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Detailed table of contents
First section: Furnaces and Baths for Heating Steel
Previous section: Casehardening
Next section: Testing the Hardness of Metals
When referring to the tables, "Physical Properties of Heat-treated Carbon Steels" and "Physical Properties of Heat-treated Alloy Steels," the following points should be considered: (1) The figures given indicate what can be expected as the average product of a given composition when treated in the manner specified, and as applied to average sections prevailing in automobile work; (2) the values given are low enough so as to protect the makers of heat-treated stock and parts from unreasonable demands, the idea being to give values which coincide with the results obtained when stock of medium to high grade is purchased in the open market and treated by means of commercially efficient equipment controlled by commercially accurate instruments. For the sake of simplicity it was deemed advisable to adopt only average minimum values for tensile strength, elastic limit, reduction of area and elongation. These values are based upon the following considerations, the heat treatment being kept constant: The lowest tensile strength and elastic limit occur with steels at the bottom of a given range in carbon. The lowest reductions in area and elongations occur with steels at the top of a given range in carbon. True elastic limits are given, because these are constantly lower than corresponding yield points. The yield point is measured by the drop of the testing machine beam, and while this is the most readily and widely used measure of the so-called elastic limit, the results obtained by this method are generally 5000 to 15,000 pounds higher than the true elastic limit when the latter property is not in excess of 125,000 pounds per square inch. The values given are very conservative and average results in practice will generally exceed appreciably the figures given, which serves to increase the factor of safety and protect both the engineer and the manufacturer.
S. A. E. Specification Numbers for Steels. -- A numeral index system has been adopted by the Society of Automotive Engineers, Inc. for representing the different classes of steel included in the S. A. E. specifications. This system makes it possible to employ specification numerals on shop drawings and blueprints that are partially descriptive of the steel to which the numbers apply. The first figure of the number indicates the general class to which the steel belongs: thus, 1, indicates carbon steel; 2, nickel steel; 3, nickel-chromium steel; 5, chromium steel; 6, chromium-vanadium steel; 7, tungsten steel; 9, silico-manganese steel. In the case of alloy steels, the second figure generally indicates the approximate percentage of the chief alloying element. The last two or three figures indicate the average carbon content in "points" or hundredths of one per cent. For example, specification No. 2512 indicates a nickel steel with approximately 5 per cent nickel, and 0.12 per cent carbon; and specification No. 71660 indicates a tungsten steel with about 16 per cent tungsten and 0.60 per cent carbon.
Ten Per Cent Carbon Steel (Specification No. 1010). -- This steel is usually known in the trade as soft, basic open-hearth steel. It is commonly used for seamless tubing, pressed steel frames, pressed steel brake drums, sheet steel brake bands, and a variety of other pressed steel parts. In a natural or annealed condition this steel has little tenacity, and should not be used where much strength is required. The quality is considerably improved by cold-drawing or cold-rolling, the yield point being raised by such mechanical working. When this steel, after such cold working, is heated as for bending, pressing, welding, etc., the yield point returns to that corresponding with the annealed steel. This is also true of all materials that are given a higher yield point by cold working. This steel has the following physical characteristics:
Annealed Cold-drawn Yield point, pounds per square inch . . .28,000 to 36,000 40,000 to 60,000 Reduction of area, per cent . . . . . . . . . 65-55 55-45 Elongation in 2 inches, per cent . . . . . . 40-30 unimportant
|Carbon, Per Cent||Manganese, Per Cent||Maximum Percentage||S. A. E. Specification Number|
|Desired||Min. and Max.||Desired||Min. and Max.||Phosphorus||Sulphur|
|Carbon, Per Cent||Manganese, Per Cent||Nickel, Per Cent||Chromium, Per Cent||S. A. E. Specification Number|
|Desired||Min. and Max.||Desired||Min. and Max.||Desired||Min. and Max.||Desired||Min. and Max.|
|Carbon, Per Cent||Manganese, Per Cent||Chromium, Per Cent||Vanadium, Per Cent||S. A. E. Specification Number|
|Desired||Min. and Max.||Desired||Min. and Max.||Desired||Min. and Max.||Desired||Min.|
Twenty Per Cent Carbon Steel (Specification No. 1020). -- This steel is known to the trade as 0.20 per cent carbon open-hearth steel and often as machine steel. It is intended primarily for casehardening, forges well, machines well, but should not be considered as screw machine stock. This steel may e used for a large variety of forged, machined, and casehardened automobile parts where strength is not paramount. Steel of this quality may also be drawn into tubes and rolled into cold-rolled forms, and it is better for frames than the 0.10 per cent carbon steel as it is stronger. For automobile parts this steel may be used interchangeably with the 0.10 per cent carbon steel as far as cold-processed shapes are concerned, and it is only the most difficult cold-forming operations that will cause trouble from cracking.
