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Friday, September 23, 2016

Copper base alloys and use



Copper-Base Alloys

Cast copper alloys are known for their versatility. They are used in a wide range of applications, such as plumbing fixtures, ship propellers, power plant water impellers and bushing and bearing sleeves, because they are easily cast, have a long history of successful use, are readily available from a multitude of sources, can achieve a range of physical and mechanical properties and are easily machined, brazed, soldered, polished or plated.
Following is a list of physical and mechanical properties common to cast copper alloys. Although not every property is applicable to every alloy, this range, which occurs in unique combinations, isn’t found in any other alloy group:
  • good corrosion resistance, which contributes to its durability and long-term cost-effectiveness;
  • favorable mechanical properties ranging from pure copper, which is soft and ductile, to manganese-bronze, which rivals the mechanical properties of quenched and tempered steel. In addition, almost all copper alloys retain their mechanical properties, including impact toughness, at low temperatures;
  • high thermal and electrical conductivity, which is greater than any metal except silver. Although the conductivity of copper drops when alloyed, copper alloys with low conductivity still conduct both heat and electricity better than other corrosion-resistant materials;
  • bio-fouling resistance, as copper inhibits marine organism growth. Although this property (unique to copper) decreases upon alloying, it is retained at a useful level in many alloys, such as copper-nickel;
  • low friction and wear rates, such as with the high-leaded tin-bronzes, which are cast into sleeve bearings and exhibit lower wear rates than steel;
  • good castability, as all copper alloys can be sand cast and many can be centrifugal, continuous, permanent mold and diecast;
  • good machinability, as leaded copper alloys are free-cutting at high machining speeds, and many unleaded alloys, such as nickel-aluminum bronze, are readily machinable at recommended feeds and speeds with proper tooling; 
  • ease of post-casting processing, as good surface finish and high tolerance control is readily achieved. In addition, many cast copper alloys are polished to a high luster, and plating, soldering, brazing and welding also are routinely performed;
  • large alloy choice, since several alloys may be suitable candidates for any given application depending upon design loads and corrosivity of the environment;
  • comparable costs to other metals due to their high yield, low machining costs and little requirement for surface coatings, such as paint. 
Using Copper Alloys
Cast copper alloys are identified by the Unified Numbering System (UNS) in which each alloy is assigned a number ranging from C80000 to C99999. From a metallurgical viewpoint, many cast copper alloys are single-phase solid solutions in which the alloying elements such as zinc, tin and nickel are substituted for copper in the copper matrix. Examples of cast single-phase solution alloys are red brass, which contains up to 6% zinc and 2% tin, copper-nickel, which contains up to 10% nickel, and tin-bronze, which contains up to 8% tin and 4% zinc.
As the alloy content increases, a second phase may form. In the case of brass, when the zinc content is increased, a hard second phase (called beta) forms with the copper-rich matrix. This phase is found in yellow brass, which contains up to 41% zinc. In addition, this phase impairs room temperature ductility but increases elevated temperature ductility.
Role of Lead
Lead is commonly added to many cast copper alloys. Because of the low solubility of lead in copper, true alloying does not occur to any measurable degree. During the solidification of castings, some constituents in a given alloy form crystals at higher temperatures relative to others, resulting in tree-like structures called dendrites. The small spaces between the dendrites can interconnect to form micropores. This micro­porosity is a consequence of the solidification process. The role of lead is to seal these intradendritic pores. This results in a pressure-tight casting, which is important for fluid handling applications.
Lead also allows the machining of castings to be performed at higher speeds without the aid of coolants because it acts as a lubricant for cutting tool edges and promotes the formation of small, discontinuous chips that can be cleared easily. This results in improved machined surface finishes. Lead also plays a role in providing lubricity during service, as in cast copper bearings and bushings. Lead does not have an adverse effect on strength unless present in high concentrations, but it does reduce ductility. Although lead-containing copper alloys can be soldered and brazed, they cannot be welded.
Following is a list of the various cast copper alloy families.
Coppers
Coppers (C80100 to 81200)—These alloys are pure copper (99.7% minimum) with traces of silver (for annealing resistance) or phosphorus (a de-oxidizer for welding). These alloys are used in high thermal and electrical conductivity applications, such as electrical connectors.
High Coppers (C81400 to C82800)—High copper alloys (more than 95.1% copper) are unique in that they combine high strength with high thermal and electrical conductivity.
Chromium-Copper (C81400 to 81540)—Containing up to 1.5% chromium, the strength of these alloys is twice that of pure copper, but its electrical conductivity is 80% of pure copper. Applications include welding clamps and high-strength electrical connectors.
Copper-Beryllium (C82000 to C82800)—These alloys contain 0.35-2.85% beryllium as the major alloying element and are age- or precipitation-hardened. They achieve high strength due to the precipitation of a fine second phase during heat treatment. Copper beryllium alloys either achieve high conductivity at moderate strength or moderate conductivity at high strength.
Brasses
The brasses (C83300 to C85800 and C89320 to C89940) are the most common casting alloys and are made of copper and zinc.
