Sulphur is another impurity and high sulphur is even a greater detriment to steel than phosphorus. High sulphur up to 0.09 per cent helps machining properties, but has a tendency to make the steel "hot short," i.e., subject to opening up cracks and seams at forging or rolling heats. Sulphur should never exceed 0.06 per cent nor phosphorus 0.08 per cent.

Steel used for tool purposes should have as low phosphorus and sulphur contents as possible, not over 0.02 per cent.

We can sum up the various factors something as follows for ready reference.

The ingredient Its effect

Iron The basis of steel Carbon The determinative Sulphur A strength sapper Phosphorus The weak link Oxygen A strength destroyer Manganese For strength Nickel For strength and toughness Tungsten Hardener and heat resister Chromium For resisting shocks Vanadium Purifier and fatigue resister Silicon Impurity and hardener t.i.tanium Removes nitrogen and oxygen Molybdenum Hardener and heat resister Aluminum Kills or deoxidizes steel

PROPERTIES OF ALLOY STEELS

The following table shows the percentages of carbon, manganese, nickel, chromium and vanadium in typical steel alloys for engineering purposes. It also gives the elastic limit, tensile strength, elongation and reduction of area of the various alloys, all being given the same heat treatment with a drawing temperature of 1,100F. (600C.). The specimens were one inch rounds machined after heat treatment.

Tungsten is not shown in the table because it is seldom used in engineering construction steels and then usually in combination with chromium. Tungsten is used princ.i.p.ally for the magnets of magnetos, to some extent in the manufacture of hacksaws, and for special tool steels.

TABLE I.--PROPERTIES OF ALLOY STEELS ------------------------------------------------------------------------------ Manganese,/ Chromium,/ |Elastic|Tensile |Elongation|Reduction Carbon, per /Nickel, per /Vanadium,|limit, |Strength,|in 2 in., | of area, per | cent | per | cent |per cent |lb. per|lb. per |per cent | per cent cent | | cent | | |sq. in.|sq. in. | | -------|------|-------|------|---------|-------|---------|----------|--------- 0.27 | 0.55 | | | | 49,000| 80,000 | 30 | 65 0.27 | 0.47 | | | 0.26 | 66,000| 98,000 | 25 | 52 0.36 | 0.42 | | | | 58,000| 90,000 | 27 | 60 0.34 | 0.87 | | | 0.13 | 82,500| 103,000 | 22 | 57 0.45 | 0.50 | | | | 65,000| 96,000 | 22 | 52 0.43 | 0.60 | | | 0.32 | 96,000| 122,000 | 21 | 52 0.47 | 0.90 | | | 0.15 |102,000| 127,500 | 23 | 58 0.30 | 0.60 | 3.40 | | | 75,000| 105,000 | 25 | 67 0.33 | 0.63 | 3.60 | | 0.25 |118,000| 142,000 | 17 | 57 0.30 | 0.49 | 3.60 | 1.70 | |119,000| 149,500 | 21 | 60 0.25 | 0.47 | 3.47 | 1.60 | 0.15 |139,000| 170,000 | 18 | 53 0.25 | 0.50 | 2.00 | 1.00 | |102,000| 124,000 | 25 | 70 0.38 | 0.30 | 2.08 | 1.16 | |120,000| 134,000 | 20 | 57 0.42 | 0.22 | 2.14 | 1.27 | 0.26 |145,000| 161,500 | 16 | 53 0.36 | 0.61 | 1.46 | 0.64 | |117,600| 132,500 | 16 | 58 0.36 | 0.50 | 1.30 | 0.75 | 0.16 |140,000| 157,500 | 17 | 54 0.30 | 0.50 | | 0.80 | | 90,000| 105,000 | 20 | 50 0.23 | 0.58 | | 0.82 | 0.17 |106,000| 124,000 | 21 | 66 0.26 | 0.48 | | 0.92 | 0.20 |112,000| 137,000 | 20 | 61 0.35 | 0.64 | | 1.03 | 0.22 |132,500| 149,500 | 16 | 54 0.50 | 0.92 | | 1.02 | 0.20 |170,000| 186,000 | 15 | 45 ------------------------------------------------------------------------------

NON-SHRINKING, OIL-HARDENING STEELS

Certain steels have a very low rate of expansion and contraction in hardening and are very desirable for test plugs, gages, punches and dies, for milling cutters, taps, reamers, hard steel bushings and similar work.