The physical properties of this steel after heat treatment, and of others of higher carbon content, are given in the table, "Physical Properties of Heat-treated Carbon Steels." These values apply to 1/2 to 1-1/2 inch round specimens which were heated from 15 to 30 minutes to the temperatures given in the table, quenched in oil, re-heated for 30 minutes and finally cooled in air. The physical properties given in the table referred to apply to three re-heating temperatures.
Heat Treatment. -- Heat treatment of the 0.20 per cent carbon steel produces but little change so far as strength is concerned, but it does cause a desirable refinement of the grain after forging, and materially increases the toughness. The machining qualities can often be improved by heat treatment H. Casehardening is the most important heat treatment for this quality of steel. The heat treatment depends upon the importance of the part and upon its shape and size. When parts are not intended to carry much load or withstand any shock, and the principal requirement is hardness, the simplest form of casehardening as obtained by heat treatment A will suffice. Screws and rod-end pins are examples of this class of work. For more important parts, such as gears, steering wheel pivot pins, cam rollers, push rods, and many similar automotive parts, which must not only be hard on the surface but possess strength, the desired treatment is one which first refines and strengthens the interior and uncarbonized metal. This is then followed by a treatment for refining the exterior or carbonized metal. Heat treatment B is employed. In the case of very important parts, the last drawing operation should be continued from one to three hours. The object of drawing is to relieve all internal strains produced by quenching, and decrease the hardness. The last drawing operation can be omitted with a large number of pieces. This steel when cold-rolled or cold-drawn will have a yield point of from 40,000 to 75,000 pounds per square inch for sections not over 1/2 inch round, or 1/4 inch thick in the case of sheets or flat stock.
Hardness. -- The various degrees of hardness of the 0.20 per cent carbon steel conforming to the different heat treatments listed in the table "Physical Properties of Heat-treated Carbon Steels" are as follows: For a re-heating temperature of 400 degrees F., 180 Brinell and 34 scleroscope; for a re-heating temperature of 900 degrees F., 140 Brinell and 32 scleroscope; for a re-heating temperature of 1400 degrees F., 100 Brinell and 30 scleroscope.
|Carbon, Per Cent||Manganese, Max. Per Cent||Phosphorus, Max. Per Cent||Sulphur, Max. Per Cent||Chromium, Per Cent||Tungsten, Per Cent||S. A. E. Specification Number|
|Desired||Min. and Max.|
|Carbon, Per Cent||Manganese, Per Cent||Silicon, Per Cent||Phosphorus and Sulphur, Max.||S. A. E. Specification Number|
|Desired||Min. and Max.||Desired||Min. and Max.||Desired||Min. and Max.|
Twenty-five Per Cent Carbon Steel (Specification No. 1025). -- This steel is used extensively for frames and for ordinary drop-forgings where moderate ductility is desired but great strength is not essential. It is not intended for case-hardening, although by careful manipulation it may be so treated. This should be done in emergencies only, rather than as regular practice, always employing the double heat treatment followed by a drawing operation.
