CN103993236A - Economic type core rod alloy steel and preparation and heat treatment method thereof - Google Patents

Abstract

The invention relates to an economic type core rod alloy steel and a preparation and heat treatment method thereof, belongs to the technical field of alloy steel manufacturing process, and is characterized in that the alloy steel comprises the following main alloy elements by mass percentage: 0.25-0.30% of C, 0.10-0.20% of Si, 1.51-1.62% of Mn, 3.60-4.10% of Cr, 0.20-0.30% of Mo, 0.20-0.40% of V, 0.03-0.05% of Nb, and the balance Fe. The alloy steel preparation process comprises the following steps: preparing materials, smelting, casting an electrode rod, and annealing; then carrying out electroslag remelting, and annealing; followed by carrying out multidirectional forging and direct water cooling; then carrying out two-section type annealing; and finally, carrying out quenching and tempering treatment. The properties of the alloy steel are equal to or exceed those of H13 steel under same conditions. The low-alloying-composition design thought of the alloy steel meets a transformation concept that current Chinese steel enterprises are in urgent need of energy saving, consumption reduction, cost reduction and benefit increase.

Description

Steel alloy and preparation and heat treating method for economical plug

Technical field

The present invention relates to a kind of economical plug steel alloy and preparation and heat treating method, belong to steel alloy manufacturing process technology field.

Background technology

Plug is as one of important rolling tool, and Main Function is the ring-type pass that forms sealing with roller combination, thereby to hollow billet tube reducing, subtract wall, eliminates pierced shell surfaces externally and internally spiral impression simultaneously, improves hollow forging surfaces externally and internally roughness and planeness.Plug not only will bear larger rolling pressure, skin friction force in the operation of rolling, also will bear the heat (comprising the heat that distortion produces) from hollow billet.In order to bear larger rolling pressure and higher temperature, plug should have higher intensity, hardness, wear resistance and hot-cracking resistance.

The production efficiency of plug to Continuous Seamless Tube Mill, the length of rolling hollow forging, specification limit, quality product and product cost all have a significant impact, and are also proportion maximums in the loss of Continuous Seamless Tube Mill production cost.According to statistics, the enterprise of approximately 1,000,000 tons of steel pipes of average year output, approximately 100,000,000 yuan of the expenses of year consumption plug.So large plug cost, concerning Steel Pipe Enterprise, be undoubtedly a white elephant, therefore, how to use better plug, how in ensureing quality product and output, extend plug work-ing life, reduce costs, realizing energy-saving and cost-reducing synergy is that Continuous Seamless Tube Mill production field has one of important topic to be solved.

The plug that current domestic weldless steel tube producer mainly adopts high quality steel H13 and H11 to make is produced.High quality steel is used to manufacture plug with its good high temperature obdurability, but in use, often intensity is had a surplus, and toughness deficiency, part plug recycles less than 1000 subsurfaces and just occurs a large amount of thermal cracks and wearing and tearing cut, because defect is darker, cannot change car, then cause and scrap, affect the production of mandrel mill-rolled steel pipe, also increased the cost of steel pipe's production simultaneously, extend the production cycle, and enterprise in a large number deposit can cause the pressure of capital chain week swivel link, if deposit not, enterprise's emergency mobile can reduce greatly so, affect the production program of whole enterprise.In addition, because high quality steel alloy content is higher, have higher hot strength, in hot continuous rolling and sizing operation, producing weldless steel tube needs larger load, and PQF milling train and sizing mill are difficult to reach production requirement.Thereby, in order to obtain the initiative in market, actively policy of " saving energy and reduce the cost ", " cost efficiency " " environmental protection " etc. that response country proposes, the economical low-alloy plug of China's independent research is very urgent with steel.

Therefore, the present invention adopts economical low alloying Composition Design thinking, on widely used high quality steel H13 basis, market, reduces Si, Cr and more expensive Mo, the V content of price, the Mn content of improving price cheap, and be equipped with micro-Nb and ensure the performance of steel.And obtain good plug use properties by final reasonably thermal treatment process, thereby reduce material cost and manufacturing cost, systematically promote plug manufacturing technology and quality level, make China have qualitative leap at aspects such as the research and development ability of plug, manufacture level, operation techniques.

