CN104551540A - Production method of cold-drawn precise cylinder tube - Google Patents

Abstract

The invention relates to a production method of a cold-drawn precise cylinder tube. The production method includes heating a tube blank in a circular furnace; punching a heat tube by the aid of a puncher; subjecting the tube blank to annealing; spraying the tube blank with sodium borate to remove oxide skin; leading the annealed tube blank into a tube mill for hot milling; tensioning the milled tube after tandem milling by a tensioning machine for sizing; performing stress relieving, to be specific, heating the milled tube in a heating furnace to obtain an annealed tube blank; performing acid dipping on the tube blank to remove scale of the surface; subjecting the tube blank to parkerizing, and accordingly a chemical coating of zinc phosphate is generated on the surface of the tube blank; performing saponification to form lubricating coatings such as metallic soap; subjecting the tube blank to be cold drawn to cold drawing, and the cold-drawn tube is achieved; performing normalizing air cooling; straightening the cold-drawn tube; quenching the cold-drawn tube in an induction furnace; tempering the cold-drawn tube in a box-type furnace; honing the cold-drawn tube; subjecting the cold-drawn tube to heat straightening. The cold-drawn precise cylinder tube made in the way is good in comprehensive performance and low-temperature impact toughness, has precise size and smooth surface and is good in oil storage effect.

Description

A kind of manufacture method of cold drawing accurate oil cylinder bobbin

Technical field

The invention belongs to steel pipe preparing technical field, be specifically related to a kind of manufacture method of cold drawing accurate oil cylinder bobbin.

Background technology

As the cold process of the steel for mechanical structure pipes such as carbon steel, alloy steel or stainless steel, there are known the drawing processing method of being undertaken by drawbench and the rolling processing method of being undertaken by Pierre's form milling train.Wherein, the drawing processing method of being undertaken by drawbench, compared with the rolling processing method of carrying out with machine of being pricked by Pierre's form, cold working steel pipe can be manufactured expeditiously, this seamless steel pipe is used for oil hydraulic cylinder, pneumatic cylinder uses, and at present, most Hi-grade steel its yield strength, dimensional discrepancy etc. of domestic current prescribed by standard all cannot meet the instructions for use of actual oil hydraulic cylinder, pneumatic cylinder, make the oil hydraulic cylinder of China, pneumatic cylinder seamless steel pipe can only dependence on import, constrain the development of China's cold tube rolling.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, a kind of manufacture method of cold drawing accurate oil cylinder bobbin is provided, the cold drawing accurate oil cylinder bobbin that the method obtains, improve the wearability on surface, case hardness and intensity improve, improve the wearability of surface of the work, corrosion resistance and conformability, oil cylinder service life, improve 2 ~ 3 times, yield strength is high, tensile strength is high, precision size, smooth surface, its store oil excellent performance, make running more smooth and easy, without stall condition, expanded service life, be applicable to oil hydraulic cylinder, pneumatic cylinder, fork truck, crane, stacker, building machinery, the various laborsaving automated machine engineering such as punch press.

According to technical scheme provided by the invention, a kind of manufacture method of cold drawing accurate oil cylinder bobbin comprises the steps:

(1), heating: 27SiMn pipe is heated to 1200 ~ 1290 DEG C in annular furnace, and the heat time is 4 ~ 5 hours, thus ensures that heating of pipe blank is even;

(2), bore a hole: heat pipe base perforated machine is bored a hole, the temperature of the hollow billet formed after perforation controls at 1150 ~ 1220 DEG C, and order control punch eccentricity and control pipe surface quality;

(3), annealing: introduced in continuous annealing furnace by pipe and anneal, and order control annealing temperature is 600 ~ 650 DEG C, annealing time is 70 ~ 80min, obtains the annealing pipe that annealing hardness (HV) is 210 ~ 216;

(4), borax is sprayed: spray borax device blows to the descaling of hollow billet endoporus nitrogen and borax through spiral nozzle and fill nitrogen in hollow billet, its main function is removed by the residual oxidization skin in hollow billet, form a skim at the inner surface of hollow billet simultaneously, prevent hollow billet to be further oxidized;

(5), hot rolling: pipe of annealing introduces pipe mill hot rolling, and hot-rolled temperature is 1250 ~ 1260 DEG C, obtains rolled pipe;

