CN104762563A - Hardened and tempered steel plate production method - Google Patents

Abstract

The invention discloses a hardened and tempered steel plate production method. Chemical components of steel include, by mass, 0.08% to 0.24% of C, 0.20% to 0.50% of Si, 0.80% to 1.30% of Mn, smaller than or equal to 0.018% of P, smaller than or equal to 0.005% of S, smaller than or equal to 0.020% or smaller than or equal to 0.050% of Als, smaller than or equal to 0.25% of Cr, smaller than or equal to 0.08% of Mo, smaller than or equal to 0.25% of Cu, smaller than or equal to 0.25% of Ni, and the balance Fe and remaining elements. The method includes the following processing steps of converter smelting, refining, vacuum refining, casting, heating, rolling, slow cooling and thermal treatment. Through continuous casting blank production, the internal quality of blanks is guaranteed, the low-cost chemical components only with Nb, V and Ti alloy added are selected and used for design, the cleanliness of steel is guaranteed through an LF and VD process, and the sum of the levels of various impurities does not exceed 2.0; through rolling control and normalizing treatment, the grain size of the steel reaches more than 8.0; through the effective implementation of the technical measures, steel plates for a carbon-manganese-silicon pressure container and steel plates guaranteeing flaw detection, the mechanical performance and the plate shape for the carbon-manganese-silicon pressure container are successfully produced.

Description

A kind of production method of hardened and tempered steel plate

Technical field

The invention belongs to steel-smelting technology, be specifically related to a kind of production method of hardened and tempered steel plate.

Technical background

Along with socioeconomic development, the demand of carbon manganese Silicon pressure steel plate for container is increasing.Steel heavy plate for pressure vessels requires that mechanical property is good, safe and reliable.The many employings of prior art adopt quenching+tempering explained hereafter, and the mechanical property of steel is difficult to reach high requirement.

Summary of the invention

The object of the present invention is to provide a kind of production method of hardened and tempered steel plate, comprehensive production technique is particularly adopted to ensure the production method of carbon manganese Silicon pressure container hardened and tempered steel plate, ensure that mechanical property reaches surrender surplus capacity at 50 ~ 80Mpa, tension surplus capacity is at 80 ~ 120Mpa, elongation surplus capacity is 10% ~ 15%, and impact property is even.

The technical scheme of invention:

A kind of production method of hardened and tempered steel plate, the chemical composition mass percent of steel is C=0.08 ~ 0.24, Si=0.20 ~ 0.50, Mn=0.80 ~ 1.30, P≤0.018, S≤0.005, Als≤0.020 ~ 0.050, Cr≤0.25, Mo≤0.08, Cu≤0.25, Ni≤0.25, other are Fe and relict element, comprise following processing step:

A. converter smelting: guarantee tap carbon >=0.05%, P≤0.015%, tapping temperature >=1650 DEG C, point blows number of times≤2 time, avoids tapping process slag;

B. LF refining: take the large quantity of slag to carry out slag making, controls the white slag hold-time at more than 15min;

C. vacuum refinement: refining under the pressure of≤67Pa, dwell time >=25min;

D. cast: the Metal in Tundish cast normal level of liquid degree of depth >=1m, middle bag adds insulating covering agent molding casting;

E. heat: the holding temperature of dead soaking pit controls at 1180 DEG C ~ 1260 DEG C;

F. rolling: adopt the rolling of CR+DQ mode, start rolling temperature 1000 DEG C ~ 1150 DEG C, one-phase finishing temperature > 950 DEG C, single pass draught 30mm ~ 50mm, two-stage start rolling temperature < 900 DEG C, rolling workpiece thickness is greater than 2.5 times of finished product thicknesses, finishing temperature≤860 DEG C, enter water temp and be greater than 800 DEG C, red temperature controls below 450 DEG C;

G. slow cooling: after rolling completes, rolls off the production line and carries out cooling in heap, and release internal stress, ensures plate shape and surface quality;

H. thermal treatment: adopt tempering process, tempering temperature 680 DEG C, soaking time 1 ~ 2min/mm, air cooling is to room temperature.

Inventive principle: C is most basic strengthening element in steel, improves intensity, but C affects the welding property of steel and affects toughness.Consider, the content of carbon controls in a zone of reasonableness.Si is solution strengthening element, favourable to the intensity improving steel plate.Mn is solution strengthening element, all favourable to the intensity and toughness improving steel plate.P is unfavorable to welding, and has certain cold shortness, and in this steel grade, belong to harmful element, what should control is as far as possible low.S easily forms MnS type impurity, has certain red brittleness, in this steel grade, belongs to harmful element, and what should control is as far as possible low.Described guaranteed cost, protect flaw detection and the thickness of plate shape steel plate is 12 ~ 50mm.

