Morphology and Crystallography Analyses of HSLA Steels with Hardenability Enhanced by Tailored C–Ni Collocation

High hardenability is of great importance to ultra-heavy steel plates and can be achieved by tailoring the composition of steel. In this study, the continuous cooling transformation (CCT) curves of two high-strength low-alloy (HSLA) steels (0.16C-0.92Ni steel and 0.12C-1.86Ni steel) were elucidated to reveal the significance of C–Ni collocation on hardenability from the perspective of morphology and crystallography. At a low cooling rate (0.5 °C/s), the 0.12C-1.86Ni steel showed higher microhardness than 0.16C-0.92Ni steel. The microstructure in 0.16C-0.92Ni steel was mainly granular bainite with block-shaped martensite/austenite islands (M/A islands), while that in 0.12C-1.86Ni steel was typically lath bainite with film-shaped M/A islands, denoting that the 0.12C-1.86Ni steel is of higher hardenability. Moreover, the 0.12C-1.86Ni steel exhibited a higher density of block boundaries, especially V1/V2 boundaries. The higher density of block boundaries resulted from the weakened variant selection due to the larger transformation driving force and more self-accommodation of transformation strain induced by the reduced carbon and increased nickel content.

Design and Analysis of Hot Forming Parts with Extra Thick Specification

The press hardening steel with thick specification has been used as automobile chassis parts. With the increase of the thickness, the cooling rate of the inner core is lower in the conventional process, resulting in a poor harden ability, and the fatigue test is not qualified. In this study, the microstructure of hot forming parts with thick specifications was studied by means of metallographic and micro-hardness testing. The results show that there is a microstructure gradient in the thick hot forming parts, which leads to the uneven strength in the cross section and finally affects the fatigue test results.The finite element analysis method is used to study the cooling rate of the inner core of the hot forming parts. The high hardenability press hardening steel products has been prepared by adjusting the components.

Isothermal Heat Treatment of the Low-Carbon Martensitic Steel

A study of the low-carbon steel with high hardenability was carried out. The steel contained the following alloying elements, wt. %: C – 0.20; Cr – 2.0; Mn – 2.0; Si – 1.04 Ni – 1.0; Mo – 0.3. The quenching – partitioning treatment of the studied steel was implemented. The microstructure of the steel consisted of the tempered martensite laths, bainite and martensite-austenite regions. The amount of the residual austenite and the carbon concentration in the residual austenite were estimated. The possibility of the quenching – partitioning treatment of the carburized steel was shown.

INDUSTEEL D2

Industeel D2 is an air-hardening, high-carbon (1.5%), high-chromium (12%), alloy cold-work tool steel that also contains molybdenum and vanadium. It is specifically designed to provide high abrasive wear resistance and high hardenability. This grade can be used for cutting and deformation tools submitted to high abrasive wear. It can be used when Type D3 tool steel shows an excessive sensitivity to cracking or chipping. This datasheet provides information on composition, physical properties, hardness, and elasticity. Filing Code: TS-791. Producer or source: Industeel France (a subsidiary of ArcelorMittal.

CHOICE OF TEMPERATURE AND TIME CONDITIONS OF HEATING FOR THE COMBINED PROCESS OF BORATING AND VOLUME TRAINING OF LARGE STAMPS OF 5KhNM STEEL

The stamps for hot deformation are widely adopted in industry. In use they are affected by high temperatures, tension (close to a fluidity limit) and variable thermal loadings. High-hardenability tool steels with high mechanical characteristics are used for stamps production. In this article, the possibility of use of 5KhNM steel for this goal is considered. One of technological operations at production of stamps is training in oil. It is rational to apply volume and superficial hardening, in particular chemical heat treatment, to improve operational characteristics of stamps, including wear resistance. The way of superficial hardening by the combined heating under chemical and thermal and heat treatment is presented. As a superficial way of hardening of largesize stamps of hot deformation, it is offered to use borating. Optimum temperature and time parameters of heating under the combined heat treatment are chosen and confirmed. The offered mode of chemical heat treatment allows receiving the necessary thickness of the borated layer providing high hardness and corrosion resistance in the working range of temperatures of a stamp. Also the influence of heat treatment on structure and grain size of the samples has been researched. It is shown that with increase in temperature and hold time, the size of grain increases. It leads to decrease in strength, fluidity, hardness and impact strength that can negatively influence operational properties of stamps. For definition of mechanical characteristics, the samples (in the studied range of temperatures and excerpts) have been tested for stretching and impact strength. All tests were carried out according to the existing state standard specifications. On the basis of these results, temperature and time of borating are chosen providing high mechanical properties and thickness of a borated layer. The offered approach has allowed reducing economic costs of stamps production from 5KhNM steel by exception from technological process of repeated heating for training with saving the required operational characteristics of largesize stamps.

