افزودن تیتانیم روی فولاد کم آلیاژ استحکام بالا Effect of Titanium Addition on HSLA Steel

Study on the Mechanism of Strengthening and Toughening Effect

 of Titanium Addition on HSLA Steel 

مطالعه‌ی مکانیزم استحکام‌بخشی و اثر چقرمه‌سازی افزودن تیتانیم روی فولاد HSLA

ABSTRACT

Based on the determination of load variation against deflection by means of Instrumented Charpy Impact testing, the impact energy distribution of the High Strength Low Alloy (HSLA) steel containing Nb, Ni and Ti for pressure vessels at low temperature has been quantitatively studied. The total impact energy Et could be divided into two parts, Ei  and Ep. Ei is related to the base strength of the material in terms of the grain size and alloy addition, which is also found to be less influenced by the holding time of normalization process at 910℃. Whereas, Ep of Ni-Nb-Ti HSLA steel is strongly linked to the period of holding time. Thermodynamic kinetic investigation was  carried out to study the strengthening mechanism with metallurgical microstructure analysis. 

 

بهبود یک فولاد میکروآلیاژی HSLA با وانادیم و تیتانیم

Effect of vanadium and titanium modification on the microstructure and

mechanical properties of a microalloyed HSLA steel

اثر بهبود یک‌نوع فولاد میکروآلیاژی HSLA با وانادیم و تیتانیم بر ریزساختار و خواص مکانیکی آن

ABSTRACT

Microalloyed high-strength low-alloy (HSLA) steels are essentially low carbon low-alloy steels that contain small additions (0.001–0.1wt.%) of alloying elements such as Nb, V, or Ti. These steels exhibit an outstanding combination of high strength, resistance to brittle fracture and good weldability, particularly if the carbon content is kept below ∼0.1wt.% . Several categories of HSLA steels have been developed catering to the needs of specific applications, such as the construction of large ships, oil and gas transmission lines, and offshore oil drilling platforms.

 

فولادهای میکروآلیاژی وانادیوم-نیوبیوم vanadium-niobium microalloyed steels

As-cast mechanical properties of vanadium/niobium microalloyed steels

خواص مکانیکی فولادهای میکروآلیاژی وانادیوم/نیوبیوم

ABSTRACT

Tensile and room temperature Charpy V-notch impact tests along with microstructural studies were used to evaluate the variations in the as-cast mechanical properties of low-carbon steels with and without vanadium and niobium. Tensile test results indicate that good combinations of strength and ductility can be achieved by microalloying additions. While the yield strength and UTS increase up to respectively 370–380 and 540–580 MPa in the microalloyed heats, their total elongation range from 20 to 25%. TEM studies revealed that random and interphase fine-scale microalloy precipitates play a major role in the strengthening of the microalloyed heats. On the other hand, microalloying additions significantly decreased the impact energy and led to the dominance of cleavage facets on the fracture surfaces. It seems that heterogeneous nucleation of microalloy carbonitrides on dislocations along with coarse ferrite grains and pearlite colonies trigger the brittle fracture in the microalloyed heats.

 

فولادهای زنگ نزن آستنیتی نیکل پایین Low Nickel Austenitic Stainless Steels

Low Nickel Austenitic Stainless Steels 

فولادهای  زنگ نزن آستنیتی نیکل پایین

ABSTRACT

The most common grades of stainless steel are 304 and 316, which are particularly popular because  their austenitic microstructure results in an excellent combination of corrosion resistance, mechanical  and physical properties and ease of fabrication.  The austenitic structure is the result of the addition of approximately 8-10% nickel. Nickel is not alone  in being an austenite former; other elements that are used in this way are manganese, nitrogen,  carbon and copper. 