The present invention is produced by continuously cast bloom, ensures the internal soundness of blank, selects the low cost chemical composition design of only adding Nb, V, Ti alloy, and LF+VD technique ensures the cleanliness factor of steel, and all kinds of inclusion behavior summation is no more than 2.0.The grain fineness number of steel is made to reach more than 8.0 grades by controlled rolling+normalizing treatment.By effective enforcement of abovementioned technology, successfully produce carbon manganese Silicon pressure steel plate for container and protected flaw detection, protect the carbon manganese Silicon pressure steel plate for container of mechanical property and plate shape.To hot metal pretreatment to the whole production process of steel plate hot process, perform in strict accordance with above-mentioned technique, the quality in kind performance surplus capacity of product is larger, wherein surrender surplus capacity at 50 ~ 80Mpa, tension surplus capacity is at 80 ~ 120Mpa, elongation surplus capacity is 10% ~ 15%, impact property even 15%, and even, the rich amount of impact property is large.

Embodiment

Content of the present invention is further illustrated below in conjunction with embodiment.

The production method of hardened and tempered steel plate, the chemical composition mass percent of steel is C=0.08 ~ 0.24, Si=0.20 ~ 0.50, Mn=0.80 ~ 1.30, P≤0.018, S≤0.005, Als≤0.020 ~ 0.050, Cr≤0.25, Mo≤0.08, Cu≤0.25, Ni≤0.25, and other are Fe and relict element.Comprise following processing step:

A. converter smelting: C >=0.05%, P≤0.015% when controlling to tap, tapping temperature >=1650 DEG C, point blows number of times≤2 time, avoids tapping process slag;

B. LF refining: take the large quantity of slag to carry out slag making, guarantees that the white slag hold-time controls at more than 15min;

C. vacuum refinement: refining under the pressure of≤67Pa, dwell time >=25min;

D. cast: the Metal in Tundish cast normal level of liquid degree of depth >=1m, middle bag adds insulating covering agent molding casting;

E. heat: the holding temperature of dead soaking pit controls at 1180 DEG C ~ 1260 DEG C;

F. rolling: adopt the rolling of CR+DQ mode, start rolling temperature 1000 DEG C ~ 1150 DEG C, one-phase finishing temperature > 950 DEG C, single pass draught 30mm ~ 50mm, two-stage start rolling temperature < 900 DEG C, rolling workpiece thickness is greater than 2.5 times of finished product thicknesses, finishing temperature≤860 DEG C, enter water temp and be greater than 800 DEG C, red temperature controls below 450 DEG C;

G. slow cooling: after rolling completes, rolls off the production line and carries out cooling in heap, and release internal stress, ensures plate shape and surface quality;

H. thermal treatment: adopt tempering process, tempering temperature 680 DEG C, soaking time 1 ~ 2min/mm, air cooling is to room temperature.

As shown in table 1 by the chemical composition of above method rolling carbon manganese Silicon pressure Vessel Steels embodiment 1 ~ embodiment 6, mechanics properties testing result is as shown in table 2.

Table 1 embodiment chemical composition (%)

Table 2 embodiment mechanics properties testing result

The product that embodiment is produced amounts to more than 20000 tons, excellent surface quality, outer inspection qualification rate 100%, flaw detection unification level rate 100%, properties percent of pass 100%.Wherein surrender surplus capacity at 50 ~ 80Mpa, tension surplus capacity is at 80 ~ 120Mpa, and elongation surplus capacity is 10 ~ 15%, and even, the rich amount of impact property is large, and mean value reaches 180J.Meet carbon manganese Silicon pressure steel plate for container development requires.

Claims (1)

1. the production method of a hardened and tempered steel plate, the chemical composition mass percent of steel is C=0.08 ~ 0.24, Si=0.20 ~ 0.50, Mn=0.80 ~ 1.30, P≤0.018, S≤0.005, Als≤0.020 ~ 0.050, Cr≤0.25, Mo≤0.08, Cu≤0.25, Ni≤0.25, other are Fe and relict element, comprise following processing step:

A. converter smelting: guarantee tap carbon >=0.05%, P≤0.015%, tapping temperature >=1650 DEG C, point blows number of times≤2 time, avoids tapping process slag;

B. LF refining: take the large quantity of slag to carry out slag making, the white slag hold-time is at more than 15min;

C. vacuum refinement: refining under the pressure of≤67Pa, dwell time >=25min;

D. cast: the Metal in Tundish cast normal level of liquid degree of depth >=1m, middle bag adds insulating covering agent molding casting;

E. heat: the holding temperature of dead soaking pit controls at 1180 DEG C ~ 1260 DEG C;

F. rolling: adopt the rolling of CR+DQ mode, start rolling temperature 1000 DEG C ~ 1150 DEG C, one-phase finishing temperature > 950 DEG C, single pass draught 30mm ~ 50mm, two-stage start rolling temperature < 900 DEG C, rolling workpiece thickness is greater than 2.5 times of finished product thicknesses, finishing temperature≤860 DEG C, enter water temp and be greater than 800 DEG C, red temperature controls below 450 DEG C;

G. slow cooling: after rolling completes, rolls off the production line and carries out cooling in heap, and release internal stress, ensures plate shape and surface quality;

H. thermal treatment: adopt tempering process, tempering temperature 680 DEG C, soaking time 1 ~ 2min/mm, air cooling is to room temperature.