Papers by Keyword: Cleanliness

Abstract: M2 steels, the typical Co-free high speed steel (HSS) possessing hardness level of 63~65 HRc, are most widely used for cutting tools. On the other hand, Co-containing HSS’s, such as M35 and M42, show a higher hardness level of 65~67 HRc and used for high quality cutting tools. In the fabrication of HSS’s, it is very important to control cleanliness and eutectic carbide structure of the ingot and it is required to increase productivity at the same time. Production of HSS ingots includes a variety of processes such as casting, electro-slag remelting (ESR), forging, blooming, and wire rod rolling processes. In the present study, electro-slag rapid remelting (ESRR) process, an advanced ESR process combined by continuous casting, was successfully employed to fabricate HSS billets of M2, M35, and M42 steels. Distribution and structure of eutectic carbides of the billets were analysed and cleanliness, hardness, and composition profile of the billets were also evaluated.

Abstract: The source of inclusion in IF steel end slabs after reducing the casting remnant were studied by means of total oxygen and nitrogen content analysis, original position analyzer for metal (OPA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Slims. The results show that: reducing the casting remnant have little influence on reoxidation in continuous casting process, the size of micro-inclusions are mostly smaller than 5 μm. The size of large-sized inclusions in end slab are mainly trapped in mold, they are mostly from 140 μm to 300 μm and over 300 μm, which accounted individually for 19.94% and 73.21% of total large-sized inclusions. In the end of a cast, decreasing the casting speed with slower speed changing rate can decrease the slag entrainment index of hot rolled coils from end slabs.

Abstract: The air change rate and cleanroom garment have a great impact on cleanliness and operating cost of cleanroom. This paper use the method of numerical simulation to research the effect on cleanliness with different air change rate and cleanroom garment in Grade B cleanroom. The results show the air change rate of 20/h will meet the requirements of the specification and the garment cover whole human body will decrease the particles emitted from human body mostly.

Abstract: Remanufacturing Cleaning is an important process during the remanufacturing engineering, which is unique and significantly different from the manufacturing process and has an important effect on ensuring the quality of remanufactured product. The cleanliness it achieved is an important quality index of remanufactured products, which directly affects the surface analysis, surface inspection, remanufacturing processing and assembly process and further affects the quality and cost of remanufactured products. First of all, this paper gives a systematic induction and summary on the cleaning techniques and methods of remanufacturing processes such as high-pressure water jet cleaning, ultrasonic cleaning and chemical cleaning. At the same time, the paper carries out a comparative analysis on merits and demerits of each cleaning technology. Secondly taking the remanufacturing cleaning of concrete pump truck for an example, this thesis emphasizes on introducing the cleaning techniques of pump truck vehicle cleaning and parts cleaning after dismantling, and then analysis the deficiencies of concrete pump truck cleaning from the perspective of resource and environment attribute. Finally, the paper gives development trend and prospect for the remanufacturing cleaning technology of concrete pump truck.

Abstract: High Power Laser System (HPLS) is a large optical instrument, provides extremely high temperature and pressure conditions for inertial confinement fusion (ICF) and high-energy-physics research. It contains large number of optics and which would be easily damaged due to high fluence of laser power. The contamination control of optical surfaces has a great significance to ensure the performance of the system and decrease costs. This paper discussed the background and development of cleanliness control techniques in high power laser systems, including contamination induced laser damage (CILD), contamination inspection, optical surface cleanliness degradation and maintaining.

Abstract: By means of Oxygen and Nitrogen Analyzer, Metallographic Examination, SLIME, SEM, EDS, etc, the cleanliness of ultra-low carbon steel first slab produced by LD-RH-CC, and the comparative analysis with the cleanliness of normal slab is studied. The results show that T[O] and [N] are obviously decreasing with the increasing of casting length. The micro-inclusions and large-inclusions are generally decreasing with the increasing of casting length. The micro-inclusions of the first slab are mainly from deoxidization products and reoxidation of liquid steel. And the sources of large-sized inclusions mainly are reoxidation of liquid steel, slag entrapment in mould or tundish and stuffing sand. The cleanliness of ultra-low carbon steel first slab is closed to those normal slabs at the length of 3.5m.

Abstract: The cleanness of 30Cr2Ni4MoV steel was researched by chemical analysis, SEM and electrolytic experiment. The results show that the large-sized inclusions in the casting is the direct reason for the product to scrap. It found that there is a increase trend of large-sized inclusions and oxygen content from VD to pouring process with a cleanness detection of smelting process. It have achieved a good effect by adopting some measures to improve steel cleanliness which includes controlling the carbon content of EAF tapping reasonablly, low melting point controlling of inclusions, extending soft blow time and optimizing the flow field of tundish. The quantity of inclusions has reduced from 38.8 per square millimeter to 16.0 per square millimeter. The oxygen content has reduced from 58 × 10-6 to 32 × 10-6, and the nitrogen contents has reduced from 85 × 10-6 to 70 × 10-6 after process improvment.

Abstract: In order to meet the requirement of industrial production of cleanliness steel, studies on desulphurization, deoxidization and inclusion control have been carried out. On this basis, comprehensive technologies of ladle slag control have been proposed. And these technologies are used in the production of 27CrMoNbV steel, which meet the requirement of cleanliness steel production with T[O]≤15×10-6，[S]≤0.005%, and level of inclusion not more than 1.0 as well.

Abstract: Nozzle blockage is easy to take place in continuous casting process when producing 38CrMoAl steel due to high content of aluminum ([Al]=0.7%~1.1%). Slag-steel reaction will lead to large transformation for composition of molten steel and performance of slag on the condition of traditional high content of SiO2 in slag. And it will reduce the cleanliness of steel as well. The control target of refining slag and tundish powder has been gotten through the analysis of refining & continuous casting characteristics of high aluminum steel. Based on this, the content of Si and Al in molten steel can be controlled accurately, and the cleanliness of steel has gone to a higher level. Moreover, mold powder with high basicity and vitrification ensures the stability of slag after sorbing Al2O3 inclusions in theory. Continuous casting can be carried out successfully with the control of inclusion morphology through slag washing during tapping. Industrial practice shows that Si content is 0.25%~0.40%, Al content is 0.80%~1.00%, S content is below 0.004% and T[O] is below 0.0015% in steel products. Moreover, casting bloom with good surface quality is achieved, and the rate of bloom without cleaning is as high as 100%. With all these countermeasures, 38CrMoAl steel can be continuously cast for more than 6 heats.

Abstract: Optimum performance of metal in the die casting shop in terms of metal loss, sludge generation, and high quality and consistency in mechanical properties of the die cast components are becoming increasingly important. In this context metal quality both from alloy producers’, die casters’ and end users’ perspectives is critical. The term metal quality can be defined to include 1) chemical composition, 2) inclusions and porosity inside the metal, 3) the surface appearance, and 4) consistency. This definition may apply to ingots as well as die cast parts. When the ingots are remelted and processed in the die casting shop, the effect of ingot surface quality and porosity on performance and properties is usually overshadowed by the quality of the processes in the die casting furnace. The paper discusses how the alloy gradually loses its pre-history. If the metal quality becomes inferior, housekeeping may become notoriously difficult, affecting important performance indicators such as up-time of operation and scrap rate. In partnership with the individual die casters, Hydro Magnesium offers assistance and audits to further improve the die caster’s performance and products.