CN101684532A - Enamel steel for cold rolling water heater and manufacturing method thereof - Google Patents

Abstract

The invention discloses enamel steel for a cold rolling water heater and a manufacturing process thereof. The enamel steel for cold rolling water heater comprises components as follows in percentage by weight: C: 0.01%-0.08%. Si: less than or equal to 0.03%, Mn: 0.10%-0.60%, P: less than or equal to 0.02%, S: 0.003%-0.02%, N: 0.001%-0.006%, AIs: less than or equal to 0.04%, Ti: 0.02%-0.12%, and the balance of ferrum and unavoidable impurities, wherein excess Ti content in steel is equal to Ti-(4*C+3.43*N=1.5S) which is less than or equal to 0. The manufacturing process is characterized in that the heating temperature of billet steel is 1160-1300 DEG C; the hot rolling finish rolling temperature is 850-950 DEG C; the coiling temperature of steel plates is 660-760 DEG C; the cold rolling draft is 60%-80%; the annealing temperature is 760-880 DEG C; the temperature preservation time is 60-200s; rapid cooling speed rate is 15-45 DEG C/s, planishing elongation is 0.7%-1.8%; and surface roughness is 0.7-1.9 micrometres. The invention has the advantages of excellent formability, enamel-spreadable property, pressing resistance, weldability and fish-scaling resistance, stable yield strength after enamelfiring, less cost increase, stable effect and significant economic benefits.

Description

A kind of cold rolling water heater is with Glassed Steel and production method

Technical field

The invention belongs to the steel rolling field, be specially adapted to adopt a kind of cold rolling water heater that is used for the water-heater product that the cold rolled continuous annealing mode produces with Glassed Steel and production method.

Background technology

China in water-heater is produced, adopts the increasing of enamel inner container in recent years.Enamel inner container is because its high-performance aspect anticorrosion, replacing other inner bag and becomes the main force of water heater liner.

Water heater liner by ladle body, go up lower cover three and partly or by upper and lower end socket two partly form, wherein, last lower cover is partly by drawing, ladle body forms by batching, two parts or three parts are carried out pre-treatment, enamel and sintering after welding.Not every steel all are applicable to the application of slip.The water-heater steel plate should satisfy following factor: the application of slip, formability, resistance to pressure and weldability; The steel plate of selecting to use also should have certain scaling resistance energy, will carry out withstand voltage test before water-heater dispatches from the factory, and its method is with after being full of water in the water-heater, pressurization, and pressure is at least the pressure (P is a working pressure) of 1.3P.From 0 to P supercharging, should not be less than 15 seconds, to test pressure 1.3P, be no more than 5 seconds from P, test pressure is kept 15 fens kinds at least.Whole process repeats twice back and observes defectives such as the no squama in surface is quick-fried, crack, is exactly qualified product; Water-heater steel plate weldability is also extremely important in water-heater is produced, because weld defect that welding the time causes such as crack, not seam etc., the capital stays various enamel defects after enamel burns till, it not only influences the Corrosion Protection of product, and serious welding flaw can directly influence the security of products energy.

At present, water-heater producer adopts the SPCC cold-reduced sheet usually.This class steel mainly is ferrite and cementite and a spot of perlite composition, is between 830～860 ℃ in water-heater producer through excess temperature, time is behind 7～15 fens enamel firings, cementite in the steel and a spot of perlite reaustenitizing, ferrite crystal grain after the thermal treatment in the steel is grown up, grain fineness number increases, the yield strength of steel will obviously descend behind the enamel firing, the decline of yield strength has directly influenced the voltage endurance capability of enamel inner container, the voltage endurance capability of steel plate also influences the enamel property of steel plate, and the Glassed Steel of voltage endurance capability difference causes enamel to peel off easily.

Because, the SPCC cold-reduced sheet is before steel mill dispatches from the factory at present, yield strength can not reach 300MPa, therefore, the problem that exists in water-heater producer is the soft partially yield strength deficiency of material, and simultaneously, the carbon content in the steel is too high also will to influence welding property, cause welding property unstable or bad, influence water-heater pressure test effect and scaling resistance.Because water heater liner will have high intensity and good plasticity and weldability, simultaneously, should have certain scaling resistance, have higher yield strength and better unit elongation and fine welding property and the cold rolling Glassed Steel of enamel firing stability so develop, the end socket that this Glassed Steel is widely used in water-heater ladle body and bucket is very necessary.

Summary of the invention

The invention discloses a kind of cold rolling water heater with Glassed Steel and production technique, from the composition to the production technique, control, make it reach the job requirement of water-heater with Glassed Steel according to the particular requirement of Glassed Steel.

