CN101220442B - Hot work die steel with high-heat stability and high-strength - Google Patents

Abstract

The invention relates to a novel hot working die steel material and belongs to the technical field of manufacturing process of alloy steel. High-heat stable high-strength hot working die steel of theinvention is characterized by the following components and the weight percentages of C of 0.3 to 0.6 percent, Si of 0.5 to 0.7 percent, Mn of 10.5 to 14.5 percent, Cr of 2.0 to 6.0 percent, Mo of 1.5to 3.5 percent, V of 0.5 to 2.0 percent, P of 0.01 to 0.02 percent, S of less than 0.005 percent and the allowance of Fe. The preparation process for the hot working die steel of the invention is provided as follows: (1) melting; (2) electro slag re-melting; (3) high temperature homogenization; (4) rough forging; (5) blank forging; (6) annealing; (7) quenching; finally, obtaining the hot working die steel. The die steel has the most prominent advantages of good heat stability and still keeping high hardness of more than 45 HRC in the condition of 700 DEG C; the notched bar impact strength at room temperature of the material is more than 300 ding.

Description

Hot work die steel with high-heat stability and high-strength

Technical field

The present invention relates to a kind of novel hot work die steel with high-heat stability and high-strength, belong to the steel alloy manufacturing process technology field.

Background technology

The working conditions of hot-work die steel is quite complicated, and is also very strict to the performance requriements of moulding stock.The kind of hot-work die steel is a lot, as: 3Cr2W8V, 4Cr5MoSi1 (H13) and newer DIEVAR steel.

3Cr2W8V is the hot-extrusion mold steel of using always, it is a kind of high heat-intensity hot-work die steel, and have good forging, mechanical workout and thermal treatment process performance, but its cold and hot fatigue property is relatively poor, toughness is lower, be full of cracks early failure often because of taking place in mould, when especially using water cooling, the thermal fatigue life of mould is very low.

The H13 steel has good comprehensive mechanical properties, cold-and-heat resistent fatigue property and anti-liquid metal erosion, but its use temperature is answered≤600 ℃, and same DIEVAR steel also is difficult to work under 650 ℃ of conditions.Usually, the actual operating conditions of die steel requires to reach more than 700 ℃.

Therefore, at present in the hot-work die steel field, utilizing the composition homogeneous design, develop a kind of thermostability, good strength and flexible steel grade that has superelevation concurrently, is to be of great significance, and can bring great economic benefit.

Summary of the invention

The purpose of this invention is to provide a kind of hot work die steel with high-heat stability and high-strength and preparation method thereof.

A kind of hot work die steel with high-heat stability and high-strength of the present invention is characterized in that having following composition and weight percent:

C 0.3～0.6％， Si 0.5～0.7％，

Mn 10.5～14.5％， Cr 2.0～6.0％，

Mo 1.5～3.5％， V 0.5～2.0％，

P 0.01～0.02％， S ＜0.005％，

The Fe surplus.

The preparation method of above-mentioned hot work die steel with high-heat stability and high-strength is characterized in that having following technological process and step:

A. melting: by traditional ordinary method melting; To be positioned in the medium-frequency induction furnace by the admixtion that above-mentioned prescription weighing cooperates, under 1500～1700 ℃ of temperature, carry out melting, pour into a mould steel ingot then;

B. esr: above-mentioned ingot is put in the esr device as consumable electrode, carries out secondary refining; Utilize electric current to melt consumable electrode steel alloy mother metal by the electroslag layer heat that has a resistance, liquid metal is frozen into steel ingot more again with in the water mold of molten drop form below the slag blanket of slag bath falls to;

C. high-temperature homogenization: step b gained steel ingot is heated to 1200～1240 ℃, and is incubated 8～10 hours, make the composition of steel homogenizing, prevent component segregation, improve the group of solidifying of steel; Bury sand cooling then but;

D. forge: step c gained steel ingot is heated to 1200～1230 ℃, carries out rough forge subsequently, final forging temperature is 950 ℃, obtains steel forgings;

E. blank forging: above-mentioned steel forgings blank is heated to 1100～1150 ℃ once more, in 950～1100 ℃ of temperature ranges, forges processing once more;

F. annealing: under 830 ℃ of temperature, annealed 8 hours then, to remove the stress that produces in the forging process; Furnace cooling subsequently; Make hot-work die steel;

G. quench treatment: with above-mentioned hot-work die steel after quench treatment; Quenching temperature is 1100～1200 ℃; Its aging temp is 700～800 ℃, and aging time is 2～8 hours.

