Carburized Case Research Articles

Effect of parameters of the carburized case on the properties of steel 20Kh3MVFA

1. To ensure the highest contact fatigue strength and fatigue limit the carbon concentration in the carburized case on steel 20Kh3MVFA must be higher than for steel 12Kh2N4A-1.3–1.5% as compared with 1.0–1.2%. 2. The contact fatigue strength of steel 20Kh3MVFA is ∼30% higher than that of steel 12Kh2N4A, which is explained by the larger quantity of carbides and the higher concentration of carbon in the solid solution. 3. The highest contact fatigue strength and fatigue limit of steel 20Kh3MVFA are obtained after quenching from carburizing temperature due to the larger quantity of carbon in the solid solution and its higher concentration of chromium and molybdenum. 4. Retained austenite cannot be permitted in the carburized case of highly stressed machine parts. The optimal structure is finely dispersed martensite and fine globular carbides to a depth of 0.15–0.25 mm (after grinding 0.2 mm on each side).

A New Carburizing Steel with Improved Hot Hardness and Temper Resistance

AbstractCase-hardened parts made from carburizing alloys exhibit a comparatively soft tough core and a hard, wear-resistant case. A drawback of the majority of carburizing alloys is their lack of temper resistance and hot hardness of the carburized case. Several carburizing alloys are available which have good hot hardness. Unfortunately, their enhanced hot hardness is at the expense of toughness.Currently, AISI 9310 is used for many critical helicopter gear applications. Because this steel lacks hot hardness adequate for new helicopter transmission applications, a new alloy was developed.A new carburizing alloy, designated EX00014, previously developed by CarTech and having good toughness, was selected as the starting point.An initial investigation on modifications of EX00014 indicated that Si, Cu and V were near the optimum level for the best impact, tensile and hardness properties. Lowering the Ni from 3.0% to 2.0% indicated an improvement in impact strength. Increasing the Mo to as high as 2.5% improv...

ALLOY STEEL 8124

Abstract Alloy Steel 8124 (Nonstandard, using AISI-SAE numbering system) is a nickel-chromium-molybdenum carburizing steel for use where a core of medium strength and toughness combined with a wear-resistant carburized case is sufficient. This steel can be used also without carburizing for many machinery components and structural purposes. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-326. Producer or source: Alloy steel mills and foundries.

Effect of chromium on the depth and properties of the carburized case on low-carbon steel

1. The conditions for carburizing and subsequent heat treatment to obtain the highest wear resistance must be selected by means of mathematically planned experiments for each steel. 2. As the result of optimization, the wear resistance of the carburized steels increased 20–40% as compared with the best results obtained by the traditional single-factor method. 3. Chromium lowers the carburizing rate, although the wear resistance of high-chromium steels is higher. Raising the chromium content of the steel from 3- to 13–17% increases the wear resistance 50–100% after carburizing + quenching and low-temperature tempering.

Change in the dimensions of gear wheels during gas carburizing and quenching

1. It was found that the structural characteristics of the carburized case have different effects on deformation of the outer and inner surfaces of parts. 2. The diameter of the hole (y2), unlike the diameter of the circumferential circular pitch (y5), is related to changes in several parameters of the carburized case, the most important being the concentration of carbon in martensite and in retained austenite. To increase the accuracy of the diameter of the hole in quenched gear wheols made of Cr-Ni steel we recommend slow cooling after gas carburizing, either in the furnace or in a closed pit. In view of the substantial effect of the carbon concentration in the case on the deformation of the gear wheel, strict control of the carbon content and exact compliance with the quenching regime are necessary. 3. Structural stresses in the case evidently have little effect on the total stresses that occur during cooling. This is confirmed by the absence of any significant correlation between warping of the part (parameters y1, y4, and y6) and the factorial parameters characterizing the bulk deformation of the case. 4. Multifactoral correlation and regression analysis are fully suited to calculate the effect of changes in the structural characteristics of the case on the accuracy of the dimensions of gear wheels. The practical importance of regression models and adequate experiment data is that by means of x-day analysis of the case one can predict approximately the change in the dimensions during quenching of carburized parts. The regression model can be used for quality control of parts for which chemicothermal treatment is the final operation.

AISI 4820

Abstract AISI 4820 is a low-carbon carburizing steel containing nominally 3.5% nickel and 0.25% molybdenum. It is ideal for uses that require a strong, tough core along with a highly wear-resistant carburized case. In addition, it offers a good combination of strength and low-temperature toughness for non-carburized applications. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SA-311. Producer or source: Alloy steel mills and foundries.

AISI 5120

Abstract AISI 5120 is a low-carbon, low-chromium carburizing steel recommended for applications where a core of medium strength and toughness combined with a wear-resistant carburized case is sufficient. It has medium hardenability and can be used without carburizing. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-294. Producer or source: Alloy steel mills and foundries.

SAE 8115

Abstract SAE 8115 is a low-carbon nickel-chromium-molybdenum carburizing steel recommended for applications where a core of medium strength and toughness combined with a wear-resistant carburized case is sufficient. It has medium hardenability and can be used without carburizing. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-292. Producer or source: Alloy steel mills and foundries.