It is recommended that for forging these steels it be heated slowly and uniformly to a bright red, but not in a direct flame or blast.

Harden at a dull red heat, about 1,300F. A clean coal or c.o.ke fire, or a good m.u.f.fle-gas furnace will give best results. Fish oil is good for quenching although in some cases warm water will give excellent results. The steel should be kept moving in the bath until perfectly cold. Heated and cooled in this way the steel is very tough, takes a good cutting edge and has very little expansion or contraction which makes it desirable for long taps where the accuracy of lead is important.

The composition of these steels is as follows:

Per cent Manganese 1.40 to 1.60 Carbon 0.80 to 0.90 Vanadium 0.20 to 0.25

[Ill.u.s.tration: FIG. 13.--Effect of copper in steel.]

EFFECT OF A SMALL AMOUNT OF COPPER IN MEDIUM-CARBON STEEL

This shows the result of tests by C. R. Hayward and A. B. Johnston on two types of steel: one containing 0.30 per cent carbon, 0.012 per cent phosphorus, and 0.860 per cent copper, and the other 0.365 per cent carbon, 0.053 per cent phosphorus, and 0.030 per cent copper. The accompanying chart in Fig. 13 shows that high-copper steel has decided superiority in tensile strength, yield point and ultimate strength, while the ductility is practically the same.

Hardness tests by both methods show high-copper steel to be harder than low-copper, and the Charpy shock tests show high-copper steel also superior to low-copper. The tests confirm those made by Stead, showing that the behavior of copper steel resembles that of nickel steel. The high-copper steels show finer grain than the low-copper.

The quenched and drawn specimens of high-copper steel were found to be slightly more martensitic.

HIGH-CHROMIUM OR RUST-PROOF STEEL

High-chromium, or what is called stainless steel containing from 11 to 14 per cent chromium, was originally developed for cutlery purposes, but has in the past few years been used to a considerable extent for exhaust valves in airplane engines because of its resistance to scaling at high temperatures.

Percentage Carbon 0.20 to 0.40 Manganese, not to exceed 0.50 Phosphorus, not to exceed 0.035 Sulphur, not to exceed 0.035 Chromium 11.50 to 14.00 Silicon, not to exceed 0.30

The steel should be heated slowly and forged at a temperature above 1,750F. preferably between 1,800 and 2,200F. If forged at temperatures between 1,650 and 1,750F. there is considerable danger of rupturing the steel because of its hardness at red heat. Owing to the air-hardening property of the steel, the drop-forgings should be trimmed while hot. Thin forgings should be reheated to redness before tr.i.m.m.i.n.g, as otherwise they are liable to crack.

The forgings will be hard if they are allowed to cool in air. This hardness varies over a range of from 250 to 500 Brinell, depending on the original forging temperature.

ANNEALING can be done by heating to temperatures ranging from 1,290 to 1,380F. and cooling in air or quenching in water or oil. After this treatment the forgings will have a hardness of about 200 Brinell and a tensile strength of 100,000 to 112,000 lb. per square inch.

If softer forgings are desired they can be heated to a temperature of from 1,560 to 1,650F. and cooled very slowly. Although softer the forgings will not machine as smoothly as when annealed at the lower temperature.

HARDENING.--The forgings can be hardened by cooling in still air or quenching in oil or water from a temperature between 1,650 and 1,750F.

The physical properties do not vary greatly when the carbon is within the range of composition given, or when the steel is hardened and tempered in air, oil, or water.