Heat treatment. -- Heat treatment has a moderate effect on the physical properties of the 0.25 per cent carbon steel, but this effect is not nearly so marked as in the case of the 0.35 per cent carbon steel. Heat treatment H or D may be employed, the former being simpler. The drawing operation must be varied to suit each individual case. For instance, if great toughness and little increase in strength are desired, the higher drawing temperatures (1100 degrees or 1200 degrees F.) may be used; whereas, if considerable strength is desired and a little toughness, the lower temperatures are used. With some parts the drawing operation can be omitted entirely. The double heat treatment D gives better results than heat treatment H, a better refinement of grain being obtained.
Hardness. -- The various degrees of hardness conforming to the heat treatments listed in the table "Physical Properties of Heat-treated Carbon Steels" are as follows: For a re-heating temperature of 400 degrees F., 215 Brinell and 37 scleroscope; for a re-heating temperature of 900 degrees F., 160 Brinell and 34 scleroscope; for a re-heating temperature of 1400 degrees F., 110 Brinell and 30 scleroscope.
Thirty-five Per Cent Carbon Steel (Specification No. 1035). -- This steel is sometimes referred to in the trade as 0.35 per cent carbon machine steel. It is intended primarily for use as structural steel. It forges well, machines well, and responds to heat treatment as regards strength and toughness. It can be used for all forgings such as axles, driving shafts, steering pivots, and other structural parts. It is the best all-around structural steel for such use as its strength warrants.
Heat treatment. -- Heat treatment for toughening and increasing the strength is important with this steel. The heat treatment must be modified in accordance with the experience of each user and to suit the size of the work as well as the combination of strength and toughness desired. The steel should be heat treated whenever reliability is essential. Heat treatments H, D, or E may be employed. Machining may precede the heat treatment, depending somewhat upon the convenience and nature of the treatment. When heat treatment E is applied, machining may follow the second operation or the slow cooling after heating to from 1500 degrees to 1550 degrees F. To obtain the most strength, a quenching medium like brine should be used. The yield point will then be correspondingly high, and the steel harder and more difficult to machine. If a moderately high yield point will suffice, oil may be used for quenching, and then machining may follow without any difficulty.
Hardness. -- The various degrees of hardness conforming to the heat treatments listed in the table "Physical Properties of Heat-treated Carbon Steels" are as follows: For a re-heating temperature of 400 degrees F., 260 Brinell and 42 scleroscope; for a re-heating temperature of 900 degrees F., 200 Brinell and 37 scleroscope; for a re-heating temperature of 1400 degrees F., 135 Brinell and 32 scleroscope.
Forty-five Per Cent Carbon Steel (Specification No. 1045). -- This steel is ordinarily known in the trade as a 0.45 per cent carbon machine steel. It is a structural steel of greater strength than the 0.35 per cent carbon steel, but its uses are more limited and are confined in general to such parts as require a higher degree of strength and considerable toughness. With the proper heat treatment the fatigue-resisting or endurance qualities are very high -- higher than in any of the steels previously mentioned. The 0.45 per cent carbon steel is commonly used for crankshafts, driving shafts, and propeller shafts. It has also been used for transmission gears, but is not quite hard enough without casehardening and is not tough enough with casehardening to produce safe gears. This steel should not be used for casehardened parts. When properly annealed it machines well, but not well enough for screw machine work.
Heat treatment. -- When 0.45 per cent carbon steel requires annealing, heat treatment E is suitable. Machining may follow operation 2, after the steel has been slowly cooled from a temperature ranging between 1500 degrees to 1550 degrees F. Heat treatment E is especially adapted to crankshafts and similar parts. Heat treatment H is also commonly applied to this quality of steel.
Hardness. -- The various degrees of hardness conforming to the heat treatments listed in the table "Physical Properties of Heat-treated Carbon Steels" are as follows: For a re-heating temperature of 400 degrees F., 300 Brinell and 45 scleroscope; for a re-heating temperature of 900 degrees F., 230 Brinell and 40 scleroscope; for a re-heating temperature of 1400 degrees F., 160 Brinell and 35 scleroscope.
