CN103981447B - A kind of low cost is without Mo plastic die steel steel plate and production technique thereof - Google Patents

Abstract

The present invention relates to a kind of low cost without Mo plastic die steel steel plate and production technique thereof, comprise the chemical composition composition of following weight percent content: C:0.36 ~ 0.42%, Si:0.26 ~ 0.34%, Mn:0.55 ~ 0.59%, P≤0.020%, S≤0.010%, Cr:1.25 ~ 1.55%, Nb:0 ~ 0.015%, B:0.0015 ~ 0.0025%, all the other are Fe and inevitable impurity, wherein Cr/Mn is 2.1 ~ 2.6, Si+Cr+Mn is 2.1% ~ 2.4%.The present invention adopts hot rolling+press quenching+tempering process, and steel plate is organized as martensite, martensite+bainite or martensite+bainite+a small amount of perlite, and hardness is 28 ~ 34HRC.The present invention is not containing precious alloys such as Mo, and technique is simple, and the cycle is short, and cost is low, can be widely used in various mould of plastics.

Description

A kind of low cost is without Mo plastic die steel steel plate and production technique thereof

Technical field

The present invention relates to a kind of plastic die steel steel plate, particularly a kind of low cost is without Mo plastic die steel steel plate and production technique thereof, belongs to plastic die steel field.

Background technology

Mould is the underlying process equipment of Industrial products batch production, and machine building industry part rough machined 70%, accurately machined 5% all needs mould.Plastic die steel is important moulding stock, is widely used in all kinds of industry such as household electrical appliance, electronics and communication equipment, plastics, automobile and motorcycle.

Along with advancing by leaps and bounds of world steel output, rising violently of the raw material metal prices such as Mo, Ni, V, causes the price of plastic die steel also constantly to rise thereupon.Developing low-cost is without Mo and hardness becomes the important topic of current die steel manufacturing enterprise at the Steel for Plastic Die of 28 ~ 34HRC.

The manufacture patent of existing many plastic die steel steel plates at present, from composition, patent CN101792886A, CN102286698A, CN101002638A, CN101956136A, CN102312168A, CN102899571A etc., Mo all containing 0.1 ~ 1.0% different content in its composition, from existing market price, adds the Mo only cost of alloy just need 180 yuan/ton of 0.1%, under the large market of the general great loss of steel industry, the ton steel new profit of 180 yuan then can make an iron and steel enterprise make a profit instead of suffering a loss rapidly.From technique, in the patent of current existing plastic die steel steel plate or currently available products, a part adopts die casting process, as patent CN102899571A; A part adopts forging process, as patent CN102650021A, CN102877001A, CN101967608A, CN102796959A etc.; Some is then adopt off-line heat-treating methods, as patent CN103510023A, adopts+200 DEG C of tempering of 855 ~ 875 DEG C of oil quenchings, patent CN103397261A, adopts 830 ~ 880 DEG C of normalizings+500 ~ 550 DEG C of tempering.No matter be die casting, forging or off-line thermal treatment, its production cycle is longer, and production efficiency is low, and the operations such as the casting simultaneously had more, forging, quenching, normalizing make production cost sharply rise.

Summary of the invention

The object of the invention is to propose a kind of low cost without Mo plastic die steel steel plate and production technique thereof.The present invention breaks through traditional moulds Steel Alloy Design Mode, not containing Mo alloy, by the inexpensive alloy such as rational Match Si, Cr, Mn, Nb, B element, adopt hot rolling+press quenching+tempering process, obtaining hardness on whole thickness direction is the die steel of 28 ~ 34HRC; Meanwhile, as thickness≤40mm, martensite is organized as; When thickness is 41 ~ 80mm, be organized as martensite+bainite; When thickness is 81 ~ 140mm, be organized as martensite+bainite+a small amount of perlite.

For achieving the above object, the present invention adopts following technical scheme:

Described steel plate chemical composition is by weight percentage composed as follows: C:0.36 ~ 0.42%, Si:0.26 ~ 0.34%, Mn:0.55 ~ 0.59%, P≤0.020%, S≤0.010%, Cr:1.25 ~ 1.55%, Nb:0 ~ 0.015%, B:0.0017 ~ 0.0023%, all the other are Fe and inevitable impurity, wherein Cr/Mn is 2.1 ~ 2.6, Si+Cr+Mn is 2.1% ~ 2.4%.

Below the effect of component contained in low cost plastic die steel steel plate of the present invention and the selection concrete analysis of consumption thereof are illustrated:

The hardness of C:C to material plays an important role.The content of C controls too low (as lower than 0.030%), then can not proof strength, during too high levels (as higher than 0.50%), then and welding property and the more difficult control of low-temperature flexibility.In the present invention, C content is selected 0.36 ~ 0.42%, can ensure certain hardness.

