CN103276301A - Low-temperature engineering steel with yield strength not lower than 550MPa and production method of engineering steel - Google Patents

Abstract

The invention discloses low-temperature engineering steel with yield strength not lower than 550MPa. The low-temperature engineering steel with yield strength not lower than 550MPa comprises the following components in percentage by weight: 0.04%-0.18% of C, 0.15%-0.50% of Si, 1.63%-2.00% of Mn, not more than 0..015% of P, not more than 0.008% of S, 0.05%-0.12% of Nb+Ti, 0.20%-0.4% of Mo+Cr, and 0.015%-0.05% of Als; the production steps are as follows: smelting and continuously casting to form blank, heating up the casting blank; rolling in a segmented manner by adopting a TMCP (Thermo-Mechanical Control Process); cooling; and straightening for the future use. The low-temperature engineering steel with yield strength not lower than 550MPa disclosed by the invention is not only capable of producing a steel plate with the thickness bigger than 80mm; the steel plate is uniform in tissue performance in the thickness direction, better in low-temperature impact toughness, i.e., impact power being not less than 100J at (-)60 DEG C, suitable for manufacturing engineering machinery that works in an extremely cold environment. The casting blank has center segregation C lower than 1.5 level and center porosity lower than 0.5 level; the low-temperature engineering steel is free of Ni and relatively low in content of Cr, Mo and other micro alloys, so that the cost is greatly lowered; the TMCP is adopted for producing without the processes including thermal treatment, PRC (Pre-stressed Reinforced Concrete), stacking slow-cooling and the like, and any other equipment is not needed to be added, so that the production process is simple and the production efficiency is high.

Description

The cryogenic engineering of a kind of yield strength 〉=550MPa steel and production method thereof

Technical field

The present invention relates to engineering machinery steel and production method thereof, belong to cryogenic engineering steel and the production method thereof of yield strength 〉=550MPa particularly.

Background technology

High-strength engineering machinery uses steel mainly for the manufacture of the engineering machinery structural part, be subjected to the restriction of service condition and weldprocedure, the steel plate of this class purposes not only needs material to have enough intensity, plasticity and welding property, but also require to possess good low-temperature impact toughness, to adapt to open-air operation under the extreme environment.Along with engineering machinery develops to maximization and lightness direction, high-strength engineering machinery is in rising trend with the super-thick steel plate market demand.

Tradition high-intensity high-tenacity super-thick steel plate mainly adopts hardening and tempering process production, to obtain the good martenaging martempering tissue of obdurability, weak point is that energy consumption is big, manufacturing cost is high, the production cycle is long, and is prone to crackle and surface imperfection in the quenching engineering, has reduced lumber recovery.In recent years, various countries develop a series of modified heat treated physical construction high-strength steel that do not need in succession, but the thickness specification is limited, major cause is that special heavy plate thickness direction tissue and performance uniformity are difficult to control, the over-all properties level is also not ideal enough, show that mainly intensity and toughness can not satisfy engineering machinery steel demand, perhaps cause the production cost height, drawbacks such as low-temperature performance and welding property deterioration owing to increase valuable alloy.Therefore, non-modified super-thick steel plate is the master control tissue with ferrite/perlite still at present, and generally needs through normalizing or tempering heat treatment, and intensity and toughness all can not satisfy application demand, and economic and social benefit is not obvious.For accelerating restructuring, promote industrial upgrading, press for the research and development novelty that strengthens super-thick steel plate, the composition design and processes that breaks traditions exploitation limitation.