When used for valves the following specification of physical properties have been used:

Yield point, pounds per square inch 70,000 Tensile strength, pounds per square inch 90,000 Elongation in 2 in., per cent 18 Reduction of area, per cent 50

The usual heat treatment is to quench in oil from 1,650F. and temper or draw at 1,100 to 1,200F. One valve manufacturer stated that valves of this steel are hardened by heating the previously annealed valves to 1,650F. and cooling in still air. This treatment gives a scleroscope hardness of about 50.

In addition to use in valves this steel should prove very satisfactory for shafting for water-pumps and other automobile parts subject to objectionable corrosion.

TABLE 2.--COMPARISON OF PHYSICAL PROPERTIES FOR HIGH-CHROMIUM STEELS OF DIFFERENT CARBON CONTENT -------------------------------------------------------------------------- | C 0.20 | C 0.27 | C 0.50 | Mn 0.45 | Mn 0.50 | | Cr 12.56 | Cr 12.24 | Cr 14.84 -----------------------------------------|----------|----------|---------- Quenched in oil from degrees Fahrenheit | 1,600 | 1,600 | 1,650 Tempered at degrees Fahrenheit | 1,160 | 1,080 | 1,100 Yield point, pounds per square inch | 78,300 | 75,000 | 91,616 Tensile strength, pounds per square inch | 104,600 | 104,250 | 123,648 Elongation in 2 in., per cent | 25.0 | 23.5 | 14.5 Reduction of area, per cent | 52.5 | 51.4 | 33.5 --------------------------------------------------------------------------

TABLE 3.--COMPARISON OF PHYSICAL PROPERTIES BETWEEN AIR, OIL AND WATER-HARDENED STEEL HAVING CHEMICAL a.n.a.lYSIS IN PERCENTAGE OF ------------------------------------------------------------------------- Carbon 0.24 Manganese 0.30 Phosphorus 0.035 Sulphur 0.035 Chromium 12.85 Silicon 0.20

------------------------------------------------------------------------- | Hardened | | Elastic | Tensile | | Hardening| from, | Tempered | limit, |strength,|Elongation|Reduction medium | degrees |at, degrees| per lb. |lb. Per | in 2 in. |of area, |Fahrenheit|Fahrenheit | sq. in. | sq. in. | per cent |per cent ---------|----------|-----------|---------|---------|----------|--------- | | 930 | 158,815 | 192,415 | 13.0 | 40.5 | | 1,100 | 99,680 | 120,065 | 21.0 | 59.2 Air | 1,650 | 1,300 | 70,785 | 101,250 | 26.0 | 64.6 | | 1,380 | 66,080 | 98,335 | 28.0 | 63.6 | | 1,470 | 70,785 | 96,990 | 27.0 | 64.7 ---------|----------|-----------|---------|---------|----------|--------- | | 930 | 163,070 | 202,720 | 8.0 | 18.2 Oil | 1,650 | 1,100 | 88,255 | 116,480 | 20.0 | 56.9 | | 1,300 | 77,950 | 105,505 | 25.5 | 63.8 | | 1,380 | 88,255 | 98,785 | 27.0 | 66.3 ---------|----------|-----------|---------|---------|----------|--------- | | 930 | 158,815 | 202,050 | 12.0 | 34.2 Water | 1,650 | 1,100 | 90,270 | 120,735 | 22.0 | 59.8 | | 1,300 | 66,080 | 102,590 | 25.8 | 64.8 | | 1,380 | 67,200 | 97,890 | 27.0 | 65.2 -------------------------------------------------------------------------

This steel can be drawn into wire, rolled into sheets and strips and drawn into seamless tubes.

CORROSION.--This steel like any other steel when distorted by cold working is more sensitive to corrosion and will rust. Rough cut surfaces will rust. Surfaces finished with a fine cut are less liable to rust. Ground and polished surfaces are practically immune to rust.