Ninety-five Per Cent Carbon Steel (Specification No. 1095). -- This grade of steel is generally used for springs, and when properly heat treated very good results are possible. The physical characteristics of heat-treated spring steel are best determined by transverse tests, because steel as hard as tempered spring steel is difficult to hold in the jaws of tensile testing machine. There is more or less slip and also side strains, all of which tends to produce misleading results.
Heat treatment. -- Heat treatment F is recommended. It should be understood that the higher the drawing temperature, the lower the yield point, but if the material is drawn to too low a temperature it will be brittle. A few practical trials will indicate the best temper for any given shape or size of spring. The elastic limit of steel subjected to heat treatment F, as determined by transverse tests, varies from 90,000 to 180,000 pounds per square inch.
Nickel Steel -- 0.15 Per Cent Carbon (Specification No. 2315). -- This steel, containing 0.15 per cent carbon and 3.5 per cent nickel, is suitable for carburizing purposes and will produce parts with exceedingly strong and tough cores combined with a high-carbon exterior. This steel may also be used for structural purposes, although it should not be selected for such a purpose when ordering materials, as much better results will be obtained with a nickel steel higher in carbon. The 0.15 per cent carbon nickel steel is intended for casehardened gears of transmission systems and for other casehardened parts requiring a very tough, strong steel with a hardened outer surface. The composition of this steel and of others having a higher carbon content, may be obtained from the accompanying table "S. A. E. Specifications for Nickel and Nickel-chromium Steels." When used for structural purposes, the physical characteristics will range about as given in the table "Physical Properties of Annealed and Heat-treated Alloy Steels," which also includes various other alloy steels referred to later.
Heat treatment. -- Alloy steels in general should be heat-treated and not be used in an annealed or natural condition, because the advantage of an annealed alloy steel as compared with a plain carbon steel is as a rule not in proportion with the increased cost. By means of heat treatment, however, there is a very marked improvement in physical characteristics.
The method of casehardening nickel steel No. 2315 may be varied considerably. As a rule, those parts which are made of nickel steel requiere the best treatment for casehardening. Heat treatment G is recommended. The second quenching (operation 6) should be at the lowest temperature at which the material will harden, which is sometimes below 1300 degrees F. The final drawing (operation 7) may be omitted in some cases. Parts of intricate shape with abrupt changes of thickness, sharp corners, etc. (especially sliding gears), should always be drawn to relieve internal strains.
Nickel Steel -- 0.20 Per Cent Carbon (Specification No. 2320). -- This steel, containing 0.20 per cent carbon and 3.5 per cent nickel, may be used interchangeably with steel No. 2315. The former, although intended primarily for casehardening, may properly be used for structural parts, and when suitably heat treated, will give elastic limits somewhat higher than the nickel steel containing 0.15 per cent carbon.
Heat treatment. -- For casehardening heat treatment G is recommended, and for structural purposes heat treatment H or K. The quenching temperatures, as with other steels, may be modified to meet individual cases.
Hardness. -- The various degrees of hardness conforming to the heat treatments listed in the table "Physical Properties of Heat-treated Alloy Steels" are as follows: For a re-heating temperature of 400 degrees F., 375 Brinell and 55 scleroscope; for a re-heating temperature of 900 degrees F., 280 Brinell and 42 scleroscope; for a re-heating temperature of 1400 degrees F., 125 Brinell and 28 scleroscope.
Nickel Steel -- 0.30 Per Cent Carbon (Specification No. 2330). -- This steel containing 0.30 per cent carbon and 3.5 per cent nickel, is intended primarily for heat-treated structural parts when strength and toughness are desired, as in the case of axles, front wheel spindles, crankshafts, driving shafts and transmission shafts. The physical characteristics of this steel are practically the same as those of No. 2320, slight modifications in the heat treatment much more than offsetting the slight difference in carbon content.
Heat treatment. -- Heat treatment H may be employed, although a higher refinement may be obtained by heat treatment K. Wide variations of yield point or elastic limit are possible by the use of different quenching mediums (oil, water, or brine) and by varying the drawing temperatures from 500 up to 1200 degrees F.
