said. “But what you are really selling is that the material in that part is going to meet certain properties. The more control you have up front, the more consistent those properties will be.” Further control up front can be ob-


tained by controlling the material that makes up the melt by weight. “Let’s say you are making a furnace


of iron and you use 25% returns, 25% steel scrap and 50% pig iron, and the typical charge is 4 tons. But you don’t know exactly what each material weighed,” Muratore said. “These are engineered castings, and they ought to be measured with an engineering mindset. Measurement should be a quantitative, not a qualitative, weight.”


The frequency with which a metalcasting facility checks the dimensions of its casting is often dictated by the customer, either through a specific testing criteria or the percentage of bad castings it allows in a delivery.


comparing the results from the manual tests to the automatic control system since measurement parameters are dif- ferent. For instance, the sand might be rammed pneumatically in the shop or with the green sand control system but hand-rammed in the floor or lab test. “Pay attention to a change or varia- tion, rather than the number,” LaFay said.


Quality Melting The key to quality inspec-


tion, according to Schorn, is to perform a test or inspection as soon as possible after the characteristic you are testing has been established. “For instance, it’s better to


check chemical characteristics while the metal is still molten, rather than to verify castings that you made from that melt,” Schorn said. Muratore suggests chemical


analysis should be performed as far as possible on the front end, before pouring. The goal is to stabilize the metallurgical quality of the melt before you perform additional treatment or inoculation. “If I’m applying the same inoculant, but the base iron is varying, I’ll get different end results,” Muratore said. “If you measure the melt and it’s not consistent, you have the opportunity to change that quality. Once you’ve treated


24


it though, now you are committed.” Metallurgical inspection of your


melt can be performed with a so- phisticated computerized thermal analytical tool, but analyzing simple chill wedges can provide important quality information, as well. “When a metalcaster sells a casting, it has a shape and a look,” Muratore


Put Your Data to Work Results from inspection and tests are


recorded and tracked for internal and external use. Externally, many metal- casters are required by their customers to provide information that correlates with the heat or production lot they are shipping. In those cases, the customer dictates what data is recorded and how the information is delivered. Internally, testing data is used for immediate corrective measures and overall process improvement. “There ought to be a planned


Sand that is rammed pneumatically on the casting floor is likely hand rammed in the lab. This could cause a difference in data, so pay attention to the data’s trends rather than its numbers.


reaction for data that is out of specification,” Schorn said. “And if it is significantly out of control, then some significant adjustments need to be made.” A reaction plan can include containment activities for the out-of-spec castings, molds or cores, parameter adjustments to return to specification, customer notification, or scrap- ping or repairing parts. “The focus of all tests and inspections is to provide for quality improvement,” Schorn said. “In order for that to occur, it really needs to be timely. The frequency with which inspection is performed [on a casting] should recognize the risk of parts not performing. If it’s a high risk, you need to test more often.” If the results are within the specifications set for the part or process, the information still can be used to improve operations. According to Schorn, the goal of a metalcaster should be to have


MODERN CASTING / July 2010


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