When chromium content is increased to 16 to 18 per cent and silicon is added, from 2 to 4 per cent, this steel becomes rust proof in its raw state, as soon as the outside surface is removed. It does not need to be heat-treated in any way. These compositions are both patented.

S. A. E. STANDARD STEELS

The following steel specifications are considered standard by the Society of Automotive Engineers and represents automobile practice in this country. These tables give the S. A. E. number, the composition of the steel and the heat treatment. These are referred to by letter--the heat treatments being given in detail on pages 134 to 137 in Chap. 8. It should be noted that the percentage of the different ingredients desired is the mean, or halfway between the minimum and maximum.

TABLE 4.--CARBON STEELS ------------------------------------------------------------------------------ S. A. E. | Carbon | Manganese | | | Specification|(minimum and |(minimum and |Phosphorus| Sulphur | Heat no. | maximum) | maximum) |(maximum) |(maximum)| treatment -------------|-------------|-------------|----------|---------|--------------- 1,010 | 0.05 to 0.15| 0.30 to 0.60| 0.045 | 0.05 |Quench at 1,500 1,020 | 0.15 to 0.25| 0.30 to 0.60| 0.045 | 0.05 | A or B 1,025 | 0.20 to 0.30| 0.50 to 0.80| 0.045 | 0.05 | H | | | | | 1,035 | 0.30 to 0.40| 0.50 to 0.80| 0.045 | 0.05 | H, D or E 1,045 | 0.40 to 0.50| 0.50 to 0.80| 0.045 | 0.05 | H, D or E 1,095 | 0.90 to 1.05| 0.25 to 0.50| 0.040 | 0.05 | F ------------------------------------------------------------------------------

TABLE 5.--SCREW STOCK --------------------------------------------------------------------------- S. A. E. | Carbon | Manganese | Phosphorus | Sulphur Specification no.| | | (maximum) | -----------------|--------------|--------------|------------|-------------- 1,114 | 0.08 to 0.20 | 0.30 to 0.80 | 0.12 | 0.06 to 0.12 ---------------------------------------------------------------------------

TABLE 6.--NICKEL STEELS ----------------------------------------------------------------------------- S. A. E. | | | Phosphorus| | | Specification | | | (maximum) | | | no. ---- | / | | | Carbon | Manganese | | Sulphur | Nickel | Heat |(minimum and|(minimum and| |(maximum)|(minimum and|treatment | maximum) | maximum) | | | maximum) | ---------|------------|------------|-------|---------|------------|---------- 2,315 |0.10 to 0.20|0.50 to 0.80| 0.04 | 0.045 |3.25 to 3.75|G, H or K 2,320 |0.15 to 0.25|0.50 to 0.80| 0.04 | 0.045 |3.25 to 3.75|G, H or K 2,330 |0.25 to 0.35|0.50 to 0.80| 0.04 | 0.045 |3.25 to 3.75| H or K | | | | | | 2,335 |0.30 to 0.40|0.50 to 0.80| 0.04 | 0.045 |3.25 to 3.75| H or K 2,340 |0.35 to 0.45|0.50 to 0.80| 0.04 | 0.045 |3.25 to 3.75| H or K 2,345 |0.40 to 0.50|0.50 to 0.80| 0.04 | 0.045 |3.25 to 3.75| H or K -----------------------------------------------------------------------------

