CN1242433A - Steel with high strength and high tenacity structure - Google Patents

Abstract

The present invention belongs to the field of alloy steel. The chemical components of said invented high-strength high-tough structure steel are (wt%) C 0.25-0.35%, Ni 4.0-5.0%, Si 1.7-2.5%, Mn 0.2-1.2%, Cr 0.5-1.5%, Mo 0.02-0.8%, Nb 0.01-0.04%, S is less than or equal to 0.01%, P is less than or equalto 0.01%, O is less than or equal to 50 ppm, N is less than or equal to 50 ppm, and the rest is Fe. Said invention not only possesses higher tensile strength and fracture toughness, but also possesses lower yield ratio and excellent dynamic mechanical properties.

Description

Steel with high strength and high tenacity structure

The invention belongs to field of alloy steel.Mainly be applicable to the component of the load that withstands shocks, particularly bear the parts of high velocity impact.

Component such as the load that withstands shocks, the material that requires to be adopted must have good combination of strength and toughness and higher anti-shearing unstability ability, and favorable shock resistance, promptly require material to have advantages of higher tensile strength and fracture toughness property, and lower yield tensile ratio.Table 1 has been listed the tensile strength (σ of several ultrahigh-strength steel commonly used _b), yield tensile ratio (σ _0.2/ σ _b) and fracture toughness property (K _1c).

The mechanical property of several ultrahigh-strength steel commonly used of table 1

Types of alloys	Title	??σ b	?σ 0.2/σ b	??K 1c??Mpa.m
					Low-alloy super-strength steel	??300M ??30CrMnSiNi2A	??1960 ??1760	??0.75 ??0.83	??71 ??81
Maraging steel	??18Ni(250)	??1850	??0.97	??99
					The secondary hardening martensitic steel	9Ni-5Co (Hp9-4-20 modified version)	??1680	??0.95	??116

As seen from Table 1, the main drawback of low-alloy super-strength steel 300M and 30CrMnSiNi2A is that fracture toughness property is lower.The deficiency of maraging steel 18Ni (250) is that yield tensile ratio is too high, anti-shearing unstability ability.The intensity of the low body steel 9Ni-Co of secondary hardening horse is on the low side, and yield tensile ratio is too high, and is all not ideal enough.It should be noted that back two class steel all contain higher noble element (Co and Ni), the production cost height is difficult to promote the use of.

The object of the present invention is to provide a kind of tensile strength and fracture toughness property height, yield tensile ratio is low and the steel with high strength and high tenacity structure of good economy performance.

Based on above-mentioned purpose, main technical schemes of the present invention is to add nickel, silicon, manganese, chromium, molybdenum and niobium in the pure iron of low-carbon (LC), forms the interalloy quenched and tempered steel.Its concrete chemical ingredients (weight %) is:

C 0.25-0.35%, Ni 4.0-5.0%, Si 1.7-2.5%, Mn 0.2-1.2%, Cr 0.5-1.5%, Mo 0.02-0.8%, Nb 0.01-0.04%, S≤0.01%, P≤0.01%, O≤50PPm, N≤50PPm, surplus is Fe.

Design of chemical composition is according to as follows:

C is the main strengthening element of steel, and it improves the tensile strength of steel by the mode of solid solution and formation carbide.Adding C also can increase the hardening index of steel, reduces yield tensile ratio, thereby improves the dynamic property of steel.But too much C can cause fracture toughness property to reduce, and makes the welding property variation, and C content is at least 0.25%, and the upper limit is no more than 0.35%.

Si can postpone the generation of Low-Temperature Temper Brittleness, plays the solution strengthening effect simultaneously, and the low effect of content is bad, the too high plasticity that can reduce steel, and it is relatively good that Si content is controlled at 1.7-2.5%.

Mn is the same with Ni, all helps forming residual austenite, improves the toughness of steel, thus with Mn for part Ni, it is comparatively suitable that Mn content is controlled at 0.2-1.2%.

Ni can improve matrix toughness, and an amount of Ni and Mn can form the small portion of residual austenite, thereby improves the plasticity and toughness of steel, crosses and makes strength degradation at most.Ni and Cr, Mo can guarantee the necessary hardening capacity of steel simultaneously, and Ni content is at least 4.0%, and the upper limit is no more than 5.0%.

Cr and Ni, Mo acting in conjunction can significantly improve the hardening capacity of steel, and can stop the decomposition of residual austenite, and Cr content is comparatively suitable in the 0.5-1.5% scope.

Mo can improve the hardening capacity of steel in the 0.02-0.8% scope, prevent the generation of temper brittleness, can fall the activity of C simultaneously, stops carbide to be assembled, and keeps the intensity of steel.