Hardness. -- The various degrees of hardness conforming to the heat treatments listed in the table "Physical Properties of Heat-treated Alloy Steels" are as follows: For a re-heating temperature of 400 degrees F., Brinell 436 and scleroscope 60; for a re-heating temperature of 900 degrees F., Brinell 300 and scleroscope 46; for a re-heating temperature of 1400 degrees F., Brinell 150 and scleroscope 30.
Nickel Steel -- 0.35 Per Cent Carbon (Specification No. 2335). -- The preceding remarks regarding nickel steel No. 2330 may also be applied to this steel which contains 3.5 per cent nickel and 0.35 per cent carbon. It will respond a little more sharply to heat treatment, and can be forced to higher elastic limits.
Nickel Steel -- 0.40 Per Cent Carbon (Specification No. 2340). -- This steel, containing 0.40 per cent carbon and 3.5 per cent nickel, is not used extensively. As the carbon content is higher than generally used, greater hardness is obtained by quenching and as this is accompanied by increased brittleness, the treatments must be modified to meet this condition. For example, the final quenching may be at a relatively low temperature and the final drawing temperature must be determined carefully in order to produce the desired toughness and other physical characteristics.
Nickel-chromium Steel -- 0.20 Per Cent Carbon (Specification No. 3120). -- By referring to the accompanying table, "S. A. E. Specifications for Nickel and Nickel-chromium Steels," it will be seen that there are five nickel-chromium steels (specifications Nos. 3120 to 3140 inclusive) which differ as to carbon content but have the same percentage of manganese, nickel and chromium. The nickel-chromium steel conforming to specification No. 3120 is intended primarily for case-hardening, and it may also be used for structural parts if suitably heat-treated. This steel should not be used in a natural or untreated condition.
The four grades of steel conforming to specification numbers 3125, 3130, 3135 and 3140 are intended for structural purposes, and are used in a heat-treated condition. Steels Nos. 3125 and 3130 may be used for casehardening.
Heat treatment. -- In general, the heat treatments and the properties resulting from them are much the same for nickel-chromium steels as for plain nickel steels, except that the effects of heat treatment are somewhat augmented by the chromium and increase with increasing amounts of nickel and chromium. Steel conforming to specification No. 3120 is casehardened by heat treatment G, and when used in structural parts is given heat treatment H or D. Heat treatment H, D or E is applied to steels Nos. 3125, 3130, 3135 and 3140.
Other Nickel-chromium Steels. -- The important applications of the other nickel-chromium steels listed in the table "S. A. E. Specifications for Nickel and Nickel-chromium Steels" are as follows:
Specification No. 3220. -- This steel is intended for casehardened parts, but when this grade of steel is required, very careful heat treatment is necessary, heat treatment G being recommended. This same steel may also be used for structural purposes, in which case it should receive heat treatment H or D.
Specification No. 3230. -- This grade of nickel-chromium steel is intended for the most important structural parts and should be used only in a heat-treated condition. Heat treatment H or D is recommended.
Specification No. 3240. -- This quality of steel is suitable for structural parts requiring unusual strength. Higher elastic limit is possible with a given heat treatment than in the case of a steel like No. 3230. The toughness will not be quite as great, but the steel is applicable where strength rather than toughness is the controlling factor. Heat treatment H or D is recommended.
Specification No. 3250. -- This steel is intended for gears requiring extreme strength and hardness. Either heat treatment M or Q should be applied, Q giving the better results.
Specification No. 3415. -- This steel is intended primarily for casehardening. It is considerably higher in nickel than the nickel-chromium steels previously referred to. Heat treatment G should be followed unless the steel is used for structural parts, when heat treatment M is applied.
Specification No. 3435. -- This steel is intended for very important structural parts such as crankshafts, axles, spindles, driving shafts and transmission shafts. Heat treatment P or R is recommended. This steel is not intended for casehardening.
Specification No. 3450. -- This quality of steel may also be used for gears requiring extreme strength and hardness. Heat treatment R should be used, although heat treatment P is also applicable.