The object of the present invention is achieved like this, the composition of steel, by weight percentage: C0.01%～0.08%, Si≤0.03%, Mn0.10%～0.60%, P≤0.02%, S 0.003%～0.02%, N 0.001%～0.006%, Al _S≤ 0.04%, Ti 0.02%～0.12%, and all the other are iron and unavoidable impurities, wherein the superfluous titanium content=Ti-(4*C+3.43*N+1.5S)≤0 in the steel.

The intensity rank requirement is low when being applied to, to the punching press of water-heater producer and Weldability when less demanding:

The composition of steel is by weight percentage: C 0.01%～0.04%, Si≤0.03%, Mn0.10%～0.60%, P≤0.02%, S 0.003%～0.02%, N 0.001%～0.006%, Al _S≤ 0.04%, Ti 0.02%～0.06%, and all the other are iron and unavoidable impurities, wherein the superfluous titanium content=Ti-(4*C+3.43*N+1.5S)≤0 in the steel.

When being applied to intensity rank requirement height, when water-heater producer has good punching press and Weldability:

The composition of steel is by weight percentage: C 0.05%～0.08%, Si≤0.03%, Mn0.10%～0.60%, P≤0.02%, S 0.003%～0.02%, N 0.001%～0.006%, Al _S≤ 0.04%, Ti 0.06%～0.12%, and all the other are iron and unavoidable impurities, wherein the superfluous titanium content=Ti-(4*C+3.43*N+1.5S)≤0 in the steel.

Also contain niobium in the steel of the present invention, content of niobium Nb:0.005%～0.04%.

The present invention is in order to reach good weldability, the plasticity that scaling resistance is become reconciled, and this water-heater adopts soft steel with Glassed Steel, and the carbon content span of control in the steel is 0.01%～0.08%, because carbon content height, the reaction of carbon and oxygen generates gas, when gas is discharged when enamel firing, can cause the enamel coating gas hole defect, the carbon height causes welded heat affecting zone big easily, is unfavorable for the withstand voltage test result, simultaneously, the reduction of carbon content in the steel helps the weldability of this steel.

Low manganese content, manganese content span of control is between 0.10%～0.60%, manganese content mainly is the solution strengthening element, along with manganese content in the steel improves, the intensity of steel improves, and helps grain refining, it is indispensable element in the steel, but the manganese too high levels can cause the banded structure of steel serious, and toughness descends, and is unfavorable for being shaped.

Low silicon, low phosphorus content, silicon, phosphorus content be controlled at 0.03% respectively, below 0.02%, phosphorus content too high easily with steel in Ti reaction formation FePTi, influence the plasticity of steel.

The sulphur content of steel is controlled at below 0.02%, and in order to form certain TiS, the best span of control of sulphur content is 0.003%～0.015%.

N content span of control is below 0.006%.

Sour molten aluminium is controlled at below 0.04% in the steel, and the acid-soluble aluminum content height will be prone to the fishscale defective and will reduce adherence after will making the water-heater enamel firing.

Add certain titanium content in the steel, Ti content span of control is 0.020%～0.12%, and the carbon atom in a part of steel will be separated out the microalloy carbide with the trace amount of titanium effect that adds, and distortion can suppress recrystallize in the high-temperature zone, prevent the high-temperature zone grain coarsening, improve welding property.Titanium plays the precipitation strength effect when cold zone is out of shape, simultaneously, it is the two-phase particle precipitate that forms certain Ti, to enamel is very favourable, because it can combine with various ingredients in the enamel, increase the adherence and the precipitation strength of Glassed Steel, satisfy the water-heater steel and have high extensibility and high yield strength and tensile strength.

Also can add the Nb of trace when adding Ti in the steel, Nb main form with C, N precipitate after thermal distortion exists, and can separate out on dislocation line by strain inducing in austenite, thereby hinder distortion back recrystallize significantly, play the crystal grain thinning effect, improve the yield strength of steel.

Operational path of the present invention is:

Hot metal pretreatment → converter → refining (RH or ANS) → continuous casting → hot continuous rolling → cold-rolling pickling unit → cold rolling → continuous annealing → finishing unit → packing,

Its characteristics are:

Billet heating temperature: 1160～1300 ℃;

Hot rolling finishing temperature: 850～950 ℃;

Coiler plate temperature: 660～760 ℃;

Employing high temperature batches, coiling temperature is between 660 ℃, this be in order to ensure steel can the above hot rolling of recrystallization temperature form tiny and uniform ferrite and big and equally distributed two-phase particle, help reducing steel dislocation desity and two-phase particle accumulation, grow up.

