SU1323594A1 - Method of heat treatment of hot-rolled strip for manufacturing articles by cold plastic deformation - Google Patents

Abstract

The invention relates to the field of heat treatment of rolled from hot rolled low carbon low alloy steels. The aim of the invention is to improve the strength of the products. Sheet steel 09G2 is subjected to heating to the temperature of the two-phase region, exposure and stepwise cooling. First, it is cooled in still air to 600-420 ° C, then by a water-air mixture to 90-200 °. At the last cooling stage, after winding up the strip, the coil is delayed cooling to the shop temperature. The final structure of the steel is ferrite-martensitic with / v 20% martensite. The method increases the temporary tensile strength in comparison with the known by 60 MPa, increases the strength characteristics of the finished product: & i f 550 MPa at o, i 250 MPa. 1 ill., 1 tab.

Description

 The invention relates to heat treatment of rolled from hot rolled low carbon low alloy steels and can be used in the manufacture of stamped car parts using cold plastic deformation.

The purpose of the invention is to improve the strength of manufactured products,

The drawing shows the cooling scheme for the proposed method.

The invention is described in the following examples.

Therm1-1 ches 10 is carried out on the processing of steel sheet 09G2 with a chemical compound,%: C 0.10; Si 0.27; Mp 1.54; S 0.025; P 0.021.

Sharp heat treatment of the heat in the unit and the temperature of up to two-phase temperature is holding at this TEM for 8 minutes and step cooling at which the strip cools first at a quiet time ;; to the duct to 600 420 C with i-speed 5 deg / s ,, then. Through the air-cooling system (paBHOi. Iep- but by the strip strip) to 90–200 ° C at a rate similar to that of the last cooling after strip stripping, the coil is slowed down at a rate of -5 C / h to shop temperature, Konevriafi structure has become and thermally): processed but before, lagagomu 5th spasebus is a two-phase ferrite of 1U martensite 10 mixture with, - 20% martensite „

Cooling rate: Determined: A and then the cooling curve. by, g; learn: choy using a pyrometer; - ;.

Compliance with the rpo-speed mode of natura and cooling after a different dosta igalos tolnshpy: by varying the speed and danii strip.

In order to obtain a comparator; s; s: .x; an, they carried out a thermal treatment / according to the proposed: agaim li pzvnotnotchu rzhl-, mom,

The mechanical properties of O1; | food:.:.: -; whether Hci is of transverse specimens, dantse gpeed-avleshl in the table.

The process of manufacturing the product ntiH-Ti-ipoBajiH through deformation by 5% and the subsequent aging process iipx-i 200 C 3 for 1 h about Reshm stary. m corresponds to one} of the 1st of St.-Juv mzgotoz-235943

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The increase in yield strength after deformation and aging consists of 5 of two parts

 deo ,, T,. where L o c is a defensive hardening;

 H clearing as a result

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 - 3 cases of m (2-mi processing in the optimal mode ziiJg software MPa and li cr - 140 MIL-ij, which in cwiMe gives Lb, 250 M1a (see table).

The proposed method of heat treatment increases the temporary increase in rupture compared to the known one on i 60 Ш1. while maintaining a high technological level

yield dates; 5.,) product: c-1 is 550 KPa at 250 I Sfa).

During the tension of the steel to the temperature of the two-phase region, the concentration of carbon in austenite is reduced. which leads to the release in the first stage of the cooling / edeny of a large amount of new orJa-7Xxo; for the plastic ferry)

growth of deformation, ci opocTH about: l; averages less than 3 degrees / s: pearlite decomposition of auste-1ita occurs. Steel with ferritic-pearlite n grz K gura have a higher yield strength and lower temporal resistance of the gap “s compared to ferritic marchis gnie-1 and became consistent with a high value from olusHWHuo-; 6:13 not; :: allegory .gdt materials. predzna.Chesh-1yz: for cold forming. At cooling rates nc higher than 5 ° C / s, ferrous fermentation is impregnated with interstitial impurities and KOj7ti4ecT; 3a of a new ferrite decreases, that s.; 1H} 1s out of the steel. Increase the speed of cooling of the temperate RFGG og. (h 500-420 to 90-200 p.: to the fact that as a result of lok; e:;: HO japTSHCHTHo- transformations oijbfiMOB and you know-c; that residual stresses remain in the structure; h n g turnover value / -i understood; m value; yield point of ferritic-martenspets-al /; .. takhse pony-- from: iOHieiiiie i: ,,., ;;,., Z ve, inchepy

that lead; to the emergence of a yield point. At speeds oh.p; kdeni above 3 ri-ad / h does not have time to emit free nitrogen, which leads to an early steel digestion.

Claims (1)

Invention Formula The method of heat treatment of a hot rolled strip to produce a cooling rate in this temperature range also provides the supersaturation of ferrite with carbon, which is necessary for obtaining sufficient hardening during artificial aging, 5 When the cooling rate is below 10 degrees / sec, the resulting level of internal stresses is insufficient to prevent aging at room temperature. When the cooling rate is higher than cold plastic deformation - 30 degrees / s, the ferrite is oversaturated with pre-days, mainly from low-carbon penetration, which leads to early low-alloy steels, steel re-marking. Including heating up, slow cooling, occurring - holding, cooling with a speed of 1 - with the winding of the strip into a roll (third - 5 deg / s up to 600-420 ° С accelerated cooling rate), dp needed cooling to 200-90 ° С, winding into the coil and the final cooling to the workshop temperature, that is, that with the aim of JIOBH-20 of the strength of the manufactured products, the cooling from teh fflepatyry 600-420 to 200-90 C is produced with speed of 10-30 degrees / s. Increased plasticity of martensite and release of free nitrogen. This cooling stage replaces special long-term heating for tempering. At the rate of cooling of the strip in a roll, hail / h, the stress around martensite is relieved. Offer Gage5 1st 7 Have 9 ten 1 I 12 3 1.4 15 S50 14 944 that lead; to the emergence of a yield point. At speeds oh.p; kdeni above 3 ri-hell / h does not have time to emit free nitrogen, which leads to an early shredding of steel. Products of cold plastic deformation - mainly from low carbon low alloy steels, including heating up to the formula of invention The method of heat treatment of hot-rolled strip for the manufacture of products of cold plastic deformed days, mainly from low-carbon low alloy steels, including heating up to 480 550 60 yn. Wo, yo flff- (r-s) Editor M.Nedoluzhenko Compiled by T.Efimova Tehred A. Kravchuk Order 2934/31 Circulation 549Subscription BNIILI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35., Raushsk nab., d.4 / 5 Production and printing company, Uzhgorod, Projecto st., 4 Proofreader A.Zimokosov