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Knowledge Vault

STORAGE & HANDLING

G.L. Huyett takes extreme care and caution in the procurement, production of, and shipment of raw materials and finished parts we manufacture.

Product handling is an important consideration in product quality. While not addressed in the ANSI standard, numerous references are made in the ASTM A108. From Section 9.3.1, “bars shall be given a surface coating of oil or other rust inhibitor to protect against corrosion during shipment.” And from 9.3.2, “The bars bundles shall be identified, packaged, and loaded to preserve the physical appearance [and] product tolerance…” In the notes in Table A1.4, “…straightness is a perishable quality and may be altered by mishandling. The preservation of straightness in cold-finished bars requires the utmost care in subsequent handling.”

At G.L. Huyett, significant efforts are made to insure proper handling, storage, and transportation of product. Most mill shipments are crated and shipped in wooden protective boxes with oil wrapped paper, as opposed to the open bundle method. Raw materials and finished products are nearly always shipped on flatbed trucks and unloaded using a crane and cradle system.

Lifting SteelThis system ensures that full bundles are lifted in two places to minimize bending, twisting, or contortion. The bundles are lifted directly from the truck bed to the cradle, so that forklift and other less reliable transportation means are avoided. Bundles are placed in rigid steel cradles that interface with the overhead crane. Each bundle is painted with proprietary grade colors so as to avoid misidentification from mill-specific and inconsistent coloring schemes. Bundels are tagged for lot and heat number control. When production commences, bars are transported from cradles to steel support tables to minimize distortion. Production ready bars are rolled to the band saws for operator ease and product protection.

During production, operators are trained and equipment is configured to control drop length to prevent the pinging of ends of keystock that might affect dimensions, tolerances, and performance in the field. Following production, parts are cleaned, a rust inhibitor is applied, and parts are dried. Finished parts are shipped in extra heavy-duty boxes with a liner. The box and liner provide extra shock and environmental protection.

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Raw Materials

Machine keys and pins are relatively simple components, but complicated to manufacture. The basic material used in manufacture is cold drawn steel. Cold drawn steel has a smooth finish, is relatively strong from the annealing and cold working process, and usually possesses dimensional tolerances that mate with conventional keyways.

There are two significant considerations in selecting raw material. The first is dimension. The second is grade. Raw material must conform to finish specifications for dimensions, flatness, parallelism, and surface finish. If the raw material does not conform to required specifications, additional processing may be required. In most cases, a larger size of material is required, which is then modified to finished tolerances. Grade mandates certain chemical composition and mechanical requirements. Most specifications mandate tolerances and not grade.

Note: Steels possessing carbon of greater than .28%, standard grades will have finish dimensions that do not conform to traditional specifications.

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Fastener Manufacturing Processes

G.L. Huyett is unique in the breadth of its manufacturing operations and has a reputation for producing hard-to-make parts on-site in our state-of-the-art manufacturing facility or through the use of an army of small machine shops and contract manufacturers around the world. Our operations and capabilities are complemented with a world-class warehouse containing over 95,000 non-threaded fasteners and industrial components.

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COLD DRAWING

Cold FinishCold drawing is a metalworking process that uses tensile force to stretch metal by pulling steel bars or sheets through a progressive set of rollers or dies at room temperature in order to modify their shape and structure. G.L. Huyett, in conjunction with domestic and international steel mills, has perfected a number of profiling techniques that are conducive to the manufacturing of high-quality keystock, machine keys, and other industrial fasteners.

Cold drawing profiles

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BAND SAWING

G.L. Huyett purchases cold finished bar stock from a variety of mills around the world. The bars are stored and accounted for by heat number and lot. Upon the receipt of an order, bars are pulled and welded into a pack to prevent the bars from sliding Band Saw back and forth as they are fed through a band saw using hydraulic jaws.

