CN101717896A

CN101717896A - High strength and toughness cold working die steel and preparation method thereof

Info

Publication number: CN101717896A
Application number: CN200910200517A
Authority: CN
Inventors: 汪宏斌; 吴晓春; 邓黎辉; 李绍宏
Original assignee: University of Shanghai for Science and Technology
Current assignee: University of Shanghai for Science and Technology
Priority date: 2009-12-22
Filing date: 2009-12-22
Publication date: 2010-06-02
Anticipated expiration: 2029-12-22
Also published as: CN101717896B

Abstract

The invention relates to a novel high-strength toughness cold-working die steel and a preparation method thereof, belonging to the technical field of alloy steel manufacturing technology. The chemical composition and weight percent of the steel of the present invention are: C0.7-1.2%, Si0.5-0.7%, Mn0.7-1.1%, Cr2.3-3.5%, Mo0.4-0.7%, V0.4- 0.7%, Ni0.35-0.5%, Fe balance. The preparation process of the cold work die steel of the present invention is briefly described as follows: mix the raw materials according to the formula, melt the batch materials in an induction furnace, cast them, and then remelt them with electroslag; then forge, anneal, and heat them to 850-950°C Austenitizing, after oil quenching, secondary tempering at 180-200°C. Finally, a high-strength and tough cold-working die steel is obtained. The cold working die steel of the present invention has higher strength and toughness, and higher hardness, and is a steel grade suitable for manufacturing precise and complex dies.

Description

High-toughness cold-work mould steel and preparation method thereof

Technical field

The present invention relates to a kind of novel high-strength toughness cold working die steel and preparation method thereof, belong to the steel alloy manufacturing process technology field.

Background technology

The cold-work die working conditions is quite abominable, requires cold-work die steel to have high-strong toughness and high rigidity and high-wearing feature and cooperates.On the basis that at present both at home and abroad high-strong toughness and low-alloy cold-forming die steel demand is improved constantly, it is good that the present invention has developed hardening capacity, and quenching temperature is lower, and heat treatment deformation is little, have intensity and flexible cooperation preferably, be applicable to and make accurate complicated die steel.

Summary of the invention

The object of the present invention is to provide a kind of high-toughness cold-work mould steel.Another object of the present invention provides a kind of preparation method of high-toughness cold-work mould steel.

A kind of high-toughness cold-work mould steel of the present invention is characterized in that having following composition and weight percent:

C 0.7-1.2％，Si?0.5-0.7％，

Mn?0.7-1.1％，Cr?2.3-3.5％，

Mo?0.4-0.7％，V 0.4-0.7％，

Ni?0.35-0.5％

The Fe surplus.

The preparation method of a kind of high-toughness cold-work mould steel of the present invention is characterized in that this method has following technological process and step:

A. batching and melting: carry out preparation of raw material by above-mentioned prescription weighing, the gained admixtion is put into induction furnace carry out melting; Smelting temperature is 1500～1550 ℃; Be cast into ingot, treat its naturally cooling; Esr: the ESR ingot that the melting pouring is gone out is put in the esr device, carries out esr.

B. esr: the steel ingot after the above-mentioned casting is placed the esr device as consumable electrode, carry out esr; Molten steel falls in the following water mold through the slag blanket of slag bath, is frozen into steel ingot more again.

C. forge: the above-mentioned steel ingot that solidifies again is heated in 1200～1230 ℃ of scopes forges processing; Just forging temperature is 1050～1100 ℃, and final forging temperature is 850～900 ℃;

D. annealing: carry out forged steel material and put into process furnace and anneal with above-mentioned; Annealing temperature is 830～860 ℃, and annealing time is 6～10 hours; After stove is chilled to 550 ℃, the air cooling of coming out of the stove.

E. Q-tempering is handled: with steel material reheat to 850～950 ℃, adopt the oil quenching quench treatment; Carry out double tempering at 180～200 ℃ subsequently and handle, each tempering time is 2 hours; Finally make high-toughness cold-work mould steel.

The theoretical foundation of its composition design of cold-work die steel of the present invention is as described below:

Contain proper C and Cr in this steel, guaranteeing that the ununiformity that matrix has good obdurability and material to have to have avoided carbide on the basis of good hardening capacity simultaneously exists.Minor N i can keep good plasticity and toughness simultaneously in the intensity that improves steel.Mo and V form second precipitate mutually of disperse in steel, the precipitate of these disperses not only can play the precipitation strength effect, and can hinder growing up of austenite crystal effectively, improves the obdurability of material.Si is dissolved in the matrix can improve the temper resistance that matrix strength improves steel simultaneously.Mn is in the process of austenitizing, and major part has been added in the middle of the matrix, has improved the alloy content in the matrix, has strengthened the solution strengthening effect, thereby improves the intensity of matrix.

