1 4302 COLD SHUT – COLD FRACTURE I. APPLICABLE TO… II. IDENTIFICATION III. EXPLANATION IV. LITERATURE V. ROOT CAUSES & SECONDARY CAUSES VI. ACTIONS ON ROOT & SECONDARY CAUSES VII. PROCESS CAUSES VIII. ACTIONS ON PROCESS CAUSE Gietech BV has to its best knowledge compiled the file and cannot be hold responsible for problems if applying the data and actions without proper control, evaluation and surveillance of the reader. Gietech BV can assure that the data are collected, evaluated and exposed with all the experience of Staf Henderieckx, its owner. The reader should realise that the author does not know the conditions in the reader’s foundry, which indicates that a particular verification and selection of solutions can be required. NO INFORMATION FROM THIS FILE CAN BE COPIED, MULTIPLIED OR SOLD WITHOUT THE WRITTEN PERMISSION OF GIETECH BV, WHICH HAS THE TOTAL COPYRIGHT OF THIS FILE. 2 I. APPLICABLE TO… STEEL IRON Carbon steel Gray iron Low- & medium-alloyed steel Ductile iron High alloyed steel Compacted iron Corrosion resistant steel Malleable iron Heat resistant steel White iron Manganese steel Gray iron alloyed Chromium steel Ductile iron Austempered ADI Other steel Ductile iron Ni-alloyed Ductile iron Silicon alloyed White iron Cr-Ni alloyed White iron Cr-alloyed Other iron ALL STEEL X ALL IRON X MOULDING Green sand hand moulding Ceramic moulding Green sand medium pressure Ceramic moulding lost wax Green sand high pressure Metal mould No bake sand Centrifugal casting Vacuum moulding Lost foam Plaster mould Full mould (foam) All MOULDING x MELTING Cupola cokes Arc furnace Cupola (cokeless) gas Main frequency furnace Cupola duplex Induction furnace medium Hz Rotary furnace Air Induction furnace high Hz Rotary furnace oxygen Channel furnace Flame fired crucible furnace Vacuum furnace All MELTING x 3 II. IDENTIFICATION II.1 TOOLS II.2 DESCRIPTION II.3 PICTURES II.1 TOOLS IDENTIFICATION TOOLS NDT – VT x Destructive testing x NDT- Microscope x Mechanical testing NDT- PT x Physical testing NDT-MT x Measuring dimensionally hand NDT-UT x Measuring dimensionally 3-D NDT-RT x Measuring dimensionally laser NDT-Other x Analysis testing: spectrometer Roughness test Analysis testing: other ANY TESTING Paperwork 4 II.2 DESCRIPTION LOCATION related to Cope / drag Chill location % presence % presence Riser location Vent location % presence % presence Pouring system (ingates) NO RELATION x % presence The defect consists of a crack, called cold shut or a fracture / breakage. Cold shut, also called cold lap, is a casting defect caused by imperfect fusion of molten metal streams (mostly coming together from opposite directions) or by a folding over of the metal stream. Crack like indication at the surface of the casting. The appearance is like an open crack but the walls are smooth and shape is rounded. Very often, oxide-films are present. Indication which looks like a crack but is mostly small and not very deep and has a rounded shape and smooth walls. It mostly appears in long (thin) sections and in the middle of two ingates, where the different metal streams touch each other. It is more pronounced if the metal is prone to oxidising (chromium alloyed). It is less harmless as a crack because it will not grow like cracks. Sometimes, in extreme cases, the crack can be even long and deep (completely through the section). The defect is mostly located in the top of the casting, especially if the top section consists of a large thin section. It is anyhow far from the ingates. The defect is mostly surrounded by an oxide film / dirt that restricts / avoids the fusion. Sometimes it is somewhere in the casting if it is caused by an interrupted pouring. This defect will be detected by UT and or RT testing the inside the casting and by PT or MT if the presence and the connection of the cold shot with the surface can be found. A destructive test can assure the presence and severity of the defect. The casting is normally rejected unless the casting base material is very well weldable (steel), but even than it should be considered to do it. It will never be allowed in white iron (even any iron) castings. Anyhow the customer has to agree with the repair. The defect is many times combined with slag (first dirty metal). 5 The defect is different from the defect 4301, which is more round crack and straight ones as defect 4302. The defect can be similar with defects 6303 and 6304, showing marks on the surface. But they are classified as surface condition defects. 