RU2784363C1 - Steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to ferrous metallurgy, namely, to non-magnetic high-strength steels, and can be used in the gas and petroleum industry. Steel contains carbon, silicon, manganese, phosphorus, sulphur, chromium, molybdenum, nickel, nitrogen, aluminium, copper, cobalt, vanadium, calcium, strontium, barium, niobium, and iron at the following ratio of components, wt.%: carbon up to 0.05, silicon up to 0.3, manganese 18.0 to 20.0, phosphorus up to 0.03, sulphur up to 0.005, chromium 15.5 to 17.5, molybdenum 2.4 to 2.8, nickel 4.2 to 5.0, nitrogen 0.4 to 0.5, aluminium up to 0.3, copper up to 0.7, cobalt up to 0.03, calcium 0.003 to 0.01, strontium 0.001 to 0.01, barium 0.001 to 0.01, niobium 0.01 to 0.05, vanadium 0.01 to 0.05, iron the rest.

EFFECT: steel has the required high level of strength characteristics with associated preservation of plasticity.

1 cl, 1 dwg, 2 tbl

Description

The invention relates to ferrous metallurgy, in particular to high-strength non-magnetic steels, and can be used in the gas and oil industry.

Known steel containing carbon, silicon, manganese, phosphorus, sulfur, chromium, Nickel, nitrogen, calcium and iron, while the total ratio of components is, wt.%:

Carbon up to 0.2 Silicon 0.1 - 2.0 Manganese 9.0 - 35.0 Aluminum 0.001 - 0.200 Chromium 10.0 - 20.0 Nickel 0.1 - 8.0 Nitrogen 0.001 - 0.500 Calcium 0.001 - 0.020 Iron rest

[JPS61170545, Publication date: 08/01/1986 IPC: C22C 38/00; C22C 38/58].

The disadvantage of the known technical solution is the low strength characteristics of steel, in particular mechanical properties, such as tensile strength and yield strength, due to the increased size and a large number of non-metallic inclusions in the steel composition.

Steel containing carbon, silicon, manganese, phosphorus, sulfur, copper, nickel, chromium, molybdenum, nitrogen, vanadium, cobalt, iron and other elements was selected as a prototype, while the total ratio of components is, wt.%:

Carbon 0.01 - 0.05 Silicon 0.05 - 0.50 Manganese 16.0 - 19.0 Phosphorus up to 0.04 Sulfur up to 0.01 Copper 0.50 - 0.80 Nickel 3.5 - 5.0 Chromium 17.0 - 21.0 Molybdenum 1.80 - 3.50 Nitrogen 0.0010 - 0.0050 Cobalt 0.1 - 3.0 Vanadium 0.1 - 2.0 Other elements [B, O]: 0.001 - 0.015 Iron rest

[EP2248919A1, publication date: 11/10/2010, IPC: C21D 8/12; C21D 9/22; C22C 38/04].

The advantages of the prototype over the known technical solution are higher strength characteristics of steel, in particular its mechanical properties, due to the presence of additional components in the alloy that prevent the development of microcracks in the interdendritic space and enhance dispersion hardening, thereby increasing the strength, hardness and wear of steel.

However, the disadvantages of the prototype are the unsatisfactory performance characteristics of steel, due to the low diffusion mobility of metal atoms inside the crystalline matrix, as a result of which the ductility of steel decreases and it is difficult to manufacture products from it by stamping, drawing or forging.

The technical problem to be solved by the invention is the need to improve the performance of steel.

The technical result, to which the invention is directed, is to increase the strength of steel with the concomitant preservation of its ductility.

The essence of the invention is as follows.

Steel containing iron, carbon, silicon, manganese, phosphorus, sulfur, chromium, molybdenum, nickel, nitrogen, aluminum, copper, cobalt and vanadium. Unlike the prototype, the steel additionally contains calcium, strontium, barium and niobium, while the total ratio of the components is, wt.%:

Carbon up to 0.05 Silicon up to 0.3 Manganese 18.0 - 20.0 Phosphorus up to 0.03 Sulfur up to 0.005 Chromium 15.5 - 17.5 Molybdenum 2.4 - 2.8 Nickel 4.2 - 5.0 Nitrogen 0.4 - 0.5 Aluminum up to 0.3 Copper up to 0.7 Cobalt up to 0.03 Calcium 0.003 - 0.010 Strontium 0.001 - 0.010 Barium 0.001 - 0.010 Niobium 0.01 - 0.05 Vanadium 0.01 - 0.05 Iron rest.

