MXPA00006935A - Free-machining martensitic stainless steel - Google Patents

Abstract

A corrosion resistant, martensitic stainless steel alloy is disclosed having the following composition in weight percent:carbon 0.06-0.10, manganese 0.50 max., silicon 0.40 max., phosphorus 0.060 max., sulfur 0.15-0.55, chromium 12.00-12.60, nickel 0.25 max., molybdenum 0.10 max., copper 0.50 max., nitrogen 0.04 max., and the balance is essentially iron. This alloy provides a unique combination of form tool machinability, corrosion resistance, and hardenability, particularly in the annealed condition (100 HRB max.). The alloy is capable of being hardened to at least 35 HRC.

Description

MARTENSITIC STAINLESS STEEL MACHINING EASY Field of the Invention This invention relates to martensitic stainless steel alloys and in particular to a martensitic stainless steel alloy having a composition that is balanced to provide a unique combination of machinability in a profiling machine, hardness and strength to the corrosion.

Background of the Invention The alloy Type 416 A.I.S.I. It is a hardened martensitic stainless steel alloy that provides a higher level of machinability in relation to other known grades of martensitic stainless steel. The standard compositions STM, UNS and AMS for the Type 416 alloy are as follows, in weight percent.

ASTM UNS AMS C 0.15 max. 0.15 max. 0.15 max.

Mn 1.25 max. 1.25 max. 2.50 max.

ASTM UNS AMS Yes 1.00 max. 1.00 max. 1.00 max, 0. 06 max. 0.060 max. 0.060 max. 0. 15 min. 0.15 min. 0.15-0.40 Cr 12.00-14.00 12.00-14.00 11.50-13.50 Ni 0.75 max.

Mo 0.060 max. 0.060 max. 0.060 max.1 Cu 0.50 max.

Faith Bal. Bal. Bal Mo or Zr Modifications to the basic Type 416 alloy have made improvements to improve its machinability including a positive addition of manganese or a combination of tellurium, aluminum and copper. Although it is known that these elements benefit the machinability of Type 416 stainless steel, they are also known to damage desirable properties such as corrosion resistance and processability when they are in very large quantities. The processability is related to the hot working capacity and the ease of melting the alloy. In addition, the inclusion of such elements in the composition of the basic alloy results in an alloy that is outside the industry accepted composition limits for the Type 416 alloy. Customers and potential customers for the Type 416 alloy are reluctant to buy such modified grades due to uncertainty about the effects of compositional modifications on the desired properties of Type 416 alloy in addition to machinability. U.S. Patent No. 3,401,035 relates to an easy machining stainless steel based on Type 416 alloy. That patent discloses that increasing the chromium equivalent, and consequently the amount of ferrite, in the alloy is beneficial to the machinability of Type 416 alloy drilling. However, the presence of too much ferrite in a Marcensitic stainless steel such as Type 416 adversely affects the hardness capacity of the alloy, so that high levels of hardness and strength Typically specified for that steel are not achievable. The patent indicates that "the principles of the invention" described herein "are equally applicable to steels having a duplex or ferrite-free microstructure". However, there is no discussion of how the composition of such alloys should be balanced to provide a significant improvement in machinability in a profiling tool. In view of the foregoing, there is a need for a martensitic stainless steel alloy which provides better machinability in a tool for profiling relative to known grades, but which provides at least the same level of hardness and corrosion resistance than those degrees.

Brief Description of the Invention The disadvantages associated with the known grades of Type 416 stainless steel alloy are solved to a greater degree by the alloy according to the present invention. The alloy of this invention is a martensitic stainless steel alloy having a unique combination of machinability and hardness. The open and preferred compositions of the present alloy in > 100 percent by weight, consist essentially of, approximately: Preferred Open Carbon 0.06-0.10 0.06-0.10 Open Preferred Manganese 0.50 max. 0.50 max.

Silicon 0.40 max. 0.35 max.

Phosphorous 0.060 max. 0.060 max.

Sulfur 0.15-0.55 0.15-0.50 Chrome 12.00-12.60 12-12.5 Nickel 0.25 max. 0.20 max.

Molybdenum 0.10 max. 0.10 max.

Copper 0.50 max. 0.50 max.

Nitrogen 0.04 max. 0.04 max.