(6), tensioning: the rolled pipe formed after tandem rolling is again through tensioning device sizing, and form steel pipe, finishing temperature control during tensioning is at 500 ~ 650 DEG C;

(7), stress relief annealing: rolled pipe introduced heating in heating furnace and be incubated, come out of the stove with after stove cooling, obtain pipe of annealing, object is the intensity guaranteeing steel pipe, when annealing temperature is too high, processing strain recovers, can not obtain the effect of work hardening, annealing temperature is 550 ~ 610 DEG C, can obtain the effect of work hardening, in order to remove the strength variance of cold tube rolling, in the stove of cold tube rolling, the retention time is 10 ~ 50 minutes;

(8), pickling processes: annealing pipe is carried out pickling, removes the scale on surface, concentration of hydrochloric acid: 7 ~ 19%, pickling time: 35 ~ 60 minutes, then neutralization pond rolling, rolling number of times: 2 ~ 3 times, neutralizer pH value: 9 ~ 10, then through clear water reserviors rolling, rolling number of times: 2 ~ 3 times;

(9), phosphorating treatment: the chemistry forming trbasic zinc phosphate on the surface of pipe generates overlay film, trbasic zinc phosphate concentration: 20 ~ 30%, Phosphating Solution temperature: 68 ~ 75 DEG C, phosphating time: 10 ~ 20 minutes, Phosphating Solution free acidity: 4 ~ 7, General Acidity in Phosphating Solution: 45 ~ 75;

(10), saponification process: form the lubricating film coateds such as metallic soap on overlay film, saponification temperature: 55 ~ 75 DEG C, saponification time: 8 ~ 15 minutes, saponification liquor pH value: 8 ~ 9;

(11), cold-drawn: will treat that cold-drawn pipe carries out cold-drawn processing, and obtain drawn tube, cold-drawing technology, mould chock plug and bore spacing: 3 ~ 5mm, pull out machine draft: 350 ~ 450t, and saponification pipe pulls out the front storage period: 72 ~ 96h;

(12), normalizing air cooling process: the temperature of normalizing air cooling is 800 ~ 880 DEG C, prevents steel tube surface from occurring pockmark, carries out surface treatment;

(13), pre-straightening process: straightening temperature 650 ~ 680 DEG C, to reduce residual stress;

(14), induction furnace Quenching Treatment: induction furnace hardening heat is 850 ~ 890 DEG C, and hardening media is water, reduces the residual stress of drawn tube;

(15), temper in batch-type furnace: the temperature of tempering air cooling is 400 ~ 450 DEG C, to reduce residual stress;

(16), honing: select vertical honing machine, workpiece turns round, and the form processing that honing head is reciprocating, reaches cylindricity: 0.01 ~ 0.02mm, Aperture deviation: 0.01 ~ 0.02mm, roughness: the high standard precision of Ra0.25 ~ 0.35;

(17), thermal straightening process: be incubated 45 ~ 60 minutes in low-temp temper furnace, carry out thermal straightening process again, thermal straightening temperature 550 ~ 600 DEG C, obtain yield strength (MPa): 805, tensile strength (MPa): 840, outer diameter tolerance :+0.5%, wall thickness tolerance: 8%, external diameter out-of-roundness: 0.3%, eccentricity: 6%, the cold drawing accurate oil cylinder bobbin of linearity: 0.30mm/m.

Beneficial effect of the present invention is as follows: the cold drawing accurate oil cylinder bobbin utilizing the inventive method to produce, improve the wearability on surface, case hardness and intensity improve, improve the wearability of surface of the work, corrosion resistance and conformability, oil cylinder service life, improve 2 ~ 3 times, yield strength is high, tensile strength is high, precision size, smooth surface, its store oil excellent performance, make running more smooth and easy, without stall condition, expanded service life, be applicable to oil hydraulic cylinder, pneumatic cylinder, fork truck, crane, stacker, building machinery, the various laborsaving automated machine engineering such as punch press.

Detailed description of the invention:

Below in conjunction with specific embodiment, the invention will be further described.

