Jednostka modified cast steel and method of its manufacture

 

(57) Abstract:

The invention relates to ferrous metallurgy, namely the steel used, for example, steel casting, and to a method of manufacturing such a steel. Proposed jednostka modified cast steel containing components in the following ratio, wt. %: carbon 0.18 to 0.28, manganese 0,60-0,90, silicon 0.20 to 0.52 in, titanium 0,03-0,05, aluminum 0,03-0,06, iron rest. Method of manufacturing gladestone cast steel comprises introducing the molten steel modifier containing calcium, silicon and aluminum, which further comprises barium or REM. In addition, steel is injected titanium or as part of a modifier, either in the form of ligatures in the following ratio of components introduced into the steel, wt. %: calcium 4,1-12,0, barium 4,0-12,0 or REM 8,1-30,0, aluminum 2,0-12,0, titanium 6,0-9,5, silica rest, when the flow modifier or modifier and ligatures of 2.2-3.5 kg/t liquid steel. The technical result of the invention is to improve the impact toughness of the steel to 392 kJ/m2at a temperature of -60oWith while maintaining a high level of properties. 2 S. p. f-crystals, 2 tab.

The invention relates to ferrous metallurgy, namely the steels used for the manufacture of castings, especially otamegane, silicon, impurities of sulfur and phosphorus in the following ratio, wt.%:

Carbon - 0,22-0,30

Manganese - 0,45-0,90

Silicon - 0,20-0,53

Sulfur - N. B. 0,05

Phosphorus - N. B. 0,05. [GOST 977-86, Steel 25L]

Steel is intended for the manufacture of castings especially important purposes, the number of controlled quality indicators which include toughness.

The disadvantage of this steel is that the impact strength at a temperature of -60oC below the required for parts operated at the same temperature, namely 392 kJ/m2.

The closest analogue of the claimed steel is jednostka modified cast steel, which is to improve toughness at subzero temperatures contains components in the following ratio, wt.%:

Carbon - of 0.14-0.21

Silicon - 0,10-0,60

Manganese - 0,40-1,60

Aluminum - 0,004 - 0,05

Calcium - 0,006-0,017

Titanium - 0,01-0,10

Iron - Rest

As impurities, the steel may contain sulfur and phosphorus to 0.025 wt.%. (See USSR author's certificate 639962, With 22 38/14, published 30.12.1978).

The problem to which the invention is directed, is to increase the impact toughness of the steel to 392 kJ/m2privina problem is solved by the proposed jednostka modified cast steel containing carbon, manganese, silicon, titanium, aluminum and iron, in the following ratio, wt.%:

Carbon - 0.18 to 0.28

Manganese - 0,60-0,90

Silicon - 0,20-0,52

Titanium - 0,03-0,05

Aluminum - 0,03-0,06

Iron - Rest

The content of impurities in the steel is limited to:

Sulfur - N. B. being 0.036

Phosphorus - N. B. 0.035

The proposed steel differs from the known fact that it does not contain calcium and lower limits of the contents of carbon, manganese, silicon, aluminum and titanium is increased. This provides increased impact strength at a temperature of -60oC to 392 kJ/m2while maintaining the mechanical properties inherent to become taken for the nearest equivalent.

It was established experimentally:

- when the content of carbon and manganese for the stated limits impact strength at a temperature of 60oC does not match required;

when the content of sulfur and phosphorus over a 0.035% to get the impact strength of not less than 392 kJ/m2at a temperature of 60oC impossible;

the content of titanium and aluminum 0.03% when the content of sulfur and phosphorus does not exceed 0.035% provides impact strength of not less than 392 kJ/m2and save me is the published by third parties, toughness does not reach the required level;

the titanium content exceeds 0.05%, or aluminum than 0.06% also reduces the impact strength due to the non-metallic inclusions.

The test results of steel are presented in table 1.

As follows from the data presented in table. 1, the proposed steel has a toughness 392 kJ/m2at a temperature of 60oC, while maintaining the mechanical properties inherent to become taken for the nearest equivalent.

Example 1. Steel 25L according to GOST standard 977-88), its chemical composition and mechanical properties. Impact strength at a temperature of 60oC Guest was not specified. KCU-60specified in the example, is defined on the Kurgan plant pipeline (CSTA).

Example 2. The more carbon, and manganese less than the stated limit. All other elements within. Impact strength below the required (KCU-60< 392).

Example 3. The estimated steel. The content of sulfur and phosphorus on the level steel, taken for similar. All other elements are within the specified limits. The impact strength is lower than the required.

Example 4. Titanium is less than the lower limit, the remaining elements in the specified limits. The impact strength is lower than the required.

Example 5. Ti is thinned. Other elements within the specified limits. The impact strength is lower than the required.

Example 7. Aluminum is greater than the upper limit. The impact strength is lower than the required.

Examples 8-10. Steel within the specified limits. Mechanical properties of steel correspond to the technical conditions.