A band saw is a computer-controlled multipoint cutting machine designed to cut off bar stock, tubing, pipe, or other metal stock. The band saw functions by bringing a continuously moving, endless metal blade with teeth along one edge in contact with the workpiece to be cut. The blade travels continuously between a drive wheel and an idler wheel to produce a uniform cutting action. At least two teeth must be in contact with the workpiece at all times to avoid stripping of the teeth. The cutting blade runs vertically as it passes through material held firmly in place by hydraulic jaws on both sides of the blade to produce tight tolerance cutting accuracy. G.L. Huyett has pioneered the use of proprietary fixtures, material handling, and banding equipment to automate this process.

Band sawing profiles

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COLD SAWING

Cold SawingCompared to band saws, cold saws use a slow-moving angular blade that provides highly accurate finish-quality cuts, but in lower volume. Due to improved accuracy, cold sawing is typically used when fine length tolerances are desired since it produces minimal burrs, no discoloration to the metal, and minimal dust while cutting.

Cold sawing profiles

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MILLING

MillingSometimes our customers require special end designs or special dimensions on non-standard parts. In most cases, G.L. Huyett has established automated processes and fixtures that maximize throughput and efficiency.

Milling is a multipoint cutting process used to remove material from the face or periphery of a workpiece by a rotating cutting tool (also commonly referred to as a cutter or insert). The cutting tool rotates rapidly as the workpiece is moved relative to the cutting tool on a fixture. A fixture is a work holding devise designed specifically to hold one or more workpieces tightly in place in order to reduce the amount of time needed to position or lock workpieces to the machine table. Because of high pressures applied to the workpiece, there is risk of deformation and thus rigidity is important in machine and fixture design. With milling, the fixtures can enhance productivity as much as the milling machine itself. G.L. Huyett has developed a variety of proprietary state-of-the-art fixtures for milling shaft keys and profiles.

The travel path of the workpiece (via a worktable in the case of vertical milling – our primary production method), as well as the height of the spindle holding the rotating tool, is controlled numerically using Computer Numerically Controlled (CNC) technology. The rotating tool itself may be a solid piece or an insert – a lower cost method of high-speed milling where tool wear and tool life are major considerations. With inserts, small teeth are installed and reused on three or more different corners, as opposed to one large end mill.

Mill CutterTo increase operator throughput, pallets are deployed with changers on them. This pallet systems allow the operator to load and clamp unfinished pieces while the machine is in operation. The clamps themselves may deploy air or hydraulic systems so that operator time and fatigue are not consumed from manual clamping of the parts onto the pallet or table.

Milling is used to modify the tolerances (dimensions) of parts, to install steps or cutouts in a part, or to drill and tap holes. Parts can be deburred in the machine after an operation using a tool change. Milling can also be used to modify the ends, such as Form A radial ends on shaft keys. Any process that uses a rotating cutter can be used in our mills, and with a wide range of tooling, tool holders, and insert choices, the options are almost endless.

Mill - Unfinished PartsMilling is a violent and stressful process that is far more technical that it appears. The process requires rigidity in the fixtures as even slight movements can affect the finished results.

Milling creates heat and as cold finished material is removed on the outside of a part, stresses that were reintroduced into the steel during cold finishing can affect the part and cause it to warp and bend. Warpage can be problematic when milling to modify tolerances and dimensions. Not only can the straightness of the finished part be compromised, but the ability to perform other secondary operations can be impaired as well. These distortions can be countered in one of two manners: first, the material can be stress relieved prior to milling. If this method is used, the parts may require heat-treating after milling so as to return the material to proper hardness. The second method is to mill both sides of the part, and to control the amount of material removed on one side of a part, as a percentage of total thickness.

Generally, the maximum amount of material that can be removed on carbon steel parts is 0.125″. For greater tolerance modifications the part requires milling on both sides. Stainless steel is generally always milled on both sides, because of the presence of more stresses than carbon steel.

The minimum tolerance that can be held in tolerance modification using milling is 0.003″. Tighter tolerances can be realized using grinding as a secondary operation, but keep in mind that of these operations are both time consuming and expensive (and that parts must be magnetic to be ground). For more information on stress relieving, see “Heat Treatment.”

Milling profiles

Other Non-Milling Processes That Achieve Similar Results

Arbor Milling can be used to produce keyed shafts, keyways, or the steps on keyways. An arbor mill works the same as an end mill except that the cutting takes place on a surface that runs parallel to the axis of rotation.