Red Brass (C83300 to 83810)—The red brasses are alloys of zinc (1-12%) and tin (0.2-6.5%) and may contain lead (0.5-7%). In red brass, lead is present to promote pressure tightness in service and to facilitate free machining during manufacturing. The red color is due to low zinc content. The highest volume red brass alloy (C83600) has been used commercially for hundreds of years and accounts for more tonnage than any other alloy.
Semi-Red Brass (C84200 to C84800)—Semi-red brass has higher zinc content than the red brasses, which reduces corrosion resistance, lowers raw material costs and lightens the color (but has little effect on strength). Because of their outstanding aqueous corrosion resistance, red brass and semi-red brass often are used in plumbing fittings, such as unions, valves and water meters.
Yellow Brass (C85200 to C85800)—The yellow brasses are lower in cost than the red brasses because their zinc content is higher (20-41%). In addition, they have good castability, with some alloys being permanent mold cast or diecast. Yellow brass has a pleasant yellow color that can be polished to a high luster.
Copper-Bismuth and SeBiLOYS (C89320 to C89940)—The copper-bismuth and selenium-bismuth (SeBiLOY) alloys are low-lead brass alloys that are used in food process and potable water applications. The three SeBiLOY alloys were developed to minimize lead leaching into potable water and to replicate the high machinability and pressure tightness of leaded brass. This is realized by substituting selenium and bismuth for lead. SeBiLoy I and II are red brasses and SeBiLOY III is a yellow brass.
Bronzes
Bronze is an imprecise term. It originally referred to alloys in which tin was the major alloying element. Under the UNS system, the term bronze (C86100 to 87800, C90200 to C95900) applies to a broad class of alloys in which the principal alloying element is neither zinc nor nickel. Nevertheless, bronze is the common name for a number of alloys that contain little, if any, tin.
Manganese-Bronze (C86100 to C86800)—Manganese-bronze, which contains zinc (22-42%) as the major alloying element, is among the strongest cast copper alloys and is used for gears, bolts and valve stems. Where economically feasible, aluminum-bronze replaces manganese-bronze because it offers high strength in combination with better corrosion resistance.
Silicon-Bronze and Silicon-Brass (C87300 to C87800)—Silicon-bronze and silicon-brass are alloys of zinc and silicon that have low melting points and high fluidity, which favor permanent mold and diecasting. Because of its low lead content, silicon-bronze often is a replacement for leaded plumbing brasses, but its limited machinability inhibits use in high-volume potable water systems. It is currently being used as a substitute for semi-red brass in immersed pumps.
Tin-Bronze (C90200 to C91700)—Tin-bronze is an alloy of copper and tin with good aqueous corrosion-resistance. Additional attributes include high strength, good wear resistance and a low friction coefficient compared to steel. This accounts for its use in bearings, piston rings and gear parts.
Leaded Tin-Bronze (C92200 to C92900)—These alloys are a tin-bronze containing 0.3-6% lead. Leaded tin-bronze offers the additional advantage of free cutting.
High-Leaded Tin Bronze (C93100 to C94500)—This is a tin-bronze containing 2-34% lead. High-leaded tin-bronze is used in sleeve bearings and bushings because the additional lead provides improved lubricity.
Nickel-Tin-Bronze (C94700 to C94900)—This is a tin-bronze containing 4-6% nickel. Nickel-tin-bronze is a versatile alloy that has the good wear resistance and corrosion resistance found in tin-bronzes with improved strength. Nickel-tin-bronze is used in many applications including bearings, gears, wear guides, and pump and valve components, and in motion and translation devices, such as shift forks and circuit breaker parts.
Aluminum-Bronze (C95200 to C95900)—Aluminum-bronze has a complex metallurgical structure that imparts both strength and oxidization resistance due to the formation of alumina-rich protective films. These alloys are wear-resistant and exhibit good casting and welding characteristics. Their corrosion resistance is superior in seawater, chloride and dilute acids. Applications are varied and include propellers and valves, pickling hooks, pickling baskets and wear rings. The aluminum bronze alloys that contain nickel are desirable for fluid-moving applications, such as pump impellers, because of superior erosion, corrosion and cavitation resistance.
Other Alloys
Copper-Nickel (C96200 to 96950)—These alloys are simple solid solutions of nickel in copper without lead. The copper-nickel alloys have excellent corrosion resistance in seawater, high strength and ease of manufacturing. Their various applications include pumps, valves, ship tail shaft sleeves and other marine applications.
Nickel-Silver (C97300 to C97800)—The presence of nickel accounts for these alloys’ silver luster. These alloys, which do not contain silver, offer good corrosion resistance, ease of castability and good machinability. Despite their high degree of alloying, these alloys are simple solid solutions. Major uses include hardware for food processing, seals, architectural trim and musical instrument valves.
Leaded-Coppers (C98200 to C98840)—These are essentially pure copper or high-copper alloys containing lead. The leaded-coppers offer the moderate corrosion resistance and high conductivity of the copper alloys, in addition to the lubricity and low friction characteristics of high-leaded bronzes.
Special Alloys (C99300 to C99750)—These are alloys with unique characteristics, such as Incrament 800 (C99300), which has high oxidation resistance due to aluminum, good thermal fatigue resistance and high hot hardness. This alloy was developed for glass processing including glassmaking molds and plate glass rolls.
Design for Manufacturing
The choice of alloy and casting method (sand, permanent mold, die or investment casting) determines the mechanical and physical properties, section size, wall thickness and surface finish that can be achieved. Each alloy and casting process combination results in a different set of properties.
If metalcasting facility and design engineers can work together on the “raw” or ideal component, all options will be considered early in the design process, resulting in a design and component that take advantage of the versatility that copper alloys offer.