(карбида железа), в присутствии которого существенно увеличивается твердость стали. Однако, в случае если концентрация углерода в стали будет выше допустимой границы, это приведет к ухудшению пластических свойств сплава.Carbon provides hardening of steel, increasing its hardness and elasticity. The concentration of carbon in the composition of steel is up to 0.05 wt.%. The presence of carbon in the composition of steel in a minimum amount is necessary for the formation of cementite

(iron carbide), in the presence of which the hardness of steel increases significantly. However, if the concentration of carbon in the steel is above the permissible limit, this will lead to a deterioration in the plastic properties of the alloy.

Silicon is present in the composition of steel as a deoxidizer and provides an increase in the elasticity of steel, as well as its resistance to corrosion. The concentration of silicon in steel is up to 0.3 wt.%. The presence of silicon in the composition of steel in a minimum amount is necessary to reduce the amount of oxygen in the steel. However, if the concentration of silicon in the steel is higher than the permissible limit, this will lead to the formation of refractory slags that impede the process of manufacturing steel products by welding, as well as to increase the hardness and brittleness of the steel.

, препятствуя образованию вредного соединения

(сульфид железа). Концентрация марганца в стали находится в диапазоне 18,0 - 20,0 масс.%. В случае если концентрация марганца в составе стали будет больше верхней границы указанного диапазона, то это приведет образованию тугоплавких шлаков, затрудняющих последующую работу с полученным сплавом. В случае если концентрация марганца в составе стали будет ниже нижней границы указанного диапазона, то это приведет к повышению магнитных свойств стали, а также разупрочнению стали.Manganese provides hardening of steel, increasing its hardness and wear resistance. Manganese also binds sulfur and forms manganese sulfide

preventing the formation of harmful compounds

(iron sulfide). The concentration of manganese in steel is in the range of 18.0 - 20.0 wt.%. If the concentration of manganese in the composition of the steel is greater than the upper limit of the specified range, then this will lead to the formation of refractory slags that make it difficult to work with the resulting alloy. If the concentration of manganese in the steel composition is below the lower limit of the specified range, this will lead to an increase in the magnetic properties of the steel, as well as softening of the steel.

Phosphorus and sulfur are present in the alloy as harmful impurities, the presence of which is undesirable. The concentration of phosphorus in steel is up to 0.03 wt.%, and the concentration of sulfur is up to 0.005 wt.%. If the concentration of phosphorus or sulfur is above the permissible limits, this will lead to an increase in the brittleness of the steel both at low temperatures (cold brittleness) and at high temperatures (red brittleness), as well as an increase in abrasion and a decrease in the corrosion resistance of steel.

Chromium provides hardening of steel, increasing its resistance to corrosion and wear. The concentration of chromium in steel is in the range of 15.5 - 17.5 wt.%. If the concentration of chromium in the composition of the steel is greater than the upper limit of the specified range, then this will lead to a decrease in the ductility of the steel and an increase in its magnetic properties. If the concentration of chromium in the steel composition is below the lower limit of the specified range, this will lead to softening, as well as a significant decrease in the corrosion resistance of the steel.

Molybdenum provides increased elasticity, strength and corrosion resistance of steel. Molybdenum also helps to reduce the grain size of steel, thereby reducing its brittleness and increasing fatigue strength. The concentration of molybdenum in steel is in the range of 2.4 - 2.8 wt.%. If the concentration of molybdenum in the composition of the steel is greater than the upper limit of the specified range, this will lead to an increase in the refractoriness of the steel. If the molybdenum concentration in the steel composition is below the lower limit of the specified range, this will lead to an increase in the grain size of the steel and its softening.

Nickel provides an increase in the corrosion resistance of steel, as well as an increase in its strength and toughness. Also, in combination with chromium and molybdenum, nickel significantly increases the heat hardening ability of steel and increases its fatigue strength. The concentration of nickel in steel is in the range of 4.2 - 5.0 wt.%. If the concentration of nickel in the composition of the steel is greater than the upper limit of the specified range, then this will not improve the properties of the steel, but will increase its material consumption. If the concentration of nickel in the steel composition is below the lower limit of the specified range, this will lead to softening of the steel and a decrease in its impact strength, as well as an increase in its magnetic properties.

Nitrogen provides an increase in the strength of steel, with the concomitant preservation of its ductility. The concentration of nitrogen in steel is in the range of 0.4 - 0.5 wt.%. If the concentration of nitrogen in the steel composition is greater than the upper limit of the specified range, this will lead to an increase in nitrogen in the unbound state, as a result of which the strength and ductility of the steel are significantly reduced. If the concentration of nitrogen in the steel composition is below the lower limit of the specified range, then this concentration may not be enough to ensure the achievement of increased strength and ductility of the steel.