Specification No. 3320. -- The remarks made in connection with No. 3220 apply to this steel also. There is no appreciable difference in the physical characteristics. Heat treatment L should be used for carburizing.
Specification No. 3330. -- This steel, like 3230, is intended for very important structural parts. The high nickel and chromium contents make it exceedingly tough and strong when treated according to heat treatment P or R.
Specification No. 3340. -- This steel is suitable for gears to be hardened without carburizing. The remarks made in connection with steel No. 3240 and 3250 apply. Heat treatment L should be used.
Chromium Steels. -- Four grades of chromium steels are included in the accompanying table "S. A. E. Specifications for Chromium and Chromium-vanadium Steels". Chromium steel No. 5120 is a casehardening grade of much better quality than carbon steel and is similar in this respect to nickel steel No. 2320 and nickel-chromium steel No. 3120. Heat treatment B is recommended for steel No. 5120. Chromium steel No. 5140 is similar to nickel-chromium steel No. 3140. When given heat treatment H or D, it is suitable for high-duty shafting, etc. The drawing temperature should be moderately high, in order to secure a safe degree of toughness.
|Range of Carbon Content, Per Cent||Range of Manganese Content, Per Cent||Physical Properties -- Average Minimum Values given *|
|Heating Temp., Deg. F.||Re-heating Temp., Deg. F.||Tensile Strength, Lbs. per Sq. In.||Elastic LImit, Lbs. per Sq. In.||Reduction of Area, Per Cent.||Elongation in 2 Inches, Per Cent|
Chromium-vanadium Steels. -- The specifications of eight different grades are given in the table "S. A. E. Specifications for Chromium and Chromium-vanadium Steels." The principal applications of these steels are as follows:
Specification No. 6120. -- This quality of steel is intended primarily for casehardening. It is used for the most important parts, such as casehardened shafts, gears, etc. While this steel may be used in a heat-treated condition for structural purposes, some of the steels referred to in the following are preferable, particularly where greater strength is desired. Heat treatment S is recommended for casehardening and heat treatment for structural parts.
Specification No. 6125. -- The difference between this steel and No. 6120 is very slight, and they may be used interchangeably for structural purposes. This steel may be casehardened, but it is not first choice for this purpose.
Specification No. 6130. -- This steel can be used interchangeably with No. 6125 for structural purposes, but it should not be used for casehardening. When subjected to heat treatment T, it possesses a high degree of combined strength and toughness.
Specification No. 6135. -- This specification provides an excellent quality of steel for structural parts that are to be heat-treated. The fatigue-resisting or endurance qualities of this steel are very good. Heat treatment T is recommended.
Specification No. 6140. -- This is a very good quality of steel for use where a high degree of strength is desired in conjunction with considerable toughness. Its fatigue-resisting qualities are very high, and it is a first-class material for high-duty shafts. Heat treatment T is recommended.
Specification No. 6145. -- This quality of steel contains sufficient carbon in combination with chromium and vanadium to harden to a considerable degree when quenched at a suitable temperature, and it may be used for gears and springs. For gears this steel should be annealed after forging and before machining, the annealing being done by following operations 1 and 2 of heat treatment U. For structural parts requiring great strength, heat treatment T is recommended.
Specification No. 6150. -- The remarks regarding steel No. 6145 apply to this steel. It is suitable for springs, and when given the right heat treatment, very high elastic limits are obtained. For spring material, heat treatment U is recommended, except that the last drawing (operation 6) temperature should be higher -- probably from 700 degrees to 1100 degrees F. -- the temperature varying with the section of the material.