Summary of the invention

For existing technological deficiency, the object of this invention is to provide a kind of economical plug steel alloy and preparation and heat treating method.Its objective is when meeting Current Domestic weldless steel tube enterprise Continuous Seamless Tube Mill and to produce high alloy mandrel material used and manufacturing cost is high, long this demand of cycle, the positive policies such as the iron and steel enterprise that responds national current proposition " save energy and reduce the cost ", " cost efficiency " " environmental protection ".The present invention, from novelty angle, adopts economical low alloying Composition Design thinking, on high quality steel H13 basis, reduces Cr, Si and more expensive Mo, the V content of price, the Mn content of improving price cheap, and be equipped with micro-Nb and ensure the performance of steel.The raising of Mn, can strengthen solution strengthening effect, improves obdurability and the thermostability of steel alloy of the present invention; The reduction of Si, Cr can improve the thermal conductivity of steel alloy of the present invention; The reduction of Cr, V can obviously improve or eliminate the liquation carbide of steel alloy of the present invention; The Nb of trace can ensure the structure refinement of steel.

For achieving the above object, the present invention adopts following technical scheme.

A kind of economical plug steel alloy, the mass percent of its each main alloy element is as follows:

C 0.25~0.30 %；

Si 0.10~0.20 %；

Mn 1.51~1.62 %；

Cr 3.60~4.10 %；

Mo 0.20~0.30 %；

V 0.20~0.40 %；

Nb 0.03~0.05%；

Fe surplus.

Preparation and a heat treating method for above-mentioned economical plug with steel alloy, the method has following step:

A. smelt: after alloy is prepared burden by above-mentioned economical plug steel alloy composition proportion, put into medium-frequency induction furnace or electric arc furnace carries out melting; Then carry out refining and vacuum outgas, finally pour into electrode bar, stand-by after 840 ~ 860 DEG C of annealing;

B. esr: be positioned over electrode bar as consumable electrode in esr device, carry out esr, change slag voltage 50 ~ 55V, electric current 3800 ~ 4500A, electric system voltage 52 ~ 58V, electric current 11000 ~ 12000A, voltage 60 ~ 62V binds; Make the further refining of steel by esr, removal of inclusions, eliminates or alleviates various macroscopic views and microscopic defect, obtains high quality ESR ingot, stand-by after 800 ~ 820 DEG C of annealing;

C. forge: before forging, Heating temperature is 1200～1250 DEG C; Open forging temperature: 1100 ~ 1150 DEG C; Final forging temperature: 850 ~ 900 DEG C, forging ratio >=4, direct water-cooling after forging;

D. annealing: adopt 860 ~ 870 DEG C and 730 ~ 740 DEG C of two-part isothermal spheroidizings;

E. rolling: be placed on ring furnace through the material of forging rear annealing and heat, Heating temperature is 1150 ~ 1200 DEG C, then bores a hole, through mill milling moulding, and the complete rear natural air cooling of sizing;

F. thermal treatment: 930 ~ 970 DEG C of insulations, oil quenching; Twice of 580 ~ 600 DEG C of tempering; Finally obtain plug steel alloy.

Compared with prior art, the invention has the beneficial effects as follows:

Through preparation and the thermal treatment process of alloy optimization design and recommendation, steel alloy of the present invention is than high alloy H13 steel: the one, and material cost aspect reduces greatly, the total alloy content of steel alloy of the present invention is down to 3% left and right by 9% left and right of H13 steel, and it is larger that especially more expensive alloy Mo, V reduces amplitude; The 2nd, the optimization of alloying thinking meets the requirement of current plug use properties, improves Mn and strengthens solution strengthening effect, has improved obdurability and the thermostability of steel alloy of the present invention; Reduce the thermal conductivity that Si, Cr have improved steel alloy of the present invention; Reduce the liquation carbide that Cr, V have significantly improved steel alloy of the present invention; And the Nb of trace makes steel alloy tissue of the present invention obtain refinement; The 3rd, low-alloy plug with the development of steel meet current national to iron and steel enterprise " save energy and reduce the cost ", requirement transition of " cost efficiency " " environmental protection ".