и снижения количества кислорода в стали. Однако, в случае если концентрация алюминия в стали будет выше допустимой границы, это приведет к укрупнению размера неметаллических включений в стали.Aluminum is present in steel as a deoxidizer. The concentration of aluminum in steel is up to 0.3 wt.%. The presence of aluminum in the composition of steel in a minimum amount is necessary for the formation of aluminum oxide

and reducing the amount of oxygen in the steel. However, if the concentration of aluminum in the steel is above the permissible limit, this will lead to an increase in the size of non-metallic inclusions in the steel.

Copper and cobalt are undesirable impurities in the composition of steel. The concentration of copper in steel is up to 0.7 wt.%. If the concentration of copper in steel is above the permissible limit, this will lead to a deterioration in the surface quality of products made from steel. The concentration of cobalt in steel is up to 0.03 wt.%. If the concentration of cobalt in steel is above the permissible limit, this will lead to an increase in its magnetic properties.

и уменьшает количество кислорода в составе стали снижая, тем самым, количество неметаллических включений, а также их размер. Концентрация кальция в стали находится в диапазоне 0,003 - 0,010 масс.%. В случае если концентрация кальция в составе стали будет больше верхней границы указанного диапазона, то это приведет к обогащению границ зерен легкоплавкой эвтектикой и снижению пластичности стали . В случае если концентрация кальция в составе стали будет ниже нижней границы указанного диапазона, то этой концентрации может быть недостаточно для того, чтобы образовать оксид кальция

и связать весь содержащийся в сплаве кислород.Calcium provides an improvement in the plastic properties of steel, in particular elongation and impact strength. The improvement in the plastic properties of steel is due to the fact that when calcium is introduced, it dissolves in the alloy being processed and forms calcium oxide.

and reduces the amount of oxygen in the steel composition, thereby reducing the number of non-metallic inclusions, as well as their size. The concentration of calcium in steel is in the range of 0.003 - 0.010 wt.%. If the concentration of calcium in the composition of the steel is greater than the upper limit of the specified range, then this will lead to the enrichment of the grain boundaries with low-melting eutectic and a decrease in steel ductility. If the concentration of calcium in the steel composition is below the lower limit of the specified range, then this concentration may not be enough to form calcium oxide

and bind all the oxygen contained in the alloy.

Barium and strontium are present in the alloy as elements that enhance and reinforce the effect of calcium, namely, improve its assimilation during the smelting process and improve the toughness of steel by reducing the amount of non-metallic inclusions. Barium and strontium affect the size and shape of non-metallic inclusions, in particular, their globularization (acquisition of a rounded shape), for their better settling and subsequent removal. The concentration of barium in steel is in the range of 0.001-0.010 mass%. The concentration of strontium in steel is in the range of 0.001-0.010 mass%. If the concentration of barium and/or strontium in the composition of the steel is greater than the upper limits of the specified ranges, then this will lead to the occurrence of secondary oxidation processes, which adversely affects the mechanical properties of the steel. If the concentration of barium and/or strontium in the steel composition is below the lower limits of the specified ranges, then this concentration may not be enough to ensure the most effective modification and removal of non-metallic inclusions from the steel composition.

, нитридов

, а также карбонитридов

они обеспечивают уменьшение диффузионной подвижности атомов металлической матрицы и образуют дисперсные упрочняющие фазы между атомами металла. Также ниобий обеспечивает снижение скорости диффузионного обмена при высоких температурах, затрудняя коагуляцию дисперсных фаз и вызывая, тем самым, повышение прочности и твердости стали при высоких температурах. Концентрация ниобия в стали находится в диапазоне 0,01 - 0,05 масс.%. В случае если концентрация ниобия в составе стали будет больше верхней границы указанного диапазона, то это усиливает неравномерное распределение нагрузки при эксплуатации изделия, что влечет за собой интенсивное развитие микротрещин в междендритном пространстве. В случае если концентрация ниобия в составе стали будет ниже нижней границы указанного диапазона, то этой концентрации может быть недостаточно для достижения повышенных показателей прочности и твердости стали.Niobium provides an increase in the strength and hardness of steel. The increase in strength and hardness is due to the fact that when niobium is introduced into the composition of steel in the form of carbides

