conductivity
The sample with mechanical properties meeting the standard is se*lected for thermal conductivity measurement. The thermal conductivity is not used as the acceptance condition.
Reference value: 400°C: 30W/(m•K) ~35W/(m•K)
4.5 Cooling stave cast into cooling water pipe
4.5.1 The cast iron stave of the blast furnace is cast into the cooling water pipe. The cold drawn steel pipe for conveying fluid according to GB/T 8163 is used. The seamless steel pipe for low and medium pressure boilers in accordance with GB 3087 can also be used. The material is No. 10 or No. 20 Steel, its chemical composition should meet the requirements of GB/T 699.
4.5.2 Steel strips with peeling rust are not allowed.
4.5.3 The whole steel pipe for the cooling water pipe is formed by cold bending of the pipe bending machine, and wrinkles, concave flats, peeling and scratches are not allowed in the curved portion. The cooling pipe bending radius R=(1.5D~2) D (D is the outer diameter of the steel pipe), the dimensional tolerance of the bending radius is ±2mm, and the pipe center distance tolerance is ±2mm. The shape of the cooling water pipe, such as tuyere, iron mouth and serpentine tube, can be partially hot ortho-shaped, but the cooling water pipe is not allowed to have over-burning and visually observable cracks. The pipe center distance tolerance is ±5mm.
4.5.4 When the length of the fixed length steel pipe used to make the serpentine cooling water pipe is insufficient, the seam welding is allowed, but the joint is not allowed to be in the bent part. And the joint of each circulating water pipe shall not be more than one place, and the welded protective sleeve shall be added at the butt joints of the steel pipes.
4.5.5 The thickness of the pipe wall due to bending should be less than 18% of the wall thickness according to the thickness of the water pipe, and the ellipticity of the curved portion is ≤14%.
4.5.6 After the cooling water pipe is bent and formed, a pass ball test is required. The ball is made of a wooden ball or a metal ball, and the ball’s diameter is 76% ± 0.2 mm of the inner diameter of the water pipe.
4.6 Manufacture of stave cooler
4.6.1 The cooling water pipes and the protective pipes (including the lifting lug and the cast nut) must adopt effective anti-carburizing measures, and the anti-carburizing coating is not allowed to fall off or vacant. Before the anti-carburizing treatment, the surface of the steel pipes is subjected to rust removal treatment to reveal a metallic luster.
4.6.2 The number of anti- carburizing tests for cooling water pipes is determined by the user. The methods and requirements for anti-carburizing tests are shown in Appendix A.
4.6.3 It is not allowed to directly weld the cooling water pipes in the mold.
4.6.4 Drilling iron is not allowed between the cooling water pipes and the protective pipes exposed outside the cooling stave.
4.6.5 During the casting process, the inner wall of the cooling water pipes should take measures effectively preventing from oxidation.
4.7 Stave cooler dimensional tolerance
The dimensional tolerance of the stave cooler is to be carried out according to the drawings and installation instructions. If no special requirements, implement as follows.
4.7.1 The thickness dimensional tolerance of the stave cooler is ±5mm.
4.7.2 The height dimensional tolerance of the stave cooler is ±5mm.
4.7.3 The inner and outer arc chord length dimensional tolerance of the stave cooler is ±3 mm.
4.7.4 The surface of the boss at the root of the in and out cooling water pipes of the stave coolers and the surface of the boss of the bolt holes required flat, and the height dimensional tolerance of the boss is±1.5mm.
4.7.5 All cooling water pipe inlet and outlet center position tolerance is ±5mm.
4.7.6 The dimensional tolerance of the opening radius of the tuyere and the iron mouth is ±5 mm.
4.7.7 The diameter dimensional tolerance of the temperature measurement hole, thickness measurement hole and pressure measurement hole is ±5mm.
4.7.8 The protective sleeve of the stave cooler is extended to the height of the cooling stave with a dimensional tolerance of+10-5mm。
4.7.9 The concentricity tolerance of the cooling water pipe and its protective sleeve is 2.5mm.
4.7.10 The diameter dimensional tolerance of the fixing bolt hole is ±2mm, and the centerline position tolerance is ±3mm.