Embodiment one:

To prepare diameter for 155.3mm and the hole wall wall thickness 27SiMn steel pipe that is 7.63mm, comprise the following steps:

(1), heating: 27SiMn pipe is heated to 1200 DEG C in annular furnace, and the heat time is 4 hours, thus ensures that heating of pipe blank is even;

(2), bore a hole: heat pipe base perforated machine is bored a hole, the temperature of the hollow billet formed after perforation controls at 1150 DEG C, and order control punch eccentricity is 4%, visualize is carried out to pipe, use remove pipe surface burr, stick up skin, if pipe surface occurs or there is pit that significantly namely naked eyes are obvious, runs over and injure and crackle, then should reject, avoid flowing into subsequent processing, to control pipe surface quality;

(3), annealing: introduced in continuous annealing furnace by pipe and anneal, and order control annealing temperature is 600 DEG C, annealing time is 0min, obtains the annealing pipe that annealing hardness (HV) is 210;

(4), borax is sprayed: spray borax device blows to the descaling of hollow billet endoporus nitrogen and borax through spiral nozzle and fill nitrogen in hollow billet, its main function is removed by the residual oxidization skin in hollow billet, form a skim at the inner surface of hollow billet simultaneously, prevent hollow billet to be further oxidized;

(5), hot rolling: pipe of annealing introduces pipe mill hot rolling, and hot-rolled temperature is 1250 DEG C, obtains rolled pipe;

(6), tensioning: the rolled pipe formed after tandem rolling is again through tensioning device sizing, and form steel pipe, finishing temperature control during tensioning is at 500 DEG C;

(7), stress relief annealing: rolled pipe introduced heating in heating furnace and be incubated, come out of the stove with after stove cooling, obtain pipe of annealing, object is the intensity guaranteeing steel pipe, when annealing temperature is too high, processing strain recovers, can not obtain the effect of work hardening, annealing temperature is 550 DEG C, can obtain the effect of work hardening, in order to remove the strength variance of cold tube rolling, in the stove of cold tube rolling, the retention time is 10 minutes;

(8), pickling processes: annealing pipe is carried out pickling, removes the scale on surface, concentration of hydrochloric acid: 7%, pickling time: 35 minutes, then neutralization pond rolls, rolling number of times: 2 times, neutralizer pH value: 9, then roll through clear water reserviors, rolling number of times: 2 times;

(9), phosphorating treatment: the chemistry forming trbasic zinc phosphate on the surface of pipe generates overlay film, trbasic zinc phosphate concentration: 20%, Phosphating Solution temperature: 68 DEG C, phosphating time: 10 minutes, Phosphating Solution free acidity: 4, General Acidity in Phosphating Solution: 45;

(10), saponification process: form the lubricating film coateds such as metallic soap on overlay film, saponification temperature: 55 DEG C, saponification time: 8 minutes, saponification liquor pH value: 8;

(11), cold-drawn: will treat that cold-drawn pipe carries out cold-drawn processing, and obtain drawn tube, cold-drawing technology, mould chock plug and bore ask distance: 3mm, pull out machine draft: 350t, and saponification pipe pulls out the front storage period: 72h;

(12), normalizing air cooling process: the temperature of normalizing air cooling is 800 DEG C, prevents steel tube surface from occurring pockmark, carries out surface treatment;

(13), straightening processing: straightening temperature 650 DEG C, to reduce residual stress;

(14), induction furnace Quenching Treatment: induction furnace hardening heat is 850 DEG C, and hardening media is water, reduces the residual stress of drawn tube;

(15), temper in batch-type furnace: the temperature of tempering air cooling is 400 DEG C, to reduce residual stress;

(16), honing: select vertical honing machine, workpiece turns round, and the form processing that honing head is reciprocating, reaches cylindricity: 0.01mm, Aperture deviation: 0.01mm, roughness: the high standard precision of Ra0.25;

(17), thermal straightening process: be incubated 45 minutes in low-temp temper furnace, carry out thermal straightening process again, thermal straightening temperature 550 DEG C, obtain yield strength (MPa): 875, tensile strength (MPa): 896, outer diameter tolerance :+0.5%, wall thickness tolerance: 8%, external diameter out-of-roundness: 0.3%, eccentricity: 6%, the cold drawing accurate oil cylinder bobbin of linearity: 0.30mm/m.

After testing, institute's inspection project meets GB/T3639-2009 standard to the product that the present embodiment obtains, and product is qualified, meets the requirement of user to yield strength, tensile strength, hardness.