Silico-manganese Steels. -- The two silico-manganese steels listed in the accompanying table of specifications have been standardized by usage principally as spring steel. No. 9260 is also used to some extent for gears. Neither steel is suitable for use without heat treatment. The two specifications are given to meet the requirements of, first, those manufacturers believing in relatively low-carbon and high-silicon steel, and those desiring higher carbon and lower silicon.
|Range of Carbon Content, Per Cent||Range of Nickel Content, Per Cent||Physical Properties -- Average Minimum Values given *|
|Heating Temp., Deg. F.||Re-heating Temp., Deg. F.||Tensile Strength, Lbs. per Sq. In.||Elastic LImit, Lbs. per Sq. In.||Reduction of Area, Per Cent.||Elongation in 2 Inches, Per Cent|
|Yield Point, Lbs. per Sq. In.||Reduction of Area, Per Cent||Elongation in 2 in., Per Cent||Heat Treatment Letter #||Yield Point, Lbs. per Sq. In.||Reduction of Area, Per Cent||Elongation in 2 in., Per Cent|
|2315||35,000-45,000||65-45||35-25||H or K||40,000-80,000||65-40||35-15|
|2320||40,000-50,000||65-40||30-20||H or K||50,000-125,000||65-40||25-10|
|2330||40,000-50,000||60-40||30-20||H or K||60,000-130,000||60-30||25-10|
|2335||45,000-55,000||55-35||25-15||H or K||65,000-160,000||55-25||25-10|
|2340||55,000-65,000||50-30||25-15||H or K||70,000-200,000||55-15||25- 5|
|3120||30,000-40,000||55-40||35-25||H or D||40,000-100,000||65-40||25-15|
|3125||40,000-55,000||50-35||30-20||H, D or E||50,000-125,000||55-25||25-10|
|3130||40,000-55,000||50-35||30-20||H, D or E||50,000-125,000||55-25||25-10|
|3135||45,000-60,000||45-30||25-15||H, D or E||55,000-150,000||50-25||20- 5|
|3140||45,000-60,000||45-30||25-15||H, D or E||55,000-150,000||50-25||20- 5|
|3220||35,000-45,000||60-45||25-20||H or D||45,000-120,000||65-30||20- 5|
|3230||40,000-50,000||55-40||25-15||H or D||60,000-175,000||60-30||20- 5|
|3240||45,000-60,000||50-40||25-15||H or D||65,000-200,000||50-20||15- 2|
|3250||50,000-60,000||50-40||25-15||M or Q||150,000-200,000||25-15||15- 2|
|3435||45,000-55,000||55-40||25-15||P or R||60,000-175,000||60-30||20- 5|
High-Chromium or "Stainless" Steel. --
Heat treatment. --
Heat treatment for Valves. --
|Quenched in oil from degrees F.||1600||1600||1650|
|Tempered at degrees F.||1160||1080||1100|
|Yield point, lb. per sq. in.||78300||75000||91616|
|Tensile strength, lb. per sq. in.||104600||104250||123648|
|Elongation in 2 in., per cent||25.0||23.5||14.5|
|Reduction of area, per cent||52.5||51.4||33.5|
Cobaltcrom Steel. -- This is a tungstenless alloy steel or high-speed steel which contains approximately 1.5 per cent carbon, 12.5 per cent chromium, and 3.5 per cent cobalt. Tools such as dies, milling cutters, etc., made from cobaltcrom steel can be cast to shape in suitable molds, the teeth of cutters being formed so that it is necessary only to grind them.
Before the blanks can be machined, they must be annealed; this operation is performed by pack-annealing at the temperature of 1800 degrees F., for a period of from three to six hours, according to the size of the castings being annealed. The following directions are given for the hardening of blanking and trimming dies, milling cutters, and similar tools made from cobaltcrom steel: Heat slowly in a hardening furnace to about 1830 degrees F., and hold the temperature at this point until the tools are thoroughly soaked. Then reduce the temperature about 50 degrees, withdraw the tools from the furnace, and allow them to cool in the atmosphere. As soon as the red color disappears from the cooling tool, place it in quenching oil until cold. The slight drop of 50 degrees in temperature while the tool is still in the hardening furnace is highly important in order to obtain proper results. The steel will be injured if the tool is heated above 1860 degrees F. In cooling milling cutters or other rotary tools, it is suggested that they be suspended on a wire to insure a uniform rate of cooling.
Tools that are subjected to shocks or vibration, such as pneumatic rivet sets, shear blades, etc., should be heated slowly to 1650 degrees F., after which the temperature should be reduced to about 1610 degrees F., at which point the tool should be removed from the furnace and permitted to cool in the atmosphere. There is no appreciable scaling present in the hardening of cobaltcrom steel tools.