Si: play deoxidation and solution strengthening effect in steel, can increase the intensity of material, and therefore the content of Si controls 0.26 ~ 0.34%.

Mn:Mn can improve the hardening capacity of steel, and plays solution strengthening effect, but excessive Mn will form segregation in steel plate, severe exacerbation steel plate homogeneity in a thickness direction.Therefore the content of Mn controls 0.55 ~ 0.59%.

Cr:Cr is one of strengthening element important in steel, and perlitic transformation curve can be made to the right upwards to move, and its segregation tendency is little compared with Mn.Cr and Mn coordinates, and effectively can improve the hardenability of steel.Therefore the content of Cr controls 1.25 ~ 1.55%.Si, Mn, Cr compound adds the hardening capacity that can improve steel plate, when Cr/Mn ratio is 2.1 ~ 2.6, when Si+Mn+Cr is 2.1% ~ 2.4%, steel plate can be made in the thick scope of≤80mm to obtain martensite or martensite+bainite structure, thickness is when 81 ~ 140mm, only there is a small amount of perlite in heart portion, hardness is 28 ~ 34HRC simultaneously.

Adding of Nb:Nb can improve austenite non-recrystallization temperature, and the follow-up whole operation of rolling is all completed at Unhydrated cement.Nb can also play Grain refinement.The content of Nb controls 0 ~ 0.015%.

B:B can improve the hardening capacity of steel plate, but excessive B easily causes segregation, and therefore B content controls 0.0017 ~ 0.0023%.

P, S:P, S are the harmful element in steel, and it is more low better to require in theory, but considers the reasons such as steel-making cost, control P≤0.020%, S≤0.010%.

Low cost is without a production technique for Mo plastic die steel steel plate, and it comprises the steps:

(1) according to chemical component weight per-cent according to claim 1, smelt with 180 tons of converters, continuous casting becomes the continuously cast bloom of 220mm or 320mm (thick) × 1800 ~ 2700mm (wide) × 2600 ~ 4800mm (length), continuously cast bloom substance≤30 ton;

(2) in heating process, continuous blank heating temperature is 1170 ~ 1210 DEG C, type of heating is incubated 30min with after the heating rate to 800 of 10 ~ 20 DEG C/min DEG C, continues heating, is warming up to 1170 ~ 1210 DEG C of insulation 60 ~ 90min with the speed of≤10 DEG C/min;

(3) in hot-rolled process, by the slab after soaking, 5m wide and heavy plate mill adopt ordinary hot roll process be rolled into the steel plate of 15 ~ 140mm (thick) × 2000 ~ 4800 (wide) × 6000 ~ 20000 (length), the thick production board of wherein≤70mm is by the thick continuous casting billet milling of 220mm, and the production board that 71 ~ 140mm is thick is formed by the thick continuous casting billet milling of 320mm;

(4) in hot-rolled process, hot-rolled temperature is 980 ~ 1120 DEG C, and pass deformation rate is more than or equal to 15%; Roll rear direct employing MULPIC water cooling system and carry out press quenching, divide two-stage cooling, first 1/4 section adopts low-pressure water to carry out precooling, cooling rate is < 15 DEG C/s, latter 3/4 section adopts high pressure water to cool fast, cooling rate > 25 DEG C/s, final cooling temperature≤180 DEG C, to be placed on cold bed slow cooling to room temperature.Employing two benches cools, and its objective is that the cooling rate reducing surface of steel plate and heart portion is poor, thus reduces the difference of hardness in steel plate thickness direction, prevents steel plate from ftractureing because quenching produces internal stress simultaneously.

(5) in tempering process, as thickness of slab≤40mm, tempering temperature is chosen for 570 ~ 590 DEG C; When thickness of slab is 41 ~ 80mm, tempering temperature is chosen for 540 ~ 560 DEG C; When thickness of slab is 81 ~ 140mm, tempering temperature is chosen for 500 ~ 530 DEG C; Type of heating is incubated after being warming up to target temperature with the speed of 10 ~ 20 DEG C/min, and soaking time is 2 ~ 2.5min/mm+10 ~ 40min.

The present invention, owing to have employed above technical scheme, makes it compared with prior art, has the following advantages and positively effect:

1, composition is simple, and not containing precious alloys such as Mo, Ni, V, cost of alloy is extremely low; Adopt hot rolling+press quenching+tempering process, rolling technology is simple, and process window is comparatively large, and without the need to controlled rolling, without the need to quenching or normalizing thermal treatment in subsequent heat treatment, only need tempering, process costs is lower.Whole technical process is simple, and with short production cycle, efficiency is high.