Brief description of the drawings

Fig. 1 is the quench tempering state metallographic contrast of steel alloy of the present invention and H13 steel.

Fig. 2 is steel alloy of the present invention and the contrast of H13 steel room temperature V2 type notch impact toughness.

Fig. 3 is steel alloy of the present invention and the contrast of H13 steel thermal stability.

Fig. 4 is steel alloy of the present invention and H13 steel surface and the contrast of cross section heat fatigue cracking pattern.

Embodiment

Now specific embodiments of the invention are described in down.

embodiment 1

In the present embodiment, adopt moiety and the mass percent thereof of economical plug steel alloy as follows:

C 0.30%

Si 0.20%

Mn 1.52%

Cr 3.60%

Mo 0.28%

V 0.36%

Nb 0.048%

P 0.012%

S 0.005%

Fe surplus

Preparation and heat treating method in the present embodiment are as follows:

A. electrosmelting: carry out melting by the alloying element proportioning in embodiment 1 in electric arc furnace, smelting temperature is greater than 1500 DEG C, is cast into Ф 740mm electrode bar, stand-by after 860 DEG C of annealing 20h;

B. esr: be positioned over the electrode bar after pouring as consumable electrode in esr device, carry out esr, change slag voltage 52V, electric current 4000A, electric system voltage 54V, electric current 11000A, voltage 60V binds; Current time 40min, esr becomes Ф 900mm ESR ingot, stand-by after 840 ~ 860 DEG C of annealing 28h;

C. forge: before forging, Heating temperature is 1250 DEG C insulation 15h; Open forging temperature: 1150 DEG C; Final forging temperature: 850 DEG C, forging ratio >=4, direct water-cooling after forging;

D. annealing: first stage isothermal annealing temperature is 860 DEG C, and annealing time is 8h; Subordinate phase isothermal annealing temperature is 740 DEG C, and annealing time is 14h; ;

E. rolling: be placed on ring furnace through the material of forging rear annealing and heat, Heating temperature is 1180 DEG C, then bores a hole, through mill milling moulding, and the complete rear natural air cooling of sizing;

F. thermal treatment: 950 DEG C of insulations, oil quenching; Then carry out twice of 590 DEG C of tempering; Finally obtain plug steel alloy.

embodiment 2

In the present embodiment, adopt moiety and the mass percent thereof of economical plug steel alloy as follows:

C 0.28%

Si 0.18%

Mn 1.58%

Cr 3.92%

Mo 0.28%

V 0.37%

Nb 0.040%

P 0.013%

S 0.005%

Fe surplus

Preparation and heat treating method in the present embodiment are as follows:

A. electrosmelting: carry out melting by the alloying element proportioning in embodiment 2 in electric arc furnace, smelting temperature is greater than 1500 DEG C, is cast into Ф 680mm electrode bar, stand-by after 850 DEG C of annealing 18h;

B. esr: be positioned over the electrode bar after pouring as consumable electrode in esr device, carry out esr, change slag voltage 54V, electric current 4200A, electric system voltage 56V, electric current 12000A, voltage 62V binds; Current time 38min, esr becomes Ф 800mm ESR ingot, stand-by after 850 DEG C of annealing 25h;

C. forge: before forging, Heating temperature is 1240 DEG C insulation 16h; Open forging temperature: 1180 DEG C; Final forging temperature: 900 DEG C, forging ratio >=4, direct water-cooling after forging;

D. annealing: first stage isothermal annealing temperature is 850 DEG C, and annealing time is 7h; Subordinate phase isothermal annealing temperature is 730 DEG C, and annealing time is 13h; ;

E. rolling: be placed on ring furnace through the material of forging rear annealing and heat, Heating temperature is 1200 DEG C, then bores a hole, through mill milling moulding, and the complete rear natural air cooling of sizing;

F. thermal treatment: 970 DEG C of insulations, oil quenching; Then carry out twice of 600 DEG C of tempering; Finally obtain plug steel alloy.