6 II.3 PICTURES II.3.1 Principle Cold shut – principle Cold shut – principle Cold shut – principle Cold shut – principle II.3.2 Castings Cold shut – ductile iron Cold shut – gray iron – green sand Cold shut - steel 7 Cold shut – fold over type – green sand II.3.3 NDT tests 8 III. EXPLANATION III.1 EXPLANATION III.2 REQUIRED INFORMATION III.1 EXPLANATION The defect is a linear crack in the metal, indicating that two different metal streams are not fused anymore or that some metal did fold over. 1. Metal If this first metal can enter the mould cavity, it can initiate the defect in the casting, especially due to the metal temperature (pouring temperature and or metal temperature in the mould cavity) that is low and the metal is dirty. The first metal always has some splashing and turbulence and it will clean the pouring system. It is also in contact with the cold mould, cooling extra. The problem will be larger in green sand moulds. Dirty metal, having slag and sand from the furnace and ladle and pouring box, will increase the risk for cold shut. Materials that are sensitive to oxidizing will also be more prone to have this defect. If the material has a low fluidity, the risk also increases. Silica- and aluminium-iron as well as ductile iron are prone to this defect. Also high chromium steels can suffer from this defect. If the pouring temperature is low, especially the temperature range (Tp – Tl). The metal will cool very quickly and cold shut risk will increase. 2. Pouring system The pouring system can initiate a lot of splashing under the sprue and in the sprue (non-pressurized pouring system), mixing the metal with air (oxygen) and creating slag (and dross in ductile iron). The same effect will happen if the turbulence in the pouring system is high. h9 Long and small section runners will decrease the metal temperature. The longer the flow of the metal in the casting, the higher the risk for the defect formation (few ingates leads to longer metal flow) due to a larger metal cooling. First metal running into the mould cavity. When the metal speed in the ingates is high, the metal can fold over (metal speed between 0,4 and 0,75 m/s) or be injected with high turbulence (metal speed > 1 m/s). The same will happen if the metal (leaving the ingates) hits cores or mould walls. If the venting section is too small, the metal will have to press the air out and it will lose quite some extra temperature. The longer the pouring time, the more the cooling of the metal, the higher the risk for getting cold shut defects. If the pouring box is incorrect dimensioned, the pouring can be irregular and at the end of the pouring, all slag and other inclusions will be sucked in the sprue due to the syphon effect of the metal. Interrupted pouring will have a similar effect. 3. Casting shape The thin sections will increase the metal cooling and increase the risk for cold shut. Thin vertical sections will increase the metal speed and can sometimes lead to fold over of metal. Thin horizontal large sections on top of the casting will increase the cooling of the (already cold) metal. By doing this, the risk for cold shut increase. Abrupt section changes in horizontal level (section times speed is constant). 4. Others If the mould has a lot of chills and or cooling sand, the temperature of the metal will decrease more. Especially green sand (with a higher water content) will increase the risk. Non-preheated metal moulds will have frequently the defect. 2,5 - 3 DDS Y P HO N EFF E CTP O UR ING BO X W IT H M E T A LS P RU E10 III.2 REQUIRED INFORMATION REQUIRED INFORMATION PRODUCTION Material Melting & pouring Chemistry (C, Si, Mn, S, P) x Highest temperature in furnace Chemistry (alloying elements) x Time on temperature (> Tg) Chemistry (residual elements) Number of taps Other: Temperature between taps Metallurgical treatment: type Moulding Result O-, H-, N-content Green sand: clay, burnt clay Result Al-, Ti-content Green sand: green strength Result Mg-, RE-content Green sand: strength Time treatment to pouring Green sand: water content Pouring temperature x Green sand: permeability Pouring time x Green sand: sand/metal ratio Thermal analysis No-bake sand: type of sand Ladles x No-bake sand: sieve analysis Heat treatment No-bake sand: shape of sand Heat treatment cycle No-bake sand: LOI Cooling No-bake sand: LOI * Condition cooling device No-bake sand: S-content No-bake sand: N-content Shot blasting / fettling No-bake sand: P-content Shake out temperature No-bake sand: Acid demand Type of shot blasting No-bake sand: sand/metal ratio Type of PS / riser removing No-bake chemicals Type of fettling Type of coating & liquidiser Coating thickness / layers Quality control Coating drying Report NDT-test x Ceramic sand: type of sand Tensile test result Ceramic sand: mould thickness Hardness test result Ceramic sand: drying type & time Charpy-V test result Ceramic sand: wax-removing Other tests Ceramic sand: pre-heating Pouring system & risers & chills Metal mould: type and thickness Pouring system design x Metal mould: coating type First metal x Metal mould: coating thickness Venting x Mould: pre-heating Pouring box x Other info Type of risers Weather conditions: humidity Type of chills x Weather conditions: temperature Type of sealing
铸造文库