2, in whole thickness range (15 ~ 140mm), all adopt same composition, same hot rolling technology, the hardness of steel plate of die steel is adjusted by means of only the cooling rate in fine setting press quenching technique, tempering temperature and time, different thickness steel plate hardness is obtained unified, reach the object of Flexible Production, thus reduce production cost.During by this composition and explained hereafter, as thickness≤40mm, be organized as martensite; When thickness is 41 ~ 80mm, be organized as martensite+bainite; When thickness is 81 ~ 140mm, be organized as martensite+bainite+a small amount of perlite, on whole thickness direction, hardness is 28 ~ 34HRC.

Accompanying drawing explanation

Fig. 1 is the microstructure picture at embodiment 1 light plate cross section 1/8,1/4,1/2 place;

Fig. 2 is the microstructure picture at embodiment 2 light plate cross section 1/8,1/4,1/2 place;

Fig. 3 is the microstructure picture at embodiment 3 light plate cross section 1/8,1/4,1/2 place;

Embodiment

Below in conjunction with accompanying drawing and some preferred embodiments, technical scheme of the present invention is described in further detail, but is not limited thereto.

Embodiment 1

This steel (wt%) composed of the following components: C:0.39%, Si:0.30%, Mn:0.58%, P≤0.020%, S≤0.010%, Cr:1.25 ~ 1.55%, Nb:0 ~ 0.015%, B:0.0020%, all the other are Fe and inevitable impurity, wherein Cr/Mn is 2.1 ~ 2.6, Si+Cr+Mn is 2.1% ~ 2.4%.

(1) according to above-mentioned chemical component weight per-cent, smelt with 180 tons of converters, continuous casting becomes the continuously cast bloom of 220mm;

(2) in heating process, continuous blank heating temperature is 1170 ~ 1210 DEG C, type of heating is incubated 15min with after the heating rate to 800 of 10 ~ 20 DEG C/min DEG C, continue heating, 1170 ~ 1210 DEG C of insulation 60 ~ 90min are warming up to the speed of≤5 DEG C/min, by the slab after soaking, 5m wide and heavy plate mill adopt hot rolling technology be rolled into the thick Wide and Thick Slab of 30mm;

(3) in hot-rolled process, hot-rolled temperature is 980 ~ 1120 DEG C, and pass deformation rate is more than or equal to 15%; Roll rear direct employing MULPIC water cooling system and carry out press quenching, divide two-stage cooling, first 1/4 section adopts low-pressure water to carry out precooling, cooling rate is < 15 DEG C/s, latter 3/4 section adopts high pressure water to cool fast, cooling rate > 25 DEG C/s, final cooling temperature≤180 DEG C, to be placed on cold bed slow cooling to room temperature.

(4) in tempering process, tempering temperature is chosen for 570 ~ 590 DEG C, and type of heating is be incubated after being warming up to target temperature with the speed of 10 ~ 20 DEG C/min, and soaking time is 2 ~ 2.5min/mm+10 ~ 40min.

Embodiment 2

This steel C:0.39%, Si:0.30%, Mn:0.58%, P composed of the following components≤0.020%, S≤0.010%, Cr:1.25 ~ 1.55%, Nb:0 ~ 0.015%, B:0.0020%, all the other are Fe and inevitable impurity, wherein Cr/Mn is 2.1 ~ 2.6, Si+Cr+Mn is 2.1% ~ 2.4%.

(1) according to above-mentioned chemical component weight per-cent, smelt with 180 tons of converters, continuous casting becomes the continuously cast bloom of 220mm;

(2) in heating process, continuous blank heating temperature is 1170 ~ 1210 DEG C, type of heating is incubated 15min with after the heating rate to 800 of 10 ~ 20 DEG C/min DEG C, continue heating, 1170 ~ 1210 DEG C of insulation 60 ~ 90min are warming up to the speed of≤5 DEG C/min, by the slab after soaking, 5m wide and heavy plate mill adopt hot rolling technology be rolled into the thick Wide and Thick Slab of 70mm;

(3) in hot-rolled process, hot-rolled temperature is 980 ~ 1120 DEG C, and pass deformation rate is more than or equal to 15%; Roll rear direct employing MULPIC water cooling system and carry out press quenching, divide two-stage cooling, first 1/4 section adopts low-pressure water to carry out precooling, cooling rate is < 15 DEG C/s, latter 3/4 section adopts high pressure water to cool fast, cooling rate > 25 DEG C/s, final cooling temperature≤180 DEG C, to be placed on cold bed slow cooling to room temperature.

(4) in tempering process, tempering temperature is chosen for 540 ~ 560 DEG C, and type of heating is be incubated after being warming up to target temperature with the speed of 10 ~ 20 DEG C/min, and soaking time is 2 ~ 2.5min/mm+10 ~ 40min.