The contrast in technical performance of a kind of cold drawing accurate oil cylinder bobbin and conventional steel pipe

Embodiment two:

To prepare diameter for 139.9mm and the hole wall wall thickness 27SiMn steel pipe that is 7.89mm, comprise the following steps:

(1), heating: 27SiMn pipe is heated to 1290 DEG C in annular furnace, and the heat time is 5 hours, thus ensures that heating of pipe blank is even;

(2), bore a hole: heat pipe base perforated machine is bored a hole, the temperature of the hollow billet formed after perforation controls at 1220 DEG C, and order control punch eccentricity is 4%, visualize is carried out to pipe, use remove pipe surface burr, stick up skin, if pipe surface occurs or there is pit that significantly namely naked eyes are obvious, runs over and injure and crackle, then should reject, avoid flowing into subsequent processing, to control pipe surface quality;

(3), annealing: introduced in continuous annealing furnace by pipe and anneal, and order control annealing temperature is 650 DEG C, annealing time is 80min, obtains the annealing pipe that annealing hardness (HV) is 216;

(4), borax is sprayed: spray borax device blows to the descaling of hollow billet endoporus nitrogen and borax through spiral nozzle and fill nitrogen in hollow billet, its main function is removed by the residual oxidization skin in hollow billet, form a skim at the inner surface of hollow billet simultaneously, prevent hollow billet to be further oxidized;

(5), hot rolling: pipe of annealing introduces pipe mill hot rolling, and hot-rolled temperature is 1260 DEG C, obtains rolled pipe;

(6), tensioning: the rolled pipe formed after tandem rolling is again through tensioning device sizing, and form steel pipe, finishing temperature control during tensioning is at 650 DEG C;

(7), stress relief annealing: rolled pipe introduced heating in heating furnace and be incubated, come out of the stove with after stove cooling, obtain pipe of annealing, object is the intensity guaranteeing steel pipe, when annealing temperature is too high, processing strain recovers, can not obtain the effect of work hardening, annealing temperature is 610 DEG C, can obtain the effect of work hardening, in order to remove the strength variance of cold tube rolling, in the stove of cold tube rolling, the retention time is 50 minutes;

(8), pickling processes: annealing pipe is carried out pickling, removes the scale on surface, concentration of hydrochloric acid: 19%, pickling time: 60 minutes, then neutralization pond rolls, rolling number of times: 3 times, neutralizer pH value: 10, then roll through clear water reserviors, rolling number of times: 3 times;

(9), phosphorating treatment: the chemistry forming trbasic zinc phosphate on the surface of pipe generates overlay film, trbasic zinc phosphate concentration: 30%, Phosphating Solution temperature: 75 DEG C, phosphating time: 20 minutes, Phosphating Solution free acidity: 7, General Acidity in Phosphating Solution: 75;

(10), saponification process: form the lubricating film coateds such as metallic soap on overlay film, saponification temperature: 75 DEG C, saponification time: 15 minutes, saponification liquor pH value: 9;

(11), cold-drawn: will treat that cold-drawn pipe carries out cold-drawn processing, and obtain drawn tube, cold-drawing technology, mould chock plug and bore spacing: 5mm, pull out machine draft: 450t, and saponification pipe pulls out the front storage period: 96h;

(12), normalizing air cooling process: the temperature of normalizing air cooling is 880 DEG C, prevents steel tube surface from occurring pockmark, carries out surface treatment;

(13), pre-straightening process: straightening temperature 680 DEG C, to reduce residual stress;

(14), induction furnace Quenching Treatment: induction furnace hardening heat is 890 DEG C, and hardening media is water, reduces the residual stress of drawn tube;

(15), temper in batch-type furnace: the temperature of tempering air cooling is 450 DEG C, to reduce residual stress;

(16), honing: select vertical honing machine, workpiece turns round, and the form processing that honing head is reciprocating, reaches cylindricity: 0.02mm, Aperture deviation: 0.02mm, roughness: the high standard precision of Ra0.35;

(17), thermal straightening process: be incubated 60 minutes in low-temp temper furnace, carry out thermal straightening process again, thermal straightening temperature 600 DEG C, obtain yield strength (MPa): 877, tensile strength (MPa): 886, outer diameter tolerance :+0.5%, wall thickness tolerance: 8%, external diameter out-of-roundness: 0.3%, eccentricity: 6%, the cold drawing accurate oil cylinder bobbin of linearity: 0.30mm/m.