CN102041438 provides low-alloy high-tensile structural steel Q460C super-thick steel plate and production method thereof, its chemical ingredients: C :≤0.20%, Si :≤0.60%, Mn:1.40 ~ 1.60%, P :≤0.020%, S :≤0.005%, microalloy element (Nb+Ti+V+Ni) :≤0.25%, Als: 〉=0.015%, all the other are Fe and micro impurity element.Rationally select the compound adding of best proportioning of micro alloying element Nb, Ti, V, Ni for use, give full play to precipitation strength and refined crystalline strengthening double effects, under the prerequisite that does not reduce plasticity and toughness, guarantee to make every performance index of pressurized vessel plate to reach the requirement of international 120mm.It is advantageous that the alloying element addition is lower and proportioning is free, thickness has reached more than the 120mm, and its weak point is: adopt the die casting cast to reduce production efficiency with respect to continuous casting process; Adopt normalizing heat treatment technique, increased the production cycle; Aspect of performance, intensity and low-temperature impact toughness are not enough to satisfy large-scale engineering machinery life-time service under low temperature environment, and machine life and construction ability do not have significantly and improve.

The reduce production method of a CN101597673 low-alloy high-strength thick steel plate, the processing parameter of control is: rolling technology: 1150 ~ 1180 ℃ of Heating temperatures, tapping temperature is set in 1080 ~ 1130 ℃, rate of heating is 08 ~ 0.9mm/min, rolling technology adopts the austenite recrystallization district rolling, 950 ~ 1050 ℃ of finishing temperatures; Roll the back process for cooling: adopt the laminar flow cooling, 650 ~ 750 ℃ of final cooling temperatures, 3 ~ 10 ℃/s of rate of cooling.Advantage is: special heavy plate adds an amount of Mn, does not add other alloying element, greatly reduces production cost; Rollingly must not adopt controlled rolling, save energy has been accelerated rhythm of production, does not also need thermal treatment.But intensity and low-temperature impact toughness are too low, inapplicable with make the large-scale engineering machinery that uses under the low temperature environment.

Therefore, the object of the present invention is to provide a kind of thickness more than 80mm, the composition design cost is lower, and simplified manufacturing process is applicable to the high-strength engineering machinery super-thick steel plate that uses under the low temperature environment.

Summary of the invention

The invention reside in provides a kind of thickness more than 80mm, does not need operations such as thermal treatment, RPC, stacking slow cooling, and-60 ℃ of ballistic works are not less than 100J, the cryogenic engineering of the uniform yield strength 〉=550MPa of thickness direction structure property steel and production method thereof.

Realize the measure of above-mentioned purpose:

The cryogenic engineering steel of a kind of yield strength 〉=550MPa, its component and weight percent content are: C:0.04 ~ 0.18 %, Si:0.15 ~ 0.50%, Mn:1.63 ~ 2.00%, P≤0.015%, S≤0.008%, Nb+Ti:0.05 ~ 0.12%, Mo+Cr:0.20 ~ 0.4%, Als:0.015 ~ 0.05%, all the other are Fe and micro impurity element.

Produce the cryogenic engineering steel of a kind of yield strength 〉=550MPa, the steps include:

1) smelting also, continuous casting becomes base;

2) to the strand heating, the control Heating temperature is at 1150 ~ 1200 ℃;

3) adopt the TMCP segmentation rolling: control fs start rolling temperature is at 1050 ~ 1120 ℃. and the accumulative total draft is 40 ~ 50%; Control subordinate phase start rolling temperature is at 820 ~ 860 ℃, and finishing temperature is not less than 760 ℃, and every time draft is not less than 10%, and the accumulative total draft is not less than 33%;

4) cool off, speed of cooling is controlled at 10 ~ 20 ℃/S, and final cooling temperature is 400 ~ 450 ℃;

5) align, the aligning front spring is swung 80 ~ 120S at roller-way;

6) stand-by.

The present invention compared with prior art, can not only produce thickness greater than the steel plate of 80mm, and the structure property of steel plate thickness direction is even, and has better low-temperature impact toughness, namely-60 ℃ ballistic work 〉=100J is applicable to be manufactured on the engineering machinery of working in the extreme cold environment; Strand center segregation C class is below 1.5 grades, and center porosity is below 0.5 grade; Because it is relatively low not contain Ni and Cr, Mo and other microalloy content, cost significantly reduces; Adopt the TMCP explained hereafter, do not need other complicated processing technologies such as thermal treatment, RPC, stacking slow cooling, need not to add any miscellaneous equipment, production technique is simple, the production efficiency height.