The theoretical foundation of its design mix prescription of hot-work die steel of the present invention is as described below:

Traditional hot-work die steel organize normally martensite, and martensite at high temperature can decompose, so be difficult at high temperature work.

This steel grade is a kind of high manganese austenite attitude die steel, usually suitable manganese carbon ratio example makes this steel grade remain at the Ovshinsky figure, and forms carbide by adding Cr, Mo, these three kinds of alloying elements of V, in the timeliness heat treatment process, to separate out their carbide, strengthen matrix.

Its using-system is that austenite adds the carbide that disperse is separated out, and be all to keep the Ovshinsky figure in also being to use in heat treatment process, so it has good toughness, and the carbide reinforced matrix of separating out makes matrix hardness reach the mould service requirements.At high temperature separate out just because of these carbide, so this steel grade can at high temperature be worked, it can keep good thermostability under working conditions more than 700 ℃.

Characteristics on the processing method of the present invention are to have adopted electroslag remelting process, and this is the secondary refining technology that the high-quality steel is produced; Utilize the esr device, with the steel ingot mother metal as consumable electrode, utilize electric current to melt consumable electrode steel alloy mother metal by the electroslag layer heat that has a resistance, its liquid metal is frozen into steel ingot more again with in the water mold molten bath of molten drop form below the slag blanket of slag bath falls to.Steel ingot is progressively crystallization from bottom to top.Electroslag remelting process can reduce the content of the inclusion of gas in the steel ingot, deoxidization desulfuration effectively, and can control and solidify, improve the both macro and micro tissue of remelting steel ingot.Therefore electroslag remelting process can obtain composition evenly, dense structure, superior in quality steel ingot.

The hot-work die steel that the inventive method makes has higher Rockwell hardness, good thermostability and has good impelling strength.

Description of drawings

Fig. 1 is the thermostability figure of hot-work die steel of the present invention (being called for short the SDHA steel) under 700 ℃ of conditions.

Fig. 2 be hot-work die steel of the present invention (be called for short SDHA steel) under 700 ℃ of conditions with the thermostability comparison diagram of existing die steel H13 and DIEVAR steel.

Embodiment

After now specific embodiments of the invention being described in.

Embodiment 1: in the present embodiment, adopt the moiety and the weight percent thereof of hot-work die steel as follows:

C 0.51%, and Si 0.64%, and Mn 13.08%, and Cr 5.0%, and Mo 3.13%, and V 1.12%, and P 0.019%, S＜0.004%, Fe surplus.

In the present embodiment, the technological process and the step of hot-work die steel are as follows:

(1) melting: by traditional ordinary method melting; To be positioned in the medium-frequency induction furnace by the admixtion that above-mentioned prescription weighing cooperates, under 1600 ℃ of temperature, carry out melting, pour into a mould steel ingot then;

(2) esr: above-mentioned steel ingot is put in the esr device as consumable electrode, carries out secondary refining; Utilize electric current to melt consumable electrode steel alloy mother metal by the electroslag layer heat that has a resistance, liquid metal is frozen into steel ingot more again with in the water mold of molten drop form below the slag blanket of slag bath falls to;

(3) high-temperature homogenization: step (2) gained steel ingot is heated to 1230 ℃, and is incubated 9 hours, make the composition of steel homogenizing, prevent component segregation, improve the group of solidifying of steel; Bury sand cooling then but;

(4) forge: step (3) gained steel ingot is heated to 1220 ℃, carries out rough forge subsequently, final forging temperature is 950 ℃, obtains steel forgings;

(5) blank forging: above-mentioned steel forgings blank is heated to 1140 ℃ once more, under 1000 ℃ of temperature, forges processing once more;

(6) annealing: under 830 ℃ of temperature, annealed 8 hours then, to remove the stress that produces in the forging process; Furnace cooling subsequently; Make hot-work die steel;

(7) quench treatment: with above-mentioned hot-work die steel after quench treatment; Quenching temperature is 1200 ℃; Its aging temp is 720 ℃, and aging time is 2 hours.

