Steel construction for electrotermometry

 

(57) Abstract:

The invention relates to metallurgy, in particular to the development of low-alloy structural steel with two-phase territorality structure used in cold landing high-strength rod fasteners. The proposed steel contains components in the following ratio, wt.%: carbon 0,06-0,11; manganese 0,30-0,9; silicon of 0.01 to 0.15; Bor 0,0005-0,0050; vanadium of 0.005 to 0.08; aluminum 0,02-0,06; titanium 0.01 to 0.04, sulfur of 0,005 0,020; nitrogen 0,005-0,015; calcium 0,001-0,010. And: ; ; . The technical result of the invention is to increase hardenability characteristics of the claimed steel, which will provide a guaranteed level of consumer properties and through-hardenability of steel with a diameter up to 20 mm table 2.

The invention relates to the field of metallurgy, in particular to the development of low-alloy structural steel, intended for the manufacture of billets with two-phase territorality structure used in cold landing high-strength fasteners without the final heat strengthening.

Known structural steel containing, wt.%: carbon 0.06 to 0,30%, silicon of 0.17 to 1.0%, manganese 0,8-2 is th steels are low manufacturability, insufficient hardenability, wide border element content, which does not allow to ensure the stability properties of steel.

Closest to the technical essence and the achieved effect to the proposed steel is a steel containing the proposed steel is a steel containing, in wt.%: carbon 0,18-0,24%, silicon 0,17-0,37%, manganese 0,90-1,30%, boron 0,0005-0,0050%, nitrogen 0,005-0,015%, vanadium of 0.01 to 0.08%, aluminum 0,02-0,06%, titanium 0.01 to 0.04%, the rest of the iron, in the following ratio elements and [2]. The disadvantages of the known steel is too high content of carbon, manganese and silicon, which will not allow to obtain the desired complex consumer properties during deformation hardening in the process of landing a high-strength rod fasteners.

The objective of the invention is to increase the hardenability characteristics for a given range of consumer characteristics and the provision of through-hardenability thermolysine steel with a diameter up to 20 mm

This object is achieved in that the proposed steel containing carbon, manganese, silicon, vanadium, titanium, nitrogen, aluminum, boron, and the remainder of iron, it also contains sulfur, calcium, in the following ratio of the components

Vanadium is 0.005 to 0.08%

Aluminum 0,02-0,06%

Titanium 0.01 to 0.04%

Sera of 0,005 0,020

Nitrogen 0,005-0,015

Calcium 0,001-0,010%

And

Impurities include phosphorus to 0.025%, Nickel up to 0.20%, copper up to 0.20%.

Given the combination of alloying elements allow you to get in the proposed steel rod with a diameter up to 20 mm) after quenching using a heating current of high purity and spray cooling water evenly located two-phase territorality structure designed for cold massive forming high-strength rod fasteners, providing a guaranteed level properties without the final surgery of heat strengthening.

Carbon and carbonitrides elements are introduced into the composition of this steel to ensure a fine grain structure, which will increase as the level of its strength, and to provide a given level of ductility. While vanadium manages the processes in the austenitic region (determines the tendency to grain growth of austenite (up to 950°C), stabilizes the structure during thermomechanical processing, increases the temperature of recrystallization and the Kai. The upper limit of carbon content (0,11%), vanadium (0,08%) due to the need to ensure the required level of ductility of steel, and the bottom, respectively 0,06%, 0.005% and provide the required strength level of the steel.

Manganese is used, on the one hand, as a solid solution hardener, on the other hand, as an element of substantially increasing the stability of the supercooled austenite and increases the hardenability of steel. The upper levels of manganese - 0,90% - determined by the need to ensure the required level of ductility of steel, and the bottom of 0.30%, the need to provide an appropriate level of strength and hardenability of the steel.

Silicon belongs to territooriumil elements. The lower limit on the silicon of 0.01% is caused by the deoxidation of steel. The silicon content above 0.15 percent will adversely affect the characteristics of ductility of steel.

Boron contributes to a sharp increase in the hardenability of steel. The upper limit of the boron content is determined by considerations of ductility of steel, and the lower the need to ensure the required level of hardenability.

Aluminum and titanium are used as deoxidizers and about the AK lower levels of data elements (0.02 and 0.01 respectively) is determined by the requirement to ensure the hardenability of steel, and the top level of 0.06 and 0.04) - requirement to provide a given level of ductility of steel.

Nitrogen, an element involved in the formation of carbonitrides, while lower levels (0,005%), is determined by the requirement to provide a given level of strength, and the upper level (0,015%), the requirement to provide a given level of ductility and hardenability.

Calcium is an element, modifying nonmetallic inclusions. The upper limit, as in the case of sulfur caused by the necessity of obtaining a given level of ductility and toughness of steel, and the lower limit - questions-tech production.

Sulfur determines the level of ductility of steel. The upper limit is caused by the necessity of obtaining a given level of ductility and toughness of steel, and the lower limit - questions-tech production.

To ensure complete bonding of nitrogen in the nitride type TiN and AlN as the result of reactions

[Ti]+[N]=TiN

[Al]+[N]=AlN

requires the following ratios of elements, otherwise protection boron from tying it in nitrides and decrease characteristics of the hardenability of steel.