AISI 4718

Abstract AISI 4718 is a low-carbon nickel-chromium-molybdenum carburizing steel recommended for applications requiring a strong, tough core combined with a highly wear-resistant carburized case. It has fairly high hardenability and can be used without carburizing. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-289. Producer or source: Alloy steel mills and foundries.

AISI 8822

Abstract AISI 8822 is a nickel-chromium-molybdenum carburizing steel of fairly high hardenability. Its high core strength and durable carburized case make it suitable for many heavy-duty applications. It can also be used without carburizing. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on low and high temperature performance, and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-288. Producer or source: Alloy steel mills and foundries.

Retained austenite and hardness of the carburized case on steel 18Kh2N4VA after quenching in two different media

1. The distribution of retained austenite in the case on quenched steel 18Kh2N4VA is independent of the quenching medium. The amount of retained austenite in the case is largest at a depth of 0.2–0.4 mm. 2. The change in the hardness through the depth of the case, in complete agreement with the carbon distribution, does not reflect the entire relationship between the amount of retained austenite in steel 18Kh2N4VA.

Effect of quenching in a fluidized bed on the structure and mechanical properties of carburized steel 18Kh2N4VA

1. The structural components of the carburized case and the core are finer after quenching in a fluidized bed than after quenching in oil. 2. The hardness of carburized samples is 1–2 HRC units higher after quenching in a fluidized bed than after quenching in oil. The hardness of the cores is the same after quenching in both media (HRC 38-40). 3. The ultimate tensile strength, elongation, reduction in cross sectional area, and toughness are higher after quenching in a fluidized bed than after quenching in oil. 4. A fluidized bed can be used for quenching carburized parts of steels 18Kh2N4VA and 20Kh2N4A.

AISI 4815

Abstract AISI 4815 is a low-carbon, nickel-molybdenum carburizing steel. It is recommended for applications requiring a strong, tough core combined with a highly wear-resistant carburized case. It also offers a good combination of strength and low-temperature toughness for non-carburizing applications. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on low temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SA-259. Producer or source: Alloy steel mills and foundries.

DURAMOLD-N

Abstract DURAMOLD N is a low-carbon, nickel-chromium type of plastic-molding die steel capable of developing a deep carburized case combined with exceptional core strength. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on forming, heat treating, machining, and joining. Filing Code: TS-221. Producer or source: Bethlehem Steel Corporation.

Cracking in the carburized case of gears during their grinding

Cracking in the carburized case of gears during their grinding

THE EFFECT OF MINOR ADDITIONS OF SULPHUR ON PORE CLOSURE AND CASE-HARDENABILITY OF SINTERED IRON

It is well known that sintered iron structural parts, especially in the low- and medium-density range (i.e., approx. 6.4–6.8 g/cc), often behave trickily during gas- or pack-carburizing treatment. This is mainly due to the fact that the carburizing gases, via interconnected pores, can easily penetrate the sintered parts to a greater depth. If the density of sintered iron parts is less than ~7.0 g/cc, the carburizing action is usually so fast that it becomes difficult to control case depth and to prevent carburization of the core. This can be especially inconvenient if larger charges are involved, or if a charge contains parts of varying size or density. Then, because time is too short to achieve an even temperature distribution throughout the whole charge, someparts may become through-carburized before others have developed a thin carburized case.

Carburizing with an oxy-acetylene flame

1. The feasibility of carburizing with an oxy-acetylene flame has been confirmed. 2. A carburized case of 0.8–1.0 mm can be obtained in 20 to 30 min. at 1050–1100°C by this method. 3. The effects of overheating caused by high temperature carburizing can be completely eliminated by subsequent normalizing. 4. Carburizing with an oxy-acetylene flame enables a) to shorten the duration of carburizing by a factor of 15 to 20 compared with ordinary carburizing at 920°C; b) to conduct selective carburizing; c) eliminate expensive and bulky equipment such as furnaces, induction heaters, etc., d) incorporate carburizing into the flow of mechanical processing; c) conduct carburizing at any machine repair shop.

Distribution of carbon in the carburized case of alloy steels

Distribution of carbon in the carburized case of alloy steels

鋼の滲炭層の殘留應力に就て

The residual stress of carburized case of armco iron and Si-Mn-Cr-Mo steel was measured by using Heyn's method. The result was as follows: In armco iron and Si-Mn-Cr-Mo steel having ordinary carburized case, high carbon part is under compression and low carbon part is under tension. And also, particular structure (analogous to Bainite) in carburized case of Si-Mn-Cr-Mo steel in under compression.

緩和滲炭に關する基礎的研究(第3報)

As described in the 1 st and 2 nd reports, when the carburizer with any suppressor is used, the promotive power decays according to the reaction between the suppresser and the promoter in the carhurizer. As the result of decaying, the carbon content in the surface layer of carhurized steel lowers with the proceeding of carburizing. It was calculated nn the stand point of Jaw of diffusion by applying the Duhamel theory in thermal conduction, how much this lowering offected the carbon distribution in carburized case, and found that the carbon distribution was not steeper and scarcely distinguished from that treated with the common mild-carburizer.