Description of drawings

Accompanying drawing is metallographic structure figure of the present invention.

Embodiment

Below the present invention is described in detail:

The present invention tests and adopts the 130t converter smelting, and pours into the continuously cast bloom of 250 ~ 300mm * 1600 ~ 2000mm * L, adopts the rolling test of TMCP technology.

Table 1 is the value tabulation of various embodiments of the present invention and Comparative Examples;

Table 2 is the main technologic parameters tabulation of various embodiments of the present invention and Comparative Examples;

Table 3 is various embodiments of the present invention and the tabulation of Comparative Examples performance monitoring situation.

Various embodiments of the present invention are according to following steps production:

1) smelting also, continuous casting becomes base;

2) to the strand heating, the control Heating temperature is at 1150 ~ 1200 ℃;

3) adopt the TMCP segmentation rolling: control fs start rolling temperature is at 1050 ~ 1120 ℃. and the accumulative total draft is 40 ~ 50%; Control subordinate phase start rolling temperature is at 820 ~ 860 ℃, and finishing temperature is not less than 760 ℃, and every time draft is not less than 10%, and the accumulative total draft is not less than 35%;

4) cool off, speed of cooling is controlled at 10 ~ 20 ℃/S, and final cooling temperature is 400 ~ 450 ℃;

5) align, the aligning front spring is swung 80 ~ 120S at roller-way;

6) stand-by.

The chemical ingredients of table 1 various embodiments of the present invention and Comparative Examples

Annotate: Mo and Cr, Nb and Ti be any value in limited range all, but does not comprise 0.

Table 2 various embodiments of the present invention and Comparative Examples rolling technology significant parameter control (one)

Various embodiments of the present invention all adopt TMCP technology rolling.

Table 2 various embodiments of the present invention and Comparative Examples rolling technology significant parameter control (two)

Table 3 various embodiments of the present invention and Comparative Examples mechanical properties test result

Can analyze from the result of table 3, the steel plate of 80 ~ 100mm thickness that the employing continuous casting that the present invention relates to+TMCP technology is made, yield strength is all more than or equal to 550MPa, and has good low-temperature impact toughness, and-60 ℃ of ballistic works are greater than 100J.

Above-described embodiment only exemplifies for the best, and is not to be restriction to embodiments of the present invention.

Claims (2)

1. the cryogenic engineering steel of a yield strength 〉=550MPa, its component and weight percent content are: C:0.04 ~ 0.18 %, Si:0.15 ~ 0.50%, Mn:1.63 ~ 2.00%, P≤0.015%, S≤0.008%, Nb+Ti:0.05 ~ 0.12%, Mo+Cr:0.20 ~ 0.4%, Als:0.015 ~ 0.05%, all the other are Fe and micro impurity element.

2. produce the cryogenic engineering steel of a kind of yield strength 〉=550MPa as claimed in claim 1, the steps include:

1) smelting also, continuous casting becomes base;

2) to the strand heating, the control Heating temperature is at 1150 ~ 1200 ℃;

3) adopt the TMCP segmentation rolling: control fs start rolling temperature is at 1050 ~ 1120 ℃. and the accumulative total draft is 40 ~ 50%; Control subordinate phase start rolling temperature is at 820 ~ 860 ℃, and finishing temperature is not less than 760 ℃, and every time draft is not less than 10%, and the accumulative total draft is not less than 35%;

4) cool off, speed of cooling is controlled at 10 ~ 20 ℃/S, and final cooling temperature is 400 ~ 450 ℃;

5) align, the aligning front spring is swung 80 ~ 120S at roller-way;

6) stand-by.

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