CN101805820A

CN101805820A - Prehardening treatment method of plastic mould steel

Info

Publication number: CN101805820A
Application number: CN 201010154447
Authority: CN
Inventors: 陈建礼; 田培凤; 张晓琨; 王之香
Original assignee: Shanxi Taigang Stainless Steel Co Ltd
Current assignee: Shanxi Taigang Stainless Steel Co Ltd
Priority date: 2010-04-22
Filing date: 2010-04-22
Publication date: 2010-08-18

Abstract

The invention relates to a prehardening treatment method of plastic mould steel, which comprises the following steps: controlling the finishing rolling temperature of a medium plate to be 830 to 950 DEG C when in steel rolling, and then straightening a steel plate through a hot straightening machine; cooling the straightened steel plate to the temperature of 350 to 450 DEG C in air, hanging in a slow cooling pit at the temperature of 350 to 450 DEG C, and slowly cooling for 46 to 52 hours to obtain a prehardened medium plate with the hardness of 300 to 380HB. The prehardening treatment method of the plastic mould steel has low cost and short production period.

Description

A kind of Prehardening treatment method of plastic die steel

Technical field

The present invention relates to a kind of Prehardening treatment method of plastic die steel, specifically is a kind of P20 (3Cr2Mo) plastic die steel plate of moderate thickness Prehardening treatment method.

Background technology

Pre-hardening is meant carries out modified (quenching+tempering) processing to obtain the desired use properties of mould in advance with hot worked die steel module or steel plate, do not need to heat-treat again behind the one-tenth mould to be processed and can directly use, thereby can avoid the die deformation and the crack problem that cause owing to thermal treatment.The pre-hardening of P20 (3Cr2Mo) plastic die steel processing at present after being rolled into steel plate and annealing, takes " 850～880 ℃ of oil quenching+580～630 ℃ tempering " modified pre-hardening to handle usually, makes steel plate hardness reach the performance requriements of 280～380HB.The subject matter that this pre-hardening method exists is that pre-hard thermal treatment cost is higher, and the steel plate heat treatment deformation is difficult to control, and the production cycle is longer.

Summary of the invention

In order to overcome the above-mentioned deficiency of the Prehardening treatment method that has plastic die steel now, the invention provides the Prehardening treatment method that a kind of thermal treatment cost is low, shorten the plastic die steel of heat treatment cycle.

It is better that design starting point of the present invention is based on the P20 steel hardenability, the austenite continuous cooling curve of the steel grade of introducing in " moulding stock application manual " book according to China Machine Press's publication as can be seen, behind the P20 austenitizing, speed of cooling is between 200～1500 ℃/h the time, and the hardness of steel can reach 280～376HV (277～369HB).Through reality test, when finishing temperature was 880 ℃, the speed of cooling of different thickness steel plate air cooling to 400 ℃ saw Table 1.

Table 1

Steel plate specification (mm) thickness * wide * length	??30×1800×??6000	??60×1800×??6000	??120×1000×??5000	??180×1000×??5000
Steel plate specification (mm) thickness * wide * length	??30×1800×??6000	??60×1800×??6000	??120×1000×??5000	??180×1000×??5000	Speed of cooling (℃/h)	??1495	??650	??333	??240

According to this steel grade characteristic, can take the production method of " control finishing temperature+air cooling+slow cooling ", carry out the pre-hardening of the P20 plate of moderate thickness of " (30～180) * (1000～2300) * L (unit: mm) " specification limit and handle.

The Prehardening treatment method of this plastic die steel comprises following sequential steps:

During steel rolling the plate of moderate thickness finishing temperature is controlled between 830～950 ℃, by heat rectification machine steel plate is aligned then, straightening temperature 〉=550 ℃, aligning 1～3 road;

Steel plate behind aligning is as cold as 350～450 ℃ in air, hang in 350～450 ℃ burial pit, slow cooling 46～52 hours, speed of cooling≤10 ℃/hour.Can obtain hardness is the pre-hard attitude plate of moderate thickness of 300～380HB.

The Prehardening treatment method of this plastic die steel can be realized the online pre-hardening of P20 plate of moderate thickness, reduces by 1000 yuan of/ton steel of product treatment production cost, and the pre-hardening process for producing cycle that has plastic die steel now was foreshortened to 3 days by 15 days.

Embodiment

Describe the embodiment of the Prehardening treatment method of this plastic die steel in detail below in conjunction with embodiment, but following embodiment not the restriction to the Prehardening treatment method embodiment of this plastic die steel.

Embodiment 1:

The first step: adopt 50 tons of EBT (electric furnace)+60 ton LF (ladle refining)+60 ton VD (vacuum outgas) to smelt the P20 steel, pour into 8 7.2 tons of cast slabs.The quality per distribution ratio of its chemical ingredients sees Table 2.