, nitrides

, as well as carbonitrides

they provide a decrease in the diffusion mobility of metal matrix atoms and form dispersed strengthening phases between metal atoms. Also, niobium provides a decrease in the rate of diffusion exchange at high temperatures, making it difficult for the coagulation of dispersed phases and thereby causing an increase in the strength and hardness of steel at high temperatures. The concentration of niobium in steel is in the range of 0.01 - 0.05 wt.%. If the concentration of niobium in the steel composition is greater than the upper limit of the specified range, then this increases the uneven distribution of the load during the operation of the product, which entails the intensive development of microcracks in the interdendritic space. If the concentration of niobium in the steel composition is below the lower limit of the specified range, then this concentration may not be enough to achieve increased strength and hardness of the steel.

Vanadium provides an increase in the strength and hardness of steel and is present in its composition to neutralize the development of microcracks in the interdendritic space, due to the excess concentration of niobium. Neutralization of this process is possible by grinding the grain size by introducing vanadium into the steel composition. An increase in the strength and hardness of steel is ensured by the implementation of the effect of dispersion strengthening when vanadium is introduced into the steel. The concentration of vanadium in steel is in the range of 0.01 - 0.05 wt.%. If the concentration of vanadium in the steel composition is greater than the upper limit of the specified range, then this will lead to coagulation of vanadium compounds and softening of the steel. If the concentration of vanadium in the steel composition is below the lower limit of the specified range, then this concentration may not be enough to achieve increased strength and hardness of the steel.

The invention can be made from known materials using known means, which indicates its compliance with the criterion of patentability "industrial applicability".

The invention is characterized by a set of essential features previously unknown from the prior art, characterized in that the steel additionally contains calcium, strontium, barium and niobium in the indicated concentrations. The presence of calcium, strontium and barium in the composition of the steel makes it possible to reduce the size and number of non-metallic inclusions by reducing the amount of oxygen in the steel, which ensures an increase in the ductility of the steel. The introduction of niobium into the composition of steel makes it possible to improve the structure of the metal matrix of the alloy by reducing the diffusion mobility of atoms inside it, as well as the formation of strengthening phases in the form of carbides, nitrides and carbonitrides of niobium, which has a positive effect on the strength and hardness of the steel. Compliance with the concentrations of calcium, strontium, barium and vanadium within the specified limits allows you to stabilize the plastic properties of steel, without reducing its strength. As a result of using the specified set of elements and introducing them into the alloy in the specified concentrations, the steel of the optimal morphological structure is obtained, which makes it possible to achieve high rates of hardness, strength and ductility.

This ensures the achievement of the technical result, which consists in increasing the strength of steel, while maintaining its ductility, thereby improving its performance.

The invention has a set of essential features previously unknown from the prior art, which indicates its compliance with the criterion of patentability "novelty".

The prior art known steel, which includes calcium with the same basic components. Steel is also known, the composition of which, with the same main components, with the exception of calcium, contains vanadium. However, steel is unknown from the prior art, which, with the main constituent components, would additionally contain calcium, strontium, barium, vanadium and niobium in the indicated ratios. Also, the synergistic effect is unknown from the prior art, consisting in a significant hardening of steel without the risk of increasing its brittleness due to the combined use of vanadium and niobium as alloying additives. The introduction of niobium into the composition of steel provides an increase in its strength and hardness, however, niobium carbides, nitrides and carbonitrides tend to form clusters and lines in the boundary volumes of grains, which increases the heterogeneity of the morphological structure of the steel and, as a result, the uneven distribution of loads during the operation of steel products . To neutralize this negative effect observed when niobium is introduced into steel, vanadium is additionally introduced into it, which makes it possible to reduce the size of steel grains. The combined use of vanadium and niobium as alloying additives makes it possible to achieve the effect of strengthening steel without the risk of increasing its brittleness. Also, the synergistic effect of the complex addition of calcium, strontium and barium and vanadium with niobium as alloying additives to steel is unknown from the prior art, which consists in acquiring high strength and hardness by steel without losing its ductility, which contributes to a uniform distribution of loads inside products made from steel and improves the quality of their work both in compression and in tension. It is known that the introduction of components into steel that increase its strength, in particular vanadium and niobium, leads to some decrease in the ductility of the metal, which makes its further processing and the process of manufacturing products from this metal difficult. To stabilize the plastic properties of steel, components such as calcium, strontium and barium are additionally introduced into it, each of which, using various mechanisms of interaction with atoms of the metal matrix, reduces the size and number of non-metallic inclusions, which has a positive effect on the plastic properties of steel. In view of this, the invention meets the criterion of patentability "inventive step".