from : www.afsinc.org/content.cfm?ItemNumber=7810

Aluminum Alloys grade



Wrought alloys
The International Alloy Designation System is the most widely accepted naming scheme for wrought alloys. Each alloy is given a four-digit number, where the first digit indicates the major alloying elements, the second — if different from 0 — indicates a variation of the alloy, and the third and fourth digits identify the specific alloy in the series. For example, in alloy 3105, the number 3 indicates the alloy is in the manganese series, 1 indicates the first modification of alloy 3005, and finally 05 identifies it in the 3000 series.
  • 1000 series are essentially pure aluminium with a minimum 99% aluminium content by weight and can be work hardened.
  • 2000 series are alloyed with copper, can be precipitation hardened to strengths comparable to steel. Formerly referred to as duralumin, they were once the most common aerospace alloys, but were susceptible to stress corrosion cracking and are increasingly replaced by 7000 series in new designs.
  • 3000 series are alloyed with manganese, and can be work hardened.
  • 4000 series are alloyed with silicon. They are also known as silumin.
  • 5000 series are alloyed with magnesium.
  • 6000 series are alloyed with magnesium and silicon. They are easy to machine, are weldable, and can be precipitation hardened, but not to the high strengths that 2000 and 7000 can reach. 6061 alloy is one of the most commonly used general-purpose aluminium alloys.
  • 7000 series are alloyed with zinc, and can be precipitation hardened to the highest strengths of any aluminium alloy (tensile strength up to 700 MPa for the 7068 alloy).
  • 8000 series are alloyed with other elements which are not covered by other series. Aluminium-lithium alloys are an example