Cold-rolling process is:

The cold rolling draft of total draft: 60%～85%, for guaranteeing the plate shape of rolling back steel plate, final pass should adopt little draft, draft 2%～10%.

Cold rolling draft is formulated, and obtains high R value simultaneously, can obtain high unit elongation.The increase of cold rolling draft increases recrystallize energy storage broken in the tissue after cold rolling, and in cold rolled annealed process, recrystallize forming core particle increases, and the recrystallize time opening in advance.At holding stage subsequently, the time of grain growth prolongs relatively, helps separating out, assembling of second phase, forms favorable texture, obtains good unit elongation and R value.

Annealing temperature: 760～880 ℃;

Soaking time: 60～200s;

Annealing temperature is low excessively, and soaking time is too short, will make recrystallize insufficient, makes crystal grain meticulous, influences the unit elongation of steel;

Slow cooling section temperature out: 630～700 ℃;

Fast cold section temperature out: 360～480 ℃;

Overaging temperature out: 350～470 ℃;

Fast cooling rate rate: 15～45 ℃/s, purpose is that the carbon in the steel is mainly existed with solid solution condition when cold fast, improves the yield strength of steel;

Smooth unit elongation: 0.7%～1.8%;

The roughness span of control of surface of cold-rolled steel plate is 0.7～1.9 μ m.

This roughness span of control helps at high temperature fused enamel body and immerses hackly metallic surface and form cast setting, has strengthened the area that connects of enamel coating and matrix, makes and the level of response increase has improved the adherence at interface.

Because the present invention adopts continuous annealing that speed of cooling is controlled, carbon in the steel is mainly existed in the steel with solid solution condition when cold fast, simultaneously, in steel, added certain Ti, Nb content, on the one hand, a spot of C, N can stop grain growth with the second phase precipitate, play the crystal grain thinning effect, on the other hand, the water-heater steel is handled by the high temperature application of slip in steel mill's following process process, C in the steel, second of N separates out mutually to assemble and grows up, form certain hydrogen trap, moving of the hydrogen atom in the restriction steel makes steel have the quick-fried property of good squama, simultaneously, second separates out mutually and can hinder grain growth, makes steel handle the back grain fineness number in the high temperature application of slip and very big alligatoring can not take place, and the steel plate that the application of slip is handled still keeps high yield strength.

Two-phase particle TiN, the TiS and TiC or TiCN, the TiCS etc. that are organized as thin ferrite and disperse distribution of the present invention's cold-rolled steel after cold rolling thermal treatment.

Advantage of the present invention and effect are, the steel that adopts above-mentioned elemental composition to produce in its processing condition, by to the speed of cooling control of when annealing, carbon in the steel is mainly existed in the steel with solid solution condition when cold fast, simultaneously, in steel, added certain Ti, Nb content, make steel after the high temperature application of slip is handled, C in the steel, second of N separates out mutually and grows up, form certain hydrogen trap, make steel have the quick-fried property of good squama, acquisition has good plasticity, the application of slip, resistance to pressure and weldability and certain scaling resistance energy, and the water-heater steel that yield strength is stable behind the enamel firing, this cold rolling water heater Glassed Steel good pressure-resistant performance, cost increases little, but effect stability, a year economic benefit can reach more than millions of units.

Description of drawings

Fig. 1 is A group metallographic microstructure figure of the present invention;

Fig. 2 is B group metallographic microstructure figure of the present invention.

Embodiment

Introduce the specific embodiment of the present invention below,

The present invention is according to the product innovation purposes, composition to steel is optimized, wherein several elements are divided into two groups of technical schemes, as shown in the table, the intensity rank requirement is low when being applied to, the punching press of water-heater producer and Weldability are adopted the A group when less demanding,, adopt the B group when water-heater producer has good punching press and Weldability when being applied to intensity rank requirement height.

Chemical ingredients (surplus is iron and unavoidable impurities, wt, %)

	??C	??Si	??Mn	??P	??S	??N	??Al S	??Ti	??Nb
										??A	??0.01～ ??0.04	??≤ ??0.03	??0.10～ ??0.60	??≤ ??0.02	??0.003 ??～ ??0.02	??0.001 ??- ??0.006	??≤ ??0.04	??0.02 ??～ ??0.06	??≤ ??0.04
??B	??0.05～ ??0.08	??≤ ??0.03	??0.10～ ??0.60	??≤ ??0.02	??0.003 ??～ ??0.02	??0.001 ??～ ??0.006	??≤ ??0.04	??0.06 ??～ ??0.12	??≤ ??0.04

Wherein: the superfluous titanium content=Ti-(4*C+3.43*N+1.5S)≤0 in the steel.