Effect of boron microaddition on hardenability of new-developed HSLA-type steels

Purpose: The paper presents the results of investigations on the effect of 0.003% boron microaddition on the hardenability of new-developed HSLA-type steels. In order to prevent the binding of the boron microaddition with nitrogen in BN nitrides, Ti microaddition at concentrations of 0.033% and 0.028% was also added into the tested steels. Design/methodology/approach: Evaluation of hardenability of the investigated steels was carried out on the basis of the Jominy test and the analytical method, according to the ASTM 255-89 standard, taking into account the effect of the boron microaddition. Additionally, developed of the CCT-diagram of investigated steel. A DIL 805A/D dilatometer with a LVDT-type measuring head was used to carry out the dilatometric test. Findings: Microaddition of boron, introduced into steel in a concentration of 0.003% along with Ti microaddition shielding (in concentration of 0.033% in steel A and 0.028% in steel B), advantageously improves hardenability. This is reflected in calculated ideal critical diameter DIB, which is equal 163 mm for steel A and 155 mm for steel B. The form of curves of phase transformations of supercooled austenite is typical for steels with microaddition of boron, with similar chemical composition. Research limitations/implications: Due to similar chemical composition of investigated steels, the kinetics of phase transformations of austenite, supercooled under continuous cooling, was determined for steel B containing 0.28% C, 1.4% Mn, 0.3% Si, 0.26% Cr, 0.22% Mo and Nb, Ti, V and B microadditions at 0.027%, 0.028%, 0.019% and 0.003% respectively. Practical implications: Tested steels have high hardenability and show the full usability for production of forged parts with the method of thermomechanical treatment, i.e., hot- deformed in the temperature range adjusted to the type of microadditions added to steel, with direct quenching of forgings from finishing forging temperature. The results of the tests may be useful for developing the parameters of heat treatment and thermomechanical treatment of investigated steels. Originality/value: The hardenability of new-developed HSLA-type steels was determined.

CRYODUR 2767

Cryodur 2767 is a good choice for high hardenability and polishing application needs. This datasheet provides information on composition and physical properties. It also includes information on heat treating. Filing Code: TS-764. Producer or source: Schmolz + Bickenbach USA Inc..

Manufacturing technologies of steel seamless tubes for production of hard-to-recover hydrocarbons

The review contains main directions in the development of modern steelmaking, hot rolling technologies and heat treatment aimed to follow increased requirements to seamless tubes for production of oil and gas under severe conditions. New targets of PJSC “Gazprom” in development of new resources have determined new technical requirements to pipes for low temperature application, resistant to hydrogen sulfide and carbon dioxide corrosion. Basic metal science approaches are given to develop new chemical compositions of high quality steels containing minimum of sulfur, phosphorous and solute gases. Corresponding heat treatment routes are determined for formation of martensitic microstructure in full wall section during quenching with subsequent high tempering for required combination of high strength and ductility. It was shown that optimal combination of high strength and toughness at 60 °C below zero can be achieved by alloying of chromium-molybdenum steel containing about 0.25 wt. % of carbon with strong carbon forming elements such as vanadium and niobium. Sustainability of these steels to stress sulfide cracking was achieved through grain refinement with microalloying by molybdenum in concentrations corresponding to strength grades that gives high hardenability and retards tempering of martensite. New compositions of corrosion resistant martensitic 13 % chromium steel were carried out that was resulted in required resistance to carbon dioxide environments with improved low temperature toughness and high strength. The authors present results of reconstruction of steel making and hot rolling production lines at JSC “Volzhskii Pipe Plant” providing the required quality of new products from continuously cast steel billets to finished tubes.