The rest of the alloy is essentially iron and the usual impurities. The alloy is further characterized because it has a very low amount of ferrite under the tempered and annealed conditions. Up to that point the amounts of silicon and chromium present in this alloy are significantly lower than in known commercial grades. The alloy according to this invention provides a machinability in a significantly improved profiling machine with a hardness capacity that is at least as good as that of the known grades of Type 416 alloy. The above tabulation is provided as a convenient summary. and it is not therefore intended to restrict the upper and lower values of the ranges of the individual elements of the alloy of this invention to be used in combination with each other, to restrict the ranges of the elements to be used only in combination with each other. In this way, one or more of the intervals can be used with one or more of the other intervals for the remaining elements. In addition, a minimum or maximum of one element of a preferred embodiment may be used with the minimum or maximum for that element of another preferred embodiment. Through this application, the term "percent" or the symbol "%" means percent by weight, unless otherwise indicated.

Detailed Description The alloy according to the present invention contains a combined amount of carbon and nitrogen to provide a hardness capacity of at least about 35 HRC when the alloy is heated to about 1825 ° F (996.1 ° C) for 30 minutes and then it is cooled with air. To provide the desired hardness, the alloy contains at least about 0.10% carbon + nitrogen. The presence of too much carbon and nitrogen in this alloy adversely affects the machinability of the alloy, however. Therefore, the combined amount of carbon and nitrogen is restricted to no more than about 0.14%. Individually, from about 0.06 to 0.10% carbon and trace amounts up to about 0.04% nitrogen are present in this alloy. Within the ranges mentioned above, the amount of nitrogen present in the alloy depends on the amount of carbon that is selected. Manganese is inevitably present in the alloy of this invention, at least residual levels. Manganese is preferably restricted to no more than about 0.50% to ensure that the alloy provides the desired level of corrosion resistance, in particular, substantially free of corrosive attacks during passivation. Silicon is also inevitably present in this alloy in retained amounts of the additions made to deoxidize the alloy during the melting / refining process. However, because silicon promotes the formation of ferrite, its use is restricted so that the amount retained is not more than about 0.40%, and preferably not more than about 0.35%. Chromium contributes to the good corrosion resistance of this alloy and, therefore, at least about 12.0% chromium is present in it. Chromium also promotes the formation of ferrite in this alloy. Therefore, to limit the amount of ferrite present in the alloy, the chromium is restricted to no more than about 12.60% and better still no more than about 12.50%. Sulfur is present in this alloy because it combines with available manganese and chromium to form sulfides that benefit the machinability of the alloy. In this regard, at least about 0.15%, even better at least about 0.20%, and preferably at least about 0.30% sulfur in this alloy is present. Too much sulfur, however, adversely affects the working capacity of the alloy, its resistance to corrosion, and its mechanical properties such as ductility. For that reason the sulfur is restricted to no more than about 0.55% and better still no more than about 0.50% in this alloy. Preferably, this alloy contains about 0.30-0.40% sulfur.