Operational path of the present invention is:

Hot metal pretreatment → converter → refining (RH or ANS) → continuous casting → hot continuous rolling → cold-rolling pickling unit → cold rolling → continuous annealing → finishing unit → packing,

In order to reach its goal of the invention, the present invention improves some technologies wherein, wherein:

The control of hot rolling technology:

Billet heating temperature: 1160～1300 ℃.

Hot rolling finishing temperature: 850～950 ℃

Coiler plate temperature: 660～760 ℃

Employing high temperature batches, coiling temperature between 660 ℃, this be in order to ensure steel can the above hot rolling of recrystallization temperature form tiny and uniform ferrite and big and equally distributed two-phase particle.Be beneficial to the dislocation desity and the two-phase particle accumulation that reduce steel, grow up.

The control of cold-rolling process:

Cold rolling draft: 60%～85%, for guaranteeing the plate shape of rolling back steel plate, final pass adopts little draft, draft 2%～10%.

Cold rolling draft is formulated, and obtains high R value simultaneously, can obtain high unit elongation.The increase of cold rolling draft increases recrystallize energy storage broken in the tissue after cold rolling, and in cold rolled annealed process, recrystallize forming core particle increases, and the recrystallize time opening in advance.At holding stage subsequently, the time of grain growth prolongs relatively, helps obtaining separating out, assembling of the big crystal grain and second phase, forms favorable texture, obtains good unit elongation and R value.

Thermal treatment process control:

Annealing temperature: 760～880 ℃;

Soaking time: 60～200s;

Annealing temperature is low excessively, and soaking time is too short, will make recrystallize insufficient, makes crystal grain meticulous, influences the unit elongation of steel;

Slow cooling section temperature out: 630～700 ℃;

Fast cold section temperature out: 360～480 ℃;

Overaging temperature out: 350～470 ℃;

Fast cooling rate rate: 15～45 ℃/s, purpose is that the carbon in the steel is mainly existed with solid solution condition when cold fast, improves the yield strength of steel;

Smooth unit elongation: 0.7%～1.8%;

The roughness span of control of surface of cold-rolled steel plate is 0.7～1.9 μ m.

After the cold rolling thermal treatment, two-phase particle TiN, the TiS and TiC or TiCN, the TiCS etc. that are organized as thin ferrite and disperse distribution of steel.

Be several groups of specific embodiments of the invention below

(surplus is iron and unavoidable impurities wt to table 1 chemical ingredients, %)

Sequence number	??C	??Si	??Mn	??P	??S	??Als	??Ti	??N	??Nb
										??1	??0.022	??0.02	??0.52	??0.009	??0.004	??0.022	??0.043	??0.0024
??2	??0.025	??0.02	??0.19	??0.008	??0.006	??0.033	??0.049	??0.0034
										??3	??0.034	??0.01	??0.34	??0.010	??0.012	??0.024	??0.050	??0.0023
??4	??0.031	??0.01	??0.18	??0.012	??0.011	??0.027	??0.032	??0.0018
										??5	??0.018	??0.02	??0.42	??0.013	??0.009	??0.035	??0.031	??0.0027
??6	??0.015	??0.01	??0.31	??0.008	??0.011	??0.031	??0.042	??0.0027	??0.029
										??7	??0.062	??0.02	??0.25	??0.010	??0.007	??0.026	??0.071	??0.0029	??0.013
??8	??0.037	??0.01	??0.51	??0.009	??0.013	??0.034	??0.025	??0.0019	??0.032
										??9	??0.052	??0.01	??0.18	??0.013	??0.012	??0.025	??0.072	??0.0024
??10	??0.055	??0.02	??0.29	??0.009	??0.013	??0.037	??0.089	??0.0021
										??11	??0.058	??0.01	??0.32	??0.007	??0.010	??0.022	??0.084	??0.0027
??12	??0.070	??0.01	??0.48	??0.011	??0.013	??0.025	??0.097	??0.0017

Table 2 hot-rolled temperature system

Sequence number	Hot rolling finishing temperature (℃)	The hot rolling reeling temperature (℃)
			??1	??905	??703
??2	??897	??695
			??3	??877	??691
??4	??919	??713
			??5	??904	??702
??6	??892	??683
			??7	??899	??694
??8	??921	??715
			??9	??915	??707
??10	??917	??722
			??11	??923	??705
??12	??881	??687