Embodiment three:

To prepare diameter for 159.4mm and the hole wall wall thickness 27SiMn steel pipe that is 7.52mm, comprise the following steps:

(1), heating: 27SiMn pipe is heated to 1280 DEG C in annular furnace, and the heat time is 4.5 hours, thus ensures that heating of pipe blank is even;

(2), bore a hole: heat pipe base perforated machine is bored a hole, the temperature of the hollow billet formed after perforation controls at 1200 DEG C, and order control punch eccentricity is 4%, visualize is carried out to pipe, use remove pipe surface burr, stick up skin, if pipe surface occurs or there is pit that significantly namely naked eyes are obvious, runs over and injure and crackle, then should reject, avoid flowing into subsequent processing, to control pipe surface quality;

(3), annealing: introduced in continuous annealing furnace by pipe and anneal, and order control annealing temperature is 630 DEG C, annealing time is 75min, obtains the annealing pipe that annealing hardness (HV) is 213;

(4), borax is sprayed: spray borax device blows to the descaling of hollow billet endoporus nitrogen and borax through spiral nozzle and fill nitrogen in hollow billet, its main function is removed by the residual oxidization skin in hollow billet, form a skim at the inner surface of hollow billet simultaneously, prevent hollow billet to be further oxidized;

(5), hot rolling: pipe of annealing introduces pipe mill hot rolling, and hot-rolled temperature is 1255 DEG C, obtains rolled pipe;

(6), tensioning: the rolled pipe formed after tandem rolling is again through tensioning device sizing, and form steel pipe, finishing temperature control during tensioning is at 600 DEG C;

(7), stress relief annealing: rolled pipe introduced heating in heating furnace and be incubated, come out of the stove with after stove cooling, obtain pipe of annealing, object is the intensity guaranteeing steel pipe, when annealing temperature is too high, processing strain recovers, can not obtain the effect of work hardening, annealing temperature is 590 DEG C, can obtain the effect of work hardening, in order to remove the strength variance of cold tube rolling, in the stove of cold tube rolling, the retention time is 40 minutes;

(8), pickling processes: annealing pipe is carried out pickling, removes the scale on surface, concentration of hydrochloric acid: 13%, pickling time: 45 minutes, then neutralization pond rolling, rolling number of times: 2.5 times, neutralizer pH value: 9.5, then through clear water reserviors rolling, rolling number of times: 2.5 times;

(9), phosphorating treatment: the chemistry forming trbasic zinc phosphate on the surface of pipe generates overlay film, trbasic zinc phosphate concentration: 25%, Phosphating Solution temperature: 70 DEG C, phosphating time: 15 minutes, Phosphating Solution free acidity: 6, General Acidity in Phosphating Solution: 55;

(10), saponification process: form the lubricating film coateds such as metallic soap on overlay film, saponification temperature: 65 DEG C, saponification time: 10 minutes, saponification liquor pH value: 8.5;

(11), cold-drawn: will treat that cold-drawn pipe carries out cold-drawn processing, and obtain drawn tube, cold-drawing technology, mould chock plug and bore spacing: 4mm, pull out machine draft: 420t, and saponification pipe pulls out the front storage period: 84h;

(12), normalizing air cooling process: the temperature of normalizing air cooling is 860 DEG C, prevents steel tube surface from occurring pockmark, carries out surface treatment;

(13), pre-straightening process: straightening temperature 670 DEG C, to reduce residual stress;

(14), induction furnace Quenching Treatment: induction furnace hardening heat is 880 DEG C, and hardening media is water, reduces the residual stress of drawn tube;

(15), temper in batch-type furnace: the temperature of tempering air cooling is 440 DEG C, to reduce residual stress;

(16), honing: select vertical honing machine, workpiece turns round, and the form processing that honing head is reciprocating, reaches cylindricity: 0.015mm, Aperture deviation: 0.015mm, roughness: the high standard precision of Ra0.28;

(17), thermal straightening process: be incubated 55 minutes in low-temp temper furnace, carry out thermal straightening process again, thermal straightening temperature 580 DEG C, obtain yield strength (MPa): 877, tensile strength (MPa): 893, outer diameter tolerance :+0.5%, wall thickness tolerance: 8%, external diameter out-of-roundness: 0.3%, eccentricity: 6%, the cold drawing accurate oil cylinder bobbin of linearity: 0.30mm/m.