Other elements in this alloy may be present as retained amounts of additions made to the melt for a specific purpose or that were accidentally added through the fillers used during the melting of the alloy. However, the amounts of such elements are controlled so that the machinability, corrosion resistance, and hardness of the alloy are not adversely affected. More particularly, nickel and copper are restricted in this alloy because too much of those elements, either alone or in combination, will result in an undesirably high annealed hardness. In that regard, the nickel is restricted to no more than about 0.25% and preferably no more than about 0.20%. The copper is restricted to no more than about 0.50%, and preferably to no more than about 0.25%. Molybdenum is restricted to no more than about 0.10%, because like chrome, molybdenum promotes the formation of ferrite in this alloy. Up to about 0.1%, but preferably not more than about 0.05%, of selenium may be present in this alloy because of its beneficial effect on machinability as an element that controls the formation of sulfur. Up to approximately 0.01% calcium may be present in this alloy to promote the formation of calcium and aluminum silicates, which benefit the machinability of the alloy with carbide cutting tools. A small but effective amount of boron of about 0.0005-0.01% may be present in this alloy because of its beneficial effect on hot working capacity. The rest of the alloy is essentially iron, except for the usual impurities found in similar grades of commercially available martensitic stainless steels. The amounts of such impurities are controlled so that the basic properties of machinability, corrosion resistance and hardness capacity are not adversely affected. For example, phosphorus is considered to be an impurity in this alloy, which adversely affects the machinability of the alloy and, therefore, is restricted to no more than about 0.060%, preferably not more than about 0.030. %. Very small amounts of cobalt, approximately 0.10% or less, and vanadium, 0.08% or less, may be present in this alloy, without adversely affecting the desired combination of properties. In addition, elements such as titanium and zirconium are varied to no more than about 0.02%, preferably no more than about 0.01% to control the amount of Ti and Zr carbonitrides in the alloy, because such phases adversely affect the machinability of this alloy. Similarly, aluminum is restricted to no more than about 0.02%, preferably no more than about 0.01% to control the amount of aluminum oxide in the alloy, which also adversely affects the machinability of this alloy . Within the weight percent ranges described hereinabove, the elements are carefully balanced to control the amount of ferrite in the alloy, but without adversely affecting the hardness or corrosion resistance capacity provided by the alloy. It has been found by the inventor that the machinability in a profiling tool provided by this alloy is substantially improved when the amount of ferrite present is restricted to significantly lower levels than those usually found in the known grades of the Type 416 alloy. Up to that point the composition of the alloy is balanced so that the amounts of ferrite forming elements such as chromium and silicon present in the alloy are significantly lower than in the known commercial grades of the Type 416 alloy. Since the amount Ferrite in the alloy is directly related to the amount of ferrite forming elements present, the relative level of ferrite can be determined with reference to an equivalent chromium factor. An equivalent of suitable chromium is that defined in U.S. Patent No. 3,401,035 as: Chromium Equivalent in% =% Cr +% Si + 1.5x% Mo + 10x% Al -% NI -% Cu - 30 (% C +% N) Preferably, the% Chromium Equivalent in the alloy according to the present invention is not greater than about 9.5%, better still, not greater than about 9.0%, and preferably not greater than about 8.75%, according to to what is determined by the previous formula. No special technique is required in the melting, casting, or working of the alloy of the present invention. Arc fusion followed by decarburization with argon-oxygen (AOD) is the preferred method for melting and refining the alloy. However, other practices such as vacuum induction melting (VIM) can be used. This alloy is suitable for use in continuous casting processes and, when desired, can be produced by powder metallurgical technique. The alloy according to the present invention is hot worked from an oven temperature of about 2000-2300F (1093-1260C), preferably 2100-2250F (1149-1232C), reheating as necessary after intermediate reductions. The alloy is hardened by austerizing at about 1800-1900F (982-1038C), preferably tempering in oil, and then tempering or annealing for about 2-8 hours, preferably about 4 hours, at an oven temperature of about 300-1450F (149-788C). The alloy is preferably cooled with air from the tempering or annealing temperature. As with Type 416 stainless steel, the present alloy can be heat treated to a variety of desired hardnesses, such as 100 HRB max., 26-32 HRC or 32-38 HRC. The improved machinability provided by this alloy is more pronounced in the annealed condition (100 HRB max.) And when the alloy has been hardened to an intermediate level of hardness (26-32 HRC).

The alloy of the present invention can be formed in a variety of forms for a wide variety of uses and is itself adapted for the formation of billets, billets, rods, wires, straps, plates, or sheets using conventional practices. The preferred practice is to continuously melt the alloy in the form of billets or billets followed by hot rolling of the billet or billet to a bar or ingot, wire, or strip. Such shapes are then easily machined into useful components.

Working Examples To demonstrate the unique combination of properties provided by the present alloy, Example 1 thereof was prepared having the composition in weight percent shown in Table 1. For comparison purposes, tests A and B are comparative with compositions outside the range of the present invention, but which are typical of the commercial grade of Type 416 alloy. The weight percent compositions of Tests A and B are also shown in Table 1.

Table 1 Element Example 1 Test A Test B C 0.093 0.095 0.084 Mn 0.41 0.40 0.40 Si 0.23 0.70 0.68 P 0.017 0.016 0.021 s 0.35 0.34 0.37 Cr 12.36 13.10 13.02 Ni 0.24 0.22 0.31 Mo 0.01 0.01 0.06 Cu 0.04 0.04 0.05 Co 0.02 0.02 0.03 V 0.065 0.072 0.08 N 0.030 0.032 0.034 Ti < 0.005 < 0.005 < 0.005 Cb < 0.01 < 0.01 < 0.01 W < 0.02 < 0.02 < 0.02 Zr < 0.005 < 0.005 < 0.005 Fe The rest The rest The rest Example 1, Assay A and Assay B were prepared as commercial size assays and were cast in high and refined using the AOD process.