The invention is illustrated by the drawing, which shows the following tables:

Table 1 - Compositions of the alloy according to the invention and the alloy according to the prototype.

Table 2 - Results of testing the compositions of the alloy according to the invention and the alloy according to the prototype for tension and impact strength.

In order to illustrate the possibility of implementation and a better understanding of the essence of the invention, an embodiment of its implementation is presented below, which can be modified or supplemented in any way, while the present invention is by no means limited to the presented embodiment.

The invention is illustrated by the following implementation example.

To obtain 1000 kg of the alloy, chromium, charge material and carbon were taken, while the charge material was represented by iron with inclusions of copper, cobalt, sulfur and phosphorus, as well as copper and cobalt. Chromium, charge material and carbon were placed in an arc steel-smelting furnace DSP-6, after which the alloy was smelted at temperatures of 1680-1710 ° C and a chromium iron-carbon semi-product was obtained, while the number of phosphorus inclusions decreased during melting in the furnace. The resulting semi-finished product was subjected to out-of-furnace treatment in a ladle-furnace unit (LAF) at temperatures of 1630-1780°C with adjustment of the chemical composition of the alloy by introducing manganese, chromium, nickel, molybdenum and carbon into the intermediate product, while in the process of out-of-furnace treatment the amount of sulfur inclusions decreased. The resulting alloy was transferred to a chamber-type degasser, where vacuum-oxygen refining of the alloy, purging it with oxygen, and deoxidation by adding silicon and aluminum to the alloy were performed. After the deoxidation of the alloy, it was again transferred to the ACP and out-of-furnace processing and alloying of the alloy with nitrogen at temperatures of 1600–1650°C were carried out, after which calcium, strontium, barium, niobium and vanadium were introduced into the alloy. At the end of the out-of-furnace treatment, the alloy was poured into molds for forging ingots by the siphon method with the addition of slag-forming, heat-insulating and exothermic materials, and the casting start temperature was 1470-1500°C. After pouring the alloy into molds for forging ingots, the alloy crystallized, and then the ingots were removed and their subsequent processing.

Alloy 1

To obtain 1000 kg of steel, 180 kg of Cr, 0.6 kg of C and 573.97 kg of charge material were taken, which was represented by 568.3 kg of Fe, as well as inclusions of Cu with a mass of 4 kg, Co with a mass of 0.5 kg, and inclusions of P weighing 0.9 kg and S weighing 0.27 kg, the number of which decreased in the process of obtaining the alloy: P to 0.5 kg and S to 0.07 kg. Then 170 kg Mn, 5 kg Cr, 38 kg Ni, 22 kg Mo and 0.1 kg C, 1 kg Si, 5 kg Al, 0.01 kg Ca, 0.01 Sr, 0.01 kg Ba, 0.01 kg .7 kg Nb and 0.7 kg V and N in the amount of 3.5 kg.

Alloy 2

To obtain 1000 kg of steel, 175 kg of Cr, 0.5 kg of C and 571.02 kg of charge material were taken, which was represented by 564.56 kg of Fe, as well as inclusions of Cu with a mass of 5 kg, Co with a mass of 0.4 kg, and inclusions of P weighing 0.8 kg and S weighing 0.26 kg, the number of which decreased in the process of obtaining the alloy: P to 0.4 kg and S to 0.06 kg. Then 175 kg Mn, 5 kg Cr, 40 kg Ni, 23 kg Mo and 0.1 kg C, 2 kg Si, 4 kg Al, 0.01 kg Ca, 0.01 Sr, 0.01 kg Ba, 0.01 kg .6 kg Nb and 0.6 kg V and N in the amount of 3.75 kg.

Alloy 3

To obtain 1000 kg of steel, 170 kg of Cr, 0.4 kg of C and 568.15 kg of charge material were taken, which was represented by 559.8 kg of Fe, as well as inclusions of Cu with a mass of 7 kg, Co with a mass of 0.3 kg, and inclusions of P weighing 0.7 kg and S weighing 0.35 kg, the number of which decreased in the process of obtaining the alloy: P to 0.3 kg and S to 0.05 kg. Then 180 kg Mn, 5 kg Cr, 42 kg Ni, 24 kg Mo and 0.1 kg C, 3 kg Si, 3 kg Al, 0.03 kg Ca, 0.01 Sr, 0.01 kg Ba, 0.01 kg .5 kg Nb and 0.5 kg V and N in the amount of 4 kg.

