CN1995433A - Tube for crane chord member and its production method - Google Patents

Abstract

The invention discloses a crane chord pipe and manufacturing method, which comprises the following steps: allocating raw material with 0.26-0.31% C, 0.17-0.35% Si, 1. 30-1. 50% Mn, 0.01-0.04% Ti, 0.0005-0.002% B and Fe and inevitable impurity; quenching; tempering under 470 deg. c for 60min; insulating at 900 deg. c for 20min; proceeding air cooling; adopting tempered martensite to make the metal phase of steel; transmitting austenite into martensite with large amount of microfine carbonate; selecting at least one element from Cu, Ni, Cr or one or two element from Sn and As.

Description

Tube for crane chord member and manufacture method

Technical field

The present invention relates to a kind of tube for crane chord member and manufacture method.

Background technology

Crane chord member is applied to model on the big elevating capacity crawler mounted crane truss type arm of " QUY200 ", is a member on the jib boom suspension bracket.This member adopts chord member steel pipe (being generally four) to press the certain angle welding with the usefulness as load-bearing, adopts welding process to connect with web member (other material steel pipe) between chord member and the chord member.

Existing main chord mainly is made of 12CrNiMnMoVB steel pipe, 14CrNiMnMoV steel pipe, TOK80 steel pipe, and its chemical ingredients and performance are as follows:

The 12CrNiMnMoVB modifier treatment: the roll-type stove is heated to air cooling normalizing after the 900-920 ℃ of soaking.Batch-type furnace is heated to 900-910 ℃ of insulation 60-65min quenching-in water.Batch-type furnace is heated to the tempering of 730-750 ℃ of insulation 120min air cooling.

The 14CrNiMnMoV normalizing treatment: adopt double normalizing, the forced air cooling novel process is heated to 920 ℃ of soaking for the first time, is heated to 900 ℃ of forced air coolings for the second time.The carbon content of 12CrNiMnMoVB steel is 0.52%.-20 ℃ of A _KVValue :-20 ℃ of A of two stove 12CrNiMnMoVB steel _KVValue is 56-130J.

The main chord tube material is TOK80, and specification is 60.3mm * 4.5mm, and its chemical ingredients % is: C0.12, Mn0.87, B0.001, P0.12, S0.005, mechanical property: yield strength 867Mpa, tensile strength 922Mpa.

Following three problems of existing crane chord member ubiquity:

(1) bad mechanical property, tension, surrender, twisting strength are low, near or easily bend, reverse when reaching specified load capacity, thereby cause the lifting machine inefficacy;

During (2) with the welding of the member of unlike material, phenomenons such as crack appear in seam place easily;

(3) after the use long period, be easy to generate tired defective, reduced the working life of lifting machine.

Summary of the invention

The objective of the invention is to overcome the above-mentioned deficiency of prior art and a kind of new tube for crane chord member and manufacture method are provided.

Technical scheme of the present invention is: 28MnTiB crane chord member steel pipe, composition is in quality %, specifically have: C:0.26～0.31, Si:0.17～0.35, Mn:1.30～1.50, Ti:0.01～0.04, B:0.0005～0.002, rest part is Fe and unavoidable impurities, tensile strength Rm is more than 980MPa, and yield strength Rel is more than 800MPa.

The steel pipe metallographic structure is a tempered martensite, and this martensite is the resultant that obtains from the austenitic transformation of processing, and a large amount of fine carbide are distributing in the martensitic matrix.

As above-mentioned steel pipe, also be:, aforementioned composition is increased by 1 group or 2 groups that selects again from following A～B group in quality %.Note

A group: Cu:0.2% is following, Ni:0.2% is following, below the Cr:0.2%, therefrom select more than a kind or 2 kinds:

B group: Sn:0.02% is following, below the As:0.03%, therefrom select a kind or 2 kinds.

Carbon content control: carbon content should be controlled at middle limit in the steel, or more on the low side.If carbon content is higher, can the plasticity and the welding property of steel be had a negative impact.

Material welding performance is mainly decided by the carbon equivalent of material, and the carbon equivalent of general requirement material is not more than 0.6 on the engineering, could guarantee the welding property of steel, and defectives such as weld crack do not appear in the seam position.

Carbon equivalent is calculated by following formula:

Ce＝C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15。

With heat (batch) number 0511895V is that example is calculated carbon equivalent:

Ce＝0.30+1.38/6+(0.03+0.01+0)/5+(0.16+0.04)/15＝0.55

The carbon equivalent of visible material satisfies the welding property requirement.

Titanium content control: titanium mainly exists with the TiC form in steel, plays dispersion-strengthened action.Because the titanium scaling loss is bigger, wayward when smelting, the specification composition range is narrow again, thus target component preferably be controlled at about 0.025%, in order to avoid composition exceeds standard.

The control of boron: the effect one of boron is to strengthen crystal boundary, the 2nd, and slow down proeutectoid ferrite and change, promote bainite transformation.But too high boron content can worsen the hot workability of steel, and is easy to crack when rolling.The performance of collateral security steel is set out, and target component should be controlled in 0.005 ~ 0.002% scope.