Table 2

??C	??Si	??Mn	??P	??S	??Cr	??Mo
??C	??Si	??Mn	??P	??S	??Cr	??Mo	??0.36	??0.52	??0.86	??0.014	??0.003	??1.74	??0.36

Second step: 8 steel ingots are heated to 1180 ℃ and be incubated 4 hours in process furnace, adopt the 1000mm reversing two high blooming mill Rolling from Ingot to be made (100～180) * 1000 * (4000～7000) (unit of length: 8 of different thickness steel plates mm) then.The finishing temperature of different size steel plate correspondence, go into the burial pit temperature and see Table 3.

The 3rd step: the steel plate that rolls into is cooled to show the slow cooling temperature in air behind 9 roller heat rectification machines alignings, 400 ℃ the burial pit slow cooling 48 hours of then steel plate being packed into.

The 4th step: the steel plate slow cooling hung out steel plate after 48 hours from burial pit, made its air cooling to room temperature, inspection by sampling steel plate hardness.Hardness Surveillance the results are shown in Table 3.

Table 3

Rolling specs (mm) is thick * wide * long	Finishing temperature ℃	Slow cooling temperature ℃	Steel plate hardness HB
Rolling specs (mm) is thick * wide * long	Finishing temperature ℃	Slow cooling temperature ℃	Steel plate hardness HB	??180×1000×4300	??890	??405	??332
??160×1000×5000	??895	??380	??338	??180×1000×4300	??890	??405	??332
??160×1000×5000	??895	??380	??338	??150×1000×5230	??870	??387	??338
??140×1000×5640	??880	??390	??342	??150×1000×5230	??870	??387	??338
??140×1000×5640	??880	??390	??342	??130×1000×6035	??875	??377	??348
??120×1000×6500	??860	??378	??340	??130×1000×6035	??875	??377	??348
??120×1000×6500	??860	??378	??340	??110×1000×7100	??887	??398	??330
??100×1000×7845	??850	??389	??342	??110×1000×7100	??887	??398	??330

Embodiment 2:

The first step: adopt 70 tons of converter+80 ton LF (ladle refining)+RH (vacuum outgas) to smelt P20 steel one stove, and continuous casting becomes 220 * 1260 * 2150mm specification continuously cast bloom.The quality per distribution ratio of its chemical ingredients sees Table 4.

Table 4

????C	????Si	????Mn	????P	????S	????Cr	????Mo
????C	????Si	????Mn	????P	????S	????Cr	????Mo	????0.37	????0.56	????0.86	????0.007	????0.005	????1.74	????0.38

Second step: continuously cast bloom is heated to 1230 ℃ in continuous furnace, adopt 2300mm two roller broadening milling trains and 2300mm four-roll universal rolling machine that continuously cast bloom is rolled into 6 of the steel plates of different size shown in the table 5, the finishing temperature of different size steel plate correspondence, go into the burial pit temperature and see Table 5.

The 3rd step: the steel plate that rolls into air cooling to 430～450 ℃ behind seven roller heat rectification machines alignings, 450 ℃ the burial pit slow cooling 48 hours of then steel plate being packed into.

The 4th step: from burial pit, hang out steel plate, make its air cooling to room temperature, inspection by sampling steel plate hardness.Hardness Surveillance the results are shown in Table 5.

Table 5

Rolling specs (mm) is thick * wide * long	Finishing temperature ℃	Go into burial pit temperature ℃	Steel plate hardness HB
Rolling specs (mm) is thick * wide * long	Finishing temperature ℃	Go into burial pit temperature ℃	Steel plate hardness HB	????80×1600×4656	????860	????435	????330
????70×1600×5320	????850	????430	????345	????80×1600×4656	????860	????435	????330
????70×1600×5320	????850	????430	????345	????60×1800×5510	????830	????440	????347
????50×1800×6622	????843	????445	????350	????60×1800×5510	????830	????440	????347
????50×1800×6622	????843	????445	????350	????40×1800×8200	????836	????448	????360
????30×1800×11000	????835	????450	????366	????40×1800×8200	????836	????448	????360

Annotate: all the other compositions in table 2 and the table 4 are Fe and unavoidable impurities.

Claims

1. the Prehardening treatment method of a plastic die steel, it comprises following sequential steps:

During steel rolling the plate of moderate thickness finishing temperature is controlled between 830～950 ℃, by heat rectification machine steel plate is aligned then;

Steel plate behind aligning is as cold as 350～450 ℃ in air, hang in 350～450 ℃ burial pit, slow cooling 46～52 hours, and obtaining hardness is the pre-hard attitude plate of moderate thickness of 300～380HB.