Alloy 4

To obtain 1000 kg of steel, 163 kg of Cr, 0.4 kg of C and 565.14 kg of charge material were taken, which was represented by 556.688 kg of Fe, as well as Cu inclusions with a mass of 7 kg, Co with a mass of 0.3 kg, and P inclusions with a mass of 0 .7 kg and S weighing 0.45 kg, the number of which decreased in the process of obtaining the alloy: P to 0.3 kg and S to 0.05 kg. Then 185 kg Mn, 7 kg Cr, 44 kg Ni, 25 kg Mo and 0.1 kg C, 3 kg Si, 3 kg Al, 0.0475 kg Ca, 0.0325 Sr, 0.0325 kg Ba, 0.0325 kg .4 kg Nb and 0.4 kg V and N in the amount of 4.25 kg.

Alloy 5

To obtain 1000 kg of steel, 155 kg of Cr, 0.4 kg of C and 562.13 kg of charge material were taken, which was represented by 553.575 kg of Fe, as well as Cu inclusions with a mass of 7 kg, Co with a mass of 0.3 kg, and P inclusions with a mass of 0 .7 kg and S weighing 0.55 kg, the number of which decreased in the process of obtaining the alloy: P to 0.3 kg and S to 0.05 kg. Then 190 kg Mn, 10 kg Cr, 46 kg Ni, 26 kg Mo and 0.1 kg C, 3 kg Si, 3 kg Al, 0.065 kg Ca, 0.055 Sr, 0.055 kg Ba, 0.3 kg Nb and 0 .3 kg V and N in the amount of 4.5 kg.

Alloy 6

To obtain 1000 kg of steel, 150 kg of Cr, 0.4 kg of C and 559.01 kg of charge material were taken, which was represented by 547.298 kg of Fe, as well as Cu inclusions with a mass of 7 kg, Co with a mass of 0.3 kg, and P inclusions with a mass of 0 .7 kg and S weighing 0.55 kg, the number of which decreased in the process of obtaining the alloy: P to 0.3 kg and S to 0.05 kg. Then 195 kg Mn, 10 kg Cr, 48 kg Ni, 27 kg Mo and 0.1 kg C, 3 kg Si, 3 kg Al, 0.0825 kg Ca, 0.0775 Sr, 0.0775 kg Ba, 0.0 .2 kg Nb and 0.2 kg V and N in the amount of 4.75 kg.

Alloy 7

To obtain 1000 kg of steel, 145 kg of Cr, 0.4 kg of C and 556.00 kg of charge material were taken, which was represented by 547.35 kg of Fe, as well as inclusions of Cu with a mass of 7 kg, Co with a mass of 0.3 kg, and inclusions of P weighing 0.7 kg and S weighing 0.65 kg, the number of which decreased in the process of obtaining the alloy: P to 0.3 kg and S to 0.05 kg. Then 200 kg Mn, 10 kg Cr, 50 kg Ni, 28 kg Mo and 0.1 kg C, 3 kg Si, 3 kg Al, 0.1 kg Ca, 0.1 Sr, 0.1 kg Ba, 0.1 kg .1 kg Nb and 0.1 kg V and N in the amount of 5 kg.

Alloy 8

To obtain 1000 kg of steel, 140 kg of Cr, 0.3 kg of C and 552.89 kg of charge material were taken, which was represented by 543.348 kg of Fe, as well as Cu inclusions with a mass of 8 kg, Co with a mass of 0.2 kg, and P inclusions with a mass of 0 .7 kg and S weighing 0.64 kg, the number of which decreased in the process of obtaining the alloy: P to 0.3 kg and S to 0.04 kg. Then 205 kg Mn, 10 kg Cr, 52 kg Ni, 29 kg Mo and 0.1 kg C, 4 kg Si, 2 kg Al, 0.1175 kg Ca, 0.1225 Sr, 0.1225 kg Ba, 0.1225 kg 05 kg Nb and 0.05 kg V and N in the amount of 5.25 kg.

Alloy 9

To obtain 1000 kg of steel, 138 kg of Cr, 0.2 kg of C and 549.84 kg of charge material were taken, which was represented by 539.405 kg of Fe, as well as Cu inclusions with a mass of 9 kg, Co with a mass of 0.1 kg, and P inclusions with a mass of 0 .6 kg and S weighing 0.73 kg, the number of which decreased in the process of obtaining the alloy: P to 0.2 kg and S to 0.03 kg. Then 210 kg Mn, 7 kg Cr, 54 kg Ni, 30 kg Mo and 0.1 kg C, 5 kg Si, 1 kg Al, 0.135 kg Ca, 0.145 Sr, 0.145 kg Ba, 0.02 kg Nb and 0 .02 kg V and N in the amount of 5.5 kg.