TABLE 7.--NICKEL-CHROMIUM STEELS ------------------------------------------------------------------------------- S. A. E. | | | Phosphorus| Sulphur | | | Specification| | | (maximum)|(maximum) | | | Heat no. ------ | ------ | ---- | |treatment | Carbon | Manganese | | | Nickel | Chromium |(minimum and|(minimum and| | |(minimum and|(minimum and | | maximum) | maximum) | | | maximum) | maximum) | ------|------------|------------|----|-----|------------|-------------|-------- 3,120|0.15 to 0.25|0.50 to 0.80|0.04|0.045|1.00 to 1.50|0.45 to 0.75*|G,H or D 3,125|0.20 to 0.30|0.50 to 0.80|0.04|0.045|1.00 to 1.50|0.45 to 0.75*|H,D or E 3,130|0.25 to 0.35|0.50 to 0.80|0.04|0.045|1.00 to 1.50|0.45 to 0.75*|H,D or E | | | | | | | 3,135|0.30 to 0.40|0.50 to 0 80|0.04|0.045|1.00 to 1.50|0.45 to 0 75*|H,D or E 3,140|0.35 to 0.45|0.50 to 0.80|0.04|0.045|1.00 to 1.50|0.45 to 0.75*|H,D or E 3,220|0.15 to 0.25|0.30 to 0.60|0.04|0.040|1.50 to 2.00|0.90 to 1.25 |G,H or D | | | | | | | 3,230|0.25 to 0.35|0.30 to 0.60|0.04|0.040|1.50 to 2.00|0.90 to 1.25 | H or D 3,240|0.35 to 0.45|0.30 to 0.60|0.04|0.040|1.50 to 2.00|0.90 to 1.25 | H or D 3,250|0.45 to 0.55|0.30 to 0.60|0.04|0.040|1.50 to 2.00|0.90 to 1.25 | M or Q | | | | | | | X3,315|0.10 to 0.20|0.45 to 0.75|0.04|0.040|2.75 to 3.25|0.60 to 0.95 | G X3,335|0.30 to 0.40|0.45 to 0.75|0.04|0.040|2.75 to 3.25|0.60 to 0.95 | P or R X3,350|0.45 to 0.55|0.45 to 0.75|0.04|0.040|2.75 to 3.25|0.60 to 0.95 | P or R | | | | | | | 3,320|0.15 to 0.25|0.30 to 0.60|0.04|0.040|3.25 to 3.75|1.25 to 1.75 | L 3,330|0.25 to 0.35|0.30 to 0.60|0.04|0.040|3.25 to 3.75|1.25 to 1.75 | P or R 3,340|0.35 to 0.45|0.30 to 0.60|0.04|0.040|3.25 to 3.75|1.25 to 1.75 | P or R ------------------------------------------------------------------------------- * Another grade of this type of steel is available with chromium content of 0.15 per cent to 45 per cent. It has somewhat lower physical properties.

TABLE 8.--CHROMIUM STEELS ------------------------------------------------------------------------------- S. A. E. | | | | | | Specification| | | | | | no. --- Carbon | Manganese | | | Chromium | |(minimum and|(minimum and|Phosphorus|Sulphur |(minimum and| Heat | maximum) | maximum) |(maximum) |(maximum)| maximum) |treatment ---------|------------|------------|----------|---------|------------|--------- 5,120 |0.15 to 0.25| * | 0.04 | 0.045 |0.65 to 0.85| B 5,140 |0.35 to 0.45| * | 0.04 | 0.045 |0.65 to 0.85| H or D 5,165 |0.60 to 0.70| * | 0.04 | 0.045 |0.65 to 0.85| H or D | | | | | | 5,195 |0.90 to 1.05|0.20 to 0.45| 0.03 | 0.03 |0.90 to 1.10|M, P or R 51,120 |1.10 to 1.30|0.20 to 0.45| 0.03 | 0.03 |0.90 to 1.10|M, P or R 5,295 |0.90 to 1.05|0.20 to 0.45| 0.03 | 0.03 |1.10 to 1.30|M, P or R 52,120 |1.10 to 1.30|0.20 to 0.45| 0.03 | 0.03 |1.10 to 1.30|M, P or R ------------------------------------------------------------------------------- --Two types of steel are available in this cla.s.s, one with manganese 0.25 to 0.50 per cent (0.35 per cent desired), and silicon not over 0.20 per cent; the other with manganese 0.60 to 0.80 per cent (0.70 per cent desired), and silicon 0.15 to 0.50 per cent.