Embodiment 3

This steel (wt%) composed of the following components: C:0.39%, Si:0.30%, Mn:0.58%, P≤0.020%, S≤0.010%, Cr:1.25 ~ 1.55%, Nb:0 ~ 0.015%, B:0.0020%, all the other are Fe and inevitable impurity, wherein Cr/Mn is 2.1 ~ 2.6, Si+Cr+Mn is 2.1% ~ 2.4%.

(1) according to chemical component weight per-cent according to claim 1, smelt with 180 tons of converters, the continuously cast bloom that continuous casting becomes 320mm thick;

(2) in heating process, continuous blank heating temperature is 1170 ~ 1210 DEG C, type of heating is incubated 30min with after the heating rate to 800 of 10 ~ 20 DEG C/min DEG C, continue heating, 1170 ~ 1210 DEG C of insulation 60 ~ 90min are warming up to the speed of≤10 DEG C/min, by the slab after soaking, 5m wide and heavy plate mill adopt hot rolling technology be rolled into the thick Wide and Thick Slab of 105mm;

(3) in hot-rolled process, hot-rolled temperature is 980 ~ 1120 DEG C, and pass deformation rate is more than or equal to 15%; Roll rear direct employing MULPIC water cooling system and carry out press quenching, divide two-stage cooling, first 1/4 section adopts low-pressure water to carry out precooling, cooling rate is < 15 DEG C/s, latter 3/4 section adopts high pressure water to cool fast, cooling rate > 25 DEG C/s, final cooling temperature≤180 DEG C, to be placed on cold bed slow cooling to room temperature.

(5) in tempering process, tempering temperature is chosen for 500 ~ 530 DEG C, and type of heating is be incubated after being warming up to target temperature with the speed of 10 ~ 20 DEG C/min, and soaking time is 2 ~ 2.5min/mm+10 ~ 40min.

The plastic die steel scale of hardness that table 1 embodiment of the present invention 1-3 relates to

Claims (2)

1. a low cost is without Mo plastic die steel steel plate, it is characterized in that, described steel plate chemical composition is by weight percentage composed as follows: C:0.36 ~ 0.42%, Si:0.26 ~ 0.34%, Mn:0.55 ~ 0.59%, P≤0.020%, S≤0.010%, Cr:1.25 ~ 1.55%, Nb:0 ~ 0.015%, B:0.0017 ~ 0.0023%, all the other are Fe and inevitable impurity, wherein Cr/Mn is 2.1 ~ 2.6, Si+Cr+Mn is 2.1% ~ 2.4%, during steel plate thickness≤40mm, be organized as martensite; When thickness is 41 ~ 80mm, be organized as martensite+bainite; When thickness is 81 ~ 140mm, be organized as martensite+bainite+a small amount of perlite, on whole thickness direction, hardness is 28 ~ 34HRC.

2. a kind of low cost, without the production technique of Mo plastic die steel steel plate, is characterized in that described production technique comprises the following steps according to claim 1:

(1) smelt with converter, continuous casting becomes the continuously cast bloom of thick 220mm or 320mm × wide 1800 ~ 2700mm × length 2600 ~ 4800mm, continuously cast bloom substance≤30 ton;

(2) in heating process, continuous blank heating temperature is 1170 ~ 1210 DEG C, type of heating is incubated 15min with after the heating rate to 800 of 10 ~ 20 DEG C/min DEG C, continues heating, is warming up to 1170 ~ 1210 DEG C of insulation 60 ~ 90min with the speed of≤5 DEG C/min;

(3) in hot-rolled process, by the slab after soaking, 5m wide and heavy plate mill adopt ordinary hot roll process be rolled into the steel plate of thick 15 ~ 140mm × wide 2000 ~ 4800mm × length 6000 ~ 20000mm, the thick production board of wherein≤70mm is by the thick continuous casting billet milling of 220mm, and the production board that 71 ~ 140mm is thick is formed by the continuous casting billet milling that 320mm is thick;

(4) in hot-rolled process, hot-rolled temperature is 980 ~ 1120 DEG C, and pass deformation rate is more than or equal to 15%; Roll rear direct employing MULPIC water cooling system and carry out press quenching, divide two-stage cooling, first 1/4 section adopts low-pressure water to carry out precooling, cooling rate is < 15 DEG C/s, latter 3/4 section adopts high pressure water to cool fast, cooling rate > 25 DEG C/s, final cooling temperature≤180 DEG C, to be placed on cold bed slow cooling to room temperature;

(5) in tempering process, as thickness of slab≤40mm, tempering temperature is chosen for 570 ~ 590 DEG C; When thickness of slab is 41 ~ 80mm, tempering temperature is chosen for 540 ~ 560 DEG C; When thickness of slab is 81 ~ 140mm, tempering temperature is chosen for 500 ~ 530 DEG C; Type of heating is incubated after being warming up to target temperature with the speed of 10 ~ 20 DEG C/min, and soaking time is 2 ~ 2.5min/mm+10 ~ 40min.