The economical plug of embodiment 1 and 2 two kinds of alloying constituents of embodiment is with steel alloy after above-mentioned preparation and thermal treatment, and final finished plug specification is Φ 150mm, and sampling is carried out performance test and contrasts with the H13 steel under equal conditions.

The performance comparison of steel alloy of the present invention and H13 steel is as follows:

A. the tempering state of quenching metallographic

The plug of embodiment 1 and 2 two kinds of alloying constituents of embodiment presents typical tempering lath martensite+carbide feature with the steel alloy tempering state metallographic of quenching, and the lath martensite feature of H13 under equal stiffness conditions has not been clearly, test result as shown in Figure 1.

B. the tempering state of quenching impelling strength

On the blank that is 35 ~ 37HRC in hardness, get lateral impact sample, specimen size is 10mm × 10mm × 55mm, opens V2 type breach, and under equal stiffness conditions,, far above H13 steel, test result as shown in Figure 2 for steel alloy of the present invention (embodiment 1 and embodiment 2).

C. thermal stability

Steel alloy of the present invention (embodiment 1 and embodiment 2) carries out stability contrast experiment with H13 steel under 620 DEG C of conditions, H13 steel is through after the temper of quenching, its hardness value and steel alloy of the present invention approach, be 35 ~ 37HRC, test-results as shown in Figure 3, steel alloy of the present invention is more because Mn content increases, and thermal stability quite even surmounts compared with H13 steel.

D. thermal fatigue property

Under DEG C condition of room temperature ~ 700, carry out cold cycling, after 3000 cold cycling, contrast thermal fatigue surface and the cross section crack morphology of steel alloy of the present invention (embodiment 1 and embodiment 2) and H13 steel, as shown in Figure 4.As seen from Figure 4, after steel alloy thermal fatigue test of the present invention, surface net cracks is thin compared with H13, and cross section crack depth is more shallow compared with H13, and thermal fatigue property is better than H13 steel.

Claims (2)

1. an economical plug steel alloy, is characterized in that: the mass percent of each main alloy element is as follows:

C 0.25~0.30 %；

Si 0.10~0.20 %；

Mn 1.51~1.62 %；

Cr 3.60~4.10 %；

Mo 0.20~0.30 %；

V 0.20~0.40 %；

Nb 0.03~0.05%；

Fe surplus.

2. prepare a method of using steel alloy with thermal treatment economical plug as claimed in claim 1, it is characterized in that the method has following steps:

A. smelt: alloy is put into medium-frequency induction furnace after by composition proportion batching described in claim 1 or electric arc furnace carries out melting; Then carry out refining and vacuum outgas, finally pour into electrode bar, stand-by after 840 ~ 860 DEG C of annealing;

B. esr: be positioned over electrode bar as consumable electrode in esr device, carry out esr, change slag voltage 50 ~ 55V, electric current 3800 ~ 4500A, electric system voltage 52 ~ 58V, electric current 11000 ~ 12000A, voltage 60 ~ 62V binds; Make the further refining of steel by esr, removal of inclusions, eliminates or alleviates various macroscopic views and microscopic defect, obtains high quality ESR ingot, stand-by after 840 ~ 860 DEG C of annealing;

C. forge: before forging, Heating temperature is 1200～1250 DEG C; Open forging temperature: 1100 ~ 1150 DEG C; Final forging temperature: 850 ~ 900 DEG C, forging ratio >=4, direct water-cooling after forging;

D. annealing: adopt 860 ~ 870 DEG C and 730 ~ 740 DEG C of two-part isothermal spheroidizings;

E. rolling: be placed on ring furnace through the material of forging rear annealing and heat, Heating temperature is 1150 ~ 1200 DEG C, then bores a hole, through mill milling moulding, and the complete rear natural air cooling of sizing;

F. thermal treatment: 930 ~ 970 DEG C of insulations, oil quenching; Twice of 580 ~ 600 DEG C of tempering; Finally obtain plug steel alloy.