Broaching is used to cut internal keyways into the inside diameter of a gear or sprocket; and to form the radius on a Form A shaft key. Broaching is a cutting operation where stock removal is built into the tool by having each successive tooth cut deeper into the material. The tools are long and tapered.

Shaping is used to form the ends of radial shaft keys. Material is removed by a single point cutting tool that reciprocates across the face of a stationary workpiece to produce a sculpted surface. For shaft keys, the parts are stood up in the fixture and shaped in batches in just a few passes.

Shearing is a high speed cutting process where an upper cutoff blade is passed by a lower blade, one of which is stationary, with a desired offset. It is an excellent production method for high-speed production of shaft keys, both with square (Form B) and radial (Form A) ends.

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TURNING

Turning is a machining operation performed on a lathe in which a workpiece rotates at high-speeds while a fixed cutting tool removes material. G.L. Huyett uses CNC, automatic bar feed equipment, and off-line programming to increase production and minimize setup time. Metal Turning and Lathe MachineThe most obvious use for a lathe is to manufacture pins. A lathe can turn complete parts including the formation of a head or radial grooves such as those found on a headless pin.

Some of our lathes are equipped with live tooling that consists of a second small spindle that is positioned perpendicular to the workpiece (in the same plain as the tool). Live Tooling is used to produce transverse features such as a cross hole in a pin.

Lathe Cross ToolLathes have a tailstock, which interferes with the end of the workpiece opposite the turret (which holds the chuck and spins the workpiece). The tailstock provides rigidity to the workpiece to minimize chatter and deformation when the part is being cut. Chatter is an undesirable attribute because it can interrupt the contact of the tooling with the workpiece. If the cutting tool does not maintain rigid and constant contact with the workpiece excessive chatter can bend or deform the workpiece.

Turning & Facing

Among the more basic processes of a lathe are turning and facing. Turning is a material-removal process where the tool is primarily parallel to the workpiece rotation. With facing, the tool is located at a right angle to the turret.

Parting & Grooving

Parting and grooving are other common lathe processes. Parting is a turning operation that uses a single-point cutoff tool to sever a section of a workpiece from raw stock. Grooving works similarly except the workpiece is not severed. There are many different groove styles that can be produced by using specialized tooling.

Boring

Lathes can be used to bore tapered or cylindrical holes by using a single-point cutting tool mounted to the tailstock that moves parallel to the axis of rotation. The Tailstock can also be equipped with drilling or reaming tools to create holes in the axis at one end of (or all the way through) a part. All drilling and reaming performed on G.L. Huyett lathes is done using a multi-station tool turret.

Turning profiles

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GRINDING

Metal Grinding processGrinding is a machining operation in which material is removed using a powered abrasive wheel, stone, belt, paste, sheet, compound, etc. to realize fine finish tolerances and surface finishes. While there are a number of ways to grind parts, surface grinding is the technique deployed at G. L. Huyett as it is a more precise method of tolerance modification. Surface grinding is an abrasive machining process in which abrasive particles, bonded onto a grinding wheel, remove small amounts of material from a workpiece.

Parts are laid on a table that has a chuck or holder. The holder uses the force of magnetism to hold parts on the table, or in the case of non-magnetic materials, like stainless steel, a vacuum chuck or adhesive is used. The magnetism of the chuck has limitations based on the size of the workpiece, as well as the holding power around the outer edges of the chuck (about 1″ in total).

The table reciprocates, or moves back and forth, beneath an abrasive turning wheel. As the table moves back and forth, the entire table moves in a way that over time, the grinding wheel passes over the entire surface area of the table. This process, while slow, is precise. With each pass, as much as 0.001″ of material is removed. The maximum thickness to be removed using this process is 0.008″. Otherwise, milling should be used.

In order to develop a constant datum point, a minimum amount of material is needed, which is .001″ for part lengths under 4″ in total. For parts over 4″ in length, a minimum removal of .003″ is required. Cold drawn steel has some permissible twist that is revealed in longer length parts. The extra stock allows the grinder to pass through the twists so that a common datum point is achieved.

