Medium Alloy Steels Research Articles

Refining and Decarburizing Steel-Degassing Process in the Melting Practice of Alloy Steels

Reduction of the oxygen content of low to medium alloy steels by the C–O reaction under low pressure is discussed. Avoidance of disturbing reactions with the ladle refractory is accomplished by using basic lined teeming ladles with sliding stoppers. The exothermic vacuum refining of high chromium content alloyed steels is accomplished with gaseous oxygen. The importance of this new process should be considered when planning for the construction of steel plants in the future.

Sulfide Stress Corrosion of Some Medium and Low Alloy Steels

Abstract A study made of factors influencing sulfide-stress corrosion of a number of low alloy and medium alloy steels showed that their delayed failures when exposed simultaneously to stress and the corrosive action of acidified brine-hydrogen sulfide solutions have most of the features of hydrogen induced, delayed brittle failures. Different steels subjected to the same exposure conditions showed varying degrees of embrittlement as measured by ductility loss in bend tests. Ductility could be restored partially by room temperature storage. Ductility restoration was related to the amount of hydrogen removed after exposure. Delayed failure under stress occurs when corrosion generated hydrogen is absorbed, and lowers fracture strain until it equals the strain under load. A minimum applied stress was obtained for each steel below which failure did not occur. This “threshold” stress decreased as strength level increased and depended simultaneously on composition and microstructure. Nickel had little effect on cracking behavior of a steel whereas carbon appeared to be detrimental. Twinned martensite was more susceptible than untwinned martensite. Steels containing austenite were more resistant than body-centered steels.

AIR-4

Abstract BETHLEHEM AIR-4 is a medium alloy air-hardening tool steel having low deformation, high wear resistance and hardness, deep hardening properties and adequate toughness for severe service. It has excellent free-machining characteristics. This datasheet provides information on composition, physical properties, hardness, and elasticity. It also includes information on forming, heat treating, machining, and joining. Filing Code: TS-129. Producer or source: Bethlehem Steel Corporation.

Carbide Face Milling of Alloy Steel under Electric Resistance Heating

Surface finish and tool wear were observed and discussed when alloy steel (soft, medium and hard) was cut with carbide face milling cutter under electric resistance heating. When the soft and medium alloy steels were cut, surface finish became better with the increase of cutting temperature (the increase of current), but it became worse with further increasing of current beyond a certain value. Damage of tool was least when cutting conditions including electric current were so good that builtup edge was just disappeared, and with the increase of current, damage became more which was caused by repeated thermal stress, and further increase of current expedited the flank wear. When hard alloy steel (HRC 56) was cut, rake surface of tool was broken as a shell and the time of broken down was quick as the current was large. This damage is considered to occur by cracks which are subjected to the magnitude and number of times of repetition of thermal stree.

Theoretical premises for the use of an endo-gas atmosphere

1. A Co-H2-H2O type endo-gas atmosphere is reducing for carbon and for low- to medium-alloy steel; it is neutral for steels with various C contents. 2. An appropriate humidity of the endo-gas atmosphere is determined from the equilibrium diagram of the system CO-H2-H2O-C(γ-Fe), depending on temperature and the C content required in the surface layer of the steel. 3. The presence of methane in the endo-gas leads to a lower equilibrium water vapor content. An endo-gas atmosphere of CO-H2-H2O-CH4 type (with addition of methane) is a gaseous carburizing agent. Such an atmosphere, in combination with a CO-H2-H2O atmosphere, can be used in steel carburizing and allows automatic control of the carbon concentration in the surface layer of steel.

Non-Metallic Inclusions, Their Quantitative Extraction from Steel

An important factor in steel quality—non-metallic inclusions—can making practices. As a first step in effecting this control, the authors show that quantitative extraction and analysis of non-metallic inclusions in low- and medium-alloy steels is practicable.