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American Centrifugal, General | Centrifugal Tubes, General
Machining | Standards, Practices, and Specifications
Quality Control | Marketing Methods | Literature
AMERICAN CENTRIFUGAL, GENERAL
GQ1: In what areas are you most competitive?
GA1: Non-standard sizes, (OD's, walls and lengths) - 10" OD and larger being favored, special chemical analyses or unusual analyses in small quantities, heavy wall thicknesses are especially favored and fabricated assemblies using centrifugals.
GQ2: Can you cast flanges on your tubing?
GA2: Yes, we are able to cast a flange on one end of a tube and, if the material grade allows welding, we can fabricate flanges at other areas on the tube.
GQ3: What are your typical schedules?
GA3: Depends on how much work is required by us. For example, rough as-cast tubing - 3 weeks, rough machined - 4 weeks, finish machined - 5 weeks, fabricated assemblies - 6 weeks and up. The schedules will vary depending on the total machine time required. Special schedules are available upon request.
GQ4: What services other than casting do you offer?
GA4: We offer complete facilities for heat-treating, welding and fabricating, machining, dynamic balancing and non-destructive testing. We also have facilities for manufacturing heavy static castings.
GQ5: What materials do you cast?
GA5: We are capable of casting Plain Carbon Steel, Low-Alloy Steel, High-Manganese Steels, Cast Irons, Ductile Irons, Stainless Steels and various custom alloys. A general rule of thumb is if the material contains the element Iron (Fe) in its chemistry, we can most likely cast it.
CENTRIFUGAL TUBES, GENERAL
GCQ1: What are the advantages of centrifugal tubes over seamless and turned and bored forged tubes?
GCA1: The principal advantage is that we offer the engineer freedom of design. We offer a stepless range of outside diameters from 4" to 55", wall thicknesses varying from 1/2" to 10", and lengths up to 24 feet; longer lengths can be furnished by welding.
GCQ2: Other advantages?
GCA2: We offer a wide range of compositions and mechanical properties through various heat treatments. Tensile strength, hardness and impact properties can be designed for the particular application by controlling the composition and heat treatment. We have the further advantage of being able to produce small as well as large quantities economically. To summarize, we offer the design engineer the tubular product needed to do a specific job. Some of the other advantages of centrifugal tubes over seamless tubes and turned and bored forgings are: dimensional stability, inherent concentricity, and non-directional mechanical properties because of equiaxed grain structure.
GCQ3: What is your maximum pouring weight?
GCA3: This figure varies depending on the outer diameter of the casting, but a good rule of thumb is 40,000 lb casting weight.
GCQ4: What are your tolerances on straightness, wall thickness, uniformity, and concentricity of as-cast tubes?
GCA4: American furnishes as-cast steel tubing in up to 24-foot lengths, straight within .125" TIR. Tubes of other materials, such as cast iron, which cannot be straightened, are supplied within .250" TIR.
GCQ5: What are your tolerances on machined tubing?
GCA5: Concerning straightness, concentricity, wall variation, ovality and parallelism, we can work to almost any limits you require.
GCQ6: What is "CERAM-SPUN"?
GCA6: "CERAM-SPUN" is a patented process that eliminates the expense of special or specific mold sizes. A ceramic slurry is introduced into a flask and centrifuged horizontally to form a thermally insulated mold of high-density, smooth face and inherent concentricity. We obtain "stepless" OD sizes of tubing by varying the weight of slurry, and thus the thickness of the mold, utilizing "stair step" flask sizes. The special advantages of "CERAM-SPUN" are (1) flexibility of OD size, (2) expansion of the molds during the casting process, which reinforces the casting during solidification, thus preventing hot tears and cracking, and (3) inherent concentricity of the tubing produced.
GCQ7: What are briefly summarized advantages of CERAM-SPUN tubing?
GCA7: (1) Reduced cost to the customer. (2) Flexibility in OD size, thickness and analysis. (3) Slow solidification rate, eliminating mid-wall imperfections. (4) Expansion of mold supports the casting during solidification, prevents cracking and hot tears. (5) The inherent concentricity of the mold face to the roller bands produces more uniform outside diameters, and results in lowering machining costs.
GCQ8: Describe American Centrifugal's fabrication process.
GCA8: We counter bore the ends of the tubes and slide them on to a machined back-up ring. We then weld the two pieces together and bore out the back-up ring, including the root pass of the weld, which results in a full penetration weld. There are some applications in which we do the same prep and weld but leave the back-up ring in place (based on whatever the customer requests).
GCQ9: Do you have standard size tubing?
GCA9: No, all tubing is custom made.