Under the best of circumstances, a tolerance of 0.0005″ can be held using this method, although a maximum of +/-0.0005″ (0.001″ total) is recommended.

Grinding profiles

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PUNCHING/STAMPING

Punching, also referred to as stamping, is a process of using a punch press to punch through material and into a die to create a hole in a workpiece with expert precision. As the punch pushes through the material,Metal punching and stamping process it shears off and the sidewall of the resulting hole displays a burnished area, a rollover, and a breakout.

There are several variations of the basic punch design. For starters, more than one part can be punched in a single stroke for higher volume applications. A progressive set of dies can be used to form more complicated designs. In a progressive die, each stroke progresses toward a finished part. Deep drawn parts such as a cup are made this way.

There are also variations in tooling. Compound dies – which have more than one die component – are often used to make flat washers, where the formed part is basically the same, but there are different combinations of inside and outside diameter. One ID punch, can be used in combination with OD punches and thus overall tooling costs are less than if there is a one piece die for each set up.

Punching & Stamping profiles

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LASERING

Metal Laser Cutting ProcessLasering, or Laser cutting, is a metal forming process that uses intensified beams of light to drill or cut forms into metal to finished tolerances. Lasers use a high-energy beam supported by a coaxial supply of cutting gas to melt, vaporize, or combust material in a small and concentrated area. Lasering should be considered for production runs up to 500 pieces where tooling costs can be prohibitive. Lasered parts are flat, such as washers and other forms, but parts can be bent at angles following laser work. G.L. Huyett’s laser department is equipped to affordably run even “one-off” orders for prototypes and repairs.

Lasering profiles & capabilities

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cold heading

Cold heading, also known as cold forging, is a higher production format used to make pins and other solid parts. The cold heading process uses dies and a drive system to ram parts into a die cavity where they are upset, or enlarged, to the form of the die cavity. Forging may involve multiple strokes to progressively form a part, or to overcome the horsepower of a smaller cold heading machine. The multiple strokes can also be used to add numerous features to a single part in one overall production run.

Holes and certain transverse features (including threading on a bolt) are performed as a secondary operation. Cold heading is good for production runs over 1,000 pieces on large parts, and 5,000 pieces on smaller parts.

Cold heading profiles

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Tumbling

TumblerAfter sawing, parts are often tumbled to ensure that burrs are removed prior to shipment or plating. Tumbling consists of submitting the parts to vibration while in the presence of media, which in technical terms is known as vibratory finishing. The media is specially designed to cause friction with the parts, and in effect polish the parts in a controlled manner. There are established parameters governing the mixture of media and parts, and the amount of time the parts remain in the tumbler.

The tumbler is a large doughnut-shaped drum with parts that rotate in a circular direction. The entire load is lifted up (though not airborne), and then dropped. As the load is dropped, the tub returns to its upward position applying an angular upward force that serves as a shearing action. After a proper amount of production time, the tumblers empty into a conveyor belt and are sent through a cleaner and dryer. The cleaner and dryer contain rust inhibitor ingredients that extend the shelf life of plain finish parts. Shelf life can be adversely affected by environmental factors and improper handling and storage. Efforts must be made to avoid dropping parts long distances, where the edges can ping, or from handling the parts using bare hands, where oils and impurities present on your skin can damage the finish on the parts. For this reason, G.L. Huyett personnel use gloves when handling plain finish parts.

The tumbling process is performed after each production process that creates burrs, or after heat treating, where black scale resides on the parts and must be removed. In some instances up to .0005″ of material can be removed using especially aggressive vibratory media and an extended finishing time. Generally this is a cost effective means of altering tolerances and dimensions compared to machine removal such as with milling or grinding. Removal is uniform but not precise on all surfaces.

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wire forming

Wire forming can be done in a number of ways. Cotter pins are formed similar to cold heading, except that the dies are designed so that the wire is pushed around them and the wire forms around the die.