The production of steel involves the introduction of liquid steel modifiers and ligatures.

The closest analogue of the claimed steel production method is a method comprising introducing the liquid steel additives in the form of an alloy, which is a deoxidizer, a modifier and a ligature, in the following ratio of components in the input additive, wt.%:

Silicon - 40 - 65

Calcium - 8,0 - 30,0

Aluminum - 1,0-5,0

Vanadium - 3,0-14

Titanium - 0,1-1,0

Iron - Rest.

Cm. EN 2125113 C1, With 22 35/00, published 20.01.1999.

In the proposed method in contrast to the known modification of steel are at the same time three kinds of elements: the inoculators (Ti), inhibitors-scavengers (Al, Ti), inveraray (Ca, Ba or REM), simultaneously affecting the macro-, micro - and submicron cast steel structure that reduces sulfur and phosphorus to the level of a 0.035%, reduces the grain size, ostranenie and micrological steel, titanium and aluminum.

The essence of the claimed method is that the method of production of cold-resistant cast steel comprises introducing the molten steel modifier containing calcium, silicon and aluminum. Unlike well-known in the steel enter modifier, optionally containing barium or REM. Additionally, the steel is injected titanium or as part of a modifier, either in the form of ligatures in the following ratio of components introduced into the steel, wt.%:

Calcium is 4.1 to 12.0

Barium or - 4,0-12,0

REM - 8,1-30,0

Aluminum - 2,0-12,0

Titanium - 6,0-9,5

Silicon - Rest

when the flow modifier or modifier and ligatures of 2.2-3.5 kg/t liquid steel.

The proposed method differs from the known fact that the alloy modifier further comprises barium or REM, with a stated ratio of the components and their consumption of 2.2-3.5 kg/t liquid steel, and titanium is administered either as part of a modifier, or optionally in the form ligatures.

As determined experimentally, if the flow rate of the modifier and the ligature is in the range of 2.2 - 3.5 kg/t, the residual elements, including calcium, in finished steel no. In some of the bottoms to become discovered calcium within not more than 0.002 wt.% or traces, h is so K. , doing its job of cleaning steel from impurities and inversion inclusions, they leave in the slag.

It was established experimentally:

- with the introduction of the modifying elements below the lower limit of the chemical composition of the steel does not conform to the technical conditions. Impact strength below the required (S and P >0,035%, Ti and Al < 0.03 per cent);

- with the introduction of reactive elements or some of them above the upper limit of refractory unfavorable shape and location of nonmetallic inclusions is reduced toughness of the steel at the temperature of 60oC;

- when the flow modifier and alloying elements is less than the lower limit of the chemical composition of the steel does not meet the technical conditions;

- at a flow rate greater than the upper limit of modifying and alloying elements titanium and aluminum may be higher than the upper limit, which leads to a decrease of impact strength due to solid solution hardening.

The results of applying the modifier and alloying elements in steel are shown in table 2.

Example 1. Modifying elements is less than the lower limit. The impact strength is lower than the required. Steel does not meet the technical conditions="ptx2">

Example 3. Titanium is less than the lower limit. Steel does not meet the technical conditions.

Example 4. Titanium greater than the upper limit. The impact strength is lower than the required.

Example 5. Calcium is above the upper limit. Reduced impact strength.

Example 6. The flow modifier and ligatures below the lower limit. Steel does not meet the technical conditions.

Example 7. The flow modifier and ligatures are above the upper limit. The impact strength is reduced due to the solid solution hardening by increasing the content of titanium and aluminum.

Examples 8-10. All parameters within the specified limits. Steel meets specifications.

Steel was tested on Kurgan plant valves on existing equipment with a positive result that, given the technology of steel production allows to recommend it for industrial production.

1. Jednostka modified cast steel containing carbon, manganese, silicon, titanium, aluminum and iron, characterized in that it contains components in the following ratio, wt.%:

Carbon - 0.18 to 0.28

Manganese - 0,60-0,90

Silicon 0.20 to 0.52 in what it became, includes introduction to the molten steel modifier containing calcium, silicon and aluminum, characterized in that the steel is injected modifier, optionally containing barium or REM, in addition to the steel impose titanium or as part of a modifier, either in the form of ligatures in the following ratio of components introduced into the steel, wt.%:

Calcium is 4.1 to 12.0

Barium or - 4,0-12,0

REM - 8,1-30,0

Aluminum - 2,0-12,0

Titanium - 6,0-9,5

Silicon - Rest

when the flow modifier or modifier and ligatures of 2.2-3.5 kg/t liquid steel.

 

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FIELD: iron metallurgy, in particular steel smelting industry.

SUBSTANCE: claimed material contains (mass %): viterite concentrate 40-42; aluminum 38-40; lime 5-12; magnesium 6-8; titanium 1-2. Invention allows increasing the refining ability of material due to modification low valence sulfur and phosphorus compounds in metal melt.

EFFECT: steel of improved quality.

1 tbl, 1 ex

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