Claims (1)

1. the manufacture method of a cold drawing accurate oil cylinder bobbin comprises the steps:

(1), heating: 27SiMn pipe is heated to 1200 ~ 1290 DEG C in annular furnace, and the heat time is 4 ~ 5 hours, thus ensures that heating of pipe blank is even;

(2), bore a hole: heat pipe base perforated machine is bored a hole, the temperature of the hollow billet formed after perforation controls at 1150 ~ 1220 DEG C, and order control punch eccentricity and control pipe surface quality;

(3), annealing: introduced in continuous annealing furnace by pipe and anneal, and order control annealing temperature is 600 ~ 650 DEG C, annealing time is 70 ~ 80min, obtains the annealing pipe that annealing hardness (HV) is 210 ~ 216;

(4), borax is sprayed: spray borax device blows to the descaling of hollow billet endoporus nitrogen and borax through spiral nozzle and fill nitrogen in hollow billet, its main function is removed by the residual oxidization skin in hollow billet, form a skim at the inner surface of hollow billet simultaneously, prevent hollow billet to be further oxidized;

(5), hot rolling: pipe of annealing introduces pipe mill hot rolling, and hot-rolled temperature is 1250 ~ 1260 DEG C, obtains rolled pipe;

(6), tensioning: the rolled pipe formed after tandem rolling is again through tensioning device sizing, and form steel pipe, finishing temperature control during tensioning is at 500 ~ 650 DEG C;

(7), stress relief annealing: rolled pipe introduced heating in heating furnace and be incubated, come out of the stove with after stove cooling, obtain pipe of annealing, object is the intensity guaranteeing steel pipe, when annealing temperature is too high, processing strain recovers, can not obtain the effect of work hardening, annealing temperature is 550 ~ 610 DEG C, can obtain the effect of work hardening, in order to remove the strength variance of cold tube rolling, in the stove of cold tube rolling, the retention time is 10 ~ 50 minutes;

(8), pickling processes: annealing pipe is carried out pickling, removes the scale on surface, concentration of hydrochloric acid: 7 ~ 19%, pickling time: 35 ~ 60 minutes, then neutralization pond rolling, rolling number of times: 2 ~ 3 times, neutralizer pH value: 9 ~ 10, then through clear water reserviors rolling, rolling number of times: 2 ~ 3 times;

(9), phosphorating treatment: the chemistry forming trbasic zinc phosphate on the surface of pipe generates overlay film, trbasic zinc phosphate concentration: 20 ~ 30%, Phosphating Solution temperature: 68 ~ 75 DEG C, phosphating time: 10 ~ 20 minutes, Phosphating Solution free acidity: 4 ~ 7, General Acidity in Phosphating Solution: 45 ~ 75;

(10), saponification process: form the lubricating film coateds such as metallic soap on overlay film, saponification temperature: 55 ~ 75 DEG C, saponification time: 8 ~ 15 minutes, saponification liquor pH value: 8 ~ 9;

(11), cold-drawn: will treat that cold-drawn pipe carries out cold-drawn processing, and obtain drawn tube, cold-drawing technology, mould chock plug and bore spacing: 3 ~ 5mm, pull out machine draft: 350 ~ 450t, and saponification pipe pulls out the front storage period: 72 ~ 96h;

(12), normalizing air cooling process: the temperature of normalizing air cooling is 800 ~ 880 DEG C, prevents steel tube surface from occurring pockmark, carries out surface treatment;

(13), pre-straightening process: straightening temperature 650 ~ 680 DEG C, to reduce residual stress;

(14), induction furnace Quenching Treatment: induction furnace hardening heat is 850 ~ 890 DEG C, and hardening media is water, reduces the residual stress of drawn tube;

(15), temper in batch-type furnace: the temperature of tempering air cooling is 400 ~ 450 DEG C, to reduce residual stress;

(16), honing: select vertical honing machine, workpiece turns round, and the form processing that honing head is reciprocating, reaches cylindricity: 0.01 ~ 0.02mm, Aperture deviation: 0.01 ~ 0.02mm, roughness: the high standard precision of Ra0.25 ~ 0.35;

(17), thermal straightening process: be incubated 45 ~ 60 minutes in low-temp temper furnace, carry out thermal straightening process again, thermal straightening temperature 550 ~ 600 DEG C, obtain yield strength (MPa): 805, tensile strength (MPa): 840, outer diameter tolerance :+0.5%, wall thickness tolerance: 8%, external diameter out-of-roundness: 0.3%, eccentricity: 6%, the cold drawing accurate oil cylinder bobbin of linearity: 0.30mm/m.