A fourslide is often used to form bridge pins and other complicated wire forms. The fourslide is wire fed and uses cams and a single motor that are timed to four dies that sit around the outside perimeter of a rotary table. The cams time the die impact into the wire, with the wire formed around the dies, similar to a cotter pin. Each machine stroke advances the part one more station forward progressively. After the fourth impact, the formed part is ejected through a hole in the middle of the rotary table. The opportunity for four impacts allows for rather complicated design capabilities. Fourslides can also design in-line, but are based on the same operating principles.

Metal Wire forming process

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Threading

There are two distinct methods used to thread a part: thread cutting is a process of using a single-point tool to produce a uniform helical thread form. Thread cutting involves removal of material and is used when full thread depth is required, the production quantity is small, the blank is not very accurate, threading up to a shoulder is required, or when the material is brittle. Thread cutting can be performed on a lathe.

Thread milling is related to thread cutting in that material is removed from the workpiece to create threads. Thread milling is generally used on larger threads (over 1.5 inches) and uses a multipoint tool. The advantages of thread milling versus thread cutting are a better surface finish, improved concentricity, and a left or right hand thread can be created with the same tool. Thread milling is normally done on a dedicated thread milling machine.

Thread rolling, also known as thread forming, is a cold-forming process in which external threads are formed by rolling workpieces between shaped hardened dies. The process is fast and is used for high production runs. The forming process itself increases the outside (major diameter) of the part and thus a smaller blank size can be used as opposed to the blanks used for cut threads. There is a typical 15-20% savings in blanks, measured by weight, in rolled versus cut thread parts. Rolled threads are recognized to the observer because the threads are larger than the blank rod from which they are formed. While cut and milled threads can be both internal and external, rolled threads are only external because of the forming process.

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HEAT TREATMENT

Hardenability is the property of steel that determines the depth and distribution of hardness induced by quenching from the austenitizing temperature. Hardenability should not be confused with hardness as such or with maximum hardness. Hardness is a measure of the ability of a metal to resist penetration as determined by any one of a number of standard tests (Brinell, Rockwell, Vickers, etc). The maximum attainable hardness of any steel depends solely on carbon content and is not significantly affected by alloy content. Maximum hardness is realized only when the cooling rate in quenching is rapid enough to ensure full transformation to martensite. The as-quenched surface hardness of a steel part is dependent on carbon content and cooling rate, but the depth to which a certain hardness level is maintained with given quenching conditions is a function of its hardenability. Hardenability is largely determined by the percentage of alloying elements in the steel; however, austenite grain size, time and temperature during austenitizing, and prior microstructure also significantly affect the hardness depth.

Steel’s versatility is due to its response to thermal treatment. Although most steel products are used in the as-rolled or un-heat-treated condition, thermal treatment greatly increases the number of properties that can be obtained, because at certain “critical temperatures” iron changes from one type of crystal structure to another. This structural change, known as an allotropic transformation, is spontaneous and reversible and can be made to occur by simply changing the temperature of the metal.

In steel, the transformation in crystal structure occurs over a range of temperatures, bounded by lower and upper critical points. When heated, most carbon and low–alloy steels have a critical temperature range between 1300 – 1600° F. Steel above this temperature, but below the melting range, has a crystalline structure known as austenite, in which the carbon and alloying elements are dissolved in a solid solution. Below this critical range, the crystal structure changes to a phase known as ferrite, which is capable of maintaining only a very small percentage of carbon in solid solution. The remaining carbon exists in the form of carbides, which are compounds of carbon and iron and certain of the other alloying elements. Depending primarily on cooling rate, the carbides may be present as thin plates alternating with the ferrite (pearlite); as spheroidal globular particles at ferrite grain boundaries or dispersed throughout the ferrite; or as a uniform distribution of extremely fine particles throughout a “ferrite-like” phase, which has an acicular (needlelike) appearance, named martensite. In some of the highly alloyed stainless steels the addition of certain elements stabilizes the austenite structure so that it persists even at very low temperatures (austenitic grades). Other alloying elements can prevent the formation of austenite entirely up to the melting point (ferritic grades).

Fundamentally, all steel heat treatments are intended to either harden or soften the metal. They involve one or a series of operations in which the solid metal is heated and cooled under specified conditions to develop a required structure and properties.