List of aerospace aluminium alloys

The following aluminium alloys are commonly used in aircraft and other aerospace structures:
Note that the term aircraft aluminium or aerospace aluminium usually refers to 7075.
6063 aluminium alloys are heat treatable with moderately high strength, excellent corrosion resistance and good extrudability. They are regularly used as architectural and structural members.
The following list of aluminium alloys are currently produce, but less widely used:

Marine alloys

These alloys are used for boat building and shipbuilding, and other marine and salt-water sensitive shore applications.
4043, 5183, 6005A, 6082 also used in marine constructions and off shore applications.

Cycling alloys

These alloys are used for cycling frames and components

Automotive alloys

6111 aluminium and 2008 aluminium alloy are extensively used for external automotive body panels, with 5083 and 5754 used for inner body panels. Hoods have been manufactured from 2036, 6016, and 6111 alloys. Truck and trailer body panels have used 5456 aluminum.
Automobile frames often use 5182 aluminium or 5754 aluminium formed sheets, 6061 or 6063 extrusions.
Wheels have been cast from A356.0 aluminium or formed 5xxx sheet.

Air and gas cylinders

6061 aluminum and 6351 aluminium are widely used in breathing gas cylinders for scuba diving and SCBA

Wednesday, September 21, 2016

Stainless Steel Grade, Type and Properties

Type of stainless Steel

1            Austenitic grade

2            Martensitic grade

3            Ferritic grade

4            Duplex Grade

5            Precipitation Hardening Grades

6            Super Alloy Grade

 

1. Austenitic Grades

       Austenitic grades are those alloys which are commonly in use for stainless applications.

       The austenitic grades are not magnetic.

       The most common austenitic alloys are iron-chromium-nickel steels and are widely known as the 300 series.

       The austenitic stainless steels, because of their high chromium and nickel content, are the most corrosion resistant of the stainless group providing unusually fine mechanical properties.

       They cannot be hardened by heat treatment, but can be hardened significantly by cold-working.

 


       Straight Grades

   The straight grades of austenitic stainless steel contain a maximum of .08% carbon.

       Low Carbon Grades

   The “L” grades are used to provide extra corrosion resistance after welding.

   The carbon is kept to .03% or under to avoid carbide precipitation

   The letter “L” after a stainless steel type indicates low carbon (as in 304L)

   "L" grades are more expensive


       High Carbon Grades

   The “H” grades contain a minimum of .04% carbon and a maximum of .10% carbon and are designated by the letter “H” after the alloy.

   People ask for “H” grades primarily when the material will be used at extreme temperatures as the higher carbon helps the material retain strength at extreme temperatures.

 
Austenitic Grades and Type

       Type 304

   The most common of austenitic grades, containing approximately 18% chromium and 8% nickel. It is used for chemical processing equipment, for food, dairy, and beverage industries, for heat exchangers, and for the milder chemicals.

       Type 316

   Contains 16% to 18% chromium and 11% to 14% nickel

   Type 316 is used in chemical processing, the pulp and paper industry, for food and beverage processing and dispensing and in the more corrosive environments. The molybdenum must be a minimum of 2%

       Type 317

   Contains a higher percentage of molybdenum than 316 for highly corrosive environments. It must have a minimum of 3% “moly”

       Type 321 & Type 347

   developed for corrosive resistance for repeated intermittent exposure to temperature above 800 degrees F. Type 321 is made by the addition of titanium and Type 347 is made by the addition of tantalum/columbium. These grades are primarily used in the aircraft industry

 
Martensitic Grades

       developed in order to provide a group of stainless alloys that would be corrosion resistant and hardenable by heat treating.