It is good that the present invention has developed hardening capacity, and quenching temperature is lower, and heat treatment deformation is little, has intensity and flexible cooperation preferably, is applicable to and makes accurate complicated die steel.

Description of drawings

Fig. 1. steel of the present invention is 180 ℃ of tempering temperatures, impelling strength and hardness curve during different quenching.

Fig. 2. steel of the present invention is 930 ℃ of quenchings in thermal treatment process, two hours twice o'clock SEM of 180 ℃ of tempering and organize metallograph.

Fig. 3. both impelling strength and hardness ratio be after thermal treatment process is 1030 ℃ of 200 ℃ of tempering of quenching with the D2 steel after thermal treatment process is 930 ℃ of 180 ℃ of tempering of quenching for steel of the present invention

Embodiment

Now steel specific embodiment of the present invention is described in down.

In this example, adopt the moiety and the weight percent thereof of cold-work die steel as follows:

C?0.73％，Si?0.69％，Mn?0.80％，Cr?2.35％，Mo?0.50％，

V 0.46%, and Ni 0.37%, the Fe surplus.

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

A. induction melting: carry out melting by above-mentioned alloying element proportioning in induction furnace, smelting temperature then is cast into Ф 160mm steel ingot and air cooling greater than 1500 ℃;

B. esr: the steel ingot after the pouring is positioned in the esr device as consumable electrode, carries out esr, liquid metal falls in the following water mold through the slag blanket of slag bath, is frozen into steel ingot more again;

C. forge: above-mentioned steel ingot is heated in 1200～1230 ℃ of temperature ranges forges processing; Final forging temperature 〉=850 ℃.Forge into the square stock of 60mm * 60mm;

D. annealing: the steel material after will forging is put into process furnace and is annealed, and annealing temperature is 860 ℃, and annealing time is 6h, the air cooling of coming out of the stove after stove is chilled to 550 ℃.

E. the temper of quenching: adopting the oil quenching quenching temperature is 930 ℃; Carry out double tempering at 180 ℃ again, each tempering 2 hours;

Finally make high-toughness cold-work mould steel.

Performance test

Cold-work die steel of the present invention carries out performance test through after the above-mentioned thermal treatment:

(1) quenching hardness: 64～65HRC; Tempered-hardness: 61HRC

(2) impelling strength experiment:

Get the impact of collision sample on blank, specimen size is 10mm * 10mm * 55mm.

Room temperature impact toughness value: 127J.

Cold-work die steel of the present invention 930 ℃ quench+180 ℃ of Annealed Strips under with the D2 steel recommending 1030 ℃ of thermal treatment process quench under 200 ℃ of two hours Annealed Strips both impelling strength and hardness ratio, find, the hardness of steel of the present invention is suitable with the D2 steel, and impelling strength aspect steel of the present invention significantly improves than D2 steel.

Claims

1. A high strength and toughness cold work die steel, characterized in that the chemical composition and weight percentage of the steel are: C0.7-1.2%, Si 0.5-0.7%, Mn 0.7-1.1%, Cr 2.3-3.5%, Mo 0.4-0.7%, V 0.4-0.7%, Ni 0.35-0.5%, Fe balance.

2. A method for preparing high-strength and tough cold-work die steel according to claim 1, characterized in that it has the following processes and steps:

a. Batching and smelting: Weigh the raw materials according to the above formula, put the obtained batch into the induction furnace for smelting; the smelting temperature is 1500-1550°C; cast into steel ingots, and let them cool naturally.

b. Electroslag remelting: Place the cast steel ingot as a consumable electrode in the electroslag remelting device for electroslag remelting; the molten steel falls through the slag layer of the slag pool to the water-cooled crystallizer below, Then re-solidified into steel ingots.

c. Forging: heating the above-mentioned re-solidified steel ingot to the range of 1200-1230°C for forging; the initial forging temperature is 1050-1100°C, and the final forging temperature is 850-900°C;

d. Annealing: put the above-mentioned forged steel material into a heating furnace for annealing; the annealing temperature is 830-860°C, and the annealing time is 6-10 hours; after the furnace is cooled to 550°C, it is taken out of the furnace and air-cooled.

e. Quenching and tempering treatment: reheat the steel material to 850-950°C, and adopt oil quenching treatment; then perform secondary tempering treatment at 180-200°C, each tempering time is 2 hours; For mold steel.