The choice of quenching media is often a critical factor in the selection of steel of the proper hardenability for a particular application. Quenching severity can be varied by selection of quenching medium, agitation control, and additives that improve the cooling capability of the quenchant. Increasing the quenching severity permits the use of less expensive steels of lower hardenability; however, consideration must also be given to the amount of distortion that can be tolerated and the susceptibility to quench cracking. In general, the more severe the quenchant and the less symmetrical the part being quenched, the greater are the size and shape changes that result from quenching and the greater is the risk of quench cracking. Consequently, although water quenching is less costly than oil quenching, and water quenching steels are less expensive than those requiring oil quenching, it is important to know that the parts being hardened can withstand the resulting distortion and the possibility of cracking.

Oil, salt, and synthetic water-polymer quenchants are also used, but they often require steels of higher alloy content and hardenability. A general rule for the selection of steel and quenchant for a particular part is that the steel should have a hardenability not exceeding that required by the severity of the quenchant selected. The carbon content of the steel should also not exceed that required to meet specified hardness and strength, because quench cracking susceptibility increases with carbon content. The choice of quenching media is important in hardening, but another factor is agitation of the quenching bath. The more rapidly the bath is agitated, the more rapidly heat is removed from the steel and the more effective is the quench. Listed below are some terms commonly associated with the quenching process:

Quenching (rapid cooling)

Direct Quenching: Quenching carburized parts directly from the carburizing operation.

Fog Quenching: Quenching in a mist.

Hot Quenching: An imprecise term used to cover a variety of quenching procedures in which a quenching medium is maintained at a prescribed temperature above 160° F (71° C).

Interrupted Quenching: A quenching procedure in which the workpiece is removed from the first quench at a temperature substantially higher than that of the quenchant and is then subjected to a second quenching system having a different cooling rate than the first.

Selective Quenching: Quenching only certain portions of a workpiece.

Slack Quenching: The incomplete hardening of steel due to quenching from the
austenitizing temperature at a rate slower than the critical cooling rate for the particular steel, resulting in the formation of one or more transformation products in addition to martensite.

Spray Quenching: Quenching in a spray of liquid.

Time Quenching: Interrupted quenching in which the duration of holding in the quenching medium is controlled.

Direct Hardening: Through hardening is applied to medium and high carbon parts that possess sufficient carbon content for hardening through the entire depth of the part. The parts are heated and quenched (cooled) to fix the structure of the part in a hardened state. The best recognized through hardened part in the world is a diamond!

Typical Heat Treatments for SAE Carbon Steels (Direct Hardening)

SAE No. Normalize,
Deg. F
Anneal,
Deg. F
Harden
Deg. F
Quench Temper
Deg.F
1025 & 1030 1575-1650 A To
Desired
Hardness
1033 to 1035 1525-1575 B
1036 1600-1700 1525-1575 B
1525-1575 B
1038 to 1040 1600-1700 1525-1575 B
1525-1575 B
1041 1600-1700 and/or 1400-1500 1475-1550 E
1042 to 1050 1600-1700 1475-1550 B
1052 & 1055 1550-1650 and/or 1400-1500 1475-1550 E
1060 to 1074 1550-1650 and/or 1400-1500 1475-1550 E
1078 1400-1500a 1450-1500 A
1080 to 1090 1550-1650 and/or 1400-1500a 1450-1500 Eb
1095 1400-1500a 1450-1500 F
1400-1500a 1500-1600 E
1132 & 1137 1600-1700 and/or 1400-1500 1525-1575 B
1138 & 1140 1500-1550 B
1600-1700 1500-1550 B
1141 & 1144 1400-1500 1475-1550 E
1600-1700 1400-1500 1475-1550 E
1145 to 1151 1475-1550 B
1600-1700 1475-1550   B
  1. Slow cooling produces a spheroidal structure in these high-carbon steels that is sometimes required for machining purposes.
  2. May be water- or brine-quenched by special techniques such as partial immersion or time quenched; otherwise they are subject to quench cracking.
 