Performance test

Above-mentioned hot-work die steel sample is done performance test, and the result is as follows:

(1) hardness: HRC45.

(2) impact: room temperature is impacted greater than 300J.

(3) thermostability: under 700 ℃ of conditions, do heat stability test, the Fig. 1 in the accompanying drawing is the thermostability line chart of hot-work die steel of the present invention (SDHA steel).

The phraseology of thermostability herein is: alloy steel material is incubated for some time under hot conditions, and the ability that its hardness remains unchanged and promptly do not descend is so reflect with the hardness after the material insulation.

Hot-work die steel of the present invention (SDHA steel) and original H13 steel and DIEVAR steel under 700 ℃ of conditions, the comparison of its thermostability, test-results as shown in Figure 2.

The composition of H13 steel and DIEVAR steel is as shown in the table:

Composition (wt%)	C	Si	Mn	Cr	Mo	V	P	S
									The H13 steel	0.373	0.990	0.270	5.457	1.234	0.990	0.016	0.005
The DIEVAR steel	0.309	0.237	0.485	5.056	2.400	0.598	0.005	0.0004

For H13 and DIEVAR steel, its best Q-tempering technology of respectively asking for is done heat stability test again.

H13 steel heat treatment process: 1100 ℃ of+600 ℃ of tempering 2 hours (2 times) of quenching

DIEVAR steel heat treatment process: 1025 ℃ of+600 ℃ of tempering 2 hours (2 times) of quenching+560 ℃ tempering 2 hours

Test-results

Can find out that from Fig. 2 trial curve H13 steel and DIEVAR steel are under 700 ℃ of conditions, thermostability is very poor, and hot-work die steel of the present invention (SDHA steel) is fine 700 ℃ of condition thermostabilitys.

Claims (1)

1.1. the preparation method of a hot work die steel with high-heat stability and high-strength is characterized in that the composition of this die steel and weight percent are:

C 0.3～0.6％， Si 0.5～0.7％，

Mn 10.5～14.5％，Cr 2.0～6.0％，

Mo 1.5～3.5％ V 0.5～2.0％，

P 0.01～0.02％，S ＜0.005％，

The Fe surplus;

Concrete preparation process is:

A. melting: by traditional ordinary method melting; To be positioned in the medium-frequency induction furnace by the admixtion that above-mentioned prescription weighing cooperates, under 1500～1700 ℃ of temperature, carry out melting, pour into a mould steel ingot then;

B. esr: above-mentioned steel ingot is put in the esr device as consumable electrode, carries out secondary refining; Utilize electric current to melt consumable electrode steel alloy mother metal by the electroslag layer heat that has a resistance, liquid metal is frozen into steel ingot more again with in the water mold of molten drop form below the slag blanket of slag bath falls to;

C. high-temperature homogenization: step b gained steel ingot is heated to 1200～1240 ℃, and is incubated 8～10 hours, make the composition of steel homogenizing, prevent component segregation, improve the solidified structure of steel; Bury sand cooling then but;

D. forge: step c gained steel ingot is heated to 1200～1230 ℃, carries out rough forge subsequently, final forging temperature is 950 ℃, obtains steel forgings;

E. blank forging: above-mentioned steel forgings blank is heated to 1100～1150 ℃ once more, in 950～1100 ℃ of temperature ranges, forges processing once more;

F. annealing: under 830 ℃ of temperature, annealed 8 hours then, to remove the stress that produces in the forging process; Furnace cooling subsequently; Make hot-work die steel;

G. quench treatment: with above-mentioned hot-work die steel after quench treatment; Quenching temperature is 1100～1200 ℃; Its aging temp is 700～800 ℃, and aging time is 2～8 hours.

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