General Properties of Alloy Steels. -- Alloy or "special" steels are combinations of iron and carbon with some other element, such as nickel, chromium, tungsten, vanadium, manganese and molybdenum. All of these metals give certain distinct properties to the steel, but in all cases the principal quality is the increase in hardness and toughness.
Nickel steel usually contains from 3 to 3.5 per cent nickel (ordinarily not over 5 per cent), and from 0.20 to 0.40 per cent carbon. This steel is used for armor plate, ammunition, bridge construction, rails, etc. One of the reasons why nickel steel is adapted for armor plate is that it does not crack when perforated by a projectile. The Krupp steel used for armor plate contains approximately 3.5 per cent nickel, 1.5 per cent chromium and 0.25 per cent carbon. The advantages claimed for nickel steel for railroad rails are its increased resistance to abrasion and high elastic limit. On sharp curves, it has been estimated that a nickel steel rail will outlast four ordinary rails.
Chromium steel is well adapted for armor-piercing projectiles, owing to its hardness, toughness and stiffness, and is extensively used for this purpose. Chromium steel is also used in the construction of safes and for castings subjected to unusually severe stresses, such as those used in rock-crushing machinery, etc. The percentage of chromium used in chromium steels varies over quite a wide range in the low-chromium and high-chromium steels.
Tungsten steel is largely employed for high-speed metal cutting tools and magnet steels. It has also been used in the manufacture of armor plate and armor-piercing projectiles, in which case it is combined either with nickel or chromium or with both of these metals. The property that tunsten imparts to steel is that of hardening in the air, after heating to the required temperature. This steel usually contains 5 to 15 per cent tungsten (although the percentage is sometimes as high as 24 per cent) and from 0.4 to 2 per cent carbon.
Vanadium steels ordinarily contain 0.16 to 0.25 per cent vanadium. The effect of vanadium is to increase the tensile strength and elastic limit, and it gives the steel the valuable property of resisting, to an unusual degree, repeated stresses. Vanadium steel is especially adapted for springs, car axles, gears subjected to severe service, and for all parts which must withstand constant vibration and varying stresses.
Manganese steel (also known as Hadfield managanese steel) contains about 12 per cent manganese and from 0.8 to 1.25 per cent carbon. If there is only 1.5 per cent manganese, the steel is very brittle, and additional manganese increases this brittleness until the quantity has reached 4 to 5.5 per cent, when the steel can be pulverized under the hammer. With a further increase of manganese, the steel becomes ductile and very hard, these qualities being at there highest degree when the manganese content is 12 per cent. The ductility of the steel is brought out by sudden cooling, the process being opposite that employed for carbon steel.
Molybdenum steels have properties similar to tungsten steels, except that a smaller quantity of molybdenum than of tungsten is required to secure corresponding results.
Screw Stock. -- The composition of ordinary screw stock should be, in general, about as follows: Carbon, from 0.08 to 0.20 per cent; manganese, 0.30 o 0.80 per cent; phosphorus, not to exceed 0.12 per cent; sulphur, 0.06 to 0.12 per cent. Screw stock is easily machined and cheap, but lacks strength and toughness and is not safe for vital parts. Screws made from hot-rolled bars of this material should be heat-treated and not used in an annealed condition. Screws made from cold-rolled bars are much stronger, but the best results, in either case, are obtained by the following heat treatment: After machining, heat to 1500 degrees F.; quench; re-heat from 600 degrees to 1300 degrees F., and cool slowly.
Later -- I got some feedback, after a couple of years, from someone who would like to see that next section, and though it's just one person, I'll guess that it would be useful to more. So I'll get started soon. (This paragraph written 6/29/98)
Further: 4/24/00, got another request. Total of two. OK, I'll start on it.
Here's the link:Testing the Hardness of Metals
Detailed table of contents
First section: Furnaces and Baths for Heating Steel
Previous section: Casehardening
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