Indirect Hardening: Case hardening (or indirect hardening) is applied to low-carbon content steel parts to increase surface hardness. During case hardening, carbon molecules are introduced to the part via solids, liquids, or gases in a process known as carburizing. The molecules penetrate the surface of the part, forming a casement, which is identified by the case depth (Y) and surface hardness (X). More exacting specifications will identify an effective case “Z” or a specific hardness requirement at a particular depth. Case hardness cannot be measured effectively using a Rockwell test. Readings must be taken from a cross section of the part using a microhardness tester.

Indirect hardening

Listed below are some terms and processes typically associated with case hardening (also known as indirect hardening):

Carburizing: A process in which carbon is introduced into a solid iron-base alloy by heating above the transformation temperature range while in contact with a carbonaceous material that may be a solid, liquid, or gas. Carburizing is frequently followed by quenching to produce a hardened case.

Case: 1) The surface layer of an iron-base alloy that has been suitably altered in composition and can be made substantially harder than the interior or core by a process of case hardening; and 2) the term case is also used to designate the hardened surface layer of a piece of steel that is large enough to have a distinctly softer core or center.

Typical Heat Treatments for SAE Carbon Steels (Indirect hardening)

SAE Normalize,
Deg. F
Carburize,
Deg. F
Coola Reheat
Deg. F
Coola 2nd Reheat
Deg. F
Coola Temperb
Deg. F
1010 to 1022 1650-1700 A 250-400
1650-1700 B 1400-1450 A 250-400
1650-1700 C 1400-1450 A 250-400
1650-1700 C 1650-1700 B 1400-1450 A 250-400
1500-1650cd B Optional
1650-1750f 1350-1575ed D Optional
1024 1650-1700 E 250-400
1025
1026
1350-1575ed D Optional
1650-1700 A 250-400
1027 1500-1650cd B Optional
1030 1350-1575ed D Optional
1500-1650cd B Optional
1350-1575ed D Optional
1111
1112
1113
1500-1650cd B Optional
1350-1575ed D Optional
1650-1700 A 250-400
1109 to 1120 1650-1700 B 1400-1450 A 250-400
1650-1700 C 1400-1450 A 250-400
1650-1700 C 1650-1700 B 1400-1450 A 250-400
1500-1650cd B Optional
1350-1575ed D Optional
1126 1500-1650cd B Optional
1350-1575ed D Optional
  1. Symbols: A = water or brine; B = water or oil; C = cool slowly; D = air or oil; E = oil; F = water, brine, or oil.
  2. Even where tempering temperatures are shown, tempering is not mandatory in many applications. Tempering is usually employed for partial stress relief and improves resistance to grinding cracks.
  3. Activated or cyanide baths.
  4. May be given refining heat as in other processes.
  5. Carbonitriding atmospheres
  6. Normalizing temperatures at least 50° F above the carburizing temperature are sometimes recommended where minimum heat-treatment distortion is of vital importance.
 

THERMAL MODIFICATION OF STEEL

Listed below are terms and processes associated with the thermal modification of steel for compatibility with manufacturing. Manufacturing of steel frequently causes friction, which introduces heat to the material. Thermal modification of steel diminishes the potential for adverse consequences, such as deformation caused by heating.

Stress Relieving: A process to reduce internal residual stresses in a metal object by heating the object to a suitable temperature and holding for a proper time at that temperature. This treatment may be applied to relieve stresses induced by casting, quenching, normalizing, machining, cold working, or welding.

Tempering: Heating a quench-hardened or normalized ferrous alloy to a temperature below the transformation range to produce desired changes in properties.

Annealing: Heating steel to and holding at a suitable temperature followed by cooling at a suitable rate, used primarily to soften but also to simultaneously produce desired changes in other properties or in microstructure. The purpose of the changes may be, but is not confined to, improvement of machinability; facilitation of cold working; improvement of mechanical or electrical properties; or increase in stability of dimensions. The time–temperature cycles used vary widely both in maximum temperature attained and in cooling rate employed, depending on the composition of the material, its condition, and the results desired.

Baking: Heating to a low temperature in order to remove entrained gases.

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