Add small amount of N b crystal grain thinning effectively, thereby improve the intensity and the plasticity and toughness of steel.

Simultaneously, in order to obtain good combination of strength and toughness, must strictly control impurity content, its P, S are advisable to be no more than 0.01%, and O, N are no more than 50PPm.

Steel of the present invention adopts the smelting technology of the disconnected remelting of vacuum induction furnace smelting, vacuum induction+electroslag furnace remelting or vacuum induction+vacuum consumable.The steel ingot processing that should homogenize under 1200 ℃ is carried out hot-work subsequently after the melting in 1150-850 ℃ of scope, is incubated under 870-900 ℃ of temperature after the hot-work, and oil cooling carries out quench treatment then, carries out temper at last in 200-300 ℃ of scope.

According to above-mentioned chemical ingredients and the prepared steel of the present invention of production method, not only have advantages of higher tensile strength and fracture toughness property, but also have lower yield tensile ratio, and good dynamic properties.Specific performance is: tensile strength sigma _b〉=1700Mpa, σ _0.2〉=1400Mpa, K _1c〉=115Mpa m, σ _0.2/ σ _b≤ 0.85.

Compared with prior art, the present invention is the tensile strength height not only, and fracture toughness property is good, and yield tensile ratio is low, good economical benefit.

Embodiment

The chemical ingredients scope of steel with high strength and high tenacity structure according to the present invention is smelted 4 stoves steel of the present invention on 135 kilograms of vacuum induction furnaces, its concrete chemical ingredients is as shown in table 2.

After 4 stove smelting steels are cast into ingot, the thermal treatment that under identical conditions, homogenizes, hot-work annealing, quenching, tempering heat treatment.Its concrete processing parameter is as follows:

Homogenize 1200 ℃ of thermal treatment temps of steel ingot, 6 hours time.

1150-1180 ℃ of hot-work Heating temperature, 1 hour heat-up time.

680 ℃ of annealing temperatures, annealing time 1 hour

900 ℃ of quenching temperatures, 1 hour heat-up time

200 ℃ of tempering temperatures, tempering time 2 hours.

After the tempering, the sample of 4 grades of steel is carried out precision work, and at room temperature carry out the test of tension test and fracture property respectively, the gained result lists table 3 in.

In order to contrast, in table 2 and table 3, listed the chemical ingredients and the mechanical property of 30CrMnSiNi2A and two Comparative Examples grades of steel of 9Ni-5Co in.

As seen from Table 3, the present invention compares with Comparative Examples 30CrMnSiNi2A, and intensity index is suitable, but fracture toughness property is higher than the latter; 9Ni-5Co compares with Comparative Examples, and fracture toughness property is suitable, but has advantages of higher tensile strength, lower yield tensile ratio, and with advancing, used valuable alloying element is less, and cost is lower, good economy performance.The chemical ingredients of table 2 embodiment and Comparative Examples grade of steel (weight %)

Steel grade and heat (batch) number		????C	??Si	??Mn	????Ni	??Cr	??Mo
								The present invention	????1	??0.27	??1.96	??0.49	????4.44	??1.05	??0.62
????2	??0.25	??2.10	??0.31	????4.90	??0.70	??0.75
							????3		??0.32	??1.94	??1.10	????4.15	??1.02	??0.32
????4	??0.27	??1.87	??0.51	????4.43	??1.03	??0.51
							Comparative Examples		??30CrMnSiNi2A	??0.31	??1.09	??1.08	????1.52	??1.12	????/
????9Ni-5Co	??0.21	??0.07	??0.23	????9.09	??1.93	??1.92

Continuous table 2

?Co	Nb	?V	?S	?P	?O	?N	Fe
								?/	0.029	?/	?0.004	?0.006	?24	?16	Surplus
?/	0.040	?/	?0.005	?0.006	?30	?19	Surplus
								?/	0.019	?/	?0.006	?＜0.005	?29	?20	Surplus
?/	0.037	?/	?0.003	?＜0.005	?26	?16	Surplus
								?/	/	?/	?0.005	?0.019	?33	?88	Surplus
?5.43	/	?0.8	?0.005	?0.007	?46	?30	Surplus

The mechanical property of table 3 embodiment and Comparative Examples grade of steel

Claims (1)

1. steel with high strength and high tenacity structure is characterized in that chemical ingredients (weight %) is:

C 0.25-0.35%, Ni 4.0-5.0%, Si 1.7-2.5%, Mn 0.2-1.2%, Cr 0.5-1.5%, Mo 0.02-0.8%, Nb 0.01-0.04%, S≤0.01%, P≤0.01%, O≤50PPm, N≤50PPm, surplus is Fe.