 

نیتروژن دهی و آلیاژسازی سطح فولادها با اتم های Ti و Nb توسط عملیات تراکمی جریان های پلاسمایی

Surface nitriding and alloying of steels with Ti and Nb atoms

by compression plasma flows treatment

نیتروژن دهی و آلیاژسازی سطح فولادها با اتم های Ti و Nb توسط عملیات تراکمی جریان های پلاسمایی

ABSTRACT

Phase and element composition, microhardness of Ti/steel and Nb/steel systems treated by compression plasma flows have been investigated in this work. Auger electron spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersion X-ray microanalysis and Vickers microhardness measurements were used for sample characterization. The findings showed that treatment of a “coating/steel” system by compression plasma flows generated in nitrogen atmosphere allowed alloying of the surface layer of steel by the coating element and nitriding it simultaneously. The variation of the pulses number (1–6) resulted in change of the alloying element concentration and formation of a number of phases in the alloyed layer: Fe2Ti, a supersaturated solid solution α-Fe(Ti,C) in the Ti alloyed layer and a supersaturated solid solution α-Fe(Nb,C) in the Nb alloyed layer. The formation of Ti(C,N) and Nb(C,N) carbonitrides with fcc crystal structure at the surface was also found. The change of phase composition and quenching effects resulted in substantial increase of microhardness.

 

نیتروژن دهی پلاسمایی فولاد زنگ نزن نوع AISI 420

Effect of plasma nitriding on the strength of

fine protrusions formed by sputter etching of

AISI type 420 stainless steel

تاثیر نیتروژن دهی پلاسمایی بر استحکام برآمدگی های ریز تشکیل شده

از اچ کند و پاشی (sputter etching)  فولاد زنگ نزن نوع AISI 420

ABSTRACT

Argon ion sputter-etching of AISI type 420 martensitic stainless steel was carried out to form conical protrusions with bottom diameter of 10–30 μm on the specimen surface by using a radio-frequency magnetron sputter-apparatus. Plasma-nitriding was applied to the protrusions with various mixing rate of nitrogen and argon gas. The shape of the protrusions was examined by using a scanning electron microscope, and the nitrides formed on the protrusions were identified by means of an X-ray diffraction analysis. Micro-Vickers hardness tests and nano-scratch tests were used to evaluate the deformation resistance of the protrusions. By plasma-nitriding at a nitrogen pressure of 130 Pa and a nitriding power of 50 W, about 1.3 times larger indentation resistance than that of the as-sputter-etched protrusions was obtained after a long nitriding time of 14 ks. When plasma-nitriding was carried out at a lower nitrogen pressure of 1.2 Pa and a higher nitriding power of 200 W for 7.2 ks, indentation and scratch resistances of the protrusions largely increased to the values almost three times as large as those of the as-sputter-etched protrusions. However, the protrusions were brittle due to the formation of thick nitride layers and the sharpness of the protrusions was lost. Reduction of the nitriding power to 50 W recovered the sharpness with small amount of surface nitride layer, but the indentation resistances were only 1.4 times larger values than those of the as-sputter-etched protrusions. On the other hand, plasma-nitriding using a mixture of nitrogen gas of 0.53 Pa and argon gas of 0.67 Pa at the power of 50 W produced almost twice larger indentation and scratch resistances than those of the as-sputter-etched protrusions within a short nitriding time of 1.8 ks, retaining the sharpness of protrusions without forming brittle nitrided layers.

 

سینتیک استحاله های مارتنزیتی در فولادها

Kinetics of martensite transformations in steels

سینتیک استحاله های مارتنزیتی در فولادها

ABSTRACT

Dislocation theory of the mechanism and kinetics of martensitic transformation has provided a foundation for the prediction of constitutive relations for transformation plasiticity. Application to the control of stress-state dependent shaping of stress–strain behavior has demonstrated substantial improvements in uniform ductility and ductile fracture toughness. The advance of such predictive science continues to play a central role in the new enterprise of science-based materials design.

 

اتصالات بین فولاد زنگ نزن سوپر دو فازی و فولاد HSLA

Effect of heat input on microstructure and mechanical properties of

dissimilar joints between super duplex stainless steel and high strength low alloy steel

اثر حرارت ورودی بر ریزساختار و خواص مکانیکی اتصالات غیر مشابه بین

فولاد زنگ نزن سوپر دو فازی و فولاد کم آلیاژ با استحکام بالا

ABSTRACT

In the present study, microstructure and mechanical properties of UNS S32750 super duplex stainless steel (SDSS)/API X-65 high strength low alloy steel (HSLA) dissimilar joint were investigated. For this purpose, gas tungsten arc welding (GTAW) was used in two different heat inputs: 0.506 and 0.86 kJ/mm. The microstructures investigation with optical microscope, scanning electron microscope and X-ray diffraction showed that an increase in heat input led to a decrease in ferrite percentage, and that detrimental phases were not present. It also indicated that in heat affected zone of HSLA base metal in low heat input, bainite and ferrite phases were created; but in high heat input, perlite and ferrite phases were created. The results of impact tests revealed that the specimen with low heat input exhibited brittle fracture and that with high heat input had a higher strength than the base metals.