Take in decision under the prerequisite of quality adjustment condition delivery, according to the former experiments data, that considers production scene and other trade mark simultaneously is connected 900 ℃ of quenching temperature employings.At this moment, every mechanical property of steel pipe depends on choosing of tempering temperature.Find that through metallurgical analysis 28MnTiB trade mark steel pipe adds under 470 ℃ of tempering heat treatment states in quenching, it is organized as tempered martensite, because this tempered martensite is a large amount of fine carbide that distributing in martensitic matrix, thereby has higher strength and toughness.According to the difference of tempering temperature, the carbide of tempered martensite is also different.Carbide particle is tiny more, and is also big more to metal slippage, dislocation motion inhibition, and the intensity of steel is just high more.Along with the variation of tempering temperature from 400 ℃ to 500 ℃, carbide particle becomes thick gradually from tiny, and steel strength is then by high step-down.

According to the practical situation of situ production, choose thermal treatment process and be: quenching 900 ℃ adds 470 ℃ of 60min air coolings of tempering.Under this as-heat-treated condition, the yield strength of steel pipe reaches 815MPa, the yield tensile ratio height, and Rel/Rm 〉=0.8, elongation is more than 14%, the mean value of impelling strength is more than the 60J, satisfy the demand fully (seeing Table 1).

Table 1 tube for crane chord member performance

Produce unit	Lot number	Specification	Kind	State	Rel MPa	Rm MPa	A％	Ballistic work Akv (20 ℃) J (10 * 7.5 * 55 sample)
									φ89	956170520	φ60×4	Chord member	Modified	861	990	15.4
855	982	16.2
				φ89	956130316	φ76×5	Chord member	Modified						991	1077	14
951	1033	16.4
									φ108	855400199	φ114×9	Chord member	Modified	923	1003	16.2	65/63/72
953	1036	15.0
			φ108	855400200	φ114×9	Chord member	Modified	938						1020	19.2	71/61/64
958	1041	18.0
								The user is to chord member pipe performance requriements					≥ 785	≥ 900	≥12		≥50

28MnTiB crane chord member after the improvement also has following characteristics with steel pipe:

(1) in the application process, find satisfactory mechanical property, near or when reaching specified load capacity material do not bend, reverse, guaranteed normal, the safe operation of lifting machine;

During (2) with the welding of the member of unlike material, phenomenons such as crack do not appear in seam place.

(3) after the use long period, do not produce tired defective, prolonged the working life of lifting machine.

Embodiment:

28MnTiB crane chord member steel pipe, composition is in quality %, specifically have: C:0.26～0.31, Si:0.17～0.35, Mn:1.30～1.50, Ti:0.01～0.04, B:0.0005～0.002, rest part is Fe and unavoidable impurities, tensile strength Rm is more than 980MPa, and yield strength Rel is more than 800MPa.

The steel pipe metallographic structure is a tempered martensite, and this martensite is the resultant that obtains from the austenitic transformation of processing, and a large amount of fine carbide are distributing in the martensitic matrix.

As above-mentioned steel pipe, also be:, aforementioned composition is increased by 1 group or 2 groups that selects again from following A～B group in quality %.Note

A group: Cu:0.2% is following, Ni:0.2% is following, below the Cr:0.2%, therefrom select more than a kind or 2 kinds;

B group: Sn:0.02% is following, below the As:0.03%, therefrom select a kind or 2 kinds.

The 28MnTiB crane chord member is with the manufacture method of steel pipe: its optimal heat treated state adds average tempering for quenching, and its technology is: 900 ℃ of insulation 20min shrend of quenching, tempering is incubated the 60min air cooling for 470 ℃.

Claims (5)

1, a kind of tube for crane chord member, it is characterized in that: composition is in quality %, specifically have: C:0.26～0.31, Si:0.17～0.35, Mn:1.30～1.50, Ti:0.01～0.04, B:0.0005～0.002, rest part is Fe and unavoidable impurities, tensile strength Rm is more than 980MPa, and yield strength Rel is more than 800MPa.

2, tube for crane chord member as claimed in claim 1 is characterized in that: the steel pipe metallographic structure is a tempered martensite, and this martensite is the resultant that obtains from the austenitic transformation of processing, and a large amount of fine carbide are distributing in the martensitic matrix.

3, tube for crane chord member as claimed in claim 1 or 2 is characterized in that: in quality %, aforementioned composition is increased by 1 group or 2 groups that selects again from following A～B group, note

A group: Cu:0.2% is following, Ni:0.2% is following, below the Cr:0.2%, therefrom select more than a kind or 2 kinds;

B group: Sn:0.02% is following, below the As:0.03%, therefrom select a kind or 2 kinds.

4, a kind of manufacture method of tube for crane chord member, it is characterized in that: for composition in quality %, specifically have: C:0.26～0.31, Si:0.17～0.35, Mn:1.30～1.50, Ti:0.01～0.04, B:0.0005～0.002, rest part is the material steel pipe of Fe and unavoidable impurities, its optimal heat treated state adds average tempering for quenching, its technology is: 900 ℃ of insulation 20min shrend of quenching, 470 ℃ of insulations of tempering 60min air cooling.

5, the manufacture method of tube for crane chord member as claimed in claim 4 is characterized in that: in quality % aforementioned composition is increased by 1 group or 2 groups that selects again from following A～B group, note

A group: Cu:0.2% is following, Ni:0.2% is following, below the Cr:0.2%, therefrom select more than a kind or 2 kinds;

B group: Sn:0.02% is following, below the As:0.03%, therefrom select a kind or 2 kinds.