Research lock casting thermal cracking of bakelite handle a front

Proposed a bakelite handle problems
        Bakelite handle a front lock casting casting plant is one of the leading products. Since the bakelite handle parts production, quality has been stable, high rejection rate , its main problem is the casting thermal cracking , hot crack more than 60% of total waste . Since the bakelite handle parts rejection rate, and therefore a serious threat to our plant production and plant loading.
        That last piece of casting solidification hot section parts of the site to produce , test it with the results obtained coincide.
        2 bakelite handle mechanism formed by thermal cracking
        Bakelite handle formation mechanism of thermal cracking about scientific research in recent years with the expansion of a variety of claims , we believe bakelite handle film theory more convincing .
        Such theory is that when the bakelite handle solidification solidus near , there is not a small amount of liquid crystal solidified around a film composed initially thicker , thinner temperature closer to the solidus film , when all the casting solidification , film evaporates . If the liquid film contains more low melting compounds ( such as sulfur and phosphorus in steel ) , will make the actual liquid line down , expanding the range of solidification , the presence of film time is extended , and a corresponding increase in the amount of shrinkage during solidification . Final crystallization , when for some reason the casting shrinkage hindered generated between the crystal and the crystal liquid film stress at this time , and the crystal grain boundary in the film is stretched under stress , when the stress is large enough , the liquid film will crack intergranular crack formation .
        As can be seen from the above analysis , thermal cracking in the cast are
        3 bakelite handle a front lock casting thermal cracking of
        We human, machine , material , method, starting five factors , using total quality management tools and methods bakelite handle a front lock casting analysis to identify the five factors. First, bakelite handle casting material, two bakelite handle casting structure is irrational , three lining material is bakelite handle , bakelite handle four metal charge is unqualified , Fifth bakelite handle casting process failed. Improved analysis of itemized below .
        3.1 bakelite handle casting material issues
        First, the ZG 3 5 to ZG 4 5, the second is the ZG 3 5 to QT 4 0 0 a clever thermal shell casting, shell casting cold . The test results show that the ZG 35 ZG 45 to little effect ; the ZG 3 5 to QT 4 0 0 a 15 , bakelite handle thermal cracking scrap rate dropped to skillfully %, but produce large amounts of subcutaneous polished after casting porosity , casting can not be used . In addition , later changed to QT 4 0 0 A clever casting cost.
        3.2 bakelite handle casting structural problems
        Casting structure to improve the program below. Left its programs to improve the former . The results showed that the most significant impact of the program d , this structure to the hot section of the concentrated dispersion , the casting during cooling , at the same time in an area can not be pulled off solidified , do not form cracks. 3.3 lining material issues will be replaced by aluminum vanadium quartz sand sediment lining , lining neutral protection
        4 bakelite handle economic effect
        Reduce heat loss from cracking side, according to a front lock handle each car two , three yuan per meter, with an annual output by 120,000 , then it can save 108,720 yuan. By the quality of research, casting handle a front lock without 100 % Polish and flaw detection can save 151,200 yuan. Total S conclusions about 2 60,000 yuan a. Handle a front lock by changing the structure and pouring _ [ casting process parameters , the quality of the pieces to be solved . . b J pouring a selection of process parameters on the thermal cracking of casting a greater impact : the casting process parameters control well, can be put down to a very small extent hot crack .