The maximum hardened hardness of Example 1, 38 HRC, was determined from a sample as a molten material that was hardened by heating to 1825 F (996.1 C) for 30 minutes and then cooled with air. The maximum hardened hardness of Tests A and B, 38 HRC and 37.5 HRC respectively, were determined from a mathematical model based on the composition of the alloy. The three tests were each melted in a continuous caster to form 10 inch x 8 inch billets. The billets or billets of Example 1 and Test A were subdivided into several different portions. Each portion was processed differently, so that the machinability of the two alloys could be tested in more than one size and more than one hardness. More specifically, a portion of the billet or billet of Example 1 and a portion of the billet or billet of Test A were laminated to a 0.6875 inch (1.75 cm) round bar or bar at an oven temperature of 2250 F ( 1232.2 C). The bar or ingot was annealed in batches at 700 ° C for 8 hours and then cooled in air. The bar or annealed ingot of each test was then straightened and cut into lengths which were then turned and polished to a roundness of 0.625 inches (1.6 cm). That process, the Al process, was designed to provide an annealed hardness no greater than 100 HRB (Condition A).

The billet or billet continuously fused from test B was hot rolled to a roundness of 0.656 inches (1.67 cm). The hot rolled material was annealed at 780 C for 8 hours and then cooled with air. The bar or annealed ingot was then cut into lengths which were straightened, turned and polished to a roundness of 0.625 inches (1.6 cm). A second portion of the test of Example 1 was processed to a bar or ingot with a roundness of 0.625 inches (1.6 cm) as described above, except that it was annealed at 780C for 8 hours and then cooled with air. The process of annealing at 780 ° C, the A2 process was also designed to provide an annealed hardness no greater than about 100 HRB. Another portion of the continuously cast billet or billet from Example 1 and a portion of the continuously cast billet or billet from Test A were hot rolled to a 0.781 inch (1.98 cm) round bar or bar of a furnace at a temperature of 2250. ° F (1231.2 ° C). The bars or ingots were annealed in batches of 680 ° C to 700 ° C for 8 hours and then cooled with air. The bar or annealed ingot of each test was deamped to a roundness of 0.7512 inches (1.91 cm), heated to an austenitization temperature of 1000 ° C for 0.5 hours and then the oil was tempered. The bars or ingots thus tempered were then tempered at 560 ° C for 4 hours and cooled with air. The tempered bars or ingots were cold drawn to a roundness of 0.632 inches (1.61 cm), straightened, cut into lengths and then attached or ground to a roundness of 0.625 inches (1.6 cm). That process identified as TI, was designed to provide a Rockwell hardness of approximately 26 to 32 HRC (Condition T). A further portion of the continuously cast billet or billet of Example 1 and a further portion of the continuously cast billet or billet of test A were hot rolled to a 1.0625 inch (2.7 cm) round bar or ingot of a furnace temperature. 2250 ° F (1232.2 ° C) and then cooled in the oven. The bar or billet of each test was then heated to an austenitization temperature of 1000 ° C for 1 hour and cooled in oil. The bars or ingots thus tempered were then tempered at 550 ° C for 4 hours and cooled with air. The bars or ingots thus tempered straightened, turned to a roundness of 10,017 inches (2.58 cm), were re-leveled, and then polished or rectified to a roundness of 1.00 inches (2.54 cm). That process, identified as T2, was also designed to provide a Rockwell hardness of approximately 26 to 32 HRC. Additional additional portions of billets or billets of Example 1 and Test A were hot rolled to a 0.6875 inch (1.75 cm) round bar or bar. The bar or ingot of each test was then heated to an austenitization temperature of 1000 C for 1 hour and then warmed up in oil. The bars thus hardened were then tempered at 510 C for 4 hours and cooled with air. However, the tempered hardness was greater than the desired range and thus the bars or ingots were reatemperated at 520 C for 4 hours and cooled with air. The bars or ingots thus tempered were straightened, turned, to a roundness of 0.637 inches (1.62 cm). That process, identified as Hl, was designed to provide a Rockwell hardness of approximately 32 to 38 HRC (Condition H). The hardness of the bars or ingots processed in this way was measured in the center, in the middle part of the radius, and near the edge thereof. The results of the hardness test are presented in Table 2 as the hardness of the average cross section.