GCQ10: Why would you want to use centrifugals versus other type products?
GCA10: Price and schedule.
MACHINING
MQ1: Do you have machining capabilities?
MA1: Yes, boring 6" - 72", honing 6" - 66", turning 4" - 84", polishing 4" - 84", and horizontal bar 10' x 26' milling, drilling, tapping and boring.
MQ2: How large an ID can be honed at American?
MA2: American can hone up to 60" ID as long as the total weight of the item to be honed does not exceed 50,000 lbs.
MQ3: Will you provide your tubing in the as-cast condition for others to machine?
MA3: In most cases, American Centrifugal will supply the tube with no machining by American. We can provide the tubing in an as-cast condition or finished complete per a drawing. We have an expansive machine shop with over 90,000 square feet of space and over 75 machine tools.
MQ4: What surface finishes do you offer when rough machining is wanted?
MA4: Normally, we supply tubes rough machined on the OD with approximately 250 micro-inch and on the ID with approximately 500 micro-inch. If better finishes are needed or required, they can be supplied.
STANDARDS, PRACTICES, AND SPECIFICATIONS
SQ1: Can you quote a centrifugal if we give you the competitive wrought specification?
SA1: Yes, we can normally quote on your requirement if you give us the wrought specification. We do this by converting to an applicable comparable casting specification.
SQ2: Why do you ask so many questions regarding finish sizes and end use?
SA2: We ask so that we can be of better service to our customers. The answers we request help us to determine the most economical and suitable sizes for your application. These answers also determine how much stock should be allowed depending on how the material is to be used.
SQ3: What is the appearance of the as-cast OD surface of an American Centrifugal tube?
SA3: The as-cast OD has a "shot-blasted" appearance, or the appearance of a high-quality sand-casting surface.
SQ4: What is the appearance of the inside surface of an American Centrifugal tube?
SA4: Due to the method of manufacturing our tubing, the impurities are forced to the inside surface, leaving a considerably rougher finish than the outside surface. The inside as-cast surface can be removed by machining if this surface is too rough for the application intended.
SQ5: Why hasn't American installed vacuum degassing equipment?
SA5: We are not certain the benefits warrant the investment, since we know of no way to circumvent problems such as heat loss and gas pick-up after degassing, which are inherent in the centrifugal casting process.
QUALITY CONTROL
QCQ1: What quality control procedures are routinely used on steel tubes at American?
QCA1: Our tubes are produced from carefully selected, chemically analyzed furnace charges. The metal is carefully cleaned, electric furnace melted, and centrifugally cast under computer-controlled casting procedures, including control of spinning speeds and casting times. If applicable, the tubes are subsequently heat-treated under specifically approved procedures, and the metal is chemically and mechanically analyzed according to the applicable specifications. The tubes are shot blasted for best visual inspection and are Magna-flux checked where applicable.
QCQ2: What types of inspection does your tubing get?
QCA2: All of our tubing is 100% visually, chemically, and dimensionally inspected. If required by the sales order contract or in-house specifications, we are capable of various types of Non-Destructive Testing including magnetic particle, ultrasonic, zyglo, liquid penetrant, radiography, hydrostatic, pneumatic, hardness, magnetic permeability, dynamic and static balancing, profilometer, and borescopic.
QCQ3: What is the typical nondestructive test performed on splice welds?
QCA3: Magnetic particle and ultrasonic testing. Radiography of the splice weld can also be performed.
QCQ4: How thick of a section can radiograph?
QCA4: American can radiograph up to 5" thick.
QCQ5: Are you ISO certified?
QCA5: ISO certification is currently being implemented.
QCQ6: Can American Centrifugal furnish ASME Code Stamped Material?
QCA6: No; however, we can furnish material made to the ASME Code but we do not have a Code Stamp.
MARKETING METHODS
MQ1: Do you sell direct or through distributors?
MA1: We have one recognized distributor located in Ohio and everything else is primarily handled direct with the customer.
LITERATURE
LQ1: Do you have tables of standard sizes, thicknesses, weights and lengths?
LA1: No, we do not have standard sizes, thicknesses or lengths. The flexibility of our process allows us to produce any OD size within 4" to 55". Thicknesses and lengths may be varied to conform to specific requirements.
LQ2: Do you have publications showing metal strengths and specifications?
LA2: Some publications are available; however, American has not published standard mechanical property data. Generally, CERAM-SPUN tubing has mechanical properties different from a comparable wrought analysis; however, the difference in strength is a result of either cold or hot working and we do not have the disadvantages that are inherent in mechanically formed material. The mechanical properties of the cast material usually approximate the average of the longitudinal and transverse properties of the wrought material.
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