TABLE 9.--CHROMIUM-VANADIUM STEELS ------------------------------------------------------------------------------- S. A. E. | | |Phosphorus| Sulphur | |Vanadium | Specification| | | (maximum)|(maximum)| |(minimum)| no. ------ | -- | / - | | Carbon | Manganese | | | Chromium | | Heat |(minimum and|(minimum and| | |(minimum and| |treatment | maximum) | maximum) | | | maximum) | | ------|------------|------------|-------|-------|------------|-------|--------- 6,120 |0.15 to 0.25|0.50 to 0.80| 0.04 | 0.04 |0.80 to 1.10| 0.15 | S 6,125 |0.20 to 0.30|0.50 to 0.80| 0.04 | 0.04 |0.80 to 1.10| 0.15 | S or T 6,130 |0.25 to 0.35|0.50 to 0.80| 0.04 | 0.04 |0.80 to 1.10| 0.15 | T or U 6,135 |0.30 to 0.40|0.50 to 0.80| 0.04 | 0.04 |0.80 to 1.10| 0.15 | T or U 6,140 |0.35 to 0.45|0.50 to 0.80| 0.04 | 0.04 |0.80 to 1.10| 0.15 | T or U 6,145 |0.40 to 0.50|0.50 to 0.80| 0.04 | 0.04 |0.80 to 1.10| 0.15 | U 6,150 |0.45 to 0.55|0.50 to 0.80| 0.04 | 0.04 |0.80 to 1.10| 0.15 | U 6,195 |0.90 to 1.05|0.20 to 0.45| 0.03 | 0.03 |0.80 to 1.10| 0.15 U -------------------------------------------------------------------------------

TABLE 10.--SILICO-MANGANESE STEELS ----------------------------------------------------------------------------- S. A. E. | | | | | | Specification| | | | | | no. ----- Carbon| Manganese | | | Silicon | |(minimum and|(minimum and|Phosphorus|Sulphur |(minimum and| Heat | maximum) | maximum) |(maximum) |(maximum)| maximum) |treatment -------|------------|------------|----------|---------|------------|--------- 9,250 |0.45 to 0.55|0.60 to 0.80| 0.045* | 0.045 |1.80 to 2.10| V 9,260 |0.55 to 0.65|0.50 to 0.70| 0.045* | 0.045 |1.50 to 1.80| V ----------------------------------------------------------------------------- * Steel made by the acid process may contain maximum 0.05 phosphorus.

LIBERTY MOTOR CONNECTING RODS

The requirements for materials for the Liberty motor connecting rods are so severe that the methods of securing the desired qualities will be of value in other lines. The original specifications called for chrome-nickel but the losses due to the difficulty of handling caused the Lincoln Motor Company to suggest the subst.i.tution of chrome-vanadium steel, and this was accepted by the Signal Corps. The rods were accordingly made from chromium-vanadium steel, containing carbon, 0.30 to 0.40 per cent; manganese, 0.50 to 0.80 per cent; phosphorus, not over 0.04 per cent; sulphur, not over 0.04 per cent; chromium, 0.80 to 1.10 per cent; vanadium, not less than 0.15 per cent. This steel is ordinarily known in the trade as 0.35 carbon steel, S. A. E., specification 6,135, which provides a first-rate quality steel for structural parts that are to be heat-treated.

The fatigue resisting or endurance qualities of this material are excellent. It has a tensile strength of 150,000 lb. minimum per square inch; elastic limit, 115,000 lb. minimum per square inch; elongation, 5 per cent minimum in 2 in.; and minimum reduction in area, 25 per cent.

The original production system as outlined for the manufacturers had called for a heat treatment in the rough-forged state for the connecting rods, and then semi-machining the rod forgings before giving them the final treatment. The Lincoln Motor Company insisted from the first that the proper method would be a complete heat treatment of the forging in the rough state, and machining the rod after the heat treatment. After a number of trial lots, the Signal Corps acceded to the request and production was immediately increased and quality benefited by the change. This method was later included in a revised specification issued to all producers.