Table 3 cold-rolling process parameter

Sequence number	Soaking temperature (℃)	Soaking time (S)	The slow cooling section temperature out (℃)	Fast cold section temperature out (℃)	The overaging temperature out (℃)	Fast cooling rate rate (℃/s)	Smooth unit elongation (%)
								??1	??785	??82	??652	??415	??402	??27	??0.72
??2	??787	??91	??643	??403	??389	??27	??1.18
								??3	??796	??93	??654	??432	??408	??26	??1.16
??4	??802	??78	??667	??461	??425	??29	??1.17
								??5	??828	??95	??662	??423	??406	??29	??1.52
??6	??817	??74	??656	??399	??387	??37	??1.43
								??7	??805	??91	??652	??428	??399	??28	??1.23
??8	??823	??73	??646	??375	??366	??41	??1.27
								??9	??785	??109	??655	??429	??391	??20	??0.91
??10	??822	??101	??651	??433	??404	??28	??0.77
								??11	??812	??79	??693	??466	??427	??32	??1.55
??12	??796	??105	??647	??435	??416	??24	??1.31

Implement the back effect:

Table 4 actual performance

Sequence number	Yield strength	Tensile strength	Unit elongation
				??1	??368	??437	??33
??2	??320	??387	??39
				??3	??345	??390	??36.5
??4	??316	??394	??38
				??5	??363	??434	??32
??6	??409	??468	??29
				??7	??401	??457	??26
??8	??399	??465	??28
				??9	??357	??431	??32.5
??10	??389	??461	??27
				??11	??401	??484	??28
??12	??402	??487	??25

Satisfied the user to cold rolling water heater steel requirement.

2, simulation water-heater steel is 850 ℃ of insulations down, and soaking time contrast properties data see Table 5

Performance data after the different soaking time of table 5 is handled

Sequence number	Yield strength (MPa)	Tensile strength (MPa)	Unit elongation (%)	Soaking time (branch)	Grain fineness number
							??1	??350	??400	??36	??0	8.0 level	See Fig. 1
??2	??315	??345	??34	??20	7.5 level	See Fig. 2

Claims (5)

1, a kind of cold rolling water heater Glassed Steel, it is characterized in that, the composition of steel is by weight percentage: C 0.01%～0.08%, Si≤0.03%, Mn 0.10%～0.60%, P≤0.02%, S0.003%～0.02%, N 0.001%～0.006%, Als≤0.04%, Ti 0.02%～0.12%, all the other are iron and unavoidable impurities, wherein the superfluous titanium content=Ti-(4*C+3.43*N+1.5S)≤0 in the steel.

2, a kind of cold rolling water heater Glassed Steel according to claim 1, it is characterized in that, the composition of steel is by weight percentage: C 0.01%～0.04%, Si≤0.03%, Mn0.10%～0.60%, P≤0.02%, S 0.003%～0.02%, N 0.001%～0.006%, Als≤0.04%, Ti 0.02%～0.06%, all the other are iron and unavoidable impurities, wherein the superfluous titanium content=Ti-(4*C+3.43*N+1.5S)≤0 in the steel.

3, a kind of cold rolling water heater Glassed Steel according to claim 1, it is characterized in that, the composition of steel is by weight percentage: C 0.05%～0.08%, Si≤0.03%, Mn0.10%～0.60%, P≤0.02%, S 0.003%～0.02%, N 0.001%～0.006%, Als≤0.04%, Ti 0.06%～0.12%, all the other are iron and unavoidable impurities, wherein the superfluous titanium content=Ti-(4*C+3.43*N+1.5S)≤0 in the steel.

4, according to each described a kind of cold rolling water heater Glassed Steel in the claim 1～3, it is characterized in that, also contain niobium, content of niobium Nb:0.005%～0.04% in the steel.

5, each described a kind of cold rolling water heater of a kind of production claim 1-4 production technique of Glassed Steel, its technical process is hot metal pretreatment → converter → refining (RH or ANS) → continuous casting → hot continuous rolling → cold-rolling pickling unit → cold rolling → continuous annealing → finishing unit → packing, it is characterized in that

Billet heating temperature: 1160～1300 ℃;

Hot rolling finishing temperature: 850～950 ℃;

Coiler plate temperature: 660～760 ℃;

Cold-rolling process is:

The cold rolling draft of total draft: 60%～85%, final pass adopts little draft, draft 2%～10%;

Annealing temperature: 760～880 ℃;

Soaking time: 60～200s;

Slow cooling section temperature out: 630～700 ℃;

Fast cold section temperature out: 350～480 ℃;

Overaging temperature out: 340～470 ℃;

Fast cooling rate rate: 15～45 ℃/s;

Smooth unit elongation: 0.7%～1.8%;

The roughness span of control of surface of cold-rolled steel plate is 0.7～1.9 μ m.

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