       The martensitic grades are straight chromium steels containing no nickel.

       They are magnetic and can be hardened by heat treating.

       The martensitic grades are mainly used where hardness, strength, and wear resistance are required

Martensitic Grades Type

       Type 410

   Basic martensitic grade, containing the lowest alloy content of the three basic stainless steels (304, 430, and 410).

   Low cost, general purpose, heat treatable stainless steel.

   Used widely where corrosion is not severe (air, water, some chemicals, and food acids.

   Typical applications include highly stressed parts needing the combination of strength and corrosion resistance such as fasteners

       Type 410S

   Contains lower carbon than Type 410, offers improved weldability but lower hardenability.

   Type 410S is a general purpose corrosion and heat resisting chromium steel recommended for corrosion resisting application

       Type 414

   Has nickel added (2%) for improved corrosion resistance.

   Typical applications include springs and cutlery

2. Martensitic Grades

       Type 416

   Contains added phosphorus and sulphur for improved machinability. Typical applications include screw machine parts

       Type 420

   Contains increased carbon to improve mechanical properties. Typical applications include surgical instruments

       Type 431

   Contains increased chromium for greater corrosion resistance and good mechanical properties. Typical applications include high strength parts such as valves and pumps

       Type 440

   Further increases chromium and carbon to improve toughness and corrosion resistance

 
Ferritic Grades

       developed to provide a group of stainless steel to resist corrosion and oxidation, while being highly resistant to stress corrosion cracking.

       These steels are magnetic but cannot be hardened or strengthened by heat treatment.

       They can be cold worked and softened by annealing.

       As a group, they are more corrosive resistant than the martensitic grades, but generally inferior to the austenitic grades.

       Like martensitic grades, these are straight chromium steels with no nickel.

       They are used for decorative trim, sinks, and automotive applications, particularly exhaust systems

 

Ferritic Grades Type

       Type 430

   The basic ferritic grade, with a little less corrosion resistance than Type 304. This type combines high resistance to such corrosives as nitric acid, sulfur gases, and many organic and food acids

       Type 405

   Has lower chromium and added aluminum to prevent hardening when cooled from high temperatures. Typical applications include heat exchangers

       Type 409

   Contains the lowest chromium content of all stainless steels and is also the least expensive. Originally designed for muffler stock and also used for exterior parts in non-critical corrosive environments

 


       Type 434

   Has molybdenum added for improved corrosion resistance. Typical applications include automotive trim and fasteners.

       Type 436

   Type 436 has columbium added for corrosion and heat resistance. Typical applications include deep-drawn parts

       Type 442

   Has increased chromium to improve scaling resistance. Typical applications include furnace and heater parts

       Type 446

   Contains even more chromium added to further improve corrosion and scaling resistance at high temperatures. Especially good for oxidation resistance in sulfuric atmospheres

4. Duplex Grades

       Duplex grades are the newest of the stainless steels.

       This material is a combination of austenitic and ferritic material. T

       his material has higher strength and superior resistance to stress corrosion cracking.

       An example of this material is type 2205.

       It is available on order from the mills

5. Precipitation Hardening Grades

       Precipitation hardening grades, as a class, offer the designer a unique combination of fabricability, strength, ease of heat treatment, and corrosion resistance not found in any other class of material.

       These grades include 17Cr-4Ni (17-4PH) and 15Cr-5Ni (15-5PH)

 

6. Super Alloy Grades

       Superalloys are used when 316 or 317 are inadequate to withstand attack.

       They contain very large amounts of nickel and/or chrome and molybdenum.

       They are usually much more expensive than the usual 300 series alloys and can be more difficult to find.

       These alloys include Alloy 20 and Hastelloy