 

تاثیر فرایند تمپر بر ساختار و خواص مکانیکی فولاد HSLA-100

Influence of tempering on the microstructure and

mechanical properties of HSLA-100 steel plates

تاثیر فرایند تمپر بر ریزساختار و خواص مکانیکی صفحات فولادی HSLA-100

ABSTRACT

The influence of tempering on the microstructure and mechanical properties of HSLA-100 steel (with C-0.04, Mn-0.87, Cu-1.77, Cr-0.58, Mo-0.57, Ni-3.54, and Nb-.038 pct) has been studied. The plate samples were tempered from 300 °C to 700 °C for 1 hour after austenitizing and water quenching. The transmission electron microscopy (TEM) studies of the as-quenched steel revealed a predominantly lath martensite structure along with fine precipitates of Cu and Nb(C, N). A very small amount of retained austenite could be seen in the lath boundaries in the quenched condition. Profuse precipitation of Cu could be noticed on tempering at 450 °C, which enhanced the strength of the steel significantly (yield strength (YS)—1168 MPa, and ultimate tensile strength (UTS)—1219 MPa), though at the cost of its notch toughness, which dropped to 37 and 14 J at 25 °C and −85 °C, respectively. The precipitates became considerably coarsened and elongated on tempering at 650 °C, resulting in a phenomenal rise in impact toughness (Charpy V-notch (CVN) of 196 and 149 J, respectively, at 25 °C and −85 °C) at the expense of YS and UTS. The best combination of strength and toughness has been obtained on tempering at 600 °C for 1 hour (YS-1015 MPa and UTS-1068 MPa, with 88 J at −85 °C)

 

کدگذاری فولادهای آلیاژی

کدگذاری فولادهای آلیاژی

شرح : 

کدگذاری فولادهای آلیاژی : فولادها در گروه مختلف طبقه بندی شده و بر اساس کاربرد یا خواص فیزیکی و شیمیایی که از خود نشان می دهد دسته بندی می شود . ترکیبات فولاد در «موسسه آهن و فولاد آمریکا» AISI و انجمن مهندسین اتومبیل SAE تهیه شده است. آنها برای کدگذاری فولادهای آلیاژی و کربنی و همچنین تعیین محدوده ترکیبات شیمیایی از عددهای چهار رقمی استفاده کردند. فقط دو نوع از فولادهای آلیاژی پنج رقمی می باشند.  در کدگذاری فولادهای الیاژی و کربنی پسوند H نشان دهنده این است که فولاد با قابلیت سختی‌پذیری معینی ساخته می‌شود. حرف B در بین رقم‌های دوم و سوم فولادهای آلیاژی یا کربنی، مقدار بور فولاد از (0005/0 تا 003/0) را نشان می دهد و همین طور حرف L در بین رقم‌های دوم و سوم مقدار سرب فولاد را از (15٪ تا 35٪) نشان می‌دهد که این مقدار سرب قابلیت ماشین کاری فولاد را افزایش می‌دهد. در حال حاضر نزدیک به 10000 نوع فولاد مختلف در جهان تولید می شوند لذا شناسایی و طبقه بندی فولادها از اهمیت ویژه ای بر خوردار شده است . در این کتاب ، طبقه بندی بی نظیری از فولادهای آلیاژی و کدگذاری آن ها نگاشته شده است . با توجه که کتاب فارسی با این عنوان چاپ نگردیده ، این کتاب الکترونیک می تواند ابزار مفیدی برای صنعتگران فولاد و دانشجویان علاقمند به این رسته از علم متالورژی باشد .