Alloy 10

To obtain 1000 kg of steel, 135 kg of Cr, 0.1 kg of C and 545.74 kg of charge material were taken, which was represented by 534.323 kg of Fe, as well as Cu inclusions with a mass of 10 kg, Co with a mass of 0.1 kg, and P inclusions with a mass of 0 .5 kg and S weighing 0.82 kg, the number of which decreased in the process of obtaining the alloy: P to 0.1 kg and S to 0.02 kg. Then 215 kg Mn, 5 kg Cr, 56 kg Ni, 31 kg Mo and 0.1 kg C, 6 kg Si, 1 kg Al, 0.1525 kg Ca, 0.1675 Sr, 0.1675 kg Ba, 0.1675 kg .01 kg Nb and 0.01 kg V and N in the amount of 5.75 kg.

The percentages of the components of each alloy are presented in Table 1

After that, the obtained samples of alloys were tested, during which the conditional yield strength, tensile strength, relative elongation and relative narrowing, as well as impact strength were determined.

Trial 1

Determination of the conditional yield strength, tensile strength, relative elongation and relative narrowing.

мм и длиной рабочей части

мм и проводили испытания на растяжение в соответствии с ГОСТ 1497-84. Испытания проводили на гидравлической испытательной горизонтальной машине ГИМГ-20000 при температуре окружающей среды 20°С. Образцы помещали в захваты испытательной машины и закрепляли, после чего производили постепенное нагружение образца. Нагружение образца производили равными ступенями по

, до усилия равного

при этом время выдержки на каждой ступени составляло 6 секунд. Затем нагружение образца производили равными ступенями по

, время выдержки на каждой ступени составляло 5 секунд. При достижении образцом остаточного удлинения, равного 0,2% от длины рабочей части образца, то есть на 1,9 мм, фиксировали приложенную нагрузку, вызывающую остаточное удлинение

, кН. При последующем нагружении образца до достижения им разрушения, фиксировали приложенную нагрузку, предшествующую разрушению

, кН и прекращали нагружение. После разрушения образца, разрушенные части образца складывали так, чтобы их оси образовали прямую линию, и при помощи штангенциркуля измеряли конечную расчетную длину образца

, мм, посредством измерения расстояния между метками, ограничивающими расчетную длину, при этом значение штангенциркуля по нониусу составляло 0,1 мм. Затем разрушенные части образца отсоединяли друг от друга и при помощи штангенциркуля измеряли минимальный диаметр образца после разрыва

, мм в двух взаимно перпендикулярных направлениях, значение штангенциркуля по нониусу составляло 0,1 мм. По среднему арифметическому из полученных значений вычисляли площадь поперечного сечения образца после разрыва

. Полученные результаты испытаний заносили в Таблицу 2.We took samples of the alloy in the form of cylinders with marks pre-applied on the working part of the sample every 5 mm, with a diameter of the working part of the sample

mm and the length of the working part

mm and tensile tests were carried out in accordance with GOST 1497-84. The tests were carried out on a hydraulic testing horizontal machine GIMG-20000 at an ambient temperature of 20°C. The samples were placed in the grips of the testing machine and fixed, after which the sample was gradually loaded. The sample was loaded in equal steps along

, up to an effort equal to

the exposure time at each stage was 6 seconds. Then the sample was loaded in equal steps along

, the exposure time at each stage was 5 seconds. When the sample reached a residual elongation equal to 0.2% of the length of the working part of the sample, that is, by 1.9 mm, the applied load was fixed, causing the residual elongation

, kN During the subsequent loading of the sample until it reached fracture, the applied load preceding the fracture was recorded.

, kN and stopped loading. After the destruction of the sample, the destroyed parts of the sample were folded so that their axes formed a straight line, and using a caliper, the final estimated length of the sample was measured.

, mm, by measuring the distance between the marks that limit the estimated length, while the value of the vernier caliper was 0.1 mm. Then the destroyed parts of the sample were disconnected from each other and using a caliper, the minimum diameter of the sample after the break was measured.

, mm in two mutually perpendicular directions, the value of the vernier caliper was 0.1 mm. The arithmetic mean of the obtained values was used to calculate the cross-sectional area of the sample after rupture

. The obtained test results were entered in Table 2.