4.7.11 Other dimensional tolerances of the stave cooler shall comply with the CT13 level specified in GB/T6414-1999.
4.8 Surface quality of stave cooler
4.8.1 The molding sand, core sand and sticky sand attached to the surface of the stave cooler must be removed, meanwhile, the gating root, riser root and excessive material should be removed and smoothed.
4.8.2 Crack defects are not allowed in any part of the stave coolers.
4.8.3 For local defect depth ≤5mm on the hot side of the stave cooler and area of the casting defect less than 1% of the hot surface area, only the grinding treatment is allowed, the weld repair is not allowed.
4.8.4 Casting defects of cooling stave’s cold surface:
When the depth is ≤5mm, the single defect diameter is ≤100mm, no more than two in l00mm X 100mm, no treatment is possible; when its depth is ≤10mm (glossy stave cooler) or ≤ 15mm (inlaid brick stave cooler), a single defect diameter ≤ 40mm allows welding repair, but each cooling stave must not exceed three, the welding repair zone should be properly insulated after welding to avoid cracks.
4.8.5 If the casting defects exceed the specified range of 4.8.4 of this standard or appear local holes, in the case of guaranteeing the performance and appearance quality, it can be welded and repaired with the consent of the contractor.
4.8.6 Surface roughness is tested according to GB/T6060.1-1997, and the surface roughness Ra≤100μm is required.
4.9 Cooling stave anatomical inspection
4.9.1 In mass production, the stave cooler can be anatomically inspection, and the quantity and requirement of anatomy is determined by both parties.
4.9.2 The anatomical inspection of the stave cooler sees Appendix B.
4.9.3 If nodular cast iron stave for sampling and testing sets of drilling bolt holes, the central portion should reach the following metrics: Metallographic examination: ball level 3 ~ 5, matrix ferrite content ≥80%.
4.10 After casting of the stave cooler, appropriate process measures should be taken to eliminate internal stresses in the casting. When using the annealing process, measures to prevent water pipe oxidation should be taken.
4.11 Cooling stave ball test: the diameter of the ball is 2mm smaller than the ball diameter specified in 4.5.6, and the forward and re*verse directions can pass smoothly is qualified.
4.12 Cooling stave water pressure test: pressure 1.6MPa, hold for 15min, and tap the parts of the cooling stave with o.75kg steel hammer. The voltage is first regulated for l0min, and the pressure drop of the pressure test system is allowed to be ≤3% within 5 minutes later.
4.13 Brick insert to cooling stave
4.13.1 The dimensions and physical and chemical indicators of the refractory bricks used in the bricks must meet the design requirements.
4.13.2 Cooling stave bricking methods are divided into hot brick and cold brick.
4.13.3 hot brick
18.104.22.168 The refractory bricks should be dried before casting. When the size of the embedded refractory bricks is not suitable, only sawing bricks or grinding bricks are allowed. A whole piece of refractory brick must be placed on the edge of the stave cooler.
22.214.171.124 Corresponding technical measures should be taken when hot bricks are inserted to avoid cracking of refractory bricks due to shrinkage of the castings.
126.96.36.199 Hot-inlaid refractory bricks are not allowed to have per-penetrating cracks, and refractory bricks with local cracks do not exceed 5% of the total.
188.8.131.52 Drilling iron is not allowed between hot-inlaid refractory bricks.
4.13.4 cold-inlaid brick
184.108.40.206 The inner surface of the dovetail groove of the cooling staves’ bricks must be smooth, and between each of the three troughs should inspect with the whole sample, passing as qualified.
220.127.116.11 The gap between the refractory brick and the inner surface of the cooling stave’s swallow-tail groove is lmm-3mm, and the gap between the brick and the brick is 1mm to 3mm.
18.104.22.168 The refractory mud between the refractory brick and the cooling stave body, the refractory brick and the refractory brick must be full and free of voids.
22.214.171.124 After cold-inserted bricks, the cooling staves should be naturally dried or dried in the kiln to a certain strength before being transported.