Touristiki hardenability of steel.

The ratio Mn+5,HS,08, on the one hand, defines the conditions that ensure a given level of strength of the steel, on the other hand, determines the level of the base doping, providing a minimum level of hardenability of steel.

The ratio of , on the one hand, determines the conditions of providing a given level of viscosity steel as calcium modifies nonmetallic inclusions, on the other hand, determines the level of calcium, necessary for partial bonding of oxygen, freeing up an additional amount of aluminum and provides additional protection boron from binding in the nitrides.

Comparative analysis of the prototype allows us to conclude that the claimed composition differs from the known introduction of new components - sulfur and calcium, as well as correlations , Mn+5,HS,08, .

Thus, the proposed solution meets the criterion of "novelty".

Analysis of patent and scientific and technical information not found solutions with the same set of features, which would reach a similar effect - enhancing characteristics of the hardenability of steel.

Therefore, the claimed combination of attribute is on invention, not excluding other in the scope of the claims.

In experimental conditions in 60-pound open induction furnace smelted 10 heats experienced steel, whose chemical composition is given in table 1. Steel was poured into 3 ingot weighing 17 kg, which are then forged on tutuncu section 7070 mm, Then the in rolled to a sheet thickness of 14 mm From the sheet made of billet samples with a diameter of 14 mm, which underwent heat treatment at automotive complex with heating by high-frequency currents to a temperature of 760°C and the spray cooling water. The thickness of the workpiece and the cooling during hardening provided through hardenability blanks. Next, the blanks are calibrated in fractional scheme with a total degree of deformation of 40%.

The mechanical characteristics were determined on a tangential samples. Tensile test at room temperature were performed on samples of type I, GOST 1497-84 on the test machine "INSTRON-1185" with registration strain deformation. The loading rate of a sample of 5 mm/min was Determined characteristics of strengthbandof 0.2 and plasticity .

Average values were calculated for the results has been evaluated using criteria Student, calculated as follows:

where M1and M2average values compared; S21and S22dispersion medium; - critical criterion Student at a significance level of 0.95 and the number of degrees of freedom .

Characterization of hardenability (critical diameter D50) was performed by the method of mechanical hardening cylindrical samples with a diameter of 25.0 mm and a length of 100 mm with shoulder according to GOST 5657. Before manufacture of sample blanks were heat treated in a chamber furnace at the following mode: normalization, 950°C, 1 h, air. Tested on two sample for smelting. Hardening of the samples was carried out with a water jet in a special unit. In connection with the need to prevent oxidation and decarburization of the end of the sample in direct contact with water during hardening, heating the samples in a chamber furnace (without protective atmosphere) was performed in special glasses. The end of the sample was placed on a special graphite plate. The sample was heated in a furnace to a temperature of 950°C. the Duration of heating of the sample to the quenching temperature was 3050 minutes. The deviation from the set temperature temper the extraction of the sample from the furnace before cooling does not exceed 5 C. The sample was kept under running water until completely cooled (about 1520 minutes). The cooling water temperature was 20±5°C.

For measuring the hardness along the length of the tempered sample was sosotoyalas two diametrically opposite the site to a depth of 0,5±0,1 mm Ground sosotoyalas with abundant cooling water. The roughness of the ground was rougher 7th cleanliness class according to GOST 2789. Not permitted prizhogi, causing structural changes in the metal. Curve hardenability steel measuring the hardness began at a distance of 1.5 mm from the hardened end face in the axial direction. The first 16 measurements from the end of the sample produced with an interval of 1.5 mm, and then through a 3 mm. If at a certain distance from the end of the sample, the hardness does not change, then the measurements were made after one interval, and then stopped the test. To ensure accurate fixation of the measurement of hardness was specially designed and manufactured device. If necessary, re-measuring the hardness at the site at which measurements were taken, the area was pereshlifovyvat. The depth of metal removal when re-grinding was 0.1-50,2 mm Hardness was determined according to Rockwell (HRC) in sooty two opposite sites, calculated average hardness.

Mechanical properties are presented in table 2.

As can be seen from table 2, the proposed steel in comparison with the known higher hardenability characteristics.

SOURCES of INFORMATION

1. USSR author's certificate No. 601321, With 22 38/12, 06.02.1976,

2. RF patent № 2127769, With 22 38/14, 20.03.1999, (prototype).

Structural steel containing carbon, manganese, silicon, vanadium, titanium, nitrogen, aluminum, boron and iron, characterized in that it further contains sulfur and calcium in the following ratio, wt.%

Carbon 0,06-0,11

Manganese 0,30-0,9

Silicon 0,01-0,15

Bor 0,0005-0,0050

Vanadium is 0.005 to 0.08

Aluminum 0,02-0,06

Titanium 0,01-0,04

Sera of 0,005 0,020

Nitrogen 0,005-0,015

Calcium 0,001-0,010

Iron Rest

and

 

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4 ex, 1 tbl

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21 cl, 1 dwg, 9 tbl, 5 ex

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2 tbl, 1 ex

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EFFECT: improved strength and cold resistance of steel.

5 tbl

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