, временное сопротивление

, относительное удлинение после разрыва

, а также относительное сужение

.After the end of the tests, the obtained results were processed and the conditional yield strength was determined

, temporary resistance

, relative elongation after rupture

, as well as the relative narrowing

.

The conditional yield strength was determined by the formula:

- нагрузка, вызывающая остаточное удлинение образца на 0,2%, кН;where

- load causing residual elongation of the sample by 0.2%, kN;

- начальная площадь поперечного сечения образца,

.

is the initial cross-sectional area of the specimen,

.

The temporary resistance was determined by the formula:

- нагрузка, предшествующая разрушению образца, кН;where

- load preceding the destruction of the sample, kN;

- площадь поперечного сечения рабочей части образца до испытания,

.

- cross-sectional area of the working part of the sample before testing,

.

Relative elongation after rupture was determined by the formula:

- конечная расчетная длина образца, мм;where

- the final estimated length of the sample, mm;

- начальная расчетная длина образца, мм.

- the initial estimated length of the sample, mm.

The relative contraction after rupture was determined by the formula:

- начальная площадь поперечного сечения образца,

;where

is the initial cross-sectional area of the specimen,

;

- площадь поперечного сечения образца после разрыва,

.

is the cross-sectional area of the specimen after rupture,

.

The calculation results were summarized in Table 2.

Test 2.

Determination of impact strength.

определяли по шкале маятникового копра.Samples were taken in the form of rectangular bars with a cross section of 10x10 mm, 55 mm long, with a V-shaped notch (concentrator) 2 mm wide and deep, located on one of the faces of the bar, and tested for impact strength in accordance with GOST 9454-78. The tests were carried out on a pendulum impact tester with a nominal potential energy of the pendulum of 300 J, made in accordance with GOST 10708-82. The sample was mounted on the copra supports using a template that ensures the symmetrical location of the concentrator relative to the supports, so that the sample lies freely, and the pendulum impact falls on the side opposite to the concentrator. The pendulum, which was in its original position, was released, and when it fell, the pendulum knife hit the sample, as a result of which it was destroyed. The work of the beat

was determined on the scale of a pendulum impact tester.

определяли по формуле:impact strength

determined by the formula:

- работа удара, Дж;where

- impact work, J;

- начальная площадь поперечного сечения образца в месте концентратора,

. Для всех испытаний на ударную вязкость начальная площадь поперечного сечения образца в месте концентратора составляла

- the initial cross-sectional area of the sample at the site of the concentrator,

. For all impact tests, the initial cross-sectional area of the specimen at the concentrator was

The test and calculation results were entered in Table 2.

For the prototype alloy, tests to determine impact strength were not carried out.

The obtained compositions of the alloy according to the invention were subjected to tensile tests and impact tests, with the exception of the prototype alloy. The test results were entered in Table 2 and were further analyzed. In the course of the analysis, it was found that alloys 3 to 7 had satisfactory strength and ductility indicators, while alloy number 5 had the best indicators, in which, along with achieving high tensile strength and yield indicators, ductility indicators such as relative elongation and impact viscosity, had optimal values at which it is possible for the material to change its shape under the action of external forces, without destruction, and to maintain this shape when these forces are eliminated. Such results are due to the fact that in alloys 3 to 7, the element concentrations did not go beyond the upper or lower limits of the established ranges.

Alloys 1 to 2 had poor elongation and toughness characteristics due to the low content of calcium, strontium and barium in these alloys.

Alloys 8 to 10 had poor tensile and yield strength characteristics due to the low content of niobium and vanadium in these alloys.

With regard to the prototype alloy, it was found that it had satisfactory strength and ductility, however, the values of these indicators were lower than those achieved by alloys 3 to 7.

Thus, the technical result is achieved, which consists in increasing the strength of steel, while maintaining its ductility, thereby improving its performance.

Claims (2)

Steel containing iron, carbon, silicon, manganese, phosphorus, sulfur, chromium, molybdenum, nickel, nitrogen, aluminum, copper, cobalt and vanadium, characterized in that it additionally contains calcium, strontium, barium and niobium in the following ratio of components, wt.%: carbon up 0.05 silicon up 0.3 manganese 18.0-20.0 phosphorus to 0.03 sulfur to 0.005 chromium 5.5-17.5 molybdenum 2.4-2.8 nickel 4.2-5.0 nitrogen 0.4-0.5 aluminum up to 0.3 copper up 0.7 cobalt up to 0.03 calcium 0.003-0.01 strontium 0.001-0.01 barium 0.001-0.01 niobium 0.01-0.05 vanadium 0.01-0.05 iron rest

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