Table 2 Average Hardness Process Condition A Ex. 1 To 96 In. A 98 Ex. 1 A2 92 En. B 86 Condition T Ex. 1 TI 27 In. A 28 Ex. 1 T2 28 En. A 28 Condition H Ex. 1 Hl 32 En. A 32 Hardness values of 80 to 100 are in the Rockwell B Scale (HRB). Hardness values of 20 to 35 are on the Rockwell C Scale (HRC). Table 3 shows the results of the machinability test of test specimens of each composition on an automatic screw machine. This test was designed to show the machinability of a tool to profile an alloy measured by the life of the cutting tool. Machinability tests were performed in triplicate on specimens of bars or ingots of 0.625 inches (1.6 cm) and 1,000 inches (2.54 cm) using a procedure based on the standard test procedure ASTM E618. An approximate tailored shaping tool fed at 0: ~ 002 ipr (0.051 mm / rev) and the water-based shear fluid emulsion at a concentration of 5% was used. A machining speed of 343 surface feet per minute (SFPM) (104.5 m / min) was used for heat-treated specimens up to Condition A. For heat-treated specimens up to condition T, a machining speed was used 257 SFPM (78.3 m / min) for specimens taken from bars or ingots of 0.625 inches (1.6 cm) and a machining speed of 256 SFPM (78.0 m / min) was used for specimens taken from 1,000-inch bars or ingots (2.54 cm). A machining speed of 206 SFPM (62.8 m / min) was used for the specimens heat treated to Condition H. The results are reported as the number of machined parts (Machined Parts) before the approximate diameter of the parts formed machined will grow to 0.003 inches (0.076 mm), unless otherwise indicated in the table. The results reported in Tables 3A to 3D were obtained using standard profiling tools.

Table 3A Bar or ingot of 0.625 inches (1.6 cm) in Condition A # Alloy Process Machined Parts Average Des. Its T.

Ex. 1 Al 4301, 4201,4101 420 10 In. To Al 3101, 2301, 2101 250 53 2501, 2001, 2601 237 32 E A2 3901, 4901, 5201 467 68 480, 460, 510 483 25 In. B A2 2101, 1901, 2701 223 42 1The tool failed before the part grew by 0.003 inches (0.076 mm).

Table 3 0.625 inch (1.6 cm) bar or ingot in Condition T Alloy Process Middle Parts Des. Est, Machined Ex. 1 TI 5701, 4501, 5501 523 64 In. A TI 2801, 3701, 3501 333 47 • "" The tool failed before the part grew by 0.003 inches (0.076 mm).

Table 3 C Bar or ingot of 1,000 inches (2.54 cm) in Condition T Alloy Process Middle Parts Des. Est. Machined Ex. 1 T2 3401, 2901, 2701 300 36 In. A T2 2101, 1901, 2201 207 15 1The tool failed before the part grew by 0.003 inches (0.076 mm).

Table 3D Bar or round bar of 0.625 inches (1.6 cm) in Condition H Alloy Process Middle Parts Des. Est, Machined Ex. 1 Hl 4301, 2801, 3501 353 75 In. A Hl 3201, 2501, 2301 267 47 xThe tool failed before the part grew by 0.003 inches (0.076 mm).

Table 4A 0.625-inch (1.6 cm) bar or ingot in Condition A Alloy Process Middle Parts Des. Est, Machined Ex. 1 To 490, 480, 540 503 32 In. A Al 1901, 2101, 3501 250 87 2701, 1701, 1701 203 58 1The tool failed before the part grew by 0.003 inches (0.076 mm).

Table 4B 0.625 inch (1.6 cm) bar or ingot in Condition T Alloy Process Middle Parts Des. Est. Machined Ex. 1 TI 6401, 6401, 6701, 650 17 In. A TI 5101, 6101, 5501 557 50 The tool failed before the part grew by .003 inches (0.076 mm).

Table 4C Bar or ingot of 1,000 inches (2.54 cm) in Condition H Alloy Process Middle Parts Des. Est. Machined Ex. 1 Hl 3401, 2701, 2501 287 47 In. A Hl 3201, 3101, 3501 327 21 1The tool failed before the part grew by 0.003 inches (0.076 mm). Cone-shaped specimens were prepared for the corrosion test of the 0.625 inch (1.6 cm) bars or ingots of Example 1 and Test A. the cone-shaped specimens have a vertex with an angle of 60 ° and were polished to a value of 600 degree. Triplicate assemblies of some of their conical specimens were passivated by immersing them in a 5% by weight solution of sodium hydroxide at 160-180 ° F (71-82 ° C) for 30 minutes and then rinsed in water. The conical specimens were then immersed in a 20% by volume solution of nitric acid (HN03) containing sodium dichromate at 120-140 ° F (49-60 ° C) for 30 minutes and rinsed in water again. Finally, the conical specimens were again immersed in a 5% by weight solution of sodium hydroxide at 160-180 ° F (71-82 ° C) for 30 minutes and then rinsed in water. The remaining conical specimens were not passivated. All specimens were tested by exposure to a controlled environment that had a relative humidity of 95% at 95 ° F (35 ° C) for 200 hours and then inspected for the presence of corrosion. Shown in Table 5A below are the results of the corrosion test of the passivated tapered specimens of each test, including the heat treatment process used (Process) and a qualitative evaluation of the degree of corrosion (Test Results) that the specimens from each set they experienced. Table 5B shows the results for non-passivated specimens.

Table 5A. { Passivated } I .D. Process Test Results Ex. 1 Al Several small areas of oxidation.

In. A Al Several small areas of oxidation.

Ex. 1 TI Several small areas of oxidation; bites in a sample.

Table 5A (continued). { Passivated } I .D. Process Test Results In . TO IT Several small areas of oxidation; bites in a sample.

Table 5A. { Not passivated } I, D Process Test Results Ex. 1 Al Several small areas of oxidation; bites in a sample.

In. A Al Several small areas of oxidation.

Ex. 1 TI Several small areas of oxidation; bites in a sample.

In. TO IT Several small areas of: oxidation; bites in a sample.

The data presented in Tables 3A to 4C show that Example 1 of the present alloy provides a machinability in an upper profiling machine in relation to Tests A and B in the annealed condition and in relation to Test A in the intermediate hardened condition (26-32 HRC). This significant improvement in machinability is obtained without sacrificing the hardness capacity because, as noted above, Example 1 provided a hardened hardness of 38 HRC using a known hardening and quenching heat treatment. In addition, the data in Tables 5A and 5B show that Example 1 has a corrosion resistance that is essentially the same as that of Test A. Thus, the improvement in machinability in a profiling machine provided by the present invention was obtained without sacrificing corrosion resistance. The terms and expressions that have been used were used as descriptive terms and not limiting. There is no intent to use such terms and expressions to exclude any equivalents of the features shown and described or portions thereof. It should be recognized, however, that various modifications are possible within the scope of the claimed invention. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Claims (5)

1. EIVINDICATIONS Having described the invention as above, the content of the following claims is claimed as property: 1. An alloy of martensitic stainless steel having a unique combination of machinability in a profiling tool, hardness capacity, and corrosion resistance, the alloy is characterized in that it consists essentially of,, in percent by weight, approximately: % in weigh Carbon 0.06-0.10 Manganese 0.50 max, Silicon 0.40 max, Phosphor 0.060 max Sulfur 0.15-0.55 Chrome 12.00-12.60 Nickel 0.25 max. Molybdenum 0.10 max. Copper 0.50 max,% by weight Nitrogen 0.04 max. and the rest is essentially iron.
2. 2. The alloy according to claim 1, characterized in that it contains no more than about 0.35% silicon.
3. 3. The alloy according to claim 1, characterized in that it contains no more than about 0.20% nickel. .
4. The alloy according to claim 1, characterized in that it contains no more than about 12.50% chromium.
5. 5. An alloy of martensitic stainless steel having a unique combination of machinability in a pari-profiling tool, hardness capacity, and corrosion resistance, the alloy is characterized in that it consists essentially of, in percent by weight, approximately: % in weigh Carbon 0.06-0.10 Manganese 0.50 max. Silicon 0.35 max. % in weigh Phosphorous 0.060 max. Sulfur 0.15-0.55 Chrome 12.00-12.50 Nickel 0.20 max. Molybdenum 0.10 max. Copper 0.50 max. Nitrogen 0.04 max. This is essentially iron.